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December 25

Condoms failing during perfect use

What causes condoms to fail during perfect use? — Preceding unsigned comment added by Uncle dan is home (talk • contribs) 04:46, 25 December 2016 (UTC)[reply]

Define "perfect". ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:07, 25 December 2016 (UTC)[reply]

Why does the OP need to define perfect? Perfect use is a standard wording for contraceptive research. It's reasonable to assume the OP is simply interested in perfect use as defined in these studies. I'm not sure if their definitions are always totally the same, but there's no reason to think the OP feels the need to limit it to one specific definition, and it's not like there's some sort of major disagreement over what's perfect use. Nil Einne (talk) 16:08, 25 December 2016 (UTC)[reply]

There's no such thing as "perfect". And your comments assume a number of facts not in evidence. StuRat raises a question below which you need to answer, as it's clear "perfect" is NOT universally understood for this product. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:17, 25 December 2016 (UTC)[reply]

What facts aren't in evidence? Nil Einne (talk) 16:21, 25 December 2016 (UTC)[reply]

"Perfect use is a standard wording for contraceptive research." Says who? "It's reasonable to assume the OP is simply interested in perfect use as defined in these studies." Says who? "It's not like there's some sort of major disagreement over what's perfect use." Prove it. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:25, 25 December 2016 (UTC)[reply]

The simplest answer is if you don't understand a question because you have zero understanding of the subject matter, it's best not to even try to answer. I suggest you give a read of Birth control and Comparison of birth control methods before you ever touch a question relating to contraception ever again. Nil Einne (talk) 16:29, 25 December 2016 (UTC)[reply]

I've been around the block a few times, and I know plenty about contraception. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:10, 25 December 2016 (UTC)[reply]

P.S. Even before my answer above, I've already proven all which you asked which I reasonably can with the references I provided below, especially [1]. I obviously cannot reasonably prove that the the OP is interested in standard terminology used throughout contraceptive research rather than some weird BB or StuRat terminology, only the OP can do that. However I continue to assert that when standard terminology is being referred to, it's reasonable to assume that it's what someone is interested in, unless they give some evidence to the contrary Nil Einne (talk) 16:33, 25 December 2016 (UTC)[reply]

P.P.S. I should also clarify I used the term contraceptive research loosely. I was intending to include research relating to barrier methods to help reduce STI transmission, since perfect use applies to both of them. Nil Einne (talk) 16:59, 25 December 2016 (UTC)[reply]

(EC)What facts aren't in evidence? And I've already answered all of StuRat's questions. And why do you keep mentioning "perfect"? As I already said, this has nothing to do with "perfect" but "perfect use" which is an incredibly standard part of contraceptive research. Whether or not it's universally understood is a moot point. The question is whether the question can be understood without further clarification and the answer to that is it can be, since there is no need for any of us to define "perfect use" as it's a standard part of the research. If you want to understand what it means, you're free to ask without demanding people define a standard part of the research. Nil Einne (talk) 16:29, 25 December 2016 (UTC)[reply]

"Used according to directions" works. "Perfect use" is an absurdity. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:56, 25 December 2016 (UTC)[reply]

Yet the fact remains, it is a standard part of research and discussions surrounding contraception and methods to reduce STI transmission during sex. Probably at least partially because saying that Coitus interruptus or Fertility awareness was "used according to directions" is weird. In any case, the main point is if you disagree with the standard terminology that's up to you, but there's no reason to ask the OP to define something which is part of the standard terminology. Nil Einne (talk) 17:12, 25 December 2016 (UTC)[reply]

BTW, another factor would likely be "who's directions"? A person following their brother or poorly informed abstinence-promoting sexual educator may be following directions surrounding condom use. But if this directions are flawed they wouldn't be regarded as having perfect use. Nil Einne (talk) 17:49, 25 December 2016 (UTC)[reply]

The directions on the package. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:07, 25 December 2016 (UTC)[reply]

Next I suppose some clown will tell us that lots of specialties' jargons include phrases that don't mean exactly what a layman might take them to mean. —Tamfang (talk) 18:39, 25 December 2016 (UTC)[reply]

Assuming adequate manufacture, friction. Ian.thomson (talk) 04:49, 25 December 2016 (UTC)[reply]

Doesn't "perfect use" include lubricants ? StuRat (talk) 14:46, 25 December 2016 (UTC)[reply]

A manufacturing defect. StuRat (talk) 14:45, 25 December 2016 (UTC)[reply]

What lubrication are you using that completely eliminates friction? (And you do realise that for many people, such a wondrous substance isn't actually desired since it somewhat defeats the purpose of sex.)

Anyway this source [2] has info on an often quoted figure of 2% failure for perfect use. It mentions only one study [3] which tried to look at perfect use. Perfect use is described as removing anyone who did not correctly follow condom usage instructions, they give an example of these specific errrors

they put the condom on after starting intercourse; did not store the condom in a cool, dry place; did not push the air out of the condom tip; used an oil-based lubricant; did not hold on to the condom ring during withdrawal when the condom was intact; or did not withdraw while the penis was still erect.

Note while avoiding oil lubrication is mentioned, no where does it mention a need to use super lubrication which completely eliminates friction. While I assume the list isn't intended to be exhaustive e.g. poking holes in the condom before use probably wouldn't be considered following instructions. But I think it's fair to assume if external lubrication was required in their instructions, such an error would likely have been mentioned. So the lack of "did not use a water-based lubricant" or "did not use a condom-friendly lubricant" anywhere suggests it wasn't.

(The actual instructions on condom use that they provided to participants aren't in the paper. I suspect it was too long and in the early days of online publishing they couldn't include it as an extra to the online version.)

Nil Einne (talk) 16:21, 25 December 2016 (UTC)[reply]

Spermicidal foam is a pretty good lubricant and it's also another layer of defense in case of breakage or misuse. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:19, 25 December 2016 (UTC)[reply]

I've made some minor changes to my comment, but it doesn't seem to matter since your comment did not relate to mine. Nil Einne (talk) 16:21, 25 December 2016 (UTC)[reply]

To clarify, I have no idea why you suddenly bring up spermicidal foam. It relates to nothing I said even before my modification, nor to anything that StuRat said, nor to anything the OP said. The OP's question related to the causes of condom failure during perfect use. StuRat claimed that lubrication would eliminate all friction and was a requirement for perfect use. I pointed out the former made no sense and later does not appear to be correct.

You keep saying "prove it" and "define this" but then make a comment which poorly worded and I'm pretty sure poorly supported. While I mentioned 2% failure rate above, I mistakenly didn't properly clarify that I was referring to contraception. (Although this could be established by reading the sources.)

However condoms are also use to reduce the risk of STIs and the OP simply referred to failure rather than why they were interested in failures. In my case it was largely a moot point (the issue was that study did not appear to require lubrication for perfect use). But in your case, it's quite important as our article mentions, spermicides may actually increase transmission of some STIs. Yet no where did you say "another layer of defense in case of breakage or misuse" only applied to certain cases.

Also as our article mentions, the use of spermicide lubricated condoms over normal condoms is not advised by a number of authorities even for contraceptive purposes. It barely address the use of additional spermicidal foam lubrication for contraceptive purposes. (It makes a weak claim "Combined methods....believed....either method alone with a 1991 ref.) But IIRC from previous research which you can probably find in the archive, the evidence is weak enough for any real benefit that few authorities suggest it for use with condoms even without STI concerns. Yes IIRC isn't the best standard, but the only reason this arises is because you suddenly brought up spermicidal lubricant and made the claim they are beneficial without evidence.

Nil Einne (talk) 16:59, 25 December 2016 (UTC)[reply]

P.S. I initially intended to address StuRat's manufacturing defects claim but later abandoned this amongst other reasons, because I was incorrectly reading StuRat's posts as combined. This is mostly the reason why I failed to clarify I was referring to contraception and also indented my post to the wrong StuRat post. Apologies again. Nil Einne (talk) 17:12, 25 December 2016 (UTC)[reply]

Okay found it there Wikipedia:Reference desk/Archives/Science/2015 February 5#causes of condom failure. It looks like I was mostly looking for evidence relating to spermicidal lubricated condoms and I didn't find much evidence. I believe, but can't be sure, I would have mentioned if I'd come across evidence that additional spermicide lubrication (as opposed to lubricated condoms) was beneficial which suggests to me I didn't. This was 2 years ago, and maybe I simply missed something. So if you have research suggesting using additional spermicide foam with condoms is beneficial for contraception (or anything else), I'm all ears. As I sort of implied there, one factor may be that the considering the possible increase in STI transmission risk and the probable? very minor benefit for contraception, it's of limited interest so little quality research. Remember per my earlier links, there's only 1 study of sufficient quality which actually looked at perfect use of condoms so it's not like this would be a unique situation. (Although it's true that perfect use generally gets far less interest than typical use.) Incidentally, t may be helpful to link to Nonoxynol-9 as it also has some info. Why you felt spermicidal foam was helpful info for this discussion, I still don't know, but whatever. Nil Einne (talk) 17:49, 25 December 2016 (UTC)[reply]

I did NOT claim that lubricants remove all friction. The lubricant doesn't need to completely eliminate friction, only bring it down to a level the material can withstand, for the designed duration. StuRat (talk) 17:49, 25 December 2016 (UTC)[reply]

But you said 'Doesn't "perfect use" include lubricants' in reply to an earlier point about friction being the cause of failures when manufacturing defects weren't involved. Unless you're claiming they will eliminate friction, this is irrelevant since friction is most likely part of the cause of failures (whether breakage or slippage), for that matter likely including many cases of defective condoms. My bigger concern is when both your posts were read in combination, this may lead to the false conclusion that manufacturing defects are the most likely cause of failures with perfect use. As far as I can tell, this isn't the case. (I did have some research for this but abandoned it partially because it wasn't as clear cut as I would like and also because as mentioned above I decided your answer was fairly ambiguous and I couldn't be bothered dealing with it.) Condoms may fail even with perfect use and without defects simply because basically sex involves friction and so this can lead to breakages and slippage. And yes this could happens with any normal lubrication used in sex. If you weren't intending to suggest that, well that's fine but there's still no explanation for your post about lubrication. Nil Einne (talk) 18:09, 25 December 2016 (UTC)[reply]

Let's compare with a car engine. Run without oil, it will break down immediately. With the proper oil (and all the other required maintenance), it should run for it's design life (say 100K miles), unless it has a manufacturing defect. None of this implies that engine oil removes all friction. Condoms are similar, in this respect. StuRat (talk) 20:39, 25 December 2016 (UTC)[reply]

Vocal type

If one's vocal range is D2-A4, what voice type is that (in both sexes)? Languagesare (talk) 10:10, 25 December 2016 (UTC)[reply]

It is really impossible to answer this question with just this data because the range is not simply determined by your highest or lowest notes, but by a multitude of factors. Ewa Podleś has a three-octave range (spanning, IIRC, from about C3 to C6), but she is a contralto, because, as she has "a range of more than three octaves, high notes like a soprano, low notes like a real alto, as well as the technique to sing coloratura" (as she puts it). Perhaps some of this thinking, which is rather common, comes from how things tend to work in most community choirs, where the bar for getting the part is very low and is just "is it within your range", even if the timbre is completely wrong. What you also need to consider is tessitura (where you are most comfortable singing) and timbre.

It's probably safe to assume you are male, because this range is practically impossible for females. That cuts things down from the usual seven we give in vocal range to the lowest three, since you can't go into the fifth octave. Beyond that, it gets impossible to cut things down further unless we know where your most comfortable range is, and in general how your voice sounds throughout all the two and a half octaves you give.

(I should note also that I am looking at it from a classical perspective, which is the only one I actually experienced. Things may be different in other genres.) Double sharp (talk) 10:34, 25 December 2016 (UTC)[reply]

Thanks for your very thorough answer. My most comfortable range is F2-F4, the low notes are strong but as I go higher it becomes childlike. Languagesare (talk) 11:54, 25 December 2016 (UTC)[reply]

The childlike tone you speak of past the break (I presume around E4 or so) suggests falsetto, so I'd be willing to bet that you're a bass, given the strength of the lowest notes, going down to F2 and a little beyond. (But please take it with a pinch of salt, because my accuracy would be impaired by not being able to hear you. If you want to know for sure, I'd suggest going to a qualified singing teacher in person.) Double sharp (talk) 12:34, 25 December 2016 (UTC)[reply]

During a lesson in a boys' school the music master asked all the boys to sing and then told them the classification of their voices. When he reached one he didn't much like he listened to him sing and then said "contralto". 86.185.150.23 (talk) 12:25, 25 December 2016 (UTC)[reply]

LOL! It's a range that never gets any respect, to be sure. Double sharp (talk) 12:34, 25 December 2016 (UTC)[reply]

Snow References

Good morning, Science Reference Desk! Good evening, for any readers who happen to be elsewhere! (As far as I'm concerned, it's going to be morning all week today)!

To enhance our encyclopedia's coverage of snow and to preemptively answer any impending questions about snow, here are a few science references that will be helpful to our regular readers:
- Six Snow Forecast Tools from the U.S. National Weather Service
- The Snow Data System from NASA Jet Propulsion Laboratory
For our regular readers who happen to be in the southern hemisphere of our planet for some reason, fear not: here are some more scientific references to help you find snow:
- Alpine Areas District Forecast, from the Bureau of Meteorology...
And for our readers who have more distant snow objectives, here is the best snow data I can find for Mars, and here are some lithographs of Enceladus and ...a slightly less scientifically-accurate lithograph of Cassini.

Nimur (talk) 14:13, 25 December 2016 (UTC)[reply]

In chemistry are there 3 states of matter or 4 or 5?

I've read in a book ("chemistry for dummies") that there are 3 states of matter: Gas,Liquid, and Solid. No mention about coloid (gel). Then is the coloid (gel) not considered as state by itself? In my school, if I'm not mistaken I learnt that the coloid is state by itself. Here in wikipedia I saw another state: plasma.so now I'm confused how many states there are in fact. 93.126.88.30 (talk) 15:57, 25 December 2016 (UTC)[reply]

See List of states of matter - which does not include colloids as those are mixtures of solid and liquid. The traditional fourth state is plasma - but modern physics has expanded the list considerably. Wymspen (talk) 16:18, 25 December 2016 (UTC)[reply]

Those are the 3 most common states of matter. There are also some truly bizarre states, like a Bose-Einstein condensate. StuRat (talk) 17:54, 25 December 2016 (UTC)[reply]

Different phases are defined using the Gibbs free energy, if going from one thermodynamic state to another there is non-analytic behavior in the Gibbs free energy, then we say that the state correspond to different phases. The idea is that all the properties of some compound in some phase can be obtained by measuring it in the neighborhood of some point. E.g. the heat capacity of water at 55 C can be determined with arbitrary accuracy by measuring it and a large enough of its derivatives at, say 10 C. These derivatives can be obtained by measuring the heat capacity in some interval around 10 C, so it boils down to making a large enough number of measurements near 10 C. And this will always work for any property (expansion coefficient, compressibility viscosity, thermal conductivity etc. etc.) for any chemical compound, as long as the measurements are taken in the same phase as the point where you want to make the prediction. This is then true by the very definition of phase. So, whenever this breaks down the phase is different, this can be because in one phase the compound is a liquid and in the other it is a gas, but there are a huge number of other phase transitions, e.g. carbon can be in graphite form or in the form of diamond. Water can be a solid in a large number of different types of ice.

In many cases the different phases can exist at the same temperatures and pressures. One phase is then metastable, in thermal equilibrium the Gibbs free energy should be a minimum so the phase with the larger Gibbs free energy is then in the metastable phase. Water slowly heated in a microwave can be heated to above the boiling point without it turning into steam. The properties of this superheated water are then what you would have obtained from extrapolating the Gibbs free energy of water below the boiling point. Similarly, if you take the Gibbs free energy of steam and extrapolate it below the boiling point, you get the Gibbs free energy of super saturated water vapor instead of water. Count Iblis (talk) 19:35, 25 December 2016 (UTC)[reply]

... but don't we need to distinguish between state, phase, mesophase and allotrope? (... not to disagree with the above, but just to avoid confusing the OP. ) Dbfirs 20:48, 25 December 2016 (UTC)[reply]

Plasmas don't come up very much in chemistry, because of the dissociation of molecular bonds in them. Double sharp (talk) 04:26, 26 December 2016 (UTC)[reply]

They actually do come up quite a number of times in industrial chemistry, for example during the synthesis of acetylene. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 07:08, 26 December 2016 (UTC)[reply]

True; I misspoke. What I meant is that while they may be useful as intermediates to produce something else, their actual chemistry is not very significant. Double sharp (talk) 12:17, 26 December 2016 (UTC)[reply]

The definition of a "state of matter" is more about language than it is about reality. Wymspen pointed you to List of states of matter. As you can see, you can categorize the more exotic "states" in several ways. Depending on your field of study, you may find it easier to think of it as "solid, liquid, gas, other", and then expand "other" by specifying the actual conditions. -Arch dude (talk) 07:16, 26 December 2016 (UTC)[reply]

The differences and the definitions of proton and neutron

It's used to say the definition of proton and neutron are that the proton is electrically charged while the neutron is not. My question is if we can put another distinction and simply say: neutron is the heavier particles of the nucleus, while the protons are the lighter particles of the nucleus (electrons are indeed the lightest but they are not in the nucleus). If that's ok, then why it's not in use? (always I see the definition about the electrical issue only) 93.126.88.30 (talk) 20:43, 25 December 2016 (UTC)[reply]

The chief distinction is the charge (combination of quarks), with the difference in mass being incidental and less important in nearly all applications. Dbfirs 20:52, 25 December 2016 (UTC)[reply]

The key thing to understand here is that a chemical element always has the same number of protons. For example, three protons make lithium, no matter how many neutrons are present - the neutrons only decide whether you have a radioactive form of lithium or not. (as in isotopes of lithium) Incidentally, that article describes a nucleus where one of the neutrons was replaced by a lambda baryon, which is much heavier...^[4] so it's not strictly speaking only two building blocks (plus gluons) available. Wnt (talk) 02:35, 26 December 2016 (UTC)[reply]

Those are hypernuclei. Indeed a few containing lambdas are known, and there have been efforts to detect others with sigmas or xis, which would presumably make a five-dimensional nuclide chart. Double sharp (talk) 03:10, 26 December 2016 (UTC)[reply]

@Double sharp: It's curious - I found myself looking up "stable hypernucleus" and found [5]/[6], but I'm far at sea there ... could empty a pistol into that paper and not a shot would get past the first page, I'm afraid. I know an unstable subatomic particle (the neutron) can be made stable in the right nucleus; is the same true of hyperons? I can think of a name for a stable lithium hypernucleus already. :) Wnt (talk) 23:11, 27 December 2016 (UTC)[reply]

From the first page of the first one: "Multistrange hadronic matter in finite systems and in bulk is predicted on general grounds to be stable, up to strangeness violating weak decays." So, there is that caveat, which has apparently not yet been investigated. Though there are nevertheless some predictions that they might be absolutely stable, as cited in your second paper. This would be very cool if not for the problem of making enough! Double sharp (talk) 03:24, 28 December 2016 (UTC)[reply]

For the chemist, the charge/non-charge is paramount. For a deeper observer, a more nuanced definition may be needed. However, if you need a more nuanced definition, you are already past the simple charge/no-charge definition, so you must think in terms of the quarks, and the mass difference is a minor consideration. -Arch dude (talk) 06:59, 26 December 2016 (UTC)[reply]

I think these answers are missing the point. By asking about definitions, the original poster seems to think that by "proton" we might mean any positively charged particle found in the nucleus, and it just happens that there is only one particle like that. Rather, we have observed that there is a certain kind of particle that is found in the nucleus, and it has certain properties of charge, mass, and being made of a certain combination of quarks. We have named this particle the "proton". In doing this we aren't focusing on any one property of it; we're assigning a name to the particle with the whole combination of properties. (And similarly for "neutron", of course.) --69.159.60.210 (talk) 10:23, 26 December 2016 (UTC)[reply]

The two major differences between neutrons and protons is their mass, and that free neutrons (not bound in a stable nucleus) decay with a halflife of about 15 minutes, while protons are believed to be stable. If they decay, the halflife of proton decay must be on scales dwarfing the current age of the universe.

Free neutron decay results in the production of a proton (that is, one of the neutron's quarks changes nature), an electron, conserving the charge, an antineutrino, and in some cases a gamma ray. See the linked article for details.

μηδείς (talk) 23:55, 26 December 2016 (UTC)[reply]

Yes, to enlarge on the OP's viewpoint - afaiu he is right to think that electric charge is not always the most salient thing for all purposes. Thinking of the proton & neutron as nucleons bound by the Nuclear force as he does was the historical route of people like Hideki Yukawa, and as Nuclear force says, "The nuclear force is nearly independent of whether the nucleons are neutrons or protons." Also: "This property is called charge independence." - a welcome case of sensible terminology.:-) John Z (talk) 03:23, 27 December 2016 (UTC)[reply]

December 26

stupid NMR question

It is easy for me to think I understand proton nuclear magnetic resonance. Yet when it gets down to the nitty-gritty of just why J-coupling works as it does... I realize that my thoughts are not in order. Specifically...

I understand that alcoholic (-OH) protons and other rapidly exchanging protons are in rapid equilibrium with other molecules in solution, and that a "D2O shake" can remove them from the NMR. But what prevents them from coupling with nearby protons? I have the impression that at least old fashioned NMR worked with a continuous wave where the spin flips of protons in a large population of molecules were measured without any sort of special pulse and decay regime at all. And I would tend to assume that an individual radio photon strikes a molecule instantaneously, taking a snapshot that should vary depending on whether nearby hydrogens are flipped one way or the other, shielding or deshielding. So the more I think of it, the more I'm not getting why spin-spin splitting doesn't affect those positions. Where am I going astray?

The other thing that is confusing me is when NMR coupling works through multiple bonds - sometimes as many as four in conjugated dienes. What exactly is pushing on what, that allows a nucleus with a certain spin at one end to affect the stability of a nucleus at the other?

I know there are other sophisticated NMR strategies that work from nucleus to nucleus. I still don't really understand though what the key differences are that determine when the relevant path is as a crow flies vs. along the bonds.

Wnt (talk) 02:58, 26 December 2016 (UTC)[reply]

boat that can "fly" underwater like a penguin

Hi! When penguins swim underwater it looks a bit like they are flying. As a kid I wanted to have or build a submarine that uses a similar technique. Does something like that exist? Basically a seabreacher with wings. (((The Quixotic Potato))) (talk) 10:32, 26 December 2016 (UTC)[reply]

More like an aeroplane than an penguin, but the DeepFlight Challenger and Necker Nymph is/was positive buoyancy submersible crafts using hydrodynamic forces to descend. WegianWarrior (talk) 10:51, 26 December 2016 (UTC)[reply]

It is not an effecive principle for flying or swimming machines or vehicles (planes, drones, submarines) to use wings for propulsion. While is is an obviously implemented near perfection methode used in nature in many forms, see Tradeoffs_for_locomotion_in_air_and_water#Hydrodynamic_principles, the only methode really established in technology is gliding. In air this is well established by the principle of Lift (soaring)-planes and in water only by drones that use buoyancy-based propulsion, tho in that case it is very slow. So the answer is no and it wont work well until engeneering manages to build something as usable, fuleable, effective and capable as nature achieved by "inventing" the Muscle. --Kharon (talk) 16:04, 26 December 2016 (UTC)[reply]

The muscle doesn't exist that even comes close to the size, strength, speed, or efficiency of hydraulics/pneumatic actuators. The reason that flapping wings are not used by aircraft or watercraft is that rotary motion, which is (mostly) not available to organisms (but see Rotating locomotion in living systems), is generally more efficient than flapping motion. --Guy Macon (talk) 22:23, 26 December 2016 (UTC)[reply]

The octopus, for example, uses jet propulsion, which would seem to be superior to flapping of wings underwater. But even so, as you say, machinery easily beats them all. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:22, 27 December 2016 (UTC)[reply]

@Guy Macon. It seems you dont understand the challenge of an technological implementation. Even some electrical actuator that is build with High-temperature superconductors that get close to 99% efficiency, with whatever you pick in materials and engineering as mechanics and whatever energy source you add, with no budget limitations, you will not beat nature in efficiency un the end. Dolphins are capable to exeed speeds of 35 knots underwater without the need of a nuclear reactor, a rocket engine or alike. They eat 50 fish and travel 35 knots for one week on that. Technological implementation is not about single parts, like "your" efficient actuators, but the working concept you can build and its versatility in reality. --Kharon (talk) 04:36, 27 December 2016 (UTC)[reply]

Oh great, nutcase time. OK, I was mechanical engineer in charge of the design of a motor that was measured at 98.4% efficiency. No superconductors, no magic. You can even buy them in kit form for about $1500 for powering solar cars. How big are these 50 fish that a dolphin can travel at 35 knots for one week, ie about 7000 km? The main reason that wing-like propulsors aren't used is that screws are quite efficient (80% is not atypical) and very easy to drive mechanically. Wings require complexities in their drive that are not justified by any increase in performance, if there is one. Greglocock (talk) 08:00, 27 December 2016 (UTC)[reply]

I prefer the phrase "factually challenged". Muscles top out at about 30% efficiency. See Muscle#Efficiency. Atlantic bottlenose dolphins in an ambient seawater pen eat about 100,000 kcal/week.[7] On average an adult dolphin will eat four to nine percent of its body weight in fish daily, so a 550 lb dolphin will eat 22 to 50 pounds of fish per day.[8] Yes a dolphin can cover long distances running off of stored body fat, just as my car can cover long distances on a full tank of gas, but that says nothing about fuel efficiency. And by the way, we were building machines that could travel underwater faster than any dolphin back in WWII -- no superconductors required. Nowadays we can go a lot faster. See Underwater speed record. --Guy Macon (talk) 08:31, 27 December 2016 (UTC)[reply]

FWIW:[9][10] Wnt (talk) 12:24, 27 December 2016 (UTC)[reply]

In those cases, stealth would be the overriding factor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:55, 27 December 2016 (UTC)[reply]

Does anybody know what flying fish do with their large pectoral fins when they are underwater. Are they used in propulsion which would link to the OP, or perhaps they keep them folded against the body for streamlining? DrChrissy ^(talk) 20:17, 27 December 2016 (UTC)[reply]

Not a flying fish, but "We examine underwater flight in the spotted ratfish (Hydrolagus colliei) to test the model. This animal relies entirely on flapping its large, flexible pectoral fins for routine locomotion"[11] DrChrissy ^(talk) 21:29, 27 December 2016 (UTC)[reply]

@DrChrissy: Here's [12] a video showing a flying fish using a few flaps for low-speed maneuvering in shallow water. I don't think they use the wings much to flap while swimming at speed. Here [13] you can see them taking off, and in the first few seconds it's pretty clear the wings are held flat against the body during the high-speed thrust phase just prior to launch.

Here [14] is a very nice review article of swimming modes, with an eye toward energetics and engineering. Figs. 14,15, and associated refs will be interesting to User:The Quixotic Potato. The key term for this "swimming like flying with 'wings' is labriform swimming, that should help future searches, here's a few top hits in the academic literature [15] [16]. Here's another paper specifically about the energetics of penguins and ducks that use wings under water [17]. While most dabbling ducks keep their wings folded while under water, many diving ducks use their wings to fly downward more rapidly, example here [18]. SemanticMantis (talk) 21:24, 28 December 2016 (UTC)[reply]

Thanks so much for this. Wonderful references and videos. (some WP articles clearly need this information) In the video about the diving ducks, I loved that they use their wings to dive, but kept them tucked in when rising to the surface. Presumably they can rise quicker by remaining stream-lined. By the way, in my research for this question, I read somewhere that flying fish tuck their pectoral wings in both before exiting and re-entering the water. I imagine this is due to the risk of injury. DrChrissy ^(talk) 21:44, 28 December 2016 (UTC)[reply]

OP here, thank you all. This is why I love Wikipedia. I wish I would've had access to Wikipedia as a seven year old, but it didn't exist back then (and I didn't even have internet access). Very interesting stuff, I'll spend a couple of days reading everything and everything that those pages link to. I have to admit that my seven year old self didn't really care about fuel efficiency. DrChrissy's question also made me curious. (((The Quixotic Potato))) (talk) 06:07, 28 December 2016 (UTC)[reply]

Deposit of fog droplets vs. fog drip

The original definition by the WMO of deposit of fog droplets was: "deposit of non-supercooled fog or cloud droplets on objects the surface temperature of which is above 0°C. Observed especially in mountainous areas where orographic clouds are frequent. The intensity of the deposit depends on the duration and granulometry of the fog (or clouds) and on the speed of impact of the droplets. It is also a function of the wettability and interception coefficient of objects (paticularly high for conifer needles). When this phenomenon is high, the droplets can run together and drip on to the ground. In some cases the amount of water falling from branches during a single night could be the equivalent of a moderate rainfall" (International Cloud Atlas vol.1, 1975, p. 115 – some words and phrases were changed by me for copyright issues). Although this definition may be similar to fog drip, it seems also to include the moist deposit of fog droplets on the ground falling directly from the fog itself. The new definition that can be read in this draft seems to include only fog drip from clouds. I would like to know why moisture from the fog itself it is not often considered in those definitions.--Carnby (talk) 11:26, 26 December 2016 (UTC)[reply]

information on a french reflecting circle by lorieux, lepetit

Hello, I would like any information regarding a french reflecting circle by lorieux, lepetit. Any help would be greatly appreciated. Thank you in advance. — Preceding unsigned comment added by Anthony Sura (talk • contribs) 12:21, 26 December 2016 (UTC)[reply]

Have you seen Reflecting instrument#Reflecting circle? Looie496 (talk) 14:39, 26 December 2016 (UTC)[reply]

See FRENCH REFLECTING CIRCLE by "LORIEUX, LEPETIT N° 254". Blooteuth (talk) 23:39, 26 December 2016 (UTC)[reply]

Are the waves of the ECG created before the real contraction of the heart?

Normally medical staff (according to what some of them told me) are said that the depolarization waves of the ECG represent the contraction of the heart, but I've read in the past that the ECG waves of depolarization happens in fact before the contraction, but because it happens in milliseconds then it's negligible and nobody talks about it. Is that true? I'd like to see any source which support it (Unfortunately I don't find the place that I've read it) 93.126.88.30 (talk) 17:49, 26 December 2016 (UTC)[reply]

It might (or might not) help to look at our cardiac action potential article. As you can see in the diagram I've inserted, a typical action potential in a heart muscle cell has a very fast onset and then a long sustained phase. The QRS complex in the ECG reflects the onset, but contraction occurs throughout the long sustained phase. However without that fast onset the contraction would not be coordinated properly. I don't quite understand what you mean by "it's negligible and nobody talks about it". What does "it" refer to there? Looie496 (talk) 18:05, 26 December 2016 (UTC)[reply]

I think the OP is using "it" to mean the delay between the recorded electrical activity and the muscle activity. DrChrissy ^(talk) 20:13, 26 December 2016 (UTC) [reply]

The ECG picks up the electrical activity of the heart muscle itself, since there is so much of it, rather than any regulatory nerve (and indeed, the heart can beat without innervation). So when the ECG picks something up, the heart muscle cells are actually "contracting" in the sense of a physiological activity. To get to contracting in terms of physics, the route is slightly longer: the action potential allows the Ryanodine receptor 2 to join in bringing calcium to the cytoplasm, and that calcium interacts with troponin C, which is in a complex with myosin. And only after the myosin is allowed to act do the heart cells actually start getting shorter, which of course takes some time. Still, for not particularly surprising reasons, I'd hazard, this is one of the shorter and more foolproof examples of signal transduction that I can think of. Wnt (talk) 19:56, 26 December 2016 (UTC)[reply]

Determine whether caulk is silicone or acrylic?

Is there an easy way to determine whether a sealant caulk used around a window frame is silicone or acrylic? I want to use a remover but it's more troublesome to get an acrylic one so I'd like to figure out what will work in advance. Picture in case that makes a difference --79.69.193.153 (talk) 21:50, 26 December 2016 (UTC)[reply]

Do you have isopropyl alcohol? It is absorbed by acrylic caulk and softens it, making it easier to remove mechanically. I believe (but have not personally tested) that silicone caulk laughs at your puny isopropyl alcohol. --Guy Macon (talk) 22:29, 26 December 2016 (UTC)[reply]

Yes I do, that's perfect! Thanks! 79.69.193.153 (talk) 15:39, 27 December 2016 (UTC)[reply]

December 27

Distance to stars

I was surprised to learn that the distance to stars is not known very accurately. For instance, the distance given for Betelgeuse is +/- 22%. That seems like quite a bit of uncertainty for something so close. Is it errors in measuring the parallax? Bubba73 ^{You talkin' to me?} 05:29, 27 December 2016 (UTC)[reply]

The problem is that except for either very close stars, where the parallax can be well-measured, or for certain types of stars like Cepheid variables with unusually uniform brightness characteristics, we have to guess based on an unsure distance and an unsure luminosity. When measuring parallax, we've got at best 15 or so light minutes as a baseline to guess an angle where the other legs of the triangle may be hundreds of light years or more. Betelgeuse's luminosity is highly variable, and its size is also uncertain as the article will explain, so it's a tough case. μηδείς (talk) 05:47, 27 December 2016 (UTC)[reply]

Cosmic distance ladder explains how the distances of astronomical objects are determined. The pre-Gaia parallax of something that far is crap. That spacecraft will greatly increase the distance of 1% error, 10% error etc. and measure parallaxes a large fraction of the way across the galaxy except Betelgeuse is far too bright to be measured I think. Sagittarian Milky Way (talk) 06:02, 27 December 2016 (UTC)[reply]

That helps a lot. Bubba73 ^{You talkin' to me?} 06:37, 27 December 2016 (UTC)[reply]

Resolved

Lithium-ion batteries in smartphones emit more than 100 toxic gases

I have experienced this

http://www.ibtimes.co.uk/lithium-ion-batteries-smartphones-emit-more-100-toxic-gases-say-researchers-1587570

Which smartphones don't emit such toxic gases? 42.110.158.213 (talk) 11:16, 27 December 2016 (UTC)[reply]

" the gases emitted when a range of commercial lithium-ion batteries are heated to the point of combustion. "

So don't set fire to your phone battery.

"Toxicity, a serious concern of thermal runaway from commercial Li-ion battery". Nano Energy. 27. 2016. doi:10.1016/j.nanoen.2016.06.031. {{cite journal}}: Unknown parameter |authors= ignored (help) Andy Dingley (talk) 11:39, 27 December 2016 (UTC)[reply]

None.

Rant time. That question, which merely reflects the general tone of the article (which itself is the most exaggerated yet true version that the quoted scientists could approve, following the recipe of [19]), is loaded.

Any material of any kind that is present in the universe will contain traces of almost any other physically possible molecule, including a large number of "toxic" components. Most often, it will contain "toxic" components at detectable levels - for instance, tap water regulations allow for arsenic at detectable concentrations, not because the lobby of water distribution is out to poison our children, but because there is a mountain of scientific studies studying the dose–response relationship for arsenic and saying it basically has no effect below this threshold. (Nonetheless, the water lobby or cost-cutting politicians may still come afterwards to make sure regulations aren't properly enforced though.)

The real question, in a context of health and safety, is whether the emanations from the cell phone cause measurable health trouble under various realistic scenarii. If you have access to the original article to which AD linked above, you could see the concentrations they measure and compare with epidemiological studies - my guess is that the toxic gases will be well below the threshold at which a health effect is demonstrated - if it wasn't, it would have made headlines in the scientific press. Tigraan^{Click here to contact me} 21:01, 27 December 2016 (UTC)[reply]

Meanwhile, until we are sure that emanations are below any danger limit, it would be wise not to sleep with your mobile phone right under your nose, especially if you are fast-charging it at the time, and it would be unwise to put your mobile phone on the fire, or in a hot oven, especially if you also have your head in it at the time. To answer the original question: ones which have had their batteries removed. Dbfirs 21:25, 27 December 2016 (UTC)[reply]

Rather the opposite in fact. The emanations they measure are seriously unpleasant and at high concentrations. However they're not released in normal service. A valid paper is wholly misrepresented by the IBT article - which is fairly typical for the IBT. Andy Dingley (talk) 21:49, 27 December 2016 (UTC)[reply]

Yeah I'm not sure why Tigraan doubts that a combusting battery may release gases in concentrations sufficient to be harmful since plenty of products will do so. Nil Einne (talk) 23:35, 27 December 2016 (UTC)[reply]

I somehow missed the bit about setting the batteries on fire in the article's abstract. But even then, my main point stands - it's a game of numbers. Either you can go through the paywall and start discussing the values that lie behind, or you are bound to speculate one way or the other. Sure, I will grant you that it is more than plausible that fumes from a burning battery are toxic, but to prove it you need the numbers. Tigraan^{Click here to contact me} 16:48, 28 December 2016 (UTC)[reply]

Read the article, via the doi link above. It's not paywalled (or else I've bulk-paid Elsevier somehow and didn't notice). Andy Dingley (talk) 20:35, 28 December 2016 (UTC)[reply]

Yeah it's not behind a paywall so I'm not sure why this was brought up. Also I'm not sure what's this fixation with the numbers. Of the four compounds quantified the authors specially noted the levels of CO were a concern. There was no commentary on the other 3. Sure it's always useful to look at they numbers yourself, but ultimately if you don't trust the authors to correctly note the risk you should question if you can even trust their measurements. Either way it isn't speculation to note the authors consider the level of CO a concern. In any case even if the main point has some limited truth too it it's largely missing the forest from the trees. The reason why you don't have to so concerned about this and it didn't make waves in the scientific press is because the results are not surprising and only a concern in a limited set of circumstances and definitely not to ordinary usage of the products. Even without these results you should be concerned if your battery combusts and not just because of what may be emitted. And yes it is silly to "guess is that the toxic gases will be well below the threshold at which a health effect is demonstrated". There's a very good chance the levels of something will be a concern if in a sufficiently closed and small space when you're combusting something as complex as a lithium ion battery and enough of them (well total capacity is a decent measure). It may still be a guess without the paper, but Tigran was the first person to make a guess even after the non paywalled paper was presented and so the obvious question is it a good guess, and the answer seems to be a clear cut no assuming a basic reading of even the flawed IBT article or the title of the paper or just what was noted here before the reply which Tigran was aware of (IE the recognition we are talking about combusting batteries) . Nil Einne (talk) 21:44, 28 December 2016 (UTC)[reply]

Traditional and Western medicines

My Chinese friend says that some Western medicines are based on TCM herbs and some Western people go to poor countries, ask the local people about local herb medicines, then steal the info to make Western medicines. Is that correct and if yes, more info and examples? --Curious Cat On Her Last Life (talk) 23:38, 27 December 2016 (UTC)[reply]

Err... yes and no. Many 'old wife’s' remedies are ridiculous. Yet not all. The Indian Government set up this site for the very reason that western pharmaceutical companies were attempting to demand royalties on traditional treatments. Will leave it to it to a quack, to explain how, that when one has a patent they go out of their way to ban the original. Willow Bark or an Aspro anyone? Oh! What a coincidence. --Aspro (talk) 00:01, 28 December 2016 (UTC)[reply]

On the topic of TCM. Artemisia annua is a very effective anti malarial, yet the ( very expensive) patented synthetic equivalent based on this herb is less so. Make your own minds up. Should one venture into a an area of 'black water fever' your quack can only prescribe a less effective treatment by the law laid down by the FDA, who purpose is to protect the healthy profits of the pharmaceutical companies. --Aspro (talk) 00:28, 28 December 2016 (UTC)[reply]

@Aspro: peddling Big Pharma conspiracy theory and your anti FDA rhetoric has no place on the ref desk. The ACT treatments are expensive because they cost more to produce (than the very cheap old Chloroquine based drugs which no longer work very well), and the FDA has nothing to do with companies in Europe selling drugs in Africa. The truth is a LOT more complicated. Many of the drugs in Artemisnin combination therapy are not patented and have generic versions, such as Artemether and Artesunate, they are just more expensive to produce. Do a bit of research and cite some relevant articles, maybe you should keep your opinions to forums like prison planet or abovetopsecret. Vespine (talk) 00:44, 29 December 2016 (UTC)[reply]

If alternative medicine (e.g. TCM) works it becomes medicine. (((The Quixotic Potato))) (talk) 06:17, 28 December 2016 (UTC)[reply]

We don't seem to have an article about this phenomenon, but yes, it exists. One case is Hoodia, a plant known to the Bushmen (San) people of southern Africa as an appetite suppressor. The pharmaceutical industry found out about this potential treatment for obesity, and a generation later, the plant is under threat of extinction, the Bushmen are as poor as ever, and the isolated component is apparently too toxic to be usable. You may find other examples with better outcomes by browsing Category:Medicinal plants by tradition. Carbon Caryatid (talk) 11:24, 28 December 2016 (UTC)[reply]

Nota bene: "the genus became internationally known and threatened by collectors, after a marketing campaign falsely claiming that it was an appetite suppressant for weight loss". And of course the San people are not Chinese. At least 99% of TCM is BS. (((The Quixotic Potato))) (talk) 11:27, 28 December 2016 (UTC)[reply]

Indeed. I was responding to the query about "some Western people go[ing] to poor countries". I understand that 99% ^{[citation needed]} of drug candidates are found not to be usable, for one reason or another. Carbon Caryatid (talk) 11:54, 28 December 2016 (UTC)[reply]

By the way, the general field is called ethnobotany, which our article defines as "the study of a region's plants and their practical uses through the traditional knowledge of a local culture and people^[1] <snip> including, but not limited to, plants as medicines, foods, and clothing.^[2] ".Carbon Caryatid (talk) 11:58, 28 December 2016 (UTC)[reply]

The specific allegation is "biopiracy", but that is a very broad political term applied to benefit very specific people. The 'fix' generally involves privatizing the public domain, but they say it's for a good cause. (The Hoodia article cited above is a good example: someone claims a patent on something well known for centuries, and the fix is to share the profits with the tribe!) Ahem. I think that capitalism has become more of a religion than a workable scheme for organizing an economy at this point, and this is one example of that. There are a great many TCM treatments that are effective - most notably, the Chinese take flack for raising bile bears whose gall contains ursodeoxycholic acid (which now can be synthesized), while in the West they are more happy to simply take out your gallbladder and leave you with digestive problems instead. "Ethics" is just another word for profit. Wnt (talk) 16:29, 28 December 2016 (UTC)[reply]

References

Biopiracy, thank you, I had forgotten the term. I see that they take hoodia as a key example. Carbon Caryatid (talk) 17:33, 28 December 2016 (UTC)[reply]

December 28

Confusing pubmed article: "skin defect of hell"

Was not sure whether to ask this in reference desk language, but would anyone know what this surgery abstract in pubmed would refer to by the term "skin defect of hell" https://www.ncbi.nlm.nih.gov/pubmed/12078310 ? — Preceding unsigned comment added by 2604:2000:7011:5C00:91A0:39FC:5873:5B0E (talk) 12:08, 28 December 2016 (UTC)[reply]

Ehm, yeah. "Hell" should probably be "heel". I googled "skin defect of hell" -"Surgical intervention in the treatment of skin defect of hell". I found http://www.rrsurg.com/article/zgxfcjwkzz/2000/4/232 and then I put the Chinese text in Google translate and it said: "Perioperative Management of Primary Repair of Skin Defect in Heel". (((The Quixotic Potato))) (talk) 12:16, 28 December 2016 (UTC)[reply]

I do not understand Chinese but Google Translate tells me that 足跟部皮肤缺损 means Heel skin defect (足跟 means heel). I have used the contact form to make them aware of the situation, maybe they'll fix the typo at some point in the future. (((The Quixotic Potato))) (talk) 12:18, 28 December 2016 (UTC)[reply]

(short-term) Death Toll from catastrophic Dam failure?

Does anyone have (short-term) death toll estimates from the catastrophic failures of the Aswan Dam and the Three Gorges Dam? Note, I'm looking for short term, those directly caused by flooding and building collapse as opposed to those from disease such as cholera, typhoid, etc. or dehydration due to lack of clean water. If possible, I'd like to additionally get information for any Dam whose short-term expected death toll is greater than these two (I doubt there are, but I'd like to be sure) *and* the one with the highest death toll in the United States. (Most of the dams in the US Southwest on the Colorado don't have *large* cities downstream (Yuma, Arizona isn't large by these standards)). If this belongs in RD:Misc, let me know.Naraht (talk) 14:32, 28 December 2016 (UTC)[reply]

Why isn't alcohol used to treat bacterial skin infections?

So alcohol kills 99.999% of bacterial within 15 seconds. Why isn't it used to treat bacterial skin infections instead of antibiotics? — Preceding unsigned comment added by 177.37.160.211 (talk) 16:40, 28 December 2016 (UTC)[reply]

Because skin infections are not usually on the surface of the skin - and if the patient either took the alcohol by mouth, or had it injected, it would be very quickly metabolised. Using alcohol swabs to clean the surface of a wound has a long tradition - but it is only effective on the surface. Wymspen (talk) 18:43, 28 December 2016 (UTC)[reply]

That figure is very optimistic, I think. But the main point there is that if the bacteria are not in you then it doesn't take much of a magic bullet to kill them. You could probably wash with soap or wave your hand over a Bunsen burner and kill/remove a lot of bacteria also. But in between live cells, your body can't have 70% ethanol, no more than it could put up with Bunsen burner temperatures or dish soap. It would be like trying to fight terrorist infiltrators with nuclear weapons! Wnt (talk) 18:51, 28 December 2016 (UTC)[reply]

If it's not causing disease, a bacterium on your skin is a colonization, not an infection. You don't want to kill them all; you only want to kill the ones likely to cause infection. The other ones - by being present - can help prevent the potentially pathogenic ones from predominating and causing other problems. In other words, the skin has a "normal flora" - bacteria that are supposed to be there - the absence of which can cause problems. - Nunh-huh 18:57, 28 December 2016 (UTC)[reply]

All true, but the OP's premise was the case of an infection. Although many antibiotics have some specificity, for example targeting Gram-positive cell walls, there are not many things, apart from a few drugs against weird bacteria like isoniazid, or phage therapy, that really go after the bad actors and leave the bacterial bystanders alone. Wnt (talk) 21:25, 28 December 2016 (UTC)[reply]

Artificial intelligence

Many sci-fi films depict scenarios in which humans are outsmarted by artificial intelligence but is this actually a possibility in reality? 2A02:C7D:B937:6300:B46E:5B0E:8B82:3412 (talk) 21:13, 28 December 2016 (UTC)[reply]

It is not possible at the moment. It might become possible in the future. Stephen Hawking is certainly concerned about that possibility - http://www.bbc.co.uk/news/technology-30290540 Wymspen (talk) 21:24, 28 December 2016 (UTC)[reply]

How about a nice depressing match of Computer chess? Really, we'll set it low, you might have a chance. Wnt (talk) 21:26, 28 December 2016 (UTC)[reply]

This has some merit. My garden-variety PC outsmarts me with alarming frequency, so AI can be said to be able to outsmart a human in tasks for which some higher level of cognition isn't required, but just an extreme ability to assess possibilities (i.e. a chess match in which a computer can just map out possible near-term positions based on the board's setup). Tyrol5 [Talk] 00:34, 29 December 2016 (UTC)[reply]

History of artificial intelligence and Philosophy of artificial intelligence are two nice long articles with good references. Then there's Artificial_intelligence. See also Weak AI, Hard AI, and AI-complete. As Wnt alludes, computers are already better than us at chess. And now even playing go. And all kinds of other things; machine learning is now entering a phase where any kid with some coding skills can jump in and make computers do crazy "smart" things [20]. But these are generally seen as "soft" or "narrow" forms of AI, and we don't have anything yet that we think can truly think. It gets hard to talk about. Intelligence itself is hard to define, and can mean many rather different things. Hard problem of consciousness outlines some of the thoughts we've had about thoughts and consciousness. SemanticMantis (talk) 21:55, 28 December 2016 (UTC)[reply]

Two very thoughtful web sites on the question of AIs taking over:

I highly recommend both. --Guy Macon (talk) 23:57, 28 December 2016 (UTC)[reply]

Not quite as good as the above two, but still quite interesting: https://www.explainxkcd.com/wiki/index.php/1002:_Game_AIs --Guy Macon (talk) 00:13, 29 December 2016 (UTC)[reply]

December 29

Commercially-canned mushrooms

There's something different about commercially-canned button mushrooms, compared to fresh ones. Fresh mushrooms are soft. When you break them, they break along the grain of the fibers. Canned mushrooms, on the other hand, are firm, and have a seemingly "isotropically uniform" texture. What kind of processing and/or added ingredients are responsible for the firmness and texture of canned mushrooms? --100.34.204.4 (talk) 02:32, 29 December 2016 (UTC)[reply]

[1] USDA definition of Ethnobotany

[2] Biocylopedia: Ethnobotany

[1]

[2]