| AskScience AMA Series: I'm Marina Picciotto, the Editor in Chief for the Journal of Neuroscience. Ask Me Anything! Posted: 16 Dec 2016 05:00 AM PST I'm the Professor of Psychiatry and Deputy Chair for Basic Science at Yale. I am also Professor in the departments of Neuroscience, Pharmacology and the Child Study Center. My research focuses on defining molecular mechanisms underlying behaviors related to psychiatric illness, with a particular focus on the function of acetylcholine and its receptors in the brain. I am also Editor in Chief of the Journal of Neuroscience, a fellow of the American Association for the Advancement of Science, and a member of the National Academy of Medicine. I'll be here to answer questions around 2 PM EST (18 UT). Ask me anything! submitted by /u/AskScienceModerator [link] [comments] |
| lim x->∞ of (e^(i * x)) is defined, but lim x->∞ of sin(x) AND lim x->∞ of cos(x) is not defined. How? Posted: 16 Dec 2016 03:58 AM PST Was just reading Feynman's lectures in physics and there is a part where cos(x) (for Harmonic Oscillator) is written as real part of ei*x. All good and well, until an integral of ei*x is used from 0 to ∞. In the limits, ei*∞ evaluates to 0. But neither is cos(∞) defined nor sin(∞). Can someone please explain this contradiction? EDIT: My doubt is now clear. Thanx to /u/lucasvb for clearing it. submitted by /u/rusty_ballsack_42 [link] [comments] |
| Is it possible that creatures very similar to those currently extint come to exist again in a very distant future? (through evolution) Posted: 16 Dec 2016 03:25 AM PST |
| How do those little winter birds, like chickadees, not freeze to death, and, if they are just little well-insulated furnaces, where does all their energy come from, just seeds? Posted: 15 Dec 2016 11:25 AM PST |
| Is there an operator that can have an associative property without a commutative property, or vice versa? Posted: 16 Dec 2016 02:18 AM PST It seems that operators, whether they're pertaining to numbers, sets, propositional logic, vectors or whatever, will only have an associative property (ex. (a+b)+c = a+(b+c) ) when they also have a commutative property (ex. a+b = b+a). I can't quite put my nose on what the two properties have in common with each other; is there an abstract proof (or disproof) that they're bi-conditional, or something along those lines? Sorry if my question's not clear I'm slightly drunk and frustrated because I can't figure it out on my own. submitted by /u/IDontLikePeaches_AMA [link] [comments] |
| If entropy is a measure for the amount of disorder in a system, why is it at its maximum when equillibrum is achieved? Posted: 16 Dec 2016 03:52 AM PST |
| Is gasoline entirely homonegous? If I buy Venezuelan gas at Citgo, is it any different than gas from oil from Saudi Arabia or Texas? Or does the refining process remove all differences? Posted: 16 Dec 2016 01:52 AM PST |
| How do Gemalto tokens work? Curious how the system knows when a numerical value off of a Gemalto token is a valid number. Posted: 15 Dec 2016 09:45 PM PST |
| Is it possible to build up enough static electricity to actually damage yourself? Posted: 15 Dec 2016 07:26 AM PST |
| What is the amperage of the human nervous system? Posted: 15 Dec 2016 12:30 PM PST |
| How many truly random bits are needed to produce n "good" pseudo-random bits? Posted: 16 Dec 2016 01:48 AM PST Suppose one has a "good" pseudo-random number generator, which is able to take varying numbers of seeds, then how many seeds should one use to produce n "good" pseudo-random numbers? Considering a "riffle" shuffle of cards (which seems to be almost complementary to Quicksort to me), it seems that one should need about O(log n) bits --- whether to shuffle up or shuffle down on each of the seven shuffles, in this case. Is this close to right? submitted by /u/ihaphleas [link] [comments] |
| What factors determine whether something (event, occurrence, experience, etc) makes it into our memory? Posted: 15 Dec 2016 05:42 PM PST We obviously don't remember everything. There's got to be some system of separating the wheat from the chaff. So what determines what makes the cut and gains admittance to our cranial repository? submitted by /u/Smooth_Caddy [link] [comments] |
| Why are elements above bismuth so very unstable? Posted: 15 Dec 2016 05:29 PM PST Something that I can't understand is why stability suddenly drops off after bismuth. Aside from elements 43 and 61, all elements under lead (82) are stable. However, after lead, I see the following: lead (stable) > bismuth ("stable", half-life 1019 a) > polonium (not at all stable, half-life of Po-209 is 125 a, or around 106 h) > astatine (half-life of At-210 is 8 h) > etc. The drop in half-life from bismuth to polonium is seventeen orders of magnitude. (and from polonium to astatine, another five.) So in total, from bismuth to astatine, half-life decreases by a factor of 1022 - a huge number. Why? Is there some sort of mechanism that breaks down as soon as z hits 84? If you say that nuclei are inherently very unstable past z=84, then how do you account for the relative stability of the actinides, and the massive jump in stability (nine orders of magnitude) from actinium to thorium? Actinium (half-life 21 a) > thorium (half-life 1010 a) This is a jump of nine orders of magnitude, and is followed by more relative stability: Protactinium (half-life 104 a) > uranium (half-life 109 a) > neptunium (half-life 106 a) > plutonium (half-life 108 a) > americium (half-life 104 a) > curium (half-life 107 a). (After this, stability drops again, but not as markedly as the drop from Bi to Po.) I'm obviously rounding half-lives here to the nearest order of magnitude as the exact numbers are unimportant, but my point stands. What is the reason for the tremendous decrease in stability after bismuth, as well as the reason for the return to long lives in the actinides? I know that nuclei with odd z are less stable than those with even z; this explains the "zig-zag" nature of the half-lives in the actinides. However, this does not account for the sudden drop in stability at polonium. submitted by /u/18blue42 [link] [comments] |
| are there materials that can change the wavelength of light? Posted: 15 Dec 2016 12:50 PM PST I don't mean optical filters which only block certain wavelengths, I mean transparent materials that can effectively redshift or blueshift any photon passing through them. submitted by /u/chunkylubber54 [link] [comments] |
| How do scientists know what elements celestial bodies are composed of? Posted: 15 Dec 2016 03:58 PM PST I couldn't readily find the answer to this by doing a google search, so I apologize in advance if this is too elementary of a question. How do scientists know what they are composed of, in general, without having samples to test? More specifically, how do they know the rivers and lakes of Titan are made of liquid methane/ethane? submitted by /u/pickle2tickle [link] [comments] |
| Can a breathable, Earth-like atmosphere actually be sustained on a planet like Mars with a substantially lower mass and gravity? Posted: 15 Dec 2016 06:48 AM PST Just wondering how big a part Earth's gravity plays in the composition of our atmosphere. I know Venus has a dramatically thicker atmosphere at approximately the same gravity but it's made up of toxic chemicals not like ours that's mostly nitrogen/oxygen. Is it possible to get a nitrogen/oxygen atmosphere on Mars with high enough air pressure to stay at less than 1/2 the gravity of Earth? If not what chemical combination would we need to best get something breathable but not exactly the same as Earth's atmosphere? submitted by /u/trevize1138 [link] [comments] |
| How do we keep stably anchored dry platforms in the deep sea? Posted: 15 Dec 2016 09:55 AM PST This may be more of an engineering question but I am interested in the forces that must be overcome to keep a permanent mooring at sea and what solutions we've found. I've seen spar buoys and things like oil rigs that are permanently moored at sea but i don't understand how they actually manage to resist the stress of constant battering by wind and wave. Say I have a platform anchored at sea by a tether to the sea floor, I would imagine that the wind and currents would pull the tether taut in the direction they predominantly blow. So then what happens when a large wave comes along (or, say, a storm)? The platform is going to be shifted from the lowest point right in front of the wave up to the crest, stressing the tether further. how does this not break tether? The alternative is that the platform temporarily comes underwater which i'm assuming we manage to avoid. Somehow oil rigs don't sink below the waves even for a bit, right? I get that they might avoid this by being elevated from the actual surface, such that it's the column sticking out that becomes partially submerged never actually reaching the platform on top. I'm interested in platforms floating on the surface directly and having some guarantees that they won't become submerged or have waves wash over their surface. have we found any way to do this? is it impossible to have that guarantee without having electrical systems that regulate bouyancy or slack on the anchors? what are other things that degrade the tether? do we have to throw down new ones every so often? do we use multiple tethers? if so how do we resist the added dimension of torsion that would be caused by the wind? how do we keep platforms that don't use spars from flipping over? just making them broad? I've seen things like at-sea fishing farms where the farms and houses are all just floating tethered together, how do these overcome these forces? What about algae and barnacles and other things that naturally grow on flotsam and add weight and drag to buoys, how do we deal with that? do we just have to clean it up periodically? What I actually want to know about is how can we construct a platform floating directly on the water on the deep ocean that will stay put, not flip over, not be pulled underwater but allowing for water to crash over the platform if necessary. I'm especially interested in simple mechanical solutions that don't really depend on fancy materials engineering or on actively monitoring the slack on the tether or buoyancy. How do we do things like this for research and/or industry? submitted by /u/polyguo [link] [comments] |
| What are the leading theories on the non-Indo European portion of Proto-Germanic? Posted: 15 Dec 2016 07:54 AM PST |
| Why do some intravenous medications produce a taste response as they are being injected? Posted: 15 Dec 2016 03:15 AM PST I've just had a few injections of Augmentin and as it is being injected I can taste it at the back of my throat. Why does this happen despite not being taken orally? I've also been having cyclizine IV and this also has a unique 'taste'. Why do some drugs have a 'taste', but some don't? submitted by /u/syzmcs [link] [comments] |
| What is the lowest and highest pressure with life? Posted: 15 Dec 2016 10:11 AM PST |
| Given 40 various dessert options with a quantity of 3 each, what are the odds that my coworker picks the exact same set of desserts as me? Posted: 15 Dec 2016 10:53 AM PST This happened today. There were about 40 different dessert options at a company party. You could also take multiple of each option, for example 3 of the same type of cookie (setting the max at 3 for each option is probably reasonable). I took one brownie and 2 of one particular type of cookie. So 2 of the 40 options, but 3 items in total. My coworker comes by an hour later with the exact same one type of brownie and 2 of the same cookie I got. What are the odds of them picking the exact same set (not factoring in bias)?? They are not as impressed as I am, but I want to prove it's a ridiculous anomaly. submitted by /u/RedditorSays [link] [comments] |
