November 07, 2016 at 03:54AM

Today I Learned: 1) Don't eat raw yucca. It leeches cyanide in the digestive tract unless you cook it properly, especially from the skin. 2) There are those who say that World War I was inevitable. Others claim that it could have easily been avoided if a few people had just gone to the table and talked. Well, today I learned that only a few days before the German invasion of Belgion that kicked off open hostilities in the war, Russia's Tsar Nicholas II and Germany's Kaiser Wilhelm II were telegramming each other promising that they were doing everything possible to keep their respective countries out of the war and urging each other to do the same. Alas, the military leadership in both countries managed to overrule their civilian leaders. So if the Kaiser and the Tsar couldn't stop the war, who could? 3) Also in World War I news, today I learned that there was widespread public support for war in France before the German invasion. There was widespread desire for revenge against the Germans for the last war the two had been in. One example of simmering public sentiment: less than two weeks after the assassination of Franz Ferdinand, the French Socialist leader Jean Juarès was publically assassinated in a restaurant. Juarès had been one of the most prominent anti-war voices in France, and his death may have actually been more widely-noted than Ferdinand's at the time. These last two facts courtesy of the "The Great War" channel on Youtube. I've just started watching their series on the Great War, produced weekly, going over the events of each week as they happened 100 years before. The series started in August of 2014, and is scheduled to end in late 2018. I intend to stay about two years behind, though I may try to catch up to keep the dates straight.

November 03, 2016 at 04:35AM

Today I Learned: 1) A vote in the US is arguably worth thousands of dollars, if not tens of thousands. How do you figure? Well, only something like half of the US votes. Say that's 150 million people. What are the odds that your vote is the swing vote that decides the election? Something like 1 in 150 million (it's been estimated at much, much bigger than that -- I've seen numbers as high as 1 in 10 million, but this will illustrate the point plenty well, I think). That's not very likely... but if it does happen, then you've just decided, to some degree, the fate of several trillion dollars. If only 10% of the budget is affected by the candidate, then that's still hundreds of billions of dollars allocated in accordance with your vote. It's not a very precise mechanism of spending money, but it's potentially an *extremely valuable* one. 2) GamS is apparently a rather difficult protein to purify. Not sure why. Slightly relatedly, having a (standard-difficulty) protein purified costs around $500 from a protein purificaiton center. 3) The US has teams of military personel called "Red Cells" that break into US facilities and do things like take over submarines, kidnap VIPs, and plant bombs, all in order to reveal security vulnerabilities.

November 02, 2016 at 05:12AM

Today I Learned: 1) The current best theory of the origin of life is neither "RNA world", "lipid world", nor "metabolism world" (or whatever you call the hydrothermal vent hypothesis). It's what you might call "everything world" -- the idea is that a complex but not altogether unlikely mix of organics all came together to produce RNA, amino acids, and micelle-forming lipids, all in a clay microenvironment that could definitely catalyze ribonucleotide production and might be able to support ATPase-like metabolism. See http://ift.tt/2ecU9m2 for details, including a bunch of brief but colorful biographies of some of the crazy scientists behind this field. 2) There are a lot of little tidbits about the Mona Lisa. Here are a couple: The Mona Lisa was originally a painting of someone else. It was painted over in multiple layers, with normal paints and with translucent varnishes. The blue sky in the background of the Mona Lisa was painted with lapis lazul, which at the time of the painting cost more than gold by weight. The Mona Lisa was owned by Napoleon, who hung it in his washroom. It was damaged by water stains while "installed" there. 3) There's a famous sketch of Leonardo da Vinci's of what appears to be a modern bycicle... which is probably a fake. It was done in graphite, which wasn't invented until after Leonardo's death.

November 01, 2016 at 12:30AM

Today I Learned: 1) ...a few things about Salem, Massachussets. It was named after "salam", as in "peace". It was once the capital of the Massachussetts Bay Colony, until a governor's son drowned in the river near the city, and the governor decided to move the capital to Boston to avoid memories of his son's death. Salem also used to be one of the more wealthy, thriving ports in New England. Much of modern-day Salem occupies what used to be ocean, which was filled in with at least one New Hampshire mountain. List continues. 2) A joint iGEM team from Ludwig-Maximillian University and the Technical University of Munich just presented a new technology for 3D printing tissues. Current standard organ-printing technology involves printing alternating layers of hydrogel scaffolding and cells. The scaffolding provides structure for the cells until they're nicely adhered. Then the hydrogel is blasted or chemically washed away, which is fairly destructive. The Munich team built several cell lines that display biotin on their outer membranes. They print by injecting those cells (free-floating!) into a media containing tetrameric avidin variants*. The biotin on the cells sticks to the avidin in the media, and the avidin (being tetrameric --> having four binding sites for biotin) acts as a chemical bridge that causes the cells to stick together. They clump up almost immediately, and form vaguely rigid structures, or at least as rigid as a pile of cells is going to get. They can print pretty nice-looking 2D shapes, and they've demonstrated the ability to print two layers, with cells sticking in their printed layer quite well. The printer the team used was a modified Ultimaker 2. They modified it with a special printing head and a custom bed for holding petri dishes, both of which can be printed by the vanilla version of the Ultimaker for a conversion cost of about $50. * For those who don't remember from previous TILs, avidin and biotin are notable proteins mostly because they bind together really really strongly. 3) Chinese medicine has a regulation problem in China. Chinese medicinal substances occupy a weird liminal space between food and medicine, and as such somehow don't fall under the regulatory purview of any Chinese regulatory agencies. That's bad, because they are, in fact, taken as both food *and* medicine, and it turns out that it's not enormously uncommon for Chinese medicine to be contaminated with heavy metals or Aspargillus (which excretes some pretty nasty toxins).

October 30, 2016 at 11:31PM

Today I Learned: 1) In the late Victorian era, there was a very wealthy woman by the name of Isabella Stewart Gardner. She married into yet more wealth, and spent a good amount of it patronizing art of every kind. Her house was a veritable art gallery in itself, and when she died, her will stated that her house be turned into a museum. The will also specified that if any piece of art were removed from its original position, the entire estate would be put up for auction and the proceeds donated to Harvard. You can still go there -- it's a beautiful collection of collections, ranging from classical sculpture (imported from Europe) to medieval furnishings and paintings (also imported from Europe) to some of the most avant-garde painting of Gardner's time. 2) When the printing press was first invented, most printed books had very large margins so that illuminators could come in after printing and add illustrations around the edges. It was a big deal when printers first started adding illustrations directly by print, and there were artists who specialized in print art. 3) It's possible to 3D-print molds for microfluidic devices, using relatively inexpensive printers. An iGEM team from Uppsala, Sweden, used a 3D printer to manufacture microfluidic rigs for heat-shock transformation of bacteria. Including the cost of the master and chip, they managed to bring the cost of transformation down moderately (from something like $2.5/transformation to something like $1.4/transformation). The chips looked really nice, too.

October 30, 2016 at 12:07AM

Today I Learned: 1) There are human cell lines that aren't adhesive! Some kind of immune cell lines can be grown free-floating in media. 2) Glucose meters work by measuring the activity of glucose oxidase (GOx) or, more rarely, glucose dehydrogenase (GDH), which both metabolize glucose into other sugars. Both reactions are redox reactions, and the resulting change in oxidation state can be measured with a properly-built sensor. The more glucose, the more GOx reactions per second, the higher the amperage through the sensor. I also learned that you can make a similar device to detect ethanol using AOx (alcohol oxidase) instead of GOx. An iGEM high school team from China built such a device, which could detect alcohol levels in water with reasonable accuracy. They didn't test it in blood. 3) You can swap the active sites of different proteases, and it will work (at least sometimes).

October 28, 2016 at 11:13PM

Today I Learned: 1) The E. coli genome apparently forms a solenoid-like helix with a turn size of about 100,000 bp. This means that stuff like sigma factors that recruit other enzymes to specific locations in the genome can also affect locations that appear to be very far away, but are physically close to each other in the cell. Note that the diameter of this solenoid is significantly bigger than the diameter of an E. coli. I believe this works out because there is also higher-order coiling of the genome. Also note that this is old news to scientists who study Eukaryotes. I just didn't know that it also happened reliably and repeatably in bacteria, or that the bacterial genome formed such a huge loop. 2) The single most important chemical in modern dry-cleaning is perchloroethylene (or PERC). It's incredibly cheap, incredibly good at removing stains, and somewhere between midly and very toxic (and probably a carcinogen). It's nasty stuff to work with, but it's very difficult for dry-cleaners to get away from. France recently put a ban on PERC, set to go into effect in 2022. The iGEM team of Paris-Bettencourt decided to interview every dry-cleaner in Paris, in person, to determine what effect the ban has had so far and what dry cleaners are looking to replace it with. It turns out that a) a lot of dry cleaners are still using PERC, b) a lot of dry cleaners have moved away from PERC, c) by region, PERC use is negatively correlated with immigrant populations, d) a nontrivial number of dry cleaners report feeling sick around PERC, and e) a lot of dry cleaners don't really know how they can survive without PERC -- it's just too damned economical. 3) Bacteriosins are a class of toxic protein secreted by bacteria to kill or inhibit closely-related species. They are much more effective than standard lab antibiotics, and after fifty years of use in the food industry, we still don't see resistance to them in any meaningful amounts. Unfortunately, they're also quite narrow-spectrum, and they aren't particularly useful medicinally in part because they break down very quickly in the stomach.

October 28, 2016 at 12:11AM

Today I Learned: 1) One way to think about cancer -- it's a reversal, within a single organism, of the evolution of multicelluarlity. I don't think this really tells me anything strictly *new*, but it's a nice way of crystallizing a lot of ideas about cancer in a succict way. 2) Saw some really old piano-like instruments today, including a pianoforte, harpsichord, and clavicle from around the 1730s. Seeing those instruments in person really puts Mozart and the other classical composers in context. They're dainty instruments, relatively delicate-looking and very ornately decorated (though admittedly I was looking at some very wealthy persons' instruments). If I were Mozart and I was given one of those to work with, I bet I'd come up with something classical-sounding too. 3) There was a brief period in ancient Egyptian sculpture where the principal subject of the sculpture would be shown more than once in the same sculpture. I saw one example from a high-ranking official's tomb showing the guy, the guy again with a different kilt, and his wife and children. Nobody is really sure why they did this.

October 27, 2016 at 02:28AM

Today I Learned: 1) ...a plausible reason a single-celled organism might evolve multicelluarlity. Yeast cells in the wild have an occasional mutation that prevents their cell walls from splitting apart when they divide. The result is that they form almost-clonal clumps. Lab yeast been selected to not clump, so they live almost entirely as separate cells. Question: under what circumstances might that clumping feature be selected for? Here's one. There are some nutrients that yeast can only absorb after they're digested outside the cell. For example, yeast can break down extracellular sucrose (which they cannot process directly) into glucose and fructose (which they can process directly) by expressing the enzyme invertase on the outside of their cell walls. The problem is that much of the fructose and glucose they produce floats off into the surrounding media, where it is inaccessible or worse (it could be eaten by a competitor! *Gasp!*). A group at Harvard proposed that clumped cells might have a selective advantage in a sucrose-rich media, because having a bunch of clumped cells together raises the local concentration of available fructose and glucose quite a bit. They raised single cells of yeast in a range of concentrations of sucrose and glucose, then, based on which ones grew and which didn't, backed out a model of sucrose digestion and diffusion. They added clumping to their model, and predicted that clumped yeast should be able to survive on less sucrose than the non-clumped variety. They generated some clumping yeast mutants, tried seeding *those* in sucrose media, and their predictions panned out. There are a lot of other possible reasons to start building a multicellular colony -- for instance, it makes you potentially much harder to eat -- but this is a very nice experimental exploration of one such reason. You can read the rest (for free!) here in PLOS Biology: http://ift.tt/2dZ3jG4 2) Bose is the undisputed master of the noise-cancelling headphone industry. This in itself would make a fine little TIL, but I *also* learned today that Bose *also* uses noise-cancelling tech to make super-smooth suspension for driver's seats for truckers. It turns out that taking vibration from a truck for hours and hours every day isn't very good for you, so making a driver's seat that doesn't vibrate is a big deal. 3) What the rice plant looks like. It basically looks like wheat.

October 25, 2016 at 12:34AM

Today I Learned: 1) If Python throws an error at you involving receiving instances instead of something else, you probably forgot to put a "self" argument in a method declaration. 2) ...a little bit more about ring species, which I mentioned yesterday. I didn't realize that the bit where the species at the two ends of the geographic range can't interbreed is a *requirement* of a ring species. I thought it was just a thing that *could* happen. I was wrong. Along with that, I learned today that ring species are incredibly rare. Wiki claims there are only four known ring species (three kinds of birds and a tree), and that three of them are controversial (the tree is definitely a ring species). 3) Markov-Chain Monte Carlo (MCMC) is a class of algorithms for drawing random samples from a distribution where you can't explicitly write out the distribution, but you can evaluate the density of that distribution at any given point. A key property of MCMC algorithms is that they're memoriless -- once initialized well, consecutive samples returned by MCMC are independent. Today I learned a bit about how several different flavors of MCMC actually work. Classical Metropolis-Hastings MCMC starts with a "walker" at some point. In each iteration of the algorithm it takes a random walk in any direction, then probabilistically decides to either stay there or go back, based on how high the density of the underlying function it's walking over (the higher the density, the more likely it is to say; intuitively, this means it will spend more of its time where the density is high). Adaptive MCMC works the same way, except that when the adaptive MCMC takes a walk, it isn't totally unbiased in its direction -- based on past results, it tries to learn when there is covariance in the underlying function (imagine a narrow ridge in the function's landscape) and changes what directions it will walk in accordingly. This is to save some computational effort when it encounters very narrow ridges, which are apparently pretty common. Vanilla Metropolis-Hastings would spend tons of iterations jumping off the cliff to either side and rejecting the new value, so it takes it a long time to move around on those ridge; Adaptive MCMC spends most of its time just walking around on the ridge. The MCMC Hammer (a very popular Python package for MCMC) works by having many walkers, all working in parallel. At each iteration, each walker picks another walker and takes a random step towards (or away from?) that walker. This solves the ridge problem much the same way as the adaptive MCMC, but I think it's a bit more robust on certain kinds of functions, and it's *much* more parallelizable for a multi-core system, since multiple walkers can be updated in one operation.

October 24, 2016 at 01:51AM

Today I Learned: 1) A ring species is a kind of species undergoing spatial speciation where the species varies considerably, but continuously, across its geographic range. Typically a ring species varies enough from one end to the other that members of the populations at opposite ends can't interbreed. It's called a "ring" species because in some cases, the geographic range bends back so that the populations at either end actually overlap, but are still distinct because they can't interbreed. 2) One of the common traits of developing market (i.e., third-world country) is high local currency volatility -- many developing markets have a large degree of political or financial uncertainty, which leads to rapid and frequent changes in the relative value of the nation's currency. 3) If you 3D print a part and it comes out warped, you can sometimes fix it by heating it with a blow dryer and twisting it back into shape. Thanks Andrey Shur!

October 23, 2016 at 03:07AM

Today I Learned: 1) A number of chess endgames in which one player only has a king and the other players only have a small number of pieces, have been solved, though some solutions are difficult to execute. Two knights, for example, cannot win against a king. Two bishops can, but it's difficult to execute without accidentally tieing. 2) "Wort" is a word, but not the word I thought it was -- wort is, according to Wiki, "the liquid extracted from the mashing process during the brewing of beer or whisky". 3) ...about Margaret Sanger. When I first heard the name, I thought perhaps she was the inventer of Sanger sequencing, which had me really excited to learn about her. Turns out she's just one of the most important sex educators in the 20th century and basically started birth control as an institutional thing in America. Oh well.

October 22, 2016 at 03:08AM

Today I Learned: 1) People really notice (and care) if a conference has bad coffee. 2) Janelia Farm (one of the coolest biological research institutes out there -- if you don't know about it, you should check it out!) has an endowment from HHMI of about $19 billion. That covers something like 50 very well-funded labs, operating with some ridiculous equipment. Just a good number to know in terms of calibrating institute expenses. 3) I really like the style of the current director of the FBI, James Comey. Check out his prepared remarks on Clinton's recent email scandal -- it's clear, precise, balanced, well-structured, and addresses a lot of possible questions an audience member might want to ask. Really my kind of informative prose. http://ift.tt/2dX27AB

October 21, 2016 at 02:47AM

Today I Learned: 1) Learned a bit about insect immune systems. For one thing, I learned that hemolymph, the goey stuff that insects pump around their body, doesn't carry much oxygen. It mostly seems to be for moving nutrients around... and for immune system function. 90-95% of the cells in the hemolymph are killer cells, which detect, track down, and ingest foreign cells. These are insects' primary line of defense against pathogens. The other major immune system component insects have is a system of anti-microbial peptides, or AMPs. AMPs are a diverse class of small proteins produced across the eukaryotes, but they're particularly important to insects. AMPs act as antibiotics in a number of ways, and are secreted en masse when the insect's immune system detects an invasion. 2) Remember that weird nested symbiosis I mentioned a couple of TILs ago? With the bacteria that lives in a bacteria that lives inside an insect? Today I learned a bit more about that triple symbiosis. The insects (it's actually a whole clade) in question are mealybugs, a clade of tiny little fuzzy sapsuckers, meaning they live on sap sucked from host plants. This isn't a very nutrient-rich diet, so it helps to have symbiotic bacteria that can metabolize unusual carbon sources. The first-level endosymbiont is Tremblaya, a bacteria that has been reduced to almost organelle status -- it has a massively reduced genome, even lacking the standard tRNA synthetases found in, say, mitochondria. The endosymbiont of Tremblaya, in contrast, is much closer to a normal bacteria in genome content. The second-level endosymbiont varies pretty widely across mealyworm species. It's worth noting that having a bacteria living inside a bacteria is extremely unusual. As far as I know, there aren't any known cases outside of insect cells. It's thought that Tremblaya can acquire an endosymbiont because of its unusual cell membrane. See, it's so massively reduced that it no longer has its own genes for synthesizing a membrane and cell wall. It relies on the mealyworm to produce a membrane for it. This means that from the outside, it effectively looks like a eukaryote -- and the symbionts that live in Tremblaya happen to be well-adapted to invading eukaryotic cells. 3) ...about preadaptation. Preadaptation is when a species just happens to have a trait that makes it very well suited for an environment it hasn't encountered before. When the preadapted species *does* encounter that environment, it tends to do quite well. You could consider any successful invasive species an example of preadaptation. Another example is thought to be lobe-finned fishes, which have far, far fewer bones in their fins than ray-finned fishes (most fish are ray-finned). I don't know why they evolved lobs, but it seems to have been really useful to have a small number of finger bones when the first lobe-finned fish started to crawl up onto land -- which is why we have five fingers on a hand instead of fifty (lobe-finned fish have order of ten digits per hand; ray-finned fish have more).

October 20, 2016 at 02:08AM

Today I Learned: 1) ...the "true" definition of molecular cooperativity. Cooperativity is (can be?) defined as a property of a chemical reaction in which one reaction makes a second more likely. 2) ...a few bits and pieces of Norse mythology. There are a surprising number of giant worms (snakes) in Norse myths. Also a lot of wolves, ravens, and eagles. All three of the latter were in some sense signs of war -- not good things. Wolves, for instance, didn't have their modern connotation of nobility. They were considered savage, bestial things, full of hunger and spite. 3) You can, in principle, build a high-gain, high-accuracy amplifier from a high-gain, low-accuracy amplifier coupled to a low-gain, high-accuracy amplifier.

October 19, 2016 at 02:49AM

Today I Learned: 1) At Caltech, if you don't register for classes, you will be classified as not-enrolled, which can cause you to lose building access priviliges. As far as I can tell, that is the only consequence of not registering. 2) In HTML, the "a" tag is is the tag defining a hyperlink. Why "a"? Seriously, why "a"? I have no idea. 3) The word for a tile used in a mosaic is "tessera", or "tesserae" for plural.

October 17, 2016 at 02:10AM

Today I Learned: 1) We've had jellyfish in space since 1991. A bag full of polyps was sent to up with a space shuttle, and has been growing in microgravity ever since. The jellyfish were recently brought back to Earth. They did not handle gravity very well -- they were pretty bad at maintaining orientation in true gravity. 2) Spaghetti is... trickier to cook in tomato sauce than the other pastas I've tried. Sauce doesn't soak into the pasta as quickly as boiling water, which means there's this awkward and rather lengthy period where the spaghetti remains stiff, which makes it a) hard to mix in properly to where it can absorb sauce better and b) hard to mix the bottom, which causes it to tend to burn. 3) Never run "conda upgrade --all" without superuser privilages. Just like with pip, if conda detects that it needs to upgrade itself, it will download the newer version of itself, uninstall itslef, and re-install the new version. Except that if you don't have superuser priviliges, it fails during the reinstallation bit, leaving you with a broken, half-uninstalled conda that's really difficult to clean up after.

October 16, 2016 at 04:24AM

Today I Learned: 1) Linked traits were well known to breeders and horticulturalists by Darwin's time (and probably long before then), though there was no explanation until geneticists realized how genetic linkage works. Relatedly, when Darwin wrote "On the Origin of Species...", it was widely believed that domestic animals tended to gain floppy ears from disuse, since they did not need to raise them in alarm as frequently as their wild cousins. (In fact, droopy ears seems to be linked with other traits of youth, which tend to be selected for through domestication.) 2) The Feynman Sprinkler is an interesting physics puzzle. Imagine a standard garden sprinkler. It spits out water, and the resulting momentum transfer causes the sprinkler head to spin. Now imagine you reverse the flow of the pump providing water, so it sucks in rather than spitting out. Put it in a tank of water. What happens to the reverse-sprinkler? The result is... confusing, at least to me. Think about it for a few minutes, then check out the Wiki page on "Feynamn Sprinkler" and see if you can make sense of it. 3) ...how to use CSS classes! Somehow I keep re-learning this over and over again, but I always have to re-learn it anew whenever I take on a new HTML project.

October 15, 2016 at 01:57AM

Today I Learned: 1) There is an insect with an obligate endosymbiotic bacteria -- that is, a bacteria that lives in the insect's cells, and provides important functions to the insect -- that itself has an obligate endosymbiotic bacteria. More details to follow. 2) Relatedly, there's a well-known nasty effect that happens when one organism becomes a required endosymbiote for another (usually it's a plant or animal that takes on a bacterial endosymbiote) that poses a serious danger to both organisms. See, endosymbiotes have to deal with having an incredibly small effective population size, since a) they can't really get access to outside populations to recombine genetically, and b) they undergo a nasty population bottleneck whenever the host reproduces. It turns out that the effects of genetic drift become much more severe with small populations. If the effective population size is small enough, drift and random mutation will overcome selective pressure, and the symbiote's genome will literally start to degrade on evolutionary timescales. See, population size and mutation rate are intimately linked, and both contribute to the maximum size genome a species can stably maintain through selection. The higher a species' mutation rate, the smaller the biggest genome they can maintain over many generations. Smaller population sizes effectively amplify the effect of mutations on genome degradation. There's some thought that this is basically what determines genome length -- species adapt to have genomes that are sizes their mutation rate can support, basically. That's why RNA viruses, which have insane mutation rates, also have insanely tiny genomes. Probably. In the case of endosymbiotes, the symbiote evolved to cope with a reasonable mutation rate/effective population size, but gets hit rapidly with a much harsher mutation rate/effective population size. The net result is that the symbiote's genome gets quickly whittled down to a small fraction of its original size. An extreme example is the ancestral predecessor of the mitochondria, the genome of which was whittled from a (presumably) normal-sized bacterial genome to a 10-20kb circlet. This puts the host in a real pickle. Now it depends on an endosymbiote, but that endosymbiote is rapidly degenerating. Thus begins a mad scramble to somehow make the symbiote functional before it completely loses any ability to function, killing both symbiote and host. This is presumably why gene transfer from symbiote to host is so common (it's been observed in just about every sufficiently-old endosymbiotic relationship) -- it keeps the endosymbiote functional while reducing its genome size, making it less likely to decay to uselessness. 3) ...what a young termite queen looks like. It's a surprisingly elegant looking insect, at least from afar -- it has long, diaphanous wings, making it look almost like a squat dragonfly, but with a flight pattern more like a moth.

October 14, 2016 at 03:49AM

Today I Learned: 1) I like persimmons! I'm not sure if I'd ever actually had a persimmon before, but today I had one pretty much fresh off a tree, and it was pretty darned good, for a fruit. I'd describe the taste as kind of a mellow, sweet, orange/mango flavor. 2) There are parasitic transposable elements. I mean, all transposable elements are parasitic on the host genome*. There are, however, also transposable elements that have lost their protein-coding regions. They aren't actually fully functional without *another* transposon around to snip them out and move them from place to place. There are some really clever adaptations transposons have evolved to combat parasitic transposable elements, including a whole class of RNA transposons that get transcribed, leave the nucleus, produce a virion-like coat from a protein monomer, reverse-transcribe themselves, produce and attach an integrase to themselves, and move back to the nucleus for insertion. * this is contentious -- some scientists, most notably those from the ENCODE project, think that transposons are kept around as drivers of genetic variation. However, today I learned that the wider molecular evolution community suspects that this is rubbish, and that transposons are truly junk DNA, in the sense that they do not contribute to host fitness. 3) Apparently what we call "transgenderedness" today was relatively common in Native American societies. Of course, any time someone talks about "Native American societies", they're talking about a huge swath of cultures, some separated by centuries or millennia of divergence, so keep in mind that everything in this particular TIL is a MASSIVE generalization, BUT! The point is that many, many Native American societies had between three and five standard gender concepts. Typcially these were roughly equivalent to one or more of "male", "female", "male in female body", "female in male body", and "male and female". The non-("male" or "female") genders (referred to as "two-spirits" in modern parlance) were considered anywhere from perfectly normal to special and honored. Interesting how different other cultures' views of gender can be from our own... yet also interesting how ultimately circumscribed those gender views are. It all really boils down to variations on "male" and "female" -- even accounting for cultures quite different from ours, the human race hasn't explored the space of possible genders very thoroughly.

October 13, 2016 at 02:24AM

Today I Learned: 1) When ISIS first invaded and took ground in Iraq, they did so largely on the back of a massively successful media campaign. ISIS only had a few thousand troops, but they put out a number of well-produced battlefield videos on Twitter and Facebook and other platforms that made them look like a much bigger threat, essentially magnifying the effects of a string of small victories. As a result, they were able to force the surrender of Iraqi forces an order of magnitude larger than their own. 2) There is a transposable element*, called the P-element, that was acquired by the fruit fly D. melanogaster very recently (within the last couple hundred years). It confers a whole constellation of nasty phenotypes on its bearer, including a high probability of sterility. When discovered, the P-element quickly became a classic example of the spread of a selfish element in a naïve population. Also, since the invasion, D. melanogaster has developed an RNA interference pathway to shut it down. More recently (between 1800 and 1950!), the P-element invaded another fly species, D. simulans (which I assume is named so because it's similar to D. melanogaster?). Evidence points to a single horizontal gene transfer event being behind the invasion. * a transposable element is a gene which does nothing but move and/or copy itself into other parts of the genome, found almost exclusively in Eukaryotes. It's hotly contested whether or not transposable elements are functional in some way, if they're just selfish genes that their hosts can't get rid of. 3) Viridis, the current most-popular colormap in matplotlib, is very similar to Matlab's current default colormap, parula, but has been tweaked so that a) the gradient is visually smooth across the entire range of the colormap and b) it doesn't lose contrast if you're red-green colorblind. For more details, see http://ift.tt/2dZgvvp.

October 12, 2016 at 03:06AM

Today I Learned: 1) Here's a little algorithmic puzzle: You have a point (x,y) somewhere in the unit square, where one corner of the square lies at (0,0), the other at (1,1). You want to "jiggle" the point by moving it around randomly, in any direction, in a kind of Gaussian way. What algorithm do you use to make sure the point doesn't leave the square? Can you make it efficient? It's a trickier puzzle than it looks. It's not capital-D Difficult, but it's tricky. Try it. Ok, so here's an algorithm I used: 1) Pick a random angle theta, uniformly sampled between 0 and 2*pi radians. Then draw a number N from a Gaussian centered at zero. Try adding N*sin(theta) to the point's y-coordinate and N*cos(theta) to the point's x-coordinate. If that point leaves the unit square, draw another N and try again. Today I learned that this isn't a good algorithm. It works most of the time, but if you have a point in the corner and you get an angle facing the wrong way, it goes infinite (or close to infinite) and breaks. For example, imagine the point is at (1,0) and you pick 45 degrees as your angle. Now, no matter what N you choose, it'll be outside the unit box. There's a simple fix -- re-choose the angle every time you re-choose N, and before too long you'll get a good combination. Can you come up with an algorithm that isn't as wasteful? 2) A timing belt (or cam belt) is a geared belt that physically synchronizes various valves in an engine. If it fails, the engine can do really nasty things involving terms like "catastrophic failure". Apparently it's also possible for a timing belt to be off in such a way that causes accelerator input to the engine to be delayed, though I don't see how that's actually possible. 3) Mantis eyes may change color over the course of the day? I noticed that my mantis's eyes were dark, almost opaque. This made me a little worried, because usually I can see right to the back of the eye, where there are little itty bitty pupil-like spots. Later, though, it went back to normal, so I guess it's not a problem? I'm going to have to keep an eye on this.

October 11, 2016 at 01:11AM

Today I Learned: 1) You know those fancy prepackaged salads with multiple lettuces of different colors? Apparently those lettuces are grown together, in parallel rows, so that they can be harvested together and processed and packaged in the field for shipment. The effect is quite beautiful. 2) Last night I ran an experiment evolving agents in a series of iterated prisoner's dilemmas*. The agents were limited to "reactive strategies", which are strategies in which each agent probabilistically determines whether to cooperate or defect based on only the last move of the opponent, where the cooperate rate for each possible previous move can be tuned between 0 and 1. Each generation, each agent plays an iterated prisoner's dilemma against some fraction of the other agents (one at a time). The total fitness of each agent is calculated, then a new population of agents is randomly selected from the original (with duplication possible) where each agent's probability of being picked for the next generation is proportional to its fitness. Finally, each new agent's paramters are jiggled slightly to add variation to the next round of selection. Here are a couple of lessons I've learned from the results: 2a) Taking a random (Cauchy, in this case, which is like a bell curve but with greater probability of a large result) move in one axis and then another random move on the other axis isn't even *close* to a good way to generate random spread around a point (this came up when generating mutations between generations). 2b) Tit-for-tat, which is generally considered a really, really good strategy in an iterated prisoner's dilemma, doesn't seem to be stable in my evolution simulator. If you start with all of the agents clustered in the "cooperate after the opponent cooeperates; defect after the opponent defects" corner of strategy space, they pretty quickly start to spread out. Notably, I got a cluster of strategies at around generation 20 that defected a lot, and they seemed to do much better than the tit-for-tatters. By about generation 65, the agents were totally spread around strategy space. I've read that tit-for-tat is actually really vulnerable to "mistakes" in gameplay, as happens when the agent's probability of cooperation in response to cooperation isn't quite 1. If you have two agents that copy the other one with 99% fidelity, then eventually one of them will mess up. When it does, they get stuck in a vicious cycle of betrayal, which isn't very profitable for either one. Or maybe I've added too much mutation, and nothing is actually stable. Or, alternatively, my population size (100) could be too small to overcome genetic drift with the level of selection I'm applying. 3c) Some possible evidence to support the "too much mutation" hypothesis -- in a much longer simulation (5000 generations), it looks kind of like there's a ton of wandering around, without much in the way of stable strategies. I only printed out population snapshots every 50 generations, so it's hard for me to say right now exactly how the populations are moving, but they're definitely shifting around a lot between snapshots. A common -- but not universal -- trend is that defecting when the opponent cooperates is a highly profitable strategy, wheras whether or not the agents cooperate after a defection doesn't seem to matter much. I don't like the way I handled mutation in last night's run, so I've fixed it and will start another simulation tonight, this time sampling every generation (and perhaps not running quite as long). * I'm assuming most of my readership knows what a prisoner's dilemma is; if I'm wrong about that, let me know and I'll explain in the comments. 3) My new favorite party music playlist: http://ift.tt/2d8WCNW

October 10, 2016 at 04:13AM

Today I Learned: 1) Concentrated calcium chloride tastes... bad. Like, burning chemical bad. Like "this should not be in contact with living tissue" bad. Don't do it. 2) If you try to make cheese using a standard feta cheese kit, but with soy milk instead of real milk, it doesn't curdify. It turns into a rather thick, pudding-like mix that's kind of halfway to setting... but it doesn't get there. Next time, I will try adding some calcium chloride, which supposedly helps harden cheeses if you put it in at the right time (I didn't). 3) Numba, a just-in-time compiler package for Python functions, has a lot of limitations. It can compile classes, but only if you give it a bunch of type information about what kinds of inputs the class is going to get, and it doesn't support all of the features of the compiler. It also can't compile methods of objects -- only free-standing functions. Even then, it's a bit tetchy. I think it's back to Cython with me if I want to get this code to run much faster....

October 09, 2016 at 04:22AM

Today I Learned: 1) "Peccable" is a word. It means "capable of sinning". It was used much more widely in the early 19th century, according to Google, and fell out of usage somewhere around 1950. 2) Rennet tastes like... well, it's hard to describe. It's subtle, slightly aromatic, slightly acidic, slightly salty, and a little broth-like. Honestly, it tastes a bit too much like the smell of minipreps for my taste, as delicious as they sometimes smell. 3) There are gated communities for RVs.

October 08, 2016 at 04:24AM

Today I Learned: 1) You know the lemonade machines that some restaurants have, where you can see the lemonade swirling around in a tank? It turns out that, at least in many cases, that lemonade is not what you get in your drink. It's just there for show. Your drink is actually mixed from a contraption underneath the counter. This deceptive device actually lies at the center of an interesting turn in patent law, which basically says that you can get a patent even if the device you patent is immoral or deceptive (or, as it turns out, even illegal). A few more details here: http://ift.tt/2dTHa90 2) There are salts that are liquid at room temperature. I only know about one, and I only sort of know its structure -- it's a somewhat complex organic, much bigger than the usual salts you hear about in a chemistry class. 3) There are attempts right now being made to chemically sequester CO2 from the air, potentially converting it into methanol or other useful fuels. Unfortunately, the process isn't efficient at atmospheric levels of CO2 (even though we're now well above 400 ppm...), so it's really planned for use in CO2-emitting plants as a kind of air scrubbing technique. It's also really, really hard, and we don't have a good way to do it yet.

October 07, 2016 at 01:52AM

Today I Learned: 1) SSD drives (and presumably flash drives, too) have an interesting problem in that they read and write in entire blocks of .5-1 megabytes. When a write happens, the entire block is actually read, modified, and written back in. That's particularly annoying since flash memory wears out with use, and too many read/write cycles to a single memory location will break it. Accordingly, SSD manufacturers have a lot of tricks for reducing write requirements. Also, SSDs come with a bit of extra memory onboard. When blocks break, they can detect the fault, permanently lock out that block, and allocate to one of the reserve blocks instead. 2) So, how long do SSDs last? This (http://ift.tt/2cWbdkE) delightful experiment from last year pushed six commercial SSDs to their deaths. According to the authors, SSD manufacturers guarantee their drives to about 20 TB of read/writes, or 20 GB/day for three years. In fact, they perform well for much, much longer -- of the six drives tested, none hit a single error until around the 100th terabyte. *That* drive continued to funciton, albeit with increasingly smaller storage capacity, until between 800 and 900 total writes. Other drives performed better, logging hundreds of terabytes before their first failure and the best writing over a petabyte before finally crashing for good. Not bad. Thanks to Chris Lennox for finding this! *Just a warning, when I left a tab with this article open for a while, it started sucking up memory and processing time. By the time I killed it it was using several gigabytes of RAM. Not sure if that was a bug or some kind of background process, but I thought you should be aware. Can anyone replicate? 3) There is a species of parasitic wasp that lays its eggs in caterpillars... you know, there are a lot of great evolutionary stories that start that way, or at least very similarly. Anyway. This *particular* species has a weird quirk that their young hatch together as a brood and then immediately mate with any wasp around, which is usually siblings. Yes, it's odd that they're so inbred, but there you have it. This mating system has an interesting consequence for optimal sex ratio choice. If all of your children are mating with your own children, then it turns out the best sex ratio strategy is to have almost entirely female children, and just a couple of males that can fertilize them all. That way, you have the most possible opportunities for grandchildren. This is, in fact, what this wasp does -- it can control the male-to-female ratio of its broods, and it prefers to lay broods with lots and lots of females. That changes if the wasp lays a brood in a caterpillar that already has another set of eggs in it. In this case, the wasp's male children have to compete with the first mother's (few) male children. The payoff for having males is suddenly higher, because it increases the chances of fertilizing all the copious numbers of females that will be around, which is really efficient. The second wasp will lay a brood with a higher ratio of males to females. As more and more wasps lay their eggs in the same food source, the ratio of males increases, eventually approaching 50%. Amazingly (or, perhaps, quite expectedly), you can calculate the game-theoretic optimal ratio of males in a brood for any number of previous broods layed in the same caterpillar, and the behavior of this wasp matches the theoretical results quite well.

October 06, 2016 at 04:01AM

Today I Learned: 1) There is a limit, called the diffraction limit, on how small a thing you can see using light of a given wavelength. Today I learned that the diffraction limit only applies at focal distances greater than a couple of wavelengths. So if you could build a lens and camera less than a few hundred nanometers across, you could, in principle, build an optical microscope that could see things below the diffraction limit for visible light. Except not really, because to do so would require materials with negative and/or imaginary refractive indices, for reasons I do not understand. But you *can* build metamaterial lenses for longer wavelengths, like radio. 2) DNA bases, in the usual narrative, pair beacuse of hydrogen bonding between bases that sort of fit together. That's not really true, exactly -- most (order of magnitude 50%) of the energy in a base pair is actually in stacking bonds between adjacent bases (they have some sort of favorable shared pi-bond between aromatic rings). The base pairing works largely because when two bases don't sort of fit together, they physically bump into each other and mess up the structure required to get the benefit of base stacking. Something I'd idly wondered about was why you can't get relatively good bonding between pyrimidines (Ts, Cs, and, in RNA, Us), which are much smaller than purines (As and Gs). They're small, so they shouldn't clash with each other, right? Today I learned a plausible explanation, which is that pyrimidines don't actually contribute much, if at all, to base stacking -- it's the second aromatic ring on the larger purines that actually makes the base stacking interaction, so every base pair needs a purine to "work". 3) One of the well-known (in the business world) places where growing businesses fail is the so-called "Chasm". The chasm is the gap between a company that can produce a product in small volume for early adopters and a company that sells to the mass market. Apparently it's quite common for a product to get really enthusiastic support early on from a small pool of early adopters, only to be completely ignored by the vast majority of consumers once the company tries to scale up. On a similar note, economy of scale doesn't always apply. Service-oriented industries, or other industries where a large amount of human intervention is required, are a good example.

October 05, 2016 at 02:03AM

Today I Learned: 1) So, starfish may not be radially symmetric after all -- one of a starfish's arms always has a higher density of nerves, and it tends to favor that arm over the others. Arguably, it is actually a head. Today I learned (although apparently not for the first time?) that if the head arm of a starfish is cut off, it can shift that functionality to another arm! 2) We have some delightful printable labels for labeling tubes (and other things) in our lab. They're particularly nice because they tolerate cold well, which is important for labeling tubes that are going to be stored at -20°C or -80°C for a long time. Today I learned that though they are quite cold-tolerant, they are not particularly water-tolerant, and care should be taken not to get the adhesive wet before freezing them down. 3) Fire spreads significantly more quickly uphill. I guess that makes sense, because uphill is for hot air kind of like downhill is for water.

October 04, 2016 at 02:25AM

Today I Learned: 1) Qiagen midiprep kits* come in at least two varieties, which use mostly the same reagents but different columns. I also learned that you can buy columns, which are, as far as I can tell, by far the limiting reagent in the kit. That makes buying midis much, much cheaper. *these are kits for extracting plasmid DNA from medium-sized numbers of bacterial cells. For small numbers of bacterial cells, you use a miniprep kit; for large numbers of bacterial cells, you use a maxiprep kit. 2) A yearly subscription of Asimov, widely considered the best magazine in short-form science fiction by a fair margin, costs less than $40. Moreover, you can get a pack of old magazines at $15 for 12 magazines. Not to sound too much like an ad here, but I'm rather surprised how cheap sci-fi short stories are if you're not buying them in book form. 3) The tracrRNA in the CRISPR system (which is the bit of RNA that is recognized by Cas9 and causes an associated gRNA to be loaded) has to have the right sequence, not just the right secondary structure. With a few exceptions, chainging the sequence in a structure-preserving way destroys the function of the tracrRNA.

October 03, 2016 at 02:00AM

Today I Learned: 1) Some games that look at first blush like prisoner dilemma games can be solved by agreeing to alternately cooperate and defect, basically taking turns exploiting each other. If the payoff matrices are right, you can make more money trading off like that than you can by cooperating all the time. 2) The Lotka-Volterra equation, which describes population dynamics for a simple predator-prey model, is mathematically identical to the replicator equation describing evolutionary dynamics of replicators with different frequency-dependent strategies. 3) There are, in addition to vacuuming robots, swiffering robots and mopping robots. I hear they're not very effective (so says Andrey Shur).

October 01, 2016 at 12:47AM

Today I Learned: 1) There is a style of restaurant called an automat which is essentially a giant vending machine, for food. They were apparently fairly common until the 70s? They died off primarily because a) fast food restaurants offered more flexibility and competed them into the ground, and b) inflation made it no longer feasible for customers to pay in coins, which is all most automats were set up to take (at least in the US). 2) Vacuuming robots can suck up a surprising amount of dirt. 3) CcdB is a gene coding an antibacterial. Today I learned how the ccdB protein works. It's an inhibitor of DNA gyrase, which is a protein that helps relax supercoils in DNA during replication. If all it did was inhibit DNA gyrase, that would be pretty bad, but it's actually much nastier -- the ccdB/gyrase complex can still function halfway, which involves snipping open one strand of the DNA helix and letting it unwind. It just can't stitch it back together, so ccdB turns DNA gyrase into a genome fragmentation machine.

September 30, 2016 at 02:38AM

Today I Learned: 1) ...about Valeria Lukyanova, colloquially known as "The Human Barbie". For a while, she dedicated a significant fraction of her life to immitating the physical appearance of a barbie doll. With her body. She did a pretty decent job, too -- through some combination of extreme dieting and possibly surgery (though she denies the surgery bit), she managed to get her proportions about right. She also applies a ridiculous amount of makeup for a pretty spectacular effect. I'm really torn about this case. On the one hand, as a general supporter of transhumanism, I applaud the use of the body for personal expression and the willingness to venture outside human body norms, even for purely aesthetic purpose. On the other hand... of the entire space of possible bodies, she went with *barbie*?!?! That's about the worst possible option I could have thought of. It's kind of pathetic, in my opinion. 2) Simple amplitude modulation (as in, signal encoding) is inefficient in terms of bandwidth. A naïve amplitude modulation scheme will use about twice the bandwidth of the baseband. There are, however, tricks you can use to cut this down. One, whose name I learned earlier today but have forgotten, makes use of symmetry in the Fourier transform of the signal -- since the Fourier of the signal is symmetric around some frequency, you can cut it down by only sending one half of the signal (in frequency space). 3) SSH communication can use public/private key pairs to authenticate a user. Instead of sending a host a password, you can essentially send them proof that it's you with a set of public and private keys you share with the server ahead of time. I don't actually know what the authentication algorithm is, but I imagine it goes something like this: the server sends you a secret, encrypted with the server's private key; you decrypt with the server's public key, ensuring that the secret came from the server; now you encrypt the secret again with your private key and send it back; the server decrypts with your public key, which you gave it in a previous transaction; if the decrypted secret matches the one it sent out, then it knows it's you and it knows you know it's it, and it begins a handshake protocol to open a secure connection. Today I learned that the above authentication is just that -- authentication. The public/private key pair is *not* used to encrypt any subsequent information -- that's all done the same way as in a password-authenticated session.

September 29, 2016 at 03:29AM

Today I Learned: 1) When shipping stuff on dry ice, you apparently need between 5 and 10 lbs of dry ice per day of shipping to keep it cold. 2) Agarose gels don't actually polymerize when they cool -- it's actually a gel of agarose, which is itself a long-chain polysaccharide. Agarose crystal is actually also a gel, sort of. It's a lot of chains cross-linked by hydrogen bonds, at least. Those cross-links stick around in solution, but heating an agarose solution breaks down the hydrogen cross-links, and cooling it down again lets them re-form... but this time, in a large, complete gel. For all the details (and a few details on how polyacrylamide gels work, which *are* polymerized), see http://ift.tt/2dmuaMN, courtesy of Anders Knight. 3) Webcams are considerably cheaper than I expected. You can get cheap USB ones on Amazon for about $20 without really looking hard.

September 28, 2016 at 03:32AM

Today I Learned: 1) ...how high-performance chromatography, like high-performance liquid chromatography (HPLC) and gas chromatography (GC) and other fancy methods like supercritical fluid chromatography (SFC). Here's what I knew: Chromatography is similar, in the most basic principles, to separating components of ink by spotting it on paper. A chromatography setup has a column with some kind of binding material (usually called the solid phase), over which you flow a sample (the liquid or gas phase) containing multiple compounds that you want to separate. Because different components in the liquid phase will bind more or less stongly to the solid phase, they move through the column less or more quickly, respectively. This causes them to come out the other end of the column at different times, so by catching what comes out at different times, you can collect different components. (You can also hook a chromatograph directly to a mass-spec to get really clean characterization of complex mixtures.) Here's what I learned: Chromatography is *not* like an electrophoretic gel, where you just flow a sample through and the more it binds, the longer it takes to come out the other end. Actually, whatever your chemicals-of-interest are are usually calibrated to bind really strongly to your column, at least initially! Your compound of interest, and possibly some other contaminants, will bind to the column, but lots of other stuff will wash through. The way you get the compound(s) of interest off the column is by slowly changing what kind of liquid you wash over the column (the buffer). As the buffer composition changes, it changes how well your compound sticks to the column, and at some critical point, your compound will flow off and you can collect it. For instance, nickel columns are used to collect His-tagged proteins*, because His tags stick to nickel pretty well. If you flow a mix of proteins with some his-tagged proteins (say, a cell lysate containing the tagged protein), then the his-tagged proteins will stick to the nickel column. Once all the excess proteins have washed through, you start to slowly add imidizole to the buffer on the column. His-tags are good at binding to nickel, but imidizole is *really* good at binding to nickel. As the imidizole concentration increases, it eventually starts to kick off the his-tagged proteins, and at some critical point, most of the his-tagged protein goes back into solution and flows off the column to be collected. Thanks to Anders Knight for a solid explanation of chromatography! * a His-tag is a bunch of histidine amino acids tacked onto the end of a protein, usually to make it easier to isolate. 2) The song "Barret's Privateers", which is a truly delightful, if somewhat depressing, classic sea shanty (might I recommend this recording by Stan Rogers? http://ift.tt/2dC1rUE) is actually a modern piece written by the selfsame Stan Rogers in the 70s. I would not have guessed that from listening. 3) Well, Elon Musk just released some new information on how he plans to get people to Mars (and beyond, if travellers are interested). I didn't read too much on the details, but basically it's a giant (*really* giant) two-stage reusable rocket. The rocket first takes a capsule containing crew and cargo to low Earth orbit and then falls back to Earth. It's hitched to a fuel container, launched *back* up into orbit to meet the capsule, and delivers the fuel that will get the capsule to Mars. Then the rocket falls back to Earth a second time to be refitted for another launch. The capsule jets away to Mars, using a solar sail for thrust in addition to the initial fuel consumption (and presumably a decelleration burn at the end? Can any Kerbal players fill me in on this bit?). The reusable rocket makes the trip relatively cheap -- Musk is estimating $500,000 per passenger for the initial flight, with costs potentially falling as low as $100,000 per passenger. The catch is that the initial capital investment required to build the rockets isn't trivial. Musk is estimating $10 billion, and he's not known for making conservative estimates. That's... really, really, *really* outside of SpaceX's price range. It would almost certainly require government money, in a sort of space-race-style project to get people to the moon. In that sense, Musk has just proposed a massive potential public project, rather than a company plan. Now, let's put that in perspective. That $10 billion will be spread out over many years. Musk's most optimistic guess is that we could have men on Mars in 2025. That's the *most optimistic* scenario, but it would spread the investment cost over something like 10 years. Really, though, I would guess that the capital investment will be pretty heavily front-loaded, and I'm also going to guess that it's going to take longer than 10 years, so let's say $2 billion a year for a while. That's about $6 per person per year (there are a lot of humans). How much is that, in terms of other things in our budget? In terms of science, a $2 billion a year is pretty big, but not overwhelmingly so. That's about half the budget of the National Science Foundation, which accounts for a huge fraction of scientific funding in the US. It's only a tenth or so of the budget of the NIH, though, and that's seen as worthwhile, so maybe the NIH could pivot massively and get us into space? But let's be real, science isn't the *first* thing to get cut when creating a new project. That honor belongs to education. The Department of Education received $77.4 billion from the federal government in 2012 (actually up a fair bit since 2010!), so we could get there with a ~3.5% cut to education for a decade, paying no more in taxes. Or, you know, we could cut military spending by a third of a percent.

September 27, 2016 at 03:14AM

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September 26, 2016 at 04:06AM

Today I Learned: 1) Most genes in yeast are kept at more or less constant levels of abundance throughout the cell cycle. Presumably the same is true for many other organisms? 2) How many Americans can play the piano? Google has no easy answers for this. The best I've found is a rather sketchy, badly-cited set of estimates from a Google Answers thread estimating between 1 million and 20 million (http://ift.tt/2cvFe5D). I *have* confirmed that about 12,000 grand pianos, about the same number of uprights and digitals, and about a million electric keyboards are sold each year in the US. Now those are some hard numbers to use to estimate total numbers of piano players, but it gives you some sense of the scale of piano usage in the US. 3) Wintermelon looks like a strange cross of honeydew and cantalope. It is not. Do not be fooled. It is actually a huge, fleshy, juicy melon that tastes roughly like the pith of watermelon, and is eaten more in soups and stir frys than on its on.

September 25, 2016 at 03:17AM

Today I Learned: 1) For a simple model of genome evolution, there is a critical mutation rate above which a species cannot maintain selective traits. The intuition is that it is much easier to mutate away from a specific genome than it is to mutate back to it, so if the overall mutation rate is high enough, it can overwhelm any selective advantage of the most-fit genome -- even if the most-fit genome has more offspring, too many will be less-fit mutants for that fitness advantage to matter. The transition is, at least for very sharply peaked fitness peaks, an abrupt phase-change. Below that mutation rate, the species will maintain a stable equilibrium of variants spread around the peak, centered on the peak. Above the threshold, adaptation more or less completely breaks down, and the species will explode in genetic diversity. The critical mutation rate threshold is, moreover, proportional to 1/N, where N is the genome length -- the larger the genome, the less mutation it can tolerate before becoming essentially unstable over multiple generations. I'd heard this idea before (that small genomes are in some sense more tolerant to mutations). Today I saw the math behind it. I won't go into it here, but suffice it to say that it's pretty simple, and pretty simplified. I also learned today that the critical mutation rate turns out to be close to 1 mutation per genome per generation, and it turns out that many species (dare I say most?) do fall under the regime of <1 mutation/genome/generation. Also, today I learned of an interesting side effect of the above stuff -- the mutation rate threshold is bigger for more broadly-distributed peaks in fitness space. That means that if there are two peaks in fitness space, with one very sharp and tall and the other less fit but broader, then a species with moderate mutation rate may actually gravitate to the broad, shorter peak instead of optimizing for global maximum fitness. I find that very satisfying, because it's a very formal way of thinking about "evolutionary robustness", which comes up fairly frequently in conversation about biology but is a little hard to justify intuitively. 2) Related to the above, think about how you would guess the following organisms rank in terms of mutation rate per genome *per generation*: human RNA viruses; bacteriophages; E. coli; yeast; fruit fly; mouse; human. Which do you think has the highest per-generation mutation rate? If you guessed "mouse", you're close -- estimates put mouse per-generation mutation rates at about 1/2 a mutation per genome per generation. But the highest rates in the above list belong to lytic RNA viruses. The table I'm reading from has per-generation mutation rates between 0.84 and 6.5, which is shocking above the critical mutation rate mentioned before. Which do you think has the lowest per-generation mutation rate? It's bacteriophages. Turns out that with the glaring exception of RNA viruses, the per-genome mutation rate is dominated by genomic size. Bacteriophages have relatively high per-base mutation rates (1,000-10,000 times higher than humans) but their tiny size means that their per-*genome* mutation rate is quite low (around 0.004/generation). 3) The shape of the clitoris (which, in case you don't know, is a much larger organ than it appears from the outside, and extends around much of the vagina) was discovered fairly recently. See this *1998* paper descibing the first modern dissection of the clitoris: http://ift.tt/2d0Bvzb. Here's the really obnoxious bit -- the shape of the clitoris *was* well known before the 20th century. Early versions of Grey's Anatomy included pretty accurate anatomical structures of the clitoris. Later versions, and virtually all other medical literature and textbooks, simply omitted them until fairly recently.

September 24, 2016 at 04:13AM

Today I Learned: 1) There are no common genotyping tests to determine suitibility of a cancer patient for radiation therapy. This is starkly different from chemotherapies, for which there are many genetic tests to predict safety and efficacy of the chemotherapy. It's not entirely clear why radiation therapy hasn't benefited from genetic testing the same way chemotherapy has, but it may simply be because radiation therapy scientsts tend to gravitate towards technological innovations for delivering radiation in more controlled, more precise, more measured ways. 2) We (meaning a bunch of scientists at Heidelberg) just discovered the molecular sensor that the human body (well, mouse body, but probably also the human body) uses to detect when a fever is high and when to shut it down. It's a temperature-sensitive ion channel called TRPM2 (Transient Receptor Potential Member 2). There are lots of other members of the TRP family, which are sensitive to different temperature ranges and are expressed in different places. TRPM2 is active in the preoptic area (POA) of the hypothalamus, which is a little bit of the brain responsible for tracking core body temperature and adjusting it in response to inflammatory signals. 3) iGEM will accept plasmids that aren't Biobrick compatible, though they won't count towards medal requirements.

September 23, 2016 at 03:39AM

Today I Learned: 1) ...that default ssh settings are really shockingly insecure. If I read those guides correctly, when you send your password when logging in, it sends it in plaintext! Key-pair login is much more secure -- that way you never have to send a password, and the server doesn't need to know a password (aside from the user's public key). 2) Fan death (the idea that running a fan in a closed room overnight can kill you) is, in fact, still believed in South Korea, though not as much among the young (if you believe an uncited sentence on Wiki). Moreover, Korean news agencies report cases of "fan death" relatively frequently (a couple of times each year). MOREOVER, the Korea Consumer Protection Board (a government-funded public agency) warns about fan death and states in no uncertain terms that direct use of a fan indoors can raise the risk of death by asphyxiation due to "[an] increase of carbon dioxide saturation concentration [sic] and decrease of oxygen concentration". 3) Speaking of ridiculous ideas, when Benjamin Franklin invented the lightning rod, Americans were hesitant to employ them. Why? Because lightning was believed to be primarily an act of God's righteous anger, and therefore carried a heck of a lot of heavenly power. Using a lightning rod to transfer that electric/dietical power to the ground would, obviously, supercharge the ground and make things like lightning more likely. I'm not making this up. http://ift.tt/2cq3JB0 The less on of the day is that a lot of things people know are complete and utter falsehoods. Use data. Experiment. Draw on the collective experience of the scientific community, at least when *it* uses data and experiments.

September 22, 2016 at 01:26AM

Today I Learned: 1) Korean has two ways of counting! It has one set of words for counting objects, as in "one tree, two trees, three trees", etc. It has another set of words for the mathematical objects of numbers, as in something you'd put on a number line. Interestingly, the latter set of numbers sounds *really suspiciously* close to Chinese words for those numbers. 2) Rounded to the nearest thing, I know nothing about the Aztec political system. Today, I read a bit about the Aztec political system, and with it, a bit about Aztec culture. My source is a blog post about a book by Inga Clendinnen, which can be found at http://ift.tt/2cnCszv. I still don't know *much* about Aztec culture or politics, but my new impression is that Aztec civic, political, and religious life was largely based around the production of intense, Carvinal-like communal experiences. If this particular soure is to be trusted (and is correct), the Aztecs were masters of using ritual for effect, and the kinds of religious rituals they underwent on a regular basis were addictive in their intensity and civically justified as critical for the continued function of the world without disaster (i.e., keeping the sun rising and the rain coming without flood). Really, though, I recommend reading the link above -- at this point, I'm giving at least a fifth-hand account. 3) Two Linux console tricks. 1) I finally learned how to access multiple command line prompts on a headless Linux system. 2) When using 'less', you can scroll sideways with the sideways arrow keys.

September 20, 2016 at 12:31AM

Today I Learned: 1) The Beatles were so ahead of their time that they quit performing live because their equipment couldn't handle the crowds. There didn't exist commercial speakers that could play reasonably well over the roar of the kinds of crowds the Beatles routinely generated. At some point, they decided that there was no point in playing live, because nobody could hear their music anyway. That was when they started devoting themselves full-time to studio recording. 2) ...proper application of a chop (the Asian style seal/signature). If you press it with a hard backing behind the paper, it doesn't apply very well (imperfections in the chop surface show up really strongly). A soft backing works much better, like a folded paper towel. 3) Very important cable management trick for serious cabling situations -- label both ends of the cable with a unique number, with a nice tape that won't come off or gunk up. That way you shouldn't ever have to go manually tracing a wire through a thick bundle of cables.

September 19, 2016 at 03:08AM

Today I Learned: 1) Hardy, of the Hardy-Weinberg equilibrium, was yet another example of a mathematician who was proud to never work on anything practically useful, but ended up being famous for deriving very practiacal, applied mathematics. 2) Single-population, two-allele evolutionary dynamics seem pretty simple at first blush. If the populations are big enough that genetic drift isn't a problem, then the one with the higher fitness grows in the population until the other one doesn't. Today I learned that that's only true if population growth is exponential, i.e. the rate of reproduction of each population is exactly proportional to the size of that population. If the rate of growth is *slower* than exponential, then there is a stable equilibrium between the two populations where both can coexist. If the rate of growth is *faster* than exponential, then fitness is actually more or less irrelevant -- there is an unstable nonzero equilibrium between the two species, and whichever species starts with a larger population than it has at that equilibrium will dominate regardless of the relative fitness of the two populations. When would you encounter sub- or super-exponential growth in a population? A nonreproducing population with immigration would be an example of subexponential growth -- there, population growth is entirely determined by a (potentially) constant immigration. A mix of reproduction and immigration also can result in subexponential population growth. An example would the release of sterile insect populations into the wild, which is done to bring down wild pest populations. Superexponential growth happens any time two organisms have to find each other to mate, as in sexually reproducing species -- the denser the population, the more likely it is that each individual reproduces, and the faster overall population growth. 3) I read a claim today that the terms transcription and translation (as in, transcription of RNA from DNA and translation of RNA into protein) were coined by John von Neumann, to refer to processes in an abstract self-replicating automata schema he had theorized. There wasn't a citation given, but context clues suggest that the term was, as I say, coined in "Theory of Self-Reproducing Automata", a classic 1966 work on, well, self-reproducing automata* **. Well, I read through a chapter (chapter 4: http://ift.tt/2cJdGxl) of that book looking for references to transcription and translation before realizing that I was just reading a chapter excerpted from a bit of a longer work than I wanted to read in one Sunday afternoon. In any case, I didn't see any reference to transcription and translation exactly, though it *did* contain a theoretical description of abstract machinery surprisingly like the transcriptional machinery of the cell... not surprising, since it was inspired by the same (although it was written before most of the details of either transcription or translation had been worked out, so there are some telling differences among the similarities). I eventually found a text version of the book (link available here, along with a bunch of other formats: http://ift.tt/2d9SVt4) and ctrl+f'ed for "transcrip" and "transl", and there was nothing quite resembling transcription and translation in the biological sense. Phoey. Would've been a great story. In any case, von Neumann is great. Go check out his works. The chapter linked above has, among other things, a really nice succinct little comparison of brains, computers, and theoretical thermodynamic limits. If you're interested in computation, this is a must-read. * Ever heard of a von Neumann machine? This is the book that defined it. ** I'm not sure if von Neumann actually penned anything in that book. It's "edited and completed" by Arthur W. Burks. What I read of it reads as a sort of "best of" compilation of von Neumann's best lectures, interspersed with some commentary and summarization by Burks.

September 17, 2016 at 04:41AM

Today I Learned: 1) Two transcriptional elongation factors called GreA and Greb are very, very important for efficient transcription in E.-coli-based* transcriptional systems. Addition of GreA and GreB to a minimal in vitro transcription/translation system (PURE express) increased yield about 6-fold, which brings them much, much closer to the kinds of yields we regularly get out of TX-TL. * anyone have a better way to punctuate this? 2) When you assign a computer a new IP address, you may need to release and refresh that computer's IP configuration, which can be done by running ipconfig \release ipconfig \refresh 3) ...a bit about how stocks and public companies work. As I gather, the basic idea of stocks is that it's a way for a company to make a ton of money by selling itself to lots of shareholders who want to invest in a company without shelling out tons of money or getting directly involved with the company in any kind of deep way. When a company "goes public" (which basically means it signs up on some kind of public trading list and legally commits to making a bunch of its financial information public), it gains the ability to sell stocks to whoever wants to buy them. This is great for the company, because it gives them a huge influx of instant cash. It's even better for early investors, because they typically get paid back during the going-public event. Stocks nominally derive their value either from dividends that the stock pays (which are typically single-digit-per-year returns) or from the ability of a stock-owner to vote in certain decisions of the company with a weight proportional to the number of stocks the stock owner owns. In practice, I'm fairly confident that stocks are more like currency than a good -- they have value because everyone believes they have value. Companies can decide to create and sell more stock whenever they want to. When that happens, it can be really bad for investors who already own stock, because a) they suddenly own far less of the controlling share of the company and b) the supply of stock goes up drastically (which I suspect is the bigger effect). However, it can also be really good for investors, because selling stock gives the company a ton of money to work with, which can put them way ahead in the marketplace, which can make their stocks more valuable again. So it's an intricate balance. Another thing companies can do is *split* their stocks, which means they basically declare that everyone who owns stock now owns, say, twice as many stocks with half the value each (or, in general, X times as many stocks with 1/X times the value each). This is apparently really annoying for stockholders, although I don't really know why, but it's nice for the company because it lowers the barrier to purchase a single stock. Google once promised that they would never split their stocks, but they did when their stock reached something like $1000/stock. Warren Buffet also once promised that he would never split his stocks for Berkshire Hathaway, and he has held true to his word -- as of tonight, those stocks go for $218,400 apiece. Thanks to Kevin Cherry for graciously imparting some of his knowledge of stocks and stock trading!

September 16, 2016 at 02:00AM

Today I Learned: 1) A couple of DARPA projects currently listed on their wiki page: bullets designed to penetrate armor by melting and being formed into a spike by a powerful electromagnetic field; wearable jetpacks to increase infantry speed; a mind-controlled robotic arm; a headset that reads and transmits your thoughts in order to communicate covertly; SyNPSE (Systems of Neuromorphic Adaptive Plastic Scalable Electronics -- any idea what that is?); and multiple independent powered exoskeleton projects. 2) There is a small but awesome subculture of DIY drivers who make and drive mono-wheel bikes. I'm not talking about motorcycles with one wheel (though those exist too, apparently!), I'm talking about one giant wheel that you sit inside, like the thing General Greivous rides. It's actually two concentric wheels. The inner wheel spins relative to the outer one, and the weight of the motor pushes the assembly forward. There are some serious desgin problems with the mono-wheel bike. The most egregious is probably the braking system. Traditional braking systems don't really work, so you have to brake with your feet. On the road. You'll want to wear some tough boots if you try that. They also require some work to balance, especially since you usually have to bend out sideways to see around the wheel. The owner* of one particularly beautiful mono-wheel bike described the experience of riding it as "more like flying than anything else" -- the seat kind of floats around the inside of the outer wheel, so you don't feel particularly grounded. * extremely charming man, at least on video. He seemed the happiest man in the world on that thing. "It never fails to put a smile on people's faces", he said repeatedly. 3) Spices are *even cheaper than I thought* from the Mexican section of a typical supermarket. I've always known they were cheap, but... well, today I bought some coriander seeds from the Mexican section. A little baggie was about 1/8 the cost of a shaker full of coriander seeds, although the baggie was smaller. ...or so I thought! Turns out the baggies just *look* smaller -- the contents of one baggie fit almost exactly into a (used) coriander seed shaker, so really they're just 1/8 the price.

September 15, 2016 at 02:31AM

Today I Learned: 1) Gough Island, a South Pacific island known for being the sole breeding site of the Tristan albatross, has a surprising invasive species -- the house mouse. Mice were introduced to the island by ships *relatively* recently, though I don't know whether that's a few decades ago or a few hundred years ago. The mice have no predators on the island... and the albatross has absolutely no defenses against them. That's right, defenses. Against the house mouse. See, Gouhg Island mice have evolved to be much bigger than normal house mice, and have switched from an herbivorous diet to a diet of albatross chicks. The albatrosses are much, much bigger than the mice, but predatory mice can squeak in, nip off a little bit of flesh, and leave before the chick can do anything about it. Over the course of a night, a swarm of mice will nibble the bird to death. This is a serious problem for the albatrosses of the island, and has set their numbers in decline. Time will tell whether they can evolve a defense quickly enough to survive. 2) You can break a zip tie with a shoestring. Citation: http://ift.tt/2d0PeJ1 Ripped from Kitty Mayor's facebook post a couple hours ago. 3) ...about an art project called Forms in Nature*. It's basically a really, really beautiful series of ceiling light covers shaped like a mad, zero-G circulatory system, designed to cast shadows that make the room look like a dimly-lit forest. The pieces are each unique and algorithm-designed, then custom 3D-printed out of a nicely heat-resistant plastic and hand-assembled. Every one of the forms is a an exclusive experience... and they're priced accordingly, at something like $3,500/piece. You know what, though? That description really doesn't do it justice. Just go check out their webpage: formsinnature.dk *though to be honest, it's almost certainly not the only art project with that name....

September 14, 2016 at 01:54AM

Today I Learned: 1) Our autoclave will, in fact, open if it isn't finished with its cycle. Wasn't even that bad -- I didn't notice anything was wrong until I'd already taken out a bottle. 2) Metal prints are the most beautiful way to get an art print. Also one of the most expensive ways. Sadly, computer screens do not give this point justice -- you're going to have to find some yourself to really see what I mean. 3) Speaking of amazingly beautiful things, check out the red beach, in Panjin, China. It's a huge marsh dominated by a brilliant red species of alkaline-tolerant reed. It is also the site of one of the largest (wiki claims *the* largest) wetland preserves in the world.

September 13, 2016 at 02:43AM

Today I Learned: 1) Ever heard of a Nash Equilibrium? Informally, it says that in any game (economist-speak for an interaction between two or more parties where different outcomes have different values) satisfying certain conditions, there is a stable set of strategies that the players could arrive to for which no player would gain by switching strategies. There is no guarantee that the equilibrium is *good* for all, or even any, of the players, nor that the players will actually arrive at that equilibrium (even if they play perfectly rationally), but an equilibrium definitely exists. Today I learned a semi-formal set of conditions under which the Nash Equilibrium Theorem holds. It holds with a game of any finite number of perfectly rational players, where each player has a finite set of "pure strategies" that can be mixed probabilistically (i.e., a voter on a committee might vote for proposition A, proposition B, or proposition A with 10% probability and proposition B with 90% probability, or any other combination of probabilities). And... that's about it. The choice of strategies can, as far as I understand, be arbitrarily complex, as long as the decision ends up being some probabilistic combination of pure strategies. That's a shockingly powerful theorem, if you ask me. Thanks to George Artavanis for presenting about, among other things, Nash Equilibria. 2) John Wilkins, the 18th century natural philosopher, tried to write a universal language capable of communicating any thought in a clear fashion. I'd read a little bit about this scheme in Neil Stephenson's "Quicksilver", but today I learned a few more details about it. The universal language was motivated as a replacement lingua franca for latin -- something traders and diplomats could speak in any language. It was to be developed roughly in two parts -- a "real character" set and a "philosophical language". The real characters were to be a system for generating written characters that could representing any idea, in an abstract, non-verbal way (kind of like the way chinese writing acts as a non-verbal medium for speakers of different dialects). The philosophical language was, in some sense, a mapping from the real characters to spoken word. In general, the philosophic language was structured so that each additional character in a word would narrow down the meaning of the word, in some systematic way -- for example, "be" might be the word for machines, "ben" might be the word for electronic machines, "beni" might be the word for computers, "benit" might be the word for desktop computers, and so forth. The universal language was met with great excitement when it was first announced, but as you can probably guess, it never really went anywhere. 3) It turns out that there *is* a rule describing how adjectives are arranged in English! Ever noticed how you can have a big red ball, but a red big ball sounds strange? I've been wondering what rules define what order adjectives come in for a while now, and while it seemed that there were some generalizations about things like color coming after size, I never found a complete set of rules. It turns out there is one! It's not even that complicated! According to one Mark Forsyth (not the W&M one), The rule is that adjectives must come in the order "opinion-size-age-shape-color-origin-material-purpose noun". A complete example he gives is a lovely old rectangular green French silver whittling knife. Now, the question is, how the heck do we all learn this rule without ever actually learning *about* it? Thanks to Mengsha Gong for finally bringing me some peace on this subject!

September 12, 2016 at 04:55AM

Today I Learned: 1) A thymister is an electronic component kind of like a transistor, except that the output is either on or off -- instead of amplifying current like a transistor, a thymister acts as a switch. 2) It has been observed since the 60s that the children of holocaust survivors are more prone to PTSD, and suffer more severe PTSD, than the rest of the population. This has been confirmed over and over again, but there's no solid known mechanism. Recently, there's been a fair amount of somewhat fringe science on transgenerational epigenetic changes in response to stress, which has been hypothesized as one explanation. Jury's still out, as far as I'm concerned. 3) ...how to install a window AC! It's really pretty easy, although a little more difficult if you have a vertical window....

September 10, 2016 at 02:35AM

Today I Learned: 1) Here's an interesting little fact concerning the politics and game theory of global warming, as pointed out by George Artavanis. Although the usual proposed mechanism for stopping or slowing global warming is to cut greenhouse gas emissions, there are other, technologically feasible ways to stop global warming and potentially even reverse it. Fueling blooms of oceanic plankton is one way. Another would be to release or seed large amounts of sulfur gas into the atmosphere to generate cloud cover. Those techniques are fairly likely to work, and they're actually pretty cheap to implement -- the only problem is that we don't know what kind of side effects they could have, and pushing back too hard on global warming could potentially be just as catastrophic as making it happen in the first place. So, pretend you are the head of government of some small island nation. Perhaps an island nation that is literally going to sink into the ocean if global warming proceeds. The other nations of the world aren't doing what it's going to take to stop global warming. Suddenly, it sure looks like it's in your best interests to seed the atmosphere and start cooling down the planet! If you get a mini ice age for your trouble? Not a problem! That will only really affect Europe and North America. And so, here is one additional little incentive for the big countries to come up with a good solution to global warming -- if they don't, some little country is going to deploy a really, really bad one. 2) Also from George Artavanis, a game theoretic term called "salami tactics". Salami tactics are a method of undermining threats of sanctions (or nastier things, like nuclear war) by "slicing" out little pieces at a time. You start by violating some agreement just a tiiiiny bit -- enough that you get something, but small enough that nobody is willing to engage in costly sanctions to punish you. Then you escalate just a little bit more. Then just a little bit more. At every step, it's really, really hard for the other side to justify hurting themselves a lot just to punish you. The name comes from the way you're slicing away bits of your agreement, like slicing off pieces of salami. I really can't get over that name. 3) There is at least one library of yeast clones with GFP tags of every gene. Each clone has GFP attached to one protein-coding gene, so if you want to know how much of some gene is expressed under some condition, you just pick out the right clone, grow it up, put it in the condition you're interested in, and see how much it glows. This fact brought to you by Andy Halleran.

September 09, 2016 at 12:57AM

Today I Learned: 1) A radio galaxy is a galaxy that emits a lot of light from synchrotron radiation. Synchrotron radiation is light emitted by electrons that are accellerated radially through a magnetic field. I'm not entirely clear on what causes synhrotron radiation in galaxies, but certain galaxies make a lot of it. Radio galaxies get their name because synchrotron radiation is primarily radio-frequency, although it does extend up through and past the visible range of the spectrum as well. 2) Back in 2006, NASA launched a radio telescope called ARCADE to the edge of space using a balloon. There are plenty of radio telescopes on the ground, but they work by comparing one pixel of the sky against another nearby pixel, and look for contrast. Among other things, ARCADE was sensitive enough, or otherwise had the right equipment, to measure absolute radio intensity. What ARCADE discovered is the Space Roar -- all of space appears to be lit up with about six times the radio noise that anybody had expected. We still do not know where the Space Roar comes from. 3) Tor, which stands for "The Onion Router", is a system of anonymous information routing via the internet. It is so named because it makes use of onion routing, which is a technique for preserving anonymity where a message has multiple layers of encryption, like an onion, that are sequentially decrypted by successive network nodes. Because of the method of encryption, each node can only decrypt its layer, which means it only knows where it received the packet from and where it should send the packet, but not anything further upstream or downstream, making it very difficult to trace where packets come from or go to. Surprisingly, at least to me, onion routing was developed *and patented* by the US Naval Research Laboratory. A couple of researchers at the NRL developed Tor and arranged for it to be released with a free license, and later split off to found The Tor Project, a non-profit organization that now manages and develops Tor.

September 07, 2016 at 11:54PM

Today I Learned: 1) A dead tree, caught on another dead tree, creaking while blowing around in the wind, sounds surprisingly like a bleating elk, or perhaps a young bear. 2) Sweetened aloe juice (which tastes like fruity sugar water) is considerably better than raw aloe juice (which tastes like battery acid). The little aloe chunks that come in it are also quite tasty. Relatedly, Lychee juice tastes just like lychee jelly cups. Thanks to Sarah Seid for finding these things to try! 3) Bitcoin miners aren't searching for new bitcoins, or at least that's not their primary function in the bitcoin economy -- they are actually public ledger-writers, which store publically-available transaction records involving bitcoins ("blocks") in a heavily-distributed network of such transactions ("block chains"). Transactions are verified by consensus of the miners. Miners are rewarded for creating blocks with a small number of bitcoins. Creating a block is intentionally computationally intensive to keep the supply of bitcoins relatively stable. I also learned how to make something like writing a block computationally intensive. Bitcoin miners are required to include a "proof of work" in any block they publish. A simplified explanation of the proof of work is that it's a modification to the block which makes it hash to a small value using RSA or another hash (i.e., it hashes to something starting with a bunch of 0s). This is computationally intensive -- the only known way to find such modificaitons is to try variations until one works. Verifying that the work has been done is quite easy, though -- you just apply the modification, hash the modified block, and see if it starts with enough 0s.

September 07, 2016 at 11:53PM

Yesterday I Learned: 1) ...how to play a dulcimer, at least in the broadest possible outlines. Dulcimers have four strings -- a tonic string (brass-wrapped), a string a fifth above it, and a pair of strings each an octive above the tonic (two strings so that the volumes match). The simplest/standard way to play is to hold down chords on the frets and strum out chords, but you can also leave the bottom two open as a drone and just move around on the top two notes as melody. Thanks to Sarah Seid for teaching me! 2) There is such a thing as vegan sour cream, and it can actually be used to make a passable vegan tzatziki, but it really seems closer to heavily-whipped cream cheese in consistency and flavor. I haven't tried it on toasted bagel yet, but I really want to. 3) ...the tastes of pure citric acid, tartaric acid, and malic acid in water. Malic acid tastes like the tartness in an un-ripe blackberry. Tartaric acid tastes like the sourness in some grapes, and a bit like limes. Citric acid... is sour. You've all tasted it -- it's all over candies and drinks of all kinds and a surprising number of other foods. Thanks again to Travis Blount-Elliott

September 07, 2016 at 11:53PM

Two Days Ago I Learned: 1) Paddlefish. Go Google Image search them. Now, some basic background. Paddlefish are considered something of a "living fossil" -- they've been around for a very long time (late Cretaceous) with very few morphological changes, and they're still around, though struggling a bit. Up until recently, there were two known species, the American Paddlefish and the Chinese Paddlefish. The Chinese species hasn't been seen in the wild for over a decade, and is thought to be extinct. The American Paddlefish is "Vulnerable" -- it's not endangered yet, but it's likely to become endangered soon. I don't know much about why Paddlefish have been doing so poorly lately, but I'd guess it has a lot to do with their size and slow reproductive cycle. They're BIG FISH, which makes them really fun targets for fishermen, and they only bear young every couple of years, not starting until they're something like seven years old. It's pretty sad that we're killing off a family that's been around since the dinosaurs. 2) In a double-blind, randomized taste test of seven different vegan milk alternatives by two people, Trader Joes' original rice milk was the clear winner, oat was clearly the worst, and walnut chocolate milk was really quite good. 3) Meads and beers can be back-sweetened (that is, additional sweetness added after fermentation) with sugar or honey, but you have to add something to stop yeast growth first or it will start to ferment again. Potassium sorbate and potassium metabisulfite are good yeast-inhibitors for this purpose. Credit to Travis Blount-Elliott, who as far as I can tell is a meading wizard.