Wikipedia:Reference desk/Archives/Science/2008 October 8

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October 8

Headset to hear dictations

What are the technical specifications that we have to look in a head phone to get maximum efficiency to hear dictations and comfort for wearing long hours?

As far as comfort goes, that's not likely to be a question of technical specifications. Your head and ears are pretty unique in their shape, and what is comfortable for one person may not be comfortable for you, and vice versa. -- Captain Disdain (talk) 01:17, 8 October 2008 (UTC)

For example, I switched from earmuffs (which I otherwise prefer) to plugs after I got new glasses whose shafts stand out further from my head than before. —Tamfang (talk) 05:34, 8 October 2008 (UTC)

Sensory Integration Disorder and its Impact on Potty Training

I have a 4 yr old daughter who has SID and is very hypersensitive. She has been working with OT and PT since she was 5 mths old. No one has any clear information to give me on how to potty train! The developmental specialist states to give her time- the uroligists states she must get it done b/c of the severe negative side effects it has had on her (kidney infections that have led to hospitalizations). She is very fearful of even sitting on the toilet much less wanting to be in the bathroom when it flushes! I have read all I can find on SID and own numerous books on potty training. Are there methods used for children with SID to help with this issue??

Thank you- —Preceding unsigned comment added by 12.202.108.191 (talk) 03:25, 8 October 2008 (UTC)

Have you asked the medical professionals for locations of appropriate support groups? Have you tried searching on the web for support groups that address this specific issue? There are lots of parents here, but we're really not allowed to give medical advice on specific issues. Franamax (talk) 05:01, 8 October 2008 (UTC)

And there's no particular reason the child must be in the bathroom when the toilet flushes. She can be standing just outside the door watching when you flush the toilet, and then she can hold a long stick to help you flush the toilet, and then she can use the stick herself. But that's starting to be medical advice... Franamax (talk) 05:07, 8 October 2008 (UTC)

Strange gender inequality in the dental industry

I've been to numerous dentists. Why are the dentists always only men and the assistants always only women? Are you ready for IPv6? (talk) 03:49, 8 October 2008 (UTC)

That's an interesting question. Have you tried to seek out dental clinics where the dentists are female? As far as the gender split goes:

• Dentist does seem to be a male-dominated field. A discussion on possible gender-bias can be found here. Stand-alone professional fields such as dentistry would seem good ground for women to avoid gender bias, since they have only to fulfill the qualifications. I would speculate that those women so inclined might gravitate instead to pharmacology or in particular physiology (M.D.-type doctor rather than D.D.S-doctor). Perhaps those women inclined to a medical field either go big or go home (pace to any dentists who might think I denigrate their important field - but it does rank just a little under M.D.).
• As far as dental assistants or dental hygienists, I would speculate that the field offers a good way for women of child-bearing age to acquire a valuable transferable skill that offers them maximum flexibility as to hours worked, balanced with a good income. Also, women are probably just better as dental assistants, since they're more empathetic, interact naturally with children, etc. You can read that as a sexist statement, but I mean it as a statement of great admiration.
• And the factor of bearing and caring for children must always be considered in choice of training and work for women - they're the ones making them after all. :) In the case you question though, the balance does seem somewhat skewed. Franamax (talk) 04:55, 8 October 2008 (UTC)

My current dentist is female, my former dentist was female. Of the 4 dentists over my life-time 2 have been female. Of course that's my perspective and so statistics might not back this up. Just throwing that in there. 194.221.133.226 (talk) 10:32, 8 October 2008 (UTC)

Could it be the case that greater (on average) physical strength and large hands are an advantage when pulling teeth? Or that the general wisdom is such - thus discouraging some women from taking up dentistry? A personal observation - the only time a female dentist tried to remove one of my teeth (I've had a lot of teeth removed), she wasn't strong enough to budge it and had to go fetch a male colleague. --Kurt Shaped Box (talk) 10:59, 8 October 2008 (UTC)

Personal observation #2 - my lower wisdom teeth had twisted roots and the (male) dentist couldn't pull them no-how. He ended up jack-hammering them into pieces (which I still have). As well as the pain from the extraction site, I had a bruise on my jaw from where he braced his hand trying to pull. The point about physical strength may have some merit. Franamax (talk) 21:24, 8 October 2008 (UTC)

This site has some numbers. It says there is an 83%/17% male/female split among all private practice dentists in the US. It's interesting to note that at a prestigious veterinarian school in my area there is a similar split in the other direction. --Sean 14:51, 8 October 2008 (UTC)

It's probably the same reason that most Doctors (traditionally) have been male, and most Nurses female. "Dentist is to Doctor as Dental hygienist is to Nurse" (FWIW, my current dentist is female, and I know of male hygienists, just like I know female doctors and male nurses) -- 128.104.112.147 (talk) 15:40, 8 October 2008 (UTC)

A dental hygienist is different from a dental nurse. --Tango (talk) 23:23, 8 October 2008 (UTC)

I'm a male and I don't work out very well and probably every woman in the miitary is stronger than me so I don't think it's strength. As for pregnancy, dentists often share a practice with another dentist and dentists themselves generally see the patient for two minutes during checkup. I also have noticed there's a lot of female vets. I'm not really quite sure how to really search for lots of dentists. I usually call 800-DENTIST when I move, but my last move within about 50 miles only one dentist was registered. That dentist had a nice office with fancy machines so I thought he'd be good. It turns out that he pays for it all by not just charging 4 times more for an exam, but will give false diagnosis and tell people they need expensive things done that only harm their teeth. I wasn't certain until I searched on the internet about this. There's countless cases of people who moved to a new location, got a new dentist, and despite having no cavities or other problems for 10-15+ years their new dentist claims to find 5-12 cavities that don't exist just so he can mutilate a person's body to make extra money. It's rather common. I take it dentists don't have to take the hipocratic oath. Are you ready for IPv6? (talk) 01:39, 9 October 2008 (UTC)

Well, if you just wanted to rant about how evil dentists are, you could have saved us some time and effort answering what looked like a legitimate question. How's this then? Dentists are a male-dominated caste placed on this earth solely to suck away our cash and destroy our bodies. There you go, you read it here on Wikipedia, so it must be true. Can we close this thread now? Franamax (talk) 02:51, 9 October 2008 (UTC)

That wasn't reason for the question. I just bought it up along with a lot of othe things because I saw a lot of people discussing this. Are you ready for IPv6? (talk) 03:41, 9 October 2008 (UTC)

OK, I'll retract any suggestion that you posed an improper question in the first place. However, the later post you made strays over the line into our striction that the RefDesk is not a forum for opinions, nor is it a soapbox to put forth your own opinions. If you have a specific follow-up question, we can consider it. Franamax (talk) 03:47, 9 October 2008 (UTC)

It seems that over-servicing is not an article here though Google attests dentistry is rife with it. Dentistry may not have the hippocratic oath as such, but its national professional association would have an ethical code and is the body to complain to usually. On wiki, entering "Dental ethics" gives you Michele Aerden who instigated the first Dental Ethics Manual and "Dentistry ethics" comes up with stuff worth sifting if you're keen. Julia Rossi (talk) 10:45, 12 October 2008 (UTC)

immume system

types of immumoglobine —Preceding unsigned comment added by Ksneyhaa (talk • contribs) 06:37, 8 October 2008 (UTC)

WIth regard to the immune system, we discuss immunoglobulins IgA, IgD, IgE, IgG, and IgM. - Nunh-huh 06:43, 8 October 2008 (UTC)

chemistry

two flasks A & B have equal volumes .flask A contains Hydrogen maintained at 300K while B contains methane gas maintained at 600K. 1.which flask contain greater number of molecules & hwmany times more —Preceding unsigned comment added by Bhuwanntl (talk • contribs) 07:55, 8 October 2008 (UTC)

"Do your own homework. The reference desk will not give you answers for your homework, although we will try to help you out if there is a specific part of your homework you do not understand. Make an effort to show that you have tried solving it first." -- Aeluwas (talk) 08:53, 8 October 2008 (UTC)

Your question is unanswerable, because you have not specified whether the two flasks have equal pressures. Take a look at combined gas laws. If we specify that pressure is equal, you're looking at Charles's law. - Nunh-huh 09:00, 8 October 2008 (UTC)

Aflatoxin in raw peeled peanuts

How can I know if raw peeled peanuts are contaminated by Aspergillus flavus and Aspergillus parasiticus? Is it possible to see it like mold on bread? Mr.K. (talk) 12:14, 8 October 2008 (UTC)

Peanuts in general are susceptible to aflatoxin contamination. You wouldn't see the aflatoxin itself (except under blacklight), but you might see the fungus that produces it. Cooking doesn't really affect it, since the toxins are heat stable (the fungus that produces them, however, is not). Fungus doesn't imply aflatoxin (not all fungi produce it), but lack of fungus doesn't guarantee safety. Like most toxins, a really small dose (i.e. one dubious peanut eaten per year) isn't going to kill you. If in doubt, don't eat it (no surprise there), but probably best to avoid the whole group if you see some fungus growing on anything in it. SDY (talk) 13:01, 8 October 2008 (UTC)

Sleep injuries

I'm failing to find the medical term for injuries that occur while sleeping, such as pulling a muscle or separating a joint. Is there a term to classify those injuries? -- kainaw™ 13:18, 8 October 2008 (UTC)

They don't happen often enough, and aren't intrinsically different from similar injuries occurring while awake, for there to be a common medical name for them. - Nunh-huh 15:22, 8 October 2008 (UTC)

Semen and Enzymes

Do the enzymes in washing detergent break down the proteins ect, that are in semen? i always wash my underwear seperately, because i worry that im simply spreading it all evenly on my clothes, and that microscopic amounts will rub off on where i sit ect. Zakbrak341 (talk) 13:56, 8 October 2008 (UTC)

If they're only microscopic amounts, what difference does it make? Also, why do you have so much semen in your underwear? You're meant to remove your clothes for that kind of thing... --Tango (talk) 14:10, 8 October 2008 (UTC)

Its not loads, just very small amounts of precum before i take them off ect, if got lots on them i'd just throw them away, but the thought of any amount of semen on anything bothers me, for a while i was doing a hot wash, so it would denature the protiens but then i worried that the heat would denature the enzymes in the powder, and if the enzymes break down the protiens into amino acids, then thats better than simply unfolding the protien into its secondary of primary structure, then i started worrying, what if these enzymes in the washing powder are specfic to protiens in common food stains only and have no effect on the protiens in semen, so now im just wash them in serveral changes on water with lots of detergent. —Preceding unsigned comment added by Zakbrak341 (talk • contribs) 14:31, 8 October 2008 (UTC)

Tango, two things. First, some people are kinda clean freaks when it comes to everything, so it's not really unusual to be concerned over whether semen is contaminating other clothes in the washing machine. Secondly, it's not really your place to ask him why he has semen in his underwear, you should only address his questions. 98.221.85.188 (talk) 14:35, 8 October 2008 (UTC)

Your detergent should emulsify fats, which means that it wraps little bubbles of detergent around your semen and stops it from sticking to any of your clothes. Plasticup ^T/C 15:08, 8 October 2008 (UTC)

Except that semen is essentially fat-free. No emulsification. For the original questioner: the enzymes in washing detergents are designed to be as non-specific as possible in breaking down proteins, and should have no trouble with semen. - Nunh-huh 15:19, 8 October 2008 (UTC)

Even if someone can get something which is soiled physically clean, meaning that the offending sunstance cannot be seen or even detected by CSI, they still remember it was once there. It can get more into ritual purification, like the concept of a ritual bath removing some iniquity or moral stain. I read a housewife's complaint to an advice column that her husband had soaked his sore toe in warm salt water (at the doctor's advice) in one of her expensive gourmet cooking pots, and that she had to throw the pot away because she would never afterward feel that it was "clean" regardless of scrubbing or dishwasher cleansing. If the questioner gets a reference to an authoritative laundering site which says a wash of some temperature on some cycle with certain cleaning products will render the garment as clean as it was when it came out of the package, then he might be saved the expense of frequently throwing garments away and buying replacements. Some people, even in this era of "cold water" energy-saving detergents wash a load of white cotton washcloths, towels, and underwear in the "hot" wash cycle with detergent and chlorine bleach, with an extra rinse, Not saying this is the authoritative answer to the original question, and there is also the question of enzymes versus bleach and hot versus cold water to eliminate biological stains. Interestingly there are loads of book references dealing with semen stains[[1]] though few specifically address their removal. (Not to be confused with the mythical character "Seaman Staines" on the Captain Pugwash children's program). Edison (talk) 15:23, 8 October 2008 (UTC)

You can check how good a job your selected detergent is doing by taking a look at your unmentionables under a black light before and after the wash. 71.178.135.144 (talk) 02:15, 9 October 2008 (UTC)

Not a great method. While semen does fluroesce under a black light, it is not the only thing that does. Lots of detergents and fabric softeners do, as well. When you see, on crime shows, them use a black light to look for semen and/or blood, it's not the black light that proves its presence; the black light merely lets them know where the most likely places to test are. Its only after they have done a positive chemical test can they know that the stain that glows under black light is semen, or blood, or any of a number of other agents that also glow... --Jayron32.talk.contribs 02:24, 9 October 2008 (UTC)

If it makes the questioner feel any better, the sperm in semen dies after the semen dries, so no matter what, there is no sperm spreading around your clothes or to any other surfaces.--el Aprel (^facta-_facienda) 20:20, 11 October 2008 (UTC)

E=mc^2...Whatever that means.

Hey...what unit is the E in $E=mc^{2}$? Is it calories, Joules, tons, or what? I have been wondering about this for a while and saw the article on E=mc^2 with its handy list of how much energy is contained in a dollar bill. It lists several units of measuring energy, which got me confused. When you convert mass to energy, is the mass converted to Joules or calories or another type of energy? 31306D696E6E69636B6D (talk) 16:36, 8 October 2008 (UTC)

Well, it defaults to kg·m²/s² (Joules), which it does say in the intro :)

In the formula, c2 is the conversion factor required to convert from units of mass to units of energy. The formula does not depend on a specific system of units. In the International System of Units, the unit for energy is the joule, for mass the kilogram, and for speed meters per second. Note that 1 joule equals 1 . In unit-specific terms, E (in joules) = m (in kilograms) multiplied by (299,792,458 m/s)2.

-- MacAddct1984 ^{(talk • contribs)} 16:42, 8 October 2008 (UTC)

(ec) :Joules and calories are units of measurement, not different "type[s] of energy". Just like you can measure speed as miles per hour or kilometers per hour or feet per second and can convert a speed from one to the other but it's still the "same speed". So whatever units you use for c and for m determines the units of E. If that's not the unit you want, you can convert. Or you can choose what units of energy you want and then convert the mass and speed of light to use them. DMacks (talk) 16:43, 8 October 2008 (UTC)

As long as you're consistent, you can use any unit system (for example, you could use ergs, but then you would have to measure the mass in grams and the speed of light in cm/s - see cgs). Usually scientists use SI units, where energy is measured in joules. It's also common to see energy measured in electron volts. --Tango (talk) 16:46, 8 October 2008 (UTC)

You're wrong: you can use any units that measure the same thing. For example, instead of asking how many 'joules' a certain number of 'kilograms' would result in according to e=mc^2, you can ask Google how many "horsepower-hours" (which measures the same thing joules do) a "pound" of stuff results in. Just google "1 pound * c^2 in horsepower*hours". You get "1 pound * (c^2) = 1.51859015 × 1010 horsepower * hours". In other words, if you had a magic reactor in your room that completely turned matter into energy, then with 1 pound of fuel you could output one horsepower (745 watts) for

15000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 hours.

You haven't used the same equation, though, you've added a conversion factor (or, you've absorbed the conversion factor into the constant by measuring the speed of light in obscure units). You have to use consistent units, otherwise you quite clearly get nonsense. If I use kg for the mass and m/s for the speed, plug it in and I get joules for the energy, I can't just choose for that to be ergs or electron volts or horsepower hours, since that would be assuming they are all the same thing. To get to another unit I had to multiply by a conversion factor so then I'm actually using E=kmc² where k conversion factor. --Tango (talk) 21:12, 8 October 2008 (UTC)

No, you're just wrong. Take something simple: distance = speed * time. So, 60 miles per hour for two minutes = distance = 60 m/h * 2 minute = 120 minutes * m/h, ie "120 mile-per-hour minutes". And look 120 mile per hour * minutes = 3.218688 kilometers is a perfectly good answer. You can ask for it in feet, inches, anything. It's just a unit conversion, it's not solving an equation. —Preceding unsigned comment added by 82.120.232.170 (talk) 12:26, 11 October 2008 (UTC)

yeah, just remember that the CONSTANT in the equation, C, isn't just a number, like a million. Instead, it's a "million miles per hour" (for example). So, if you take a pound, or a kilogram, or any unit of mass you want, and mulitply it by a million miles per hour squared, you get a certain amount of energy. I don't have an intuitive conception for why a million miles per hour squared times 1 pound should be an amount of energy though... —Preceding unsigned comment added by 82.120.232.170 (talk) 17:54, 8 October 2008 (UTC)

Lets take it in terms of the metric system, for symplicity. Energy is defined, in one instance, as the measure of the change of speed of object of a defined mass over a defined distance. From a unit-based analysis, that means that energy is measured as kilograms times meters squared divided by seconds squared, ( kg*m²/s² ). That is the inherent definition of energy. The deal is, if you do ANY other combination of measurements, and arrive at the same final units, that is a measure of energy. For example, air pressure*volume is a unit of energy (air pressure can be expressed as force per unit area, and force is mass * acceleration, and volume is displacement cubed, so the if we express pressure as (kg) * (m/s²) / (m²) * (m³) we get, kg*m²/s², which is energy. How we calculate energy, as electron-volts or as newton-meters, or as joules, or as liter-atmosphere (these are all energy measurments) is largely dependent on the particlar application. --Jayron32.talk.contribs 18:18, 8 October 2008 (UTC)

I've thought of an analogy that might help you: if you could increase your gas mileage by 20% for every 10% under the speed limit that you go (just made that up!!!) you can use that without knowing units for EITHER mileage OR speed limit -- and indeed, our British readers would translate that "tip" into different actual numbers than the Americans...

So if m is kilograms then E would have to be in Joules? 31306D696E6E69636B6D (talk) 18:29, 8 October 2008 (UTC)

No, you're confused by the mistake the poster above made. See my correction of him above. (The poster above is lazy and wants to just cross out units that are the same, for example, when you multiply 55 miles per hour by 2 hours you figure out what units the answer will be by going: [m/h]*[h], ie crossing out the two h's. But you can just as easily ask what distance you go in a minute at that speed).

The easiest thing to do is play around. Into google put "c=" . Then try "1 lb * c^2". And put "1 kilo * c^2". Then you can ask for the results in different units by saying "in" as I did above ("1 pound * c^2 in horsepower*hours").

If m is in kg and c is in m/s, the E will be in joules. If you chose different units for c, you'll get different units for E. --Tango (talk) 21:14, 8 October 2008 (UTC)

Energy is dimensionally equivalent to Force*Distance, which is equivalent to Mass*Speed*Speed. (See Dimensional analysis for a better grounding on the subject.) The exact units that Energy comes out in is dependent on the units that you use both for mass and for speed. $E=mc^{2}$ is always valid, regardless of choice of units for any two of the quantities, however, the units of the third may end up not to be a "conventional" measure (e.g. $stone*furlong^{2}/fortnight^{2}$ is a unit of energy, albeit not one that has much use/respect). SI, however, is designed to be self-consistent, so if you stick to the standard SI units, things tend to work out well, unit-wise. Kilograms, meters, and seconds are all base SI units, so for mass in kg, and speed in m/s, the units of energy work out to the SI unit of energy (joule), because the joule is defined as equal to $1kg*m^{2}/s^{2}$ (See joule#Description). -- 128.104.112.147 (talk) 22:27, 8 October 2008 (UTC)

I think a workingman's explanation of e=mc^2 is prudent here. When you convert mass to energy, you are literally doing just that. Mass becomes energy. The 'type' of energy mass becomes is actually explicit in the formula. When mass is converted to energy, for instance in a nuclear reaction, it is released as a photon, which is why we use 'c' as a conversion factor: the mass is converted into light! --Shaggorama (talk) 07:46, 13 October 2008 (UTC)

Except that E=mc² holds for all mass-energy conversions, not just the ones which involve photons. For example, with beta decay, the weak interaction causes a neutron to decay into a proton, an electron, and a neutrino - no photon involved. Yet, there is a detectable reduction in the total mass of the system, which correlates to the amount of energy released by the decay by the equation E=mc². It gets even stranger. The mass of a proton is about 60-160 times that of the three quarks of which it is composed (the gluons being massless). Where does the extra mass come from? It's mainly the binding energy of the three quarks, along with the kinetic energy of their relative motion. Absolutely no photons involved, yet this mass-energy equivalence is still governed by E=mc². The use of c is due to its property of being a fundamental metric of 4-dimensional spacetime (specifically, the conversion factor which allows you to interconvert time with spacial distance) - the fact that it is also "the speed of light" is just a side product of that, not the key essence of the quantity. -- 128.104.112.147 (talk) 23:20, 13 October 2008 (UTC)

safe dough?

I live with an Italian, and she's making pizza in four days -- but she's started today. She mixed a spoonful of honey with oil into flour and water and is letting it rise at room temperature, keeping it moist under a moist cloth (which she will keep remoistening over the next four days). This "mother" dough she will use over the course of several pizzas, the first one Saturday, until she's done with it.

My question is: how does this work? I'm not sure what role the "mother" dough has, is it like yeast?

In fact I heard that "sourdough" was created by accident more than a hundred years ago, and since then they have alwyas been reusing the same starter -- they always saved a little to make more. But she's not adding a "starting" piece, she's just starting from honey and oil! So, isn't it just a random toss-up what microbes will start growing? Why is it even safe?

Obviously I'm not asking for any medical or legal advice... —Preceding unsigned comment added by 82.120.232.170 (talk) 17:14, 8 October 2008 (UTC)

Actually, the invention of having isolated yeast which you add to the dough to make it rise is a relatively recent invention. For thousands of years, bread was made the same way: You mixed flour, water, and a few seasonings, you sat the mixture on the window sill, and it picked up whatever yeast cultures blew in on the wind, and the bread rose and you baked that. The problem is that some cultures don't taste particularly good. Someone a long time ago figured out that if you find a particularly tasty piece of dough, rather than let future batches of dough get cultured randomly, if you innoculate it with your good-tasting culture, you get equally good tasting bread. This is often accomplished by reserving a "starter" or "mother" culture from each batch of bread, and using it to innoculate the next batch. However, you can also control which cultures take hold in your bread by carefully controling the chemistry of the dough. Cultures are highly sensitive to variations in pH and salinity and other factors, so the specific ratios of say, honey to salt to flour will basically be highly favorable to a single variety of microorganism, and not so much to the others. Once you find a recipe that attracts the right yeast, if you use the same recipe each time, you will end up with the same yeast each time, and thus a fairly consistent bread. --Jayron32.talk.contribs 18:04, 8 October 2008 (UTC)

(EC) See sourdough, which is exactly what she's making; it should be delicious! The reason it's not a toss-up is that whatever incidental microbes might be hanging around get their asses kicked by the massive amounts of good yeast and bacteria already in the flour. It's only if they run out of food (the honey) that those agents will start to die off and bad ones can take over. Sourdough has been around for thousands of years, and while it is indeed possible to keep a starter going indefinitely, most people just start one from scratch. --Sean 18:15, 8 October 2008 (UTC)

if I get you right, your response implies 1) flour you buy has lots of good yeast and bacteria in it (and not bad ones), it's made that way? How's that work? 2) if you added honey forever the good ones would always have enough to eat, you could keep it going a month and then bake it... —Preceding unsigned comment added by 82.120.232.170 (talk) 19:45, 8 October 2008 (UTC)

Actually, most of the yeast is present in the air, or on the flour itself. The yeast is just there, it isn't added or anything. It may grow on the grain naturally, or it may just alight on the flour from the air. The determining factor as to which microbe predominates is the local chemistry in the dough. The good yeast, if correctly encouraged to grow, will simply crowd out any nasty critters. --Jayron32.talk.contribs 20:09, 8 October 2008 (UTC)

In fact, the use of "ambient" yeast and bacteria in lambic beer rather than pure yeast cultures is the reason for the rich complex taste of Belgian beer. - Nunh-huh 21:03, 8 October 2008 (UTC)

1) Correct. It's only natural that microbes that can live on wheat will be found on it in the wild. 2) No, just adding honey won't do it. You also need to add more flour, and water, and keep the bacteria/yeast balance correct. I seem to remember Harold McGee's magisterial On Food and Cooking covering the details, but I'm sure many baking books do, too. FYI, some cooks have kept starters going for *decades*, though refrigeration makes that a lot easier. --Sean 22:32, 8 October 2008 (UTC)

We cannot rule out that "wild" yeast or fungus might make the dough taste bad or even become toxic. Edison (talk) 03:53, 9 October 2008 (UTC)

An archived Ref Desk answer describes some undesirables which might grow in a dough culture : "I suppose we could add a disclaimer about "Ask a baker" or "Ask a mycologist" for bread mold advice. I claim no expertise in this area and only cite info found on the net or from general reading, including a baking textbook, and from baking various types of bread in the home. The surface of fresh-baked bread is generally free of microorganisms because of the heat of baking, but ropy mold may survive in the interior of bread. The surface can become contaminated while the bread is cooling or being wrapped, while it is sliced, or while it is stored. [2]. Bread can be attacked by various types of mold. There are over 600 varieties of bread mold. Some of them are listed at [3]. Note that the same mold may grow on bread and other substances, and some of these are toxic to humans. In general, some spores are just part of nature. But if mold from bread or other sources has left a high concentration of spores in an area such as your kitchen or your breadbox, it stands to reason that a loaf of bread placed there subsequently might get moldy quicker than if the mold spores were not drifting around. See Black bread mold, [4] at Madsci.org. Edison 14:59, 14 August 2007 (UTC)" Edison (talk) 18:49, 9 October 2008 (UTC)

and, of course, once you've made a few loaves of bread in a kitchen it's pretty thoroughly inoculated with enough yeast on a permanent basis. fungi are remarkably tenacious. I worked in a lab with the fungus neurospora crassa 20 years ago; i'm still seeing random colonies of neurospora appear around the house where i haven't hit it with the lysol lately, along with the usual household mildew and random gunk. mind you, i didn't grow the fungus at home, that's just from spores which hitched home with me; and moreover, I've moved twice since then. for another example, microbreweries which make beer for on premises consumption but subcontract the bottled product to big breweries (often the case) can specify their recipe, but can't specify their particular strain of yeast, as one particular strain of yeast will colonize a brewery, and you just can't make a batch with a different strain in that premises. (so i've been told at the local microbrewery). see also lambic for another example of trusting in airborne yeast to produce a palatable and nontoxic product, rather than adding a defined yeast (oh, somebody said that already). Gzuckier (talk) 06:03, 11 October 2008 (UTC)

Erronious definition

I found this definition for Hyperthyroidism. I don't believe this is the real definition. I couldn't figure out how to correct it so I am sending it to you.

<obvious bit of vandalism removed ... no need to keep that around for posterity --98.217.8.46 (talk) 03:13, 9 October 2008 (UTC)> —Preceding unsigned comment added by 152.130.7.64 (talk) 18:27, 8 October 2008 (UTC)

Yes, that's a bit of vandalism in our hyperthyroidism article. It's fixed now, thanks for pointing it out. - Nunh-huh 19:09, 8 October 2008 (UTC)

Perhaps it's an alternate definition? --Sean 22:38, 8 October 2008 (UTC)

Perhaps in an alternative universe. - Nunh-huh 23:32, 8 October 2008 (UTC)

Do gas giant even have a flowing water?

Do Jupiter, Saturn, Uranus, and Neptune even have a flowing water in it's mantle or it's just a hot dense white-hot vapor if human touch it they will instantly get electricute and roast. All their core is very white-hot, hotter than the surface of the sun.--SCFReeways 23:13, 8 October 2008 (UTC)

To be honest, I'm not sure. Any water in the mantle would be extremely hot, but the pressure may be enough for it to stay liquid. I think it would be all mixed in with everything else rather than flowing, though. A human at those temperatures would be instantly killed, yes, although I don't know why you think they would be electrocuted... --Tango (talk) 23:20, 8 October 2008 (UTC)

• metallic hydrogen for jupiter and Saturn, certainly they conduct electricity, even Uranus and Neptune the ice to me actually means electronic stuff, hot gluey vapours similar to lightning and molten comets. I don't think is true water the water we use and drink. Those planets is total gas, and landing to me is like going to hell. No solid surface no place to land, from what I've learnt when I was elementary student, if we try to land on it we will just keep sinking trough their interior, until we get to it's nucleus, and even prior to getting to it's center, the strong heat will instantly kill humans, even those dense vapours. Does your saying of liquid mean vapours from the burnt rockets?--SCFReeways 23:36, 8 October 2008 (UTC)

To answer Tango's question, I presume the OP is concerned about that big-ass storm that's been circling Jupiter for at least the last 300 years. And there's plenty of lightning on Jupiter (at least) and presumably the other gas giants. Matt Deres (talk) 23:42, 8 October 2008 (UTC)

• Even Uranus and Neptune's mantle I beleive is made of deadly "junks" possibly liquid, eelctrical wastes, vapors, perhaps anything.--SCFReeways 23:51, 8 October 2008 (UTC)

I think we can all agree that anyone standing in the core of a gas giant would be killed instantly. The heat and pressure would be extraordinarily deadly. I'm pretty sure you would not live long enough to be electrocuted by a lightning bolt.

Does that answer your question? APL (talk) 01:35, 9 October 2008 (UTC)

Heat, pressure AND radiation. The gas giants are certainly pretty nasty places. Given that there must be a more or less continuous gradient from the low temperature and pressure of space down to the metallic hydrogen at the center - you'd imagine that there would be some altitude at which liquid water could exist - whether there actually is enough water at that level to form flows is much harder to determine. Probing the conditions deep into that atmosphere is very hard. SteveBaker (talk) 01:53, 9 October 2008 (UTC)

Are you saying gas giants have a core that is just gas? Not rock? I'd assume enough asteroids fell into them to give them a rocky core, though I hear Saturn is very light. Though I also would assume then that the sun must swallow a lot of asteroids, though why this doesn't make the sun die with iron going into its core, who knows. Are you ready for IPv6? (talk) 03:39, 9 October 2008 (UTC)

Talking about Earth or gas giant? While Earth have "Greenhouse" or "Icehouse" have nothing to do with gas giants. Earth had icehouse in the past, and once it was cooler when all the continenets is at the South Pole. 100 to 200 million years later, Earth will likely to be greenhouse or hot again. I don't know why you ask this becasue this have nothing to do with the question.--Freeway91 19:58, 9 October 2008 (UTC)

Gas giants have a solid core, but not because they swallow asteroids, it's because of the immense pressure. 98.221.85.188 (talk) 04:17, 9 October 2008 (UTC)

I don't think the core is rock as we know it. In Jupiter's case, at least, it's rather exotic matter (metallic hydrogen and similar), due to the intense pressure. Regular rock would probably be destroyed long before it reached the core. --Tango (talk) 10:23, 9 October 2008 (UTC)

Well, the elements that make up the rock (iron, etc) have to be there somewhere. In these cases, though, it's a matter of scale. Neither Jupiter nor the Sun consume enough asteroids to be relevant when analyzing their overall composition. — Lomn 13:01, 9 October 2008 (UTC)

Sure, the elements will be there, but not in the forms we're used to. They had plenty of the components of rock from the start, they don't need asteroids for that (well, they make have formed by aggregation of what were essentially asteroids, but that was a long time ago), but those components can't make rock at those temperatures and pressures. --Tango (talk) 13:36, 9 October 2008 (UTC)

I wonder if consumered rock has anything to do with the sun cycles like the sun is supposed to go in cycles where it varies from stronger and weaker to what it puts out. I know that the earth while it did go into cycles of hot to freezing, did used t average a lot hotter but in the last tens of millions of years it gradually really cooled down and then the recent ice age was pretty much its lowest point and then it started warming back up a bit, but still lower than the average. Mars was also supposedly warmer at one time, too. Are you ready for IPv6? (talk) 13:46, 9 October 2008 (UTC)

Highly unlikely, again as a matter of scale. There's just not enough foreign material entering the sun to affect things, even if things would be affected in the first place. With that caveat, it's worth noting that even dropping a planet-sized chunk of iron into the sun would likely have no effect. Iron is the fusion stage at which stars quit, yes -- but the presence of iron should have no effect on the hydrogen fusion process currently ongoing, or the helium fusion that will follow once the hydrogen is exhausted, or the lithium or beryllium or whatever follows that. Iron isn't exothermically fusible, but neither does it poison other fusion reactions. — Lomn 14:08, 9 October 2008 (UTC)

Metallicity does affect how a star behaves, but I agree that on the scale we're talking about the effect would be negligible. I'm not sure much even falls into the sun - to do so it would need to shed almost all its angular momentum, which is pretty difficult to do. --Tango (talk) 14:18, 9 October 2008 (UTC)

Time-independent Schrödinger equation: "If $\psi$ is a solution then $\psi$* is also a solution."

In an Introductory Quantum Mechanics book I'm reading, the author often claims that if $\psi$ is a solution then so is its conjugate, and this is stated as being self-evident (leaving me to suspect I'm missing something obvious). Previously, I've only ever encountered complex conjugates when related to an actual complex number, whereas $\psi$ is actually a function $\psi (x)$, hence my confusion.

The equation is as follows:

$E\psi =-{\frac {\hbar ^{2}}{2m}}{d^{2}\psi \over dx^{2}}+V(x)\psi \,$

This forms part of a question that asks to show that a time-independent wave function $\psi (x)$ can always be taken to be real, because if a solution isn't real it can just be expressed as a linear combination. Quote: "if $\psi (x)$ satisfies [the above equation], for a given E, so too does its complex conjugate, and hence also the real linear combinations $(\psi +\psi *)$ and $i(\psi -\psi *)$."

So I basically have two questions: 1) Why can we say $\psi *$ is a solution because $\psi$ is? 2) What else is this question looking for, since it basically gives the answer away when it talks about the linear combinations?

I have the feeling I'm mis-interpreting something here, so I'd be grateful for any clarification or help. Leucippus89 (talk) 23:54, 8 October 2008 (UTC)

Edit: Just to be clear, this question is about $\psi (x)$ and not $\Psi (x,t)$. I know that when you solve the Schrödinger equation by separation of variables, the time-dependent function always has complex components which are dependent on t and so could be safely ignored (?) in an equation that's just concerned with x. But that's not what this question's about, and I think that's what's confused me, because I'm not used to seeing complex terms in $\psi (x)$. Leucippus89 (talk) 00:39, 9 October 2008 (UTC)

I suppose $E$, $V$ and $m$ are all real? If so, it's pretty easy to see that $E\psi ^{*}=(E\psi )^{*}$ and $-{\frac {\hbar ^{2}}{2m}}{d^{2}\psi ^{*} \over dx^{2}}+V(x)\psi ^{*}=\left(-{\frac {\hbar ^{2}}{2m}}{d^{2}\psi \over dx^{2}}+V(x)\psi \right)^{*}$. —Ilmari Karonen (talk) 02:45, 9 October 2008 (UTC)