Wikipedia:Reference desk/Archives/Science/2013 June 12

= June 12 =

Mites and ticks
Is it true that mites and ticks find it harder to bite/sting musclier people? Clover345 (talk) 00:53, 12 June 2013 (UTC)


 * Probably, in general. Men are generally more muscular, and generally have thicker skin.  Be— —Critical  01:04, 12 June 2013 (UTC)
 * But muscle isn't attached to skin so why would it have an effect? Clover345 (talk) 01:44, 12 June 2013 (UTC)
 * "Probably, in general." Is about as unspecific as you can get two words to be. Men are generally more muscular, What has the musculature of men have to do with tick bites? Are women more prone to tick bites? and generally have thicker skin. Do they? is that a guess too? I could almost believe if you had said that men on average have thicker skin on the palms of their hands because men on average they do more manual labour, but even then I wouldn't be totally convinced. And what does thick skin have to do with musculature?? Not a single word of that reply helps answer this question in any way. Now, subcutaneous fat I could believe plays a factor, less body fat makes a person appear more muscular but it is not correlated. You can have skinny weak people with little body fat or you can have huge muscular people with very high fat, like sumo wrestlers, so I doubt actual musculature has anything to do with it. A thinner skin and fat layer might make it harder for a tick to bite you, but for all we know, without a reference, it might make it easier for a tick to bite you. Taking a stab in the dark without any logical induction does not help at all. Vespine (talk) 05:48, 12 June 2013 (UTC)
 * I think Becritical was probably trying to make a joke. There is a statistical correlation between muscularity and thick skin, so there is probably a statistical correlation between muscularity and tick-bitability.  This is a prime example of the fact that correlation does not in general imply causation. Looie496 (talk) 06:37, 12 June 2013 (UTC)
 * :D Be— —Critical  13:56, 12 June 2013 (UTC)
 * A tick can bite through cowhide with no problem. Human skin is much softer so I doubt a tick would find it harder - even in muscular people. I've had tick bite fever several times and I would say, as a generalization, that ticks seem to prefer the softer skin on your body - e.g. inner thigh groin area, under arm area and scalp. This may have nothing to do with the softness of the skin but rather that they can more easily hide in these areas and suck away unnoticed. This is based purely on my personal experience.196.214.78.114 (talk) 07:28, 12 June 2013 (UTC)
 * There are many species of mites and ticks - perhaps there is some variability in their bite capability? Certainly there are ticks that feast on cows - and those must be able to penetrate the thick hide on those animals. However, these kinds of blood-feeding pests aren't always able to cross species (eg dog fleas don't like to bite humans)...so it's possible that the kinds of tick that can bite through cowhide simply don't have what it takes to feed on humans for other reasons.
 * We need some solid evidence here - a decent reference would definitely help in answering this question accurately. SteveBaker (talk) 13:37, 12 June 2013 (UTC)
 * Agreed - it's very important to get the original folklore right before you try to confirm it. I don't know for example if what they mean is that someone who is active is harder for a tick to hang onto, etc. Wnt (talk) 15:39, 12 June 2013 (UTC)

I'm having trouble finding any study of the bitability of different people. There are plenty of papers on tick preferences, but most concern species preference. One paper states that, at least in South Africa, few ticks actually prefer humans, mostly feeding on other, larger animals. Put that in the pile of things that suggest our skin should not be a problem at all. The one study I could find on preferences between different people was concerning adults vs. children, and concluded that behavior (time spent near tick habitats) rather than size or odor was the main driver of bite-rate differences. I seem to have misplaced that paper, so please forgive the lack of citation. I also question the very premise that muscle mass would even be associated with skin thickness. In at least one part of the body, skin thickness seems to be more associated with fat than muscle, which has an accompanying curious correlation between skin thickness and prognosis for kidney failure patients! Just another reminder that Looie's point is very important. So in the end, I question every aspect of this question, even the underlying claim - if the main determinant of tick bites is behavior, I'd expect people doing outdoor athletics, who may be more muscular, to get more tick bites. And if none of this has anything to do with skin thickness, which was not suggested by the OP, then I question it nonetheless, as the ticks are not biting through to muscle anyway. Someguy1221 (talk) 04:34, 13 June 2013 (UTC)

Sievert
In the article Sievert there are outdated quality factors which are superseded by ICRP 103 publication. — Preceding unsigned comment added by 217.21.43.22 (talk) 09:18, 12 June 2013 (UTC)


 * Well... update it? — Preceding unsigned comment added by 217.158.236.14 (talk) 09:31, 12 June 2013 (UTC)


 * Indeed, we encourage anyone who has a solid reference for a fact (and the ICRP publication would certainly count) to dive in and edit the encyclopedia to make it better. If you feel nervous about doing that, then you should at least report your findings on the "Talk" page for that article: Talk:Sievert - because this really isn't the right forum for that kind of thing. SteveBaker (talk) 13:32, 12 June 2013 (UTC)


 * It was mentioned there a couple of times, but nobody cares. -- 217.21.43.222 (talk) 16:59, 12 June 2013 (UTC)


 * Somebody cares - but anybody who works with radiation safety - and requires both precision and currency - should not be consulting a free online encyclopedia. Our encyclopedia article provides a thorough summary, and enough information to help guide anyone with more interest towards proper reference material.  In fact, ICRP Publication 103 is the first reference listed in the sievert article.  It is available for purchase, and a free excerpt is available online. Nimur (talk) 18:00, 12 June 2013 (UTC)

Basic rocket anatomy
Looking at this picture of the recently-launched Chinese rocket, I was just wondering, what is the main big tube most likely filled with and what about the smaller tubes on the sides? I see a number of types of setups at Rocket propellant. If one of those, e.g., LOX and kerosene, are the case here, are each of the tubes likely independently having all needed to be a thruster, or are the small tubes and the one big one having fully different ingredients only all together forming a working thrust system? 20.137.2.50 (talk) 14:23, 12 June 2013 (UTC)


 * According to our Long March (rocket family) article "the main stages and associated liquid rocket boosters use dinitrogen tetroxide as the oxidizing agent and UDMH as the fuel". Each of the liquid rocket boosters will be a self-contained rocket system, linked to a central thrust control. Gandalf61 (talk) 14:45, 12 June 2013 (UTC)


 * Long March seems to have a very similar booster arrangement to the R7/Soyuz rocket family, for which there's more public documentation available. Starsem's outline guide to Soyuz (here) shows internal diagrams for the Soyuz core stage and for its four strap on boosters (p22-). As Gandalf61 says for the LM, the Soyuz boosters run (essentially) the same engines as the core stage, and all four boosters and the core have their own fuel and oxidiser tanks. For the Soyuz, calling the core stage "stage 2" is a bit misleading, as its engines are lit at takeoff and burn (at about 50% power) all the time the boosters are running. Once the boosters are finished and gone the core throttles up to 100%. In contrast, this page says that the LM's core doesn't start until shortly before the boosters are shed. -- Finlay McWalterჷTalk 17:16, 12 June 2013 (UTC)

Main Battle Tank
I have a question which may seems to be a silly question, when you take a look on the turret before assembling it on the hull , you find that it is impossible for the loader in a tank like leopard 2 to reach the ammo storage at the left of the driver because , there is an obstruction between the loader and the ammo storage because of the extension of the turret inside the hull (the cylinder which contains the crew) as in the image on this page http://www.miscellaneoushi.com/Military/army/army_tanks_german_bundeswehr_leopard_2_1280x853_wallpaper_25616  — Preceding unsigned comment added by Tank Designer (talk • contribs) 14:47, 12 June 2013 (UTC)


 * You should explain what you're asking better. Simply looking at the picture I don't see an obvious obstruction, and the idea that the person loading the shells can't reach the ammo seems highly unlikely. Wnt (talk) 15:37, 12 June 2013 (UTC)


 * Note also that, in principle, it is not necessary for the loader to be able to easily reach all of the tank's ammunition. Tank designers could easily opt to shoehorn in additional ammunition in inconvenient spaces, with the understanding that it can be transferred into battle-ready storage when the tank is not engaged. I believe, but can't cite specifics, that some tank designs have even incorporated such storage in external compartments that cannot be reached unless the crew exits the vehicle. This method of ammunition storage has been used in other areas, such as the WW2-era Type VII U-Boat. &mdash; Lomn 17:20, 12 June 2013 (UTC)


 * That extension doesn't appear solid - I don't see what obstruction you're referring to. There are a bunch of items inside that space - but it may well be that they are simply stowed there temporarily when the turret is removed (eg to make wiring harnesses easier or something). (Higher res version of that image is HERE).  This image shows ammunition storage both behind the gunner in the turret and down in the front section of the hull.  This article talks about how the ammo is reached and suggests that the rounds stored in the hull are the primary ones - with the additional rounds in the turret locked away behind an electrically operated door. SteveBaker (talk) 18:43, 12 June 2013 (UTC)


 * And while we're on the topic, why can't they devise a system for automatically loading shells, rather than requiring people to do it ? We've been able to do this with bullets since the Gatling gun (or earlier), after all. StuRat (talk) 04:30, 13 June 2013 (UTC)


 * See Autoloader, which are indeed used in many tanks. A common argument against autoloaders is that until recently, humans were actually about as fast as them anyway, for your typical tank-caliber guns. There were also concerns of the reliability of the autoloader, and the fact that incorporation of an autoloader into many existing tanks would require a dangerous relocation of the ammunition, such that accidental detonation of the ammo would be far more likely to kill everyone in the tank. That particular concern has been mitigated in many vehicles by more recent improvements to autoloader design, or by designing a new vehicle around an autoloading gun in a way that eliminates the problem. Someguy1221 (talk) 04:45, 13 June 2013 (UTC)