Wikipedia:Reference desk/Archives/Science/2010 August 15

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August 15

House

I watched an episode of house (the one with the Death Row guy, 2x1 maybe?). House explains that getting the patient drunk was a treatment for the patient trying to kill himself by drinking methanol because the ethanol in liquor "bonds" with and neturalises the methanol and both just get p***ed out. I only have high school chemistry but I didn't get this part. What bonding? How can ethanol and methanol bond? 76.228.198.120 (talk) 01:24, 15 August 2010 (UTC)

See Ethanol#Antidote for methanol poisoning. The same enzyme (alcohol dehydrogenase) is responsible for breaking down both ethanol and methanol; if most of those enzyme molecules are tied up with metabolism of ethanol, then you suppress the generation of toxic products of methanol metabolism. It sounds like the phrasing from the episode was sloppy, but not totally out there. TenOfAllTrades(talk) 01:34, 15 August 2010 (UTC)

How is Hyponatremia (low sodium) diagnosed ?

How is "Hyponatremia" (low sodium) diagnosed in humans & animals ? After reading several related articles from Wikipedia, I have not been able to specifically determind how this condition is detected. Some of the articles talk about low sodium in the blood, so I am suspecting that a blood test must be taken for analysis, but I am not sure. Lindaeaton (talk) 05:28, 15 August 2010 (UTC)

I would just offer them some salt with their meal and see if they use it. -JK 92.230.64.158 (talk) 07:35, 15 August 2010 (UTC)

How exactly would that tell you if they had hyponatremia? It may be just that they don't like adding salt to whatever it is they are eating, perhaps it's already salty enough for them. I myself rarely add salt to a meal, although do use it when cooking (along with soya sauce) sparingly sometimes, but highly doubt I have hyponatremia as I eat plenty of chips and other likely salty processed foods. Of course it could even be that their doctor told them to restrict their sodium intake or perhaps they aware that they have a high sodium intake, so are trying to restrict it where possible. Nil Einne (talk) 10:16, 15 August 2010 (UTC)

You might find this link interesting. [1] Regards, --—Cyclonenim | Chat  08:11, 15 August 2010 (UTC)

The Basic metabolic panel battery of blood tests include tests for both sodium and chloride ions and can therefore diagnose both hypo- and hypernatremia. This test (also known as "CHEM-7" can be performed by a small machine - not much bigger than a laptop computer - which (as far as I can ascertain) uses photometric techniques - probably absorption spectrometry. The results are printed automatically by the machine and compared against 'normal' ranges. SteveBaker (talk) 14:34, 15 August 2010 (UTC)

is there soap in stevia?

see this

http://www.youtube.com/watch?v=-1hPIPZ-0DI&playnext=1&videos=o6oGd7iMGtU

"even distilled water gets the soap when you blend it with stevia. test it in the lab.

if you disagree, i have chemistry labs in las vegas willing to testify to this." —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 14:31, 15 August 2010 (UTC)

I would be very very skeptical of information of a claimed scientific nature found on YouTube. There are (by far) more faked videos than real ones. If this is real - you will be able to Google for it and get more details. I recommend our stevia article. SteveBaker (talk) 14:36, 15 August 2010 (UTC)

I have to agree. If there are 'chemistry labs in LV willing to testify to it' then it should be documented somewhere. And I would trust someone who provides me sources to look up rather then allege chemistry labs are willing to testify to it Nil Einne (talk) 19:31, 15 August 2010 (UTC)

this guy has made hundreds of vids on stevia his name is dan quinn —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 15:35, 15 August 2010 (UTC)

I clicked the video, but he was talking about something that "we've been dumping down our sinks for the last 80 years" - presumably not stevia. I have no idea what he's on about. Generally, there are many emulsifiers present in natural foods. Wnt (talk) 16:50, 15 August 2010 (UTC)

In fact I only see 11 videos in his Youtube profile, none of them seem to be about stevia. Dan Quinn (fighter) doesn't exactly inspire confidence you should trust him in science matters but does suggest he likes stevia so concurs that he isn't talking about stevia in the video. Nil Einne (talk) 19:42, 15 August 2010 (UTC)

In case anyone is confused, the article has now been drasticly cut down when I noticed how problematic it is and mentioned it at WP:BLP/N Nil Einne (talk) 12:02, 16 August 2010 (UTC)

Top human sprinting speed

What's the top instantaneous speed ever achieved in a track and field event? I'm thinking, of course, of Usain Bolt's latest world record. --Belchman (talk) 15:00, 15 August 2010 (UTC)

The first reference in our 100 meters article gives 10m split times for several races. In a 2008 race, Bolt ran 10m in 0.82 seconds which is 12.2m/s or 27.3 mph. CS Miller (talk) 16:37, 15 August 2010 (UTC)

Thanks, but that split is not from his current world record (set in 2009, in Berlin). --Belchman (talk) 18:34, 15 August 2010 (UTC)

The official IAAF split times [2] from a quick search for 'usain bolt split'. As I expected, there's no real difference, he achieved 0.81 or 12.35m/s. The big gain was because he didn't celebrate at the end as he somewhat controversial did in Beijing. He may have achieved a nominally higher split in the 200m race of perhaps the 100m relay of course. And the actual highest instantenous speed would have been higher then that, you could try some sort of frame by frame video analysis, trying to determine the speed between frames but at that level you run into complicating things like how you decide distance travelled and how accurate the time between frames is. Nil Einne (talk) 19:08, 15 August 2010 (UTC)

Thank you. --Belchman (talk) 21:08, 15 August 2010 (UTC)

As an addendum, I found [3] in the comments to the earlier discussed ref which gives a slightly lower split time of 0.805. Nil Einne (talk) 15:01, 16 August 2010 (UTC)

Let's look at world record times over various standard distances:

• 50 meters 5.56 seconds (8.99 meters/sec),
• 60 meters 6.39 seconds (9.39 meters/sec),
• 91.44 meters 9.09 seconds (10.06 meters/sec) -- 100 yard dash,
• 100 meters 9.58 seconds (10.44 meters/sec),
• 150 meters 14.35 seconds (10.45 meters/sec),
• 200 meters 19.19 seconds (10.45 meters/sec),
• 300 meters 30.85 seconds (9.72 meters/sec),
• 400 meters 43.18 seconds (9.26 meters/sec).

Since the average speed over 100, 150 and 200 meters are very nearly the same - but over 50, 60, 91, 300 and 400 meters, they are significantly slower, we can clearly see that the distance required to accelerate to top speed must be more than 60 to 90 meters but less than 100 meters - and stamina issues don't seem to kick in until distances over 200 meters but less than 300 meters. That says that the average speeds for the 100, 150 and 200 meter events must be pretty close to the peak speed that anyone can run - and the acceleration time is pretty negligable. So my best guess would be around 10.45 meters per second.

SteveBaker (talk) 02:04, 16 August 2010 (UTC)

Wait a sec, maybe you meant something different, but do these numbers really show that top speed is reached above 60 to 90 meters? They do show that top average speeds are achieved at distances between 100 and 200 m, but all these averages include the slow first meters. At what point do the fastest sprinters actually reach top speed? ---Sluzzelin talk 02:24, 16 August 2010 (UTC)

But that's the point. If they reached their peak speed at (say) 150 meters - then you'd expect faster average times over 150 meters than over 100 meters - especially since the effects of the acceleration time are less important over longer distances...but you don't see that. These runners can cover 100m, 150m and 200m at almost the exact same average speed. It's weird...but it's data. SteveBaker (talk) 02:29, 16 August 2010 (UTC)

It's not all that weird, because there are two competing things going on here. Yes, in a longer sprint, you can run a higher proportion of it at peak speed than in a shorter one. But the peak speed will not be as high, because you have to save more strength for the longer run. --Trovatore (talk) 02:46, 16 August 2010 (UTC)

The 100m and 200m averages happen to be very close. The 150m average would probably be higher if it was a regular event but it's an extremely rare distance and not run in championships. Usain Bolt's record [4] was not in good conditions (though it helped there was no curve) and he said "I'm not in the best shape and I still have a lot of work to do but I am getting there." Before his run there was a poor record from 1983. If there was a "10m with flying start" event where acceleration time didn't matter then I guess the peak speed would be slightly higher, because in normal races they use a lot of energy in the initial acceleration at low speed. PrimeHunter (talk) 13:40, 16 August 2010 (UTC)

It occurs to me that we're being asked about any track and field event. Is it possible that (for example) long-jumpers reach faster peak speeds? SteveBaker (talk) 02:29, 16 August 2010 (UTC)

Or pole vaulters, on their way down? Jørgen (talk) 10:35, 16 August 2010 (UTC)

Well, a spherical pole vaulter falling under the influence of a homogeneous 1g gravity field in a vacuum through the distance of the world record height of 6.15m would reach a speed of 10.98m, slightly higher than the above estimates. But pole vaulters are not spherical, or jump in a vacuum. And, more to the point, they don't really lift their center of gravity over the bar, and they don't fall back all the way to the ground (there is at least 1m of mat). So terminal speed comes out at a bit less than 10m/sec. --Stephan Schulz (talk) 12:26, 16 August 2010 (UTC)

In any case, haven't we established that the maximum instaneous speed is probably closer to 12m/s? The split times may not be perfect hence why I'm quoting a lower figure but they can't be that far off. The problem with SB's analysis is he's looking at the average speed only yet as he acknowledged you need to reach the peak speed first. We see this in the split times of course. As Trovatore has semi pointed out, you can't maintain such a peak for ever, although I don't know for sure I'd say that the peak at slightly higher distances is lower. It may be the same, or even higher and either the person takes long to reach it or they start to taper off near the end. However as I said earlier, I doubt the peak is going to be that different from what we've already got and given the problems trying to determine instaneous speeds at high accuracy it's largely a moot point anyway IMHO. Nil Einne (talk) 13:07, 16 August 2010 (UTC)

I agree. The trouble with times over shorter and shorter distances is that the fuzzy issue of which part of the body you treat as the measurement point starts to dominate the numbers. If the runner had (let's say) his nose furthest forward at the start of the 10m split time - and an arm at the forward extent of it's swing at the end of the split distance - then the runner's center of gravity may only have moved 9.5 meters rather than 10. That's what makes me skeptical that the 12 meters per second 'burst' is really valid. Plus the fact, what measurement is our OP really asking about - nose to nose, furthest-forward-part to furthest-forward-part? The results will surely be dramatically different in those two cases - and we can think of many other different definitions for "distance travelled". SteveBaker (talk) 23:03, 16 August 2010 (UTC)

Steve, look again (or for the first time, if you haven't) at the PDF linked above (it's here, to save you some scrolling). It's quite clearly not a "burst" to 12 m/s. There's some high-frequency oscillation that may indeed be explained by the body-part thing, but the main part of the curve stays above 12 m/s for most a large fraction of the run.

Also, your hypothesis that the stamina effect kicks in only after 150m is inherently implausible. That's not how muscles work. If you lift weights, you know very well that you can use your muscles at higher intensity if you don't have to do it for as long, going down to quite short intervals, say a single bench-press repetition.

So what's going on, I conjecture, is that the stamina effect is there from the very beginning. If there were world records kept for propelling your center of mass forward 10 meters, and 20 meters, you would find that the first 10 meters of the 20-meter world record would be slower than the 10-meter world record.

But for average speed, this competes with the effect of the time it takes to accelerate, which is why the average speed goes up, flattens out around 150 m, and then goes back down again. --Trovatore (talk) 09:41, 18 August 2010 (UTC)

You can do a quick calculation from those world record speeds. Let's assume that all the acceleration occurs during the first 50 metres (I think it's slightly less than that, more like the first 30 m, but I don't have a reliable source for that). So we subtract the world record time over 50 metres from the other times, and calculate the speed over the rest of the course: that gives 12.43 m/s for the 100-metre record and 11.01 m/s for the 200-metre record. My guess (taking into account the comments below about the 50-metre time) would be that the maximum speed of a human is a little bit less than 13 m/s (29 mph). I would expect long jumpers to be any equally good measure of this maximum speed as 100-metre runners, but we don't seem to have any hard data to go on. Anyone for pointing a radar speed-gun at a long jumper during the next big athletics meeting? ;) Physchim62 (talk) 16:12, 16 August 2010 (UTC)

I believe sprinters in training film themselves with high speed cameras and use other technology to work out which bit of their race is letting them down and how. That would suggest that the information we want is known, we just have to try and find somewhere that it has been made public. --Tango (talk) 17:13, 16 August 2010 (UTC)

Is it possible that the slower speeds for 60 and 90 metres reflect the fact that these are less prestigious events and therefore don't attract the same number of attempts to create new records? --rossb (talk) 13:27, 16 August 2010 (UTC)

I think it's certain that that is the case. The 50m record hasn't been broken for more than 14 years, while the 100m record has been broken about 10 times since then and had over a quarter of a second knocked off it. People just don't race over 50m these days. --Tango (talk) 15:15, 16 August 2010 (UTC)

It's possible that there's some effect there, but it's not obvious from the records. The average speed of the world record time goes up to a maximum and then goes down, with only a single peak; this is exactly what you would expect from the hypothesis I outline above in my response to Steve. --Trovatore (talk) 09:44, 18 August 2010 (UTC)

Nasty Prickly Sucker

nasty prickly sucker

On my land there is a spiny prickly plant growing near some english ivy on some rocks. Unfortunately I fell down on it on thursday and am living with itchy red bumps on my hand. I was wondering if anyone could identify the plant for me and I can do some research on it.. Thanks. schyler (talk) 15:03, 15 August 2010 (UTC)

I can't identify it, but it reminds me of Datura stramonium or (vaguely) Solanum carolinense - if you don't get a real answer here, try posting this image at Talk:Solanaceae. There are still quite a few species Wikimedia Commons still needs to get pictures of, so please don't throw out this photo! Wnt (talk) 17:14, 15 August 2010 (UTC)

Are you quite sure it wasn't the ivy you were reacting to? My husband comes out in hives if he touches ivy. --TammyMoet (talk) 18:30, 15 August 2010 (UTC)

Displacement time response

If we displace an amount of gas trapped in a medium, will it take a time estimated by the speed of sound in this medium in order to sense this displacement at a distant point? If yes, does this rule apply to liquids and solids (for example displacing a steel bar of length of about 10 km and sense the first response of this displacement at the other end)?--Email4mobile (talk) 16:26, 15 August 2010 (UTC)

Yes, that's about accurate. It is especially accurate for the steel-bar case, and is pretty accurate for an incompressible fluid (liquid). In a gas (or liquid), the actual propagation time is confounded by convection and bulk movement of particles, which are a fairly nonlinear process. Often, multiple speeds are defined for a fluid - such as p-wave and s-wave speeds for elastic fluids; and in other fluids, empirical descriptions of travel-time speeds can be defined. Generally speaking, bulk fluid motion is sub-sonic, so information propagating as an acoustic pressure wave will usually arrive before any other method of information propagation, including shear-waves, rayleigh waves, or convective or bulk fluid movement. An important exception is a detonation or supersonic shock front, where bulk movement of air particles is forced to occur at a speed greater than their resting acoustic sound-speed. Transsonic and supersonic fluids behave very strangely, for exactly this reason - their "normal" method for particle interactions is too slow to account for the actual changes in mass, energy, and momentum distribution. Nimur (talk) 18:44, 15 August 2010 (UTC)

Relay race strategy

Why do you think that the "second fastest, third fastest, slowest, then fastest (anchor)" strategy is the most used in relay races? --Belchman (talk) 18:32, 15 August 2010 (UTC)

Probably nothing except psychological reasons. Fastest man last is obvious - best chance on that sprint to the finish line. second fastest first hopefully gives a little bit of a lead at the beginning, so the two slowest runners (who usually aren't particularly slow, mind you) can focus on maintaining a lead they already have rather than trying to catch up to others. --Ludwigs2 22:35, 15 August 2010 (UTC)

the first runner is the only one who has to accelerate from a standing start, so more than psychological factors come into play. Looie496 (talk) 00:47, 16 August 2010 (UTC)

But the last runner is the only one who is able to risk running out of stamina in a sprint to the finish line. SteveBaker (talk) 01:41, 16 August 2010 (UTC)

honestly, it's probably just a status thing. first and last runners are the ones people are most likely to remember, so they go to the team stars. the rest is just rationalization. The race is won by the collective time of all four racers (barring fumbled batons and such), and there's no technical reason why the order they run in should matter. --Ludwigs2 02:08, 16 August 2010 (UTC)

Yes and both of those are why second fastest first and fastest last make sense. As for the other two, third fastest second may have some psychological advantage in reducing how far they may fall behind. (I thought of this earlier today before anyone had replied but didn't say anything but since everyone else is speculating why not?) Of course whether these factors actually get any consideration or it's really just tradition, status or whatever I don't know. Nil Einne (talk) 11:58, 16 August 2010 (UTC)

One factor that I have seen have an impact, particularly in 4 X 100 relays, is who runs best around the curve. Those best at doing so would get the first and third legs. HiLo48 (talk) 12:12, 16 August 2010 (UTC)

how do armless people masturbate

like this guy

http://cdn2.sbnation.com/imported_assets/521792/kylemaynard_medium.jpg

—Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 19:11, 15 August 2010 (UTC)

Well, I admit I have no personal experience with this at all. It might just not be possible in some cases, depending on the degree of the paraplegia, though one should never underestimate the human ingenuity that surrounds ways of sexual self-gratification. (One could imagine, for example, that "props" — like a Dutch wife, or even just the old fashioned "hole in a pillow" method — could be employed to pretty good effect by males, even without the use of hands. For females, I imagine the use of toys is probably still possible for the dextrous.) But apparently there has been at least one book written on the subject of paraplegic sexual activity, and from the review linked to, I wouldn't be surprised if it discussed these kinds of options. --Mr.98 (talk) 19:39, 15 August 2010 (UTC)

By rubbing oneself against an inanimate object. 82.44.54.4 (talk) 19:47, 15 August 2010 (UTC)

that would hurt a lot —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 21:07, 15 August 2010 (UTC)

I don't see how. Put a pillow between your legs and rub on it. Does it hurt? If it does I suggest you seek the advice of a doctor. 82.44.54.4 (talk) 21:15, 15 August 2010 (UTC)

Let me clarify the IP's suggestion: rubbing oneself against a soft inanimate object. A soft easily washable inanimate object for men! --Tango (talk) 21:46, 15 August 2010 (UTC)

Hookups. John Riemann Soong (talk) 21:35, 15 August 2010 (UTC)

it does hurt if you are circumcised. theres no lubrication. chafing ect. do their nurses masturbate them? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 22:27, 15 August 2010 (UTC)

So then, um, one uses lube if "no lube is a problem". I think your question has been answered here. DMacks (talk) 22:44, 15 August 2010 (UTC)

While I appreciate circumcision can make things more difficult our article specifically mentions rubbing against an inanimate object as a common male masturbation technique (I've even read debates about whether it's harmful), I'm pretty sure that some circumcised males must do it. If it's not possible for you, either you're not doing it right or there's a specific health issue that we can't help you with. Of course outside of masturbation Non-penetrative sex#Frottage is also a fairly common sexual practice and depending on precisely what's being done may share some similarities. In any case, using lubrication is always advisable if there is any pain or other such problems during masturbation and is often useful particularly for circumcised males. BTW, the first result for 'hands free masturbation' is [5] although the picture doesn't show what's described in the text (shouldn't need to say it isn't work safe). Incidentally I also came across [6] which I think is a serious site, for circumcised males. Nil Einne (talk) 23:15, 15 August 2010 (UTC)

do their nurses masturbate them? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 02:25, 16 August 2010 (UTC)

We are being trolled by Tomjohnson357. This is not a scientific question and so is not appropriate for this Reference Desk. Dolphin (t) 02:45, 16 August 2010 (UTC)

I think that such questions are perfectly in order. Had they been on some similar (non-sexual) theme—as to how native peoples cut their toenails, for example—there would have been no cause to object. It is wowsers attempting to censor WP.

The more relevant question is how do quadruple amputees cut their toenails? -- 111.84.151.46 (talk)

I do remember reading (and that means this is a reference to a reputable third party and therefore within the ambit of WP) that during the 1950s, a Russian youth, rendered armless through an industrial accident on a collective farm, bought a cow milking machine for the purpose of masturbation. He managed to attach one of the rubber teats to his penis and turn the machine on with his teeth. He had a wonderful first orgasm and then a second. After that, his penis became sore and he tried to switch the machine off and remove the teat, but with no success. He had a third orgasm and by then was becoming desperate. Somehow, he got to his phone and rang the factory that produced the milking machines and told them he was having trouble turning it off, without, of course, telling them what he was using it for. Oh, said the girl on the switchboard “That’s OK, it will stop automatically when the bucket is full...” Myles325a (talk) 03:20, 16 August 2010 (UTC)

Will Myles325a be providing the reference to the reputable third party source? No? I thought not. Dolphin (t) 03:33, 16 August 2010 (UTC)

That sounds like the kind of urban legend where a true story of someone being an idiot gets embellished with the addition of an ironic punchline and some extra details to try and make it sound more believable. The idea that someone would use a milking machine to masturbate is highly plausible, in fact, I'd be very surprised if it has never happened (although, chances are they weren't armless and didn't buy it, they probably worked on a dairy farm) but the "it will stop when the bucket is full" bit was probably just added on for a joke (cow milking machines don't have buckets, for a start, they have massive tanks, you only use a bucket for hand milking). What was this reputable source? Was it either someone saying they did it themselves or a doctor saying they treated somebody that did it? If it wasn't one of those two, it isn't reputable. --Tango (talk) 04:09, 16 August 2010 (UTC)

You're mostly correct. The same milking machines that feed the bulk tanks can have a bucket put on them for cows that have been treated with any medicines that shouldn't be put into the bulk milk. Dismas|^(talk) 09:44, 16 August 2010 (UTC)

I recall reading pretty much exactly that story in the "True Stories!" section of an FHM magazine about ten years ago. That, of course, is about the most cast iron guarantee possible that it's not true at all. ~

mazca ^talk 09:37, 16 August 2010 (UTC)

While it's not an RS for the milking machine story, I can offer Br. Med. J.: 1942, 1960, doi:10.1136/bmj.1.5190.1942 {{citation}}: Missing or empty |title= (help) as a source for a similar line of action: this New Scientist article (for 1985, so 25 years after the original publication), suggests that men are somehow destined to repeat the errors of their fathers (or uncles, or whatever!) Physchim62 (talk) 15:50, 16 August 2010 (UTC)

Humor aside, someone ought to use the older reference there, and others findable by search, to start an article penrig, for one of the more peculiar units of measure in the world. Wnt (talk) 16:20, 16 August 2010 (UTC)

 Done Physchim62 (talk) 17:27, 16 August 2010 (UTC)

Also just in case anyone is wondering about the other important issue raised here regarding how native peoples cut their toenails, my extensive studies have shown that the hill tribe people of Laos favour an odd looking device fashioned from what appears to be a metallic material. It features some kind of symbolic language. It's difficult to make out but it appears to say something like "nipping Chuangxing Nail Clippers Made in China 100mg". Sean.hoyland - talk 10:00, 16 August 2010 (UTC)

Where legal, it seems far more likely a sex worker would be hired instead. BTW, in terms of the story, beyond the bucket issue there's also another what seems to be obvious flaw in the story. Cows don't have an unlimited amount of milk. If your cow is out of milk continously milking it until the bucket is full is not going to do anything but injure the cow. In modern times of course, a machine without some sort of safety off is going to fall foul of OSH regulations in most developed countries. Nil Einne (talk) 11:54, 16 August 2010 (UTC)

most armless people cant afford sex workers. and its not legal most places either. most do have full or part time nurses though. is it legal for them to masturbate the man? —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 17:48, 16 August 2010 (UTC)

If they are armless and have financial difficulties I would suspect they have bigger things to worry about then masturbation (no pun intended) Nil Einne (talk) 19:46, 16 August 2010 (UTC)

i cant imagine whats worse than lying in bed every night with a painful erection. —Preceding unsigned comment added by Tomjohnson357 (talk • contribs) 19:50, 16 August 2010 (UTC)

If you have painful erections every night when you don't masturbate, you should see a doctor. As for the more general point you clearly have never lived a life (or even thought of one) in financial difficulty if you genuinely think masturbation is that important. (I haven't either but it's something you can contemplate.) Not having enough food to eat, not knowing if you will have a home tomorrow, not being sure if you could afford the things like electricity that you need for the home even if you have one, not being sure if you can afford any home help to do any basic things you can't manage like tidy up your home (you mentioned a nurse, I'm not really sure what this 'nurse' is for but they're definitely not going to be cheap), not being sure if you can afford a doctor for when you have medicial issues (which I would guess are probably more common for an armless person), are plenty of things which an armless person in financial difficulties is likely to be more concerned about then masturbation Nil Einne (talk) 16:58, 17 August 2010 (UTC)

Freshwater fiddler crab

The fiddler crab article reads like a handbook but avoids sourcing its statements. I would like to purchase a couple of fiddler crabs for my 29G freshwater tank and have 4 concerns: the article states that there is really no such thing as a freshwater fiddler crab and that they should not be kept in freshwater for more than a day or so -- is this accurate information? Secondly, must I have rocks branches in the water that allow the crab to break the surface, or can they live totally underwater? Thirdly, if I get a male and a female, how likely will they mate? And fourthly, should I worry that they will catch/kill my fish? I have some neon tetras, platys and mollies -- I had crayfish as a kid and I fed them live minnows. Will the crabs do the same? DRosenbach ^{(Talk | Contribs)} 19:15, 15 August 2010 (UTC)

Fiddler crabs aren't really predators, but you can still end up with something like this: [7] Unfortunately each aquarium, its size and layout and food and fish, is a different experiment, far removed from normal ecology - no scientific publication is likely tell you whether each of your fish are safe. I see many websites stating that fiddler crabs don't thrive in fresh water. To contradict them, could someone examine fulltext of [8], [9]? (regarding Uca minax, Uca spinicarpa) Based on the long but not infinite time that aquarium specimens can spend in freshwater, and the absence of fiddler crabs far from the sea, I suppose there must be some sticking point - can they breed in fresh water? I wonder if you could take a few different freshwater species, hybridize them to improve genetic variation, and passage them for a few generations in increasingly fresh water until you have a new crabby counterpart to Caulerpa taxifolia to unleash on the river ecosystem?

Time

Please explain the phrase "Abyss of Time"

Thank you

User: Center 33 —Preceding unsigned comment added by Center39 (talk • contribs) 20:05, 15 August 2010 (UTC)

This is primarily a metaphorical way of displaying the seemingly indefinite and eluding concept of time. Tyrol5 [Talk] 20:07, 15 August 2010 (UTC)

And in some cases it may be an allusion to Prospero's phrase "the dark backward and abysm of time" in Act I, scene 2, of The Tempest. Deor (talk) 20:52, 15 August 2010 (UTC)

Quoting, "The Abyss of Time is a massive underground labyrinth that appeared in the playable epilogue in Persona 3: FES, titled The Answer. Originally a state of hibernation, it became 'active' when it was attracted by the grief and sorrow of SEES, and spread it's influence there, rooting down below the dorm.". The moral is that questions like this can't be answered without knowing the context. Looie496 (talk) 20:54, 15 August 2010 (UTC)

Dinosaurs eating one another

Is there a similar order of animals that eat one another as a primary part of their diet? Obviously dinosaurs dominating the world was a factor in such carnivory, but I just wonder. Thanks. 67.243.7.245 (talk) 20:37, 15 August 2010 (UTC)

Uh, mammals? Uh, birds? Uh, fish? Uh, insects? It's harder to find an order of animals that doesn't. Looie496 (talk) 20:56, 15 August 2010 (UTC)

Mammalia and insecta are both classes and fish is a confusing collection of classes and phyla. Birds and dinosaurs are both complicated due to the differences between Linnaean taxonomy and phylogenetic taxonomy (in short, birds evolved from dinosaurs but appear completely different, so should birds be considered a type of dinosaur? The Linnaean approach says no, the phylogenetic approach says yes.) but if we use the Linnaean conventional taxa aves is a class and dinosauria a superorder. So, I think the best interpretation of the OP's question is to find a superorder or smaller in which members eat each other as a primary part of their diet. One example I can think of is polar bears eating seals - they are both in the order carnivora (I'm sure there are other examples from that order too, but this is the first I thought of). --Tango (talk) 04:30, 16 August 2010 (UTC)

(EC) Sorry I'm confused what the question is. There are plenty of modern day carnivores if that's what you're asking. Many species of Felidae for example. Note that dinosaurs were a diverse bunch of animals and the dinosaurs generally ate rather different dinosaurs. The fact that dinosaurs were eating dinosaurs isn't really that different from the fact many mammalian carnivores primarily eat other mammals Nil Einne (talk) 20:58, 15 August 2010 (UTC)

The relevant article might be Cannibalism in animals. It's rather common in some species. EverGreg (talk) 07:48, 16 August 2010 (UTC)

All dinosaurs are not members of the same species; so it is not strictly accurate to call a Tyrannosaurus a cannibal if it eats other species of dinosaur like hadrosaurs. Nimur (talk) 08:33, 16 August 2010 (UTC)

Absolutely true. EverGreg (talk) 10:56, 16 August 2010 (UTC)

Weasels' primary predators are other members of the order Carnivora. APL (talk) 15:30, 16 August 2010 (UTC)

Chimpanzees are (now) known for devouring other primates... Wnt (talk) 15:36, 16 August 2010 (UTC)

And some members of the subtribe hominina eat other primates as well.... CS Miller (talk) 20:09, 16 August 2010 (UTC)

Is there a specific name for this concept?

An animal that generally avoids predation by being too big for anything that's fast enough to catch it to take without great difficulty - and also too fast for anything that's big enough to take it to catch it without great difficulty. This came up when discussing gulls with someone this afternoon - as some of the larger larids are a bit like this. --Kurt Shaped Box (talk) 22:18, 15 August 2010 (UTC)

No, but there is a name for the opposite category: dinner. Looie496 (talk) 02:15, 16 August 2010 (UTC)

The usual term is "having no natural enemies" or "natural predators". According to wikipedia, the adult elephant is one example, though animals may prey on young or weak individuals. EverGreg (talk) 07:55, 16 August 2010 (UTC)

Under Kurt Shaped Box's specification, would not this require there to be a predator larger but slower than an elephant? (87.81 posting from . . .) 87.82.229.195 (talk) 11:19, 16 August 2010 (UTC)

Blue whale is larger and at least on land it is slower than elephants and it is a predator.--Gr8xoz (talk) 14:41, 16 August 2010 (UTC)

This is a complex topic, and such a simple rule wouldn't generally be accurate. Consider camouflage, mimicry, venoms and poisonous compounds, general unpalatability, armor, spines, ink sacs, and just plain dexterity - among many others, no doubt. Also remember that small predators can take down a larger prey (lions devouring a full-grown elephant, as shown beautifully in a Planet Earth (TV series) episode [10]. At the extreme, consider MRSA taking down a human... Wnt (talk) 15:32, 16 August 2010 (UTC)

Perhaps there is something in Antipredator defenses in birds and mammals By Timothy M. Caro Sean.hoyland - talk 15:41, 16 August 2010 (UTC)

Workings of a rolling mill

My 1988 World Book Encyclopedia says that a hot-rolling mill can take a piece of steel 5 inches thick by 8 feet long and produce a sheet 1/16 inch thick and 1,400 feet long; the width of the piece isn't mentioned. In other words, the final thickness is 1/80 of the original thickness, but the final length is 175 times the original. I can't understand: how could this be done without violating the conservation of mass? Would the final width be less than half of the original? Please note (1) the diagrams on the facing page are side-on, not showing width, and (2) I've read the section to which rolling mill is a redirect, but I can't find an answer. 71.79.87.249 (talk) 23:54, 15 August 2010 (UTC)

I think when they say 8 feet long, they actually mean 8 feet wide, the 8 foot width stays the same, and the length "1,400" is meaningless since they don't give you the starting length. A rolling mill is a continuous process. I don't think they work with 8 foot batches (although the article does imply that at least historically they used to, but I'm pretty sure they don't anymore). This is just a guess though. Ariel. (talk) 00:21, 16 August 2010 (UTC)

Actually I think they still do. See this explanation of a continuous mill that uses billets of metal. Rmhermen (talk) 14:47, 16 August 2010 (UTC)

This sounds much like wire drawing, where a short thick rod becomes a long thin wire. As the metal goes from one set of rollers to the next, it becomes thinner and moves faster. No "extra mass" is created. The width must be constrained to be no wider than the rollers at each stage. A rectangular billet which was not too wide could become a thinner and wider and longer sheet of about the same volume and of exactly the same mass (neglecting any Einsteinian mass/energy equivalence, not likely to be a significant effect in a rolling mill). Edison (talk) 23:25, 17 August 2010 (UTC)