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May 5

Extinction vs. evolution of defense mechanisms

Why is that some groups of animals manage to evolve defensive mechanisms against predators and other threats, while other animals (sometimes from the same taxonomic rank) do not evolve anything and become extinct? Is it about population size and slow rate of predation? Thanks. 93.174.25.12 (talk) 14:24, 5 May 2016 (UTC)

It's virtually impossible to say with certainty exactly why similar scenarios can turn out differently in evolutionary history. Lots and lots of factors come into play, and we are not really able to do controlled experiments for these scenarios. But yes, you basically have the right idea. I'll say a little more about the factors and give you some refs that will help you think about this issue: Selective pressure e.g. through predation comes in various strengths. Too low and it won't have much effect, too high and the species is wiped out right away. Allee effects can come into play for very small populations, and in that scenario, random chance can play a big role too. Alternative stable states discusses a little bit about how random fluctuation can lead to different outcomes in ecological models. Apparent competition provides another way of looking at this. If a predator P preys on species A and B, then the dynamics of A and B are actually similar to when A and B compete for a single resource R, because of the predator's prey switching. This gets in to top-down vs. bottom-up control of ecosystems, by species at different places in the food web, see here [1] for a brief description of those effects and here [2] for a scholarly review article. Finally, note that in the case where one predator P eats one species A almost exclusively, they will have strong pressure to not eat all of A, because if they did, P could go extinct too. So that's a very broad overview of the forces that influence whether species persist in a sort of Red Queen race or whether one or more go extinct. If you have further questions or would like more specific references let me know and I'm happy to provide more info. SemanticMantis (talk) 14:43, 5 May 2016 (UTC)

(ec) Note that extinction isn't just caused by predation, there's also a loss of habitat, food supply, climate change, disease, etc. One way in which predators can wipe out a species is if an invasive species is introduced which is far more capable than the prey, not giving the prey the time they would need to make massive adaptations. Species limited to islands with no natural predators are particularly vulnerable, like the dodo. On the other hand, if a predator in the same environment slowly evolves more capability to hunt the prey, the prey can evolve an ability to survive that predator at about the same rate. StuRat (talk) 14:45, 5 May 2016 (UTC)

Yes, the dodo, and also the Moa. Akld guy (talk) 04:59, 6 May 2016 (UTC)

Evolution is the summation of random mutations that enables a life form to compete. If they find that their Ecological niche is suddenly changing due to say climates changes or/and other predators or animals that are better at competing for the limited food supply moving in, then they may not be able to evolve quickly enough to adapt. This goes for other things as well. Take Microsoft. In the early years it was a predator. Now it a grown to be a slow moving giant dinosaur, leaving other more adaptive critters to nip at it ankles take away the food it needs, because they have better evolved and can do so more quickly.--Aspro (talk) 14:56, 5 May 2016 (UTC)

• Relevent here is Survivorship bias. Much of people's misunderstanding about evolution comes with the notion that, while mutations are random and capricious and arbitrary, only mutations which have "survived" are evident long enough to leave a significant record, so we have the mistaken sense that evolution has a purpose or a goal or makes living things "better". --Jayron32 16:10, 5 May 2016 (UTC)

I am actually suspicious that a species can go extinct through lack of predation. The dodo is a classic example, though some now say it has been misrepresented. If members of a species do not periodically make a run for their lives, will they continue to be able to run? Etc. Of course, the dodo never actually became too weak to move ... it just reached a point where it couldn't handle a sudden change for the worse. A species facing many predators is already at worse, and can't be so greatly surprised. I even wonder if a prey species tends to evolve a top speed that just barely ensures the predators will keep getting fed with its weaker members, though that would be in a sense a pretty remarkable extreme of altruism, already a controversial concept. But I have not really seen anything about this. Wnt (talk) 21:02, 5 May 2016 (UTC)

Hey @Wnt: do you mean you suspect lack of predation can cause extinction? Resource competition models show how species can go extinct with no predation. All you need is an uptake rate that's faster than the supply rate. Tilman's R*_rule_(ecology) is relevant here, see also [3] [4] [5]. But there's no predator even in the picture there. To get at the notion of lack or too little predation, you'd want to have a fairly stable system with say one predator, two consumers, and one resource, then show that removing the predator can cause one of the consumers to go extinct. In concept this could be investigated with microcosms, but I don't know as much about that. For the theory, check out my colleagues Chesson and Kuang (2008) [6] or maybe some of their other work [7]. I don't know if they have this specific scenario covered, but I suspect they do. Ecological modeling his hard, evolutionary modeling is hard, food web modeling is hard, and very few people have been bold/crazy enough to try to understand all three interacting. There are some simulation models out there that get pretty complicated, but depending on your epistemic stance, those don't really tell us anything about the real world. Then again, depending on your epistemic stance, no model no tells us anything about the real world ;) SemanticMantis (talk) 21:58, 5 May 2016 (UTC)

@SemanticMantis: Great answer - it is indeed hard. Even reality seems like a bad model, to be honest. For example, in the case of the Lake Guri howler monkeys, the long-term effect of losing a predator in the abstract is overwhelmed by the effect of huge extremes in population that occur immediately. It's like you have to ask what would happen if overgrazing yields a new equilibrium over many years that is not different from the old equilibrium, then would the predator's absence also cause specific changes in the former prey? It's not even really a coherent question, I guess. At least, I'm not sure how to frame it properly. Wnt (talk) 22:45, 5 May 2016 (UTC)

@Wnt: I wonder if you're getting at the distinction of neutrally stable cycles vs. stable limit cycles. For example in the classic Lotka-Volterra predator prey model, there is nothing to stabilize a preferred amplitude, and both species can come arbitrarily close to zero. This is very different from some other systems/ models, but if you look at the famous Hudson Bay data for lynx and hare pelts [8](I can't find our copy of this graph), you can see there's no clear lower limit to the fluctuations. It is hard to properly phrase the questions and comments, but if you want to continue the discussion, feel free to drop by my talk page. SemanticMantis (talk) 14:01, 6 May 2016 (UTC)

Percent deviation from additivity

What is the quantitative expression associated to the verbal phrase +/_x % deviation (expansion or contraction) from the addivity of volumes in water ethanol or water salt/sugar solutions?--85.121.32.1 (talk) 15:47, 5 May 2016 (UTC)

Could it be a fraction whose numerator include the difference between the volume of the mixture V and the volumes of the two components V1 and V2 and the denominator equals the sum V1+V2:

$\%\Delta V_{r}={\frac {V-(V_{1}+V_{2})}{V_{1}+V_{2}}}100$?--85.121.32.1 (talk) 15:52, 5 May 2016 (UTC)

or $\%\Delta V_{r}={\frac {V-(V_{1}+V_{2})}{V}}100$?

Which one of these two variants of this fraction which can be called relative volume difference are more appropiate?--85.121.32.1 (talk) 15:15, 6 May 2016 (UTC)

Is this question too complicated or intimidating for someone from here to attack it? (just a thought)--85.121.32.1 (talk) 15:32, 6 May 2016 (UTC)

I think it's a mainly a language problem. If you post the complete sentence as originally written, it'll be easier for us to work out the meaning. If the original sentence isn't in English, we'll probably also be able to provide a good translation. Tevildo (talk) 20:42, 6 May 2016 (UTC)

Doing some digging, I believe the problem sentence is in Apparent molar property#Alcohol, and I must admit that I don't understand it either. The sentence is:

“ The nonideality of the solution is reflected by a slight decrease (roughly 2.2%, 1.0326 rather than 1.055 L/kg) in the volume of the combined system upon mixing. ”

My question (which I think mirrors that of the OP) is (a) 2.2% of what?, and (b) where does the 1.055 L/kg come from? 1.0326 L/kg is the specific volume of a 20% w/w mixture of ethanol and water. Tevildo (talk) 07:43, 7 May 2016 (UTC)

Medical Satire

Thinking of putting this suggestion up to Wikipedia:WikiProject Requested articles but would like your comments first, as the editors here seem to have both feet on the ground.

Something, I have had simmering on my back burner for years, is that Wikipedia doesn't have an article on Medical Satire yet. There is a lot of it about – one could even say that it is a chronic pandemic. It is my (personal) belief, that it has a slow incubation period, starting in the early twenty’s (at the same time when protection of one's parental antibodies wains) with signs an symptoms only becoming manifest in the mid-thirties. Until such time, that medical science can come up with a effective treatment for this malady, is there any Quacks Doctors/nurses/radiographers/hospital porters/morticians/ etc., that can help me to put such an article together?--Aspro (talk) 17:13, 5 May 2016 (UTC)

You're talking about this [9] sort of thing, right? Here's [10] [11] some refs to get you started, lots of refs therein too. I would not have guessed the genre could trace its roots back to the 17th century! SemanticMantis (talk) 18:31, 5 May 2016 (UTC)

I don't think Wikipedia needs an article about every combination of literary form and subject matter. Is there something about satire of medicine that makes it more than the sum of its parts? -- BenRG (talk) 19:15, 5 May 2016 (UTC)

Well, we already have Political satire and Religious satire (despite "multiple issues"), also Comedy of manners. Alansplodge (talk) 17:51, 6 May 2016 (UTC)

Well, those articles sort of illustrate what I'm afraid the medical satire article would be: some boilerplate text along the lines of "satire of X has existed for as long as X; it is a way of avoiding cultural taboos surrounding the direct criticism of X; it can provide valuable insight into the popular perception of X at different points in history", etc., followed by the intersection of "list of works about X" and "list of satirical works". To be fair, there might be value in a separate list of historically important satire about medicine. -- BenRG (talk) 21:23, 7 May 2016 (UTC)

Tiltwinged and thrust vectoring airliners

Thrust vectoring says it's not currently used on commercial aircraft. In practice, what are chances of a commercial airliner with a sort of tiltwings that tilt to a desired angle and thrust vectoring engines for better control of the angle of attack? Costs aside, my understanding is that it would reduce (or eliminate) the possibility of stalling, diving, flat spins and other undesirable aerodynamic effects, so that even in case of pilot error (like Pulkovo Aviation Enterprise Flight 612) the proper airflow could be restored. Brandmeister^talk 20:38, 5 May 2016 (UTC)

If such things as tiltwings, tiltrotors, variable-sweep wings, variable-incidence wings and thrust vectoring were considered cost efficient, we would already have operational commercial aircraft with one or more of these features. Since we don't, I have to assume that the cost (in regard to money, weight and added complexity) of adding such features outweighs the benefits of them. WegianWarrior (talk) 21:04, 5 May 2016 (UTC)

I know nothing about this, but I had an impression the Bell Boeing V-22 Osprey was not a particularly safe aircraft. Does the benefit of having all those fancy features available for emergencies really outweigh the odds that something going wrong with them will cause an emergency in the first place? Wnt (talk) 22:33, 5 May 2016 (UTC)

A predecessor of the proposed Boeing 2707 supersonic transport was planned to have had "swing wings" (variable geometry), but they made the aircraft too heavy and the final design had a delta wing rather like Concorde. Alansplodge (talk) 22:44, 5 May 2016 (UTC)

The Concorde did have a movable nose cone, which allowed them to switch from a position with better visibility to one with better aerodynamics. However, the Concorde, despite being used for decades, didn't really prove to be commercially viable in the long term (only 14 were ever put into service). StuRat (talk) 15:00, 6 May 2016 (UTC)

All of the concerns listed are minuscule in commercial aviation. Stalling, uncontrolled diving and spins (of any type) are virtually unheard of. Notable cases such as the Airbus out of Brazil would likely still have a stall/spin because it was commanded. I'd be more keen on ideas like supercruise that allow fuel efficient supersonic transport. Also, efficient high-altitude jet design would be a higher priority, imo. --DHeyward (talk) 09:04, 6 May 2016 (UTC)

Agreed. While all of those high-tech additional moving parts might help a fighter plane during a dogfight, just flying more conservatively is enough to make them unnecessary for commercial aircraft. StuRat (talk) 15:00, 6 May 2016 (UTC)

According to Accidents and incidents involving the V-22 Osprey; "The V-22 Osprey had 7 hull-loss accidents with a total of 36 fatalities. During testing from 1991 to 2000 there were four crashes resulting in 30 fatalities. Since becoming operational in 2007, the V-22 has had three crashes resulting in six fatalities including one combat-zone crash, and several minor incidents." Alansplodge (talk) 17:43, 6 May 2016 (UTC)

Infact all modern commercial airliners have Thrust reversal-"Thrust vectoring" as brake. Beyond that vectoring and Variable-sweep wing make no sense for big planes and with very few, very expensive exeptions, like the Rockwell B-1 Lancer and Tupolev Tu-160, there are no Variable-sweep wings on huge planes because they "only" give you more speed for a very high price and additional risks. Just imagine you would have to make shure a Airbus A380 with defective variable-sweep wing, fixed in its deltawing travel settings, would need to be able to land on an already "almost to short for this giant plane" airstrip. --Kharon (talk) 01:17, 8 May 2016 (UTC)

Could we be in a black hole right now?

Could we (Earth and visible universe) be inside a black hole right now and since the beginning of times? --Llaanngg (talk) 22:35, 5 May 2016 (UTC)

See Black-hole_cosmology. Some people find this idea convincing, others don't. I'm not even sure if it's a falsifiable claim or not. SemanticMantis (talk) 22:46, 5 May 2016 (UTC)

This exact same question was asked just last month. Vespine (talk) 23:08, 5 May 2016 (UTC)

And yet, nobody had linked our most relevant article in that thread. I skipped that round because I don't know much about this topic. But this time I looked around a bit because I felt the last round was unsatisfactory, though there is what looks to be expert commentary from Ben there. Anyway, sometimes it's ok to ask the same question again- sometimes you get different and possibly better references. SemanticMantis (talk) 13:54, 6 May 2016 (UTC)

An antidepressant

I just found out by accident that citalopram, a rather popular antidepressant, is a salt of Hydrobromic Acid. Good Lord, it is a very strong mineral acid. To have it in the GI tract on a daily basis... Isn't it dangerous? --AboutFace 22 (talk) 22:42, 5 May 2016 (UTC)

Salt (i.e. table salt) is a salt (chemistry) of hydrochloric acid. The neutralization of an acid into something more neutral is what makes a salt a salt. Wnt (talk) 22:47, 5 May 2016 (UTC)

There a comprehensive list of adverse effects here. There are not any GI track specific effects though, only related to SSRI discontinuation syndrome. --Llaanngg (talk) 23:23, 5 May 2016 (UTC)

You know your stomach is filled with acid, right? An enormous number of drugs are administered as salts, often hydrochloride salts. --71.110.8.102 (talk) —Preceding undated comment added 05:50, 6 May 2016 (UTC)

As above. Your stomach is already at pH 1.5-3.5 (gastric acid, a few mgs more acid isn't going to do much. 213.105.166.119 (talk) 06:46, 6 May 2016 (UTC)

May 6

What happens if long enough rope is on earth?

49.135.2.215 (talk) 01:26, 6 May 2016 (UTC)Like sushi

What? Evan ^{(talk|contribs)} 01:27, 6 May 2016 (UTC)

Earth destroyed by black hole. Sagittarian Milky Way (talk) 02:06, 6 May 2016 (UTC)

Didn't somebody ask this like a week ago? ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:08, 6 May 2016 (UTC)

You can use it for a space elevator. It had better be a really strong rope though. --71.110.8.102 (talk) 06:15, 6 May 2016 (UTC)

I imagine it will be like the infamous "piece of string" - always just slightly too short for whatever it is needed for. 81.132.106.10 (talk) 09:03, 6 May 2016 (UTC)

If a long rope is on Earth, well, a long rope is on Earth. ThePlatypusofDoom (Talk) 12:29, 7 May 2016 (UTC)

The Earth will hang itself.--Heron (talk) 07:36, 8 May 2016 (UTC)

pressure enough to make "carbon string"?

(I can not be watching)

49.135.2.215 (talk) 01:28, 6 May 2016 (UTC)Like sushi

Read Carbon fibers, Carbon nanotube and Linear acetylenic carbon. High pressure may not be required. Graeme Bartlett (talk) 11:18, 6 May 2016 (UTC)

Edible-nest swiftlet

Our article on the subject is quite poor. I was wondering if anyone knows the average weight of each nest?Lihaas (talk) 10:17, 6 May 2016 (UTC)

The German article (de:Weißnestsalangane) says: "Der Durchmesser beträgt ungefähr 6, die Höhe 1,5 Zentimeter, das Gewicht liegt bei ungefähr 14 Gramm." (diameter 6cm, height 1.5 cm, weight around 14 grams). --Wrongfilter (talk) 10:31, 6 May 2016 (UTC)

Thanks

Man, it takes a heck of a lot to make 1 kg...which sells for some $2000.Lihaas (talk) 13:41, 6 May 2016 (UTC)

So about 28 cents apiece: have a look at what they have to do to collect them. Alansplodge (talk) 17:38, 6 May 2016 (UTC)

Isn't that 28 dollars apiece ? StuRat (talk) 03:55, 7 May 2016 (UTC)

D'oh! Quite right StuRat, $28 each. Still, I suspect that's the wholesale price rather than what the chap at the top of a precarious ladder gets. Alansplodge (talk) 13:35, 8 May 2016 (UTC)

If they paid better, maybe they could afford sturdier ladders (or how about a cherry picker, or at least a net ?). StuRat (talk) 23:24, 9 May 2016 (UTC)

I like how the video clearly states that the nest has no nutritional value and adds no flavor. I bet it's a heck of an interesting texture though :) SemanticMantis (talk) 17:49, 6 May 2016 (UTC)

I dunno about the youtube video but it makes sense at about 30 or so dollars...and its apparently rich in protein but an acquired taste.Lihaas (talk) 12:42, 7 May 2016 (UTC)

@Alansplodge: Theyre farmed too. (hence easier)Lihaas (talk) 13:06, 8 May 2016 (UTC)

Thanks Lihaas. Gosh, I don't know how I missed swiftletfarming.blogspot. Alansplodge (talk) 13:35, 8 May 2016 (UTC)

Extracellular sodium channel blockers vs. intracellular sodium channel blockers

Sodium channel blocker lists both extracellular and intracellular classes of these substances. I noticed that the intracellular forms include several crucial drugs, including a number of WHO-EM drugs (lidocaine, bupivacaine, procainamide, quinidine, phenytoin, carbamazepine), whereas the extracellular forms are some of the most lethal neurotoxins known (saxitoxins, neosaxitoxins, and tetrodotoxins). It would seem that blocking one side of the sodium channel versus the other makes a significant difference, but what exactly is that difference? —/Mendaliv/^2¢/_Δ's/ 20:39, 6 May 2016 (UTC)

Excellent question! Two thoughts. First, the sodium channel that both TTX and lidocaine act upon is a voltage-gated sodium channel. This means that, unlike the ligand-gated nicotinic sodium / potassium channel, the voltage gated sodium channel is not meant (evolved) to be activated / deactivated / inactivated / deinactivated by a neurotransmitter (ligand) molecule binding to it from the outside. So, whatever molecule binds to it from the outside and blocks it, is either a toxin or a drug, and not a part of a natural physiological processes taking place in the organism. Second, there is no strict way to distinguish between a "poison" and a "drug" - it is purely a question of dosage and intended (or unintended) effect. Toxins are poisons produced by living organisms. It so happens that TTX is used by some fish and amphibian species to protect themselves; so it is ingested by the predator and acts on the predator's neurons from the outside instead of being transported into the neurons first. There are toxins that are transported into the cell, too: for example colchicine or taxanes that interfere with cell division, or Tetanus toxin that blocks neurotransmitter release into the synaptic cleft. But for a fast-acting toxin your best bet is to block the action potential generation and propagation or synaptic transmission from the outside of the neurons, which is what most fast-acting toxins do. --Dr Dima (talk) 22:13, 6 May 2016 (UTC) Continued: as to why the voltage-gated sodium channel "blockers" (actually, mostly modulators) found in medical use bind to the intra-cellular sites of the sodium channel - it may be by chance (novocain was discovered in 1905, long before the sodium channel itself was discovered). Or it may be because binding to the intra-cellular sites allows to modulate, rather than physically block, the channel, which may be advantageous in medical applications. --Dr Dima (talk) 22:50, 6 May 2016 (UTC)

What I can say for sure so far is that an answer for this one won't be easy. There seem to be some different effects of the two types of drugs, [12] and allegedly (I don't know if this is reproducible) the extracellular toxins also do something to calcium channels ... something subtle. [13] The local anaesthetics affect TTX-resistant channels. [14] There are literally hundreds of papers in PubMed that discuss tetrodotoxin and lidocaine somehow or other, and they're not the easiest papers to read... (Here's another one that might be informative, modeling extracellular access of drugs, but it is not finger food) One trivial thing is TTX is simply longer-acting, [15] but that doesn't really explain it when a drug is taken with the intent of long-term inhibition. Hmmm, hit #249 is a goodun: [16] says "The contrasting patterns of effects between TTX and local anaesthetics suggest that blockade of TTX-sensitive sodium channels alone may not be responsible for the effects of cocaine, lignocaine and benzocaine." That's kind of ancient, but there is TTX-R stuff about lidocaine coming out to the current day: [17] Wnt (talk) 00:18, 7 May 2016 (UTC)

Very interesting and informative responses, thank you both! So my take on this is that the intracellular versus extracellular distinction might not be the crucial distinction. For instance, it looks like STX and TTX are voltage-insensitive (whereas most pharmaceutical Na+ blockers seem to be voltage-sensitive). Related to this seems to be the affinity, with STX/TTX having very high affinity. Taking off something Dr Dima said above—noting that the distinction between drug and toxin is a fairly arbitrary one—I began to wonder if the problem with STX/TTX is one of therapeutic index... or more simply that useful doses would be extraordinarily small. I saw one article suggesting the use of either STX or TTX for bladder pain syndrome, with results in a human study of anesthesia lasting around 90 (!) days, for example, with a dose measured in micrograms. —/Mendaliv/^2¢/_Δ's/ 03:43, 9 May 2016 (UTC)

Magnetic quantum number

I recently did some major rewriting at magnetic quantum number, and have a leftover sentence about Larmor precession. The problem is, I have no idea how to relate it to the article. As best as I could figure out looking at a few web sources, the Larmor frequency is a function of the atom, not the m of a particular electron therein, and so electrons with any given m all precess at the same frequency?

Bonus question: I was kind of wondering where the angular momentum goes if multiple photons hit an atom. For example, you have a hydrogen atom with bright multiple frequencies of light shining on it. The first photon carries sqrt(2) reduced Planck units of angular momentum and knocks the atom from its base state (0) to the first level (sqrt(1*2)); all the angular momentum is conserved. But any photons after that knock it up by a smaller amount, not much more than 1, because sqrt(l(l+1)) approximates to l+0.5. Now I suppose this is reversible - it could emit back out photons with the same total angular momentum - and so in a sense the momentum is conserved. But the vector isn't! Or am I missing something... (I'm thinking this is something about how random angular momentum adds up ... but in which direction(s)?)

Anyway, I'd much welcome some eyes at magnetic quantum number to see if I screwed it up badly. Wnt (talk) 21:29, 6 May 2016 (UTC)

Also, I think there is no way to tell by looking at the shape of the orbital whether it has a +m or -m (but you can tell the absolute value of m). This would be the equivalent of seeing a map of a planet's orbit and not knowing from that alone which way the planet is headed. But can someone confirm with a source?

Hydrogen 6h orbital, with m=-5. The electron wave cycles through its complex phase five times going around a large circle. With m=5, it cycles in the opposite direction... as if moving through these phases from one lobe to the next.

More generally, it would be nice to get a more intuitive feeling here. If you look at a hydrogen and you see it has a p_x electron, that electron has an angular momentum around the z axis. Does this truly mean that the electron is orbiting in some sense, i.e. that over time it is moving either clockwise or counterclockwise about the z axis? Now there are some real howlers about the meaning of the + and - lobes of orbitals online, but my understanding is that they represent the phases of a wave, and that in intuitive terms this means - correct me if I'm wrong, and this sounds wrong! - that if we somehow could know where the electron really was in the orbital without disturbing its momentum, then in some short time (how short?) it would fall through the nodal plane and turn p in the other sign of lobe in something like half the Bohr orbital period (half of 150 as, according to page 9, but does this get larger with principal quantum number? I'd guess so, and that the extra time corresponds to the extra little lobes near the nucleus in 3p orbitals and up, which it has to pass through?) And so I take the angular momentum to possibly indicate that the electron in a p orbital jumps from lobe to lobe via a course that goes a particular direction around the nucleus? But at some point the analogy seems to break down since the electron jumps over a nodal plane, something with no apparent particle-mechanics analogy. Wnt (talk) 14:29, 7 May 2016 (UTC)

It "jumps over a nodal plane, something with no apparent particle-mechanics analogy"? Exactly! Because it's a wave-like/particle-like entity, not quite either one. Even on a plucked guitar-string, one can easily see stationary points. If one is very careful (and my quantum-mechanics prof was awesome at this!) one can lightly place a finger at half the guitar's length, pluck the string, and then remove finger...both halves of the string vibrate, and the guitar is stably emitting an octave higher than normal. The hand-wave(ha!)-ing explanation is that the electron (if you are still thinking it's a particle that has discrete positions at specific times) can tunnel across the node. The wave explanation is that there is just a node on the single wavefunction, so "the wave" is on both sides simultaneously, or the string need not "move" the middle in order to be moving on both sides. wikiquote:Quantum mechanics has some good comments from experts about how often QM does not make self-consistent macroscopic/real-world sense. DMacks (talk) 21:03, 7 May 2016 (UTC)

@DMacks: I recognize that many sources say QM is hard to understand. But I remain unsure when and how much those limits can be pushed. What emboldens me most is that alternating current can be written in similar crazy notation, with phase angles and complex numbers. Yet it has an intuitively comprehensible basis. So I feel like I shouldn't give up trying to find one here. I am thinking (not sure) that if you look at the f orbital diagram I added to the article, that you can sort of see how an f orbital with m=0 is vibrating up and down between lobes in the z-axis, and one with m=1 is orbiting in something like an x-z plane from lobe to lobe, with only a slight motion around the z axis, whereas the m=3 case is more or less the same orbit, but now totally in the xy plane so that all the angular momentum is around the z axis. The motion from lobe to lobe (or node to node) would seem to mark some kind of path...

Which gets me to another question, I suppose. If you "lightly measure" a population of electrons to be within one particular lobe of an f orbital, say, can you measure them within attoseconds later and see that they may move to the adjacent lobes, but not all the way to the lobe on the far side of the atom? Wnt (talk) 01:02, 8 May 2016 (UTC)

For an analogy of the "is the electron moving or not" question, consider a flashlight/laser beam shining continuously on an absorbent (dark) surface. The light has momentum (pointing along the direction of the beam, toward its destination). But the situation is also time-independent. Is the light moving? In some sense yes, in some sense no. It's the same question for the electron orbits. That it's a quantum wave function, and the motion is circular instead of linear, doesn't matter as far as this question goes. The electron orbits in the same sense that the light moves.

For a classical analogy of "jumping through nodes" consider a standing wave. You can think of a standing wave in one dimension as a superposition of left-moving and right-moving waves. Is the light (or whatever) moving left and right through the nodes? I don't know, but whatever your answer is in the classical case, that's the answer in the quantum case too. -- BenRG (talk) 17:46, 8 May 2016 (UTC)

Maybe I'm being simple-minded here, but I feel like if an electron has energy and angular momentum it has to be moving. Still, the whole question may be complicated. It seems like one guy at the center of what has been published lately on attosecond transient absorption spectroscopy, who was looking at things like the transition of an electron from 4d orbitals to Rydberg atoms, says "Such a noble-gas ion which inherits a hole in the valence p_z orbital is not anymore in an eigenstate but rather in a superposition of different quantum states." And what he can do seems a lot blunter than what I wanted, looking at where an electron is in an orbital and then looking a few attoseconds later, which for now still seems like nothing but a thought experiment AFAICT. This is all far beyond my understanding. Honestly, I'm still not really understanding what that ring diagram I added above really means - the complex phases are normally shown as spaces between orbital lobes, but in this series of images, even for p orbitals (except along the z axis! due to multiple possible orientations superimposed?), they are shown as linkages, probably the very "orbits" I was looking to see. But dang it, if only I got what the e^itheta in these solutions "really means", and comprehended how these segments are bricked together to build up orbitals, I feel like a lot of quantum mechanics would be very intuitive. Wnt (talk) 20:16, 8 May 2016 (UTC)

No one knows why nature chose complex-valued wave functions over real-valued or quaternion-valued or something else, so you're in good company if you don't understand that.

It's important to understand that these orbitals are not the only states the electrons can be in, they are just an orthonormal basis (linear algebra) for the states. Any orthonormal linear combination of those states would also work. In commons:Hydrogen orbitals 3D#n = 2, they've chosen a different set of 2p basis vectors than you usually see in these collections of pretty pictures. Usually, they would use the middle one, the sum of the left and right ones, and the difference of the left and right ones (times a normalization/phase constant). The left and right ones are e^iθ and e^−iθ times a function of r and φ, and their sum and difference are cos θ and sin θ times that function of r and φ (still ignoring the constant factors). cos θ and sin θ have two peaks each, of opposite complex phase (+1 of phase 0 and −1 of phase 180°), and those two phases are colored blue and yellow in these pictures. So the sum and difference of the left and right pictures would look like the center picture turned on its side, which is what you usually see in pictures of the 2p orbitals (e.g. here). It's not the same functions drawn in different ways, but different functions (spanning the same space) drawn in more or less the same way.

All of these orbitals taken together are a complete basis for bound states, so any bound electron wave function is a linear combination of them—even one where the electron is localized, and very far from the atom, and basically orbiting it classically, as in a Rydberg atom. But these approximately classical states are combinations of basis orbitals from different rows of commons:Hydrogen orbitals 3D, which means they don't have a definite energy or angular momentum. The guy you quoted misspoke when he said "a superposition of different quantum states". He meant "a superposition of eigenstates of different quantum numbers", i.e., a weighted sum of basis functions from different rows of commons:Hydrogen orbitals 3D. -- BenRG (talk) 05:29, 9 May 2016 (UTC)

@BenRG: I suppose I still don't fully understand the superposition process and how it affects angular momentum. If I simply look at one of those looped p orbitals, I can imagine that the complex phase simply means when the electron is most likely to be at a particular point, almost like with alternating current. It is around the position with a +1 value at t=0, around the position with +i at t=a/4, around -1 at t=a/2 etc., where I would expect a ought to be some small multiple (1?) of the Bohr period. And if all that were true, then I see it having an angular momentum to match m=1 or m=-1 (per the right hand rule). However, if I sum these two together, getting the yellow and blue spheres, now it's just going back and forth straight along the x or y axis, and it has no angular momentum. Now of course I pretty much have to sum them together if I expect the electron to be located somewhere in particular, like pointing at another atom, but don't know which way it's moving - I think that's telling me the angular momentum is in a superposition of eigenstates in those instances? If that's true, then the yellow-and-blue version for m=0 should be taken to mean that we know the angular momentum around z is zero, and we don't know which way it is in the other axes. But is any of this right? And if it is, might we (by which I'm afraid I mean you, sorry!) get some sources and modify one of the articles to somehow explain the difference between the ring and the yellow-and-blue pictures of an orbital? Wnt (talk) 11:30, 9 May 2016 (UTC)

Looking through [18], it does appear possible to deduce m by looking at the orbital. The absolute value of m is equal to the number of red bands (phase = i) in any torus for a given orbital (and zero for the blue-and-yellow solutions on the page). The sign of m is negative if blue, purple, red run clockwise in any given torus, and positive if they run counterclockwise. I suppose a planetary orbit would also provide the sign of its angular momentum, if it were drawn as a complex number in which the e^itheta angle is a function of time. Wnt (talk) 15:07, 9 May 2016 (UTC)

Alright, to bite the bullet here, in a Bohr model, FWIW:

$v={\sqrt {Zk_{\mathrm {e} }e^{2} \over m_{\mathrm {e} }r}}.$

For now I'll say it's an actual hydrogen (Z=1), leaving me to work 8.9875517873681764×109 N·m2/C2 * (−1.602176565(35)×10−19 C)^2 / 9.10938215(45)×10−31 kg. Uck... comes out, in the unlikely event I did not foul up, to 253.3 N m2/kg = 253.3 m3/s2. Divide by r, take the square root, that's m/s. For the Bohr radius of 0.0529E-9 m, I get the value for v is 2188058 m/s. To go around the Bohr radius then is 24.18 attoseconds ... no, times 2 pi, because it's the circumference ... 151.9 attoseconds. Caveat being that the ground state in the Bohr atom has angular momentum with n=1! Well, I'm starting where I can. Anyway, the classical period is expected to be proportional to n^3, the angular momentum to n, the velocity to 1/n, the radius to n^2 ... so the time to cross each segment between two red bands in high-m orbitals like the graphic above would be inversely proportional to n^2. (Not to m, but for the highest-m orbitals that look like a single torus around the z axis, m is equal to l is equal to n) So clearly, unlike what I was first wondering, the electron isn't simply vibrating at some base Compton rate as it goes around one of these tori. (According to Compton wavelength the classical radius of an electron, FWIW, is 2.8E-15 m, much smaller than any of these features, while the other measure is simply the Bohr radius) The ionization energy for the innermost orbital is -13.6 eV, vs. 510 keV electron mass, so the Compton wavelength of that negative energy, if there were such a thing, would be 37500 times higher, or 1.05E-10 meters ... hmmm, that's close to the 3.323E-10 meters of the Bohr circumference. Especially curious since that should go up proportional to n^2, just like the length of the circumference in the higher-energy orbitals, because the ionization energy drops per n^2. Is there anything in physics about these orbitals somehow reflecting the Compton wavelength of the ionization energy? That's weird! Wnt (talk) 21:31, 9 May 2016 (UTC)

Does petting an human release endorphins?

In the past I've heard explanation why people are relaxed while getting petting, but I forgot the explanation. Is it because that the body release endorphins? (I know for sure that it releases the hormone oxytocin but I'm not sure about the endorphins) 93.126.95.68 (talk) 23:28, 6 May 2016 (UTC)

Probably more so than with your average dog or cat. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:38, 6 May 2016 (UTC)

Apparently so. Complementary Psychosocial Interventions in Child and Adolescent Psychiatry: Pet Assisted Therapy--Aspro (talk) 23:45, 6 May 2016 (UTC)

If I'm nor mistaken, this article deals with petting pets rather than petting human. Am I right? 93.126.95.68 (talk) 23:54, 6 May 2016 (UTC)

Am I right or mistaken that humans are animals also!--Aspro (talk) 00:32, 7 May 2016 (UTC)

"petting" is a fairly antiquated term for physical affection...like "heavy petting" instead of "making out"...the OP is using the term in this manner...68.48.241.158 (talk) 01:51, 7 May 2016 (UTC)

I doubt it releases Oxycontin. You were probably thinking of oxytocin. --71.110.8.102 (talk) 04:46, 7 May 2016 (UTC)

Thank you, I corrected it. 93.126.95.68 (talk) 12:20, 7 May 2016 (UTC)

According to Dr Nor Ashikin Mokhtar, there are many hormones and neurotransmitters released during foreplay but oxytocin and endorphins only seem to be released during an orgasm. Richerman (talk) 08:00, 7 May 2016 (UTC)

According to the article oxytocin "In a 2003 study, both humans and dog oxytocin levels in the blood rose after five to 24 minutes of a petting session."93.126.95.68 (talk) 12:22, 7 May 2016 (UTC)

May 7

Mechanisms and or Functionalities sought

Apparently this exists in the game. If so,

1. What's the mechanism(s)/functionality(s)
2. How it does what it is suppose to do?

Apostle (talk) 09:45, 7 May 2016 (UTC)

When I googled world of warplanes ufo mechanism, I came to this site. Take note of the date (April 1) and the comment "Thanks for laughing along with us on April 1st!" under the picture and see if you can come to any conclusions on your own. In the future, questions about games should probably go in the Entertainment desk. Matt Deres (talk) 12:16, 7 May 2016 (UTC)

For proposed actual use of flying saucers in the military, see Avrocar. StuRat (talk) 15:09, 7 May 2016 (UTC)

Unsatisfying. Thank you (both) anyway -- Apostle (talk) 18:40, 7 May 2016 (UTC)

Place with the largest observable part of the other celestial hemisphere

In what place on Earth the largest part of the other celestial hemisphere could be observed at night (such as in northern celestial hemisphere with the largest number of southern hemisphere objects or vice versa)? Thanks.--93.174.25.12 (talk) 13:47, 7 May 2016 (UTC)

The closer you get to the equator, the more of the "other" celestial hemisphere you should be able to see. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:55, 7 May 2016 (UTC)

A tall vantage point should help as well. Combining the two, Chimborazo should be a good choice. Kilimanjaro wouldn't be a bad choice either. --82.164.37.199 (talk) 14:34, 7 May 2016 (UTC)

preheating oven pointless?

I notice that to put food in I have to basically open the door all the way and for at least 2 or 3 seconds...all the hot air is let out..if google "preheating oven pointless" a lot comes up to suggest it's true....true??68.48.241.158 (talk) 16:36, 7 May 2016 (UTC)

No, definitely not pointless because the thermal capacity of the heating elements and the metal structure of the oven far exceeds the thermal capacity of the air released on opening. The cooler air that flows in is quickly heated to the temperature of the metal that surrounds it. Dbfirs 16:40, 7 May 2016 (UTC)

what you say is scientifically true, of course...I wonder about the practical difference...is there that much of a significant practical difference considering how quickly modern ovens heat up...??68.48.241.158 (talk) 16:51, 7 May 2016 (UTC)

Yes, I was thinking of older ovens with a high thermal capacity. If the oven heats up to the required temperature in a few seconds, then pre-heating is indeed almost pointless, but only my small halogen oven does this. Dbfirs 16:58, 7 May 2016 (UTC)

well, seems like it get to 400F in 6 or 7 minutes...to 300F in 4 or 5 minutes...68.48.241.158 (talk) 17:05, 7 May 2016 (UTC)

It also depends on what you are using your oven for. Baking often needs a constant even temperature for a relatively short time, so pre-heating is important. If you are roasting a joint then you can just add five minutes to your cooking time instead of pre-heating. Dbfirs 17:09, 7 May 2016 (UTC)

Preheating where needed is probably not mostly about times or temperatures. These are factors, but the biggest one is probably that during heating the elements or burners give of a lot of infrared which may not be want you want. BTW, this was discussed before on the RD, see Wikipedia:Reference desk/Archives/Science/2009 October 9#Why preheat the oven?

You gave figures for how long it takes to reach the desired temperature from cold, but not how long it takes to return to the temperature after opening (if the elements even come on again). If it's 1 minutes vs 4 minutes this is still a very big difference if the total time is short. Note that if you've been using an oven enough with a variety of different things, it's not that hard to see how big a difference having the elements on as well as not preheating can make.

Also if you read some of the results from your search, you'll likely find people with similar comments e.g. [19] [20] [21]. There are a few who appear to be speaking from actual experience (rather than simply theoretical which to be frank is likely too spherical cow to be useful) e.g. [22] (and some of the comments in the discussions) but it's not always clear what the specific experience involves.

I'm sure people preheat in a lot of cases where it's not really particularly useful. And I'm sure preheating with modern ovens and smaller ones is often less important than with older ones and larger ones. But this is different from saying preheating is always useless (other than for time saving if you remember to preheat during prep) with most resonable size home ovens.

Nil Einne (talk) 20:39, 7 May 2016 (UTC)

I imagine for things like roast potatoes that bringing them slowly up to temperature in a bath of cold duck fat would result in a quite different outcome to dropping them into hot fat. Similarly with roast chicken, the skin would dry rather than crisp. For stews and the like I doubt it makes much odds. Greglocock (talk) 00:01, 8 May 2016 (UTC)

Its simply a timing issue, because recipies need to set a reliable time frame to cook or roast something properly. For one oven may need 15 minutes and another only 5 minutes to heat up, you can not include that. With some cooking experience you can estimate and include the preheating phase with your oven and very likely save some time. --Kharon (talk) 00:53, 8 May 2016 (UTC)

May 8

Paint color matching.

When I take a chip of paint to a DIY store and have them make a matching paint - what kind of sensor do they use? Seems like a regular RGB camera wouldn't cut it...do they switch light sources? How does it actually work?

SteveBaker (talk) 02:21, 8 May 2016 (UTC)

Colorimeter?--178.107.62.251 (talk) 03:34, 8 May 2016 (UTC)

One actually can use a regular camera, for example, Sherwin-Williams has an app.[23] DMacks (talk) 04:13, 8 May 2016 (UTC)

I'm DEEPLY skeptical that a cellphone camera, with unknown lighting, could possibly, remotely, come up with a useful color match to existing paintwork - and to be fair to Sherwin-Williams, that's not what they're claiming. They suggest using colors captured in photos for "inspiration" and other such things - but they never say it's going to match...and nor would it. SteveBaker (talk) 18:00, 9 May 2016 (UTC)

Not sure how good it is, but [24] has some technical discussion. That and other sources like [25] [26] (second one is about car paint colour matching) says a spectrophotometer. One source I came across called it a Spectroradiometry, but I think photometer is more accurate for the type of machine normally used. Admitedly I wonder if spectrocolorimeter may be even more accurate for what being done, but I didn't read enough to know for sure.

Anyway I found this PR about one machine used [27] which may help find out PR about this specific machine [28], if you cut through the PR I would guess you could get some info on what's actually involved. Colour Match Navi CT-X is evidentally one device used for cars although I could find very little about it. The device mentioned in the Gizmodo link is more productive [29]. I also noticed a lot of AliBaba results e.g. [30], I would guess some stores are using products sold there.

I would also assume/hope, there must be some published science about these commercial computerised paint colour matching machines, I didn't notice any but a targeted search may work better.

Nil Einne (talk) 14:23, 8 May 2016 (UTC)

Hmmm - so according to the HowItWorks article - they shine "pure" white light onto the target then capture the reflected intensity across the visible spectrum in 10nm steps using a bunch of interference patterns. That's kinda what I thought.

SteveBaker (talk) 18:00, 9 May 2016 (UTC)

Mobile phones in walkie-talkie mode - range?

I understand that a mobile phone connecting directly to another mobile phone instead of via a cell tower would have greatly diminished range because the cell tower provides the power so that the phone doesn't have to but what would that range be? Using the hardware usually used to connect to the nearest cell tower, how far could phones talk to each other in a such a walkie-talkie mode? — Preceding unsigned comment added by 78.148.108.58 (talk) 19:52, 8 May 2016 (UTC)

This question really devolves pretty quickly when you start getting into technical details. Cellular networks are specifically designed to be asymmetric, not peer-to-peer; and this design is embodied in every detail of the hardware, from the amplifier design to the antenna design to the frequency choice to the digital and software protocols that are used. A significant limiting factor - perhaps the most significant limiting factor - is the nature of the shared channel, and if we re-architected a mobile phone for direct peer-to-peer operation, this changes everything about the communication signal quality. Every single detail of your mobile telephone's radio is defined by its mechanism for cooperatively sharing that channel with a tower and with other users. So, we simply can't answer the original question as posed - not accurately - because cellular telephone electronics don't work in this mode. If we start changing details or making approximations, we haven't got a cellular telephone anymore.

How familiar are you with radio technology? Before we start lobbing specifications at you, it might be good for you to review some basic terminology for telecommunications engineering and radio-frequency engineering.

At best, we could show you some specifications for other types of radios whose size and shape are "similar" to mobile cellular telephones. For example, a handheld VHF radiotelephone for use at aviation radio frequencies will reach one or two miles (if you're on the ground); and you might manage to reach as far as ten or twenty miles if you're at altitude - say, two miles above the ground, with a clear line of sight to your remote station. Aviation VHF is quite a bit lower frequency than the bands used by a modern mobile cellular telephone. To first-order approximation, that means that your cellular telephone will have a shorter range and will be much more limited by any obstacles (like walls, buildings, and terrain, and even humidity in the atmosphere) that block your line-of-sight.

I happened to be reading this article - on natural antennas - earlier this weekend. It's fascinating to see some cold, hard numbers - a 15 watt HF radio (which is much lower frequency and much much much much greater power than your mobile telephone) will work over a few miles through dense forest; but if you use a tree as an antenna, you can get as much as 20 or 30 dB of antenna gain. If you were in a forest and wanted to use a modern mobile cellular telephone, you'd probably have to be within a mile of the tower, or the signal would drop below usable levels.

Nimur (talk) 20:47, 8 May 2016 (UTC)

• Some cell-phone manufacturers marketed cellphones which were known for walkie-talkie modes (known as Push-to-talk). Nextel was one of the best known. --Jayron32 23:10, 8 May 2016 (UTC)

Yes, but that technology was still mediated by the centralized cellular network. There was no direct device-to-device radio link. For example, iDEN, the Motorola-branded technology that powered Boost Mobile and NexTel, was a trunk radio carrier. It has the superficial appearance of being a "walkie talkie," but that technology actually has more in common with VoIP than with a real, direct radio link. Nimur (talk) 02:42, 9 May 2016 (UTC)

TETRA (Terrestrial Trunked Radio) Mobile Stations (MS) designed for use by emergency services can communicate in direct-mode operation (DMO) in situations where network coverage is not available. DMO also includes the possibility of using a sequence of one or more TETRA terminals as relays. AllBestFaith (talk) 13:27, 9 May 2016 (UTC)

Neat! That's very similar to a lot of research into mesh networks and ad-hoc digital packet radio networks used by advanced HAM operators. But I'm pretty sure TETRA is not used in the United States by emergency services. We have a diverse set of local, state, Federal, and special-purpose services, so perhaps some organizations use it... but they are exceptions, not the rule.

Here's a pretty cool rundown of the historical and current radio technologies used by the CHP: California Highway Patrol radios, from WB6NVH. That guy has great photos, does a deep technology dive, covers current and historical systems, and even lists sources .... he even links to the authorization-legislation!

Such radios are neither "mobile phone" nor "walkie-talkie" - the preferred terminology is "Tactical Network Radio" or some variation therein.

It's hard to find good technical documentation on those technologies - what's left of the Motorola radio technology division is struggling to stay afloat ever since our friends at Google decided to hack the company to pieces. Most of the technology offerings are listed on the Motorola Solutions webpage - the real Motorola - and these are pretty much the full spectrum of the radios and radio network technologies that American emergency services use today.

Nimur (talk) 15:14, 9 May 2016 (UTC)

Presumably you could build a cell phone with other radios for direct communication, right? Actually isn't that already the case, as many phones these days have Wi-Fi and/or Bluetooth? Do those use the same antenna as the cell radio? I'm a programmer, and I'm fairly knowledgeable about software in general, but all that signal processing stuff is voodoo to me. Now certainly, it might not be economical to add radios to a cell phone for peer-to-peer communication. --71.110.8.102 (talk) 00:02, 10 May 2016 (UTC)

Driest place east of the Mississippi river

Which place in the United States east of the Missisippi river receives the lowest average annual rainfall? — Preceding unsigned comment added by 24.207.71.235 (talk) 23:09, 8 May 2016 (UTC)

I did some searches, and while I couldn't find any specific locale, This overview of Virginia climate notes that certain valleys of the Appalachian Mountains, such as the Shenandoah Valley and the New River Valley are noted for their lower-than-normal rainfall in the Eastern U.S. That may help you narrow down your searches. Such places lie in the rain shadow of the peaks of the Appalachian ridges, so that makes some sense. --Jayron32 23:16, 8 May 2016 (UTC)

Minnesota. Sagittarian Milky Way (talk) 05:13, 9 May 2016 (UTC)

Hard to tell from just that map. There are places east of the Mississippi in other states which are colored the same color as those parts of Minnesota which are also east of the Mississippi (which is only a small part of the state). --Jayron32 08:35, 9 May 2016 (UTC)

[31] At the river's northernmost point I draw a meridian to Canada. I've seen people draw the line due north from the source. Sagittarian Milky Way (talk) 16:47, 9 May 2016 (UTC)

Here's a better mean annual precipitation map of the USA, for the period 1961-1990, using downsampled NOAA data [32]. Looks like Northern MI has the largest area in the 25-30" bin east of the Mississippi. SemanticMantis (talk) 13:49, 9 May 2016 (UTC)

May 9

pressure enough to make "oxgen glass"?

49.135.2.215 (talk) 00:53, 9 May 2016 (UTC)Like sushi

The word "glass" or "amorphous" does not appear in our article on Solid oxygen. I'm not sure any of the solid phases of oxygen are "glass" or "glass like", can't find any reference to suggest it. Vespine (talk) 02:35, 9 May 2016 (UTC)

2 2/3 quarks for "positive hole"?

49.135.2.215 (talk) 00:54, 9 May 2016 (UTC)Like sushi

Are you talking about a pair of up quarks here? More likely for you to find is 2 up quarks, and a down quark making a proton. You would have some of these in your body. Take a read of our quark article. Particles made from quarks always appear to have integer charge. Graeme Bartlett (talk) 07:39, 9 May 2016 (UTC)

proton approaching neutron?

49.135.2.215 (talk) 00:55, 9 May 2016 (UTC)Like sushi

You haven't really asked a question here, perhaps Nuclear force helps? If not, you might need to actually form a question. If you have a hard time trying to ask a question in English, you could try asking in your native language and someone might be able to translate it for you. Vespine (talk) 04:07, 9 May 2016 (UTC)

anti-proton receeding from anti-neutron?

49.135.2.215 (talk) 00:56, 9 May 2016 (UTC)Like sushi

These two make the antideuteron. But we do not have much written on this. Strong nuclear force holds them together. Graeme Bartlett (talk) 07:31, 9 May 2016 (UTC)

Water universal soluvant as v shaped molcure?

(I will not surly be back)

49.135.2.215 (talk) 01:39, 9 May 2016 (UTC)Like sushi

Water is not a universal solvent, as many substances are not water-soluble, such as oils. (Our disambiguation page does include water, but that must be because many, but not all, substances are water soluble.) StuRat (talk) 03:24, 9 May 2016 (UTC)

Under some conditions, water becomes substantially able to dissolve non-polar things too (for various reasons depending on what conditions...Accelerated Solvent Extractor, microwave irradiation, etc). DMacks (talk) 05:24, 9 May 2016 (UTC)

...which prompted me to create the accelerated solvent extraction stub. Wasn't there a template/tag for RD discussions that led to article-space improvements? DMacks (talk) 05:51, 9 May 2016 (UTC)

{{WikiProject Reference Desk Article Collaboration}} --Jayron32 12:06, 9 May 2016 (UTC)

The molecular dipole moment of water and the v shape of the molecule are indeed an important factor in water's ability to dissolve many substances. SemanticMantis (talk) 13:45, 9 May 2016 (UTC)

Also hydrogen bonding. --Jayron32 16:32, 9 May 2016 (UTC)

Pathophysiology of hemoptysis in PE

In case of PE (or pulmonary embolism) in some of the cases one of the signs is hemoptysis. I'm trying to understand how could it happen.

Here is the blood comes the vena cava and then he's coming into the right atrium >right ventricle > pulmonary artery > alveoli capillary system and then come back to the heart through: pulmonary vein > left atrium > left ventricle and leaves the heart to the aorta etc.

My question is: if the embolism is stuck in the pulmonary artery (this is the definition of PE) how can influence on the bronchial arteries which are exploded as a result of the higher pressure of the blood there and causes to hemoptysis. here is the higher pressure is found before the embolism rather than after this point of this embolism is found. I'm trying to understand this pathophysiology unsuccessfully 93.126.95.68 (talk) 03:17, 9 May 2016 (UTC)

Pulmonary emboli often present with hemoptysis as a result of ischemic pulmonary parenchymal necrosis. (source here) --Dr Dima (talk) 06:09, 9 May 2016 (UTC) In plain English, this means that when embolism cuts off circulation to (a part of) a lung, the lung tissue startts to die. This may show up as coughing up blood. --Dr Dima (talk) 06:15, 9 May 2016 (UTC)

Thank you Dr. Dima. To be honest, I still don't understand, how can it be that there is an ischemic pulmonary parenchymal necrosis, while the lungs gets blood from the aorta (through bronchial arteries) rather than from the pulmonary artery (which is the blocked one). 93.126.95.68 (talk) 23:33, 9 May 2016 (UTC)

Our pulmonary embolism article says: "Pulmonary embolism (PE) is a blockage of an artery in the lungs...", emphasis mine. --71.110.8.102 (talk) 23:54, 9 May 2016 (UTC)

Baby growth

Asking for a friend. Do human babies grow more in the first or second year of their lives after birth? Is there a time past that when humans grow even faster? Zell Faze (talk) 20:23, 9 May 2016 (UTC)

More the first year: [33]. As far as "is there a time when they grow even faster"; as a percentage, no, but possibly in terms of most weight gained in a year, but there will be considerable variation in that, depending on gender, when growth spurts hit, if they suffer from obesity, etc. StuRat (talk) 21:05, 9 May 2016 (UTC)

Just as an anecdote, you very much notice a big difference in size between a new born baby and a one year old. IMHO there is still a considerable difference in size between a one year old and a two year old. But now my son is two, there is not such a bid difference in size between him and a three year old child. Vespine (talk) 22:37, 9 May 2016 (UTC)

A "bid difference" ? So you put him up for sale each year on his birthday ? :-) StuRat (talk) 23:22, 9 May 2016 (UTC)

"glider"? "holed shere"?

49.135.2.215 (talk) 00:38, 10 May 2016 (UTC)Like sushi

Light based lifeforms

After seeing this http://phys.org/news/2013-09-scientists-never-before-seen.html, I have wondered whether anyone has proposed the possibility of life forms that are photon-based. Has anyone hypothesized about it? — Preceding unsigned comment added by 24.207.71.235 (talk) 00:41, 10 May 2016 (UTC)

reverse triangle measurement?

(I would not be commenting, probably)

49.135.2.215 (talk) 00:43, 10 May 2016 (UTC)Like sushi