March 17, 2018 at 05:40AM

Today I learned: 1) The PDF for the Gaussian distribution was discovered something like 80 years before Guass by de Moivre, who wrote it out as part of his treatise on probability "The Doctrine of Chances" (which was apparently written primarily for gamblers?). From what I gather, de Moivre's paper on the normal distribution (which he used as an approximation of a binomial distribution for large numbers of trials(!)) languished in obscurity until well after Gauss formalized the distribution and popularized it. 2) Related: Stigler's Law of Eponymy states that any scientific or mathematical discovery named after a person was not discovered by the person it was named after. This includes Stigler's Law (attributed by Stigler to one Robert K. Merton). 3) On a more sober note, today I learned that lynchings in the US were much, much worse than I thought. I *thought* lynchings were basically public killings with a big crowd. In fact, lynchings were more akin to medieval executions -- that is, the murder part would be preceeded by hours of torture involving things like open flames and removal of body parts.

March 15, 2018 at 03:50AM

Today I learned: 1) You know how gravity falls off with the square of the distance between two objects? As does electromagnetism? That's because we live in three spatial dimensions (for the same reason that the surface area of a 3D sphere increases with the square of its radius). If we lived in 4D space, then forces would fall off with the cube of distance; if we lived in N-D space, forces would fall off to the power of 1/(distance^N). That also means that the inverse-R-squared law is strong evidence that we do, indeed, live in a 3D space, and not, for example, a 3D slice of a higher-dimensional space. Wouldn't that immediately falsify string theory, which posits lots and lots of dimensions? Well... no. There's a caveat to the "forces fall off to the power of 1/(distance^N)" law, which is that it only holds as long as all of the spatial dimensions have the same characteristic length scale. Now, I must admit, I don't fully understand what the "length scale" of a dimension is. Nevertheless, if a dimension is "small", then not much force will leak out into it, and the force falloff will remain very close to the 1/R^2 law. As of 2005, gravity had not been measured to a high enough precision to distinguish between a 1/R^2 falloff and an almost-1/R^2 falloff, leaving room for the possibility of other, smaller dimensions. As far as I know, that fact hasn't changed in the last decade. 2) ...how to return Amazon packages. It's ridiculuosly easy. First, you go to your orders on Amazon, find the thing you want to return, and click some relatively obvious button that says something about returning the item. Follow the instructions. If you can get it to a Kohls or an Amazon locker, they'll package it and label it and ship it to you for free. Otherwise, if you get it to a UPS store, they'll package it, label it, and ship it for some (not always outrageous) application of money. Also, to keep things snappy, if you ask for an item replacement from Amazon, they will immediately ship you the new thing. If you don't return the original item postmarked before some date, they'll automatically charge you for it again. I do wonder if you could abuse this somehow by, say, buying a ton of things at once, ordering up replacements for all of them, then shutting down your Amazon account (or your credit card) before the due date. 3) I somehow got it into my head that you could decompose any linear transformation a rotation and a scaling, possibly with a reflection. I was wrong -- I'm pretty sure scalings *don't* account for shearings, and even including shearings doesn't give you all of the linear transformations. As a side note, I *did* find the conditions under which you *can* write a linear transformation as a rotation plus a scaling -- for a linear transformation with matrix [[a, b], [c, d]], you can do that decomposition iff b = -ac/d. You're welcome? I guess?

March 13, 2018 at 11:45PM

Today I learned: 1) The number line can be thought of as a limit of a circle with increasingly large radius. This is useful for proofs involving the number line, and can get you a factor of pi in sums that otherwise isn't obvious. For more, see https://www.youtube.com/watch?v=d-o3eB9sfls. 2) Synthetic biological circuits break. A lot. Almost all synthetic circuits are bad for the cell they're in, so most mutations that break the circuit will be selected for pretty quickly. One of the most common types of circuit-breaking mutations is accidental insertion by Insertional Sequence (IS) elements, which are small DNA fragments that make transposons, which flip the IS out of whatever DNA it's in and move it somewhere else. Bacterial genomes have lots of IS elements (E. coli has a few dozen, depending on the strain), so any engineering in bacteria will run afoul of them eventually. So. IS elements are common in bacterial genomes, and they mess up biocircuits. Why not remove them from the genome? Well, somebody has -- Scarab Genomics LLC sells a variety of IS-free cell strains for a variety of cloning needs, for the low low price of... actually, I don't know how much they cost. You have to make an account with them and sign in to see prices. More importantly, though, Scarab Genomics has some pretty nasty licencing restrictions on their strains -- they get a cut on any IP you develop using their lines, for example. Not nice. 3) Strong ribosomal binding sites (RBSs) can protect mRNAs against degradation. Probably. This is a pretty new finding, but it looks like if an RNA is covered in ribosomes, the ribosomes can physically block RNAses from binding and degrading the RNA. Strong RBS -> lots of attached ribosomes -> less degradation. The effect is modest, but measurable.

March 13, 2018 at 01:10AM

Today I learned: 1) ...how to replace snap-on buttons! Technically, that's a lie. I looked up how to replace snap-on buttons late last week. But! Today I actually *did* some snap-button replacing, which honestly felt a lot more like learning than watching a video. For the record, the hardest part was removing the old buttons, which wasn't terribly difficult once Andrey Shur provided me with the right tools. 2) One of the most clear-cut problems with the US healthcare system is the use of opt-in organ donation. It's well-known that many, many people who would be fine with donating their organs on death never bother to sign up for organ donation, and lo! We have a chronic, severe shortage of organs for transplantation. It would be SO EASY to switch to an opt-out system where everyone is, by default, signed up for organ donation, and you can fill out a form to not donate if you really want to. This would vastly increase rates of donation, while still giving people the opportunity to not donate if they have any objections serious enough to warrant filling out some paperwork. ...except that it isn't *quite* that clear-cut after all. Opt-out policies *do* correlate with higher rates of donation, but there are opt-out countries with very low donation rates, and Spain, the most widely-cited success story for opt-out policy, has the Very Large Caveat that they implemented a bunch of organ-transplantation-related reforms around the same time as opt-out, which seem to be responsible for a good part of the increased donation rates there. There are also some specific failure modes for opt-out. For example, when Wales switched to an opt-out system, they saw rates of organ donation *decrease* (albeit slightly). A possible reason is that in Wales (and many other countries with opt-out organ donation), the family can still decide to deny access to a deceased organ, so opt-out isn't quite so opt-out as it sounds. Before they switched to opt-out, the family could *also* decide to allow transplantation if the family member wasn't signed up. So really, in both systems, anybody who doesn't bother filling out paperwork to make a decision one way or another is actually at the mercy of their family. In opt-in, there's a way to guarantee that you will donate your organs; in opt-out, there is only a way to guarantee you will *not* donate your organs. Therefore, it's possible that the opt-out system actually creates an extra group of people that don't donate. 3) There is a belief running around that chewing gum is bad for pregnant women. I'm quite skeptical. Some quick googling brought up a bunch of results (with a fairly wide spread of claims), but none from sources I would consider reliable. The only plausible-looking claim, as far as I can tell, is that some gums are sweetened with sorbitol, which is a diuretic and can cause intestinal distress if taken in large quantities. Is that likely to actually be a problem? I'm guessing not.

March 12, 2018 at 03:28AM

Today I Learned: 1) Medieval executioners were almost completely separated from larger society. Firslty, executioning was, like most trades in medieval Europe, familial. Executioners were born into the job, whether they liked it or not. Secondly, executioners were considered kind of magical, kind of blessed, and kind of cursed. Importantly, they had the special ability to remove a person's honor with a touch, like a morbid, adult form of cooties. You're in a marketplace and you accidentally brush up against an executioner? Whoops. You just got infected with the executioner's aura. You are no longer fit for polite society. One side effect of executioner hygeine was that executioners were a bit of an inbred breed -- only the children of executioners were fit to marry an executioner, so their lineages remained separate from most of society. This fact-set courtesy of Dan Carlin's Hardcore History. 2) Henna tattoos are traditional for brides. Didn't know that. 3) The Viking probe we sent to Mars found some evidence for life, although it didn't pan out in the long-term. Viking carried four tests for carbon-based life: a mass spec to directly look for organic compounds, and three experiments that looked for release of compounds of various kinds when nutrients were added to soil samples. One of the release experiments came up strongly positive... but it turned out that the release (in this case, radiolabeled CO2) could be explained quite well by gamma ray irradiation of the sample.

March 11, 2018 at 05:13AM

Today I learned: 1) I'm a big fan of Beethoven, espeically his piano sonatas. I love how beastly they are, how passionate, how ridiculously ahead of their time they are (did you know Beethoven invented boogie-woogie? https://youtu.be/ccyHT1sFmsg?t=1032). Today I learned that Beethoven's sonata no. 23 ("Appassionata") was *so* ahead of its time that it was never performed in public until after Beethoven's death. He played it for some of his colleagues and students (including Czerny), nobody wanted to play it. One critic (often-quoted online, but without citation) called it "incomprehensibly abrupt and dark". From the sound of it, Beethoven's contemporaries couldn't, for the most part, parse it. On a related note, apparently Beethoven never technically bought a piano. All of his were loaned, rented, or gifted by piano manufacturers. Beethoven was famously frustrated with the piano of his time. Pianos of the late 18th and early 19th century were sickly cousins of their modern descendants in a lot of ways. They were smaller both in soundboard size and range, they were more limited in their ability to play repeated notes, and they generally sounded much weaker (compare harpsichords to a modern concert piano). The biggest single advancement in piano technology was the cast-iron frame, which lets modern pianos be strung with absolutely immense tension, and lets you put a ton of kinetic energy into a performance in a quite literal way. Unfortunately, the cast-iron frame was only invented in the last couple of years of Beethoven's life, and he was constantly frustrated by the lack of his pianos' abilities to express what he wanted. He pushed what he had to the limit, though -- the Appassionata, for example, goes all the way to the highest and lowest notes available on his piano at the time. 2) If you're eating a Thai curry and you bite into a chunk of something that looks, tastes, and feels like ginger, odds are it's not ginger. It's probably one of the four varieties of galangal, a ginger-like root used as one of the main ingredients in Thai curry. 3) You can buy oreos in eastern Asia, but they're packaged a little differently -- each oreo is individually wrapped. In fact, single-bite individually-wrapped packages inside a larger package seems to be a common motif of east Asian snack foods.

March 09, 2018 at 08:28PM

Today I learned: 1) According to Harvard professor Johan Paulsson, if you fuse most fluorescent proteins to a protein that naturally multimerizes (that is, a protein that forms a complex of two or more copies of itself), the fluorescent protein attachment will cause the whole protein to clump dramatically. I'd read this before, but misread it slightly and thought that this applied to *any* fluorescent protein fusion. The thinking is that fluorescent proteins normally bind to each other, but only very weakly; however, when two or three or ten of them are all fused to one complex, it acts as a nucleation site for larger-scale aggregation. Citation: http://ift.tt/2HisT4D 2) You know the weird thing in quantum mechanics where particles kind of appear and disappear at random in a kind of quantom froth? Well, there's a way of viewing that phenomena as a consequence of simple formulations of quantum mechanics married to special relativity -- essentially, quantum systems get random spikes in energy, and special relativity says that you can interconvert between matter an energy, so there must be occasional production of particles from random QM fluctuations. According to Anthony Zee, the "marriage of QM with special relativity" is also one of the primary motivations for developing quantum field theory. I don't yet understand this claim, nor why it should be true. 3) Say you're a cell, and you want to make some specific amount of a protein. There are, roughly, two variables you can (dependently) vary to get the right amount of output protein -- transcription speed and translation speed*. For a fixed amount of output, you could have TONS of transcription and a little bit of translation on each of the many mRNAs you make, or extremely little transcription and TONS of translation on every mRNA you make, or anywhere in between. Today I learned that, across a wide variety of organisms, cells overwhelmingly choose to have low transcription and high translation over high transcription and low translation. Citation: http://ift.tt/2oIM3K9. This flies in the face of experimental data I've seen before that tells us that translation is much, much more energetically expensive for a cell than transcription and, in particular, that high-strength RBSs are *even more* energetically expensive than you'd expect. So... I don't know why cells would do this. The Alon paper has some arguments that don't make sense to me. One possibility, though, is that expressing low transcriptional rates makes gene expression *noisier*, which could be better for some processes. Still, I'd be surprised if the *vast majority* of genes are better expressed noisily than consistently. * Okay, you can also modify degradation speed and a couple other things, but I'm going to neglect those, because they turn out not to be too interesting in this story.

March 04, 2018 at 04:58AM

Today I learned: 1) Can you guess the most-played race in D&D? Today I learned that it's humans, by a pretty wide margin, according to Wizards of the Coast's polling. 2) Here's a potentially useful narrative trick -- the main character of a story doesn't have to be as interesting as the other characters, especially if it's a first-person story. In general, you can get a reader to go along with a main character by sheer dint of them being a main character. Learned this from a fellow student and part-time writer who had a problematic character that needed to exist for plot/connective reasons, but wasn't very interesting. So they flipped the story to first-person around that character. Instant fix. 3) Romans... ancient Romans were a special people. Incredible, but also so, so terrible. Case in point on the "Romans are the worst people ever" side of the ledger -- fatal charades. This was a Roman practice of performing plays using condemned criminals as actors. The only catch was that the plays involved the deaths of main characters, which were performed for real, live, on stage. Like... imagine Hamlet, but all the actors are on death row, and they actually die on stage. The Romans did that. I'm a bit curious how they convinced the prisoners to go along with it. Also, they must have had awful rehersals.

March 03, 2018 at 04:26AM

Today I learned: 1) Cave bacteria! There are bacteria that live exclusively on the inside surfaces of cave rock. They form visible sheets, and sometimes excrete really pretty minerals. I don't know much about them, but they can somehow live off of the rock face -- I'm not sure whether they're filter-feeding stuff that comes by, or if they're actually reacting the rock for energy. Whatever they're eating, it's not a particularly *accessible* source of food -- they are VERY SLOW GROWING, taking decades to fill small gaps in their mats. Some kind scientists at University of New Mexico compared the community compositions of cave bacteria and soil bacteria (http://ift.tt/2F8VxVa). Their conclusion was that the broad distribution of taxa was quite similar in the caves and in the soil above, but that there was quite a bit of divergence between *species* in the two climes. In other words, it looks like all of the usual inhabitants of soil got into the caves and colonized with roughly the same success, but then they evolved to look pretty different from their above-ground ancestors. Thanks to Patricia Prewitt for tipping me off to the existence of these critters! 2) RAND corporation has a new meta-study on the effects of gun policy. I've only read their summaries, but it looks pretty comprehensive. The big take-away is that there isn't enough data to make strong conclusions about most questions around the effets of gun control. There isn't a ton of data on gun violence, and what data there is isn't sufficient to reliably detect small effect sizes (which could still add to thousands of deaths per year). None of this is surprising, since the US government is BARRED BY LAW FROM FUNDING RESEARCH ON GUN CONTROL. It's usually not a good sign if someone feels they have to ban research on a topic, especially a poitically-charged one. Frankly, I don't take much of a hard stand on gun control one way or another, but IMHO the current research climate on gun control reeks of Lysenkoism. ANYWAY, the second-biggest take-away from the RAND meta-study is that there are *some* policies that appear to be effective at reducing violent crime, accidental deaths, and suicides (especially suicides). The first figure at this link is a good summary (http://ift.tt/2HYu9uF). For those who prefer a written digest, here it is: background checks and child access prevention laws help reduce suicides pretty dramatically; child-access prevention laws also almost certainly reduce accidental gun deaths; background checks and mental health screening probably decrease violent crime, and (perhaps surprisingly) stand-your-ground laws probably *increase* violent crime; concealed-carry laws might increase both accidental and homicidal deaths from guns, but the evidence is weak; most surprisingly to me, there is not evidence that bans on assault weapons and high-capacity magazines have much effect at all on anything. You can read the rest of the report here, if you're super-interested in gun control research and you have a lot of time on your hands: http://ift.tt/2t87FE9 3) Cells in a developing embryo can detect their position within the embryo within about 1% error, we think only using the concentrations of four transcription factors that are distributed in specific ways around the embryo. We don't know exactly how they do it, and that's quite close to the inforamtion-theretical limit of precision for the amount of information available in those transcription factor signals (unless, of course, there are channels they're exploiting that we don't know about). Thanks to Andy Halleran for this one!