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Application Time and Effectiveness of Four Systemic Nematicides Against Meloidogyne arenaria on Florunner Peanuts | Influence of Cropping Systems on Stem Rot (Sclerotium rolfsii), Meloidogyne arenaria, and the Nematode Antagonist Pasteuria penetrans in Peanut | s2orc_citation_titles | 31 |
Such a waste of money | They didn't fit my sons foot so I had to give them away. Such a waste of money! | amazon_reviews | 176 |
who commanded the japanese forces in the battle of wake island | Battle of Wake Island working anti-aircraft director among them); eighteen Browning heavy machine guns; and thirty heavy, medium and light water- and air-cooled machine guns. On 28 November, naval aviator Commander Winfield S. Cunningham, USN reported to Wake to assume overall command of U.S. forces on the island. He had 10 days to examine the defenses and assess his men before war broke out. On 8 December, just hours after the attack on Pearl Harbor (Wake being on the opposite side of the International Date Line), 36 Japanese Mitsubishi G3M3 medium bombers flown from bases on the Marshall Islands attacked Wake Island, destroying eight | paq | 285 |
who made the ford tvr griffith 400 | copies of the 400 and 10 600s off the assembly line at the Griffith factory in Plainview, Long Island, N.Y, USA, the company was dissolved. TVR Griffith 400 The TVR Griffith Series 400 is a 2-door coupe sports car produced by Griffith Motor Company in Plainview, New York ( a Ford Dealer in Plainview/Hicksville NY, Long Island ), between 1964 and 1967. It is the successor to the TVR Griffith 200, featuring improved cooling via a larger radiator with twin electric fans, redesigned rear suspension, and a redesigned rear with better visibility and the round taillights sourced from the Ford | paq | 435 |
Metric Regularity Relative to a Cone | The purpose of this paper is to discuss some of the highlights of the theory of metric regularity relative to a cone. For example, we establish a slope and some coderivative characterizations of this concept, as well as some stability results with respect to a Lipschitz perturbation. | s2orc_title_abstract | 106 |
which novel by robert graves was adapted for radio by robin brooks | I, Claudius (radio adaptation) I, Claudius is a six-part 2010 radio adaptation of the novels "I, Claudius" and "Claudius the God" by Robert Graves. Broadcast as part of the "Classic Serial" strand on BBC Radio 4, it was adapted by Robin Brooks and directed by Jonquil Panting, with music composed by David Pickvance. Claudius was played by Tom Goodman-Hill and the series' cast is also notable for including Derek Jacobi, who played Claudius in the 1976 BBC TV adaptation of the same works. The series was released as a BBC Audiobook on 6 January 2011. It won the 2012 Audie | paq | 97 |
I am sure he will love it as it is a heavy weight flannel | I got this shirt for my son for Christmas....I am sure he will love it as it is a heavy weight flannel. Well worth the price! | amazon_reviews | 158 |
what is the total number of residues in complement component 4 | Complement component 4 point in time, the genomic and derived amino acid sequence of either C4A or C4B had yet to be determined. The early studies vastly expanded the knowledge of the C4 complex, laying down the foundations that paved the way to discovering the gene and protein structures. C. Yu successfully determined the complete sequence of the human complement component C4A gene. In the findings, the whole genome was found to have of 41 exons, with a total of 1744 residues (despite avoiding the sequence of a large Intron 9). The C4 protein is synthesized into a single chain precursor, which then | paq | 392 |
What’s the status of God in philosophy? | Although most philosophers are atheists, is philosophy moving more toward the existence of God or against? The Kalam and Aquinas arguments are really good defense for the existence of god. However, does god most likely to exist according to philosophy? | reddit_title_body | 578 |
(E)-1-(2,4-Dichlorobenzylidene)thiosemicarbazide | In the crystal structure of the title compound, C8H7Cl2N3S, the Schiff base is approximately planar. An intramolecular N—H⋯S hydrogen bond stabilizes the molecular structure. The molecules are linked by N—H⋯S and N—H⋯Cl hydrogen bonds, forming a chain along the c axis. | s2orc_title_abstract | 22 |
Settlers Cafe on a Sunday afternoon | I was thinking of going over to Settlers Cafe this afternoon to play some boardgames with some strangers. I'm visiting from the US by myself and wanted to hang out, chat with the locals, and play some games. I'm just not sure if anyone will actually be at Settlers. Is anyone familiar with that Cafe? Or better yet, anyone want to join me? | reddit_title_body | 153 |
who lived in the hotel earle in the movie barton fink | Barton Fink home of Jack Lipnick. The spooky, inexplicably empty feel of the Hotel Earle was central to the Coens' conception of the film. "We wanted an art deco stylization", Joel explained in a 1991 interview, "and a place that was falling into ruin after having seen better days". Barton's room is sparsely furnished with two large windows facing another building. The Coens later described the hotel as a "ghost ship floating adrift, where you notice signs of the presence of other passengers, without ever laying eyes on any". In the film, residents' shoes are an indication of this unseen presence; another | paq | 400 |
educational math review toy | My 8yo twins received this for review and were actually excited to practice math with it during their summer vacation! It requires 2 AA batteries in a rear compartment that can be unscrewed with a coin. As stated in other reviews, the battery door bulges with the batteries inside although it does not affect the function. The screen is a very basic design typical of a calculator but with functions that allow testing in addition, subtraction, multiplication, division, decimals, fractions and percentiles. There are 9 levels for each function and a help button to provide clues. It's simple enough that my 6yo was able to figure it out and the green and red light next to the screen lets the player know if they have the correct answer. It's great for building math skills and since my kids are happy to play with it as an electronic toy I'm very happy | amazon_reviews | 255 |
[Rare Product Inquiry] JWH-073 (US/International) | Hi, I've been looking for some JWH-073 for a while now on a few markets to no avail, is is still around somewhere? Thank you | reddit_title_body | 248 |
They are so much more durable and I get WAY better traction! The chain coverage does have some gaps ... | I do snow removal in North Idaho in the winter, and I completely destroyed a pair of the cheap shoe chains that have the wire wound around the rubber. I'm on cross-slopes sometimes and making lots of turns with the snowblower, so the other pair would actually unwind itself from the rubber and then the loose wire would tear the rubber itself until there was so much broken rubber that I had to hold them together with zip ties. I decided enough was enough and bought these. They are so much more durable and I get WAY better traction! The chain coverage does have some gaps so sometimes if I step a certain way I slip a little, but there's enough grip that I always end up grabbing some kind of traction even if I slip a little bit initially. I use these over snow boots so the sizing was a concern, but they fit great and have kept me upright all season. We'll see how they hold up against the salt, but even if I have to buy a new pair every season, they're affordable enough that it's still a great buy. | amazon_reviews | 283 |
Finally, the guitar support I need | I tried many different guitar supports in an effort to lift the neck of my guitar high enough. Foot stools aggravated my back injuries, the Dynarette Cushion (which I used for two years) is comfortable but doesn't go high enough and is completely non-adjustable, and the A-Frame was a flimsy, unstable, and instant failure that I regretted purchasing almost immediately.
Enter the ErgoPlay....
I love this thing. It is very stable, comfortable, adjustable, and it can easily raise the guitar nearly a foot. The suction cups actually held on to my flat finish guitar, unlike my experience with the A-Frame Support which couldn't stick to anything. At first I wasn't really sure if I liked it but after a few days of playing with it I felt more and more comfortable with it. I eventually set it up so that it is extended almost to its full length and I don't think I'll ever be able to go back to using any other method.
My only complaint is that I wish it came with a small lint-free carrying bag because the suction cups tend to attract any felt, lint, pet hair, or dust nearby. This support will not fit in most guitar cases. | amazon_reviews | 35 |
ScienceDirect 12 th International Conference on Hydroinformatics , HIC 2016 Accuracy and computational efficiency of 2 D urban surface flood modelling based on cellular automata | JFLOW: a multiscale two-dimensional dynamic flood model | s2orc_citation_titles | 37 |
[USA-NY] [H] i7-2600, Alienware x51 mATX Motherboard, X51 R2 [W] Paypal, Google Wallet | I'm looking to sell my Alienware x51 R2, it makes a great living room steambox and can play most games at solid frame rates (~60-65 fps) that are not too GPU demanding (like Warframe, DOTA 2, TF2) but will struggle (~30-35 fps) if you're looking to play BF4 or Skyrim on Ultra or something like that. If you're looking to play Witcher 3 on something like this I would not recommend it because on Ultra it dips into 20 fps at certain points. But if you're looking for just a living room media center this thing has been great to me. Currently I'm using it as a Wii emulator with Dolphin and playing Project M I get 60 frames every time without any lag or stutters.
I'm looking to upgrade and don't have much need for it anymore so I'm going to try to get rid of it. It's literally in perfect condition so I'm going to ask 400 obo for it.
 
Timestamp
 
Earlier Stamp
 
I'll ship with everything but the Hard Drive, so 8GB DDR3 1600 Ram, the included GT 545 (with mount), i7-2600, stock fan cooler, external PSU, start up disk and manuals as well as the motherboard and power board.
 
If I don't get any interest I'd be willing to sell the i7-2600 separately either with the motherboard or without. I'd take 140 for the CPU and stock fan and 160 if you wanted the motherboard included. For the graphics card I would take like 40 for it if you're interested.
All prices include shipping. If you're interested just send me a PM, thank you!
 
If you just want the case and nothing else because it's cool we may be able to work that out as well, since I've seen people show a lot of interest in small form factor cases lately. | reddit_title_body | 104 |
Impact of Unstitched and Stitched Laminates by Line Loading | Results of impact responses for both unstitched and stitched laminates to line-loading at low striking velocities are presented in this paper. These laminates, made of E-glass dry preform and having a (0°2/90°2)s stacking sequence, were fabricated by resin transfer molding. For the stitched laminates, Kevlar-29 untwisted roving of 3000 denier was used for the through-the-thickness reinforcement. Impact tests were conducted on a specially designed falling tower with a line-nosed impactor. It was found that the number of matrix cracks, the splitting crack lengths, the delamination areas, and the laminate residual deflections were all much reduced due to the stitching reinforcement. The major impact-induced damage mechanism gradually changed from delamination for the unstitched laminates to the plastic-hinge type of localized deformation at the impact location for the stitched specimens as the stitching density increased. Further, delamination damage in an unstitched laminate could be detected from the recor... | s2orc_title_abstract | 148 |
who was hela the first human cell line | Stanley Michael Gartler identical, and further, all carried the G6PD allele found almost exclusively in people of African descent. HeLa, the first successfully established human cell line, was derived from a woman of African descent named Henrietta Lacks, so this result suggested that the cell lines were not truly independent, but had been contaminated by HeLa cells. It was not realized at the time that nearly all attempts to establish human cell cultures resulted in cell lines with limited life spans. Dr. George Gey, the originator of HeLa, had sent his cells to all who requested them, and this problem arose because many | paq | 263 |
Running Apps with Achievements | Hi guys,
I currently use Nike+ as a running app. Like many other users, I was pretty disappointed when they overhauled it, particularly because the ability to get achievements seems to have vanished. Maybe it's the gamer in me, but I liked getting an achievement for running on my birthday or being active 12 months in a row. They were motivating. Yes, you can still access them online, but I think they've been phased out of the mobile app (which was kinda the point, you know?).
Can anyone recommend an app that offers similar achievements? Or really, any achievements at all? Does such an app exist?
Thanks for your help. | reddit_title_body | 191 |
Water, Sewer, Trash in St. Louis City | Hi folks, I found a couple posts that were archived about paying water/sewer/trash in St. Louis City, but I still had a couple questions. We're thinking of renting a place that doesn't cover these utilities but are worried about how much it will cost. How much is the bill for a 2 bathroom house? How do you sign up for these utilities? | reddit_title_body | 466 |
Didn't work with my Pentax camera | Didn't work with my Pentax K-S2. The angle of the grip was such that there was no way you could get your hand in the right angle to release the shutter. Guess it just depends on your camera, but this didn't work for me. | amazon_reviews | 125 |
I thought this book was a textbook but it turns out that it looks more like a workbook that you write it in and I ... | I know this isn't a review but I have a question hopefully someone knows the answer. I thought this book was a textbook but it turns out that it looks more like a workbook that you write it in and I decided to rent it. Besides I rent it, I can't write in it. I'm not sure if I should keep it for now and wait what my teacher says or take it back and buy one instead. If someone could give me some opinions that would be awesome! | amazon_reviews | 78 |
Unrecorded watermark, colour shade and perforation variation in philatelic issues commemorating the World Youth Stamp Exhibition (2014) from Malaysia | A watermark is applied to an official paper document of value, such as postage and revenue stamps, bank notes and passports, as a device to reduce counterfeiting (Mackay, 2003). Typically, it comprises a pattern, image or letters that appear when viewed under transmitted light, or via reflected light on a dark background. Watermarks on postage stamps are often what differentiate a common stamp from a rare and valuable one, and recognition and study of watermarks is an active field of philately. Colour variation in stamps are more common and may be significant, especially in cases of missing colours. However, changelings (stamps that change colours due to condition of storage, etc) are of little philatelic value, and may be difficult to scientifically document (Guertin, 1965; Herendeen, 2013). Perforation types are also noteworthy, and recorded in detailed catalogues. As in watermarks, perforations can result in price differences between stamps, and fake perforations are common (Prill, 2011). | s2orc_title_abstract | 154 |
what type of sets can order theory be generalized to | does not have to be a lower set. Furthermore, it is often generalized to preordered sets. A subset which is - as a sub-poset - linearly ordered, is called a chain. The opposite notion, the antichain, is a subset that contains no two comparable elements; i.e. that is a discrete order. Although most mathematical areas "use" orders in one or the other way, there are also a few theories that have relationships which go far beyond mere application. Together with their major points of contact with order theory, some of these are to be presented below. As already mentioned, the | paq | 130 |
Tips for keeping a bird in a room. | Hello!
My fiance and I own a GCC and currently we are constrained to two places in a house (our bedroom and then a personal gaming/media room that's pretty big, Our birdcage is in the gaming room and we let the free roam this room since we are in it pretty much all day for work, gaming, tv etc. Our roommates own cats/dogs and we don't want our bird to be injured if it flies out the door when we are leaving to grab something. Anyone have a tip to have extra security in preventing the bird from flying out the room when the gaming room door opens? We don't want to put the bird in the cage every time we need to open the door for something.
​
Thanks! | reddit_title_body | 639 |
Stuck on 4.85 HFW after PS3Xploit | Hey all, I'm stuck on 4.85 HFW after using PS3Xploit. I'm trying to install 4.84.2 Rebug, but I'm unable to install any CFWs. I've tried the Rogero and Rebug 9.99 Downgraders as well as the 4.86.1 Rebug Lite, but they all come up with corrupt data (the MD5's all match) and I can't install any of them in recovery mode. I'm probably just dumb, but I'm brand new to PS3 Homebrew and honestly I'm not afraid to admit that I don't know what I'm doing (i'm more fluent in 3DS HB). Any help is appreciated, thanks!
EDIT: I updated to 4.87 and followed MrMario's guide instead and it worked well. Thanks to everyone who helped out! | reddit_title_body | 636 |
when was the last time ingonish had a high temperature | into the fall. These warm southwest winds blow down-slope from the Cape Breton Highlands, drying out and warming as it descends. Although the surrounding water freezes during winter, it warms very quickly through the summer, with sea surface temperatures peaking around 21°C (70°F) in August. The highest temperature ever recorded was on 10 August 2001. The lowest temperature was on 18 January 1982. Weather data has been recorded at Parks Canada in Ingonish Beach since 1950. In 2000, Environment Canada upgraded the climate station to an automated weather station. Ingonish Ingonish is a Canadian rural community in northeastern Victoria County, | paq | 366 |
TIFU by opening my pressure cooker | Obligatory not today, but a few months ago
So there I was cooking some meat in my pressure cooker on the stove. I had just turned off the stove to allow the steam to escape so it can de-pressurize. However, it was boiling so fast that it managed to build up sufficient pressure to activate the lock which keeps the intellectually challenged such as myself from opening it while it’s pressurized.
I wanted to check if they were done, but didn’t want to wait for for it to fully de-pressurize. I wanted my meat NOW. So I forced and twisted the top (which you’re not supposed to do) to open the lid.
Now I’ve done this before, even on the exact same settings when I was making dinner last week. There’s usually a little bit of pressure, just enough to activate the lock, so when you twist the lid off it will pop off a little bit that’s all.
This time, however, it didn’t just pop off. As soon as the lid was twisted enough to be lifted off, a deluge of boiling meat water and steam exploded out of the pot, covering the entire counter, stove, my phone, shirt, and pants.
I had to stand there in awe of the stupidity I have exhibited. The meaty juices was dripping onto the floor, behind the cabinet doors, on the walls, just fucking everywhere.
Luckily almost all of the meat stayed in the pot, so I cleaned everything up (the meat was done).
tl;dr: I opened my pressure cooker while it was under pressure and boiling meat juice exploded all over my kitchen. | reddit_title_body | 581 |
how soon should i take a pregnancy test? | hi! so i was supposed to get my period on june 17th but so far, my flo app is telling me i’m two days late [today is june 19th].
how soon after should i take a pregnancy test? a week after the 17th, which will be june 24th?
thank you & i’m sorry for the dumb question 😅 just a little freaked out.
edit: also i’m sure this is important but i just forgot to add, i had protected sex on june 12th! | reddit_title_body | 649 |
Six Steps to Overcome Bias in the Forecast Process | A technically sound forecast goes nowhere if it is not accepted by those in power, whether they are politicians or upper management. Elaine notes that often the forecast gets manipulated to satisfy political ends or meet targets and plans. Politics is also about biases, motivations, and interests, and comes into play when various incentives and reward structures influence the forecast. She maintains that we need to examine some common problems that organizations face and provide solutions that allow the technically sound forecast to prevail, free of manipulation or bias. She describes a case study in the politics of budget forecasting and offers six strategies to overcoming organizational politics. Copyright International Institute of Forecasters, 2005 | s2orc_title_abstract | 192 |
Hydrogen-Bonded Helical Self-Assembly of Sterically-Hindered Benzyl Alcohols: Rare Isostructurality and Synthon Equivalence Between Alcohols and Acids | Hydrogen-bonded aggregation has been examined in a series of sterically hindered benzyl alcohols with an objective to explore how sterics influence the otherwise inconsistent and variable synthons generally observed for alcohols. All the sterically hindered alcohols 8–15 were found to adopt a helical hydrogen-bonded synthon, and crystallize uniformly in the rare I41/a space group, for which the statistical prevalence in the CSD is abysmally small. Remarkably, the crystal packing in all of these alcohols is found to be isostructural to analogous sterically hindered carboxylic acids 1–4. The reason as to why all alcohols sustain the helical motif, despite being aggregated via rather weak hydrogen bonds as compared those in analogous acids 1–4 is traceable to unique molecular topology that permits close-packing as well as exploitation of intermolecular interactions comprehensively. It is shown that sterics permit a very rare packing as well as synthon equivalence between carboxylic acids and alcohols. It eme... | s2orc_title_abstract | 61 |
Shoes Christmas Gift for Smelly Feet? | Hey all!
Longtime lurker using a throwaway... (sorry!) My partner wants a nice pair of new shoes as a Christmas gift, and suggested I make it a present for both of us -- something that is comfortable and fashionable (for her), but will also make her feet extra smelly (for me). She's the best!
She likes flats, so I'm thinking a high end pair of "slipper flats" like Birdies Slippers or Rothy's Loafers that she can wear for comfort and fashion. Does anyone have experience with these, and know if they'll be a gift "for both of us" after some wear? Any other recommendations??
Thanks! | reddit_title_body | 481 |
who led the soviet union in the red inferno | Red Inferno: 1945 halting the Allied advance into Germany, new US President Harry S. Truman authorizes the US Army to continue across the Elbe and head for Berlin to bring a quick end to the war to guarantee the West's share of the to-be divided German capital with their forces in the city. However, Soviet Premier Joseph Stalin, despite the agreed terms of dividing Berlin and Germany with the Western Allies, wants to take Berlin for himself, on the grounds that the Soviet Union best deserved to conquer its archenemy's capital, after the unparalleled brutality of the Eastern Front. He even goes as | paq | 486 |
how many sangam verses are written by alathur kilar | Alathur Kilar Alathur Kilar, originally pronounced "Ālathur Kiḻhār" (Tamil: ஆலத்தூர் கிழார்), was a Tamil poet of Sangam period. He has authored seven poetries in the Sangam literature, including five in Purananuru and two in Kurunthogai. Alathur Kilar has written seven Sangam verses in all. This includes verses 34, 36, 69, 225, and 324 in Purananuru and verses 112 and 350 in Kurunthogai. The three Chola emperors mentioned by Alathur Kilar include Setchnni Nalankilli, Cholan Nalankilli, and Cholan Kulamuttratthu Thunjiya Killi Valavan. Alathur Kilar cites the Tirukkural in verse 34 of the Purananuru, calling it 'Aram' which later became one of | paq | 266 |
what was the charge in the cohoes fire | reported. There were minor injuries, including a firefighter who was taken to a hospital. Gomes pleaded guilty to arson and in June 2018 he was sentenced to one year in jail and a US$600,000 fine. 2017 Cohoes fire The 2017 Cohoes fire was a non-fatality fire that destroyed three residential buildings and affected 28 others in Cohoes, New York. Damage was estimated to millions of dollars. The fire started on November 30, 2017 when a local resident, John Gomes, attempted to imitate a metalworking technique he saw on the History Channel series "Forged in Fire". Flames from a burn-barrel he | paq | 207 |
Finding a pair of Oxfords - In Europe/Scandinavia | Hey MFA
I'm searching for a pair of Oxfords, as my previous shoes are no more.
So far I got my eyes on the Walk-over George (dark brown), the thing they don't seem to have any seller(s) based in my country - Denmark - or Scandinavia and I'd definitely prefer if I could find a store to actually try the shoes before I buy.
I plan to ask a local store if they'd able to get their hands on a pair, but should that fail I would like to have a backup plan!
Church's has a store in Copenhagen but I think their price point is a bit higher than what I'm aiming for. F.x. the Maltby from the contemporary collection sits at 650 € while the Walk-over pair is 345 $.
Thanks in advance for your guidance. | reddit_title_body | 101 |
Polaroid Type 80 viva film | Polaroid viva film is the best alternative to most Type 80 Polaroid film.
Being that there is no alternative other, Polaroid viva, is the choice film for my Holgaroid (Polga), Polaroid Square Shooter 2, and my current Polaroid Type 100 back modified, allowing the usage of Polarod viva in the same Polaroid back that processes all of my Type 100 films - like polaroid Type 665, 669 and 690.
Lately, I allow the film to dry completely before scanning.
Polaroid, we see you now! | amazon_reviews | 237 |
Recommendations for screen recording 3D models | I am using a PC laptop, and I can make very basic screen recording of my full res scans using the xbox app. I use reality capture, and their video option is for fly throughs I think intended for drone projects only.
I would like a nice, slow rotating view of a model recorded to video format, rather tha the jerky rotation and view used with just a cursor. Anyone know of any programs that you can use for more polished screen recording of 3D models? | reddit_title_body | 493 |
Directional characteristics of electrodiffusion anemometric triple-split probes | Abstract The theory of steady convective diffusion to a circular cylinder in cross flow shows that the directional characteristics of triple-split anemometric probes depend strongly on Re due to the changing wake structure in the range of medium Re. Resulting predictions of the directional characteristics agree well with the data for a real electrodiffusion three-segment anemometric probe. | s2orc_title_abstract | 81 |
Phosphorylation by tyrosine kinases has been shown to promote cellular growth and hypertrophy and to play a key role in modulating ion channels. We have examined possible effects of genistein, a protein tyrosine kinase (PTK) inhibitor, on cardiac delayed-rectifier K currents (IK). Guinea pig ventricular myocytes were voltage-clamped by conventional whole-cell mode (5.4 mM [K]out/150 mM [K]in; pCa = 8; 36 degrees C). Amplitudes of tail and steady-state (2-s pulse) currents were measured as IK. Micromolar concentrations of genistein (10-100 microM) reversibly inhibited basal, swelling-enhanced (by 70% hypotonic solution), and intrapipette Cyclic adenosine monophosphate (cAMP) (1 mM)-enhanced IK concentration-dependently, while intrapipette cAMP-enhanced IK were also affected by daidzein, an inactive analog of genistein. In contrast, lavendustin A (10 microM) and tyrphostin 51 (100 microM), other types of PTK inhibitors, had no effect on IK. These results suggest that genistein may inhibit IK and that this inhibition is not mediated by an inhibition of tyrosine kinase activity. | It has been suggested that protein tyrosine kinase (PTK) activity can directly regulate cardiac L-type Ca(2+) channels. This conclusion is based to a large extent on the observation that the PTK inhibitor genistein can inhibit the cardiac L-type Ca(2+) current. The purpose of the present study was to determine whether the ability of genistein to inhibit cardiac L-type Ca(2+) channel activity is due to inhibition of PTK activity. Genistein significantly reduced the magnitude of the L-type Ca(2+) current in guinea pig ventricular myocytes recorded using the whole-cell patch-clamp technique. However, this effect was associated with extracellular, not intracellular, application of the drug. Peroxovanadate (PVN), a potent protein tyrosine phosphatase inhibitor, had no effect on the basal Ca(2+) current. PVN was also ineffective in preventing the inhibitory effect of genistein. Internal perfusion of cells with a pipette solution containing ATPgammaS was used to prevent reversibility of phosphorylation-dependent processes. This treatment did not alter the inhibitory effect of genistein, although it did result in irreversible protein kinase A-dependent regulation of the Ca(2+) current. Bath application of lavendustin A, a PTK inhibitor that is structurally unrelated to genistein, did not affect the Ca(2+) current amplitude. The inhibitory effect of genistein was also associated with a hyperpolarizing shift in the voltage dependence of Ca(2+) channel inactivation. These results are consistent with the conclusion that the cardiac L-type Ca(2+) current is not directly regulated by PTK activity and that the inhibitory effect of genistein is due to direct non-catalytic blockade of the channels. | s2orc_abstract_citation | 54 |
Tavern Brawl idea: train an AI | We all figured the Burndown brawl was collecting AI training data. Wouldn't it be cool to see your PvE opponent go from 0% to 50+% win rate as the week goes on?
Depending on how the team does it, you could train a deckbuilding or gameplay AI, or both.
Imagine: the AI can see your deck before the game and build something in response. On Wednesday it throws in random cards and makes random moves. You win easily. By Friday it can spot your aggro/midrange/control build and tech for it. By the end of the brawl it's solved the meta and we only win with obscure combos and RNG. | reddit_title_body | 405 |
how many days of measurable precipitation does wichita get | Wichita, Kansas exceeds an average of 62 days a year and an average of 12 days a year. The minimum temperature falls to or below on an average 8.5 days a year. The hottest temperature recorded in Wichita was in 1936; the coldest temperature recorded was on February 12, 1899. Readings as low as and as high as occurred as recently as February 10, 2011 and July 29–30, 2012, respectively. During an average year, Wichita receives of precipitation, most of which falls in the warmer months, and experiences 88 days of measurable precipitation. The average relative humidity is 80% in the morning | paq | 35 |
glad I know how to sew | String and button came off after a few times wearing these boots, glad I know how to sew. Great boots for the price though. | amazon_reviews | 375 |
great for photo props | great sticks for crafts. made photo props, worked great. | amazon_reviews | 289 |
The greatest crime I have ever read | The greatest crime I have ever read! The story-twist about half way in the novel is mind blowing.
Even the last sentence is a cliffhanger!
Great read! | amazon_reviews | 303 |
HIGH QUALITY FINISHING OF BEVEL GEARS BY ELECTROCHEMICAL HONING | Investigations on surface quality improvement of straight bevel gears by electrochemical honing process | s2orc_citation_titles | 30 |
name the type of laser used to heat crystalline silicon | Crystalline silicon is the use of a laser to heat the silicon locally without heating the underlying substrate beyond some upper temperature limit. An excimer laser or, alternatively, green lasers such as a frequency-doubled Nd:YAG laser is used to heat the amorphous silicon, supplying energy necessary to nucleate grain growth. The laser fluence must be carefully controlled in order to induce crystallization without causing widespread melting. Crystallization of the film occurs as a very small portion of the silicon film is melted and allowed to cool. Ideally, the laser should melt the silicon film through its entire thickness, but not damage the | paq | 28 |
Very disappointed for the price | Is no where near as bright as it is let on to be. Very disappointed for the price. I've had better for less. | amazon_reviews | 61 |
who was the author of the book 173 hours in captivity | 173 Hours in Captivity 173 Hours In Captivity: The Hijacking of IC 814 is a 2000 book () written by Neelesh Misra, a New Delhi-based correspondent of the "Associated Press". The book is about the hijacking of Indian Airlines Flight 814 on its journey from Kathmandu to New Delhi on Christmas Eve, December 24, 1999. The sequence of events outside the plane (IC 814) is a well-documented and familiar story. The book presents the events inside the plane. During their 173 hours of captivity, the passengers and the crew lived and re-lived, experienced and re-experienced many uncomfortable emotions. The book | paq | 282 |
Nice Nautical Addition to Steampunk World | Really like this Steampunk series. The lost world of oracles is a nice addition to the nautical arena of Steampunk. Nicely developed characters. Each book has a new couple to focus on. Wanted to get a sense of what steampunk is, and I am getting that from these novellas. Good read. | amazon_reviews | 227 |
who plays jessie in gerald's game | Gerald's Game having been abandoned, was shot and killed by the police. In May 2014, "Deadline Hollywood" reported that Mike Flanagan was set to direct a film adaptation. In an interview with Rue Morgue in September 2016, Mike Flanagan said that the film adaptation would premiere on Netflix. He did not state when the film would premiere or whether Stephen King would be involved. In October 2016, Deadline reported that Carla Gugino and Bruce Greenwood will star in the film as Jessie and Gerald Burlingame. On October 17, 2016, Flanagan tweeted indicating the first day of production had begun. The film premiered | paq | 438 |
Should I visit my abusive dying grandmother? | On mobile and English isn't my first language.
also a first time poster.
Tldr:
Abusive grandmother is dying, should I go visit her and my grandfather that I blame for my father slight abusiveness?
Storytime!
My father was severely abused his entire childhood. I (24f) know that my grandfather even broke my father's arm and at some point my father ran from home and moved in with my mother's parents.
Many years and many events later, they apologized to my father and my father forgave them, as I was told.
But my father in turn became an abusive man. Though not nearly as bad as my grandparents and I think in many of the FEW instances he exploded, my mom took the hit. The only instances I remember were when he hit my brother who than had a bloody nose. Him pushing me to the ground and kicking me (not sure if this actually happened or that my young brain made this up for some reason...) Him throwing water at me and than the glass as well (he threw the glass towards my stomach, not my head)
For some reasons I don't have many memories of my childhood, either good or bad. What I do remember is being scared of my father, wishing other dad's were actually my dad and thinking if my dad were to die in an accident, I'd be sad, but my life would be better for it. I also cried when my mom left for work and I remember never wanting to move out because I didn't want my mom to be alone with him, listening in to them fighting in case I had to jump in and my mom having an escape plan ready. Keep in mind that I was a child when these thoughts processes happened.
My relationship with my dad is complicated, but I'm on good terms with him right now. However, I haven't seen his parents in years, though I accepted their call on my birthday. I mostly blame them for how my father has treated us. My grandmother had a sister, who is the complete opposite of her, why couldn't she be like her sister? Why did she abuse her children together with her husband? I don't hate her, but I do blame her.
To my actual problem: grandmother is dying and my father asked me if I wanted to go visit her. I don't know if I should or shouldn't go and I would like some advice to what others would do. Should I just suck my issues up and go? I'm young (24f), I'm not the wisest. Will I regret going? What would I even talk about with them if I went? Will I regret not going? If I don't go, would that hurt my dad? How should I even bring it if I don't go. | reddit_title_body | 516 |
Purposefully getting a Master's degree in a seperate major? | I'm currently pursuing an undergraduate degree in Mechanical Engineering with plans to go back to school for Master's after I graduate. But the thing is that I'm highly interested in both Mechanical and Electrical and was considering getting a Master's in that instead of Mechanical. Is there anything particularly wrong with this idea? | reddit_title_body | 245 |
Live oak saplings survive prescribed fire and sprout | Prescribed Fire Effects on Deciduous Oak Woodland Stand Structure, Northern Diablo Range, California | s2orc_citation_titles | 52 |
what surrounded the big bang singularity before it banged? | What was around the singularity concurrent to it being a singularity and did that singularity emit or did it suck. And, can such a singularity exist in our current universe waiting to bang | yahoo_title_question | 1 |
In vivo and ex vivo needle-based confocal endomicroscopy of intraductal papillary mucinous neoplasm of the pancreas. | Validation of diagnostic characteristics of needle based confocal laser endomicroscopy in differentiation of pancreatic cystic lesions | s2orc_citation_titles | 37 |
Actually better than my old one | It worked well for what I needed it for. Actually better than my old one. | amazon_reviews | 252 |
Proteomic analysis of changes in pea roots caused by the apoptosis-inducing concentration of salicylic acid | Effects of salicylic acid on protein content and 14C-amino acid incorporation into proteins of pea roots | s2orc_citation_titles | 28 |
worked great for a while (5 months) | worked great for a while (5 months)...now the transmitter is shutting off by itself...I have to go over and toggle the on/off switch to get it to turn back on...after 10 minutes it will just shut off again...I replaced the batteries in both the receiver and the headphones and the problem persisted | amazon_reviews | 133 |
where does the old bering sea start and end | Old Bering Sea Old Bering Sea is an archaeological culture associated with a distinctive, elaborate circle and dot aesthetic style and is centered on the Bering Strait region; no site is more than 1 km from the ocean. Old Bering Sea is considered, following Henry B. Collins, the initial phase of the Northern Maritime tradition. Despite its name, several OBS sites lie on the Chukchi Sea. The temporal range of the culture is from 400 BCE to possibly as late as AD 1300. The culture was initially named the "Bering Sea" culture by Canadian archaeologist Diamond Jenness in 1928 following | paq | 141 |
What was the significance of the Treaty of Paris in 1763? | What did the treaty of paris in 1763 result in? | wikianswers | 22 |
what type of acting is available in the play the weavers | The Weavers (play) characters are proletarians struggling for their rights. Unlike most plays of any period, as pointed out many times in literary criticism and introductions, the play has no true central character, providing ample opportunities for ensemble acting. Barrett H. Clark's comments: "as one of Gerhart Hauptmann's experiments in dramatic form, "The Weavers" is highly significant. Instead of a hero, he has created a mob; this mob is, therefore, the protagonist—or chief character—and if individuals emerge from the rank and file they are not thrust into the foreground to stay long. It is the weavers as a class that is ever before | paq | 474 |
Context, Not Conflict, Drives Cognitive Control. | Theories of cognitive control generally assume that perceived conflict acts as a signal to engage inhibitory mechanisms that suppress subsequent conflicting information. Crucially, an absence of conflict is not regarded as being a relevant signal for cognitive control. Using a cueing, a priming, and a Simon task, we provide evidence that conflict does not have this unique signal status: Encountering a conflict does not lead to behavioral adjustments on subsequent conflict trials, whereas encountering a nonconflict trial does lead to behavioral adjustments on subsequent nonconflict trials. We propose that this apparent role-reversal can be explained by a mechanism that responds to both the presence and the absence of conflict, down-regulating the visuomotor system following conflict, and up-regulating it following nonconflict. (PsycINFO Database Record (c) 2011 APA, all rights reserved). Language: en | s2orc_title_abstract | 90 |
Good router- no issues. Strong signal and easy set-up | Easy set-up, solid signal. No issues other than downloaded and installed the EU firmware update from the website by mistake as they're kinda thrown in together (should be more clearly identified as US customers should probably not be given the option as a top choice)- still works perfectly. | amazon_reviews | 309 |
when did harsh vardhan become the chief minister of delhi | having made the statement. Harsh Vardhan is married to Nutan, and they have two sons and a daughter. Harsh Vardhan (Delhi politician) Dr. Harsh Vardhan is the incumbent minister at Ministry of Science & Technology (India), Ministry of Environment, Forest and Climate Change and Ministry of Earth Sciences in the BJP-led NDA government of Prime Minister Narendra Modi. He represents Chandni Chowk in Delhi as a Member of Parliament in the 16th Lok Sabha. He was also the Chief Minister of Delhi candidate for the BJP in the 2013 Delhi assembly election. Harsh Vardhan was born in Delhi to Om | paq | 189 |
'My Cancer' Blog Marks First Birthday | It's hard to believe, but at the end of this month, the blog will be one year old. As I sit here now, it feels like this past year has flown by. But time heals a lot of things. Memories start to fade. It's possible to forget those hours in the chemo chair that felt like days, the days of feeling sick that seemed like weeks. I realize that I have changed. A lot. My thinking about cancer is different. Cancer has lost some of its terror. I remember how panicked I was the first time I was told that there were tumors in my body. I wanted them out, that minute. Now, if the next scans find something, I'll be disappointed, but I won't panic. I know that there is time, that there are ways to attack them. I went back and read the first blog entry. It was about denial, something that I think all cancer patients are familiar with. I found this passage: I know it's in there. I know that, most likely, it will kill me. But that doesn't stop me from dreaming. I still think about things I'd like to be doing in ten years, five years, next year. Well, now it is "next year." It wasn't all that certain that I would still be here for the end of the first year, but here I am. Have I done those things I was dreaming about the first time I sat down to write a blog? Honestly, I don't remember what those dreams were. I do think about the future, every day. I don't know if any of those dreams will turn into reality, I don't know if I'll get the time. But I made it this far. And sitting here, right now, that feels like a victory. | npr | 2 |
Getting ready to sell home in Central Texas. Should I replace master bedroom carpeting with wood flooring? | My house is 5 years old and has ceramic tile in living areas, carpeting in bedrooms. The master bedroom carpeting shows wear. I'm trying to decide if I should just re-carpet or invest in wood flooring. Any thoughts? | reddit_title_body | 324 |
when did white water world open at ocean parade | Ocean Parade (Dreamworld) all of the area once occupied by Country Fair. Since its opening, the most major change to the land was when The Claw was added in September 2004. This installation required the redesign of the pathway, dining and merchandise shops. In 2006, Ocean Parade opened a "park-hop" entrance to WhiteWater World, which is also owned by Ardent Leisure (the owners of Dreamworld). In June 2011, Dreamworld will open a Zamperla Disk'O called "Shockwave". In 2014, Dreamworld renovated Ocean Parade with the rebuild of Wipeout and the opening of Tail Spin. In 2015, The Cyclone was renovated and transformed into Hot | paq | 535 |
Great 2D pictures, easy to use. | Great pictures and easy to use. Love having an extra battery! The 3D picture mode isn't all that great, but we didn't get it for that. | amazon_reviews | 233 |
Multiaxial Stress Relaxation of Dual-Cross-Link Poly(vinyl alcohol) Hydrogels | Dual-cross-link hydrogels, which are composed of poly(vinyl alcohol) chains cross-linked by covalent bonds and transient physical bonds via borate ions, have received considerable interest due to the high extensibility as well as the self-healing properties. The dual-cross-link gels exhibit pronounced stress relaxation after the imposition of step strain, reflecting the breaking dynamics of temporary chains which sustain the initial stress. Multiaxial stress relaxation experiments using equibiaxial, planar, and uniaxial stretching with various degrees of strain unambiguously validate the time-strain separability in relaxation stress for a general type of deformation. The time effect is satisfactorily described by an existing model, while the strain effect is well approximated by the neo-Hookean model. Furthermore, the magnitude of total stress relaxation to the initial stress is constant, independently of the type and degree of imposed strain. These simple features provide an important basis for formulati... | s2orc_title_abstract | 155 |
[Podcast] Why you don't want to start with Starting Strength or Stronglifts - Revive Stronger: 150 | Podcast
>This time we're talking about the times of uncertainty and mostly why starting strength or stronglifts are not good programmes for hypertrophy!
**Timestamps:**
00:20 We're talking about our current state
33:44 Starting strength, 5x5
42:52?
54:32 Best tips for leg training @ home? In having a really tough time stimulating them. | reddit_title_body | 491 |
Edward J. Hendrick | Edward Joseph Hendrick (March 23, 1910 - August 12, 1987) was a leader in American prison systems and public administration. From 1952 to 1972, he was Deputy Commissioner of Public Welfare for the City of Philadelphia, and simultaneously served as Superintendent of the Philadelphia Prison System. By virtue of office, he was the lead named defendant in Jackson v. Hendrick, which set important legal precedents regarding humane conditions and overcrowding in US prisons. He was previously Chief Probation Officer for the United States District Court for the Eastern District of Pennsylvania. During World War II, he served in the US Navy as prison administrator for the 12th Naval District based in San Francisco, California.
His career was bookended by service in the Catholic Church. As a young man he entered the Jesuit formation and taught Latin at Regis High School in New York City. After retiring from government service, he became one of the most senior laypeople in the Archdiocese of Philadelphia, leading Adult Social Services - including the management of various nursing homes and shelters, and related programs. He was made a Knight of St. Gregory the Great by Pope John Paul II.
Early life
Edward was the first child born to Foscola Orrimela (F.O.) Hendrick and his second wife Helen C. Hendrick (née O'Neil). Foscola was an inventor and restaurateur, serving as general manager of Childs Restaurants, which was owned by his mother's family. Foscola's first wife, Frederikke Marie Blix, had died in 1902, leaving Foscola with four children. Foscola subsequently met and married Helen C. O'Neil, who had been a cashier in one of the Childs restaurants. In addition to Edward, Foscola and Helen had three further children: Helen, Catherine, and James.
As a boy, Edward attended Xavier High School in New York City, and then proceeded into the Jesuit formation, attending Woodstock College and Georgetown University.
Career
In 1940, Hendrick was appointed US Probation Officer for the District of New Jersey, by the Honorable Guy Leverne Fake; the appointment was confirmed by US Attorney General Robert H. Jackson. In 1943, Hendrick accepted a transfer to the Eastern District of Pennsylvania, reporting to Randolph E. Wise, Chief US Probation Officer. When Wise resigned, Hendrick was appointed to succeed him. Wise and Hendrick formed a professional relationship that would span another 40 years, through the City of Philadelphia (1952–1972) and the Archdiocese of Philadelphia (1973–1984), when both men retired.
In July 1944, Hendrick was granted a leave of absence from his federal role, in order to join the US Navy in support of World War II. During the war, he ran several Navy prisons in the Western US.
In 1952, Wise was appointed Philadelphia's first Commissioner of Public Welfare. Wise named Hendrick as one of his three Deputy Commissioners, with a specific focus on the city's penal system. They were part of a wave of reformers coming in under Joseph Clark, who was the city's first Democratic mayor in 68 years. Wise and Hendrick would continue in their respective roles through the next 20 years under Mayors Clark, Dilworth, and Tate.
Hendrick was recognized as a progressive and vocal advocate of prison reform efforts – mounting campaigns to end prison overcrowding, to improve staffing and training levels, and to offer inmates rehabilitation and vocational programs.
As early as 1957, Hendrick gave an interview to The Philadelphia Inquirer where he called attention to the issue of overcrowding and under-staffing in his own prison system, lobbying for the construction of a new facility "to replace the overcrowded, outdated Moyamensing Prison".
Nevertheless, the Philadelphia prison population exploded during his tenure, the city did not provide adequate funding to expand capacity or programs, and the system began to crack. On July 4, 1970, inmates at Holmesburg Prison rioted. In February 1971, five inmates filed a class action (Jackson v. Hendrick), "seeking injunctive relief from conditions of confinement alleged to violate the prisoners' constitutional and statutory rights". Over 15 years the case worked its way through the legal system, ultimately to the Pennsylvania Supreme Court.
In 1972, a frustrated Hendrick surprised new Mayor Frank Rizzo by resigning his City post and joining the Archdiocese of Philadelphia, to help lead the Catholic Social Services Administration. The move should not have been a great surprise, as his friend and boss Randolph Wise had also left the City and joined the Archdiocese, just months prior.
In 1984 at the age of 74, Hendrick retired from the Archdiocese. In 1986, Pope John Paul II made him a Knight of St. Gregory; he was invested by Cardinal John Krol. He died at his home in Philadelphia on August 12, 1987.
References
Knights of St. Gregory the Great
1910 births
1987 deaths
Woodstock College alumni
Georgetown University alumni
Xavier High School (New York City) alumni
People from East Orange, New Jersey | wikipedia | 45 |
USB Port not compatible with iPhone or iPod | The USB drive is not compatible with either the iPhone or the iPod. This was a huge disappointment. It appears that is is meant for connecting only to a thumb drive. Lame... | amazon_reviews | 166 |
Sputtered Pd77%Ag23% membranes of thickness 2.2-8.5 µm were subjected to a three-step heat treatment in air (HTA) to investigate the relation between thickness and the reported beneficial effects of HTA on hydrogen transport. The permeability experiments were complimented by volumetric hydrogen sorption measurements and atomic force microscopy (AFM) imaging in order to relate the observed effects to changes in hydrogen solubility and/or structure. The results show that the HTA-essentially an oxidation-reduction cycle-mainly affects the thinner membranes, with the hydrogen flux increasing stepwise upon HTA of each membrane side. The hydrogen solubility is found to remain constant upon HTA, and the change must therefore be attributed to improved transport kinetics. The HTA procedure appears to shift the transition from the surface to bulk-limited transport to lower thickness, roughly from~5 to ≤2.2 µm under the conditions applied here. Although the surface topography results indicate that HTA influences the surface roughness and increases the effective membrane surface area, this cannot be the sole explanation for the observed hydrogen flux increase. This is because considerable surface roughening occurs during hydrogen permeation (no HTA) as well, but not accompanied by the same hydrogen flux enhancement. The latter effect is particularly pronounced for thinner membranes, implying that the structural changes may be dependent on the magnitude of the hydrogen flux. |
Introduction
Palladium-based membranes have been the focus of many studies due to their high hydrogen permeability and selectivity, which may find application in efficient separation technologies [1,2]. At temperature below~300 • C and pressure below~2 MPa, however, pure palladium undergoes the α-to-β phase transition that results in irreversible lattice strain. Over time, cycling of the temperature causes the Pd to become brittle; leading to fractures. In order to prevent hydrogen embrittlement, Pd is conveniently alloyed with other metals [3,4]. Silver is a widely used alloying element, reducing the α-to-β phase transition to below room temperature. Moreover, Pd-Ag alloys exhibit higher hydrogen permeability than pure palladium [4][5][6], with a maximum at~23 wt.% of Ag [6].
Hydrogen flux can be also enhanced by heat treatment in air (HTA) procedures [7][8][9][10][11][12][13][14][15][16][17][18][19], which are essentially oxidation-reduction cycles. For thin membranes, typically in the range of 1-3 µm, the total hydrogen flux through the membrane can be doubled upon air thermal treatment [8][9][10][11]16], and HTA has also been used to regenerate deactivated membranes [14,20,21]. Moreover, Mejdell et al. reported a significant reduction of the CO inhibitive effects on hydrogen permeation through a~3 µm Pd-Ag (23%) membrane after HTA [9]. The phenomena behind these advantageous effects are, however, still not clear. Different hypotheses have been suggested to explain the influence of heat treatment in air; including cleaning of the Pd-Ag surface, microstructural rearrangement, and induced segregation of Pd towards the surface. Oxidation is known to remove certain impurities and poisoning species from Pd-based surfaces [5,15,16,20]. This can facilitate and improve hydrogen flux, but is not a sufficient explanation that can fully elucidate the positive effects of HTA [14].
Microstructural changes are commonly observed in Pd-based membranes after air exposure, while the permeation properties are maintained or enhanced and even the stability/durability seems upheld. These include increase in surface roughness [10,13,14,17,22,23], as well as defect/void formation [8,11,14,17,19]. The increased surface roughness leads to an enlarged active surface area which can promote the hydrogen flux through the membrane given that surface phenomena are transport limiting. Furthermore, surface roughening is associated with grain growth in the membrane bulk [10,13,14,17,19]. As there is no clear agreement on whether larger grains inhibit [24][25][26] or enhance [27,28] hydrogen flux, it is not possible to irrefutably attribute hydrogen flux enhancement to formation of larger grains. Recently we established, however, a possible correlation between the solubility of hydrogen and the average grain boundary density in sputtered membranes, rendering the diffusivity practically unaffected as long as the hydrogen transport was controlled by bulk diffusion [29]. On the other hand, Zhang and co-workers [17] reported an increase in the hydrogen sorption kinetics that was attributed to higher hydrogen diffusivity for a 25 µm cold-rolled Pd-Ag 25 wt.% membrane after heat treatment in air at 300 • C for 1 day.
Another hypothesis is related to surface segregation of Pd as a result of the heat treatment in air, since H 2 dissociates over and binds to Pd but not to Ag. It is well established that Ag segregates to the membrane surface of ideal Pd-Ag alloys in absence of adsorbates; i.e., under vacuum or inert gas conditions, while a reverse segregation of Pd is induced after exposure of Pd-Ag surfaces to hydrogen and several other chemisorbing species [30][31][32]. The thermal treatment in air has been found to yield formation of a~2 nm thick PdO layer [13] on the Pd-Ag surface and to an enrichment of Pd that can be involved in the enhancement of hydrogen flux through Pd-Ag membranes [13,15,16,32]. Segregation and rearrangement of the outmost atomic layers could also be linked, in the sense that this could affect in particular the transfer of hydrogen from the surface to the bulk or vice versa; processes that are particularly difficult to study experimentally.
In this work, a new approach to the heat treatment in air procedure has been applied in order to further investigate its effect on hydrogen transport properties in Pd-Ag membranes. The procedure was performed so that each side of the membranes was consecutively exposed to ambient air in order to probe the individual surface responses, which to our knowledge have not been previously addressed in the literature. A final HTA applied to both sides together was also performed in order to establish if additional effects exist. Different membrane thicknesses have been included to the investigation, as well as measurements of hydrogen solubility before and after heat treatment, to better understand the transport mechanisms involved. The membranes were characterized using atomic force microscopy (AFM) for as-grown membranes, hydrogen-stabilized, and heat-treated in air (with subsequent hydrogen stabilization), to monitor changes in surface topography.
Materials and Methods
Membrane Preparation
Pd77%Ag23% thin, self-supported membranes were produced by SINTEF using a unique two-step magneton sputtering technique onto silicon single crystal substrates [33,34]. Pd-Ag films with thicknesses of 2.2, 4.7, 6.9, 8.5, and 11.2 µm were studied. The membrane thickness was determined using white light interferometry. In this work, the membranes analyzed have been categorized as follows: 'as-grown' refers to Pd77%Ag23% thin film samples just pulled-off from the silicon substrate; 'hydrogen-stabilized' refers to membranes exposed to hydrogen permeation measurements only; 'air-treated' corresponds to membranes that have been heat-treated in air (HTA) and subsequently stabilized under hydrogen according to the procedures described below. The 'growth/feed side' of the membranes is the side growing during the magneton sputtering deposition and was always exposed to the feed gas during permeation experiments. The 'substrate/permeate side' refers to the membrane side facing the silicon wafer under fabrication, and was always kept to the permeate (low pressure) side of the membranes during permeation experiments.
Hydrogen Stabilization/Permeation
The permeation behavior under pure hydrogen (purity 99.999%) through the Pd77%Ag23% membranes was studied as a function of temperature and pressure with no use of sweep gas. All membranes were mounted in a microchannel configuration as depicted in Figure 1. The membranes were placed in between a polished stainless steel feed housing and a polished stainless steel plate. The feed housing had seven channels for gas flow corresponding to a total active surface area of 0.91 cm 2 , in accordance with the permeate side steel plate geometry. On the permeate side, an open stainless steel housing was sealed to the perforated steel plate by a polished copper gasket. In conjunction with absence of sweep gas or dilutants, this configuration enables investigation of very thin membranes in absence of transport limitations from the gas phase (concentration polarization) or the support [35]. Membrane leakage was checked by using an Agilent 490 Micro-GC (Agilent Technologies, Santa Clara, CA, USA). No leakage could be detected during any of the permeation experiments both before and after the three-step heat treatment procedure. Experiments were performed at selected temperatures of 300, 350, and 400 • C. 300 • C was reached by ramping at 2 • C per minute with nitrogen (purity 99.999%) flushing on the feed side and argon (purity 99.999%) on the permeate side. After reaching 300 • C, nitrogen and argon were slowly removed from the system and hydrogen introduced. The permeate side was left at atmospheric pressure while a differential pressure of maximum 2 bar was applied on the retentate side. The permeate flow was measured by a bubble flow meter.
Heat Treatment in Air (HTA)
The three-step heat treatment in air (HTA) procedure was performed between hydrogen permeation experiments for three selected membrane thicknesses; 2.2, 4.7, and 8.5 µm respectively. The HTA was mainly performed using the following sequence: (i) permeate side, (ii) feed side, (iii) both sides one more time, with hydrogen permeation experiments between each step. Each HTA step was carried out at 300 • C for one hour. Before exposing the membranes to ambient air, hydrogen was removed from the system by introducing nitrogen on the feed side and argon on the permeate side for about 15 min. Nitrogen/argon were reintroduced for 15 min at the feed/permeate sides in order to flush out air. Hydrogen was then introduced again and nitrogen/argon slowly removed. As will be shown, HTA had the largest effect for the thinnest membranes. Another 2.2 µm membrane was therefore subjected to an alternative HTA sequence, denoted HTA2: (i) feed side, (ii) permeate side, (iii) both sides one more time, again with hydrogen permeation experiments between each step and procedures otherwise as described above.
Hydrogen Solubility
Equilibrium sorption measurements were carried out as described in [29] using an ASAP 2020 chemisorption analyzer (Micromeritics Instrument Corporation, Norcross, GA, USA) for 2.2 µm and 8.5 µm as-grown membranes, as well as after heat treatment in air. The heat treatment in air for the sorption samples was performed in a furnace at 300 • C under ambient air for one hour. Volumetric sorption was performed with a hydrogen pressure between 0.02 and 90.7 kPa. In every measurement, a sample mass close to 0.1 grams was used, taking into account also mass loss from degassing of the sample. The sorption measurements were carried out twice at three different temperatures: 300, 350, and 400 • C.
AFM Imaging
The surface topography was investigated by atomic force microscopy (AFM, Bruker, Boston, MA, USA) using a Multimode AFM instrument with a Veeco Multimode controller. All force spectroscopy analysis was performed in tapping mode under atmospheric conditions. Surface topography was investigated for both growth/feed side and substrate/permeate side for all the as-grown membranes, for hydrogen stabilized membranes and selected membranes after heat treatment in air with subsequent hydrogen stabilization. At least five surface scans were obtained at different locations for each sample. The first flattening order, provided by the AFM-instrument software (Nanoscope Software Version 7.2, by Veeco, Plainview, NY, USA), was performed in order to remove tilt and noise from all images. Surface roughness was estimated as the root mean square roughness (Rq) from the measured AFM images.
Results and Discussion
Permeability
Hydrogen permeation through Pd-Ag membranes generally follows the solution-diffusion mechanism, where Fick's law of diffusion describes the mass transport
J H 2 = P t (p n 1 − p n 2 ) = SD t (p n 1 − p n 2 )(1)
P is the permeability of the membrane, t the thickness, p 1 and p 2 the partial pressure of hydrogen on the high pressure side and low pressure side of the membrane, respectively, S the solubility, and D the diffusion coefficient. The n-value is determined by the rate-limiting step of the transport mechanism as explain further below. The diffusivity can be expressed as
D = D 0 exp − E a RT(2)
where D 0 is a pre-exponential factor and E a the activation energy for diffusion. Hydrogen permeance (P/t, Equation (1)) values, measured at 300 • C for untreated membranes (not subjected to HTA), are plotted in Figure 2 as a function of inverse thickness. In the calculation of the permeance, n = 0.5 was applied, which is essentially valid only with bulk diffusion as the rate-limiting step [36][37][38][39][40][41]. When the kinetics is bulk-limited, the permeance should be proportional to the inverse thickness, leading to a constant value for the permeability (a material property). In thick Pd-membranes, hydrogen generally forms a dilute solution and the transport is bulk-limited. The full line (Figure 2) refers to a bulk value of permeability equal to 1.5 × 10 −8 mol·m·m −2 ·s −1 ·Pa −0.5 that has been reported for a 100 µm thick Pd77%Ag23% membrane at 300 • C [5]. A previous investigation of pure Pd membranes in the thickness range 10 to 150 µm indicated that bulk diffusion was rate limiting for thicknesses above 20 µm [37]. As the thickness decreases, the transport mechanism may be controlled by a combination of surface effects and bulk diffusion (0.5 < n < 1) [42,43]. Eventually, surface phenomena such as adsorption/dissociation and/or association/desorption become completely rate-limiting, and the pressure exponent approaches unity [36][37][38][39][40][41]. Figure 2 indicates a bulk limited transport with permeance values somewhat higher than the bulk literature value for the thicker membranes (≤4.7 µm), while the thinnest membranes exhibit permeance values indicative of surface limitations affecting hydrogen permeation. The thickness at which this transition appears may depend both on the conditions (T, P, H 2 feed content) and the material properties as affected by the fabrication and eventual pre-treatment of the membrane. Several studies report that surface phenomena start to have an impact from 4-5 µm [10,29,40,44]. There are some variations in the measured permeance between membranes of the same thickness; larger for the 2.2 µm membrane relative to the 4.7 µm and 8.5 µm membrane. There could be several reasons for this variation, including experimental uncertainty. There may be a gradient in membrane thickness as large as~10% across the silicon wafer, but we take care to mainly utilize the mid-sections for permeation experiments to reduce this deviation. Time and contamination during ambient storage may have an effect, as well as slight stretching of the material under total pressure difference [10]. Such sputtered membranes of similar thickness are, however, not found to exhibit major differences in microstructure, composition, or surface topography [10,45,46], but a general observation that will be further discussed below is that this variation between principally equivalent samples is also reduced by HTA [10].
After stabilization under hydrogen and measurement of the permeance, membranes with thicknesses of 2.2, 4.7, and 8.5 µm were subjected to the three-step HTA procedures as described above. The results are displayed in Figure 3 and Table 1. Figure 3a shows the hydrogen permeance plotted as a function of inverse thickness before HTA as well as after each step in the HTA procedure; n assumed equal to 0.5 also here. HTA has larger effect as the thickness decreases, with practically no effect for the 8.5 µm thick membrane. Moreover, the permeance increases after each of the first two HTA steps, i.e., upon oxidation-reduction of each side of the membrane. The first increase amounts to~20% (HTA permeate/substrate) while the second (HTA feed/growth) is 60-40% (Table 1), depending on temperature, for the 2.2 µm membrane. There is no significant change when both sides are simultaneously exposed one more time to air. Figure 3a also implies that the permeance is inversely proportional to the membrane thickness after HTA. Hence, the oxidation-reduction cycle imposed by the HTA procedure apparently shifts the surface transport limitation to lower thickness and bulk diffusion becomes rate-limiting for the hydrogen transport over the whole thickness range and experimental conditions investigated. Moreover, the surface limitations appear to impose transport limitations on both sides initially, which can be lifted stepwise by oxidizing one side at the time. In order to investigate the importance of the order of the heat treatment with respect to growth/feed or substrate/permeate side of the membrane an experiment in the opposite order (HTA2) was performed for the 2.2 µm thickness as mentioned above. The results are displayed in Figure 3b and in Table 1. The stepwise increase in permeability is definitely maintained, possibly with some differences due to the order, i.e., feed or permeate side first. The relative increases are now~40% (HTA feed/growth) followed by 70-30% (HTA permeate/substrate) with increasing temperature, to eventually reach similar permeances values as for the main HTA sequence. Conclusions with respect to order are, however, complicated by the variation in values obtained for the hydrogen stabilization as discussed above. The dissociative adsorption of hydrogen over palladium surface atoms is practically non-activated [47]. It is thus difficult to ascribe the observed permeation increase on the feed side for either of the sequences in terms of adsorption properties only. Moreover, the hydrogen-stabilization as well as the HTA should have promoted Pd termination of the surface over Ag, but (temperature dependent) coverage effects may complicate the segregation behavior [48]. Nevertheless, the subsurface structure and elemental distribution may also be affected by the treatment and play a role in the transfer from the surface to the bulk and may affect both sides.
After exposure to air of both sides of the membranes, the permeability approaches a value of 2.1 ± 0.1 × 10 −8 ·mol·s −1 ·m −2 ·Pa −0.5 at 300 • C, as shown by Table 1 as well as the values for the 4.7 µm thickness (not shown). This is comparable to previous values reported in literature for similar membranes [10], for which the HTA also seems to partially diminish the variations between samples from different wafers or fabrication batches that is observed during the initial stabilization under hydrogen. The oxidation-reduction cycle may hence induce a higher degree of structural and compositional uniformity. The flux increase after HTA of both sides of the thinnest membrane corresponds to a doubling of the permeability, also in accordance with what has been previously reported in literature [10,13,14,16], although a comparison of permeabilities based on n equal to 0.5 is not valid in the strictest sense. The final permeability value at 300 • C is, however, higher than the value of 1.5 × 10 −8 ·mol·m·m −2 ·s −1 ·Pa −0.5 at 300 • C expected for bulk-limited transport reported in literature [5]. This could be related to differences in grain structure/density [29], grain orientation (the sputtered PdAg films contain predominantly grains oriented along <111> parallel/normal to the surface [49]), as well as purity, but requires further investigation.
Hydrogen Solubility and Diffusivity
In addition to hydrogen permeation experiments before and after the three-step heat treatment procedure, hydrogen sorption measurements were carried out to investigate possible variation caused by the HTA. The hydrogen solubility values were obtained before and after heat treatment in air of both sides simultaneously for 2.2 µm and 8.5 µm membranes, and the Sieverts' constants are reported in Table 2. Solubility decreases with increasing temperature, as expected [3,[50][51][52][53][54]. Moreover, the solubility increases as the thickness decreases as we have recently reported [29]. These thickness dependent changes in solubility were related to differences in the grain structure of the sputtered Pd-Ag films. After HTA of both sides, the values of Sieverts' constant remain basically unaffected for 300 and 400 • C. There is, however, some increase for the values at 350 • C, especially for the 8.5 µm. We are unsure whether this discrepancy can be considered an experimental error, but the data are not sufficient to conclude on significant HTA-induced changes in solubility. Previous results for a 25 µm cold-worked Pd-Ag25 wt.% indicated no change in hydrogen solubility after heat treatment in air [17,18].
Hydrogen diffusivities calculated based on reaction (1) for the 2.2 µm and 8.5 µm thick membranes before and after HTA are shown in Figure 4 as a function of inverse temperature. Estimated values for the pre-exponential factor (D 0 ) and activation energy (E a ) using Equation (2) are listed in Table 3. There are no significant changes found in diffusivity for the 8.5 µm membrane as both the permeability ( Table 2) and solubility (Table 3) are constant before and after HTA. The solubility value obtained after HTA at 350 • C has been omitted from the fit in Figure 4, but the values remain if it is taken in. The apparent activation energy of 20 kJ/mol (before and after HTA) is comparable to results obtained for Pd-Ag with bulk-limited kinetics. Völkl and Alefeld collected data for the diffusion coefficient of hydrogen in Pd from 25 authors and estimated a mean value of E a~2 2.4 kJ/mol and D 0 2.9 × 10 −7 m 2 /s [55]. Moreover, Holleck calculated for a Pd80%Ag20% (0.08-0.20 cm thick) membrane values of E a of~22.3 ± 0.4 kJ/mol and D 0~( 2.33 ± 0.2) × 10 −7 m 2 /s [56]. This suggests that HTA does not change the hydrogen transport mechanism for thick sputtered Pd77%Ag23% membranes. Table 3. Estimated values of the pre-exponential factor (D 0 ) and of the activation energy (E a ) for 2.2 µm and 8.5 µm thick membranes before and after the main HTA sequence.
Sample Thickness (µm)
Before HTA After HTA D 0 (m 2 /s) E a (kJ/mol) D 0 (m 2 /s) E a (kJ/mol) 2.2 4.9 × 10 −7 29 3.6 × 10 −7 24 8.5
1.5 × 10 −7 20 1.7 × 10 −7 20
In the case of the 2.2 µm thick membrane, the permeability enhancement must be attributed to an apparent increase in the diffusivity since the solubility seems to remain constant. Both the pre-exponential factor and the activation energy changes after HTA: E a decreases from 29 kJ/mol before HTA to 24 kJ/mol after HTA on both sides, and similar values were obtained for the opposite order of stepwise air-treatment (HTA2). Since E a exceeds the values reported for thicker membranes in literature [56], this supports the idea that surface phenomena are rate-limiting before HTA. However, if the enhanced kinetics of hydrogen transport upon heat treatment in air is associated with a transition from surface to bulk limited transport, there should be a change in the n-value that essentially complicates the comparison by fitting. However, comprehensive analysis to extract n-values also requires a larger pressure range that what could been applied here [11,35]. Nevertheless, the activation energies associated with (associative) desorption should be generally higher than those for diffusion, but may depend on the surface composition (Pd/Ag) as well as the coverage as discussed in [29].
Surface Topography
AFM was used in order analyze how the hydrogen stabilization and HTA procedure affects the surface topography of the different membranes. Figures 5 and 6 show representative AFM images of 2.2 µm and 8.5 µm thick as-grown, hydrogen-stabilized, and air-treated membranes. The corresponding roughness values of all the measured membranes are reported in Table 4. The feed/growth side of as-grown samples shows an increase in the surface roughness as the thickness increases. The corresponding permeate/substrate side is very smooth (0.2-0.4 nm) with some variation in surface roughness between the different samples and thicknesses analyzed. This is in accordance with previous results for similar, sputtered membranes [10,29], and reflects the nature of the nucleation and growth phenomena involved during sputtering. A relatively high density of nuclei seem to form on the substrate, and then growth proceeds by continuing some grains while others are terminated [19]. Table 4. Surface roughness for as-grown membranes, after hydrogen stabilization and HTA with subsequent hydrogen stabilization obtained from AFM imaging analysis for both the growth/feed and substrate/permeate side. The analyzed areas are based on (5 × 5) µm 2 images except for the substrate/permeate side as-grown membranes where images with an area of (1 × 1) µm 2 are used. Upon hydrogen permeation, the feed side surface roughness is found to increase moderately, while the effect of H 2 stabilization on the permeate side is found to be strongly thickness dependent. Hydrogen exposure/permeation has already been reported to increase the surface roughness of 1.3 µm sputtered Pd-Ag films [10]. For thick membranes (≥8.5 µm), hydrogen exposure causes only small changes to the surface structure. The permeate side becomes more roughened as the thickness decreases and the surface roughness of the 2.2 µm membrane becomes comparable for the two opposite sides. The reason behind this trend is not known, and it has-to our knowledge-not been reported before. The thickness dependent surface roughening on the permeate side under hydrogen permeation may possibly be connected to the fact that thinner membranes experience higher hydrogen flux than thicker membranes. In general, substantial roughening is associated with grain growth [19,29] and the higher hydrogen flux should hence facilitate restructuring and grain growth. After the HTA procedure and subsequent hydrogen stabilization the surface topology undergoes further changes, depending on thickness. For the thickest (8.5 µm) membrane analyzed, the roughness of the feed side is mainly enhanced upon exposure to hydrogen while the HTA procedure has only minor effect ( Figure 5). The permeate side, on the other hand, is strongly roughened after HTA. The feed side of the 4.7 µm thick membrane, already roughened during the hydrogen stabilization step, has yet another increase in roughness once oxidized. A similar behavior is also observed for the permeate side. Heat treatment in air contributes to a strong additional increase in surface roughness of feed side for the 2.2 µm membrane ( Figure 4, Table 2). The permeate side roughness, instead, is enhanced only after hydrogen exposure to around 12 nm, and no further increase after HTA is observed.
Membrane
Eventually, upon HTA the roughness values end up in the range of 20-30 nm on the growth/feed side and 9-15 nm on the substrate/permeate side, irrespective of the thickness dependent differences existing due to the growth process or developing during H 2 stabilization only. This is in agreement with several other investigations [10,13,14,17,22,23], reporting that the heat treatment in air helps the overall surface roughening process, thus creating new active sites and an increase of surface area. However, the roughening occurs also during hydrogen permeation-in particular for the thinner membranes-without observing an associated strong increase in flux. The permeation enhancement effect of the heat treatment in air can therefore not be fully attributed to an increase in surface area [14,19,57].
Conclusions
A three-step heat treatment in air has been performed on sputtered Pd77%Ag23% membranes with thickness ranging from 2.2 µm to 8.5 µm. The HTA is found to increase hydrogen permeability after each of the steps and to have a larger effect as the membrane thickness decreases. Air oxidation has no apparent effect on the hydrogen solubility, implying that enhancement in permeability may be related to an increase in diffusivity for thinner membranes (≤5 µm). The data also suggest that bulk diffusion is the rate-limiting step for transport after HTA for all membranes, while surface phenomena are rate-limiting for thinner membranes prior thermal air treatment. Moreover, AFM studies reveal that the HTA increases the surface roughness of the membranes. However, significant surface roughening is already experienced upon stabilization under hydrogen, in particular for the thinner membranes, indicating that increase in permeability is not only attributable to increased surface area.
Figure 1 .
1Sketch of the microchannel reactor configuration.
Figure 2 .
2Measured hydrogen permeance as function of inverse thickness at 300 • C for membranes not subjected to HTA. The full line refers to values of permeance reported if bulk is the rate limiting step (1.5 × 10 −8 ·mol·s −1 ·m −2 ·Pa −0.5 )[5].
Figure 3 .
3Permeance measured at 300 • C for each single step of heat treatment in air; (a) as function of inverse thickness for the main HTA membrane side sequence with the full line indicating a permeability of 2.1 × 10 −8 mol·s −1 ·m −2 ·Pa −0.5 , and (b) as function of the difference in the square root of the hydrogen partial pressure for the HTA2 membrane side sequence applied to a 2.2 µm thick membrane.
Figure 4 .
4Arrhenius plot of the diffusivity for 2.2 µm and 8.5 µm thick membranes before and after HTA of both sides for the temperature range 300-400 • C. The diffusivity scale is presented in logarithmic form and the dotted lines are linear fits.
Figure 5 .
5AFM images of the 2.2 µm thick membrane for the feed/growth side (left panel) and permeate/substrate side (right panel) for (a) as-grown; (b) hydrogen stabilized; and (c) HTA-subjected samples. Image areas: (a) right: 1 × 1 µm 2 ; rest: 5 × 5 µm 2 .
Figure 6 .
6AFM images of the 8.5 µm thick membrane for the feed/growth side (left panel) and permeated/substrate side (right panel) for (a) as-grown; (b) hydrogen stabilized; and (c) HTA-subjected samples. Image areas: (a) right and (b) right: 1 × 1 µm 2 ; rest: 5 × 5 µm 2 .
Author
Contributions: Conceptualization, T.P. and H.V.; Methodology, T.P., H.V., and R.B.; Validation, N.V., H.V. and I.-H.S.; Investigation, N.V.; Resources, T.P. and N.V.; Writing-Original Draft Preparation, N.V. and I.-H.S.; Writing-Review & Editing, T.P. and H.V. and R.B.; Visualization, N.V., I.H.S.; Supervision, H.V.; Project Administration, T.P. and H.V.; Funding Acquisition, T.P. and R.B. Funding: This research was funded by the Research Council of Norway through the RENERGI Program (190779/S60) and CLIMIT Program (215666/E20), and NTNU, SINTEF and Statoil ASA through the Gas Technology Centre NTNU-SINTEF.
Table 1 .
1Permeability measured at 300 • C after before, between and after each of the three steps in the main HTA membrane side sequences for the 2.2 µm thick membranes.T ( • C)
Permeability 10 8 (mol·m·m −2 ·s −1 ·Pa −0.5 )
Main HTA Sequence
HTA2 Sequence
Before
Feed
Perm
Both
Before Feed
Perm
Both
300
1.1
1.3
2.1
2.0
0.9
1.3
2.2
2.1
350
1.2
1.5
2.3
2.3
1.1
1.6
2.4
2.3
400
1.5
1.8
2.5
2.5
1.5
2.1
2.7
2.7
Table 2 .
2Sieverts' constant measured at different temperature for 2.2 µm and 8.5 µm thick membranes before and after heat treatment in air.Sample Thickness (µm)
Temperature ( • C)
Sieverts' Constant (µmol/g·Pa 0.5 )
Before HTA
After HTA
8.5
300
0.77
0.79
350
0.53
0.63
400
0.44
0.45
2.2
300
0.82
0.81
350
0.57
0.60
400
0.47
0.47
© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Acknowledgments: Marit Stange is gratefully acknowledged for the manufacturing of the Pd-alloy films and MSc Live Nova Naess is acknowledged for contributing with some of the AFM data.Conflicts of Interest:The authors declare no conflict of interest.
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| s2orc_abstract_body | 27 |
[TOMT] [books] [UK] Tim and the witch? | OK, this was a series of books from when I was in primary school in the late 80s. It may have been for readers aged 8, 9 or 10.
The premise was a series of books, possibly 'Tim' and a witch. But this kid was some how initiated into some kind of witch fraternity and had a cat, or familiar.
The books were small, not novel sized, and maybe had illustrations taking up the top half of pages. they seemed quite dark in nature, and were serialised.
Struggling to remember them. | reddit_title_body | 5 |
Reductive Lie Groups, such as the orthogonal groups, the Lorentz group, or the unitary groups, play essential roles across scientific fields as diverse as high energy physics, quantum mechanics, quantum chromodynamics, molecular dynamics, computer vision, and imaging. In this paper, we present a general Equivariant Neural Network architecture capable of respecting the symmetries of the finitedimensional representations of any reductive Lie Group G. Our approach generalizes the successful ACE and MACE architectures for atomistic point clouds to any data equivariant to a reductive Lie group action. We also introduce the lie-nn software library, which provides all the necessary tools to develop and implement such general G-equivariant neural networks. It implements routines for the reduction of generic tensor products of representations into irreducible representations, making it easy to apply our architecture to a wide range of problems and groups. The generality and performance of our approach are demonstrated by applying it to the tasks of top quark decay tagging (Lorentz group) and shape recognition (orthogonal group). |
Introduction
Convolutional Neural Networks (CNNs) (LeCun et al., 1989) have become a widely used and powerful tool for computer vision tasks, in large part due to their ability to achieve translation equivariance. This property led to improved generalization and a significant reduction in the number of parameters. Translation equivariance is one of many possible symmetries occurring in machine learning tasks.
A wide range of symmetries described by reductive Lie Groups is present in physics, such as O(3) in molecular mechanics, SO(1,3) in High-Energy Physics, SU(2 N ) in quantum mechanics, and SU(3) in quantum chromodynamics. Machine learning architectures that respect these symmetries often lead to significantly improved predictions while requiring far less training data. This has been demonstrated in many applications including 2D imaging with O(2) symmetry (Cohen and Welling, 2016a;Esteves et al., 2017), machine learning force fields with O(3) symmetry (Anderson et al., 2019;Bartók et al., 2013;Batzner et al., 2022;Batatia et al., 2022a) or jet tagging with SO + (1, 3) symmetry (Bogatskiy et al., 2022;.
One way to extend CNNs to other groups (Finzi et al., 2020; is through harmonic analysis on homogeneous spaces, where the convolution becomes an integral over the group. Other architectures work directly with finite-dimensional representations. We follow the demonstration of Bogatskiy et al. (2020a) who constructed a universal approximation of any equivariant map with a feed-forward neural network with vector activations belonging to finite-dimensional representations of a wide class of Lie groups. In this way, one can avoid computational challenges created by infinite-dimensional representations. Figure 1: Examples of natural science problems and associated reductive Lie groups. For high energy physics, the Lorentz group SO(1, 3); for chemistry, the Euclidean group E(3); for quantumchromodynamics, the SU(3) group.
Alternatively, our current work can be thought of as a generalization of the Atomic Cluster Expansion (ACE) formalism of Drautz (2019) to general Lie groups. The ACE formalism provides a complete body-ordered basis of O(3)-invariant features. By combining the concepts of ACE and E(3)equivariant neural networks, Batatia et al. (2022a) proposed the MACE architecture, which achieves state-of-the-art performance on learning tasks in molecular modelling. The present work generalizes the ACE and MACE architectures to arbitrary Lie groups in order to propose a generic architecture for creating representations of geometric point clouds in interaction.
Concretely, our work makes the following contributions:
• We develop the G-Equivariant Cluster Expansion. This new framework generalizes the ACE (Drautz, 2019) and MACE (Batatia et al., 2022b) architectures to parameterize properties of point clouds that are equivariant under the action of a reductive Lie group G. • We prove that our architecture is universal, even for a single layer. • We introduce lie-nn, a new library providing all the essential tools to apply our framework to a variety of essential Lie Groups in physics and computer visions, including the Lorentz group, SU(N ), SL 2 (C) and product groups. • We demonstrate the generality and efficiency of our general-purpose approach by demonstrating excellent accuracy on two prototype applications, jet tagging, and 3D point cloud recognition.
Background
We briefly review a few important group-theoretic concepts: A real (complex) Lie group is a group that is also a finite-dimensional smooth (complex) manifold in which the product and inversion of the group are also smooth (holomorphic) maps. Among the most important Lie groups are Matrix Lie groups, which are closed subgroups of GL(n, C) the group of invertible n × n matrices with complex entries. This includes well-known groups such as Sp(2n, R) consisting of matrices of determinant one, that is relevant in Hamiltonian dynamics A finite-dimensional representation of the Lie group G is a finite-dimensional vector space V endowed with a smooth homomorphism ρ : G → GL(V ). Features in the equivariant neural networks live in these vector spaces. An irreducible representation V is a representation that has no subspaces which are invariant under the action of the group (other than {0} and V itself). This means that V can not be decomposed non-trivially as the direct sum of representations. A reductive group over a field F is a (Zariski-) closed subgroup of the group of matrices GL(n, F ) such that every finite-dimensional representation of G on an F -vectorspace can be decomposed as a sum of irreducible representations.
Related Work
Lie group convolutions Convolutional neural networks (CNNs), which are translation equivariant, have also been generalized to other symmetries. For example, G-convolutions (Cohen and Welling, 2016b) generalized CNNs to discrete groups. Steerable CNNs (Cohen and Welling, 2016a) generalized CNNs to O(2) equivariance and Spherical CNNs (Cohen et al., 2018) O(3) equivariance. A general theory of convolution on any compact group and symmetric space was given by . This work was further extended to equivariant convolutions on Riemannian manifolds by Weiler et al. (2021). ACE The Atomic Cluster Expansion (ACE) (Drautz, 2019) introduced a systematic framework for constructing complete O(3)-invariant high body order basis sets with constant cost per basis function, independent of body order (Dusson et al., 2022). e3nn + Equivariant MLPs The e3nn library (Geiger and Smidt, 2022) provides a complete solution to build E(3)−equivariant neural networks based on irreducible representations. The Equivariant MLPs (Finzi et al., 2021) include more groups, such as SO(1, 3), Z n , but are restricted to reducible representations making them much less computationally efficient than irreducible representations. Equivariant MPNNs and MACE Equivariant MPNNs Anderson et al., 2019;Bogatskiy et al., 2020a;Satorras et al., 2021;Brandstetter et al., 2022;Batzner et al., 2022) have emerged as a powerful architecture to learn on geometric point clouds. They construct permutation invariants and group equivariant representations of point clouds. Successful applications include simulations in chemistry, particle physics, and 3D vision. MACE (Batatia et al., 2022a) generalized the O(3)-Equivariant MPNNs to build messages of arbitrary body order, outperforming other approaches on molecular tasks. (Batatia et al., 2022b) showed that the MACE design space is large enough to include most of the previously published equivariant architectures.
The G-Equivariant Cluster Expansion
We are concerned with the representation of properties of point clouds. Point clouds are described as multi-sets (unordered tuples) X = [x i ] i where each particle x i belongs to a configuration domain Ω. We denote the set of all such multi-sets by msets(Ω). For example, in molecular modeling, x i might describe the position and species of an atom and therefore x i = (r i , Z i ) ∈ R 3 × Z, while in high energy physics, one commonly uses the four-momentum x i = (E i , p i ) ∈ R 4 , but one could also include additional features such as charge, spin, and so forth.
A property of the point cloud is a map
Φ : msets(Ω) → Z(1)
i.e., X → Φ(X) ∈ Z, usually a scalar or tensor. The range space Z is application dependent and left abstract throughout this paper. Expressing the input as a multi-set implicitly entails two important facts: (1) it can have varying lengths; (2) it is invariant under the permutations of the particles. The developed in this article are also applicable to fixed-length multi-sets, in which case Φ is simply a permutation-invariant function defined on some Ω N . Mappings that are not permutation-invariant are special case with several simplifications.
In many applications, especially in the natural sciences, particle properties satisfy additional symmetries. When a group G acts on Ω as well as on Z we say that Φ is G-equivariant if
Φ • g = ρ Z (g)Φ, g ∈ G(2)
where ρ Z (g) is the action of the group element g on the range space Z. In order to effectively incorporate exact group symmetry into properties Φ, we consider model architectures of the form
Φ : msets(Ω) −→ embedding V −→ parameterization V −→ readout Z,(3)
where the space V into which we "embed" the parameterization is a possibly infinite-dimensional vector space in which a convenient representation of the group is available. For simplicity we will sometimes assume that Z = V .
The Atomic Cluster Expansion (ACE) framework (Drautz, 2019;Dusson et al., 2022;Drautz, 2020)) produces a complete linear basis for the space of all "smooth" G-equivariant properties Φ for the specific case when G = O(3) and x i are vectorial interatomic distances. Aspects of the ACE framework were incorporated into E(3)-equivariant message passing architectures, with significant improvements in accuracy (Batatia et al., 2022a). In the following paragraphs we demonstrate that these ideas readily generalize to arbitrary reductive Lie groups.
Efficient many-body expansion
The first step is to expand Φ in terms of body orders, and truncate the expansion at a finite order N :
Φ (N ) (X) = φ 0 + i φ 1 (x i ) + i1,i2 φ 2 (x i1 , x i2 ) + · · · + i1,...,i N φ N (x i1 , . . . , x i N ),(4)
where φ n defines the n-body interaction. Formally, the expansion becomes systematic in the limit as N → ∞. The second step is the expansion of the n-particle functions φ n in terms of a symmetrized tensor product basis. To define this we first need to specify the embedding of particles x: A countable family (ϕ k ) k is a 1-particle basis if they are linearly independent on Ω and any smooth 1-particle function φ 1 (not necessarily equivariant) can be expanded in terms of (ϕ k ) k , i.e,
φ 1 (x) = k w k ϕ k (x).(5)
For the sake of concreteness, we assume that ϕ k : Ω → C, but the range can in principle be any field. Let a complex vector space V be given, into which the particle embedding maps, i.e.,
(ϕ k (x)) k ∈ V ∀x ∈ Ω.
As a consequence of (5) any smooth scalar n-particle function φ n can be expanded in terms of the corresponding tensor product basis,
φ n (x 1 , . . . , x n ) = k1,...,kn w k1...kn n s=1 ϕ ks (x s ).(6)
Inserting these expansions into (4) and interchanging summation (see appendix for the details) we arrive at a model for scalar permutation-symmetric properties,
A k = x∈X ϕ k (x), A k = n s=1 A k , Φ (N ) = k∈K w k A k ,(7)
where K is the set of all k tuples indexing the features A k . Since A k is invariant under permuting k, only ordered k tuples are retained. The features A k are an embedding of msets(Ω) into the space V . The tensorial product features (basis functions) A k form a complete linear basis of multi-set functions on Ω and the weights w k can be understood as a symmetric tensor. We will extend this linear cluster expansion model Φ (N ) to a message-passing type neural network model in § 4.4.
We remark that, while the standard tensor product embeds (⊗ n s=1 ϕ ks ) k : Ω n → V n , the ncorrelations A k are symmetric tensors and embed (A k ) k : msets(Ω) → Sym n V .
Symmetrisation
With (7) we obtained a systematic linear model for (smooth) multi-set functions. It remains to incorporate G-equivariance. We assume that G is a reductive Lie group with a locally finite representation in V . In other words we choose a representation ρ = (ρ kk ′ ) : G → GL(V ) such that
ϕ k • g = k ′ ρ kk ′ (g)ϕ k ′ ,(8)
where for each k the sum over k ′ is over a finite index-set depending only on k. Most Lie groups one encounters in physical applications belong to this class, the affine groups being notable exceptions. However, those can usually be treated in an ad hoc fashion, which is done in all E(3)-equivariant architectures we are aware of. In practice, these requirements restrict how we can choose the embedding (ϕ k ) k . If the point clouds X = [x i ] i are already given in terms of a representation of the group, then one may simply construct V to be iterative tensor products of Ω; see e.g. the MTP (Shapeev, 2016) and PELICAN (Bogatskiy et al., 2022) models. To construct an equivariant two-particle basis we need to first construct the set of all intertwining operators from V ⊗ V → V . Concretely, we seek all solutions C α,K k1k2 to the equation
k ′ 1 k ′ 2 C α,K k ′ 1 k ′ 2 ρ k ′ 1 k1 (g)ρ k ′ 2 k2 (g) = K ′ ρ KK ′ (g)C α,K ′ k1k2 ;(9)
or, written in operator notation,
C α ρ ⊗ ρ = ρC α .(10)
We will call the C α,K k generalized Clebsch-Gordan coefficients since in the case G = SO(3) acting on the spherical harmonics embedding ϕ lm = Y m l those coefficients are exactly the classical Clebsch-Gordan coefficients. The index α enumerates a basis of the space of all solutions to this equation. For the most common groups, one normally identifies a canonical basis C α and assigns a natural meaning to this index (cf. § A.2). Our abstract notation is chosen because of its generality and convenience for designing computational schemes. The generalization of the Clebsch-Gordan equation (9) to n products of representations acting on the symmetric tensor space
Sym n (V ) becomes (cf. § A.6) k ′ C α,K k ′ ρ k ′ k = K ′ ρ KK ′ C α,K ′ k ∀K, k = (k 1 , . . . , k N ), g ∈ G,
where
ρ k ′ k = k ′′ =πk ′ π∈Sn ρ k ′′ k and ρ k ′ k = n t=1 ρ k ′ t kt .(11)
Due to the symmetry of the (A k ) k tensors C α,K k need only be computed for ordered k tuples and the sum k ′ also runs only over ordered k tuples. Again, the index α enumerates a basis of the space of solutions. Equivalently, (11) can be written in compact notation as
C α ρ = ρC α .(12)
These coupling operators for N products can often (but not always) be constructed recursively from couplings of pairs (9).
We can now define the symmetrized basis
B K α = k ′ C α,K k ′ A k ′ .(13)
The equivariance of (13) is easily verified by applying a transformation g ∈ G to the input (cf § A.3).
Universality: In the limit as the correlation order N → ∞, the features (B K α ) K,α form a complete basis of smooth equivariant multi-set functions, in a sense that we make precise in Appendix A.4. Any equivariant property Φ V : Ω → V can be approximated by a linear model
Φ K V = α c K α B K α ,(14)
to within arbitrary accuracy by taking the number of terms in the linear combination to infinity.
Dimension Reduction
The tensor product of the cluster expansion in (7) is taken on all the indices of the one-particle basis. Unless the embedding (ϕ k ) k is very low-dimensional it is often preferable to "sketch" this tensor product. For example, consider the canonical embedding of an atom
x i = (r i , Z i ), ϕ k (x i ) = ϕ znlm (x i ) = δ zZi R nl (r i )Y m l (r i ).
Only the (lm) channels are involved in the representation of O(3) hence there is considerable freedom in "compressing" the (zn) channels.
Following Darby et al. (2022) we construct a sketched G-equivariant cluster expansion: We endow the one-particle basis with an additional index c, referred to as the sketched channel, replacing the index k with the index pair (c, k), and renaming the embedding (ϕ ck ) c,k . In the case of three-dimensional particles one may, for example, choose c = (z, n). In general it is crucial that the representation remains in terms of the ρ k,k ′ , that is, (8) becomes
ϕ ck • g = k ′ ρ kk ′ (g)ϕ ck ′ .(15)
Therefore, manipulating only the c channel does not change any symmetry properties of the architecture. We can use this fact to admit a learnable embedding,
A ck = c ′ w cc ′ ϕ c ′ k ,
This mechanism is employed in numerous architectures to reduce the dimensionality of the embedding, but the approach taken in by Darby et al. (2022) and Batatia et al. (2022b) and followed here is the exact opposite: we allow many more learnable c channels but then decouple them resulting in a much lower-dimensional basis of n-correlations, defined bỹ
A ck = n t=1 c ′ w cc ′ x∈X ϕ c ′ kt (x) .(16)
The resulting symmetrized basis is then obtained by
B K cα = k ′ C α,K k ′Ãck ′ .(17)
Following the terminology of Darby et al. (2022) we call this architecture the tensor-reduced ACE, or, G-TRACE. There are numerous natural variations on its construction, but for the sake of simplicity, we restrict our presentation to this one case.
Universality: Following the proof of Darby et al. (2022) one can readily see that the G-TRACE architecture inherits the universality of the cluster expansion, in the limit of decoupled channels #c → ∞. A smooth equivariant property Φ may be approximated to within arbitrary accuracy by an expansion Φ K (X) ≈ c,α c K α B K c,α (X). Since the embeddingà ck is learnable, this is a nonlinear model. We refer to § A.4 for the details.
G-MACE, Multi-layer cluster expansion
The G-equivariant cluster expansion is readily generalized to a multi-layer architecture by reexpanding previous features in a new cluster expansion (Batatia et al., 2022b). The multi-set X is endowed with extra features, h t i = (h t i,cK ) c,K , that are updated for t ∈ {1, ..., T } iterations. These features themselves are chosen to be a field of representations such that they have a well-defined transformation under the action of the group. This results in
x t i = (x i , h t i ) (18) ϕ t ck (x i , h t i ) = α w t,ck α k ′ ,k ′′ C α,k k ′ k ′′ h t i,ck ′ ϕ ck ′′ (x i )(19)
The recursive update of the features proceeds as in a standard message-passing framework but with the unique aspect that messages are formed via the G-TRACE and in particular can contain arbitrary high correlation order:.
m t i,cK = α W t,cK α B t,K cα .(20)
The gathered message m t i = (m t i,cK ) c,k is then used to update the particle states,
x t+1 i = (x i , h t+1 i ), h t+1 i = U t m t i ,(21)
where U t can be an arbitary fixed or learnable transformation (even the identity). Lastly, a readout function maps the state of a particle to a target quantity of interest, which could be local to each particle or global to the mset X,
y i = T t=1 R loc t (x t i ), respectively, y = T t=1 R glob t ({x t i } i ).(22)
This multi-layer architecture corresponds to a general message-passing neural network with arbitrary body order of the message at each layer. We will refer to this architecture as G-MACE. The G-MACE architecture directly inherits universality from the G-ACE and G-TRACE architectures: Theorem 4.1 (Universality of G-MACE). Assume that the one-particle embedding (ϕ k ) k is a complete basis. Then, the set of G-MACE models, with a fixed finite number of layers T , is dense in the set of continuous and equivariant properties of point clouds X ∈ msets(Ω), in the topology of pointwise convergence. It is dense in the uniform topology on compact and size-bounded subsets.
lie-nn : Generating Irreducible Representations for Reductive Lie Groups
In order to construct the G-cluster expansion for arbitrary Lie groups, one needs to compute the generalized Clebsch-Gordan coefficients (11) for a given tuple of representations (see 13). To facilitate this task, we have implemented an open source software library, lie-nn 1 . In this section we review the key techniques employed in this library.
Lie Algebras of Reductive Lie Groups
Formally, the Lie algebra of a Lie group is its tangent space at the origin and carries an additional structure, the Lie bracket. Informally the Lie algebra can be thought of as a linear approximation to the Lie group but, due to the group structure, this linear approximation carries (almost) full information about the group. In particular the representation theory of the Group is almost entirely determined by the Lie algebra, which is a simpler object to work with instead of the fully nonlinear Lie group.
Lie algebra The Lie groups we study can be realized as closed subgroups G ⊂ GL n (R) of the general linear group. In that case their Lie algebras can be concretely realized as g = Lie(G) = {X ∈ M n (R) | ∀t ∈ R : exp(tX) ∈ G} where exp(X) = 1 + X + 1 2 X 2 ... is the standard matrix exponential. It turns out that g ⊂ M n (R) is a linear subspace closed under the commutator bracket [X, Y ] = XY − Y X.
Structure theory We fix a linear basis {X i } ⊂ g, called a set of generators for the group. The Lie algebra structure is determined by the structure constants A ijk defined by
[X i , X j ] = k A ijk X k , in that if X = i a i X i and Y = j b j X j then [X, Y ] = k i,j A ijk a i b j X k .
The classification of reductive groups provides convenient generating sets for their Lie algebras (or their complexifications). One identifies a large commutative subalgebra h ⊂ g (sometimes of g C = g ⊗ R C) with basis {H i } so that most (or all) of the other generators E α can be chosen so that [H i , E α ] = α(H i )E α for a linear function α on h. These functions are the so-called roots of g. Structural information about g is commonly encoded pictorially via the Dynkin diagram of g, a finite graph the nodes of which are a certain subset of the roots. There are four infinite families of simple complex Lie algebras A n = su(n + 1), B n = so(2n + 1), C n = sp(2n), D n = so(2n) and further five exceptional simple complex Lie algebras (a general reductive Lie algebra is the direct sum of several simple ones and its centre). The Lie algebra only depends on the connected component of G. thus when the group G is disconnected in addition to the infinitesimal generators {X i } one also needs to fix so-called "discrete generators", a subset H ⊂ G containing a representative from each connected component. Representation theory The representation theory of complex reductive Lie algebras is completely understood. Every finite-dimensional representation is (isomorphic to) the direct sum of irreducible representations ("irreps"), with the latter parametrized by appropriate linear functional on h ("highest weight"). Further given a highest weight λ there is a construction of the associated irrep with an explicit action of the infinitesimal generators chosen above. The Weyl Dimension Formula gives the dimension of an irrep in terms of its highest weight.
Numerical Computations in lie-nn
The most basic class of the lie-nn library encodes a group G and infinitesimal representation dρ of g using the tuple
ρ := (A, n, {dρ(X i )} i , {ρ(h)} h∈H ) ,(23)
with A the structure constants of the group, n the dimension of the representation, and dρ(X i ) and ρ(h) being n × n matrices encoding the action of the infinitesimal and the discrete generators respectively. The action of infinitesimal generators is related to the action of group generators by the exponential, ∀X ∈ g, ρ(e X ) = e dρ(X) .
As the building blocks of the theory irreps are treated specially; the package implements functionality for the following operations for each supported Lie group:
• Constructing the irrep with a given highest weight.
• Determining the dimension of an irrep.
• Decomposing the tensor product of several irreps into irreps up to isomorphism (the selection rule, giving the list of irreducible components and their multiplicities). • Decomposing the tensor product of several irreps into irreps explicitly via a change of basis ("generalized Clebsch-Gordan coefficients"). • Computating the symmetrized tensor product of the group (see. A.6 for details).
To construct an irrep explicitly as in (23) one needs to choose a basis in the abstract representation space (including a labeling scheme for the basis) so that we can give matrix representations for the action of generators. For this purpose, we use in lie-nn the Gelfand-Tsetlin (GT) basis (Gelfand and Tsetlin, 1950) and associated labeling of the basis by GT patterns (this formalism was initially introduced for algebras of type A n but later generalized to all classical groups). Enumerating the GT patterns for a given algebra gives the dimension of a given irrep, the selection rules can be determined combinatorially, and it is also possible to give explicit algorithms to compute Clebsch-Gordan coefficients (the case of A n is treated by Alex et al. (2011)). For some specific groups, simplifications to this procedure are possible and GT patterns are not required.
In some cases, one wants to compute coefficients for reducible representations or for representations where the analytical computation with GT patterns is too complex. In these cases, a numerical algorithm to compute the coefficients is required. Let dρ 1 , dρ 2 be two Lie aglebra representations of interest. The tensor product on the Lie algebra dρ 1 ⊗ dρ 2 (X) can be computed as,
dρ 1 ⊗ dρ 2 (X) = dρ 1 (X) ⊗ 1 + 1 ⊗ dρ 2 (X)(24)
Therefore, given sets of generators of three representations dρ 1 , dρ 2 , dρ 3 , the Clebsch-Gordan coefficients are the change of basis between (dρ 1 (X) ⊗ 1 + 1 ⊗ dρ 2 (X)) and dρ 3 (X). One can compute this change of basis numerically via a null space algorithm. For some groups, one can apply an iterative algorithm that generates all irreps starting with a single representation, using the above-mentioned procedure (see A.7).
Applications
Lie groups and their applications
In Table 6.1 we give a non-exhaustive overview of Lie groups and their typical application domains, to which our methodology naturally applies.
Benchmarking our method on all of these applications is beyond the scope of the present work, in particular, because most of these fields do not have standardized benchmarks and baselines to compare against. The MACE architecture has proven to be state of the art for a large range of atomistic modeling benchmarks (Batatia et al., 2022a). In the next section, we choose two new prototypical applications and their respective groups to further assess the performance of our general approach. Table 1: Lie groups of interests covered by the present methods and their potential applications to equivariant neural networks. The groups above the horizontal line are already available in lie-nn. The ones below the line fall within our framework and can be added.
Group Application Reference
SU(1) Electromagnetism (Lagrave et al., 2021) SU(3) Quantum Chromodynamics (Favoni et al., 2022) SO(3) 3D point clouds (Batatia et al., 2022a)
SO + (1, 3)
Particle Physics (Bogatskiy et al., 2020b)
SL(3, R)
Point cloud classification -SU(2 N ) Entangled QP -
Sp(N )
Hamiltonian dynamics -SO(2N + 1) Projective geometry -6.2 Particle physics with the SO(1, 3)
Jet tagging consists in identifying the process that generated a collimated spray of particles called a jet after a high-energy collision occurs at particle colliders. Each jet can be defined as a multiset of
four-momenta [(E i , p i )] N i=1
, where E i ∈ R + and p i ∈ R 3 . Current state-of-the-art models incorporate the natural symmetry arising from relativistic objects, e.g, the Lorentz symmetry, as model invariance. To showcase the performance and generality of the G-MACE framework we use the Top-Tagging dataset (Butter et al., 2019), where the task is to differentiate boosted top quarks from the background composed of gluons and light quark jets. G-MACE achieves excellent accuracy, being the only arbitrary equivariant model to reach similar accuracy as PELICAN. We refer to Appendix A.8.1 for the details of the architecture. (Bogatskiy et al., 2022;Qu and Gouskos, 2020;Munoz et al., 2022;Bogatskiy et al., 2020a;Komiske et al., 2019;Pearkes et al., 2017).
3D Shape recognition
3D shape recognition from point clouds is of central importance for computer vision. We use the ModelNet10 dataset (Wu et al., 2015) to test our proposed architecture in this setting. As rotated objects need to map to the same class, we use a MACE model with O(3) symmetry. To create an encoder version of G-MACE, we augment a PointNet++ implementation (Yan, 2019) with G-MACE layers. See the appendix A.8.2 for more details on the architecture.
Architecture Accuracy
PointNet (Qi et al., 2016) 94.2 PointNet ++ (Qi et al., 2017) 95.0 PointMACE (ours) 96.1
Conclusion
We introduced the G-Equivariant Cluster Expansion, which generalizes the successful ACE and MACE architectures to symmetries under arbitrary reductive Lie groups. We provide an open-source Python library lie-nn that provides all the essential tools to construct such general Lie-group equivariant neural networks. We demonstrated that the general G-MACE architecture simultaneously achieves excellent accuracy in Chemistry, Particle Physics, and Computer Vision. Future development will implement additional groups and generalize to new application domains.
A Appendix
A.1 Proof of (7) This statement follows closely the arguments by Dusson et al. (2022); Drautz (2020) and others.
ϕ ks (x j ) = k w k n s=1 A k = k w k A k .
A.2 Custom notation and indexing
We briefly contrast our notation for Clebsch-Gordan coefficients (11) with the standard notation. By means of example, consider the group SO(3) in which case the Clebsch-Gordan equations are written as
m ′ 1 m ′ 2 C LM l1m ′ 1 l2m ′ 2 ρ l1 m ′ 1 m1 (g)ρ l2 m ′ 2 m2 (g) = M ′ ρ L M M ′ (g)C LM ′ l1m1l2m2 .(25)
In this setting, our index α simply enumerates all possible such coefficients. One can often assign a natural meaning to this index, e.g., for the group SO(3) it is given by the pair of angular quantum numbers (l 1 , l 2 ). Specifically, in this case, we obtain
C α,LM l1m1l2m2 = C LM l1m1l2m2 , if α = (l 1 , l 2 ), 0, otherwise,(26)
where C LM l1m1l2m2 are the Clebsch-Gordan coefficients in the classical notation. Thus, the additional index α is not really required in the case of SO(3), nor our other main example, SO(1, 3). Our notation is still useful to organize the computations of equivariant models, especially when additional channels are present, which is usually the case. Moreover, it allows for easy generalization to other groups where such a simple identification is not possible (Steinberg, 1961).
A.3 Equivariance of G-cluster expansion
The equivariance of the G-cluster expansion is easily verified by applying a transformation g to the input,
B K α • g = k C α,K k A k • g = k C α,K k k ′ t ρ kt,k ′ t (g)A k ′ = k ′ k C α,K k t ρ kt,k ′ t (g) A k ′ = k ′ K ′ ρ KK ′ (g)C α,K ′ k ′ A k ′ = K ′ ρ KK ′ (g)B K ′ α .(27)
4. The density of the basis B K α . As the last step one can readily observe that the symmetrization and cluster expansion steps can be exchanged. I.e. first symmetrizing and then employing the steps (7) result in the same model. Letting ϵ → 0 in the foregoing argument while fixing the number of particles #x results in all errors vanishing. Note that this will in particular require taking N → ∞.
Pointwise convergence.
To obtain density in the sense of pointwise convergence we first introduce the canonical cluster expansion without self-interacting terms
Φ K (x) = ∞ n=0 j1<···<jn v (n) K (x j1 , . . . x jn ).
The difference here is that the summation is only over genuine sub-clusters. Because of this restriction the series is finite for all multi-set inputs x. In other words, it converges in the pointwise sense.
One can easily see that v n can be chosen (explicitly) to make this expansion exact. After truncating the expansion at finite n ≤ N and then expanding the potentials v (n) K one can exactly transform the canonical cluster expansion into the self-interacting cluster expansion. This procedure is detailed in (Dusson et al., 2022;Drautz, 2020).
The arguments up to this point establish the claimed universality for the linear ACE model. The corresponding universality of the TRACE model follows immediately from (Darby et al., 2022). Since a single layer of the MACE model is a TRACE model, this completes the proof of Theorem 4.1.
A.5 Product of groups
Let G 1 and G 2 be two reductive Lie groups, and form the direct product group G 1 × G 2 . and ρ 1 be a associated irreducible representations then ρ 1 ⊗ ρ 2 is an irreducible representation of G 1 × G 2 . One can then generate any Clebsch-Gordan coefficient of the product group G 1 × G 2 using the algorithm presented above. It is of particular interest in the case of the equivariant message passing networks on points clouds, where the group of interest is G × S n .
A.6 Symmetric Tensor products
The permutation group is an important concept in the context of tensor products. It can be useful to focus on a subset of the full tensor product space that exhibits certain permutation equivariance. For example, the spherical harmonics are defined as the permutation-invariant part of a tensor product.
The symmetric tensor product can be thought of as a change of basis, or projector, from the tensor product to the symmetric part of the tensor product. In the case of a tensor product of correlation order four we have,
S ν = B ν;ijkl x i y j z k w l(28)
where B is the change of basis that satisfies:
B ν;ijkl = B ν;σ(ijkl) ∀σ ∈ S 4(29)
We propose in lie-nn a new algorithm used to calculate B. The Symmetric Tensor Product is calculated using a tree structure, starting at the leaves and progressing towards the trunk. The leaves are the basis of the individual indices, and they are combined and constrained at each step to impose symmetry.
A.7 Computing the irreps from input representations
For some groups, the computation of the generators X can become a very involved task. However in most applications, the data itself is already given in a form of a representation. One approach proposed by (Finzi et al., 2021) is to not work in the space of irreps but the space of polynomials of the input representation. This approach has the advantage of requiring little previous knowledge of the group. However it is also much less efficient than using irreps. One alternative way is to consider polynomials of the input representation, that are reducible and then compute the block diagonalisation to project down to irreps subspace. One can then work directly as polynomials in this subspace and compute Clebsch-Gordan coefficients numerically. We provide routines in lie-nn to carry out these operations from any given input representation.
A.8 Details of numerical experiments
A.8.1 Jet Tagging
Dataset The dataset (Butter et al., 2019) was generated using a Pythia, Delphes, and FastJet (using cuts for the jet's kinematics on ∆η = 2, R = 0.8) to simulate the response of the ATLAS detector at the Large Hadron Collider (LHC). The dataset is released under the "Creative Commons Attribution 4.0" license. The entire dataset contains 2 millions jets with a 60/20/20 for training, validation, and testing balanced splits.
Model The model uses 3 layers of the G-MACE architecture to generate the Lorentz group equivariant representation of each jet. For the 1 particle basis, we use a product of radial features on the Minkowski distances, and SO(1, 3) spherical harmonics. The radial features are computing by passing a logarithmic radial basis as in (Bogatskiy et al., 2022) into a [64, 64, 64, 512] MLP using SiLU nonlinearities on the outputs of the hidden layers. The internal representations used are (0, 0) and (1, 1). We use 72 channels for each representation. For the embedding, and readout out, we use similar achitectures to LorentzNet.
Training Models were trained on an NVIDIA A100 GPU in single GPU training. Typical training time for the dataset is up to 72 hours. Models were trained with AMSGrad variant of Adam, with default parameters of β 1 = 0.9, β 2 = 0.999, and ϵ = 10 −8 . We used a learning rate of 0.0035 and a batch size of 64. The model was trained for 80 epochs with 2 epochs of linear learning rate warmup and followed by a phase of cosine annealing LR scheduling.
A.8.2 3D shape recognition Dataset ModelNet10 (Wu et al., 2015) is a synthetic 3D object point clouds dataset containing 4,899 pre-aligned shapes from 10 categories. The dataset is split into 3,991 (80%) shapes for training and 908 (20%) shapes for testing. We were unable to find a license.
Model The model uses a three-layer encoder architecture following the PointNet++ one. We use an encoder of the full point cloud into sub-point clouds of sizes [1024,256,128]. Each PointNet layer maps a point cloud of size N t to one of size N t+1 . We compute the node features as the sum of the PointNet output and the MACE output, h (t+1) = PointNet(xyz (t) , h (t) ) + MACE(xyz (t) , h (t) )
Training Models were trained on an NVIDIA A100 GPU in single GPU training. The typical training time for the dataset is up to 12 hours. Models were trained with the AMSGrad variant of Adam, with default parameters of β 1 = 0.9, β 2 = 0.999, and ϵ = 10 −8 .
A.9 Limitations and Future Work
The spectrum of potential applications of the present method is very large. In this paper, we focus on a subset of applications that have known benchmarks and baselines. A broader range of groups is implemented in the lie-nn library. Future work should focus on applying this architecture to tasks with domain-specific knowledge.
Figure 2 :
2Examples of Dynkin diagrams and their associated group class.
Table 2 :
2Comparisson between state-of-the-art metrics on the Top-Tagging dataset. Scores were taken from
Table 3 :
3Accuracy in shape recognition.
https://github.com/lie-nn/lie-nn
Acknowledgments and Disclosure of Funding IB's work was supported by the ENS Paris Saclay. CO's work was supported by NSERC Discovery Grant IDGR019381 and NFRF Exploration Grant GR022937. This work was also performed using resources provided by the Cambridge Service for Data Driven Discovery (CSD3).IB would like to thank Gábor Csányi for his support.A.4 Completeness of the basis and Universality of MACEWe explain in which sense the basis B K α is a complete basis, and briefly sketch how to prove this claim. The argument is contained almost entirely in(Dusson et al., 2022)and only requires a single modification, namely Step 3 below, using a classical argument from representation theory. We will therefore give only a very brief summary and explain that necessary change.We start with an arbitrary equivariant property Φ V embedded in V where we have a representation, i.e. the actual target property is Φ is then given as a linear mapping from V to Z. For technical reasons, we require that only finitely many entries Φ V K may be non-zero, but this is consistent with common usage. For example, if G = O(3) and if Φ is a scalar, thenLM is non-zero if and only if L = 1; and so forth. For other groups, the labeling may differ but the principle remains the same.1. Convergence of the cluster expansion. The first step in our parameterisation is to approximate Φ V in terms of a truncated many-body expansion (4). It is highly application-dependent on how fast this expansion converges. Rigorous results in this direction in the context of learning interatomic potentials can be found in(Bachmayr et al., 2021;Thomas et al., 2022). A generic statement can be made if the number of input particles is limited by an upper bound, in which case the expansion becomes exact for a finite N . This case leads to the uniform density result stated in Theorem 4.1. We adopt this setting for the time being and return to the pointwise convergence setting below.In the uniform convergence setting we also require that the domain Ω is compact.Throughout the remainder of this section we may therefore assume that an N can be chosen as well as smooth components φ (n) such that the resulting model Φ V,N approximates Φ V to within a target accuracy ϵ,2. The density of the embedding. As already stated in the main text, if the components φ (n) K are smooth, and the embedding {ϕ k } k is dense in the space of one-particle functions (5) then it follows that the φ (n)K can be expanded in terms of the tensor product basis ϕ k := ⊗ n s=1 ϕ ks to within arbitrary accuracy. The precise statement is the following standard result of approximation theory: if span{ϕ k } k are dense in C(Ω), then span{ϕ k } k are dense in C(Ω n ). That is, for any ϵ > 0, there exist approximants pThe density of the symmetrized basis. The next and crucial step is to show that, if the φ (n) K are equivariant, then the p (n) K may be chosen equivariant as well without loss of accuracy. If the group G is compact then the representations ρ can be chosen unitary(Broecker, 1985). In that case, the argument from(Dusson et al., 2022)can be used almost verbatim: letwhere H is the normalized Haar measure thenp (n) is equivariant by construction andIf the group is not compact, then one can apply "Weyl's Unitary Trick" (see(Bourbaki, 1989), Ch. 3): first, one complexifies the group (if it is real) and then constructs a maximal compact subgroup K C of the complexification. This new group K will have the same representation as G and in virtue of being compact, that representation may again be chosen unitary. Therefore, symmetrizing p (n) with respect to K C results in an approximant that is not only equivariant w.r.t. K C but also equivariant w.r.t. G.
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| s2orc_abstract_body | 21 |
If they can remaster LEGO Star Wars the Complete Saga, they should make a new LEGO Harry Potter with the new wave. | Title says it all. I just think that LEGO Harry Potter which was great deserves a good remaster just like LSWTCS. Not that combine the video games shit. | reddit_title_body | 579 |
PASSIVE WI-FI: Bringing Low Power to Wi-Fi Transmissions | Wi-Fi has traditionally been considered a power-consuming communication system and has not been widely adopted in the sensor network and Internet of Things (IoT) space. We introduce Passive Wi-Fi that demonstrates that one can generate 802.11b transmissions using backscatter communication, while consuming 3-4 orders of magnitude lower power than existing Wi-Fi chipsets. Passive Wi-Fi transmissions can be decoded on any Wi-Fi device including routers, mobile phones and tablets. Our experimental evaluation shows that passive Wi-Fi transmissions can be decoded on off-the-shelf smartphones and Wi-Fi chipsets over distances of up to 100 feet. We also design a passive Wi-Fi IC that shows that 1 and 11 Mbps transmissions consume 14.5 and 59.2 ?W respectively. This translates to 10000x lower power than existing Wi-Fi chipsets and 1000x lower power than Bluetooth LE and ZigBee. | s2orc_title_abstract | 274 |
The activity of the PrkC protein kinase is regulated in a sophisticated manner in Bacillus subtilis cells.In spores, in the presence of muropeptides, PrkC stimulates dormancy exit. The extracellular region containing PASTA domains binds peptidoglycan fragments to probably enhance the intracellular kinase activity. During exponential growth, the cell division protein GpsB interacts with the intracellular domain of PrkC to stimulate its activity. In this paper, we have reinvestigated the regulation of PrkC during exponential and stationary phases. We observed that, during exponential growth, neither its septal localization nor its activity are influenced by the addition of peptidoglycan fragments or by the deletion of one or all PASTA domains. However, Dynamic Light Scattering experiments suggest that peptidoglycan fragments bind specifically to PrkC and induce its oligomerization. In addition, during stationary phase, PrkC appeared evenly distributed in the cell wall and the deletion of one or all PASTA domains led to a non-activated kinase. We conclude that PrkC activation is not as straightforward as previously suggested and that regulation of its kinase activity via the PASTA domains and peptidoglycan fragments binding occurs when PrkC is not concentrated to the bacterial septum, but all over the cell wall in non-dividing bacillus cells.Many bacteria possess a conserved family of serine/threonine protein kinases (STPK) 1 that are involved in the regulation of several cellular processes 2-5 . These enzymes are composed of an intracellular kinase domain resembling the catalytic domain of Hanks-type kinases and, for most, a short transmembrane trait (TM) and an extracellular regulatory C-terminal region containing β-lactam-binding domains 6-8 . These PASTA domains (for penicillin-binding protein and serine/threonine kinase associated domains) are specifically found in bacteria and notably in Firmicutes and in Actinobacteria. They are shown to interact with β-lactam antibiotics 9,10 , peptidoglycan (PG) fragments 6,11 and Lipid II 12 . Despite a poor conservation of their amino acid sequence, the PASTA domains share a globular fold formed by one α helix facing three β strands 13 . The number of these PASTA repeats varies also among STPKs 1,14 but they are predicted to be signal-binding domains sensing the state of the cell wall. One of the best-characterized STPKs is the PrkC protein from B. subtilis. It is constituted of an intracellular kinase domain, a short transmembrane helix and an extracellular region with a linear modular structure composed of three PASTA domains and a C-terminal domain, which structurally resembles an Ig fold presenting the typical features of adhesive proteins involved in cell-cell interactions or signaling 15,16 . Furthermore, unlike its homologues from other species like Mycobacterium tuberculosis or Streptococcus pneumoniae, the inactivation of PrkC does not impact cell division, cell shape or cell growth but rather alters stationary phase physiology and spore germination[17][18][19]. Like its S. pneumoniae homologue, PrkC is also expressed during exponential growth; it is localized at the septum of dividing cells and its activity is directly stimulated by the cytoplasmic cell division protein GpsB 20 . During stationary phase growth, B. subtilis PrkC seems to be required to limit cell lysis and thus, among the pleiotropic effects of prkC deletion, the lysis phenotype would rather be linked to the absence of the elongation factor G (EF-G) phosphorylation 17 . However, in the spore-forming bacteria B. subtilis, it has been proposed that the main function of PrkC is to mediate the exit of dormancy in response to PG fragments. Indeed, muropeptide fragments of the cell wall have been shown to stimulate germination of wild-type B. subtilis dormant spores whereas they have no effect on prkC-mutant spores. This stimulation requires the kinase activity of PrkC since germination is not activated in catalytic mutant (PrkC-K40A) spores 19 . Furthermore, PASTA domains of PrkC were found to bind PG in vitro with a clear preference for DAP-type to Lys-type muropeptides 11 driven by the Arg500 located in PASTA3. The most obvious hypothesis for the muropeptide-driven activation of PrkC would be that their binding to PASTA domains induces dimerization of the extracellular domain thus leading to the formation of the asymmetric active PrkC dimer 16 . Recently, the X-ray structure of the intracellular kinase domain of PknB suggests a model in which a structural and functionally asymmetric 'front-to-front' association occurs 21 . The activated autophosphorylated kinase domain can then mediate spore germination 19 by phosphorylating protein substrates like EF-G. To elaborate this model, the authors demonstrated that, in Bacillus spore preparation, EF-G phosphorylation is due to PrkC and to the addition of cell-free supernatants19. In another study, the same authors examined EF-G phosphorylation from cells grown to the exponential phase in the presence of PG fragments22. Surprisingly, they concluded that PrkC phosphorylates EF-G in response to PG fragments despite the presence of a band corresponding to muropeptide-dependent phosphorylation of EF-G in a ΔprkC mutant. This PrkC activation by muropeptides is challenged by other observations. In particular, the catalytic domain alone, without any PASTA motifs, is active in vitro 17,23 . Furthermore, a study of the oligomerization state of the extracellular domain of PrkC from Staphylococcus aureus, which strongly resembles that of B. subtilis, showed that it is monomeric and that muropeptides do not induce its dimerization 16 . The authors suggested that this dimerization mechanism may require the contribution of the TM domain and maybe indirectly modulated by muropeptides. In addition, whereas the PASTA module is required for the autophosphorylation of the kinase IreK from Enterococcus faecalis in response to cell wall stress, no direct muropeptide-induced activation of PrkC kinase activity has been observed 24 . In some cases, like for PknB from M. tuberculosis and PBP2x or StkP from S. pneumoniae, PASTA domains have been shown to be important for cell division and localization of the protein at mid-cell and at the poles 2,25 . In addition, it was recently shown for StkP from S. pneumoniae that the PASTA repeats are required for the activation of the kinase independently of muropeptides binding and also to control the septal cell wall thickness 26 . These observations suggest that PASTA domains could have several functions in proteins and are not limited to ligand-binding domains. Thus, the mode of activation of STPKs could be species-specific and more complex than the accepted model described so far.In this paper, we show that contrary to what was observed for the two homologues PknB or StkP, the septal localization of PrkC is independent of its PASTA domains but depends only on its TM domain in B. subtilis growing cells. Addition of PG fragments has no effect on this localization. Furthermore, we demonstrate that the deletion of one or all PASTA domains has no effect on PrkC activity in vitro or in vivo during exponential growth. In agreement with these data, whereas the protein is able to bind muropeptides, the kinase activity of PrkC is not stimulated by the addition of these PG fragments neither in vitro nor in vivo. Nevertheless, we show that the PASTA domains are necessary to stimulate PrkC autophosphorylation during the stationary growth phase, when PrkC is no longer concentrated at the septum of the cells but distributed all over the cell wall. All these results suggest that a complex mode of activation for the PrkC kinase activity exists in B. subtilis that depends on its cellular localization and is interconnected with bacterial growth phase. |
Results and Discussion
PASTA domains are not necessary for septal localization of PrkC. The extracellular domain has been shown to be required for PknB proper localization at mid-cell and at the poles in M. tuberculosis 25 , and for StkP localization at the septum in S. pneumoniae 2,27 . To test if the PASTA repeats are also required for PrkC localization at mid-cell and at the poles in B. subtilis growing cells 20 , we constructed several PrkC truncated proteins fused to GFP (Fig. 1). These proteins were deleted of one, two or three PASTA repeats as well as other deletions of the cytoplasmic domain or of the entire external domain. We analyzed their localization by fluorescence microscopy and noticed that all the truncated forms of PrkC were properly situated at the septum or at the poles of the cell. The only exception was the catalytic domain alone (GFP-PrkCc) that showed fluorescence throughout the cytoplasm of the bacteria (Fig. 1E). The deletion of one or two PASTA repeats or of all the external domain of PrkC had no effect on its localization (Fig. 1B,C,D). Even the deletion of the catalytic domain, alone or coupled with the deletion of the external domain, had no effect ( Fig. 1F and G), as long as the TM domain is present. Since one of the PASTA domain properties is its ability to bind muropeptide fragments of the cell wall, we prepared some PG fragments from an exponential growing cell culture of B. subtilis and tested their addition to the cell culture producing GFP-PrkC at the concentration range known to stimulate spore germination as previously described 19 . In agreement with the former observations, this supplement had no effect on the localization of the protein ( Fig. 1A and A'). The deletions of PASTA domains or their interaction with PG fragments have therefore no consequences on the localization of PrkC. All these data suggest that its septal and polar localization in B. subtilis cells is only mediated by the TM domain. This could be due to the TM domain itself or to its interactions with membrane proteins located at the division sites or at the poles like proteins of the divisome. Some of them may be involved in the localization of PrkC via an interaction of their transmembrane domains. We can already exclude the GpsB, EzrA and DivIVA cell division proteins whose deletion has no effect on PrkC localization 20 . Some proteins recycling the cell wall like hydrolases or PBPs 28,29 may be potential candidates.
The deletion of the PASTA domains has no effect on the kinase activity of PrkC in vitro. The catalytic domain of PrkC 30 alone possesses an efficient kinase activity in vitro 17,23,31 . We thus wanted to test if the deletion of the PASTA repeats could have an effect on the enzymatic activity of PrkC in vitro. For this purpose, we constructed and then purified some truncated forms of PrkC deleted of one or two PASTAs or of the entire extracellular domain (Fig. 2A). The production and purification yield was low depending on the extracellular region (Fig. 2B); however, we used these preparations to test the kinase activity of the corresponding proteins in vitro with radiolabeled ATP. Since GpsB has been shown to stimulate PrkC 20 , the experiments were also carried out in the presence of GpsB. We observed that the autophosphorylation of PrkC as well as its kinase activity were not significantly modified by the deletions of the PASTA domains (Fig. 2C, odd numbered lanes and Fig. S1). In all cases, the activity was stimulated by GpsB (Fig. 2C, even numbered lanes). These data clearly show that the The binding of muropeptides to PrkC doesn't modify its kinase activity in vitro. It has been shown by different biochemical approaches that PrkC PASTA repeats and homologues from other species, Stk1, PknB or StkP, are all able to bind muropeptides in vitro 10,11,15,19,25,32 . However, these studies were carried out with the extracellular domain alone, in the absence of the catalytic domain, and the effect of this binding on the kinase activity has never been tested so far in vitro. In addition, for PrkC from B. subtilis, a specific interaction of DAP-type-tetrapeptide was proposed with the PASTA3 by NMR 11 . To test the effect of muropeptide binding on the kinase activity of PrkC, we first checked by limited proteolysis the ability of our purified full-length PrkC protein to bind a purified PG fragments. The analysis of constituent muropeptides of the vegetative cell wall peptidoglycan of B. subtilis show that they are mostly composed of glycan strands ending with MurNAc units in the anhydro form and of peptide chains containing three or four amino acids with a clear preference for DAP-amidated-type 33 . We then decided to use the disaccharide tetrapeptide GlcNAc-MurNAc-L-Ala-γ-D-Glu-meso-DAP-D-Ala (or TCT) 34 in our tests (Fig. 3A). As purified muropeptides are usually used at the micromolar range in the previously cited biochemical studies, we decided to test TCT in a scale from 50 to 250 µM. We observed that the digestion profile of PrkC was modified by the addition of TCT suggesting a conformational change due to TCT binding to the protein. Indeed, we observed a decrease in the intensity of a specific protein band (see arrow) with the addition of increasing amounts of TCT ( Fig. 3A left gel). This observation could not be made with the PrkCc protein used as negative control (Fig. 3A right gel). These data confirmed that the binding of muropeptides to PrkC protein is dependent of its PASTA domains. This interaction was shown here for the first time by analyzing the entire protein and not only its extracellular domain. The amount of TCT necessary to visualize its binding to PrkC is in agreement with an affinity at the micromolar range for this muropeptide. Furthermore, we tested the effect of this binding on the kinase activity of the same preparation of PrkC using the same amounts of TCT. The catalytic domain PrkCc that is unable to bind the muropeptide was used as negative control. As shown in the autoradiogram, the binding of TCT to PrkC has no effect on its kinase activity in vitro (Fig. 3B). These observations were made in vitro but clearly run counter to the current activation model of PrkC and we decided to test it in vivo.
Addition of PG fragments to full-length PrkC induces its oligomerization. The current activation model of PrkC is based on the observation that B. subtilis spores of a prkC mutant are unable to germinate in response to PG fragments compared to a WT strain 19 , combined to biochemical data showing the interaction between the PASTA3 domain and muropeptides in vitro 11 . However, a clear evidence of a direct muropeptide activation of PrkC in vivo is still missing. We therefore decided to measure the autophosphorylation of PrkC full-length or of truncated forms of PrkC in vivo from cells cultivated in the absence and then in the presence of increasing concentrations of PG fragments. Being limited in the amount of TCT available, we decided to use PG fragments prepared from a B. subtilis cell culture stopped at the exponential growth phase and at the concentration range known to stimulate spore germination as previously described 19 . In order to make sure that our PG preparation was containing enough muropeptides able to interact with PrkC, we checked this binding by Dynamic Light Scattering (DLS). We also included the mutant protein PrkC(R500A) as a negative control in the experiment since this mutation, located in the PASTA3, was shown to abolish PG fragments binding. The effect of the increasing amount of PG fragments on the hydrodynamic size of PrkC, PrkC(R500A) and PrkCc respectively was determined by measuring the intensity of the light diffused by the molecules and their translational speed in solution as presented in the correlograms ( PG. However, the analysis of correlograms, Z-averages ( Fig. 4B) and diameters by intensity distribution median (Di50) (Fig. S2) suggested a difference between the proteins. All three showed differences in their correlograms in the exponential decay and fluctuating times (Fig. 4A). When PG fragments were added to PrkC, we observed a concentration-dependent increase of the fluctuation time and the broadening of the decay was slow showing a progressive increase in polydispersity suggesting a specific binding of PG fragments to PrkC leading to the oligomerization of the protein. When PG fragments were added to PrkC(R500A), the concentration-dependent increase of the fluctuation time was slower and the broadening of the decay was narrower showing that specific binding of PG fragments to PrkC(R500A) was less efficient and consequently the oligomerization too. Conversely, for the catalytic domain, the addition of PG fragments increased the time at which the correlation begins to decay with a broadening of the fluctuation time suggesting an aggregation of PrkCc by PG fragments and high polydispersity thus a nonspecific binding. These results were confirmed by the Di50 (Fig. S2) and Z-average values (Fig. 4B) that increased constantly and to less than 100 nm with increasing concentrations of PG fragments for PrkC. However, for PrkCc, the Z-average increased beyond 100 nm in the presence of 0.15 µg/ml of PG fragments and continued to increase at 1.5 µg/ml. Small variations of the Z-average values (Fig. 4B) and no variation of Di50 values (Fig. S2) for PrkC(R500A) confirmed that PG fragments binding was impaired on this protein. We also measured the denaturation temperatures for both proteins with or without PG fragments (data not shown). The denaturation temperature of PrkC was identical with or without PG fragments (50 °C) suggesting a good stability of the protein that was not modified by muropeptides binding. On the contrary, the denaturation temperature of PrkCc dropped from 70 °C to 50 °C with the addition of the PG fragments confirming a destabilizing effect of muropeptides on the catalytic domain. Altogether, these results suggest that PG fragments interact specifically with PrkC to induce its oligomerization whereas it interacts non-specifically with PrkCc to induce its aggregation. Deletion of PASTA domains or addition of PG fragments has no effect on PrkC activity during exponential phase. Since PG fragments bind to PASTA domains, we first analyzed the effect of PASTA deletions on PrkC activity in B. subtilis growing cells. For this purpose, strains expressing the truncated-PrkC-GFP proteins were grown in a rich medium until the mid-exponential phase (OD 600 = 0.8) and crude extracts were prepared and analyzed by western blots. Using antibodies against the GFP protein, we first checked that all the forms of PrkC were produced at the same level in the cell (Fig. 5A). We then measured the autophosphorylation of PrkC in vivo using antibodies against phospho-threonine (P-Thr). We observed that all the forms of PrkC were phosphorylated except the extracellular domain of PrkC (GFP-TM-P1P2-Ig-like) lacking the catalytic intracellular kinase domain that served as the negative control. These data clearly show that all the forms of PrkC containing the catalytic domain are active. However, the absence of the PASTA domains has no effect on PrkC autophophorylation and therefore on its kinase activity in vivo. This observation has also been made recently for the homologous protein IreK from E. faecalis but to a lesser extent 24 . Indeed, a truncated form of IreK lacking its five PASTA repeats was still active indicating that the extracellular domain of IreK is not required for an answer to a signal associated with growth and/or cell division. However, the specific stimulation of IreK kinase activity in response to cell-wall antimicrobials seemed to be dependent of the PASTA module, which suggests multiple parameters for sensory input in vivo 24 .
Since our preparation of PG fragments contains muropeptides able to bind to PrkC, we decided to test it on PrkC autophosphorylation in vivo. For this, strains producing GFP-PrkC or GFP-PrkCc as negative control were grown in a rich medium in the presence of increasing amount of PG fragments until the mid-exponential phase (OD 600 = 0.8). Then crude extracts were prepared and analyzed by western blots. Using antibodies against PrkC, we observed that both proteins were produced at the same level whatever the amount of PG fragments added (Fig. 5B). In addition, the phosphorylation signal detected in all lanes with antibodies against P-Thr showed that the level of PrkC autophosphorylation was similar (Fig. 5B) PASTA domains are necessary for PrkC activation during stationary phase growth. Since we did not detect any effect of PASTAs deletions or addition of PG fragments during exponential phase, we decided to investigate the localization and the activity of the protein in stationary phase cells. We first analyzed the localization by fluorescence microscopy of GFP-PrkC as well as of the truncated forms of PrkC deleted of one or several PASTA repeats. Unexpectedly, we noticed that all the forms of PrkC were distributed all over the cell wall (Fig. 6A). These observations revealed, for the first time, that the localization of PrkC varies according to the growth phase (Fig. S3). However, the PASTA domains are not necessary for this new positioning of the kinase. Thus, PrkC is concentrated at the septum and at the poles during cell division and delocalizes throughout the cell wall when the cells enter into a non-dividing state, but in both cases, the external domain is not required for PrkC cellular localization. We then wanted to test if a role of the PASTA domains would be to stimulate the kinase activity by autophosphorylation in non-dividing cells. We thus prepared crude extracts from stationary phase cultures producing the PASTA-truncated forms of GFP-PrkC or the mutant protein GFP-PrkC(R500A) unable to bind PG fragments and to oligomerize. These crude extracts were then analyzed by western blots using antibodies against the GFP protein to check that all the forms of PrkC were produced at the same level in the cell and using antibodies against P-Thr to measure the autophosphorylation of PrkC in vivo ( Fig. 6B and C). Whereas all forms of PrkC were expressed at the same level, only the entire protein was still detected by the antibodies against P-Thr. The removal of the PASTA3 or the mutation of the Arg500 to Ala, known to interact with PG fragments, was were grown on LB medium with 0.5% xylose at 37 °C until OD 600 = 0.8. After centrifugation, the pellets were resuspended in 1/100 th volume of lysis buffer and treated as described in Materials and Methods. For each strain, 16 μl of crude extract were separated by SDS-PAGE. After blotting, phosphorylated PrkC was detected using antibodies directed against P-Thr residues. To estimate the relative quantity of PrkC in crude extracts, we used anti-GFP antibodies. (B) Strains SG278 (ΔprkC, amyE::gfp-prkC) and SG465 (ΔprkC, amyE::gfp-prkCc-TM) were grown on LB medium with 0.5% xylose and increasing amounts of PG fragments (0, 0.003, 0.015, 0.03, 0.3 and 3 µg/ml) at 37 °C until OD 600 = 0.8. After centrifugation, the pellets were resuspended in 1/100 th volume of lysis buffer and treated as described in Materials and Methods. For each strain, 16 μl of crude extract were separated by SDS-PAGE. After blotting, phosphorylated PrkC was detected using antibodies directed against P-Thr residues. To estimate the relative quantity of PrkC in crude extracts, we used a specific antibody against PrkC. Full-length blots are presented in the supplemental data. sufficient to lose the phosphorylation signal. These results clearly show that, during stationary phase growth, the binding of PG fragments to the extracellular domain of PrkC is required to allow the autophosphorylation of the protein and therefore to stimulate its kinase activity.
A sophisticated model for kinase activation of PrkC. Our data suggest that PrkC regulation is a complex mechanism that may vary depending on the physiological state of the cell, i.e. growing cells versus non-dividing cells (stationary phase cells or spores) and according to the ligand and the partners of the protein when it is involved in one cellular process or another. We therefore propose a new model for the modulation of PrkC kinase activity depending on its cellular localization, the growth phase and the cellular process regulated (Fig. 7). The current model described for germination conditions and which can also be proposed for stationary phase conditions is summarized in (Fig. 7 top panel) and the designed regulatory model for PrkC kinase activity during exponential growth is presented in (Fig. 7 lower panel). During stationary phase (or germination), PrkC is located all around the cell wall (or the spore membrane), PG fragments are available, and the cells (or spores) probably need to sense an environmental signal to ensure the best rate of cell survival (or induce the exit from dormancy). Thus, stimulation by PG fragments through the PASTA domains of the protein may be required to induce PrkC dimerization and thus kinase activation via its autophosphorylation. This layout could be similar in other sporulating bacteria in which a PASTA-containing protein kinase is involved in spore germination. During growth, PrkC is concentrated at mid-cell or at the poles and, in such conditions, it likely has no access to the extracellular medium and thus to free PG fragments. Actually, no stimulation of its kinase activity by addition of PG fragments has been detected in vivo but it is stimulated by interaction with the division protein GpsB 20 . Moreover, we did not detect any stimulation of the kinase activity by TCT in vitro, although it binds to PrkC. This could be explained by the strong probability for two protein molecules to be in contact in solution before the addition of TCT and to phosphorylate each other. A high percentage of the PrkC molecules are therefore already active. In vivo, ligands like lipid II or other periplasmic molecules may play a role in PrkC dimerization that can also be mediated by its recruitment, via its TM domain, by partners located at the septum and/or at the poles like proteins of the division machinery, PBPs and hydrolases or other membrane associated proteins. During cell division, PrkC molecules are thus focused at the poles and septa where they can phosphorylate each other to become active. Furthermore, GpsB and to a lesser extent EzrA and DivIVA, increase PrkC kinase activity via a yet unknown mechanism. In these conditions, the stimulation by PG fragments may not be necessary. Our results are consistent with the regulation observed in E. faecalis cells, where IreK can respond to cell wall stress by enhancing its kinase activity via its PASTA repeats and can also respond to signal associated with growth and/ or division independently of the presence of its extracellular PASTA-containing domain 24 . We can conclude that PASTA-kinases are subtly stimulated according to their cellular localization and the cellular processes they regulate. This fine-tune regulation may also differ between species.
Methods
Plasmids and strains constructions. Standard procedures for molecular cloning and cell transformation of B. subtilis and E. coli were used. All the strains and plasmids used in this study are listed in Table 1. Primers The scale bar for microscopy images represents 2 µm. (B) PrkC-phosphorylation analysis by western blots. The same strains SG278, SG467, SG466 and SG465 were grown on LB medium with 0.5% xylose at 37 °C for 23 hours (final OD 600~ 6). After centrifugation, the pellets were resuspended in 1/30 th volume of lysis buffer and treated as described in Materials and Methods. For each strain, 16 μl of crude extract were separated by SDS-PAGE. After blotting, phosphorylated PrkC was detected using antibodies directed against P-Thr residues. To estimate the relative quantity of PrkC in crude extracts, we used anti-GFP antibodies. (C) PrkC(R500A)-phosphorylation analysis by western blots. The strains SG278 and SG622 were grown on LB medium with 0.5% xylose at 37 °C for 23 hours (final OD 600~6 ) and the culture pellets were treated as mentioned in (B). Full-length blots are presented in the supplemental data. used in this study are available upon request. Sequencing of PCR-derived DNA fragments in the plasmid constructs was carried out by GATC-Biotech to ensure error-free amplification.
For the generation of fluorescent fusion proteins, the truncated versions of the prkC gene were amplified by PCR using specific primers allowing its insertion between ApaI and XhoI sites in pSG1729 35 . The B. subtilis strain 1A963 17 was then transformed with pSG1729-gfp-prkC-(truncated versions) or pSG1729-gfp-prkC(R500A) generating the strains SG355, SG465, SG466, SG467, SG497, SG498 and SG622. Protein expression was induced with 0.5% xylose (w/v).
The truncated or mutated versions of PrkC were overexpressed in E. coli, with the corresponding genes amplified by PCR using B. subtilis 168 genomic DNA as a template and a primer pair containing SacI and PstI restriction sites. The amplified products were digested with SacI and PstI and then ligated to the pETDuet vector. The resulting plasmids are listed in Table 1.
PG preparation and purification of TCT muropeptide. B. subtilis PG fragments from growing cells were prepared as previously described in 19 . The pellet containing the cell wall PG freed of proteins and lipoteichoic acids was quantified by weighing then resuspended and digested with mutanolysin (10 µg/ml) overnight at 37 °C prior to inactivation of the enzyme at 80 °C for 20 min. The concentration of PG fragments was determined by quantitative aminoacid (diaminopimelic acid) and aminosugar (muramic acid, glucosamine) analysis with a Hitachi L8800 analyzer (ScienceTec, Les Ulis, France) after hydrolysis of samples in 6 M HCl at 95 °C for 16 h. PG fragments were then used in the several tests. TCT muropeptide was produced and purified as described in 36 . mean size of the sample, smaller samples fluctuate quicker than larger samples is solution. The steeper the exponential decay, the more monodisperse (single population) the sample, and if the decay is extended the greater the sample polydispersity (several populations). Size distribution assays were performed at 25 °C. For each assay three measurements were performed; each one consisting in 10-15 runs of 10 seconds. The scattering angle was 173°. Temperature trend assay to calculate aggregation points contained a sequence from 20 to 70 °C with 10 °C intervals. We displayed our results using the correlograms, Z-average (mean intensity size of sample) and Di50 (diameter by intensity of 50% of the molecules in solution) using the Zetaziser software 7.12. PrkC and PrkC(R500A) were prepared at 0.2 mg/ml in 20 mM Tris-HCl pH 7.5, 200 mM NaCl, 7% glycerol following centrifugation for 15 min at 14000 rpm at 6 °C. PrkCc was prepared at 0.1 mg/ml in 20 mM Tris-HCl pH 7.5, 200 mM NaCl, 7% glycerol following centrifugation for 15 min at 14000 rpm at 6 °C. The proteins were analyzed in the absence or presence of increasing concentrations of PG fragments from 0.15-1.6 µg/ml.
Dynamic Light
Microscopy.
Strains were grown on LB medium at 37 °C. The gfp-prkC gene fusion and all truncated versions of prkC were expressed from the inducible P xyl promoter in the presence of 0.5% xylose. The PrkC localization was analyzed by fluorescent microscopy on a Zeiss Upright Axio Imager M2 microscope as described previously 3 .
Western Blot. The cells were grown at 37 °C in 30 ml of LB medium to OD 600 = 0.8 for exponential phase extracts and to OD 600~6 for stationary phase extracts (23-hour cultures) then centrifuged for 10 min at 8000 rpm at 4 °C. When needed, the exponential phase cultures were realized in the presence of increasing amounts of PG fragments (0, 0.003, 0.015, 0.03, 0.3 and 3 µg/ml). Cell pellets were resuspended in 1/100 th and 1/30 th volumes of lysis buffer for exponential and stationary phase cultures, respectively, containing 10 mM Tris-HCl pH 8.0, 150 mM NaCl, 0.1% NP40, 1 mM PMSF, 1 mM DTT, 25 U.ml −1 benzonase and 10 mg.ml −1 lysozyme, and incubated for 30 min at 37 °C. 1/10 th volume of 10% SDS and 1/2 volume of (2×) Laemmli buffer were added to the extracts that were heated at 100 °C for 10 min. Samples were run on a 10% or 12.5% SDS-PAGE and transferred to hybond-ECL membrane by electroblotting. The membrane was blocked with PBS solution containing 5% milk powder (w/v), for 3 hours at room temperature with shaking, then incubated with anti-GFP or anti-PrkC antibodies diluted to 1/10000 th or 1/1000 th , respectively, overnight at 4 °C. After three washes, the secondary antibody, a peroxidase-conjugated Goat anti-Rabbit (DAKO) antibody, was used at 1/10000 th dilution for one hour. After three washes, the membrane was incubated with ECL reagents (Perkinelmer) and scanned for chimioluminescence with an ImageQuant LAS4000 (GE Healthcare). A second membrane was used for anti-P-Thr antibodies as previously described in 20 . Protein purification. Plasmids overproducing 6His-tagged PrkC truncated proteins were used to transform E. coli C41(DE3). Purification of 6His-tagged recombinant proteins was performed with Ni 2+ -NTA resin (Qiagen) as previously described in 18 for PrkCc, the PASTA-truncated forms of PrkC, PrkC and PrkC(R500A). Before purification, in order to solubilize the proteins containing a TM domain, 0.4% Triton X100 was added to the crude extracts, shacked for 1 h at 4 °C then centrifuged at 35000 rpm for 1 h at 4 °C to removed membrane fragments. In addition, the buffer used for the purification steps of these proteins contained 0.2% Triton X100.
Protein phosphorylation. 2 μg of GpsB were incubated for 15 min at 37 °C with 2.5 μg of the several forms of PrkC protein in a 15 μl reaction mixture containing 10 mM HEPES, pH 8.0, 1 mM MgCl 2 , 2 μg of MBP (Myelin Basic Protein) that was shown to be phosphorylated by PrkC 18 and 1 mM [γ-33 P] ATP (1 μCi). The phosphorylation reaction was stopped by adding 5× SDS-sample buffer to the reaction mixtures before SDS-PAGE analysis. Gels were then dried and exposed to autoradiography. When muropeptides were tested, increasing amounts (from 0 to 250 µM) of TCT were added in the reaction mixture containing 2.5 μg of the PrkC or PrkCc protein, 10 mM HEPES, pH 8.0, 1 mM MgCl 2 , 2 μg of MBP and 1 mM [γ-33 P] ATP (1 μCi).
Limited proteolysis.
For each 20 μl sample, 3 μg of PrkC or PrkCc proteins were pre-incubated for 10 min at 37 °C with 40 mM NaCl, 1 mM MgCl 2 , 10 mM Tris-HCl, pH 8.0 in the absence or presence of increasing amounts of TCT muropeptide (50, 100, 150 and 250 µM). After addition of 0.01 μg of trypsin (Promega), the reaction mixture was incubated for 10 min at 37 °C. The digestion was stopped by adding an equal volume of electrophoresis loading buffer to the assay mixtures and by heating 5 min at 100 °C before applying the samples onto a 12.5% or 15% SDS-PAGE. The gels were colored with Coomassie blue then scanned.
Data and materials availability. Data and materials will be made available upon request.
Scientific
REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2 length
Figure 1 .
1Localization of full-length and truncated GFP-PrkC in B. subtilis. 3D representation of GFP-PrkC fusion proteins, with A to G letters and dashed lines indicating the length of the protein. PrkC molecular graphic was modeled with the UCSF Chimera package (supported by NIGMS P41-GM103311) from the 3PY9 PDB structure for the extracellular domain and 4EQM PDB structure for the intracellular domain. Strains were grown on LB medium at 37 °C and all the forms of GFP-PrkC proteins were expressed from the P xyl promoter in the presence of 0.5% xylose and with 3 µg/ml of PG fragments for the full-length protein. PrkC localization was analyzed by fluorescent microscopy for strains: A: SG278 (ΔprkC, amyE::gfp-prkC), A': SG278 in the presence of PG fragments, B: SG467 (ΔprkC, amyE::gfp-prkCc-TM-P1P2), C: SG466 (ΔprkC, amyE::gfp-prkCc-TM-P1), D: SG465 (ΔprkC, amyE::gfp-prkCc-TM), E: SG355 (ΔprkC, amyE::gfp-prkCc), F: SG497 (ΔprkC, amyE::gfp-TM-P1P2-Ig-like) and G: SG498 (ΔprkC, amyE::gfp-TM). The scale bar for microscopy images represents 2 µm. deletion of any component of the external sensing domain do not significantly affect the kinase activity of PrkC in vitro in the absence of muropeptides or other potential enhancer/germinant molecules.
Figure 2 .
2Kinase activity of full-length and truncated PrkC in vitro. (A) 3D representation of PrkC protein with arrows indicating the different truncation sites. (B) Each recombinant PrkC protein was purified and the preparations were visualized on SDS-PAGE gel colored with Coomassie blue. The quantity of purified protein loaded on the gel corresponds to the amount of PrkC protein used in the enzymatic activity test. (C) In vitro phosphorylation assays in the absence or presence of GpsB for PrkC or the truncated forms of PrkC. The recombinant PrkC proteins were incubated with [γ-33 P]ATP, MBP and GpsB (lanes 2, 4, 6 and 8) or without GpsB (lanes 1, 3, 5 and 7) at 37 °C during 15 min. The tests were realized in the presence of PrkCc-TM (4.2 µM) (lanes 1 and 2), PrkCc-TM-P1 (2.6 µM) (lanes 3 and 4), PrkCc-TM-P1P2 (1.6 µM) (lanes 5 and 6), or PrkC (0.6 µM) (lanes 7 and 8). Samples were separated by SDS-PAGE and visualized by autoradiography. The radioactive signals seem to decrease with the length of the protein but these differences are due to the lower amounts of protein used in the tests which depend on their concentration after their purification. Full-length gels are presented in the supplemental data. Scientific REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
Fig. 4A). The results showed that PrkC, PrkC(R500A) and PrkCc had hydrodynamic diameters of D h = 8.23 nm, D h = 8.60 nm and D h = 4.96 nm, respectively, by volume distribution median (Dv50) in the absence of PG fragments(Fig. 4A insets)suggesting elongated monomers for PrkC and PrkC(R500A) and a globular monomer for PrkCc. In the presence of 1 µg/ml of PG fragments, PrkC had a D h of 9.20 nm, PrkC(R500A) had a D h of 8.20 nm and PrkCc a D h of 8.40 nm suggesting an oligomerization by
Figure 3 .
3Muropeptides binding to PrkC and its effect on kinase activity in vitro. (A) Coomassie-stained SDS-PAGE of partial proteolysis profile of the full-length PrkC (left) or its catalytic domain, PrkCc, used as negative control (right). 3 µg of PrkC and PrkCc were incubated with trypsin (Promega) in the absence or presence of increasing amounts of TCT (0, 50, 100, 150 and 250 µM) for 10 min at 37 °C. The digestion profiles were assessed by electrophoresis in SDS-PAGE. For full-length PrkC (left gel), the arrow indicates a band whose intensity decreases in the presence of increasing amounts of TCT. The area where the pattern of digestion is modified by the addition of TCT is framed and magnified under the full-length gel. (B) In vitro phosphorylation assays in the presence of PrkC or PrkCc. 2.5 µg of protein were incubated with [γ-33 P]ATP and MBP and increasing amounts of TCT (0, 100, 150 and 250 µM) at 37 °C during 15 min. Samples were separated by SDS-PAGE and visualized by autoradiography. Full-length gels are presented in the supplemental data. Scientific REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
Figure 4 .
4PrkC binds PG. Oligomerization of PrkC, PrkC(R500A) and PrkCc in the presence of increasing concentrations of PG fragments. (A) Correlograms displaying raw data of time dependent diffusion of 3 µM PrkC proteins analyzed with increasing concentrations of PG fragments from 0 to 1.6 µg/ml. The insets represent the size distribution by size of PrkC, PrkC(R500A) or PrkCc delta PG mean size. For PrkC and PrkC(R500A), the values of 8.23 and 8.6 hydrodynamic diameters respectively suggests elongated monomers and for PrkCc the value of 4.96 hydrodynamic diameter suggests a globular monomer. Broken blue lines indicate the start of the exponential decay without PG fragments. (B) Histogram of PrkC (light grey), PrkCc (medium grey) and PrkC(R500A) (white) Z-average values (mean intensity size) in the presence of increasing concentrations of PG fragments from 0 to 1.6 µg/ml. Z-average gradually increases suggesting an oligomerization effect of PG fragments on PrkC but a lower effect on oligomerization of PrkC(R500A) and infers a non-specific aggregation of PrkCc with PG. Z-average displayed on a logarithmic scale. Scientific REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
Figure 5 .
5The kinase activity of PrkC in vivo is not modified by PASTAs deletions or PG binding during exponential growth. (A) PrkC-phosphorylation analysis by western blots. Strains SG278 (ΔprkC, amyE::gfp-prkC), SG467 (ΔprkC, amyE::gfp-prkCc-TM-P1P2), SG466 (ΔprkC, amyE::gfp-prkCc-TM-P1), SG465 (ΔprkC, amyE::gfp-prkCc-TM) and SG497 (ΔprkC, amyE::gfp-TM-P1P2-Ig-like)
Scientific
REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
Figure 6 .
6Localization of PrkC during stationary phase growth and role of the PASTA domains. (A) PrkC localization during stationary phase growth. Strains were grown on LB medium at 37 °C during 23 hours and all the forms of GFP-PrkC proteins were expressed from the P xyl promoter in the presence of 0.5% xylose. PrkC localization was analyzed by fluorescent microscopy for strains SG278 (ΔprkC, amyE::gfp-prkC), SG467 (ΔprkC, amyE::gfp-prkCc-TM-P1P2), SG466 (ΔprkC, amyE::gfp-prkCc-TM-P1) and SG465 (ΔprkC, amyE::gfp-prkCc-TM).
Scientific
REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
Scattering. Dynamic light scattering (DLS) experiments were carried out to determine the hydrodynamic diameter of PrkC, PrkC(R500A) and PrkCc in the presence and absence of PG using a Zetasizer Nano ZS (Malvern Instruments). Particles in solution are in a constant random motion and the intensity of the scattered light fluctuates with time. To determine the particle size, the provided software uses the Stokes-Einstein relation to obtain the intensity averaged size distribution from the raw correlation data. The correlograms give several information about the sample. The time at which the correlation starts to decay is an indication of the
Figure 7 .
7Two activation modes for PrkC. Two activation modes are proposed for PrkC depending on the physiological state of the bacteria. On the top panel (in blue), we designed the model of activation during stationary phase growth or germination of B. subtilis spores. During stationary phase or before germination, PrkC is distributed all over the cell wall of the bacteria or in the internal membrane of the spore. The binding of muropeptides (germination signal for spores) stimulates PrkC dimerization and autophosphorylation. The activated PrkC can then phosphorylate its cytoplasmic substrates. On the panel below (in red), we designed the model of PrkC activation during bacterial growth. Thanks to interactions with membrane proteins at the poles and at the septum, like hydrolases or proteins of the divisome schematically represented by the white shadow, PrkC molecules get closer to each other. PrkC interacts also with the division protein GpsB which stimulates its autophosphorylation and its kinase activity. The activated PrkC is then able to phosphorylate its cytoplasmic substrates. The feedback loop regulation of PrkC activity by phosphorylated GpsB protein 20 is not described here. The divisome schematically represented by the white shadow includes the proteins described in37 and containing EzrA, PBP1, PBP2b, ZapA, SepF, FtsZ, FtsA, FtsL, FtsW, DivIB, DivIC, and DivIVA. Scientific REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
regardless of the form of the protein. This result indicates that PrkC kinase activity is not stimulated in vivo by PG binding to the PASTA repeats during exponential growth.
Scientific REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2Strain/plasmid Relevant characteristics
Source/reference
B. subtilis strains
WT168
trpC2
lab collection
1A963
trpC2 prkC∆1
17
SG278
trpC2 prkC∆1, amyE::gfp-prkC
20
SG355
trpC2 prkC∆1, amyE::gfp-prkCc
This work
SG465
trpC2 prkC∆1, amyE::gfp-prkCc-TM
This work
SG466
trpC2 prkC∆1, amyE::gfp-prkCc-TM-P1
This work
SG467
trpC2 prkC∆1, amyE::gfp-prkCc-TM-P1P2
This work
SG497
trpC2 prkC∆1, amyE::gfp-TM-P1P2P3-Ig-like This work
SG498
trpC2 prkC∆1, amyE::gfp-TM
This work
SG622
trpC2 prkC∆1, amyE::gfp-prkC(R500A)
This work
© The Author(s) 2018
AcknowledgementsWe thank J.R. Fantino for drawings with Adobe Illustrator and C. Grangeasse for stimulating discussions. This research was supported by the CNRS, the ANR (PiBaKi) and Aix Marseille Univ.Author ContributionsAdditional InformationSupplementary information accompanies this paper at https://doi.org/10.1038/s41598-018-20145-2.Competing Interests: The authors declare that they have no competing interests.Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.Open Access This article is licensed under a Creative Commons Attribution 4.0 InternationalLicense, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.
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Serine/Threonine Protein Kinases from Bacteria, Archaea and Eukarya Share a Common Evolutionary Origin Deeply Rooted in the Tree of Life. I A Stancik, 10.1016/j.jmb.2017.11.004J Mol Biol. Stancik, I. A. et al. Serine/Threonine Protein Kinases from Bacteria, Archaea and Eukarya Share a Common Evolutionary Origin Deeply Rooted in the Tree of Life. J Mol Biol. https://doi.org/10.1016/j.jmb.2017.11.004 (2017).
Substrate specificity of bacterial DD-peptidases (penicillin-binding proteins). R F Pratt, 10.1007/s00018-008-7591-7s00018-008-7591-7Cell Mol Life Sci. 65Pratt, R. F. Substrate specificity of bacterial DD-peptidases (penicillin-binding proteins). Cell Mol Life Sci 65, 2138-2155, https://doi. org/10.1007/s00018-008-7591-7 (2008).
Recognition of peptidoglycan and β-lactam antibiotics by the extracellular domain of the Ser/Thr protein kinase StkP from Streptococcus pneumoniae. B Maestro, 10.1016/j.febslet.2010.12.016FEBS Lett. 585Maestro, B. et al. Recognition of peptidoglycan and β-lactam antibiotics by the extracellular domain of the Ser/Thr protein kinase StkP from Streptococcus pneumoniae. FEBS Lett 585, 357-363, https://doi.org/10.1016/j.febslet.2010.12.016 (2011).
Chemical basis of peptidoglycan discrimination by PrkC, a key kinase involved in bacterial resuscitation from dormancy. F Squeglia, 10.1021/ja208080rJ Am Chem Soc. 133Squeglia, F. et al. Chemical basis of peptidoglycan discrimination by PrkC, a key kinase involved in bacterial resuscitation from dormancy. J Am Chem Soc 133, 20676-20679, https://doi.org/10.1021/ja208080r (2011).
The cell wall precursor lipid II acts as a molecular signal for the Ser/Thr kinase PknB of Staphylococcus aureus. P Hardt, 10.1016/j.ijmm.2016.12.001Int J Med Microbiol. 307Hardt, P. et al. The cell wall precursor lipid II acts as a molecular signal for the Ser/Thr kinase PknB of Staphylococcus aureus. Int J Med Microbiol 307, 1-10, https://doi.org/10.1016/j.ijmm.2016.12.001 (2017).
The structure of PknB extracellular PASTA domain from Mycobacterium tuberculosis suggests a ligand-dependent kinase activation. P Barthe, G V Mukamolova, C Roumestand, M Cohen-Gonsaud, 10.1016/j.str.2010.02.013Structure. 18Barthe, P., Mukamolova, G. V., Roumestand, C. & Cohen-Gonsaud, M. The structure of PknB extracellular PASTA domain from Mycobacterium tuberculosis suggests a ligand-dependent kinase activation. Structure 18, 606-615, https://doi.org/10.1016/j. str.2010.02.013 (2010).
Role of eukaryotic-like serine/threonine kinases in bacterial cell division and morphogenesis. S Manuse, A Fleurie, L Zucchini, C Lesterlin, C Grangeasse, 10.1093/femsre/fuv041FEMS Microbiol Rev. Manuse, S., Fleurie, A., Zucchini, L., Lesterlin, C. & Grangeasse, C. Role of eukaryotic-like serine/threonine kinases in bacterial cell division and morphogenesis. FEMS Microbiol Rev. https://doi.org/10.1093/femsre/fuv041 (2015).
The extended conformation of the 2.9-Å crystal structure of the three-PASTA domain of a Ser/Thr kinase from the human pathogen Staphylococcus aureus. P Paracuellos, 10.1016/j.jmb.2010.10.012J Mol Biol. 404Paracuellos, P. et al. The extended conformation of the 2.9-Å crystal structure of the three-PASTA domain of a Ser/Thr kinase from the human pathogen Staphylococcus aureus. J Mol Biol 404, 847-858, https://doi.org/10.1016/j.jmb.2010.10.012 (2010).
X-ray structural studies of the entire extracellular region of the serine/threonine kinase PrkC from Staphylococcus aureus. A Ruggiero, 10.1042/BJ20101643Biochem J. 435Ruggiero, A. et al. X-ray structural studies of the entire extracellular region of the serine/threonine kinase PrkC from Staphylococcus aureus. Biochem J 435, 33-41, https://doi.org/10.1042/BJ20101643 (2011).
The PrpC serine-threonine phosphatase and PrkC kinase have opposing physiological roles in stationary-phase Bacillus subtilis cells. T A Gaidenko, T J Kim, C W Price, J Bacteriol. 184Gaidenko, T. A., Kim, T. J. & Price, C. W. The PrpC serine-threonine phosphatase and PrkC kinase have opposing physiological roles in stationary-phase Bacillus subtilis cells. J Bacteriol 184, 6109-6114 (2002).
Characterization of a membrane-linked Ser/Thr protein kinase in Bacillus subtilis. E Madec, A Laszkiewicz, A Iwanicki, M Obuchowski, S Seror, Mol Microbiol. 463178implicated in developmental processesMadec, E., Laszkiewicz, A., Iwanicki, A., Obuchowski, M. & Seror, S. Characterization of a membrane-linked Ser/Thr protein kinase in Bacillus subtilis, implicated in developmental processes. Mol Microbiol 46, 571-586, 3178 (2002).
A eukaryotic-like Ser/Thr kinase signals bacteria to exit dormancy in response to peptidoglycan fragments. I M Shah, M H Laaberki, D L Popham, J Dworkin, 10.1016/j.cell.2008.08.039S0092-8674(08)01128-8Cell. 135Shah, I. M., Laaberki, M. H., Popham, D. L. & Dworkin, J. A eukaryotic-like Ser/Thr kinase signals bacteria to exit dormancy in response to peptidoglycan fragments. Cell 135, 486-496, S0092-8674(08)01128-8, https://doi.org/10.1016/j.cell.2008.08.039 (2008).
Phosphorylation of the cell division protein GpsB regulates PrkC kinase activity through a negative feedback loop in Bacillus subtilis. F Pompeo, E Foulquier, B Serrano, C Grangeasse, A Galinier, 10.1111/mmi.13015Mol Microbiol. 97Pompeo, F., Foulquier, E., Serrano, B., Grangeasse, C. & Galinier, A. Phosphorylation of the cell division protein GpsB regulates PrkC kinase activity through a negative feedback loop in Bacillus subtilis. Mol Microbiol 97, 139-150, https://doi.org/10.1111/ mmi.13015 (2015).
Structural and Genetic Analyses of the Mycobacterium tuberculosis Protein Kinase B Sensor Domain Identify a Potential Ligand-binding Site. D M Prigozhin, 10.1074/jbc.M116.731760J Biol Chem. 291Prigozhin, D. M. et al. Structural and Genetic Analyses of the Mycobacterium tuberculosis Protein Kinase B Sensor Domain Identify a Potential Ligand-binding Site. J Biol Chem 291, 22961-22969, https://doi.org/10.1074/jbc.M116.731760 (2016).
Induction and regulation of a secreted peptidoglycan hydrolase by a membrane Ser/Thr kinase that detects muropeptides. I M Shah, J Dworkin, 10.1111/j.1365-2958.2010.07046.xMol Microbiol. 75Shah, I. M. & Dworkin, J. Induction and regulation of a secreted peptidoglycan hydrolase by a membrane Ser/Thr kinase that detects muropeptides. Mol Microbiol 75, 1232-1243, https://doi.org/10.1111/j.1365-2958.2010.07046.x (2010).
EF-Tu and the stressosome protein YezB are substrates of the Ser/Thr kinase/phosphatase couple, PrkC/ PrpC, in Bacillus subtilis. C Absalon, 10.1099/mic.0.022475-0Microbiology. 155Absalon, C. et al. CpgA, EF-Tu and the stressosome protein YezB are substrates of the Ser/Thr kinase/phosphatase couple, PrkC/ PrpC, in Bacillus subtilis. Microbiology 155, 932-943, https://doi.org/10.1099/mic.0.022475-0 (2009).
Growth-and stress-induced PASTA kinase phosphorylation in Enterococcus faecalis. B D Labbe, C J Kristich, 10.1128/JB.00363-17J Bacteriol. Labbe, B. D. & Kristich, C. J. Growth-and stress-induced PASTA kinase phosphorylation in Enterococcus faecalis. J Bacteriol, https:// doi.org/10.1128/JB.00363-17 (2017).
The extracytoplasmic domain of the Mycobacterium tuberculosis Ser/Thr kinase PknB binds specific muropeptides and is required for PknB localization. M Mir, 10.1371/journal.ppat.1002182PLoS Pathog. 7Mir, M. et al. The extracytoplasmic domain of the Mycobacterium tuberculosis Ser/Thr kinase PknB binds specific muropeptides and is required for PknB localization. PLoS Pathog 7, e1002182, https://doi.org/10.1371/journal.ppat.1002182 (2011).
PASTA repeats of the protein kinase StkP interconnect cell constriction and separation of Streptococcus pneumoniae. L Zucchini, 10.1038/s41564-017-0069-3Nat Microbiol. Zucchini, L. et al. PASTA repeats of the protein kinase StkP interconnect cell constriction and separation of Streptococcus pneumoniae. Nat Microbiol, https://doi.org/10.1038/s41564-017-0069-3 (2017).
Control of cell division in Streptococcus pneumoniae by the conserved Ser/Thr protein kinase StkP. K Beilharz, 10.1073/pnas.1119172109E905-913Proc Natl Acad Sci. 109Beilharz, K. et al. Control of cell division in Streptococcus pneumoniae by the conserved Ser/Thr protein kinase StkP. Proc Natl Acad Sci USA 109, E905-913, https://doi.org/10.1073/pnas.1119172109 (2012).
. Reports Scientific, 10.1038/s41598-018-20145-28Scientific REPORTS | (2018) 8:1660 | DOI:10.1038/s41598-018-20145-2
Interaction of Penicillin-Binding Protein 2x and Ser/Thr protein kinase StkP, two key players in Streptococcus pneumoniae R6 morphogenesis. C Morlot, 10.1111/mmi.12348Mol Microbiol. Morlot, C. et al. Interaction of Penicillin-Binding Protein 2x and Ser/Thr protein kinase StkP, two key players in Streptococcus pneumoniae R6 morphogenesis. Mol Microbiol, https://doi.org/10.1111/mmi.12348 (2013).
Pbp2x localizes separately from Pbp2b and other peptidoglycan synthesis proteins during later stages of cell division of Streptococcus pneumoniae D39. H C Tsui, 10.1111/mmi.1274521-40Mol Microbiol. 94Tsui, H. C. et al. Pbp2x localizes separately from Pbp2b and other peptidoglycan synthesis proteins during later stages of cell division of Streptococcus pneumoniae D39. Mol Microbiol 94, 21-40, https://doi.org/10.1111/mmi.12745 (2014).
Mass spectrometry and site-directed mutagenesis identify several autophosphorylated residues required for the activity of PrkC, a Ser/Thr kinase from Bacillus subtilis. E Madec, J Mol Biol. 330Madec, E. et al. Mass spectrometry and site-directed mutagenesis identify several autophosphorylated residues required for the activity of PrkC, a Ser/Thr kinase from Bacillus subtilis. J Mol Biol 330, 459-472 (2003).
Phosphorylation of CpgA protein enhances both its GTPase activity and its affinity for ribosome and is crucial for Bacillus subtilis growth and morphology. F Pompeo, 10.1074/jbc.M112.340331J Biol Chem. 287Pompeo, F. et al. Phosphorylation of CpgA protein enhances both its GTPase activity and its affinity for ribosome and is crucial for Bacillus subtilis growth and morphology. J Biol Chem 287, 20830-20838, https://doi.org/10.1074/jbc.M112.340331 (2012).
Structural and dynamic features of PASTA domains with different functional roles. L Calvanese, L Falcigno, F Squeglia, G D' Auria, R Berisio, 10.1080/07391102.2016.1217274J Biomol Struct Dyn. 35Calvanese, L., Falcigno, L., Squeglia, F., D' Auria, G. & Berisio, R. Structural and dynamic features of PASTA domains with different functional roles. J Biomol Struct Dyn 35, 2293-2300, https://doi.org/10.1080/07391102.2016.1217274 (2017).
Analysis of peptidoglycan structure from vegetative cells of Bacillus subtilis 168 and role of PBP 5 in peptidoglycan maturation. A Atrih, G Bacher, G Allmaier, M P Williamson, S J Foster, J Bacteriol. 181Atrih, A., Bacher, G., Allmaier, G., Williamson, M. P. & Foster, S. J. Analysis of peptidoglycan structure from vegetative cells of Bacillus subtilis 168 and role of PBP 5 in peptidoglycan maturation. J Bacteriol 181, 3956-3966 (1999).
Crystal structure of the bifunctional N-acetylglucosamine 1-phosphate uridyltransferase from Escherichia coli: a paradigm for the related pyrophosphorylase superfamily. K Brown, Embo J. 18Brown, K. et al. Crystal structure of the bifunctional N-acetylglucosamine 1-phosphate uridyltransferase from Escherichia coli: a paradigm for the related pyrophosphorylase superfamily. Embo J 18, 4096-4107 (1999).
GFP vectors for controlled expression and dual labelling of protein fusions in Bacillus subtilis. P J Lewis, A L Marston, Gene. 227Lewis, P. J. & Marston, A. L. GFP vectors for controlled expression and dual labelling of protein fusions in Bacillus subtilis. Gene 227, 101-110 (1999).
Peptidoglycan molecular requirements allowing detection by the Drosophila immune deficiency pathway. C R Stenbak, J Immunol. 173Stenbak, C. R. et al. Peptidoglycan molecular requirements allowing detection by the Drosophila immune deficiency pathway. J Immunol 173, 7339-7348 (2004).
Two-step assembly dynamics of the Bacillus subtilis divisome. P Gamba, J W Veening, N J Saunders, L W Hamoen, R A Daniel, 10.1128/jb.01758-08J Bacteriol. 191Gamba, P., Veening, J. W., Saunders, N. J., Hamoen, L. W. & Daniel, R. A. Two-step assembly dynamics of the Bacillus subtilis divisome. J Bacteriol 191, 4186-4194, https://doi.org/10.1128/jb.01758-08 (2009).
| s2orc_abstract_body | 61 |
The Brinks lock works great and matches all of the other padlocks we use ... | The Brinks lock works great and matches all of the other padlocks we use for our fitness center. Thank you! | amazon_reviews | 147 |
Induction of Phenol and Defence-Related Enzymes During Wilt (Fusarium udum Butler) Infestation in Pigeon Pea | The present investigation was carried out on wilt (Fusarium udum Butler) resistant ::: (ICPL 87119, BDN 2) and susceptible (T15-15 & ICP 2376) genotypes of pigeon pea ::: at 0 day after infection (DAI), 1 DAI, 4 DAI and 7 DAI in infected and non-infected ::: tissues to identify some biochemical markers like phenol and enzymes ::: related to phenol metabolism viz., PPO and PAL for wilt resistant. The phenol ::: content increased 1 DAI to 4 DAI in leaves and root tissue and decreased later in ::: leaves tissue only during infection of wilt pathogen. The phenylalanine ammonium ::: lyase (PAL) and polyphenol oxidase (PPO) activity were highest in resistant ::: genotypes at all the stages. The root tissues recorded 5 to 10 fold higher PAL ::: activity than leaves in all genotypes. | s2orc_title_abstract | 91 |
what does imca stand for in mental health? | An Independent Mental Capacity Advocate (IMCA) is an advocate appointed to act on your behalf if you lack capacity to make certain decisions. | gooaq | 1 |
Why change fails: knowledge counts | Purpose – This paper aims to examine the relationship between managers' understanding of a specific organizational change process and their attitudes towards implementing the change.Design/methodology/approach – After a review of the current literature on the link between organizational change, knowledge of the change, and attitudes towards implementing the change, limited research was found that examined the relationship between knowledge of change and resistance to change. Then original empirical research was conducted by administering a survey to 296 managers from the Botswana Government.Findings – The results of the regression models suggest that managers who understand the change effort are more likely to be less resistant to change. Specifically, the more a manager understood the change, the more likely they were to be excited about the change, the less likely that they would think the change effort would fail, and the less likely they were to state that they wished their organization had never impl... | s2orc_title_abstract | 107 |
If you have a joint account with someone and they whip you out, is there legally anything you can do? (NY) | Side note: In one of my classes, we were talking about what happens in a divorce proceeding. My professor (who's a lawyer) mentioned that you will probably run into some issues if you share a bank account because it shows that it was something that was intended to be shared. If someone were to theoretically do something shady to a shared bank account, what can be done? Regardless if you're married or not.
Edit: Interesting info. I'd like to also note that class has been over for a long time (good eye I guess). | reddit_title_body | 178 |
Peeps with Revision Village Gold - anyone got the N18 Prediction papers? | Just got an email saying the RV Gold November 2018 prediction papers were out, but I, sadly, am a lowly RV Free pleb.
Anyone willing to share the paper? (specifically the SL if anyone's got it)
Also all of y'all are great. Hope everyone's doing okay <3 | reddit_title_body | 312 |
what's the population of eagle crest resort | Eagle Crest Resort Eagle Crest Resort is a destination resort complex in the U.S. state of Oregon. The resort has a large hotel, a conference center, three golf courses, and three major housing developments each with multiple subdivisions. The resort is located west of Redmond in Central Oregon. The development covers on the east slopes of Cline Buttes running eastward to the Deschutes River plus a separate area on the northwest side of the butte. The resort and the area around it is classified as the Eagle Crest census-designated place (CDP) and had a residential population of 1,696 at the | paq | 486 |
The same we can see our own ranked elo, could we please see our casual elo? | I play a lot of casual conquest, and dislike ranked for the most part.
I would like to know about my casual elo.
Thank you for reading. | reddit_title_body | 449 |
kabira is the ending song of which movie | the song as his ending act during the concert he held in the parking lot of Inorbit Mall in Malad, on 19 December 2014 and the concert at Emaar Boulder Hills in the city on 27 December 2014. Apart from the vocalists of the song, it was performed by Deepika Padukone in her act from 20th Annual Life OK Screen Awards, along with "Titli", "Nagada Sang Dhol" and "Ang Lagade". Listen online Kabira song Kabira (song) "Kabira" is a Hindi song from the 2013 Bollywood film, "Yeh Jawaani Hai Deewani". Composed by Pritam Chakraborty, the song is sung by Rekha | paq | 475 |
The Reasons, Shortcomings and Implementation of the Policy of Transferring Creditors Rights into Shareholders Equity | With the enforcement of the policy of transferring creditors rights into shareholder's equity, its shortcomings in design were increasingly revealed. In order to ensure that the reform of the state - owned enterprises went on smoothly, the author thought that; it is necessary to regard the act of transferring creditors rights into shareholder's equity as financial aid; it is necessary to combine the transfer of creditors rights into shareholders equity by changing the business operating mechanism ; it is necessary to transform AMC into subsidiaries of banks at anearly date. | s2orc_title_abstract | 325 |
After half a decade of Eye Doctors telling me that the problem in my eyes was probably nothing, I've been diagnosed with Keratoconus in both eyes. | Relieved to finally get a diagnosis and be able to address the problem, but frustrating that this could have been caught much earlier and a bit upsetting that I have another weird medical issue. I almost didn't even mention it during my most recent visit to the eye doctor but in glad I did.
Also a bit bummed since my insurance now is much worse than it was a few years ago so I'll be paying out thousands of dollars for this crosslinking that's being done in my worse eye. The other eye is mild so the doctor said he wanted to monitor it instead.
How much "better" can I expect my vision to get with these contacts that I'm eventually supposed to get?
Anything you think someone with newly diagnosed Keratoconus should know? | reddit_title_body | 575 |
It is excellent. A friend of mine has only been able ... | This is the only volume by this author that I have read. It is excellent. A friend of mine has only been able to find one other book by this author that he liked. | amazon_reviews | 292 |
Transient thermal modelling of an Axial Flux Permanent Magnet (AFPM) machine with model parameter optimisation using a Monte Carlo method | This paper presents the development of a transient thermal model of the EVO Electric AFM 140 Axial Flux Permanent Magnet (AFPM) machine based on a hybrid finite difference and lumped parameter method. A maximum deviation between simulated and measured temperature of 2.4°C is recorded after using a Monte Carlo simulation to optimise model parameters representing a 53% reduction in temperature deviation. The simulated temperature deviations are lower than the measurement error on average and the thermal model is computationally simple to solve. It is thus suitable for transient temperature prediction and can be integrated with the system control loop for feed forward temperature prediction to achieve active thermal management of the system. | s2orc_title_abstract | 275 |
Writing for the Future: Echeverria's "El matadero" and its Secret Rewriting by Jorge Luis Borges and Adolfo Bioy Casares as "La fiesta del monstruo" | Daguerreotypy, Optical Metaphors, and Visual Power in Echeverría’s "El matadero" | s2orc_citation_titles | 19 |
Is there a way to get a SUP on the roof of a car next to a roof top box? | I have a narrow roof top box that take up about half of the usable space on the rack for my Subaru Forester. Is there any way to get a SUP up there as well?
If I laid the SUP down flat on a traditional carrier, there isn't enough room for the box. Does anyone have any suggestions or unconventional methods? | reddit_title_body | 126 |
Do "trick" decks last longer than Bicycle decks? | Hello, beginner here. I picked up cardistry about a month ago.
I have been using a Bicycle deck and it's already starting to wear out. I have probably been damaging more than I should and I love doing the one hand riffle shuffle, so that's probably why. But here's my question, do trick decks(don't know the correct term) like ones by The Virts last longer than Bicycle decks or they are about the same?
I know I'm gonna get one of those unique decks eventually but don't know if it's worth the investment yet since they're relatively pricy. | reddit_title_body | 106 |
sharon carter is the head of which superhero group | with the Clone Saga arc telling the people evacuated from Peter Parker's neighborhood that all is well, and Agent Woo is later seen in the Death of a Goblin arc, letting Carol Danvers know about the Goblin's most recent murder. By a 2008 storyline, Carter is the acting head of S.H.I.E.L.D.. She asks the Fantastic Four to investigate a confusing situation at Project Pegasus. Sharon Carter Sharon Carter (also known as Agent 13) is a fictional character appearing in American comic books published by Marvel Comics. She is usually depicted as a secret agent and an ex-field agent of S.H.I.E.L.D. | paq | 385 |
Two LNA topologies for use in UWB systems are examined and compared in this paper. Design specifications have been derived from a ground penetrating radar system which is the target application. Circuits have been designed to cover the frequency range from 3.1GHz to 10.6 GHz. The SiGe:C technology SGB25V of IHP Microelectronics is applied to enable volume production at low prices. For measurement purposes, input and output are matched to 5Ω. | A low noise amplifier (LNA) is implemented in this work for ultra wide band (UWB) localization and sensing systems within a wide frequency range starting from 400MHz and up to 10GHz. The topology used is a resistive shunt feedback and a peaking inductance in series with the output transistor to achieve the desired bandwidth and have better noise performance. The LNA is fabricated in low cost 0.25µm 92GHz f max SiGe-HBT-BiCMOS process technology. The area of the manufactured chip is 0.73mm2. The achieved gain is 12dB with a NF less than 3.7dB over the entire frequency range while the consumed power is only 14.5mW. | s2orc_abstract_citation | 48 |
when did the university of pisa re-open | University of Pisa of a cherub was placed above the gate "Dell'Abbondanza" (the "Gate of Abundance"), leading to the piazza, and today is still the symbol of the university. Following the rebellion and the war against Florence in 1494, the Pisan "Studium" suffered a period of decline and was transferred to Pistoia, Prato and Florence. The ceremonial reopening of the university on November 1, 1543, under the rule of Duke Cosimo I de Medici, was considered as a second inauguration. The quality of the university was furthered by the statute of 1545 and the Pisan Athenaeum became one of the most significant in | paq | 164 |
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