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[
"What happens to nerve endings when we experience a burn of any kind? Does the nerve get such a sensory overload that it just shuts down instead of trying to process it all?"
] |
[
false
] | null |
[
"The nerves do no 'processing' themselves. When you apply a stimulus this strong nociceptors will fire rapidly inducing a sharp pain. If the heat source was sufficient to cause physical damage then inflammation will make the area very ",
"sensitive",
" to further stimulus, even non damaging stimulus. This is why lukewarm water hurts when you've been sunburnt. Unless the nociceptors become physically damaged themselves (eg. through prolonged exposure to fire), then they will continue to fire. However pain is essentially just an interpretation of this sensory input and so your pain perception could be modulated by the brain after repeated exposure to constantly firing nociceptors. Nociceptors themselves also have the ability to recalibrate their firing threshold to stimuli based on extended exposure. You can see this when you get into a hot bath, after a bit of pain you begin to tolerate the temperature better. "
] |
[
"In short, no. The nerve is firing like crazy after a burn. Your damaged skin is releasing signals that are received by the nerve endings. These signals inform you that you are in serious pain.",
"Now, let's get a bit more technical. There are different classes of nerve fibers for pain and touch sensation, as well as different receptors on any particular fiber that can sense different touch responses. The pain (nociceptive) signals are largely carried by two classes of nerve fibers known as A(delta) nociceptors and C fibers. The signals they detect from your skin cells are a mix of small molecules released from dying or damaged skin cells, things like protons, ATP, bradykinin and prostanoids, also temperature (cold and hot) in and of itself can active receptors on touch sensory nerve endings. The A(delta) and C fibers and their receptors together sense sharp pricking pain, burning pain, freezing pain, and slow, burning pain. A(delta) fibers generally sense fast pricking pain, whereas C fibers sense slow, dull pain. The pain felt after burning yourself is a combination of A(delta) fibers (the fast, sharp pain that makes you pull your hand off the burner) and C fibers (the dull, slow pain that keeps you up at night).",
"What might shut down after extreme pain is an adaptive response in your brain. Extreme and prolonged pain can alter your brain in ways we do not fully understand. Passing out in response to extreme pain is one adaptive mechanism to stop yourself from feeling the pain.",
"You might be wondering if we are capable of getting burned so badly that we don't experience pain because the nerves are signed off our bodies. No, unless you burn yourself up entirely. At the edges of any serious burn will be active nerve endings sensing the pain and telling your body that you have done something very bad."
] |
[
"You can overload the collator of some sensory information, the hippocampus, but the others have addressed the rest of this process well. Overload, in this case, would lead to blacking out, and just prior to that, you'd have blinding pain. Nothing happens to your eyes, per se, but there's a bottleneck at that part of the brain, and input from other sensory modalities will be inhibited temporarily, so your vision and hearing can literally cut out. BTW, \"blinding pain\" is a 10 on the pain scale. "
] |
[
"How are the triple(or more) parachutes commonly seen on capsules returning from space kept apart?"
] |
[
false
] |
Judging by the direction of force by the cord, shouldn't they be pulled together?
|
[
"There's a few things at work here. One is that the cables aren't all the same length, which will naturally give a lean to the parachute. Then there's the shape of the parachute, it's not completely symmetrical. There's also a lot of air pressure around the parachutes pushing them away."
] |
[
"They also fire them out of cannons in three directions. They also \"vent\" the canopies to help.",
"Here is a paper on the ",
"Apollo system written by T. W. Knacke",
". Someone I got to spend a day with a few decades ago."
] |
[
"Kind of like how you can use a sail to travel in directions other that directly with wind. "
] |
[
"Does Earth's atmosphere expand as a consequence of climate change?"
] |
[
false
] |
When climate change is discussed a increase in mean atmospheric temperature is often mentioned. As we know, gasses expand with increased temperature. Does this mean that the total volume of Earth's atmosphere also increases?
|
[
"Great question! Air expands as it warms, but ",
".",
"In particular, the troposphere, the lowest region where we live and where weather happens, is as you know warming. As a result, the height of the top of that layer, the tropopause, is rising over time.",
"Surprisingly, though, increased CO2 causes the upper layers of the atmosphere to ",
". The reason is interesting: these layers receive lots of energy from solar ultraviolet, and they have trouble getting rid of it. Because CO2 can vibrate at a frequency that matches infrared light, it's both a good absorber of infrared ",
" a good emitter. Adding CO2 to the upper atmosphere gives it a way to get rid of solar energy and cool down.",
"So in the upper atmosphere, increased cooling by CO2 is causing these layers to shrink. The thermosphere (the uppermost level) has contracted so that at 400 km altitude (International Space Station height), the atmosphere is about 10-12% thinner than it was 50 years ago.",
"http://www.realclimate.org/index.php/archives/2006/11/the-sky-is-falling/",
"https://www.ipcc.ch/report/ar4/wg1/",
" (See Figure 9.14)",
"https://slideplayer.com/slide/10485054/"
] |
[
"While the atmosphere and ocean expand due to warming, the size of the atmosphere shouldn't change since the gravity gradient is static. As the atmosphere expands, more air molecules would have the necessary energy to escape. The transient case might have a larger volume but once the increase in temperature stops the final size should be similar to what we have now as the more energetic molecules in weaker gravity escapes."
] |
[
"Thank you for the detailed answer, great stuff! "
] |
[
"Would a Tesla Coil work in a Vacuum?"
] |
[
false
] |
If not, why not?
|
[
"I see no reason why not. ",
"In fact, you can see it in action for yourself."
] |
[
"If the electrical potential difference (ie Voltage) was great enough there would indeed be an electron flow. But since it's not hitting any particles of gas, no ionisation takes place and the flow emits no light."
] |
[
"A Tesla coil should be able to operate in a vacuum. However, I don't believe you would be able to see the electric discharge that most people associate with a tesla coil. The electric arc you can generate from a tesla coil is the result of turning air turning into a plasma. In the absence of air there would be nothing to carry the current generated by the coil, so you wouldn't get to see the really cool arcs."
] |
[
"The sun radiates about 1000 Watts/m^2 of light on the surface of the earth. How much does that compare to a single star at night?"
] |
[
false
] | null |
[
"The Sun's apparent magnitude is -26.7. The \"average\" star you can see in the night sky is something around apparent magnitude 4. (The brightest star is -1.5, faintest you can see ~5-6).",
"For every 5 magnitudes more negative, an object is 100 times brighter. So the Sun is -26.7 - (-1.5) = 25.2 magnitudes brighter than the brightest star. Rounding that to 25 means it is 10",
" times as bright.",
"Since the Sun radiates ~1000 W/m",
" ",
" (",
"Wolfram confirms",
"). A more typical star is a factor of ~100 below that, so 1 nW/m",
": The Sun is 10 billion times brighter than the brightest star and a trillion times brighter than a more \"typical\" star."
] |
[
"Multiply the intensity of one star by the number of visible stars. Google tells me less than 10000, so still probly much less than 1 mW/m"
] |
[
"What about the sum total of light produced by all of the stars in the night sky ignoring moonlight"
] |
[
"How do cellphone and bluetooth signals travel through walls??"
] |
[
false
] |
Ok so correct me if I'm wrong, but aren't both signals made up of electromagnetic waves, the same stuff as visible light just with more energy and smaller wavelength. So, if visible light cant travel through walls, why can bluetooth and cellphones?? Is it because of the increased energy?? I know that the photons (assuming cellphones and bluetooth rely on photon based transmission) aren't any 'smaller' so it's not like they would fit through subatomic gaps in the walls. What am I missing??
|
[
"The default is for photons to go through matter. Absorption can be seen as the unusual event which occurs when the photon matches an energy gap available in the material it hits. Metals have lots of energy levels available in their sea of electrons, so they will absorb most photons; the cellulose and lignin in a wooden wall have lots of energy states that can be activated by a visible photon, but very few for a weaker radio photon. Thus long wavelengths (such as radio and microwave) can pass through walls. ",
"Incidentally, why the coincidence that walls happen to block the kind of light we can see? Evolution. Organisms to which air is transparent and common materials are opaque tend to have more offspring than organisms which can't tell the difference. "
] |
[
"It's all about the electrons in the material. Jiminuse gave a couple of good examples above. I'll try to elaborate a bit. There are a few processes that can happen:\n1) The photon passes through the material\n2) The photon is absorbed\n3) The photon is reflected\n4) The photon is scattered",
"1) is actually not as simple as it sounds. There are other processes that I haven't mentioned, like refraction, dispersion, dichroism, etc. But for simplicity let's say the materials are simply transparent and leave it at that.",
"2) is caused by quantum effects. For the electrons in a material, some energies are \"allowed\" while others are forbidden. The material just happens to have a gap between two allowed energy bands that matches the energy of your photons. When one of the photons collides with an electron from the lower energy band, the electron will absorb the photon and it's energy and enter the higher energy band. The photon disappears into the material. The electron can dissipate its new found energy as heat, by fluorescing another photon, or a few other processes. Absorption is why everyday objects have color.",
"3) Reflection. The electrons in metals, for example, are not tightly bound to any one particular atom. This property (which also makes them good electrical conductors) means that the electrons can follow the oscillating electric field of light and reflect it back. But this only happens up to a certain point. Above a particular frequency (the metal's plasma frequency) the electrons can no longer keep up, and the metal is no longer reflective. The crossover point for most transition metals is somewhere in the UV. Thus, most metals are at least partially transparent to X-rays, but will reflect visible, IR, and microwave radiation. Now, with Radio waves another interesting phenomenon starts to occur: the waves are so long that the ability of the electrons to track the electric field depends on the size of the piece of metal. So you have to get the right antenna for your waves.",
"4) Scattering. The photon meets an electron, starts to interact with it like in 2), but this time temporarily enters a forbidden high energy state and almost immediately bounces back down to its original energy, re-emitting the photon in a completely random direction. Most of the scattering you see is from an interface of some sort. It's the reason why sand, sugar, bubbles, powdered glass, etc. are white. In fact it's the reason why most everyday white objects aren't clear."
] |
[
"Note, metals are highly reflective, and not highly absorptive because they have a sea of effectively free electrons that can respond near-instantaneously to the incident waves, especially at lower frequencies. ",
"The key worth reiterating is that radio waves have much longer wavelengths than visible light, and not that they have more energy (They in fact have thousands to millions times ",
" energy per photon than visible light). "
] |
[
"Question about boiling water in a vacuum and oil extraction."
] |
[
false
] |
So when making beer, hops are boiled with the beer malt to extract the oils and acids which add the flavour. Secondary 'hopping' is later used to give a fresher, brighter hop flavour, as alot of the compounds in the hops are destroyed from the heat in the boiling process. The boiling is required, however, to initially extract enough of the hop compounds. Similarily, coffee is generally brewed to specific ground size/temperature/time to extract the optimum flavour, as too much heat makes the coffee bitter and acidic. Coffee can be brewed with cold water for an excellent cup of coffee, it just takes anywhere from 4-18 hours and specific ground/water exposure. If water will boil at a lower temperature when exposed to a vacuum, how does this effect the process in which these oils and flavour compounds are extracted. Is the temperature of the solution being used essential for effective extraction, or does the physical act of 'boiling' do the work. Because the molecules of water are 'vibrating' the same when boiling irregardless of temperature, I assume that you would be able to extract more oils without the negative effect of temperature. Or am I completely wrong, and the damaging effect would be the same?
|
[
"You would not end up with the same end result you'd get when boiling at sea level pressures, unknown if it'd be better or worse. ",
"The oils and other compounds have their own flashpoints, vapor pressure, and other characteristics. Each has their own rate of change with regards to how they respond to a change in atmospheric pressure. ",
"My personal experience with this comes with trying to set the pitch in white pine in a vacuum kiln ;) "
] |
[
"Id never heard about pitch from trees, read a bit on it and its pretty interesting"
] |
[
"Here's a neat, broad overview on some of the more commonly known chemicals found in trees: ",
"http://treedictionary.com/DICT2003/shigo/TREECHEM.html",
"EDIT: in addition to the common ones such a sugars and the wide variety of oils."
] |
[
"Why is the \"philia\" suffix being used increasingly by academics to denote sexual, or \"eros,\" love, when the Greek roots are clear in their respective differences of meaning?"
] |
[
false
] |
Does this mean that bibliophiles want to have sex with books, or audiophiles have orgasms listening to music? Doesn't the injudicious use of the suffix to denote sexual attraction in certain terms (paedophile, androphile, gynephile, et al.) lead to confusion and difficulty educating others? Shouldn't any "philia" that is defined as sexual in nature be renamed with the "-erotic" suffix, since the Greek roots are defined precisely?
|
[
"-erotic is already used, like in \"homoerotic\", \"autoerotic\" and probably a lot more words I can't think of right now.",
"-philia is way more common, but it doesn't mean the same thing in English that it does in Greek. It's acquired all of the connotations of \"like\" or \"love\" in English. That's why it can be used for anything from a water-loving molecule to a sexual fetish. Meanwhile, in English, \"erotic\" has the meaning of \"sexual\" in general, not just sexual love. Words have their meanings extended all the time. It's called semantic drift and is a normal process in language just like genetic drift in biology.",
"I don't think there is much confusion over this in practice and honestly, insisting we use these roots exactly like the Greeks did 2000 years ago is extremely pedantic. This isn't Sparta, this is English."
] |
[
"\"Philia\", as I know it, is simply the fondness for something. I guess that can escalate all the way to the \"love\" of something, but I think it's defined pretty broadly in that sense.",
"Any time I've heard it used for sexual interests or proclivities, it would mean \"the love of\". I don't think it explicitly means \"the sexual attraction to\", however. So audiophile is simply someone who has great affection for, or love of, music.",
"I guess \"erotic\" could be used in its place, and is pretty specific to sexuality, but at this point I don't think it really matters."
] |
[
"Well that's a fair criticism, I suppose, but my intention was pretty much the opposite of pedantry, since the exact issue I raised I encountered in my own learning, which was why I brought it up and questioned it. ",
"Would you agree that unchecked semantic drift could lead to a more rapid erosion of understanding over time? Isn't prescriptive grammar a check that could extend the temporal range of cross-cultural interpretation?"
] |
[
"Suppose there actually is a multiverse, and we found a way to send information between parallel universes. Could that be used to violate Heisenberg's uncertainty theorem?"
] |
[
false
] | null |
[
"Quantum mechanics says nothing about the result of such an experiment. You can't just make up hypotheticals that violate basic principles and then ask what those basic principles say in such a situation. There's no reason that atom A in universe A and atom B in universe B would have anything to do with each other."
] |
[
"Oh sorry, I thought the bit about atom A and atom B was the explanation. But I can try to explain a bit more. ",
"First, the notion of parallel universes is little more than conjecture so to assign any particular rules to them is arbitrary. Second, if there is interaction between the universes, then it really isn't meaningful to describe them as different universes anymore. Third, there's no reason that atoms would have anything to do with each other. ",
"why would the atoms in each universe have nothing to do with each other? Aren't they the same atom at this point (or two completely identical copies of the same atom, which is practically the same thing",
"To be honest, I'm not really sure how to explain what's wrong with this thinking except to say that they are not the same...They are not the same thing. You have one atom in one place and another atom in another place. Why are they one entity? And why does a measurement about one tell you anything about another? Perhaps you're thinking about some form of entanglement? I'm not really sure what's going on with the line of thought that somehow these two atoms are just one atom..."
] |
[
"Was it in using the many-worlds interpretation as a framework for the thought experiment?",
"Not at all; the MWI is consistent with modern quantum mechanics.",
"Or did I step outside the bounds of MWI itself?",
"This one.",
"First, I think you've misunderstood the MWI. The many-worlds are ",
" distinct universes. Rather, they correspond to different \"branches\" of a single universal wave function. There's only the one electron, not one in \"both worlds\". I don't really know a good way to put this in lay-terms, but ",
"this site",
" has a decent elaboration.",
"Second, in assuming you can communicate between worlds you've assumed they're not actually distinct worlds.",
"Then there's the fact that you can't actually have two worlds that are identical except for what's being measured; in order to make those measurements, entirely different experiments have to be set up, which means the worlds diverged long before the measurements were made. Then one world branches based on the momentum measurements and the other branches based on the position measurements, and you get a whole lot of new branches corresponding to each different momentum and position measurement."
] |
[
"How do we know the actual wavelength of light originating from the cluster of galaxies that are receding away from us when all we observe is red shifted light because of expansion?"
] |
[
false
] | null |
[
"Every element has its own characteristic spectrum of light, so we can look for this fingerprint in the light we receive. Since hydrogen is by far the most abundant element, we expect the spectrum of hydrogen to feature prominently. However, the features of the hydrogen spectrum won't appear at the same wavelengths as they do when we measure hydrogen in the lab, because of the red shift. ",
"Instead, the spectrum is shifted by a certain amount. But despite the shift, the structure remains unchanged, so we can identify the spectral lines of hydrogen in the light we collect. And by the amount it has shifted from what we measure in the lab, we can obtain an estimate for the speed with which the source is moving away from us."
] |
[
"For galaxies, you would generally see uncertainties on the order of a few km/s. This sounds like a lot, but is actually pretty accurate.",
"The most precise measurements I know of are those used to detect exoplanets. If you have a solar system, the star is not perfectly stationary at the center. Instead, it revolves around the center of mass, which is dominated by the star, but also accounts for the orbiting planets. As the planet orbits the star, the star wobbles a bit, and this can be observed. In this case, you can get velocities from this relativistic effect with an uncertainty below a meter per second. Yup, you read that right. From the wobble of the star, you can derive the mass and orbit of the orbiting planet.",
"Some measurements of the velocity of distant stars are literally more accurate than the average laser gun measurements a police officer performs to catch speeding cars."
] |
[
"How accurate is the estimate?"
] |
[
"How many gamma rays is the average person exposed to on Earth?"
] |
[
false
] | null |
[
"Lots. If you spend a lot of time in a building made of concrete, you're getting gammas from the small amount of potassium-40 in natural potassium. If you have an americium-241 smoke detector, you'll get gammas from that. ",
"Am alpha-decays into ",
"Np, but it doesn't always go directly to the ground state. Sometimes the alpha decays populate excited states in ",
"Np, which will subsequently decay by gamma emission. This is all part of your normal background dose that you receive on a daily basis; nothing to worry about."
] |
[
"Silly question: Has the average number of Gamma rays been calculated/estimated? It'd be a fun little fact to know."
] |
[
"I decided to see if I could work out what \"lots\" meant, but I think I must of screwed up. What did I do wrong?",
"Here is my working:",
"Let's see if we can get an order of magnitude. According to ",
"https://xkcd.com/radiation/",
", the average background dose is 10 microsieverts. A Sievert is a dose of 1 joule per kg adjusted by a multiplier that depends on the type of radiation, but for gamma rays that multiplier is 1.",
"I'm going to make the most suspect assumption here suppose that all the radiation you are expose to is gamma. This is going to mean what I work out is some kind of an upper bound. It might be ten times off or more, but I doubt its a thousand times off.",
"So a typical human might mass about 80kg, so that's 0.0008 joules or radiation. Wolfram alpha gives that as \"1/12 the acoustic energy contained in a wispier\". Anyway, gamma rays can have different energies but I'm going to use 512keV as a my typical value. That gives 9.75 billion.",
"While that number certainly qualifies as \"lots\", honestly, this seems a bit high to me. If it were this high, you'd expect Geiger counters to be a white noise of clicks all the time.",
"Edit: Just thought of another assumption that is dodgy. A gamma ray is going to deposit all its energy into a person it hits."
] |
[
"Are quarks and electrons really indivisible?"
] |
[
false
] |
I read somewhere that quarks and electrons are indivisible. How can we know that? As far as I know, the term "atom" means indivisible in greek, which shows we once thought the atom was indivisible as well. It's hard for me to understand how something can exist without being made of anything else, it just exists.
|
[
"The excitations in a spin liquid (not a state liquid) are not literally an electron split in pieces. Rather, the collective excitations of a system are quasiparticles which carry fractions of the electron's quantum numbers (charge, spin, and statistics). This kind of fractionalization has already been convincingly shown to occur in ",
"fractional quantum Hall systems",
", where experiments have detected fractional electric charge (fractional statistics are harder to detect experimentally).",
"If you inject an electron into a fractional quantum Hall system with quasiparticle charge e/3 (this is the most robust FQHE state), it will be a linear combination of three quasiparticles, and you will see three of these quasiparticles which can move around independently. But the fact that there ",
" be three quasiparticles is a reflection of the fact that the underlying charge carriers of the system are electrons with charge e. In addition, you would only be able to create these quasiparticles in multiples of three."
] |
[
"It's hard for me to understand how something can exist without being made of anything else, it just exists.",
"Do you imagine that the sub-particles of electrons and quarks would also have sub-particles etc.? I find the idea of there being an infinite regression of sub-particles much harder to swallow."
] |
[
"Is it just ",
" or is it - with our current understandings of physics - impossible? I always wondered, since the universe is supposedly infinite in size, why should there be a lower limit for size? Also, black holes (as far as I understand them) are basically a single point with all the mass in it, \"surrounded\" by a Schwarzschild Radius, basically violating our physical laws - could this also be the case with electrons/quarks? (ofc those are not black holes, I hope you understand what I mean)"
] |
[
"Do other species, animals, etc. experience the placebo effect?"
] |
[
false
] |
[deleted]
|
[
"This is an interesting question. In humans, the placebo effect works because of the recipient's belief in the efficacy of the medication.",
"So, if it worked for any other animal, that would be proof that they were intelligent enough to understand what medication is, and had enough imagination to project what the results of taking medication would be."
] |
[
"Probably",
"There is also an indirect placebo-like effect when humans judging the state of the animal know (or believe) some treatment happened: ",
"Discussion"
] |
[
"There is a study showing that the placebo effect works in dogs to reduce seizures: ",
"https://www.ncbi.nlm.nih.gov/m/pubmed/19912522/",
"However, researchers think that it arises because dogs trust humans for medication. When an owner gives it something that’s not food, dogs take it expecting to get better, possibly establishing a placebo effect. But that’s only a hypothesis.",
"What’s more interesting is that in veterinary drug trials there aren’t many placebo controlled trials but there may need to be."
] |
[
"Why does blue light penetrate water the furthest, but when you get to shorter wavelengths like UV it barely penetrates?"
] |
[
false
] | null |
[
"When you say blue light penetrates water the furthest, are you referring to the absorption spectrum of water, or the fact that large bodies of water appear blue? These two phenomena have different explanations.",
"Each compound has a characteristic absorption spectrum, which dictates its colour. Water tends to absorb red light more than blue light (very weakly), and also happens to absorb UV light very well. This ",
"spectrum",
" should clarify things.",
"There are many proposed reasons for why large bodies of water appear blue, and many of them involve scattering, rather than absorption."
] |
[
"I'm not really concerned with the color but just depth of penetration. I was under the impression that blue light in low turbidity waters is able to penetrate water the furthest depth wise. I thought it was because shorter wavelengths are more energetic but are more easily absorbed. Blue light is the shortest wavelength that is not greatly absorbed by water. I feel like im missing something though."
] |
[
"Penetration is basically the inverse of \"interaction with matter\". The more it interacts, the less it will penetrate. Absorption is that interaction in this case, so as stated before, blue light doesn't get absorbed as much as UV or red light is, thus having a larger penetration depth.",
"Penetration depth does not solely rely on energy - it depends on the medium as well. One obvious example is X-ray - it can penetrate soft tissue, but not bone, even though they have pretty much equal energy (for argument's sake, in medical imaging in this single instance)."
] |
[
"Can pair annihilation occur in free space?"
] |
[
false
] |
I know that pair production cannot occur in free space, but can pair annihilation? If so, why?
|
[
"Both processes can happen in free space. Specifically, a particle anti-particle pair can annhilate producing two photons with the same total energy as the energy of the two particles, or two photons can annihilate creating another particle/antiparticle pair (the photon is its own antiparticle).",
"The event you are describing that can be forbidden is a single photon creating a massive particle antiparticle pair. The reason is that if all of the energy of the photon was converted into the the particles, than in the center of momentum frame of reference of the new particles, their linear momentum would be zero. However in the same frame of reference the initial photon would have had a finite momentum. Therefore the conservation of momentum would be violated in such a process."
] |
[
"/u/quantum-confinement",
" nailed it; but I'll be even briefer.",
"Yes, pair annihilation can occur in free space, and pair production can too. Either one is a ",
" interaction (two photons, one electron, one positron), and both directions are allowed. "
] |
[
"Yes. When massive particles are already present, there is sufficient energy in any reference frame for the interaction to occur. With just a photon, there can be a reference frame in which it does not have enough energy to produce particles."
] |
[
"Which way should a car swerve to avoid flipping over? Should it speed up, slow down, or stay the same speed while doing so?"
] |
[
false
] |
I don't know how to describe this exactly, but say a person is driving a car and something hits it on one side in such a way that it starts tilting to the right (in a clockwise motion if viewed from behind). The driver has barely seconds to react before the car is flipped over. Which way should he swerve to avoid flipping over? Also, would speeding up or slowing down affect leveling the car out at all?
|
[
"I was taught to \"steer into the skid\", or, in other words, as you lose control you steer in the direction the car is heading. This works well for skids, though it can be counter intuitive. Rolls usually start as skids.",
"By pointing the front wheels in the direction of movement, they will roll instead of sliding. If they slide, there will be a force below the center of gravity opposing the direction of travel and the inertial force of the car above the center of gravity, setting up a rotation. Also, if you steer towards the skid, you are acting to align the vehicle with the direction of motion and vehicles usually don't roll end over end. ",
"In terms of braking or accelerating, in most cases anything which increases the sliding of the wheels makes control harder. Most modern cars have anti-lock brakes so they don't lock up, so, probably, in most cases braking would reduce speed while retaining control to the extent control can be retained. If the car did not have anti-lock brakes, neither braking nor accelerating would be best until control is regained.",
"Source: 37 years accident free driving in Canada's icy conditions thanks to a good driving instructor."
] |
[
"Thanks! I should have been more specific with my question though; for the example scenario I gave, I was imagining the car beginning to roll because it ran into an object like a curb or something on one side, so it hit one wheel and immediately began the roll. Basically what made me think of the question was that I was driving down a steep hill, was going pretty fast, and barely maneuvered through a roundabout without an accident because I had to swerve right then left very quickly because I was still moving very fast. Afterwards, I wondering what would happen if I hit the curb of the roundabout, and if I did which way I should swerve to avoid flipping. Would it still be the same solution there?"
] |
[
"I'll take a stab at answering this.",
"Say the car is swerving left, and therefore will roll clockwise (when looking through the car from the rear). The driver should steer right, so as to counteract this roll (steering right will make the car try to lean left).",
"In terms of speeds, braking will cause the car to lower at the front and raise at the back (empirical based, you could prove it using mechanics). So that would aid the car in flipping over as it will move the centre of mass further towards the edge of the vehicle.",
"If you stayed at the same speed it won't do anything to counteract the roll.",
"Whereas if you accelerated, the front of the car would rise, the rear dip and this would help the centre of mass to stay around the centre of the vehicle.",
"Disclaimer: I did no maths to determine this, just used physical intuition."
] |
[
"How do you calculate velocity in space?"
] |
[
false
] |
Do you use Earth or the Sun as a frame of reference? Is there some way to find out how fast they are moving through the universe? How does the speed of our solar system affect time? If you found a way to come to a stop (with respect to all of existence), would the traveler age faster than everyone else on earth? Would the earth appear to move away slower? Disclaimer: I am not really educated in any of this, barely have any knowledge of relativity, just curious. Edit: Would it matter which direction you started moving? For example: moving away from Earth in the direction of the expansion of the universe would increase your true(?) velocity, while moving toward the center would decrease it.
|
[
"You can use any reference frame you like, there is no absolute frame of motion in the Universe. If we measure the orbit of the planets, then the speed is in relation to the Sun - but if we measure the orbit of the moon, then the orbital speed is in relation to the Earth. The speed we measure Voyager travelling at, is in relation to the Earth, which is why on sites such as NASA the velocity report of the Voyager crafts change in relation to where Earth is in it's orbit - in reality the Voyager crafts are travelling at a constant velocity. ",
"We wouldn't know if we had truely \"stopped\" in the Universe, as there is no outside, or known centre to measure our Velocity - we would just know what our velocity/motion is in relation to xyz coordinates of whatever we decide to measure our velocity against. "
] |
[
"It is completely true that there's no absolute from of motion in the universe. And as far as current space travel is concerned, using the Earth or Sun as a reference is a good way to define velocity. However, I think that if we ever find a way to travel at velocities close to the speed of light, the CMB would be a very good reference frame to use. Of course, by the time humans can move at a fraction of the speed of light, we may have already discovered an even better reference frame to use."
] |
[
"In fact, you're always sitting still in your own reference frame. It's everything else that's moving."
] |
[
"Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"Can you please explain the differences in sex, gender, and how chromosomes fit into the picture. I’m curious about the lifestyle effects of each are driven by those factors. ie: Say someone is born with XXY. How is their life impacted by this if at all?"
] |
[
"OK, so let's start at the beginning. Your genome is composed of 3 billion bases of DNA. Those 3 billion bases are found on 46 different strands of DNA. Each strand is called a chromosome. Hence, you have 46 chromosomes. There are 22 chromosomes that are what we call autosomes, they basically look exactly the same in all members of the species. The sex chromosomes on the other hand come in two variants: X and Y. (Fun fact, birds also have sex chromosomes, but theirs are Z and W.) Now in theory, this should give us a few possible combinations: XX, XY, YX and YY. But YY doesn't happen. And the difference between XY and YX is nonexistent in our phenotype (what we actually are). So this means that our sex is a combo of getting either two X chromosomes (female) or one X and one Y (male). ",
"Why do we need an X chromosome? the genetic features on the Y chromosome have been undergoing selection to 'slim down' the chromosome to only 'masculine' genes. But there are a bunch of genes on the X chromosomes that have nothing to do with your sex: genes that code for stuff in your eyes, your gut, etc. So, while two Y chromosomes might give you twice the 'masculine' genes, the loss of ALL the other genes needed to run a basic human is a no-go. This is why we have X-linked genetic disorders like some types of red-green color blindness. Males only get a copy of the X chromosome from their mother and if it carries any genetic problems, then those males MUST express the problem. Females can avoid those problems because any genes that have bad alleles on one X chromosome can be 'filled in' by good alleles on other X chromosome. ",
"Once you have your chromosomes, then you body needs to pattern itself. There are a host of of genes that create the pattern of your body. Hox genes are a good example of one class. As the proteins of Hox genes diffuse through the body and overlap, they activate receptors and different amount of receptor activation tell those cells to form nerves, muscles, bones, etc. The reproductive systems actually arise from an identical set of structures that will differentiate into either a penis/scrotum/testes/tubes or ovary/vagina/uterus/fallopian tube. But this depends entirely on signals that are being received during development. The 'female' pattern is what everyone starts out as. Then if you are XY and send the appropriate signals during development (or are XX and inappropriately send a signal) then you become male. (or an XY can fail to send the signal and become female). The key factor here is that as long as the develops into a normal male or female pattern, they are normal. But GENOTYPE (XX or XY) can be different than PHENOTYPE (male or female) depending on what went on during development. ",
"Generally any alteration to create a trisomy (like XXY, XYY, etc.) causes large scale changes to the reproductive system that are picked up by doctors and can cause major problems throughout the persons life. So they are given named disorders. By just being male but having 2 X chromosomes is not a disorder. Make sense?"
] |
[
"To my knowledge, the difference is mainly about chemical reactivity.",
"Nitrous oxide is pretty chemically unreactive under normal conditions, and its anesthetic effects are similar to other gases like xenon, carbon tetrachloride, cyclopropane, or even nitrogen under high pressure. You can read about what we know about how anesthetic gases work here:",
"https://en.wikipedia.org/wiki/Theories_of_general_anaesthetic_action",
"Nitrous oxide does not really interact chemically with the body or get metabolized, you can breathe it back out by the lungs and the anesthetic effect is quickly reversed as the gas leaves your body. ",
"In contrast nitrogen dioxide is chemically reactive under normal conditions including in the body, for example it can react with water to create nitrous acid and nitric acid, which can damage tissue just by lowering the pH. ",
"Nitrogen dioxide also has other effects related to its chemical reactivity such as causing lipid peroxidation and other effects that are associated with what are called ROS and RNS, reactive oxygen species and reactive nitrogen species. The specific chemistry here is complicated but you can certainly find info about it if you search."
] |
[
"If lobsters have the ability to naturally live indefinitely, why don't we have large millennium old lobsters running around?"
] |
[
false
] | null |
[
"Predation from humans and other top predators may play a role, as may competition from smaller lobsters. Being big doesn't necessarily make you better at catching food, and you have fewer places to hide. Plus there is disease and accidental death to slowly weed out the old ones.",
"There are records of lobsters longer than 4ft, and if you believe some of the tales written by early explorers, they got even bigger than that. Of course, old fish tales are old fish tales, but back when there were more cod there would have been larger lobsters, since cod preferentially eat the little guys reducing competition for the few who lived to get big enough."
] |
[
"Does anyone know if anyone has a captive lobster that they are trying to keep alive for as long as possible? If not this should happen. "
] |
[
"http://www.int-res.com/articles/dao2007/79/d079p173.pdf",
"I had it wrong, it's actually the other way around. Healthy lobsters will avoid diseased lobsters (Caribbean spiny lobster ",
") even a week or more before they are infectious, at least with the virus PaV1. The juveniles also live solitary lives, which coincides with the time of their lives with the highest risk of infection, so it's hypothesized that solitary juveniles are an adaptation/selection for disease avoidance.",
"Mark Butler of Old Dominion University and Don Behringer, University of Florida, do/did a lot of work on this topic specifically, about behavioral influence on disease transmission.",
"Among the normally social large juveniles, healthy\nlobsters avoid contact with diseased lobsters and do\nso a week or more before diseased lobsters become\ninfectious (Behringer et al. 2006). Field observations\nsuggest that such behavior may retard PaV1 transmission in the wild because there is no relationship\nbetween local population density and PaV1 prevalence in natural habitats or in habitats augmented\nwith artificial structures that tend to attract and concentrate lobsters (Behringer & Butler 2006)."
] |
[
"Why hasn't America switched to the SI metric system?"
] |
[
false
] | null |
[
"I'm not sure if this is a scientific question or even answer, but in my opinion it's social momentum. Think of all the people who have grown up using imperial units and how much of a fuss they would kick up if there was a change. I imagine the only way it will happen is by putting both units of everything and then slowly people will learn metric, maybe."
] |
[
"But all the other countries used different methods as well. They grew up with them as well. But then they switched. How come that almost every country switched except a few. And those are not some undeveloped countries. USA, UK, they're global players. They're a big part in today's globalized world."
] |
[
"The UK does use metric everywhere except for miles really. I think it is partly also a social issue, maybe Americans are less willing to change. This really isn't a question for science though since all scientists use metric anyway."
] |
[
"Does Purcell's Relativistic Electromagnetism model contradict Maxwell's Equations in any way? Are they equally valid in a predictive sense?"
] |
[
false
] | null |
[
"I am not an expert on Purcell, but a bit of googling/wikipedia implicates to me that Purcell simply had a different way of explaining the same theory."
] |
[
"They are the same, just a different derivation. ",
"It isn't a \"model\". That word has a very important definition to physicists. What he did was use his understanding of Special Relativity to explain things like magnetism. "
] |
[
"It contradicts in that it is relativistic when Maxwell is not, but that is probably already assumed. ",
"The basic gist of Purcell's explanation is that electrostatic force is fundamental, and magnetism is explained using relativity. It seems magnetism arises as a natural side effect of the speed of light remaining constant in all reference frames and electrostatic force being mediated by photons, but this view turns out to be incorrect.",
"Force is not a valid 4-vector in special relativity",
", so neither the electric or magnetic forces can be considered fundamental, and Purcell's view of the electric field being fundamental isn't quite right because of this. It turns out the ",
"A-field",
", which is the magnetic vector potential, is the most fundamental. "
] |
[
"Physics question: physics and scale (Not exactly sure how to formulate this question)"
] |
[
false
] |
I was wondering, if Newtonian Physics become inapplicable at small scales (quantum physics), what happens when we go the other direction and increase the scale proportionately? In other words, if we scale up large enough, do Newtonian physics become inapplicable?
|
[
"You mean if we consider stars and galaxies instead of apples falling? Newton's laws are good on the galactic scale for most things, but General Relativity is the true theory at larger scales."
] |
[
"There are two possibilities that \"GR breaks down\":",
"Dark Matter problem, as cookie mentioned. That would lead us to MOND theories, which are very unlikely to be true.",
"Dark Energy problem, which is at even bigger scales - like size of the universe scales. Basically, we don't know why the vacuum energy we get from the standard model gravitates so weakly, so there are models that change the behavior of gravity so that it dies faster than 1/r",
" after some scale."
] |
[
"Ohhh...good question. Currently, most scientists would say no. However, there is some very wacky and not well-understood stuff happening on very large scales. For example, on the scale of galaxies, the stars and solar systems do not have the proper angular velocities. To account for this we have created a concept of 'dark matter' to balance out the missing mass necessary to keep the stars in their orbits. ",
"So who knows, maybe some other heretofore unseen force is waiting for us to discover it. "
] |
[
"What's determines the temperature of a star?"
] |
[
false
] |
[deleted]
|
[
"This is really a big issue and there's a whole field dedicated to \"stellar evolution\" and all its complexities!",
"Stars can change their temperatures throughout their life. Our sun is a yellow-white star, but it will eventually expand and turn into a cool red giant, before puffing off its outer layers and settling down into a tiny but superhot white dwarf.",
"The temperature of a star in the \"main sequence\" - that is, not counting when it goes into a red giant etc - depends on its mass. Here it's the opposite of what you guessed: the more massive the star, the hotter it is. So you have big bright blue stars, and small dim red stars, and things like our Sun in the middle. The big blue stars burn their fuel much more quickly than the small red stars, even though they have more mass. They can burn themselves out and go supernova in just a few million years, while small dim red stars can last for billions of years.",
"So in general, blue stars have formed recently, while yellow to red stars are older. In our galaxy, we have bright blue stars in the spiral arms, where stars have recently formed, and redder stars elsewhere.",
"As a side note: I actually do simulations of galaxies for my research, so if you have specific questions about computational methods etc, I'm happy to answer :)"
] |
[
"Stars don't accrete much mass after they have formed, the mass of a star is set by the so called Initial Mass Function, basically how much gas is around when it forms.",
"The reason blue stars \"have formed recently\" is that there aren't any blue stars around, that haven't formed recently, because they have a very limited live time. After that they leave the main sequence and go boom."
] |
[
"Thank you very much for your response.",
"Another question: You say that blue stars have formed recently. Now wouldn't you expect that new stars are smaller?"
] |
[
"Can anyone explain this phenomenon?"
] |
[
false
] |
[deleted]
|
[
"Ever seen one of ",
"these",
"?",
"The ",
"glow discharge",
" will follow your finger across the surface of the plasma ball because your finger is acting like an antenna for the AC frequency in the discharge. (more or less)",
"The fluorescent lights work in the same way, but apparently they didn't fully ionize enough to get the arc connect the ends of the tube, instead a weak glow discharge formed at either end, due to the local electric fields near the electrodes in the tube.",
"Drawing your fingers along the tube makes the glow discharge follow your fingers in the same way as the plasma ball, and generally lowers the required energy for the arc to propagate. Once the two glow discharges meet in the middle, the circuit is completed, and instead of two low power glow discharges, you get a continuous arc down the tube, dumping a lot more power, and properly lighting it. "
] |
[
"Shaking it could have helped, actually. There's a tiny drop of mercury in the tube that needs to become mercury vapor to sustain the arc. Shaking it could either distribute the liquid mercury more evenly, or distribute the heavier-than-air mercury vapor more evenly, especially if these tubes had been stored on end."
] |
[
"I'll take a stab at this. Fluorescent bulbs usually act as a negative resistive device, which means the voltage across the terminals decreases as more current flows through them. This is because more current means more power, which means more electrons being ripped off from gas molecules to form a plasma, which means more charged particles to carry the current. Since this is a positive feedback effect, if you don't limit the current with another device, you can end up breaking the bulb.",
"This is where the ",
"ballast",
" comes in, for which they usually use an inductor. The voltage across an inductor is proportional to the change in current through the inductor. This is a great ",
" device for fluorescent bulbs since they use a rapidly changing AC power source. ",
"Normally these two positive and negative feedback effects are in balance when the bulb is fully lit, but for your old bulbs, some other faulty electrical component made this balance out before the arc through the bulbs form. An arc is basically the line of bright plasma through which an established path of current flows.",
"My guess is your body acted as a crude antenna that allowed the current to penetrate deeper into tube until an arc could fully connect. Note that a gas turning into a plasma is a phase transition, so the resistance inside the plasma arc is much less than in the unlit gas. This means that after the arc is connected, the new equilibrium point for the system is the state of being fully lit.",
"Edit: Check out ",
"/u/Charyou-Tree",
"'s explanation as well. I had forgotten the term for glow discharge and it's good to know that glow discharges and arcs behave somewhat differently."
] |
[
"Are Dogs and Cats closely related in genetics?"
] |
[
false
] | null |
[
"Timetree.org",
" is a search engine to find the evolutionary split between two taxa / species - and the example on their start page is in fact \"cats and dogs\". :-)",
"See here,",
" they seem to have had a common ancestor some 50-60 million years ago.",
"For comparison, cats and humans split ~100 million years, cats and lions around 10 million years and cats and yeast around 1.2 billion years ago."
] |
[
"According to ",
"Wikipedia",
", the divide between Caniforms (dog-like animals) and Feliforms (cat-like animals) occurred very early on in the evolution of the order Carnivora, potentially as early as 42 million years ago.",
"Considering how far back that is, it's probably safe to say that dogs and cars are not very closely related at all besides superficial appearance.",
"EDIT: In fact, the number of chromosomes possessed by the domestic cat is 19, and the number of chromosomes possessed by a dog is 39. They are not very closely related at all, and are largely a product of common ancestry 42 million years ago and subsequent parallel evolution."
] |
[
"I was just looking that up! Wikipedia cites ",
"this article from 2006 (PDF)",
", which places the split \"around\" 42 million years ago. But that doesn't seem to be considered authoritative, because Google points me to ",
"this review from 2009",
" that still puts it anywhere from 40 Ma to ~66 Ma.",
"I'm not arguing with your point in the least, but now I'm curious. Can you (or anyone) clarify what the modern consensus is, if there is one? Bottom line, does Wikipedia need to add a caveat?"
] |
[
"Is any number over infinity considered real?"
] |
[
false
] | null |
[
"\"Dividing by infinity\" is meaningless if you're dealing with real numbers. You can define the ",
"extended real numbers",
", which is just the set containing all real numbers, positive infinity, and negative infinity.",
"Then you can extend the typical arithmetic operations to include infinity. For example adding infinity to any real number gives you back infinity, dividing any real number by infinity gives you zero, etc."
] |
[
"Just a follow up. Would that mean that infinity over infinity would be 1? "
] |
[
"You can see a list of the conventionally defined operations ",
"here",
"."
] |
[
"Can I be tasered while I am touching a lighting rod?"
] |
[
false
] |
The lighting rod I just mean my body is grounded.
|
[
"Tasers fire two electrodes that stick into you. The current flows in a closed circuit: taser -> electrode -> you -> other electrode -> taser. Current flow in that circuit is not affected by touching a grounded object.",
"EDIT: What would probably work to some extent is wrapping your entire body in aluminum foil. The foil would provide a low-resistance path between the electrodes and divert most of the current flow away from your body. It still wouldn't matter whether the foil was grounded or not."
] |
[
"They care very much, because if there is net current from the taser to ground, the taser will accumulate a voltage.",
"Back of the envelope: If a taser fired 2 mA average for 10 seconds, that would be a net charge of 20 mC. Modeling the taser as a 5 cm diameter sphere (the spherical taser approximation), its capacitance is about 3 pF and it would rise to about 700,000,000 V.",
"This is why we need closed loops for circuits."
] |
[
"Removing electrons from an object gives it a net amount of electric charge. That charge then creates an electric field from the object, and an electric field creates a voltage."
] |
[
"Can you break or bend the rules of the \"Fire Triangle\"?"
] |
[
false
] |
In school, we were taught about the Fire Triangle; the three requirements for fire, those being fuel, heat, and oxygen. Being that this was middle school (I think) I assume this was a dumbed down or simplistic version. What are some ways these rules can be subverted? Is it possible to replace oxygen with another gas, or perhaps start a fire without heat?
|
[
"To varying degrees, yes!",
"As was noted in another thread a few days ago, anything combusted by oxygen will still react with fluorine (and the original fuel will as well) in what is essentially a fire. Such environments are... uncommon, however. ",
"Heat is an inescapable requirement, but the amount required can be extraordinarily low. Hypergolic combustion occurs when two chemicals burn simply by being in contact with one another, and the temperatures at which this reaction still occurs is very low indeed. Outside of a rocket or a lab you probably won't find these substances though. ",
"I think the fire triangle is \"technically\" an over simplification, but for 99.99999% of the population in 99.99999999% of all situations, it is an accurate depiction of what is required for a fire.",
"Edit: it should be noted that oxygen can be provided by an oxidizing agent as well as free oxygen. Probably the most common occurrence of this is in bullets : along with gunpowder, an oxidizing agent allows the shot to be fired underwater or even in a vacuum."
] |
[
"I wouldn’t characterize the Fire Triangle as dumbed down or simplistic. I would characterize it as practical and everyday. What you’re asking for are interesting yet unlikely “edge cases” few people will ever see outside of a chemistry lab."
] |
[
"anything above absolute zero",
"Is going to give you difficulty, as all reactions require some enthalpy (heat) to get started. Depends on your oxidizer and your reducer.",
"The benefit here is that burning also produces heat, so it's self sustaining "
] |
[
"Can homogeneous isotropic turbulent eddies and vortex sheets during the formation of the universe, say when the universe was a 'continuum' before all the expansion...etc, be used to explain why the current state of the universe contains galactic clusters, superclusters, filaments and voids?"
] |
[
false
] |
Ok, Fluids Guy here: Does pressure and especially viscosity exist in any meaningful way at the scale of the universe? I mean clearly the universe is not a continuum anymore, but was it ever if it has always been infinite? Does the Reynolds number (ratio of inertial to viscous forces) mean anything on the scales of the early universe? What was the 'viscosity' of matter? Are there even estimates for what types of 'viscous' forces there are at such immense pressures and temperatures? Is there any force on a galactic scale in the universe which plays the role of 'viscous' dissipation or drag, because gravity is completely conservative...?? In the absence of such a viscous force, could the univsere be 'suffering' from the 2-D turbulence 'inverse energy' cascade? Hence, unbounded vortex (galactic) growth.. i.e. the universe is accellerating in it's expansion because energy feeds upwards? It's a huge conservative field... except for the role black holes play? I was speaking to a physicist friend recently. As I recall, he says that the Reynolds number of the early universe was quite low, so that turbulence was not possible until things cooled off and the viscosity declined sufficiently. I suppose he would say that the lumpiness in the current mass distribution is due to quantum fluctuations at the Big Bang. Any other theories? Thoughts?
|
[
"The people who study this stuff say that gravity alone is sufficient to explain the current structures in the universe."
] |
[
"Damn, good questions. I can say that simulations have shown that gravity, itself, is able to create the filamentous macro structures observed in the universe.",
"Even with a conservative force such as gravity, there is still some sort of dissipation---when galaxies \"collide,\" momentum is transferred between bodies. In a gaskinetic sense, that is a viscosity. Additionally, when bodies make close gravitational passes, the differential forces cause slight deformations in the bodies, and energy is converted to heat. This is happening even in the Earth-moon system (",
"http://en.wikipedia.org/wiki/Orbit_of_the_Moon#Tidal_evolution",
")."
] |
[
"Is that where Dark Matter comes in?"
] |
[
"It this is true or just part ? (show flash)"
] |
[
false
] | null |
[
"Anything you see on Arrow or Flash to do with science, medicine or technology is going to be pretty much 100% made up.",
"For the mirror to do what they're proposing, it would have to have been kept in complete darkness before and after the lightning flashes, or the images would have been overexposed. If you have photo film in a camera and you expose it to bright light before developing, there would be no useful images. Have a look through the ",
"photo processing article in Wikipedia",
".",
"The other thing is that while silver nitrate was used as a backing for mirrors, it's ",
"silver halides",
" that are used in photography. Either way, you need to keep the silver salts in the dark prior to exposing them to what you want to image, and until they are treated to fix the image."
] |
[
"No, because as soon as you exposed the photosensitive surface to light it would ruin any potential picture. Mirrors spend a lot of time out of the dark, that's kind of how they work."
] |
[
"No, because as soon as you exposed the photosensitive surface to light it would ruin any potential picture. Mirrors spend a lot of time out of the dark, that's kind of how they work."
] |
[
"What is the relationship between partially hydrogenated oils and trans fats?"
] |
[
false
] | null |
[
"Cell membranes are composed of various types of oils. This composition varies with temperature, as the cell adds or removes particular oils. The aim of that modulation is to keep the fluidity of the membrane at an ideal point. When the membrane gets too solid, the cell can add in these poorly-packing cis fats to increase the fluidity. If it adds in a trans fat instead, this will actually decrease the fluidity.",
"I don't know why ",
" bad. Maybe the fluidity of the membrane alters the ability of a cell to take up materials from outside by diffusion, or it affects the functions of proteins embedded in the membrane, or prevents the cell from reshaping itself (vital for some types). In any case, it is a bad thing.",
"(That's probably only one example, the most obvious one - I don't know a whole lot about trans fats, but I'd imagine they cause other problems too.)"
] |
[
"\"Partially hydrogenated oils\" include trans fats and cis fats, which are both types of unsaturated fat.",
"Both contain a point, or points, at which hydrogen doesn't saturate the carbon skeleton; at these points, cis bonds introduce a kink in the line of the fat, whereas trans bonds maintain a linear shape. As a result, trans fats pack together much more easily than cis fats, and have a higher melting point. Trans fats generally don't exist in nature, and the body doesn't recognise them as being different from cis forms, so it incorporates trans fats into places they shouldn't be."
] |
[
"What do you mean by \"places they shouldn't be?\" What is it exactly that trans fats are doing that they have such a reputation for being unhealthy?"
] |
[
"How do Lagrange points L4 and L5 work? Are they always at a 60° between two bodies?"
] |
[
false
] |
L1, L2, and L3 are all pretty easy to imagine, with addition and negation of gravitational forces and all that, but how exactly to L4 and L5 work, and what makes them exist at the end of an equilateral triangle?
|
[
"Lagrange points come from the restricted circular 3-body problem (hereafter 'RC3BP'; two massive bodies with one massless 'test particle', restricted -> 2-dimensional, circular -> the orbits of the massive bodies around each other are circular). The assumptions of this problem are never fully satisfied in a real system, but where those assumptions are close to being met the RC3BP offers good insight into the orbital dynamics.",
"From ",
"Wikipedia: Lagrangian point",
":",
"The reason these points are in balance is that, at L4 and L5, the distances to the two masses are equal. Accordingly, the gravitational forces from the two massive bodies are in the same ratio as the masses of the two bodies, and so the resultant force acts through the barycenter of the system; additionally, the geometry of the triangle ensures that the resultant acceleration is to the distance from the barycenter in the same ratio as for the two massive bodies. The barycenter being both the center of mass and center of rotation of the system, this resultant force is exactly that required to keep a body at the Lagrange point in orbital equilibrium with the rest of the system."
] |
[
"I hope you don't mind if I throw in a bonus question too. How would a rocket fly out to say earth sun L4? Does it first need to go into earth orbit and somehow get stuck in L4? Or can you just fly straight there?"
] |
[
"Going to Earth-Sun L4 or L5 requires ",
" fuel then going into LEO. To get the Earth-Sun L4/L5, you need to effectively escape the Earth's sphere of influence. Escape trajectories require ~1.4x more delta-V (aka fuel) than circular orbits."
] |
[
"What would you see/feel as the earth collided with a Jupiter sized gas planet?"
] |
[
false
] | null |
[
"I like this question... I'll take a stab based on what I know, but I think an astronomer would still be able to win the day (disclaimer: I am not an astronomer; I'm actually an engineer).",
"I guess the first question is the trajectory these planets are taking: the most likely path (in which a collision is assured) seems like it would involve the planets ",
"spiraling into each other",
", which would have all sorts of drag effects on the rotation of the Earth and mess up the tide long before the planets actually collided. We might see the atmosphere siphoned towards Jupiter before the upper layers of the two planet atmospheres even collided, depending on the orbit. ",
"Let's not even get into the possibility of tidal heating",
". But in the spirit of making fun assumptions, I'll assume these planets are actually geared for a head-on collision.",
"We know Jupiter's gases are ",
"mostly comprised of hydrogen",
", which we know can ",
"ignite fairly easily",
" in terrestrial environments. So assuming you were bolted down to the Earth's surface, you'd probably see some fantastic explosions as hydrogen gas vented from Jupiter's atmosphere interacted with the oxygen in Earth's atmosphere. However, it wouldn't take too long for poor Earth's meager atmosphere to get completely dispersed by Jupiter's stronger gravity.",
"Jupiter's gravitational pull is about 2.5 times that of Earth's (it's really not that dense), so I think from there you can extrapolate at what point you would \"fall off the earth,\" but this math eludes me."
] |
[
"All kinds of crazy shit",
"I like this science."
] |
[
"Question: Since the Earth (and everything on it) would be falling into Jupiter at an equal speed, wouldn't you stay more or less on the Earth's surface? At least until you actually hit the planet and you had to take all sorts of friction/drag/air resistance into account."
] |
[
"Has an experiment or apparatus ever been used to convert energy into matter?"
] |
[
false
] | null |
[
"Particle Accelerators routinely do this. They take energy and make matter (particles) from it."
] |
[
"To be clear, I was under the impression that they used the energy to accelerate existing matter and then impact it, causing destabilization of the high order particles allowing us to detect the lower order particles. Is that the case, or does the impact ultimately yield a mass gain at the loss of energy invested?"
] |
[
"Well... here is an ",
"interesting article",
" I just found where they actually made an electron and positron from photons."
] |
[
"Why are humans not capable of the net synthesis of glucose from acetyl-CoA?"
] |
[
false
] |
I understand that other organisms use the glyoxylate cycle to generate large amounts oxaloacetate from acetyl-CoA, which can then move up the pathway to gluconeogenesis. But why is this not possible through the citric acid cycle? What mechanism in the citric acid cycle prevents the net synthesis of oxaloacetate?
|
[
"In the TCA cycle, carbons are lost in the form of CO2 in the conversion of isocitrate to a-ketoglutarate, and again in the conversion of a-ketoglutarate to succinyl CoA. The glyoxylate cycle bypasses these two steps and converts isocitrate to succinate and glyoxylate. The succinate can continue to participate in the rest of the TCA cycle, and the gyoxylate provides the excess carbons (that would normally be lost) which can be used for anabolic purposes."
] |
[
"Yes. Humans (and I think all vertebrates?) do not have the enzyme isocitrate lyase, which would allow isocitrate to bypass the steps I mentioned above."
] |
[
"Ah. Okay.\nSo the carbons that would otherwise net oxaloacetate are lost in CO2, yes?"
] |
[
"How high a resolution camera would be required to be able to digitally zoom in a view individual atoms?"
] |
[
false
] |
...and if it is possible, how long do you think it will be until we have such a camera?
|
[
"Optical (light-based) cameras will never be able to see individual atoms. Atoms are smaller than the wavelength of visible light, so it cannot be used to see them. It simply cannot provide the resolution necessary. You might be able to use gamma rays because they have a much much smaller wavelength, but you would likely damage both your viewing equipment and the thing you're observing in doing so. "
] |
[
"http://www.youtube.com/watch?v=XEZtw1yt8Kc",
"This might help."
] |
[
"The problem with that is that the pixels themselves are much much larger than atoms. We have special methods of imaging atoms in which we bounce electrons off of them and interpret the image from the returning electrons, called an electron microscope. I am no expert in the field of digital cameras but I am a physics/chem major and I dont really see it being possible to image an atom using a CCD imaging device. We can image galaxies millions, even billions of light years away with ccd however it requires a tremendous lense, or other type of imaging device. I just dont see how it could ever be feasible to actually image an individual atom with a ccd. The pixels would have to be smaller than the atom in question."
] |
[
"What does a carbon notch in a FLIR do?"
] |
[
false
] |
The BriteStar Block 2, the FLIR found on the UH-1Y, has a detector element that sees Mid-IR energy in the 3.6-4.2 & 4.6-5.0 micron ranges. The 4.2-4.6 micron range has been filtered out, and is referred to as the carbon notch. Can someone please explain what the carbon notch is?
|
[
"Carbon dioxide absorbs infrared radiation in the 4.2-4.6 micron range",
", this means it also emits in the 4.2-4.6 micron range.",
"Carbon dioxide is present in our atmosphere.",
"To effectively see through the atmosphere you need to filter out the spurious emission and absorption due to the carbon dioxide. I've not seen it referred to as a carbon notch before, it is usually called a CO2 notch.",
"FLIR say that the filter is a",
"\"Cooled CO2 Notch Filter option for reduced atmospheric attenuation\""
] |
[
"So basically, if it wasn't filtered out, the carbon would act like a wall, preventing the IR energy from reaching the detector?"
] |
[
"No- it only absorbs/emits in that specific range. But CO2 is everywhere and sometimes you don't want to see it. FLIR typically only indicates the total infrared of all wavelengths observed. CO2 could obscure the image."
] |
[
"What kind of carbon do people use when a chemical formula has Carbon in it?"
] |
[
false
] | null |
[
"What do you mean by \"kind\"? Do you mean isotope?"
] |
[
"No not like isotope like graphite coal diamonds Co2 or is there like a carbon gas or carbon powder ?"
] |
[
"Carbon is the atom itself, graphite, coal or diamond are just ways those carbon atoms can be arranged. In a chemical formula like CH4 (methane) for example you just say that the carbon atome is stuck to 4 hydrogen atoms. It is not in graphite or diamond form, it is just in CH4 form."
] |
[
"We have iron in our blood, how strong a magnet would we need before we could pick up a mouse? A person?"
] |
[
false
] | null |
[
"Please post calculation requests to ",
"/r/estimation",
" or ",
"/r/theydidthemath"
] |
[
"Crosspost or delete this one?"
] |
[
"Already removed"
] |
[
"If we didn't have observational data, would there be any reason to think that the speed of light is constant in all reference frames?"
] |
[
false
] |
Perhaps another way of putting it is, is there some underlying principal that explains why it is that the speed of light is constant, rather than time or space or something else?
|
[
"all science is based on ",
" kind of observational data. If you mean \"aside from watching light move in different frames, how else do we see the effects of relativity?\" Well we would see that there is a fundamental limit on the speed of any kind of information in our universe. Anything that is massless must travel at this speed of information, and anything with mass must travel slower than that speed."
] |
[
"Yes, you could make that claim from examining Maxwell's equations."
] |
[
"The Michelson-Morley experiment was designed to gather data on the luminiferous aether. The surprise was that the results seemed to be that there was no luminiferous aether. Maxwell's equations combined all forms of electromagnetic radiation into electromagnetic waves with the catch that light had to always be traveling at c, regardless of the frame of reference. The aether was therefore required, not only because as a wave light needed a medium to propagate, but also because ",
" was meant to be the absolute reference frame for light. The surprise was that there was no aether, and in proving this, another explanation, relativity, was devised for the reference frame of light. "
] |
[
"Why do different types of ticks carry different diseases and coinfections while populating the same area and eating the same bloodmeals? E.G. red meat allergy being limited to lone star ticks and dog ticks not carrying Lyme?"
] |
[
false
] |
Why is it you are not likely to contract Lyme disease from a dog tick, but, you are from a deer tick? They both carry infectious disease, they both feed in the same territory, and they are both bloodmeal parasites. The same goes with the famous red meat allergy you can contract with a lone star tick. How does the type of tick vary which also varies your risk to tick borne illnesses?
|
[
"The animal has to be a vector for the disease as well. A bacteria or virus will be evolutionarily adapted to being in a specific host body than another. So even if they fed on the same blood, a specific bacteria/virus/parasite might not be able to propagate in certain hosts. It's the reason why not every disease any animal has can be transmitted to other animals or humans."
] |
[
"different ticks have different preferred hosts. immature deer ticks often feed on mice, which carry lyme disease, and the adults very much prefer white-tailed deer and other larger mammals. This allows the lyme disease to transfer to the larger mammal. Dog ticks are more generalist and live in a larger range, but still don't transfer lyme disease. Lone star ticks will feed on medium-small mammals as immatures, like rabbits and raccoons, and adult lone star ticks will feed on anything warm blooded and medium or large. In addition to having different hosts, lone star tick saliva kills lyme disease. ",
"A lot of diseases transferred this way have precise needs in an intermediary host as well as the primary and end host. Malaria needs both the mosquito anatomy and behavior to be just right in order to infect a new host."
] |
[
"Since Dog ticks are more generalized and feed on the same mice presumably, wouldn't that make them eligible to pick up the same vector as deer ticks?"
] |
[
"Is it possible for organic life to exist that isn't carbon-based?"
] |
[
false
] | null |
[
"No, by definition. Organic materials must contain carbon.",
"As for carbon based life, it's possible in theory. Silicon is the most likely contender since it can form similar molecules to carbon. "
] |
[
"It's reasonably likely that the study that found that was mistaken. ",
"http://www.nature.com/news/2011/110809/full/news.2011.469.html"
] |
[
"Not only was that study poorly executed and never replicated, but it was never hypothesized that the bacteria were not carbon based - only that arsenic was substituting for phosphorus in nucleic acids."
] |
[
"Why are animal clones so prone to early deaths?"
] |
[
false
] |
Every time I here about clones they always seem to be much more susceptible to diseases and genetic disorders. If they are genetically the same to there counterpart why do they die early so much more often?
|
[
"Our genes have ",
"telomeres",
" on the end of them. Telomeres are repetitive portions of genes that protect the gene from deterioration. Every time a gene replicates, a little bit of the telomere is cleaved off. Eventually, the telomeres run out, and when a cell replicates a bit of useful gene is cleaved. This can lead to cell death if too much 'good gene' is cleaved. ",
"When things are cloned, cells are taken from the parent who has already undergone some sort of aging. Their telomeres have already been shortened. So the clone is born with short telomeres and cells will begin degenerating earlier than their natural born counterparts. "
] |
[
"I need to correct a few errors in this answer seeing how I'm doing postdoctoral research on telomerase.",
"Our genes do not have telomeres on the end, our chromosomes do.",
"A little of bit of the telomere is not cleaved off. ",
"During chromosomal replication you unwind double stranded DNA, which results in two complementary single strands. DNA polymerase requires a free 3'-OH to add the next base and so another enzyme, primase makes a small piece of RNA complementary to the DNA. This allows DNA polymerase to begin replication by adding bases to the end of the RNA primer that are complementary to the template DNA strand.",
"DNA polymerase can only add nucleotides in one direction (5'->3'). So, whereas on one strand of DNA, DNA polymerase can run straight through, on the other strand (the lagging strand) it has to continually replicate away from the origin—where the double stranded DNA is being separated—from many RNA primers laid down by primase. ",
"After replication is complete, the RNA primers are removed, leaving behind a free DNA 3'-OH that DNA polymerase can now elongate from, effectively filling in the gaps left by the removed RNA primers. Unfortunately, ",
", after its removal DNA polymerase would not have a free 3'-OH to fill in the gap. Therefore, after each round of DNA replication, a single stranded 3' overhang remains with its complement not existing.",
"I like this video: ",
"http://www.youtube.com/watch?v=AJNoTmWsE0s",
"Humans have ~>3000-base long telomeres. The telomeric repeat in humans is TTAGGG. After each round of division, the cell loses some telomeric repeats. The 3' overhang recruits many small proteins that make up the shelterin complex, protecting the end from being recognized by cellular machinery designed to degrade single-stranded DNA. Once the length of the telomere falls below a threshold, the shelterin proteins being to lose affinity and dissociate. This leads to a signaling cascase that results in cellular senescence—the cells not dividing, just living (",
"., cellular retirement :)—and usually apoptosis.",
"If the shelterin signals are not effective in shutting down replication, chromosomal endjoining occurs, which leads to a whole new set of apoptotic signals.",
"Yes, eventually, continual replication will erode genes near the telomere, but chromosomal endjoining prevents this. This is one way cancer cells can avoid the loss of genetic information during rapid cel division.",
"As I'm sure you're all well aware, there exists a reverse transcriptase that contains an RNA template complementary to our telomeric repeat (AATCCC) known as telomearse. It has the capibility of recognizing the 3' overhang and adding DNA complementary to it thus maintaining and even elongating the telomere. The vast majority of cancer cells have highly active telomerase, whereas most normal cells in our bodies have no detectible telomerase activity. This is why telomerase is such an attractive target for cancer therapy—tamp down telomerase activity and you may allow the cells normal apoptotic pathways to halt cell division. Unfortunately, most cancer cells have accumulated many mutations that inhibit many apoptotic pathways, but a telomerase inhibitor is still very likely to increase the efficacy of cancer treatment by slowing down cellular proliferation by increasing chromosomal end-joining, which can disrupt genomic fidelity.",
"Now, out of my field of expertise. ",
"When clones are created, I believe they take a somatic cell that indeed has lost some telomere length. IIRC, this does impact the lifespan and cancer rates of the organism, but DNA methylation and gene silencing also play a large role in the morbidity and mortality. During embriogenesis, gene regulation is central.",
"[EDIT] For clarity."
] |
[
"So if you clone a fetus, you wouldn't have that problem?"
] |
[
"will plasma moving through a coil produce electricity?"
] |
[
false
] |
pretty much the title, say i have a hot fast moving charged plasma and i pass it through a coil, will this produce electricity. my instincts say yes, but i'd like some confirmation from someone with a bit more of a background physics.
|
[
"Where exactly do you expect electricity?",
"If the plasma has a net charge (quite unusual) and moves through the coil you have a current flow. If this current flow changes with time you can get induction, although a coil around the current flow is not a good geometry to use it."
] |
[
"It won't work for a simple coil, but a slightly more complicated device will do that. If you move a plasma (or any conducting fluid) through a tube containing a magnetic field that's perpendicular to the flow, you'll create a voltage perpendicular to both field and flow. If you put electrodes on the side walls of the tube, you can generate power, converting the kinetic energy of the plasma into electrical energy.",
"For extra credit, you can make this self-starting, using the device itself to power the coils that create the magnetic field it needs to operate.",
"This is called a magnetohydrodynamic generator. It's not very practical, but it does work.",
"https://en.wikipedia.org/wiki/Magnetohydrodynamic_generator"
] |
[
"It will produce magnetic field if you somehow manage to move the same type of plasma charge particle in 1 direction .",
"You question is wrong from the basic . What you mean is electric current ? \n What you asking is basically \" if I drink Pepsi from a straw will it produce coca cola ?\""
] |
[
"Why do vegetarians get sick when they eat meat?"
] |
[
false
] |
I recently had a vegetarian friend eat chicken and get ill enough to puke. I was wondering why vegetarians gets sick when they eat meat. Also was wondering if someone who didn't eat meat in their first 15 years of life would be able to.
|
[
"I've seen several recent studies which show how different intestinal flora can be between individuals, and how differences in flora can lead to correlations with disease, behavior, and other vectors.",
"A vegan or vegetarian diet substantially alters the human colonic faecal microbiota",
"Commensal flora and the regulation of inflammatory and autoimmune responses"
] |
[
"Nausea and vomiting were likely psychosomatic in the case you described. I'd bet your friend didn't get sick until after they were told they ate meat. If you tell someone - anyone, not specific to vegetarians - that they ate something disgusting, there's a good chance they'll start feeling nauseated. If they dwell on it, they might even vomit. It's all in the mind. ",
"As for lower GI discomfort, any change in diet can cause short-term constipation, gas, diarrhea, etc. If you never eat vegetables, and tomorrow you decide to eat a large salad with every meal, you are going to be running for the bathroom a lot that day. Most of it has to do with how your intestinal flora react to the food you eat. ",
"There's nothing special about vegetarians and meat. Some vegetarians claim that their body \"rejects\" meat, but in reality, their bowels would be back to regular schedule in no time if they started eating meat again. They might get diarrhea or discomfort in the hours after switching back, but things will be back to normal within a day. "
] |
[
"I was a vegetarian a few years back, for nearly a year. Decided to start eating meat again; the chicken went down fine. I also know someone who was a vegetarian for 10+ years, decided one day to eat a big ol' steak and felt perfectly fine afterward. So just as extra insight, in our experiences, there was no ill-effect from the sudden change in diet. "
] |
[
"Can two moons of a planet, over the long term, share the same orbit height/apogee/perigee but with different angle, without colliding?"
] |
[
false
] |
E.g. two moons, both in a circular 300,000 km high orbit around their planet, but one is equatorial and the other polar (or another angle, but not equatorial). Assuming we ignore how such an orbit came to exist, can it remain stable over the long term? By that I imply that the orbits actively keep each other form being on a collision course, using similar mechanics to orbital resonance.
|
[
"https://en.wikipedia.org/wiki/Co-orbital_configuration",
" may or may not be helpful. he ",
"Saturnian",
" moons ",
"Janus",
") and ",
"Epimetheus",
") and probably the most famous examples. However, I don't think they exactly share an apogee or perigee (which would technically be an apoapsis and periapsis, since 'gee' only refers to Earth)"
] |
[
"No. If they are not on the same plane then the system would be unstable due to the Kozai mechanism (although as a side point a system could not evolve to this configuration anyway). One of the bodies (the lighter of the two) would be excited to a higher eccentricity (also likely its inclination with respect to the host planet would change). Not really sure what the end result would be as this is not a realistic configuration to consider."
] |
[
"They also have the same orbital plane. I don't see how such a setup would be possible with different orbital planes."
] |
[
"Why does thermodynamic data differ between sources so much?"
] |
[
false
] | null |
[
"As these quantities are experimentally determined, it's going to vary on the source the data is from, but after some digging, BaO's discrepancy has a neat history:",
"-556 kJ/mol - L. Brewer, Chern Revs. 52, 13 (1953).",
"-590 kJ/mol - G. C Fitzgibbon et al. J. Chem. Thermodynamics, 577 (1973).",
"-548 kJ/mol - Chase, Malcolm W., et al. \"JANAF thermochemical tables, 1975 supplement.\" Journal of physical and chemical reference data 4.1 (1975): 1-176.",
"I can keep going, there's a couple dozen unique experimental results published in the literature and they all split between roughly -590 and -550 kJ/mol, I ignored the reference handbooks which refer to these citations anyway. This is because experimenters will attain these values from different reactions, better or worse instruments and sometimes just plain old error. However, on top of that, there is indeed a serious problem with BaO measurements, let's check out the literature! If you'll notice, Chase (whose review is used by NIST Chemical Handbook) is listed for 1975, here's what he said about the enthalpy of formation for BaO in 1975:",
"\"The new value [-548 kJ/mol] is preferred since both reactions were run in the same calorimeter on samples that were well characterized. The latter is particularly important since impurities were a major problem in studies [lists several older studies]. [...] ",
"\"Combustion studies of Fitzgibbon et al. suggest that negative bias of [enthalpy of formation] was due to partial dissolution of he crucible lining in molten BaO formed in the combustion. Dissolution was eliminated in combustion on sintered MgO disks, but large amounts of BaO2 were formed both in this case and with the use of BaO crucibles. This led the authors to dismiss combustion calorimetry in favor of solution calorimetry. [Earlier author] noted earlier that the combustion result was incompatible with data for BaCl2 (aq) [and other reagents], also a similar discrepancy existed for SrO. We find that the combustion value is incompatible with equilibrium data [...]\"",
"Alright. Basically, what Chase is saying is that for some reason the method of combustion calorimetry is flawed, pushing the enthalpy of formation more negative than it should be. He notes the same problem happening for strontium oxide as well which is chemically similar to barium oxide. So essentially, the discrepancy in the literature you make note of is some systematic error common to some of the literature on the subject. The true formation enthalpy seems to be hovering towards the less negative value. If you're still curious, check out some of the literature and you'll see vigorous debate in the calorimetry community about best practices and biases found in different reactions."
] |
[
"Great answer! Living up to your username"
] |
[
"What is the feeling towards enthalpy of formation from computational sources (quantum chemistry)?"
] |
[
"Can the flu virus from previous years help bolster your immune system against this year's strain despite the fact that it's a mutation of the same virus?"
] |
[
false
] |
A few years ago I got the flu for the first time, and I was bedridden and vomiting for about five days straight. This past weekend I got what felt like the flu, with the congestion and body aches/headaches, but I'm basically over it now and it seems tame compared to my previous bout with the flu. My utter lack of diagnostic skills notwithstanding, is there any way previous flu viruses help your immune system recognize the current mutation, even though it's not technically the same virus? I mean it's still "the flu", right?
|
[
"There is a selection process which happens when different flu strains make the leap from animals to humans. The strains which encounter antibodies capable of recognising them are unable to establish themselves in the human population and do not spread very well. So, each new strain of flu that arises should not be very well recognized by your immune system. ",
"However, the flu virus is a highly polymorphic bug that can take on many permutations. Some versions are quite mild and these are in fact the most successful from the viral point of view since milder symptoms facilitate infection of many individuals. ",
"If what you had really was influenza then probably it was just a milder version of it. It is possible but unlikely that your previous encounter with the disease helped."
] |
[
"There are lots of different strains of influenza, and these can range from being ineffective at causing disease, through mild symptoms, to the more severe symptoms. This is probably the major reason you had two different experiences.",
"However, it can also be explained by how influenza virus mutates. Influenza virus can undergo two types of mutations called antigenic drift and antigenic shift. Antigenic drift involves small mutations in the two main proteins on the viral surface responsible for recognition by the immune system. Depending on how major this change is, and how much the proteins are changed, the virus can either be recognised strongly, weakly, or not at all by the immune system's antibodies.",
"Antigenic shift, however, will lead to a completely new viral protein which won't at all be recognised by the immune system."
] |
[
"Influenza won't cause you to vomit. You likely didn't have influenza. In both of these cases, did you have a doctor verified case of flu? I would put my life savings on the bet that you didn't have the same virus in both these instances. I'd go double or nothing that neither instance was actually influenza. ",
"To answer your question: sometimes, not all the time. Even though there have been several different H1N1 flu epidemics (in 1918 and also in the 1970s) people that were alive for one or both of those epidemics were shown to have memory cells that fought the most recent 2009 H1N1 epidemic. They wouldn't be protected from, say, and H5N3 strain, though. "
] |
[
"In series circuit how can the current be the same on every consumer if each of them have different resistance?"
] |
[
false
] |
Not really very fun question, but, hell, I want an answer.
|
[
"From all my EE college professors: Think of current like water flowing through a series of connected pipes. Regardless of how wide or narrow the individual pipes may be, the same amount of water will flow through all pipes.",
"I hope this helps your understanding."
] |
[
"If the devices behave according to Ohm's Law, then each of them has a different voltage (V = IR). The sum of the individual voltages will equal the total voltage applied."
] |
[
"Think of it like a series of liquid tubes connected together. You have one fat one connected to a super skinny one, and then a moderately sized one. Now try to force water through them.",
"What you will find is that the flow rate of water through each tube is the same, but the pressure in each is different.",
"This is the same kind of idea as for circuits."
] |
[
"Breathe Nitrogen rather than Oxygen?"
] |
[
false
] |
Before I start, I have a very fundamental understanding of all sciences, only taking 101 and other introductory classes in college. So understand I'm aware this may be a ridiculous question, but I'm curious. I may also get some basic assumptions wrong, I apologize if this frustrates you like a simple misspelling would me. Okay, so humans and other carbon based lifeforms need Oxygen to breathe. As far as my understanding goes, the atmosphere is something around 70% nitrogen. Why is it that these life forms don't use Nitrogen as the primary form of "air"? OR, if that question is really stupid and obvious, is it possible for a form of evolution to occur sometime in the far future where we would depend more on Nitrogen (or other "air" source) rather than a disappearing oxygen? (Is oxygen even really disappearing?)
|
[
"Oxygen exists in the atmosphere as O2, but it is fairly reactive and can be incorporated into reactions easily. Iron rust is an example of how reactive oxygen is. ",
"Free O2",
" didn't exist in the atmosphere until photosynthetic organisms evolved, of which it is a byproduct. The organisms that first evolved photosynthesis were single celled and didn't 'breathe', however they probably used atmospheric CO2 just as plants do today. The majority of life on earth does not breathe oxygen just some heterotroph like animals.",
"Nitrogen is in the air as N2, which has a triple bond. This is very stable, and there are few organisms that can break this bond and use gaseous nitrogen. So even though nitrogen is extremely common, it can be a limiting factor for organisms, which is why ",
"nitrogen fixing",
" bacteria are so important for ecosystems.",
"edit: confused heterotroph and autotroph."
] |
[
"It's not really a ridiculous question, your question actually has a good idea behind it. For a compound to be useful in our metabolism in the same way that oxygen is, it has to be able to readily accept electrons from an outside source. Oxygen atoms, being very electronegative, is good at accepting electrons from everywhere. Nitrogen atoms are also fairly electronegative and should be able to fulfill that role, too. But we don't.",
"There are a few reasons that creatures don't use dinitrogen in their metabolic cycles. The first, and most important, is that the triple bond between the nitrogen atoms is exceedingly strong, and breaking it is not easy, even if the compounds you make from it are more stable than N2. The enzyme nitrogenase catalyzes the reduction of N2 to ammonia (NH3). This is an energetically favorable process, but actually making the reaction happen takes an awful lot of work, and the enzyme actually wastes energy to do so (though we're still not sure why). It's important to note that this enzyme doesn't use N2 for metabolism; rather, it's making ammonia to use as a chemical building block for proteins and other such things.",
"Now, there are actually metabolic cycles that utilize nitrogen compounds. If you check out the ",
"nitrogen cycle",
" on wikipedia, you'll see that there are lots of bacteria and fungi that thrive on nitrogen compounds in various oxidation states. The big stumbling block is that first step of turning dinitrogen into ammonia. From there, it's easy."
] |
[
"Since nitrogen is composed of nitrogen, and carbon dioxide is carbon and oxygen, yes, it is impossible for nitrogen to converted to carbon dioxide."
] |
[
"Could someone explain Quantum Computing to me?"
] |
[
false
] |
I'm trying to find more information about this, but everything seems overly complicated. Could someone explain the difference between traditional computing vs quantum computing? and what are the real world benefits of using one instead of the other? Thanks :)
|
[
"everything seems overly complicated.",
"It seems overly complicated, because everybody uses misleading analogies which fail to capture important elements, and then someone corrects them with a different misleading analogy..., and so forth.",
"The inherent difference is that classical computing is well described by classical states and processes, whereas quantum computing is efficiently describable by quantum states and processes, but not by classical states and processes.",
"To really get what's going on, you have to understand the basics of quantum mechanics. There are no shortcuts.",
"Quantum states can be described by normalized vectors in a \"Hilbert space\". A quantum bitstring has a Hilbert space of dimension 2",
" -- the same as the number of different classical bitstrings. Quantum evolution is rotation of these vectors. A measurement changes the state vector to point directly along one of these axes, with probability proportional to the square of the corresponding coordinate.",
"Quantum algorithms then involve choosing the right sets of rotations so that a final measurement at the end gives the right bitstring with high probability. ",
"The real world benefits of using a classical computer is that they actually exist.",
"In theory, quantum computers could be used to do certain specialized types of problems much faster -- primarily those with special symmetries that we can take advantage of. Without the the right quantum algorithm though, they'd take the same number of steps as classical computer, and each step would be much much slower."
] |
[
"With quantum computing, for every qubit you add, you increase the number of concurrent threads by a factor of two. Using a multicore processor, you'd have to increase the number of cores by a factor of two.",
"Basically with quantum computing, there's a pretty big hump to begin with, but then the number of simultaneous threads possible skyrockets pretty quickly."
] |
[
"The main issue is that quantum computing barely exists in reality yet. An example of the state of the art is a ",
"system with 14 qubits",
" which \"barely cleared the benchmark for fidelity.\" More robust systems of this kind have 8 qubits. A big issue for such systems is ",
"decoherence",
", which destroys your computation if the qubits have any atomic-level contact with the external environment.",
"There's also the ",
"D-Wave system",
", which uses a somewhat different approach, with its own tradeoffs. Their flagship commercial offering is specialized to do discrete optimization and costs $10m."
] |
[
"How does the Peltier effect work?"
] |
[
false
] |
So i keep finding really general science answers of WHAT it is. But Im looking for a step by step of what is happening and why to full comprehend how heat or cold is being turned into eletricity
|
[
"Essentially the same way as the photoelectric effect.",
"Metals all have a particular electron band energy. This means that when you put two metals in contact ",
"they develop a voltage",
". That's the same thing that causes galvanic corrosion; the metals can react chemically to gain/lose electrons that have flowed over the junction. ",
"The junction also acts kind of like an immensely weak diode, but the more important effect is that if an electron is liberated into the conduction band, it will be drawn across the junction by the voltage difference. In a solar cell, two layers of differently doped silicon create a diode, and photons energize electrons which are then pushed across the junction. The voltage gap across the diode determines which kind of photons can be absorbed. Photons that aren't powerful enough to liberate an electron get reflected normally. Photons that are too powerful have left over energy after liberating an electron, which also reflects.",
"In a thermopile the voltage difference is quite low. Visible photons can liberate electrons, but they have so much leftover energy that the efficiency is extremely low, and can be neglected. Heat (the ",
" of thermal energy) is a different matter. Heat is ",
"conducted by phonons",
", which are basically wiggles in the meterials structure. Say infrared radiation hits the metal- infrared is too weak to push electrons into the conduction band, but it can be absorbed by electrons that are already in the conduction band, giving them a little more velocity. Then that electron bounces into the other ones. It also passes by atoms and other parts of the crystal lattice, which causes a tiny distortion. The positively charged nuclei all move a little bit closer to the free electron- that movement is called a phonon.",
"The electrons causing the phonons don't contribute to electricity because they're random and they all cancel out in the large scale. The phonons can bounce into each other, combine, and do all kinds of things. Eventually, they can liberate a bound electron. If that electron bounces across the junction you've got electricity. Eventually another electron is dragged into the hole left over. If you've got a circuit set up, the electrons are dragged from the return wire, where electrons are lining up after having dropped their excess energy in the circuit. However any higher-energy electron in the conduction band is a much likelier candidate. Those electrons are more eager to drop to a more stable state and more likely to find a hole.",
"That's also why it only works with a flow of energy, and doesn't just convert temperature into electricity. If you've got both ends of a thermoelectric junction very hot, all the electrons that are being liberated are immediately being re-absorbed instead of moving across the junction. Electrons need to move to the hot side, where it will suddenly be much harder for them to drop back out of the conduction band. Since you can also have phonons can keep accelerating electrons across the entire gradient, not just the junction, the voltage depends on the thermal difference rather than the band gap.",
"This also tells you why you want thermoelectric materials to be as thermally insulating as possible- it creates a stronger gradient, making it less likely for electrons to drop back out of the conduction band. Note also that while I described metals, it also works for semiconductors and most thermopiles are semiconductors. Those are just a lot more complex."
] |
[
"You're thinking specific heat. Electron make a negligible contribution to the specific heat of metals, but they are the dominant way through which heat is transported. An electrical current is a heat current."
] |
[
"In metals the electrons are the major contributors to heat conduction, not phonons."
] |
[
"Are there any examples of two separate species of animals, or animals and plants, working towards a common goal, as a whole or in individual cases?"
] |
[
false
] | null |
[
"The biological term is symbiosis. It is when two species form a sort of relationship to the benefit of both. It could be something like the case of the tick-eating oxpecker (that little bird often seen on a rhinos and other large animals), or the nitrogen fixing bacteria in the roots of legumes. Symbiosis is common in nature.",
"Parasitism on the other hand, is a type of interaction in which one species gains at the expense of the other, in this case a host. Those blood-sucking ticks from earlier are a prime example of that. "
] |
[
"I don't know if I'm aloud to ask but I think this question don't deserve a post of it's own: Do animals of different species build physical structures (like bridges or holes) togheter? Has it been ever documented? "
] |
[
"Yes that has been observed in nature also. For example, bioluminescent bacteria lives in the light organ of bobtail squid which the squid feeds and in return, it emits light to hide the squid from predators.\n",
"https://en.wikipedia.org/wiki/Bobtail_squid",
"Or are you talking about two organisms \"building a house\" together and living in it?"
] |
[
"How did viral DNA become part of the human genome?"
] |
[
false
] |
There are some answers discussing how it was detected, or what they do, but none touch the topic of how viruses become part of our DNA. Specifically by what mechanism can anything external get integrated in anyone else dna?
|
[
"The life cycle of a virus goes as follows. A virus attaches to their specific host, then inject their genetic material into the host. The host then gets \"fooled\" into reading this material and making more and more viruses. Once there's so many viruses that the host can no longer perform the function to keep itself alive, it essentially explodes and releases the next generation of viruses into the world. ",
"Viruses can copy their DNA into their host for this purposes, but sometimes the virus is over powered or the cell survives infection and the genetic material the virus input is kept. If this happens in a gamete (sperm or egg cell) that goes on to be fertilized, that viral input is copied from the gamete to every daughter cell and voila, you have inserted viral genes into a multicellular organism."
] |
[
"Viruses are essentially little balls filled with genetic information and a couple of proteins that act like machines to help the viral genetic information get copied inside the cell. This involves taking the viral genome, converting it into a usable form, sticking it inside host cell ribosomes (protein making machines), and forcing them to make viral proteins. Most of the time, this happens outside the nucleus and often never involves DNA. However, for a certain type of viruses called retroviruses, converting the viral genome into a usable form involves a protein called reverse transcriptase. This takes viral genetic material and converts it into DNA just like what we have in our own cells. These retroviruses then trick host cells into taking that DNA inside the nucleus where it is slipped inside a chromosome."
] |
[
"In theory each generation would be an exact copy of its \"parent\" but mistakes can and do happen in the copying process so there can be slight differences in the next generation. Thats how the virus evolves. If these random errors in the copy end up making the new virus more successful there will me more of the variant"
] |
[
"Why is the reflection of a projector green?"
] |
[
false
] |
[deleted]
|
[
"Most projector screens have a coating of small reflective crystals of different sizes and shapes to increase the brightness at different viewing angles. (This differs from a \"retro-reflector\" where they try to return as much light as possible in a narrow cone back to the source.) ",
"The green could be coming from an interaction between the polarized light and these crystals at certain angles, (fresnel coefficient) or some portion of the green spectrum regardless of polarization is emitted at a specific angle to the light source as happens with water droplets and sunlight to produce a rainbow."
] |
[
"Most projector screens have a coating of small reflective crystals of different sizes and shapes to increase the brightness at different viewing angles. (This differs from a \"retro-reflector\" where they try to return as much light as possible in a narrow cone back to the source.) ",
"The green could be coming from an interaction between the polarized light and these crystals at certain angles, (fresnel coefficient) or some portion of the green spectrum regardless of polarization is emitted at a specific angle to the light source as happens with water droplets and sunlight to produce a rainbow."
] |
[
"It would be interesting to see if the effect disappears when the projection surface is a matte white material (low specularity). Also, how does the green patch appear through polarized lenses (3D glasses). Of course, you don't know if the polarization is linear or twisting..."
] |
[
"Would a perfect ball rolling on a perfect plane in a non-vacuum environment make a sound?"
] |
[
false
] |
[deleted]
|
[
"This crossed my mind also, but I didn't want to put it in there for fear of people chiding me on semantics. But I agree, without friction, the ball wouldn't \"roll\" but slide, and would only rotate if given a rotational spin independent of the surface friction. ",
"Like a bowling ball that both slides and rolls."
] |
[
"If there is a complete lack of friction can it still be said that the ball is rolling? Or is it just sliding at that point?"
] |
[
"If the ball is rolling at first, it continues to roll because of angular momentum conservation, i think"
] |
[
"Why is the circumference of a circle the derivative of its area?"
] |
[
false
] |
area = pi r circumference = 2pi r Is there a real reason as to why this is, or is it just a quirk of geometry?
|
[
"The derivative is the rate of change. If you think about it, going from a circle of radius r to radius r+h (where h is very small), the area will increase by approximately one circumference (2 pi r) times a thickness h. As h->0, this becomes simply 2 pi r, the circumference. That is a visual way of looking at it, I assume you already understand the algebra behind the derivative you mentioned."
] |
[
"It's easier to see this once if you realize that the derivative of area with respect to radius (dA/dr) is actually dA = 2πrdr, which, it's easy to see, is indeed the infinitesimal area added when you increase the radius by an amount dr."
] |
[
"If the \"radius\" of the square is r = s/2, then we have A = 4r",
" and P = 8r. The problem for ",
" shapes is, what is the \"radius\"?"
] |
[
"Did first generation stars have hydrogen planets?"
] |
[
false
] |
[deleted]
|
[
"We don't know for certain, as no first generation stars have been observed yet, as far as we know. If planets did form around some of those stars, they would be gas giants without the solid core that Jupiter is believed to have."
] |
[
"Yup, it definitely would.",
"Jupiter is a Jupiter-sized ball of hydrogen, its about 90/10 hydrogen/helium. Most of the gas giants are large balls of hydrogen that got large enough that the hydrogen could no longer exceed the escape velocity and get blown off."
] |
[
"Would a jupiter-sized ball of hydrogen have sufficient mass to prevent hydrogen from escaping its gravity?",
"That's basically Jupiter.",
"From wiki: ",
"The interior contains denser materials such that the distribution is roughly 71% hydrogen, 24% helium and 5% other elements by mass.",
"As far as I know, you don't need higher elements in order to start a protostar or proto-gas giant. Some astrophysicists correct me if this assumption is wrong. "
] |
[
"Do general anesthetics target a specific brain region or neuronal circuit?"
] |
[
false
] |
I understand that general anesthetics in most cases either increase GABAA activity or block NMDA channels (in the case of ketamine). But I can’t find an article that talks about where they target in the CNS. Obviously, exciting inhibitory neurons in different areas leads to different effects. Do general anesthetics target specific circuits or regions, or do they affect the brain globally? In that case how do they have selective functions (ie not messing with your vitals). Please correct me, as I’m more of a cog psych person than bio.
|
[
"I don't think there's much room for selectivity, we should be talking about the ",
" of CNS depression.",
"Talking about general anesthetics used to be easy, because you were just supposed to say that their mechanism of action was unknown. Nowadays, however, it's pretty much agreed upon where they act:",
"So, they work on neuronal membranes, and exert their effect most notably on synapses - they alter the release of neurotransmitters and the rate of neuronal firing. That's basically all we can say for sure, other than that it involves many mediators - GABA, glutamate, serotonin, probably a lot of others, too.",
"What is also agreed upon is, that there are several levels of CNS depression, meaning they depress brain structures ",
":"
] |
[
"This is a bit of a tangent, but might be of interest anyways. Dexmedetomidine induces sleep, but is not used as a general anaesthetic in humans. It is used for procedural sedation for non painful procedures and as an ICU sedative. The mechanism of action is rather different from the other medications used. It is a highly specific alpha-2 adrenergic agonist, and works primarily by inhibiting the locus ceruleus output to the ventrolateral preoptic nucleus. This causes a disinhibition of VLPON, and a switching of the orexinergic system initiating sleep. So it hijacks the specific sleep inducing circuitry of the brain 🙂",
"(This is all just of memory, so I apologize if details are off, but it should be pretty much what Millers anaesthesia said about it)"
] |
[
"Thanks for your response, and I understand that degree is more relevant than selectivity; but it seems the two go hand in hand. So going back to my question do we know why it targets those certain structures before others? Why, if you administer a specific amount that it will depress the cortex and subcortex, but nothing vital. I suppose nobody really knows, but there does seem to be some specificity to it."
] |
[
"Are there viruses that infect underwater/marine ecosystems?"
] |
[
false
] |
Are there viruses that infect underwater/marine ecosystems in the same way that COVID-19 (and other virus outbreaks) have infected aboveground ecosystems? If so, can we draw any conclusions about the transmissibility of viruses through the medium of water vs. the medium of air?
|
[
"Absolutely. As an example, recently there was an outbreak of ",
"Sea Star Wasting Disease",
" which killed a significant portion of all the starfish on the west coast of North America. It was caused by a single strand DNA virus. It was extremely virulent, and spread up and down the coast in fairly short order.",
"At the Vancouver Aquarium, even the starfish that were in the exhibits were infected. The Aquarium takes in sea water for their systems (with extensive filtration) but that didn't kill off the viruses."
] |
[
"Oh yes!! In fact viruses are by far the most numerous biological replicating entity in the ocean. The numbers are somewhat hard to believe and nearly impossible to put into perspective. There are an estimated 10 million viruses in every milliliter of surface sea water, meaning that every liter of sea water has more viruses than humans on the planet. It's estimated that the ocean contains 100 billion times more viruses than all of the grains of sand on earth. If you lined up all of these viruses side by side, they would span about 5.4x10",
" meters, or 12 trillion round-trips from Earth to Mars. ",
"Most of these are phage, which infect bacteria, and they have a dominating influence on the marine microbial community. I pulled all of these numbers from this ",
"review paper",
", which should be a good read if you are interested marine viruses."
] |
[
"Yup. That's how the coccolithophores ecosystem works, which is what created things like the white cliffs of dover. ",
"https://blogs.scientificamerican.com/expeditions/you-wanted-to-know-what-is-this-virus-that-infects-the-phytoplankton-part-one/",
"And here's a nifty little podcast on it:",
"https://www.wnycstudios.org/podcasts/radiolab/articles/190284-war-we-need"
] |
[
"When the sun expands to it's max in the latter stages of its life, will the conditions in any of the outer planets or their moons become ideal for life?"
] |
[
false
] |
If so, how much time will that new life have to thrive? I'm thinking, could we plant capsules in those planets to sit there and just wait for the right conditions.
|
[
"Maybe.",
"The inner planets will become too hot, and the gas giants are not ideal for life as we know it because of the immense pressures and lack of sunlight underneath their atmospheres. However, some of the gas planets' moons may be suitable for life.",
"There's not a lot of certainty in the calculations for the solar radius in 4 - 5 billion years, so it's difficult to give a precise answer. It is, however, billions of years from now, so \"sitting and waiting\" isn't really necessary - we could just wait a couple billion years. Practically speaking, your question is irrelevant at that point, as there's no telling what will happen to the human race between now and then.",
"http://www.astrobio.net/topic/solar-system/sun/living-in-a-dying-solar-system-part-1/",
"http://www.universetoday.com/12648/will-earth-survive-when-the-sun-becomes-a-red-giant/",
"http://www.universetoday.com/9472/outer-planets-could-warm-up-as-sun-dies/"
] |
[
"Very good point. Will we reach a moment where we'll say \"what's the point?\" And cease any effort to continue our race."
] |
[
"Maybe ten years later you fly off again because you want to see the crap nebula or something.",
"Who wants to go see the crap nebula? By our normal naming conventions, I doubt that it would be a very nice place.",
"Such a human existence as the self-sufficient spaceships is probably an inevitability, unless we blow ourselves up first. First issue will probably be reaching a point when we are no longer limited by the amount of energy we can gather/generate. After that, we work on condensing the time required to create things/recycle things and create more automation. At a certain point we should reach a critical mass, where we start living in a post-scarcity world."
] |
[
"Self-Fueling Pure Oxygen Car Engine"
] |
[
false
] | null |
[
"This has been removed because the question is based on fundamentally flawed premises. Please conduct some background research and revise if your question if you wish to resubmit.",
"Some of the most commonly seen mistakes are listed in the ",
"FAQ.",
" under respective fields."
] |
[
"That is my question though, what is that flawed premise?"
] |
[
"You would need energy to separate the oxygen from the air, and hence you'd need another energy source to do that first. Also, the energy density of air at room temperature and pressure would not be enough to run a modern sized car."
] |
[
"With the recent discovery of the new habitable planet, what \"checklist of events\" needs to happen?"
] |
[
false
] | null |
[
"Your question is very vague/open-ended, but here's the list as I see it:",
"Develop new propulsion technology. (Warning: speculation.) This will probably take hundreds of years for the type of leaps that must be made.",
"Travel to planet. Present-day unknowns like \"how to ensure the planet is habitable\" were likely solved during the hundreds of years to develop new propulsion.",
"Propulsion is critical because of the vast distance involved. The fastest man-made object (with respect to the Sun) is the Helios 2 probe. If we launched a spacecraft towards Tau Ceti (which I assume is the star/planet system to which you are referring, at 11.9 light years distance), with Helios-2-velocity, it would still take over 50,000 years to get there."
] |
[
"Do you mean \"checklist of events\" in terms of further studying the star and its planets, or do you mean developing interstellar spaceflight?"
] |
[
"Yeah sorry for the vague question. Just posted on a whim, but yes, I do mean interstellar space flight "
] |
[
"Why does hair come in just a few colors? And why these colors?"
] |
[
false
] |
As the title says - why can we only have different shades of a few specific colors of naural hair and why can hair only have one of these particular colors and not, say, green?
|
[
"Layman.",
"There are two major natural pigments found in hair. Eumelanin is black or brown. Pheomelanin yellow or red. Our hair colours are limited to what can be produced by mixing these two pigments in various quantities.",
"I can't say why we never evolved to produce another pigment (like a green pigment)."
] |
[
"Because humans did not evolve in forests, but in savannas."
] |
[
"Would green make you blend inn the forest?",
"BTW fun fact, there are no green mammal. "
] |
[
"Removing salt corrosion from FPLC machine"
] |
[
false
] |
Hello askscience, I work in a research lab where I run a couple of FPLC (fast protein liquid chromatography) machines. The fractionation machine that collects samples from the FPLC will occasionally spill salt-containing proteins onto its metallic base, which over time has led to a significant accumulation of salt and corrosion/pitting of the base. There are other minor salt spots on the FPLC itself. It turns out, salt is rather difficult to remove. Even the minor salt spots aren't really effectively removed with repeated scrubbing with water or dilute acetic acid. I've tried soaking the major salt spot on the fractionation machine in acetic acid to basically no effect. It's hard to find information about dealing with corrosion online. I've seen people advising applying an electric current to the corrosion and other sorts of complicated solutions. Being in a large research lab, I have an extensive amount of reagents at my disposal. So, askscience, is there a simple, straightforward solution to my problem? I'll be back at the lab for a bit shortly and may post a picture for reference.
|
[
"Try ",
"r/askscitech",
" as well."
] |
[
"I've not encountered this specific problem with FPLC, but I have cleaned some corrosion from labware (and battery terminals) using Coca-Cola, and oddly, it works well. So if you dont' want to mess with sugary things, maybe trying a fairly concentrated (pH < 4) phosphoric acid preparation would work."
] |
[
"Cola/phosphoric acid was actually one of the solutions I'd considered, but I never did try it. Thanks for the suggestion.",
"And yeah, this isn't a question that's really specific to FPLCs. It's just extra information."
] |
[
"Would an Argon-Oxygen atmosphere be breathable?"
] |
[
false
] |
Could humans breath an Argon-Oxygen atmosphere? For bonus points: what about a Neon-Oxygen atmosphere?
|
[
"Yes, although the act of breathing would require more effort due to density differences. The partial pressure of oxygen is the critical factor, and at an appropriate % of oxygen, the partial pressure is the same. ",
"Deep sea divers actually use ",
"oxygen-helium mix",
" to avoid complications at higher pressures with nitrogen. ",
"Noble gases at normal pressures would not be expected to have complications. ",
"Related topic, that scene in the movie \"The Abyss\" in which a rat breathes a liquid isn't fake, the stuff exists: ",
"https://en.wikipedia.org/wiki/Liquid_breathing",
"It's the viscosity that's the issue, our lungs aren't made to move fluids. "
] |
[
"Perfluorocarbons are mad shit! Good point about the viscosity problem.",
"I wonder if the blood could be infused with oxygen outside the body with an IV line, removing the need to breathe altogether. Maybe humans could get down to a kilometer this way? I get the feeling the OHS folks wouldn't like it, in any case."
] |
[
"It's been a long-term project to make synthetic blood actually:",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5084831/",
"There are problems, but the carrot of replacing the need for blood donors is a big deal."
] |
[
"Gravity sucks. But where and/or how does the rotation begin? We see rotation in the kitchen sink, the toilet, dust devils, tornadoes, hurricaines, our solar system, our sun, and our galaxy. WHY DOES EVERYTHING SPIN?"
] |
[
false
] | null |
[
"This usually has to do with conservation of angular momentum. Imagine a box filled with particles that travel in random directions at random velocities. All those particles together have a total angular momentum that is constant over time. If the particles start clumping together you will start to notice a rotation. If all particles eventually form one massive object, this object has the same angular momentum as the original cloud of particles and thus it will rotate around one axis. ",
"Bonus info: if the mass distribution of the object is not symmetric around this axis of rotation, the rotation will cause something similar to a torque and the axis of rotation will start to change over time (aka ",
"precession",
")."
] |
[
"I'm seeing lots of wrong answers. Conservation of angular momentum exists. It matters. That does not explain why a sink does not suck towards its center. It doesn't explain why galaxies and planets rotate about a center. How did they start rotating when they didn't have any spin to start?",
"Easy answers first. A galaxy and a solar system rotate for the same reason. Regions of concentrations of gas are pulled towards other regions. Centers within that gas pulls through the contrasting gas. That creates Von-Karman vortixes at all scales from galactic clusters down to moonlets around gas giants. There's something similar with the Coriolis force and cloud systems moving over islets. Von-Karmann are a general reaction of a static fluid interacting with something blocking the flow. The trailing fluid alternates in swirling direction. Its a periodic mass-flow excitation and stability problem. Essentially the fluid slinks around a barrier until too much of it is moving in one direction for the source of the fluid flow to maintain, then it goes the other way.",
"Now for the complex. Why do sinks form vortexes from static water? As water flows towards a drain it encounters minor disturbances in the flow at the bottom of the sink. Those instabilities form swirls which can reach the drain. At intermediate rates it is faster for water to drain with a swirl than with a static center flow so the vortex dominates at low Reynolds flow. Once the vortex begins the entire system takes angular momentum from the surroundings (the entire earth rotates a bit backward to let the water rotate the other way) and the system is now stable in a vortex flow."
] |
[
"/u/MrPennyWhistle",
" aka Destin, from Smarter Every Day, and Derek ,from Veritasium, did a pair of YouTube videos a couple of months ago with a really insightful experiment demonstrating drain swirls. They speak in depth about the origin of the spin, explain how the rotation of the earth contributes, and about the various myths surrounding the differences in spin between the Northern and Southern hemispheres. It's really entertaining but ever more informative.",
"The two videos can be found ",
"here",
" and ",
"here",
", but they are meant to be synced up and watched simultaneously which can be done ",
"here",
"."
] |
[
"Do all planets have seasons? If so, do they do anything?"
] |
[
false
] | null |
[
"Seasons are caused by the axial tilt of our planet. The axis around which the Earth rotates isn't perpendicular to the plane in which the Earth orbits around the Sun (the orbital plane). Because of this tilt, each hemisphere undergoes cycles in which it alternates between being \"turned away\" from the Sun and being \"turned towards\" the Sun. During the former, less sunlight hits that part of the planet and as such, temperatures are lower. We call this winter. Not only is the temperature affected, also the duration of sunlight during each day.",
"The effect of this is more pronounced the further you move away from the equator and towards the poles. In areas near the poles, at the height of summer, the Sun is always visible and there is a period of continuous daylight. Conversely, in winters, these areas have periods without any sunrises.",
"The greater the axial tilt, the more pronounced these effects are. Earth has an axial tilt of about 23 degrees right now (it oscillates slightly). This puts it near the middle of the pack in our Solar System. Mercury, Venus and Jupiter have a significantly smaller axial tilt. For Mercury it is only 0.03 degrees. Mars, Saturn and Neptune are in the same ballpark, but slightly higher than Earth (25-28 degrees). Uranus is an exceptional case with an axial tilt of 82 degrees. That means that for a considerable part of an Uranus year, large parts of the planet are either continuously exposed to the Sun or continuously in darkness. Except for the areas close to the equator, the regular day/night cycle is missing for large parts of the year, creating a large contrast between summer (Sun all the time) and winter (no sunlight at all for a long time)."
] |
[
"Some more details:",
"Mercury has such a slow rotation (which is coupled to its orbit) that the concept of a day and a year get somewhat mixed. I‘m not sure how meaningful the concept of seasons would be there.",
"Venus also has a slow rotation but the thick atmosphere covers it and makes temperature variations on the ground small.",
"For Mars the orbital eccentricity has an impact on seasons."
] |
[
"To address the question \"do they do anything\", yes. Mars has very strong seasonal changes, including changes in wind patterns and the formation and evaporation of carbon dioxide (dry ice) at the poles. As much as a quarter of the atmosphere freezes out and re-evaporates every year! Its dust storms also depend on season. Saturn's moon Titan appears to have big changes in methane/ethane rainfall that vary with season. Saturn has changes in atmospheric temperature and circulation, but not as extreme as Mars or Earth.",
"Less is known about the seasonal variations of Uranus and Neptune, though Uranus shows white hazes and clouds that vary with season. Jupiter and Venus have too little axial tilt to show much of a seasonal effect. Pluto probably has major seasonal changes, but these are mostly hypothetical so far."
] |
[
"What forms might our galaxy take after it merges with Andromeda?"
] |
[
false
] |
So, I just read that in a few billion years, the Andromeda galaxy and the Milky Way will . What will the resulting 'Supergalaxy' look like? I imagine the spiral arms we're so familiar with will be torn apart, but after looking at the video on that wikipedia link, there seems to be a big cluster of material that is wholly ejected. What will be the fate of these unfortunate stars?
|
[
"The two will first form an interacting pair, which will look quite irregular, like the ",
"antennae galaxy",
". In the long run (and with subsequent collisions) stellar movement should become sufficiently uniform to form an elliptical galaxy. This is also the process seen in the video you linked.",
"The stars that are ejected will just continue to exist with not much happening to them. If they're truly ejected, they'll just move on through intergalactic space, but will otherwise continue their normal stellar evolution.",
"Side note: Interaction between the galaxies will create density pertubations which should cause a lot of star formation as gas is compressed. This is related to the question of the spiral arms - According to density wave theory, the spiral arms are not static structures of stars and gas but regions of increased density. Gas clouds passing through these regions of higher density are compressed, triggering star formation. This creates, among others, some high-mass blue stars, which give the spiral arms their blue light. As the stars move out of the density wave, the massive blue stars burn out rather quickly, leading to the contrast between the spiral arms and the rest of the galactic disc. So since the spiral arms are not actually a bunch of stars and gas moving together as an arm but rather stars and gas are compressed as they move ",
" the arm, interacting galaxies should form similar structures (which can indeed be seen in images of merging galaxies)."
] |
[
"The stars and other (edit: gravitationally bound) stuff in the galaxy will move at lower angular speeds the further away they are from the galactic center of mass (for a simple model, see Kepler's third law). \nThe arms also spin, but at a fixed angular speed. Their angular speed of rotation does not have to change with radius because they are density pertubations and not fixed arrangemens of matter (which would have their rotation speeds governed by gravitation, see above). This solves the winding problem: \"If spiral galaxies spin and have arms, then why are the arms not wound tighter and tighter over time?\".",
"Therefore near the galactic center ",
"matter can overtake the density waves, while further away from the galaxy center of mass, the density wave can actually overtake stars",
".",
"Wikipedia also has ",
"an article",
" which covers the general idea of density wave theory."
] |
[
"Does this imply that the arms don't spin (pinwheel style), just the stars and matter of the galaxy do?"
] |
[
"If I went back to the Cretacious era to go fishing, what would I catch? How big would they be? What eon would be most interesting to fish in?"
] |
[
false
] | null |
[
"This is a fascinating response. So informative on something I never knew I wanted to know."
] |
[
"This is a fascinating response. So informative on something I never knew I wanted to know."
] |
[
"A number of reasons have led to the changes we see regarding armor in fishes. Armor plating was in vogue because the early seas were dominated by invertebrate predators with all manner of spikes, claws, and jaws to make short work of soft-bodied organisms. The majority of early organisms were pretty slow by design, so being armored was more realistic than being fast. However, many of the early armored fishes and invertebrate predators went extinct in the mass extinction near the end of the Devonian (~350 million years ago), which paved the way for the dominance of sharks and the ancestors modern (and less armored) bony fishes as they filled the void left by extinct species. ",
"The early modern fishes were also rather well-armored, though they were armored with recognizable scales, rather than the bony plates of older species. One thing about armor, however, is that it restricts movement. Once fish were a little better designed for speed, you see a reduction in the amount of body armor in favor of speed. ",
"Another major development was \"suction feeding\", by which a predator rapidly creates a vacuum to inhale food. Previously, fishes employed a method similar to what you'd see with a crocodile -- that is, simply snap down with lots of teeth and try to hold the prey long enough to swallow it. While sharp teeth seem more more dramatic than a vacuum, in practice there is a lot of room for prey to escape after capture, as the predator has to open its mouth to manipulate its prey. On the other hand, suction feeding allows the predator to swallow prey whole in an instant. Armor isn't much good if you've already been swallowed. It's better to just be too fast to catch. If my explanations weren't clear, check out these videos: ",
"suction feeding",
", ",
"old school",
"There are still many ancient (\"living fossil\"-ish) species alive today that have very heavy scales (though none of the ancient bony-plated fishes exist). Examples include ",
"gars",
", ",
" sp.",
", ",
"Australian lungfish",
", and ",
"sturgeon",
". Many of these ancient species have very specific strategies (e.g. ambush predator), live in slow-moving water, and/or many have adaptations that allow air-breathing, which gives a competitive advantage in oxygen-poor environments (e.g. a swamp) over species that cannot do this, regardless of how slow or fast they can swim. "
] |
[
"How dissimilar are particles and forces on a microscopic level?"
] |
[
false
] |
Obviously, they behave very differently on a macroscopic scale, but I and others would be curious to know what separates particles and forces at the base level. What, if anything, makes forces act as forces (i.e. causing acceleration), and particles as particles (volume, mass, etc.)? I understand that there is probably not any single well defined answer, but it would be interesting to hear the prevailing theories from different fields.
|
[
"You know Newton's law, right? ",
" is the way it's usually taught in schools; ",
" being the more useful way of writing it.",
"Newton's law says, in essence, that a particle will accelerate in a way that's inversely proportional to its natural resistance to acceleration — quantified as something called ",
" — and directly proportional to whatever is acting upon it, generically called \"force\" and represented as ",
".",
"\"What the heck is ",
"\" is the question that ",
" answers.",
"So your question essentially boils down to \"Please tell me everything.\"",
"Can you please narrow it down a bit?"
] |
[
"Microscopically, (point) particles do not have volume. They do have a notion of (rest) mass, and charges, &c. They are excitations of a certain field defined over all spacetime.",
"\"Forces\" are caused by interactions with \"force-carrier particles\" (a.k.a. \"gauge bosons\"). Gauge bosons are particles; they are also excitations of fields. They can also have mass, charge, &c. There are also particles that are not gauge bosons (colloquially called \"matter\").",
"The known species of gauge bosons are the photon, gluon, and the W and Z bosons. The known species of matter fields are the quarks and the leptons (electrons and her cohort, and neutrinos). The only difference between them is that while the former are vectors (spin-1), while the latter are Weyl spinors (spin-½).",
"(I've, of course, neglected things like scalars, gravitons, &c.)",
"TLDR: in QFT, both \"matter\" and \"forces\" are described in terms of excitations of fields."
] |
[
"Various intermolecular forces... electrostatics, charged particles, magnetism, gravity (not so much at small scales), van der Waal forces.",
"Different phenomena scale with different considerations... e.g. pressure depends on area, magnetism on distance. As you changed scales the relative contributions of different phenomena become more or less pronounced. The sum of all these forces at a particular scale determines how it behaves."
] |
[
"How do deep-sea organisms withstand crushing pressure?"
] |
[
false
] |
What cytological changes or other explanations are there for deep-sea life to withstand the high-pressure environment? I'm having a hard time getting past the thought of a submarine imploding upon itself when it gets to a sufficient depth, so what imparts resistance to this pressure? And does that make those types of things intolerant of a relatively low-pressure system up at the surface? If you took a fish normally living on the deep-sea floor, would its cellular architecture hold at sea level?
|
[
"Here is a really great article from Discover about just this question: ",
"Link to article",
"."
] |
[
"As long as the pressure \"within\" the organism is the same as the pressure outside, it would be fine I think. By within I mean all body cavities and cellular ones. So if you take humans very slowly (equillibrating them to the pressure as we proceed; not sure if its fully possible), we should theoretically be able to take them quite deep, until the pressure becomes extremely great and some mechanical considerations of our framework would not be optimal anymore(I'm guessing). But other than that as long as pressure within is equal to pressure outside it should all be fine. Thats why many deep-sea creatures that surface are exploded, because the pressure difference probably became too great at somepoint. In a previous discussion I was informed that if we slowly decrease pressure we can bring back any organism from the deep, but I don't have sources myself to support it..",
"I'm not telling it in a mean manner at all, I know that most people (including me till a few months ago) don't know of this, but there is a \"related\" link next to the \"comments\" link on any reddit post. Clicking it will reveal similar previous discussions; Doing so in this post reveals a similar question where we had some good discussions. Doesn't mean questions should not be asked again, but you might not get it answered at all at times and in those you can click that link and find if a previous discussion has taken place.",
"Link to previous discussion: ",
"http://www.reddit.com/r/askscience/comments/gj4fm/how_do_fish_and_other_marine_animals_survive_the/"
] |
[
"Perfect, explained it well, even though it takes a while to understand overly-simplified cell biology.",
"Yayanos, Somero, and others have discovered a few of the adaptations that permit deep-sea bacteria— and the cells of higher organisms— to thrive under high pressure. For one thing, deep-sea creatures make their cell membranes of squishier stuff. Cell membranes are layers of lipids (fats) penetrated by proteins that, among other functions, channel nutrients, wastes, and signaling molecules in and out of the cell. If the lipids are too rigid, the channels close up— and high pressure, like low temperature, makes any kind of fat more rigid. \"So deep-sea animals and bacteria tend to build their membranes with relatively fluid lipids,\" says Somero. \"Instead of butter they use something more akin to vegetable oil.\" That is, compared with surface-dwelling organisms, they use more unsaturated and less saturated fat. When such an organism is brought to the surface, thus taking the congealing pressure off its lipids, it may start to ooze a bit internally. The animals that don't die right away often suffer neurological impairment"
] |
[
"How can I comprehend the taste buds of another animal? For instance, if I were a vulture eating rank roadkill, or a deer eating fresh clover."
] |
[
false
] |
Dogs are the weirdest. Some will eat anything, while others spit out fruits and vegetables and look at you like you just handed them a stick. And why do some people like black licorice or cilantro?
|
[
"A taste bud is cells that compose or support chemoreceptors. Chemicals with specific shapes attach to specific receptors, and this is communicated to the brain to be processed as a taste type, and can be interpreted as desirable or not. Animals have genetic predispositions for specific tastes, and there is variation in this predisposition between species, as well as within species."
] |
[
"While the mechanics are the same, it is interesting to note, however, that 'heat' or 'spiciness' comes about via chemical interaction with pain receptors rather than the pathway involving taste buds. The same basic principles apply, though. The real difference is just that different receptors and nerve bundles are used. This is also why we can (often unfortunately!) experience spiciness with regions of our bodies that have no taste buds. One needs to be careful where they place their hands after slicing chilis! ;)"
] |
[
"I've heard this, and know that birds (mostly) aren't affected by capsaicin, which is why you can use chili powder on birdseed to keep squirrels out of it."
] |
[
"Is there an element/compound that is denser as a gas than it is as a solid?"
] |
[
false
] |
Title
|
[
"Generally, solids and liquids are about a thousand times more dense than gases at temperatures and pressures we're accustomed to. To increase the density of a gas, one would decrease the temperature and increase the pressure. At too low of a temperature/high of a pressure, the gas would condense into a liquid, the exact T/P combination depending on the substance's ",
"phase diagram",
".",
"To combat that, one could keep a gas's temperature above its ",
", which is the point at which it's too hot to condense into a liquid, no matter how high the pressure. Instead, above a substance's critical temperature and ",
", the gas transitions into a ",
"supercritical fluid",
". This is its own state of matter, neither really a liquid or a gas, but with some properties of each. ",
"Supercritical fluids are used in the chemical industry in a few interesting ways, notably CO2 as a solvent for extractions (Fun fact, caffiene is extracted from coffee this way to make decaf without heating the bean or using organic solvents). Small changes in temperature and pressure near the critical point can have a large impact on the fluid's solvent properties, so conditions can be tailored to a particular process's needs. They're really nifty. ",
"Under astronomical pressures, a supercritical fluid could have a higher density than when it's a solid. Solid CO2 (dry ice) has a density of around 1.5 g/mL at 1 atm and near its sublimation point. Supercritical CO2 fluid would have a density higher than that at around 8000 atm. For perspective, pressure in the deepest part of the ocean (Challenger Deep, Mariana Trench) is about 1000 atm. 8000 atm is getting close to the limits of extreme-pressure chemical reactors, but diamond anvil cells can reach well into the millions of atm, so that pressure is exotic but not unattainable in a lab.",
"You could accomplish something similar with a variety of substances, but these aren't strictly gasses anymore. I can't say that's the only way to ever get a gas more dense than its solid, but any other options would be some really special cases. I'm probably interested in the other answers as much as you are!"
] |
[
"Hey thanks for that! That was very informative, and luckily I'm in a chemistry class on equilibria right now, so i understood it! What pressure do the anvil cells reach to? Is there a maximum pressure we could obtain with our knowledge of the elements?"
] |
[
"I don't have any professional experience with diamond anvil cells, but from some quick googling it looks like the state of the art is somewhere >700 GPa (about 7 million atm). Here's a ",
"news article",
" from 2012 summarizing some work in that direction. Apparently the limiting factor at those pressures is the diamond itself, and we don't know of anything harder. ",
"Diamond anvils are really fascinating. Lots of strange materials and phases of matter emerge at extreme pressures. Since diamonds are transparent, you can run all sorts of optical, spectroscopic, crystallographic experiments in them. Even the methods for measuring pressure inside are special. The ",
"Wikipedia page",
" is pretty thorough and is a good starting point. ",
"Also, apparently E. coli bacteria ",
"can survive",
" in at some of the pressures produced in anvil cells. Wow. "
] |
[
"Why is radioactive decay exponential?"
] |
[
false
] |
Why is radioactive decay exponential? Is there an asymptotic amount left after a long time that makes it impossible for something to completely decay? Is the decay uniformly (or randomly) distributed throughout a sample?
|
[
"Exponential decay comes from the following fact:",
"The rate of decay is directly proportional to how many undecayed nuclei there are at that moment.",
"This describes a differential equation whose solution is an exponential function.",
"Now, why is that fact true? Ultimately, it comes down to two facts about individual radioactive nuclei:",
"- Their decay is not affected by surrounding nuclei (in other words, decays are independent events), and",
"- The decay of any individual nucleus is a random event whose probability is not dependent on time.",
"These two facts combined mean that decay rate is proportional to number of nuclei."
] |
[
"To add some basic math. Lets imagine there are 1m nuclei. If each has a 50% chance of decay per year, you would decay somewhere around 500k nuclei in year one. Well, next year you start with 500k, so you'd decay 250k. Next year 125k.",
"500k > 250k > 125k > 62.5k . Exponential and assymptotic.",
"Obviously the above numbers are based on the half-life... that is to say the duration for a given amount to half way decay. Each element has its own half-life."
] |
[
"Each isotope. E.g. different uranium isotopes have vastly different half life. (There are also exited states of nuclei, thus even the same isotopes may have different half life.)"
] |
[
"Have we been able to successfully create matter from energy?"
] |
[
false
] |
Since we theorize that that's the basis of the big bang, have we been able to prove it experimentally, albeit in a much more controlled environment on a much smaller scale?
|
[
"Yes, that's what happens all the time at CERN, Fermilab, etc... : particles are accelerated so that they gain an enormous amount of kinetic energy. This kinetic energy is then converted into new particles during collisions."
] |
[
"If you mean giving a particle energy as in accelerating it to a high velocity (giving it kinetic energy) no. That would violate the conservation of energy because from the rest frame of the particle, it is not moving, and therefore has no kinetic energy in its own perspective, and according to relativity, physics has to work the same in all reference frames. In other words no single body can decay or produce products with more mass than it began with, and only collisions can actually convert mass into energy. Also, a single photon that has high energy (in one reference frame) cannot decay into a particle antiparticle pair by itself in free space, because it is possible for the observer to find a reference frame where the photon is so red-shifted that there is not enough energy for the photon to conserve energy in the interaction. Another way to think about it is that it is possible for the observer to find the reference frame where the particle antiparticle pair are moving in opposite directions at equal velocity, meaning that there is 0 total momentum in the system. Since the incoming photon cannot have 0 momentum (the momentum is directly related to the energy in massless particles), momentum would not be conserved. The only way pair production could occur is for the photon to be in the presence of a strong electric field (such as that of the nucleus) so that there is a second body (the nucleus) to absorb some energy and fulfill the conservation laws of energy and momentum.",
"Also, can pure energy exist separate from any attachment to matter?",
"Neutrinos are pretty close to that, meaning they only weakly interact with matter. 99% of energy carried away from supernovae are from neutrinos, and that energy might as well be lost from the universe because a neutrino can go through a light year of lead without being stopped. The only way that energy can be absorbed is probably through a black hole."
] |
[
"I think in TUVegeto137's example, the collision must occur for the new particle to be created. I'm curious if new matter could be created simply by giving a particle more energy with nothing else (like a collision). I think this is what you are wondering as well.",
"Also, can pure energy exist separate from any attachment to matter?"
] |
[
"Are there hyperconic sections?"
] |
[
false
] |
[deleted]
|
[
"TL; DR: Yes, there are. The easiest way to get to this is to look at the algebraic formulations of the geometric objects.",
"Let's do this!",
"For a start, let's consider conic sections (Non-Hyper). ",
"The points in a cone are characterized by the equation ",
"x",
" + y",
" = z",
" , (I)",
"i.e. all points (x,y,z) which fulfill this equation are part of the surface of the cone.",
"Let's intersect this cone with a plane, and for starters let's take the x-y-plane. Points on the x-y-plane are characterized by ",
"z=0, (II)",
"so points which lie on the intersection need to fulfill both (I) and (II). Which are those? Plugging (II) into (I) yields x",
" + y",
" = 0, and as the squares are always nonnegative, this is only fulfilled for the point (0,0,0).",
"Now let's take a less boring plane parallel to the x-y-plane. It is characterized by ",
"z=c (III)",
"for some fixed c (the height of the plane, if you will). Again, points on the intersection need to fulfill both equations (I) and (III) and we get x",
" + y",
" = c",
" or sqrt(x",
" + y",
" ) = c, the equation which describes a circle.",
"Last x-y-z example until we get to the hyper stuff: A plane which is parallel to the x-z-plane, but not the x-z-plane. This is characterized by ",
"y = c (IV)",
"for some fixed y. Plugging (IV) into (I) yields x",
" + c",
" = z",
" , or equivalently (x/c)",
" - (z/c)",
" = 1, which is the equation for a hyperbola.",
"Now for the real hyper stuff. The equation which describes a hypercone is ",
"x",
" + y",
" + z",
" = w",
" (I').",
"The x-y-z-Hyperplane is characterized by ",
"w = 0 (II')",
"and the intersection of our hypercone with it is described by x",
" + y",
" + z",
" = 0, i.e. the point (0,0,0,0). ",
"A parallel (i.e. also perpendicular to the w-axis) hyperplane would by characterized by ",
"w = c (III')",
"for some c, and the intersection is characterized by",
"x",
" + y",
" + z",
" = c",
" , ",
"indeed a sphere with radius c.",
"So let's take a plane perpendicular to the z-axis:",
"z = c (IV')",
"for some fixed c.",
"Plug (IV') into (I') and get ",
"(x/c)",
" + (y/c)",
" - (w/c)",
" = 1,",
"which is actually the equation of a hyperboloid!",
"You do get degenerate cases if you take planes which intersect the origin, as see with the degenerate circle/sphere, i.e. the origin itself."
] |
[
"Since slicing a dimension 4 object with a dimension 2 object creates a dimension 3 object (at least as I understand), would slicing the hypercone (4D) with a space (3D) create 2D objects which would be our normal conic sections, or would they be different?"
] |
[
"It depends and is not easy to answer.",
"Let me ask the same question for the conic sections:",
"If we take for granted that the cone is a 3d object and the planes we intersect it with are 2d objects, which are the results? A point, A circle, hyperbolas, parabolas. Which 'dimension' do these objects have?",
"Speaking of dimensions is always a bit tricky when you're not dealing with things which are not linear (sub)spaces, and this is almost everything exept lines, planes and hyperplanes which intersect the origin.",
"There's a part of mathematics which deals with these kind of questions, it's called differential geometry. One of the questions which arises there is: How do we describe and measure complicated objects, and the answer is: With maps."
] |
[
"Have non-human Great apes ever been seen communicating with each other in sign language?"
] |
[
false
] |
There's a great scene in Rise of the Planet of the Apes where an old circus orangutan starts signing to the main chimp who signs back and I'm just wondering if it has ever been seen in real life.
|
[
"Most great apes don't get beyond using very, ",
" simple vocabularies. Most of the exceptions are listed on ",
"Wikipedia",
". The wikipedia article is actually quite thorough (make sure you read the references for more info)."
] |
[
"We have seen apes spontaneously use meaningful gestures with each other. ",
"Here's one example.",
"Instances of apes using fully grammatical sentences in ASL or any other sign language are, to say the least, extremely rare. And as far as I know, there's never been any observation of apes signing full sentences to each other - though I'm sure they can use single signs with each other, given that they can use iconic gestures. "
] |
[
"Communicating in sign language in the wild, no. But, they do communicate in other ways and have rich emotional languages. ",
"http://en.wikipedia.org/wiki/Emotion_in_animals#Primates",
"Chimps have even been caught in the wild lying. A baby chimp wants another chimps food will \"cry out\" with a sound that alerts its mother that it is being attacked. The mother comes running to chase the other chimp away and the baby gets the food! :)"
] |
[
"How exactly does an induced-fit model work?"
] |
[
false
] |
How do enzymes know when to change the size/structure of their active site when different substrates are presented? Also, how do these enzymes organize their substrates so efficiency is maximized? (so do they do all of substrate A at once then substrate B, or do they alternate, etc)
|
[
"Biomolecules are not rigid. If you look at NMR determined solution structures you find multiple, similar conformations. Also, they do not \"know\" because they do not \"think\" or \"feel\" or \"want.\" The only determinant is what is stable.",
"In terms of an enzyme there is a catalytic pocket that a substrate fits into. The substrate fits because not only is the pocket spatially formed to fit, it has hydro-philic and phobic regions that correspond to the substrate. ",
"A pocket may be slightly bigger to allow for ease of the substrate to fall in ( citation needed ), however once the substrate is in like forces will attract. This now semi-flexible protein's pocket may conform more tightly to the substrate because of these forces. "
] |
[
"Fluoxetine is correct",
"Molecular dynamics allows for computer models of proteins and their binding to substrates. I've included links to a couple videos generated by molecular dynamic models. Note how much vibration exists in the molecules.",
"An Introduction to Molecular Dynamics",
"A basic introduction to drugs, drug targets, and molecular interactions.",
"Molecular dynamics of carbohydrate binding to a designed protein",
"Molecular dynamics of a protein"
] |
[
"Exactly, I did not outright state that, but as I stated enzymes catalyze the reaction. A catalyst is a general term for anything that increases the rate of the reaction. I discussed how the rate is increased when looking at enzyme substrate interactions. There is much more to this, but the basic concept is that the rate is increased due to a stabilization of the transition state. An enzymes rate is constant, assuming sufficient substrate availability and no inhibitors. "
] |
[
"Can exposure to an incredibly high dose of radiation lead to instant death?"
] |
[
false
] |
If a person, standing in plain clothes is exposed to an intense radiation source (200+ roentgens / hour) , is it possible for them to die instantaneously?
|
[
"Yes, high enough acute doses can prevent neurons from firing correctly and lead to instant death. If you were to pull out a fuel assembly from a nuclear power plant and place it on the wall and run at it from 50 feet away. You will die before touching it."
] |
[
"This has actually happened. Bugorski took 300,000 rads to the head from a beamline in 1978 and lived. ",
"https://en.wikipedia.org/wiki/Anatoli_Bugorski",
"http://www.wired.com/wired/archive/5.12/science.html"
] |
[
"For any sort of magnetic field that we can create on earth, no, with patients with pacemakers an exception due to those device's sensitivity. The magnetic fields in MRI machines are 1-3 Tesla. This is similar to the magnetic field inside a loud speaker coil. People have levitated living organisms in strong magnetic fields - search for \"frog levitation\". These magnetic fields are probably on the order of 10 Tesla. ",
"For reference, the earth's magnetic field is on the order of 30-50 microTesla, and the 60Hz magnetic field from standing 50 feet away from a high-voltage power line is around 10 nanoTesla."
] |
[
"Is there a closed-form equation for this type of curve generated by connecting points on a graph?"
] |
[
false
] |
This shows the curve which is generated by connecting the points (0, 0) to (10, 0), (0, 1) to (9, 0), and so on. Of course, the endpoints don't have to be (10, 0) and (0, 10), they can be (X, 0) and (0, X). My question is: as I increase the number of subdivisions, e.g. connecting (0, 0.1) to (9.9, 0), until the spacing between lines becomes an infinitesimal quantity, is there a closed-form equation for the resulting curve that bounds all the lines within, assuming I use the endpoints (10, 0) and (0, 10)? My guess, just from looking at the rough shape of the curve, is that it is the arc of a quarter-circle with the center at (10, 10). Or is it not as simple as that?
|
[
"The curve turns out to be neither a circle nor a parabola, but a curve of the form",
"√(x) + √(y) = √(K)",
"where ",
" is some constant (K = 10 in your example). Okay, so how do you prove that? Well...",
"We first consider the collection of all line segments, one endpoint of which is (0, a) and the other endpoint of which is (K-a, 0). The value of ",
" is constant throughout. For a given ",
", that line segment satisfies the equation",
"y = L(a,x) = a - ax/(K-a)",
"Our collection of line segments is then the graphs of all of these equations for 0 < x < K and 0 < a < K. The desired curve is then said to be the ",
" of all of these line segments. Let y = f(x) denote this curve. Then for a fixed value of ",
", the value of ",
"(",
") should be the maximum value of L(a,x), taken over all possible values of ",
". (Remember that ",
" describes the line segments and ",
" is the parameter that tells us ",
" line segment we are considering.) This is now reduced to a standard one-variable calculus problem.",
"So we compute dL/da and set it equal to 0, giving the equation",
"1 - Kx/(K-a)",
" = 0",
"This equation has a unique solution for 0 < a < K: ",
" = ",
" - √(",
"). The maximum value is obtained by substituting this value of ",
" back into ",
", which then gives us our value of ",
"(",
"). After some cancellations, we get",
"y = (√(K) - √(x))",
"which, since ",
" is positive, can be written as what I wrote at the very start, making the required symmetry in ",
" and ",
" immediately evident:",
"√(x) + √(y) = √(K)",
" Actually it is a parabola, as ",
"/u/lucasvb",
" points out. That's my mistake. If you know about conic sections, the most straightforward way to verify the curve is a parabola is to square both sides of the equation, rearrange, and eliminate the last square root. You eventually get something like ",
"(y - x)",
" + linear stuff = 0",
"This equation is in the form of a conic, and its discriminant is immediately seen to be 0, which is invariant to isometries. So the original curve is a parabola. ",
"Once you know it's a parabola it's a simple matter of rotating it by 45 degrees to get the equation in the more familiar form of y = ax",
"+b. "
] |
[
"To add to ",
"/u/Midtek",
"'s excellent answer for this specific example, the ",
" is a actually ",
"a piece of a parabola",
". For three points A B and C, with B in the middle, you can define the curve parametrically as:",
"P(t) = A (1-t)",
" + 2 (1-t) t B + C t",
" for 0 ≤ t ≤ 1",
"We'd call it a ",
"quadratic Bézier curve",
", and this is used a lot in computer graphics to approximate general shapes. On that article, lower on the page, ",
"you can see some cool animations",
" explaining how these curves would be drawn."
] |
[
"I see you already have real answers, but here's a quick visualization I made, along the lines of what ",
"/u/camkatastrophe",
" posted, but with a bit simpler presentation. you can see that the curve is pretty close at the top, bottom, left, and right edges, but gets a bit over-round in between:",
"http://imgur.com/FVevE9j"
] |
[
"Blood type translations from"
] |
[
false
] |
Hi Reddit Ask Science, I hope this is the right place. I am an immigrant from Russia and I looked in my old passport there was a blood type: "ab(IV) rhes poz" What is it equivilant in the western blood type systems if I want to donate blood? What are the different blood type systems for and what sets them apart?
|
[
"That sounds like it would map to 'AB' 'rhesus positive' but I am not an expert and might be totally wrong.",
"If you did donate blood they will take their own tests, most likely."
] |
[
"I tried but the other systems are in other languages, making it hard to impossible to understand in google translate. It would be cool if a scientist explain it."
] |
[
"You're correct."
] |
[
"Scientists are excited to find water on Mars because it can be used to create hydrogen and oxygen (rocket fuel and breathable air). But splitting water requires more energy than you get by burning the HHO. How does science foresee using the water effectively to fuel/run/support a base on Mars?"
] |
[
false
] |
[deleted]
|
[
"Would probably be most efficient to build one on mars from scrap."
] |
[
"Would probably be most efficient to build one on mars from scrap."
] |
[
"Hydrogen and oxygen will be used for propellants and possibly portable turbines (like high-altitude drones).",
"The larger stations would be powered by solar (low power output because of less solar radiation than on Earth, but still usable) and nuclear (for obvious reasons, although reactors would be big and heavy and RTGs would contaminate the landscape, which might not be much of a problem, but it would depend on how thick the spacesuits were, if humans were to be resident.)",
"The exciting thing about water is that you could make a bunch of propellant and potentially get back into orbit around Mars. Then you could hop back on the interplanetary craft (likely powered by nuclear/ion drive) or catch the station/ship in permanent transfer orbit."
] |
[
"Shouldn't audio equalizers reflect/invert the differences in perceived loudness along the frequency spectrum?"
] |
[
false
] |
has a frequency x sound pressure x perceived loudness contour curve, allegedly sourced from ISO 226. I figure the curve shape even shifts for different levels of perceived loudness (long bass waves reach very far, as anyone who's been a block away from a dance party knows), but computers and dedicated circuits should be able to adjust for this smartly as volume is changed, etc. (The problem, of course, would be telling people to adjust volume in their software and not in the system, or in the amp/external eq and not the sound source and so on. Psychologically, this is very hard to guarantee.)
|
[
"Acoustical engineer here. There is no reason for a signal processor to apply this adjustment to the spectrum because your ear will naturally do this.",
"The graph in that link is known as an \"equal loudness\" curve. The loudness is expressed in \"phons\" and is represented as a function of both frequency and sound pressure. (By the way, the labeling on the graph is wrong. It should say sound pressure level on the left.) So any point on that line will sound equally loud to any other point on the line.",
"So 50 dB-SPL at 1kHz will sound like 50 phons; 60 dB-SPL at 100 Hz would sound like 50 phons; and so on.",
"So if you used an equalizer to match that curve, your ear would then apply the same adjustment on top of that and change the spectrum further. This is unnecessary, so just use the equalizer to make the music sound good. Let your ear take care of the loudness adjustments.",
"It should also be noted that equal loudness contours are also a function of intensity. So the more you increase the intensity, the flatter that curve would look. So there is less difference in the perceived loudness of two tones of different frequency at higher sound pressure levels."
] |
[
"Acoustical engineer here. There is no reason for a signal processor to apply this adjustment to the spectrum because your ear will naturally do this.",
"Answered! Thanks :)"
] |
[
"It seems what you would require is a system that would also monitor your proximity to the speakers in order to properly attenuate or compensate. This poses not only the problem of being inaccurate, but also of compromising the sound quality for multiple listeners in order to achieve higher-fidelity for one. ",
"Not to mention that musical tastes and ear shape/sensitivity play a big factor. I, myself, like to attenuate the major mid-range bands between 1Khz-4Khz. In this way, I enjoy loud music in my house that can still be spoken over and easily heard with a normal voice."
] |
[
"Why are the sidereal year and the tropic year related?"
] |
[
false
] |
Why is the tropical year (tilt of the earth back to same sun position) related to the sidereal year (orbit around the sun to the same star position/one time around the sun) at all? Is there a mathematical relationship? Could we have something like 4 or 8 tropical years for every sidereal year?
|
[
"The difference in the first place is due to ",
"axial precession",
", the rotation of Earth's axis. If this didn't happen, then sidereal and tropical year would be exactly the same. The reason why they are almost the same is that the precession is very slow. It takes tens of thousands of years for the axis to do one full circle.",
"See ",
"this interactive demonstration",
". Let's first pretend that axial precession doesn't exist. Pay attention to which direction the axis of rotation is pointing as you go through the year by dragging the red arrow through the calendar. You should notice how it takes one full rotation around the Sun for the axis to return to pointing to the same direction. That's why tropical and sidereal year are the same without axial precession.",
"It's not demonstrated on that page but imagine the axis rotating very little during the year so that Earth needs to orbit a little bit more for the axis to return to the same position again."
] |
[
"Assuming we are always referring to the season in the Northern-Hemisphere.",
"Look at ",
"this diagram",
" depicting the seasons. Note that the angle of 23.5° effectively doesn't change. If it actually didn't change there would be no difference between sidereal and tropic year. It fluctuates a tiny bit resulting in the tiny difference.",
"In your diagram where you labeled summer on the right hand side, the north-pole is pointed away from the sun and it would be winter. For it to actually be summer the pole would need to be pointing towards the Sun. Therefore for the situation you describe to occur the Earth would need to violently totter 47° every six months - where currently it totters a fraction of a degree.",
"I'm not sure if these forces could exist in a planet without tearing it apart and would need to be caused by some huge impact."
] |
[
"A tropical year is 365.2422 mean solar days, and a sidereal yar is 365.256 mean solar days, or about 20 minutes longer than a tropical year. This never changes.",
"A tropical year is measured by the interval of time between one vernal (spring) equinox to the next. Equinoxes occur when the ecliptic intersects the celestial equator. What this means is that Earth's rotation axis (or its line of tilt) is perpendicular to an imaginary line joining the Earth to the Sun. We experience the equinox as the day when \"day\" and \"night\" (hours of daylight vs. hours of darkness) are the same length. These occur twice a year; once in the spring, as the night gets shorter and the day gets longer, and once in the fall when the opposite occurs. Because the Earth's rotation very slowly precesses (think of a spinning top that changes the direction it tilts in as it spins) the vernal equinox actually arrives a little bit quicker than it should. Basically, the Earth tilts itself closer to the position it's trying to reach.",
"A sidereal year, however, is the time required for the Earth to complete exactly one orbit around the Sun relative to the stars. Imagine a star very, very far away from us - millions of lightyears away. If we draw an imaginary line from the Sun to the Earth to the star, then measure the time it takes for the Earth to come back to that same position, we would have a sidereal year.",
"The reason these measurements are different is because of what we're measuring relative to. That is, a tropical year is measured relative to what we experience on the Earth, which is subjective because the Earth tilts verrrry slightly differently each year. This has nothing to do with Earth's position in space, however, so the sidereal year remains the same. ",
"Source: I'm staring at my Astronomy textbook right now. "
] |
[
"Do transcription factors bind RNA?"
] |
[
false
] |
Since it is known that genes can be regulated by intragenic regulatory elements, and do so in a sequence-specific manner, is it possible for some classes of transcription factors to recognize these sequences in the corresponding transcribed RNA? If so, might it be possible to disrupt TF binding in a site-specific manner by using an engineered RNA 'sponge'?
|
[
"In answer to the first part of your question - ",
"\nThere are actually several known RNAs which act in living cells in the way in which you describe, acting as \"decoys\" for transcription factors, thus preventing their binding to the DNA (review article: ",
"http://www.nature.com/nature/journal/v482/n7385/fig_tab/nature10887_F2.html",
"). Most of the RNAs that function in this manner are termed long non-coding RNAs or lncRNAs (meaning that they are not translated into proteins). In addition other functional interactions between RNA and proteins have been described such as binding to epigenetic modifiers such as Polycomb-group proteins (source: ",
"http://www.ncbi.nlm.nih.gov/pubmed/17604720",
") and inhibiting transcription factor activity through sequestration in the cytoplasm (source: ",
"http://www.ncbi.nlm.nih.gov/pubmed/21709260",
").",
"In answer to your second question - it depends. It is theoretically possible to design an RNA-sponge to disrupt transcription factor binding, but there are several problems to consider. Many of these are equally applicable to the design of any intracellular agent- including how to get it into the cell (transduction of a DNA sequence using lentivirus is possible), how to produce it efficiently within the cell (appropriate promoters etc.), localization within the cell (if it goes into the cytoplasm when the TFs are in the nucleus then it will not be very effective) and half life (RNA generally has a shorter half life than protein and DNA within a cell). The prediction of RNA folding and activity under cellular conditions would also be a challenge - and would require experimentation in vitro in order to determine whether binding to the transcription factor would occur and whether the affinity was high enough to have a biological effect (e.g. as a competitive inhibitor).",
"Source - I work with lncRNAs and other noncoding RNAs."
] |
[
"Since RNA is transcribed as a single strand, it generates a complex secondary structure like a protein strand - this would disrupt the traditional motifs used by transcription factors to recognize DNA such as basic loop helix binding domain.\nThere are hundreds of ways to engineer mimics or other inhibitory elements to prevent transcription. One of these ways is through Lnc-RNA, which does inhibit the transcription factors from binding or from initiating transcription."
] |
[
"There are some CRISPR-Cas based systems that can bind RNA. Specifically type III systems. There is less known about them, but some researchers have successfully targeted and bound RNA. The one specific paper included below uses the protein csy4 among other regulatory elements to create programmable gene circuits.",
"Sources:\n",
"http://www.sciencedirect.com/science/article/pii/S1097276514003554"
] |
[
"If the universe is 13.7 billion years old, how come the observable universes edge is 46-47 billion light years away? Should it not be 13.7 billion light years away?"
] |
[
false
] | null |
[
"Because the universe is expanding \"faster than the speed of light can cover spacetime\". Imagine the earth was the universe and it is expanding at a high rate (getting bigger in scale). If you were living in New York and China was some light years away, the earth is now expanding faster and faster (growing in size) at a rate that increases distance between NY and China so fast that even if you were travelling at light speed, you will never be able to reach China. So effectively, it's expanding \"faster\" than the speed of light can keep up, even though technically the countries are not travelling at any speed at all.",
"EDIT: So to put everything together, light now has to travel 47 billion years to reach us even though it's only 13.7 billion years old. because now we are so far apart."
] |
[
"It doesn't work that way, because it's not expanding from a central point, so the light doesn't have to travel from \"the place where the big bang happened\" towards \"the boundaries\". It's expanding from everywhere, because the big bang itself was, if you want to put it this way, everywhere (space was infinitely small at that point).",
"In other words, don't think of it like a puddle that is spreading from a central point, but more like a plastic surface that is stretching equally from everywhere."
] |
[
"From what I understand, something we see as 40 billion light years away now wasn't 40 billion light years away when the light was emitted. It was closer, but the space between us and it has gotten bigger.",
"A poor analogy would be that if a person moving away from you yelled at you, by the time you heard their voice they would be farther than when they yelled."
] |
[
"Could a nuclear explosion create artificial diamonds?"
] |
[
false
] | null |
[
"Apparently detonation nanodiamonds are a thing. ",
"wiki",
"These are from conventional explosions. A nuclear weapons does use conventional high explosives in the reaction. You would need an abundance of carbon. Modern weapons would only have the carbon in the high explosives. Everything else is not a carbon compound. "
] |
[
"I'm extremely skeptical that any diamonds could have been formed at ground zero at Hiroshima. The overpressure (pressure above normal atmosphere) from a 20 kt airburst at a similar altitude to the Hiroshima strike ",
"is around 16 psi",
", which isn't exactly diamond-creation range. The Hiroshima bomb was quite a bit smaller than that, depending on who you believe.",
"The Hiroshima fireball never reached the ground."
] |
[
"an abundance of carbon",
"Hiroshima was mostly wood. If you looked at the soil layer by layer you'd probably find one that would be both rich in nanodiamonds and helpfully tagged with radioisotopes so you can be sure you have the right time. It was an airburst but it was still pretty intense in the center.",
"Diamonds have no half-life either, so astute archaeologists in the far far future might look at this patch of soil and go \"huh.\""
] |
[
"Are stars capable of using fusion to form all elements?"
] |
[
false
] | null |
[
"Normal stellar fusion can only get you up to nuclides around the stable isotopes of iron. To go beyond that, other processes are needed. For example, the s-process and r-process."
] |
[
"Could you explain a little more what the s-process and r-process are?"
] |
[
"The Wiki articles for ",
"s-process",
" and ",
"r-process",
" are a good start."
] |
[
"How do ships in space measure their velocity? Do they have to calculate it based on their thrust and weight (which is constantly changing as it burns fuel)."
] |
[
false
] | null |
[
"usually isn't terribly accurate",
"For spaceships and ICBM's they ",
" terribly accurate (and expensive). A professor told me about an IMU left on while sitting on a table for a day or two. It was accurate enough that you could clearly see the slight movement of the thing as the building expanded and contracted as the sun warmed and the night cooled it."
] |
[
"One method is to use inertial sensors to measure acceleration and angular velocity. By integrating those you can get some idea of where you are, but it usually isn't terribly accurate. Edit: Apparently this method is a lot more accurate than I was led to believe. ",
"Another method is to look for specific start and use trigonometry to figure out where you are in relation. ",
"Finally, you can use equipment on earth to track a spacecraft. I don't know what accuracy and distance you get out of this method. "
] |
[
"The NASA guy was right- velocities are always measured relative to something. It's really the only way they make sense. Here on Earth we have a very natural coordinate system. We assume the Earth is not moving, and we measure how quickly we pass over the surface of the Earth. But, we are still measuring our velocity relative to something, in this case the Earth. However, in your car you could decided to measure your velocity relative to the Sun, and in that case you would have to take into account the Earth's rotation and its orbit. But you car does not have an inherent velocity, it has a velocity as measured in relation to something else. "
] |
[
"Why is ethanol drinkable but methanol, 2-propanol, etc. poisonous?"
] |
[
false
] |
From an organic chemistry perspectice, what significant difference does one extra carbon make? I'm an organic chemistry student and I've yet found the answer.
|
[
"As others have already said, it just so happens that some alcohols have toxic breakdown products and others don't. Since you're an organic chem student, some details may be interesting:",
"Methanol and 2-propanol are processed by the same enzymes that ethanol is. First Alcohol Dehydrogenase oxidizes the -OH group to a carbonyl group producing the respective aldehyde. ",
"Methanol becomes formaldehyde - a preservative, toxin and carcinogen.",
"Ethanol becomes acetaldehyde - mildly toxic, probable carcinogen.",
"2-propanol becomes acetone - you use this to clean your glassware because it's an excellent organic solvent but not very toxic at concentrations relevant to your question.",
"The next step is further oxidation of the aldehyde group to a carboxylic acid group by the enzyme Aldehyde Dehydrogenase. ",
"Formaldehyde becomes formic acid/ formate - acutely toxic. ",
"Acetaldehyde becomes acetic acid - harmless.",
"Acetone is a bit different. Our bodies have metabolic pathways that can recycle it into energy sources (it's part of the ketone body pathways)."
] |
[
"The reason that methanol and other alcohols are considered poisons is due to the byproducts that are created when your body breaks them down.",
"Certain types of antifreeze are extremely toxic because of the presence of ethylene glycol. ",
"Here",
" is a good source for what happens when your body breaks it down.",
"When ethanol is broken down, it becomes acetic acid (vinegar) and doesn't destroy organs in the process.",
"I'm not saying that ethanol isn't toxic, but anything is a poison if you ingest enough of it. You can die if you drink excessive amount of water."
] |
[
"Interestingly enough, the treatment for methanol poisoning is intravenous ethanol, as it uses the same enzyme (alcohol dehydrogenase) that converts methanol into its toxic products. "
] |
[
"How do rashes target specific parts of the body?"
] |
[
false
] |
I came across which results in rashes on the palms of the hands and feet. “It’s one of the few rashes where you’ll have bumps or blisters on the palms and soles of the feet,” Dr. Derickson says. "Usually rashes on the whole body spare those parts, so that's one of the give-aways." I've always thought of rashes as being the result of a physical irritant, so you get the rash wherever the thing that causes it touches you, or it's in your bloodstream and you get breakouts pretty much all over. But this particular virus causes rashes in specific areas. How does it do that? And the claim I quote above suggests that most rashes don't happen on the palms of soles and feet, so why is that? How are these rashes able to target specific areas of the skin?
|
[
"I believe the answer is \"we don't know\" (though I'd love to hear what the answer is if we do know. Any dermatology buffs around?)",
"Rashes from different disease processes can take stereotyped albeit different forms, I'm not sure why. H, F &M disease is an interesting example. There are many others which have stereotyped rashes: the heliotrope rash of dermatomyositis, the salmon-pink maculopapular rash of adult-onset Still's disease, the classic flexor rash of eczema vs the extensor rash of psoriasis, the target lesions in the rash of Lyme's disease or even the dreaded non-blanching purpuric rash of meningococcal septicaemia. There must be hundreds of examples.",
"An interesting example where the answer is known is the herpetic rash from viral herpes. Typically, the rash appears in the ",
"dermatome",
") corresponding to the nerve root which the herpes virus is infecting. ",
"rashes as being the result of a physical irritant",
"Rashes can and often are the result of physical irritant. Viral rashes, however, are not necessarily due to physical irritation of the local area, and often appear in a general distribution. For example, children will often get a generic rash from just being unwell with a viral cough, cold etc."
] |
[
"Hand Foot and Mouth Disease can be caused by a couple of viruses, including a coxsackie virus and enterovirus 71 (EV71). While the coxsackie virus causes more Hand Foot and Mouth Disease cases, I found ",
"this",
" paper that talks about EV71 and its tropism. Tropism is the type of cells that a virus can infect based on the surface proteins of the virus and the surface receptors on the cells that it can bind to. This is generally quite specific. According to the paper, in the case of EV71, a receptor called human SCARB2 (hSCARB2) is indicated as one of the main receptors that the virus uses to enter the cell. However, the paper goes on to say that this receptor is quite broadly expressed, and so is therefore not the sole reason we see the limited disease pattern that we see. The paper goes on to suggest that other host factors are at play in limiting the virus to only the places that we see, such as Internal Ribosomal Entry Site Transactivating Factors (ITAFs), the host's interferon response, and possibly miRNAs.",
"",
"So to answer your question more briefly, the disease that we are able to see is an interplay between viral tissue tropism and the host immune system/other host factors."
] |
[
"Rashes are caused by irritation/damage to the skin, often by direct contact (as you mention above) such as touching acid, but sometimes as the result of processes that affect the whole body such as a virus. ",
"Coxsackievirus is the virus behind Hand Fooot and Mouth disease, and to echo Wdenners, we really don’t know why it preferentially travels through the blood stream to attack those three body locations. Viruses can target specific cell type and specific proteins, so presumably it likes something about what hands, feet, and the mouth are doing. However, we don’t know what that is. As for the different presentations in different people... that’s going to likely be do to genetic diversity producing slightly different cellular targets for the virus, but that’s basically all we can say about that.",
"A very specialized biochemist might be able to shed more light, but clinically speaking it is just basically taken as dogma. This is unfortunately true for many things in medicine. Disease processes (particularly in microbiology and oncology) have weird and predictable patterns, which are often beyond our current understanding."
] |
[
"What happens to an ant if I carry it miles away from its colony?"
] |
[
false
] |
[deleted]
|
[
"According to ",
"the wikipedia article on ants",
", an ant cannot join another colony because its colony scent (or lack thereof, after a certain period of time) does not match the new colony's scent. It will be attacked (probably).",
"The article does list an exception: ",
"The Argentine Ant",
". That species' genetic diversity is so globally similar that an ant separated from its colony is indeed able to join another, assuming they are also Argentine Ants."
] |
[
"I only knew because this question was asked before :) ",
"http://www.reddit.com/r/askscience/comments/rdg3g/what_happens_if_an_ant_is_released_outside_in_a/"
] |
[
"I only knew because this question was asked before :) ",
"http://www.reddit.com/r/askscience/comments/rdg3g/what_happens_if_an_ant_is_released_outside_in_a/"
] |
[
"How would the energy of an explosion or bomb be dissipated in space if there is no medium to carry a shockwave?"
] |
[
false
] | null |
[
"The energy would dissipate as an expanding ball of hot gas or whatever debris is left.",
"\nThe sockwave from a blast magnifies the damage but it isn't essential. If there isn't a medium to carry a shockwave the energy simply stays in the explosive."
] |
[
"If there isn't a medium to carry a shockwave the energy simply stays in the explosive.",
"It is just worth noting that sometimes the effect you see is ",
" of interactions with the medium. With nuclear weapons, for example, the \"blast\" wave in the atmosphere is mostly produced by heating of the atmosphere. So you are converting heat and radiation energy into blast energy, in essence (a superheat ball of air forms around the fireball and expands outward). In outer space, that doesn't happen, so you just have a lot more of the energy of the weapon expressed as heat and radiation."
] |
[
"The molecules that are produced in the chemical reaction of the explosion would move away from it at high speeds without hitting any other gas molecules. While in a medium the kinetic energy of those molecules is transferred to medium molecules, when there is no medium the reactants do not loose kinetic energy, so there is no dissipation."
] |
[
"How do you estimate the percentage of species not found if you do not know the total the number of species (since they haven't been discovered)?"
] |
[
false
] | null |
[
"A field scientist will not likely have enough time to survey an entire rainforest. However, one can easily survey several 10ft by 10ft patches within the area. Suppose you're in an area that's as large as 1 mile by 1 mile. You select several 10x10ft patches and count all the insects in those locations. You find that on average, there are 5 species present that have already been identified, and 5 species present that are new to science. You can then extrapolate and assume that in the entire square mile patch of land, that only half of the species present have already been identified. So yes, there's some guesswork and statistics involved, but it can be very accurate. Of course, you can actually test how accurate the predictions were by fully surveying the entire area, but this is rarely done due to time and funding constraints. "
] |
[
"You are absolutely right. We use a tool called species accumulation curves to estimate how often new species will be encountered as you survey additional area. Species accumulation is nearly universally an asymptotic function--it levels off as you go. For example, in the first 10x10 plot, each of the 5 species you find is new. In the second one, you might only find 3 additional species that weren't in the first one. In the one after that, perhaps only 2, and then 1, 1, 1, and 0, say. Once you stop regularly adding new species, you have reached the asymptote. Of course, it's not a perfect science, but when all else is equal, the pattern of species accumulation tends to be remarkably predictable. Ecology is a field with few generally applicable laws; some people think the species-area relationship is the only one."
] |
[
"Also, on a more global scale and over a longer period (decades, centuries): Looking at the rate of discovery of new species. I've no idea how the graph looks like, but the rate should decrease over time. From that you may make inferences. Of course, if there are new developments in, for example, oceanography, like much better technology and a sudden interest of governments to do much more research there the previous estimate may not hold, but after a while you could do a new one with the new data."
] |
[
"How do air fresheners that claim to remove bad odors work?"
] |
[
false
] |
Some air fresheners claim they can remove certain odors instead of simply masking them. How does this work chemically? Also, how can these air fresheners be scented themselves - wouldn't whatever's neutralizing the bad odors neutralize the fragrance as well?
|
[
"As a chemist who knows how this stuff works, I endorse the Edit as the correct answer."
] |
[
"Feel free to bury this under a more scientific answer, but I believe air fresheners that claim to remove odors do so via antiseptic properties. I suspect they kill bacteria that cause odors. ",
"edit: Some research has proven my suspicions wrong. Apparently aerosolized glycols in air fresheners, particularly triethylene glycol, bond with some odiferous airborne particles, after which they are heavy enough to fall to the ground.",
"http://en.wikipedia.org/wiki/Triethylene_glycol"
] |
[
"If you could somehow detach the triethylene glycol from the particles, they would still smell. It tends to bind pretty tightly though.",
"To be able to smell something, you have to be able to get a significant portion of the 'odiferous particles' back into the air. So while they probably will accumulate on the ground, I'm honestly not sure if you'd be able to smell them since the entire purpose of the triethylene glycol is to reduce how much of them will wind up in the air (ie, vapor pressure or something similar)."
] |
[
"How can we recreate structures from bones?"
] |
[
false
] |
How can we account for body parts made of cartilage, where muscle mass appears, etc.?
|
[
"where muscle mass appears, etc",
"Attachments of muscles to bones can be identified. The muscle masses can be inferred from a \"connect the dots\" approach, ie, this muscle goes from x to y and would bear z load."
] |
[
"Soft tissues exhibit mathematical relationships with regard to their proportions and suitability to purpose. By examining existing organisms, we can determine how musculature and cartilage etc. must conform to bone structure, and the recreations follow these relationships."
] |
[
"I don't think I understand your question, but if you are asking how we can 'create' different body parts from bones (i.e. bone marrow), it is because there are ",
"stem cells",
" within bone marrow that can be differentiated into bone cells, cartilage cells, and fat cells.",
"Note that in tissue engineering body parts are often not created this way (at least in my experience). Often pre-differentiated donor cells are used."
] |
[
"Why is the derivative of the area of a circle its circumference, and the derivative of the volume of a sphere its area?"
] |
[
false
] |
So the area of a circle is πr2 and its derivative is the circumference, 2πr. The same happens with a sphere. The volume is (4/3)πr3 and its derivative is the surface area, 4πr2 . Is this a coincidence? Also, can we use this property to predict similar quantities for circles/ spheres of higher dimension (its 'volume' so to say)?
|
[
"Which simplifies to 2pi*5 m. 30 metres of cable to raise it 5 metres around the ENTIRE GLOBE."
] |
[
"Check Here"
] |
[
"This reminds me of a question someone asked me recently:",
"You have a cable laid flat around the entire globe. You want to raise the entire thing 5 metres off the ground. How much more cable do you need? (Assume no obstructions, etc).",
"The answer just isn't intuitive."
] |
[
"Trying to make a \"Faraday Glove\" to insulate my hand from large static discharge, help?"
] |
[
false
] |
I haven't actually started fabrication yet, but I want to be sure I'm not barking up the wrong tree. I have a Van De Graaff generator and I want to make a chainmail glove that would be grounded so that I can discharge the dome without feeling anything. I've seen pictures and videos of guys staying relatively comfortable while discharging huge Tesla coils through full body Farady Suits, so I know this sort of thing is possible, but I don't know if something as simple as this glove: connected to ground would be enough to completely reduce sensation of the shock. Thoughts?
|
[
"Theoretically that would work (assuming the glove conducts well), but maybe an engineer can expand on some practical concerns like:"
] |
[
"If the glove is made of interlocking ringlets rather than woven metal fibers then there will be a lot of air-gaps and poorly conducting contacts that might cause parts of the glove to heat up a lot, or even arc to your hand. As much as possible you want to have continuous wires for the electricity to travel down."
] |
[
"Best material to use/coating to apply",
"I wouldn't coat the glove, best material... got money? silver-plated steel would be the best, otherwise i'd say galvanized. I'd be sure to protect against corrosion with so much surface area. ",
"Coverage of body, how far away does the rest of your body have to be away",
"Just use an insulated conductor from the glove to the bonding point. Shit, you could even run the wire under your clothes for a cleaner appearance. ",
"Joule heating",
"Unless we're talking gigantic, sustained energy discharges here, I doubt this would be a concern. If it is, then your only option really is to beef up the metal. Use heavier gauge stuff until you reach a point where there's enough conductive material to absorb the heat from high current without melting or burning you."
] |
[
"What Magnesium Compound is found in most brands of mineral water?"
] |
[
false
] |
Magnesium Oxide, Sulfate, etc? Which one? Don't ask me why I want to know, but it would be greatly appreciated! EDIT: Thanks for the answers! Upvotes given.
|
[
"Well, unless magnesium is precipitating as a salt, it will be present as an ion in solution with whatever counterions happen to be floating around and it won't necessarily always be the same counterion if it has more than one to choose from. Just pick up a bottle of mineral water and look for counterions that they usually list on the label."
] |
[
"it's MgCl2. Chloride is the most common anion on earth. (compare to Europa where sulfate is most abundant) MgSO4 is also used as a laxative, I doubt I would buy that water.",
"\nThe reason (most likely) is that when MgCl2 dissociates in water, it makes a very slight amount of MgOH+ by hydrolysis of water, making the pH just a hair below neutral (acidic). However if you use MgSO4, the second dissociation of (SO4)2+ is (HSO4)+ making the water slightly more basic, which probably doesn't taste too good. Think \"milk of magnesia\" flavor here. Acids for some reason are tastier, which is why we like lemon in our ice water and our coke to clean chrome bumpers I guess.",
"If the mineral water is carbonated, then some of the Mg may be in the form of MgCO3 which could act as a buffer to help keep the pH from getting too acidic during carbonation."
] |
[
"that's because there is no over-the-counter source of MgCl2, but that doesn't mean that's how brand names make it."
] |
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