Wikipedia:Reference desk/Archives/Science/2017 November 17

= November 17 =

An odd ball [possible insect nest identification]
What is it?

It's not a wasp hive. It seems pretty solid when you break it open. It is heavy and hard. The one pictured is around 25cm high. They are all over the place in Hainan. Ants seem to like crawling around that one.

What is it?

Anna Frodesiak (talk) 06:09, 17 November 2017 (UTC)
 * COuld it be a bird nest of some sort? Swallows build nests of mud, though usually on cliff faces or under building eaves.  -- Jayron 32 11:57, 17 November 2017 (UTC)


 * The acrobat ant builds nests like this (looks similar to me). Alansplodge (talk) 12:24, 17 November 2017 (UTC)
 * Looks like an ant colony to me too. I was a bit surprised to not see any ants in the photo, but OP says ants are all around, so that's also pretty good evidence. Tropical termites can also build roughly similar nests, but I think they usually also build covered galleries. Further destructive sampling would probably clear this up rather quickly, at least to determine ant or non-ant. SemanticMantis (talk) 15:06, 17 November 2017 (UTC)
 * Just a note - it's not wise to mess with these things.  Sometimes insects swarm out and sting you to death - or if you're rock climbing you fall to your death. 82.13.208.70 (talk) 15:54, 17 November 2017 (UTC)
 * I think that's a bit melodramatic, but better safe than sorry I suppose. For the version found in the USA, "acrobat ants are usually of minimal nuisance to people" University of Florida Entomology & Nematology. Alansplodge (talk) 21:01, 17 November 2017 (UTC)

Thank you, all. I'm still perplexed. There are never openings large enough for a bird. It is nearly solid inside. No ants swarm out when disturbed. The surface is made of mostly whole leaves glued on. There are ants visible on the thing and stem below, but not that many. There are no openings where any bug comes and goes, or none easily seen. They come in all different sizes, always enveloping branches quite symmetrically. An odd ball indeed. Anna Frodesiak (talk) 22:34, 17 November 2017 (UTC)


 * Some sort of mud-dauber ant or wasp nest. Remember, ants are just a subgroup of the wasps.  See this google image search for "dauber ant nest china"'''. μηδείς (talk) 00:04, 18 November 2017 (UTC)


 * Ants, eh? That does sound possible. It's made of whole leaves so I can't see wasps carrying those. Ants could because they work as a team.


 * And careful about calling ants "just a subgroup of the wasps". They already have wing envy, and if they hear that they get very upset and start running around in different directions. :) Anna Frodesiak (talk) 05:08, 18 November 2017 (UTC)
 * Beware when they stop doing the conga and take off their tutti-frutti Carmen Miranda hats. ;) 2606:A000:4C0C:E200:C9A:4B44:2E28:1611 (talk) 05:57, 18 November 2017 (UTC)
 * Ants are generally considered party animals, and that is why the conga line is huge with them. (By "huge" I mean quite small because they're ants.) Anna Frodesiak (talk) 07:52, 18 November 2017 (UTC)
 * I would guess that this is man(women)-made "ball" (or weight?). Birds or small animals would use other materials and better locations for a nest in a wood and colony insects would not include complete leaves in their construction like in the picture. Other interesting details are that this seems to be a young tree, that it is very straight and the added info that its in China, which could be a hint towards the ancient chines art of forming plants (Bonsai etc.) for some (later) purpose. --Kharon (talk) 06:23, 18 November 2017 (UTC)
 * Not man-made, no way, impossible. They're everywhere and people would not make those things. They're too busy farming. Anna Frodesiak (talk) 07:52, 18 November 2017 (UTC)
 * Maybe they plant something in there and farm them later. You know the rich Chinese cuisine, right? --Kharon (talk) 14:08, 18 November 2017 (UTC)


 * Have you google-imaged the topic "nests"? It looks sort of like a hornets' nest. ←Baseball Bugs What's up, Doc? carrots→ 14:51, 18 November 2017 (UTC)


 * Bugs, I actually looked at the source data on Anna's photo; saw the location was Hainan, China; google imaged "dauber aunt nest china" and posted the link in my bulletted response above, so people can just click there and use the related image link if not satisfied. μηδείς (talk) 17:17, 18 November 2017 (UTC)
 * Hi μηδείς. I'm stuck with Bing here in China. And yes, the pic is from Hainan. So, Bing shows dauber wasps, but I cannot find dauber ants at search engines or at Wikipedia. I'd like to find a species at Wikipedia then add it to the disambiguation page Dauber.


 * Anyhow, every single picture of a dauber nest at search engines shows them made of stuff like hummus but not with lots of whole leaves. Seeing that the leaves in my image are the same as the living ones on the plant, they could be just bent over and hummussed rather than the leaves gathered from the floor and carried. If the latter, then it must be ants because wasps cannot carry huge leaves.


 * Next time I'm in the forest, I'll get someone to cut one open and I'll take a picture of the inside. I'll tap on it first to ensure it's abandoned. Anna Frodesiak (talk) 23:46, 18 November 2017 (UTC)


 * Well, wasps will build cells reminiscent of honeybee combs, although maybe not as well-structured. Tapping may not be enough assurance, I would put it in a sealed bag with a rag soaked in insect killer--bug spray can also be toxic to humans; follow the instructions.  You could also just go to a local university with a reasonable biology department, as they will know the genus, if not the species. μηδείς (talk) 00:02, 19 November 2017 (UTC)


 * μηδείς, thank you kindly for the suggestions. However, 1, I will not kill them, and 2, the university thing would be a dead end for a hundred hilarious reasons. :) But thank you. I'll take my chances with a knock-then-run-then-return technique. :) Anna Frodesiak (talk) 00:12, 19 November 2017 (UTC)


 * Hornets' nests come in a wide variety of styles, some of which resemble your mystery object (e.g.), but a cursory image search didn't find any that incorporated whole leaves; they tend to make their own "paper" covering from chewed fiber and saliva (the leaves on this one seem incidental). Note:  don't mess with Chinese hornets! —2606:A000:4C0C:E200:C9A:4B44:2E28:1611 (talk) 03:47, 19 November 2017 (UTC)
 * Yes, this doesn't seem to be papery. Sort of dauby with leaves.


 * And I have encountered those giant wasps. They are absolutely huge! Anna Frodesiak (talk) 04:54, 20 November 2017 (UTC)

Evolution of anticoagulants
Why did some blood-sucking animals evolve anticoagulants if they suck in a manner where the blood doesn't have enough time to coagulate? E.g. mosquitos or leeches pierce the skin and suck directly, so the blood goes steadily into them, similar to injection needle which prevents coagulation. My guess is that anticoagulants were present before they evolved the necessary organs, allowing them to feed on spilled blood. Brandmeistertalk  16:30, 17 November 2017 (UTC)
 * I'm not sure I'm following your question. Does it help to know that ordinary saliva contains enzymes like amylase and lipase that start the pre-digestion of food? In other words, ordinary saliva is already pretty decent at breaking things up. Now, something like a vampire bat has even more advanced enzymes working for it (at least, according to our citation), but it was clearly a case where evolution took something that was already good at a certain activity and then enhanced it (to some extend, a form of exaptation). Matt Deres (talk) 18:26, 17 November 2017 (UTC)
 * As I understand, digestive enzymes and anticoagulants here are different stuff. Digestive enzymes may be needed to break down blood, but anticoagulants look redundant if the sucked blood goes straight for digestion anyway. Per clotting time, blood starts to coagulate in about 8 minutes, far more time than required for a mosquito to feed and fly away. Brandmeistertalk  18:45, 17 November 2017 (UTC)
 * As usual, Matt Deres has it with exaptation. As long as a preëxisting circumstance (digestive enzymes in the saliva) provide a little benefit, and the benefits of producing stronger enzymes is possible (chemically and given the right mutations) and outweigh the costs, evolution will move in that (in this case anticoagulant) direction.
 * Or, to further address Bradnmeister, other chemicals which have anticoagulant properties may become expressed in the saliva due a change in the regulation of gene expression. (Look at the ubiquity of melanin and cholesterol-type chemicals and their various roles.)  Eventually these will be classified as different classes of chemicals.
 * μηδείς (talk) 23:49, 17 November 2017 (UTC)


 * I am concerned that there may be some unexamined and potentially incorrect assumptions here about the clotting process. Geometry matters&mdash;clotting will proceed more quickly in the very long, narrow proboscis of a mosquito compared to the relatively much wider tubes used to measure clotting time in the lab.  For instance, this presentation shows how long bleeding persists in a rat experiment where a needle is inserted and removed from the tail vein of the animal (we're interested in the control – "vehicle" – bar at the extreme left).  Even with a direct puncture of a vein, bleeding from the much narrower opening stops in less than 90 seconds&mdash;not 8 minutes.  The size of the needle wasn't obviously specified in that slide deck, but even a relatively fine 30-gauge needle still has outer and inner diameters of roughly 300 and 150 microns, respectively.  That's several times the diameter of the mosquito proboscis; see the figures in this paper.
 * There's no need to invoke exaptation or other phenomena when we already know that blood clots faster in narrow tubes. TenOfAllTrades(talk) 01:31, 18 November 2017 (UTC)
 * That last comment makes no sense to me at all. Exaptation is the use of a pre-existing element--saliva enzymes--for a new purpose; anti-coagulant.  What in the world does that have to do with probosces?  Especially since even non-proboscised vampire bats have anticoagulants.  I suspect you may have misundertood me, but I did not even mention the feeding organ in my post. μηδείς (talk) 02:04, 18 November 2017 (UTC)
 * You're right; I completely misread what you were saying about exaptation.
 * That said, there's actually another somewhat subtler misunderstanding at work here, about how mosquito saliva inhibits coagulation. The potent anticoagulant agents in the saliva of mosquitoes (and many other blood-sucking creatures, for that matter) generally aren't enzymes at all; they're polypeptides that bind to regulatory and/or active sites and act as inhibitors of pro-clotting enzymes.  That is to say, they don't inhibit clotting by digesting clots, they inhibit clotting by preventing clot formation in the first place.  There's a bit of an overview in this PNAS snippet, which looks at anophelin (we need an article...), a thrombin inhibitor in Anopheles mosquitoes.
 * Numerous animal species, from insects (mosquitoes) to mammals (vampire bats), feed primarily or exclusively on fresh blood from their prey. These parasites produce some of the most potent antagonists of the blood clotting system known, which are critical for their hematophagous lifestyle. Many of these compounds are small polypeptides that inhibit the proteolytic enzymes of the clotting cascade, notably thrombin....
 * The overwhelming majority of proteinaceous inhibitors of proteolytic enzymes works by physically blocking access of the substrate to the active site....
 * I would certainly be intrigued if someone could locate some good references regarding the evolutionary roots of these sorts of polypeptide inhibitors. Given that the anophelins have no intrinsic enzymatic activity and don't share any conspicuous sequence similarity to any enzymes (digestive or otherwise, based on a quick BLAST) I don't find the hypothesis of digestive enzyme exaptation particularly compelling.... TenOfAllTrades(talk) 03:21, 18 November 2017 (UTC)
 * I agree, I was making no actual claim that it was, say, specifically amylase that mosquito saliva developed from, but some pre-existing substance. Small polypeptides can also easily evolve from large polypeptides with a frame-shift mutation or two that deactivates all but the part of a gene that was already producing a digestive enzyme, leaving just a small polypeptide that blocks coagulation.  The step from necrophagy to sarcophagy to hemophagy seems not to have to overcome to many barriers in the evolutionary landscape. You are right, we need sources, and this (vampyrism) is not a specific field I have studied or have books on. μηδείς (talk) 03:37, 18 November 2017 (UTC)
 * Again, though, there's no particular evidence (at least none provided here) that small(ish) polypeptides like anophelin originated with any sort of digestive enzyme, given their lack of similarity with even fragments of existing, known proteases. Yes, there's lots of ways to mutate the gene for a larger protein which will result in a much smaller product, but I'm still not clear on the fixation in this thread on the idea that a digestive enzyme in particular would be the likely starting point. TenOfAllTrades(talk) 21:59, 18 November 2017 (UTC)
 * Read this sentence again (emphasis added): "I was making no actual claim that it was, say, specifically amylase that mosquito saliva developed from, but some pre-existing substance." μηδείς (talk) 22:46, 18 November 2017 (UTC)
 * I read the whole comment, actually. I even think I understood it this time.  The second sentence says (emphasis added): "Small polypeptides can also easily evolve from large polypeptides with a frame-shift mutation or two that deactivates all but the part of a gene that was already producing a digestive enzyme, leaving just a small polypeptide that blocks coagulation."  If you – or anyone – don't want me to talk about how you're talking about digestive enzymes, stop talking about digestive enzymes. TenOfAllTrades(talk) 02:02, 19 November 2017 (UTC)


 * But you are totally dropping the context that I had just said I was using it, "say", as an example of "some prexisting substance". Would I be justified in assuming that you are arguing that an entirely new polypeptide, that just happens to be expressed in the mosquito's saliva, appeared out of nowhere de novo with all the regulatory mechanisms in place to generate it and release it at the proper time?  Of course not.  So please retain the full context of what I write (notice I use paragraphs) and stop cherrypicking words when my full meaning is clear from my entire post. μηδείς (talk) 02:34, 19 November 2017 (UTC)


 * The third paragraph of Coagulation begins: “Coagulation begins almost instantly after an injury to the blood vessel has damaged the endothelium lining the vessel.” Assuming a bite damages the endothelium, that appears sufficient to answer OP’s question, but here are a few related facts and sources that may provide perspective.  From leach: “An externally attached leech will detach and fall off on its own when it is satiated on blood, which may be anywhere from 20 minutes to two hours or more.”  From Mosquito: “Universally, hematophagous arthropod saliva contains at least one anti-clotting, one anti-platelet, and one vasodilatory substance.”  The book Mosquito, by Andrew Spielman and Michael D’Antonio, pp.14,15 mentions that a mosquito will bite up to 20 times before finding a blood vessel and each time it will inject “a chemical that inhibits your body’s ability to stop any bleeding that might begin.”  (Hematophagy does not appear to directly address the question.)--Wikimedes (talk) 21:39, 18 November 2017 (UTC)


 * The most recent free paper I found on anophelin is this, which classifies it as an atypical serine protease inhibitor. The paper doesn't try to guess which (if any) it came from.  Two important things to note is that anophelin is fast-evolving even within Anopheles, creating new relevant sites in some versions absent from others, and it is a largely disordered protein, exposing those sites readily, which means that there is less stabilizing selection because one amino acid doesn't have to stay the same to contact another.  The result is that it is going to be very hard to tell which way this train went by looking at the track.  I would not presume to say it is impossible, though.  BTW the clotting enzyme (thrombin) which it inhibits is described as an atypical chymotrypsin/trypsin like enzyme, so you can say that the clotting it inhibits is an exapted digestive enzyme if you want. ;) Wnt (talk) 16:37, 20 November 2017 (UTC)

A question about g-force
How much g-force a pilot who fly an airplane at 510 knots will endure? 37.142.17.66 (talk) 18:09, 17 November 2017 (UTC)
 * If they fly straight and level, then zero.
 * They only feel g forces if they manoeuvre, usually by pulling vertically (relative to the airframe) upwards (the wings can generate more lift than any yaw or roll forces). So loops or tight turns. Andy Dingley (talk) 18:37, 17 November 2017 (UTC)
 * I'm particularly talking about United Airlines Flight 175. 37.142.17.66 (talk) 18:49, 17 November 2017 (UTC)
 * I don't recall any particularly hard manoeuvring on that day. Also these were airliners, which just aren't built to pull many g. Andy Dingley (talk) 20:06, 17 November 2017 (UTC)1;
 * I am confused. Do you mean how much G-force was generated by the abrupt stop (crash)? --Lgriot (talk) 20:08, 17 November 2017 (UTC)
 * No. before the crash. according to National Transportation Safety Board the pilot nosedived more than 15,000 feet in two and a half minutes. so how much the g-force was on the pilot, if he really fly at 510 knots? 37.142.17.66 (talk) 20:44, 17 November 2017 (UTC)
 * That is not enough information to say. G-forces are caused by acceleration, i.e. how fast the velocity is changing.   A descent of 15,000 feet in 2.5 minutes corresponds to a vertical speed component of 100 ft/s.  The question is how rapidly they transitioned from level flight to 100 ft/s descent.  If they took x seconds that would be an acceleration of &minus;100/x ft/s&sup2;, or approximately &minus;3/x gees.  If x is small, the G-force is large.  If x is large, meaning a gradual transition into descent, the G-force is small. --69.159.60.147 (talk) 21:22, 17 November 2017 (UTC)
 * It depends on how quickly the pilot noses over, and that data isn't specified here. But first, some ballparks:
 * Let's do some math (mostly trig). 510 kts is 860 feet per second. In 2.5 minutes at that speed, the plane covers 129,000 feet and, per the above, descends 15,000 feet. It's obvious even there that 15 is only a small proportional component of 129; the trig works out to a grade of 7%.
 * This Boeing publication discusses pitch rates on takeoffs and shows a nominal flight case of ~3 degrees per second of pitch rotation to a maximum 15 degree pitch. That takes five seconds and is performed on virtually every single flight. Of course, that's at a lower speed than 500 kts.
 * On the other hand, we can check out how these planes usually descend. Per the FAA, a 767-200 flies a standard climb and descent rate of 3500 feet per minute, roughly half of the 6,000 feet per minute discussed here. Assuming standard descent happens at more or less cruising speed, that's about a 4% grade.
 * The main thing to note here is that the calculated 7% grade isn't a remarkable number. There's lots of wiggle room, and for that, we go to the g-acceleration calculator for curved paths.
 * If the plane rotates at 3 degrees per second at 260 m/s (~500 kts), that's a curve of radius 5000 m (260*30 / (pi/2)) and yields -1.4 g (so -0.4 g observed). Well, that's substantial, though not debilitating. But that's making the whole pitch transition in two seconds; that's really fast.
 * 1 degree per second still accomplishes starting the descent in 7 seconds and drops the effect to -0.45 g (so 0.55 g observed). That's close to what a plane might reasonably experience on a standard flight in abnormal circumstances.
 * Go to 0.5 degrees per second (still just 15 seconds to transition into the dive) and the force from the dive is just -0.2 g (so 0.8 g observed). Totally reasonable.
 * So, absent additional evidence, there's no cause to expect that a controlled descent of 15000 feet in 150 seconds at cruising speed would impose g loads with any significant immediate consequence. &mdash; Lomn 21:43, 17 November 2017 (UTC)

[e/c]
 * Also, it depends on which axis (Gx, Gy, Gz) the G-force is applied before G-LOC occurs (unconsciousness due to hypoxia). — (Speculation) It is likely on a commercial airliner that the plane would experience a catastrophic failure (like a wing falling off) before the pilot experiences unconsciousness.  2606:A000:4C0C:E200:C9A:4B44:2E28:1611 (talk) 21:09, 17 November 2017 (UTC)
 * Direction as well as axis. A nose-over won't lead to G-LOC in the way that a pull-up will. Andy Dingley (talk) 21:55, 17 November 2017 (UTC)
 * It depends on the Pilot and what he is trying to do! Very good Pilots manage to do 1G-barrel rolls in soaring planes and Airline Pilots aim to give their Passengers a gentle pleasant journey by default so they probably try to keep the G-Forces at 1 +- 0.2 at all times except at take off, landing and emergencies of course. --Kharon (talk) 06:40, 18 November 2017 (UTC)
 * The whole point of a barrel roll (rather than an aileron roll) is that it's a low-g manoeuvre. Although neither puts many g on the pilot in the central fuselage, the forces needed to aileron roll a large aircraft will easily overload the wing spars. This is why the Boeing 707 and the Avro Vulcan were barrel rolled, not aileron rolled. Andy Dingley (talk) 20:43, 18 November 2017 (UTC)
 * My whole point of mentioning a 1G barrel roll was just to show that aviation knows some tricks to circumvent the "simple" physical logic applied here in prior answers using (2-dimensional) direction change per second formulas to calculate a (g)force. --Kharon (talk) 00:43, 19 November 2017 (UTC)
 * Is that a Very Good Pilot? I know nothing about this, but I picture some turbulence or mechanical issue putting that glass of water all over the top of the cockpit, dripping down into any electronics etc., all while he's trying to recover from a barrel roll under already pear-shaped conditions.  Is that as bad a thing as I imagine, and if so, I wonder if that is really such a bright idea.  I mean, he could have gotten more hits drawing a cartoon penis. ;) Wnt (talk) 16:26, 20 November 2017 (UTC)


 * Just to be pedantic, the pilot experiences a force of 1G downward when the plane is not accelerating. A descent of 15000 feet in 150 seconds is not accelerating even as much as a free fall. In free fall, the pilot would experience 0G. -Arch dude (talk) 07:06, 20 November 2017 (UTC)
 * G-forces on the pilot are caused by forces on the aircraft, plus gravity forces on the pilot. Oversimplifying, the aircraft experiences four forces: thrust, drag, lift, and gravity. On a commercial aircraft the strongest of these is lift (supplied by the wings), which is why a plane banks in order to turn. On a commercial aircraft, the wings will break off before the pilot has (other) troubles related to G-forces. -Arch dude (talk) 07:21, 20 November 2017 (UTC)
 * So to answer the OP's question directly, unless he was doing something unnecessary, the pilot would have experienced a force slightly less than 1G during that descent? --Lgriot (talk) 16:39, 20 November 2017 (UTC)
 * Yes. But so "slightly" that the word "endure" is wholly inappropriate.
 * Even for a suicidal terrorist trying to impact a building, there is no need to fly heavy-handedly. If they do so, there's also a risk of a large aircraft responding badly to that. Andy Dingley (talk) 16:44, 20 November 2017 (UTC)