Wikipedia:Reference desk/Archives/Science/2007 March 18

From Wikipedia, the free encyclopedia

< Wikipedia:Reference desk | Archives | Science

Science desk
< March 17	<< Feb \| March \| Apr >>	March 19 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

1 March 18

[edit] March 18

[edit] Thyroid Hormones

Why are thyroid hormones not used for weight loss in people with normal thyroid function? If one takes synthroid or cytomel, would that permanently effect his/her own production of thyroid hormones even after discontinuation of the pills(synthroid or cytomel)?

The main reason is that thyroid hormones are cardiotoxic -- they severely damage the heart. One of their effects is to enhance the body's sensitivity to the sympathetic nervous system. In doing so, the heart rate increases, predisposing individuals for cardiac arrhythmias. In addition, blood vessels constrict and elevate blood pressure. Both effects increase the workload of the heart, which can lead to heart failure. --David Iberri (talk) 19:21, 18 March 2007 (UTC)

[edit] narcotics

Is fentanyl the strongest??? Where can I find a chart of the strengths of the different kids of narcotics??

[edit] Lifestyle Change With Dramatic Results in One Year

Hello. A few years ago I remember reading an article in Reader's Digest about a middle-aged, potbellied balding lifelong smoker who decided to change his lifestyle and observe and document the results after exactly one year.

He even had before-and-after pictures: the "before" picture shows an overweight, flabby, pasty-complexioned, balding man in his mid-forties with glasses and a decent-sized paunch smiling sardonically, sitting down on a chair wearing red short-sleeved tights flexing his right biceps. The picture looked as ludicrous as it sounds. The accompanying article detailed his lifestyle: sedentary job, no exercise for God knows how long, smoker since age fifteen, 5'10" tall weighing 197 lbs., with a penchant for fast foods preferably in the super-size range.

The "after" photo showed the same man, this time in Speedo swim trunks, and by golly you wouldn't believe that this was the man who seemed destined to die of either a heart attack, stroke, cancer or some other such cause. He was standing and flexing the same right biceps, only this time there was a dumbbell gripped in his right hand and he was in the middle of doing a curl. His whole physique was nicely sculpted (not by Mr. Universe muscle-bound standards), from the top of his (still-balding) head, down to his taut and sinewy calves. Gone were the jowls on his bespectacled face; he was still smiling, but this time with more than a hint of pride showing on his glowing, finely-chiseled face. His complexion was now ruddy, and his jawline and cheekbones were well-defined.

Unfortunately, the article just gave a cursory description of his lifestyle change: stopped smoking, started eating right and exercising, both aerobically and with weight/resistance training. The point this article was trying to make was how dramatic, in just a year's time, the human body can change for the better if a lifestyle change is made and adhered to.

My question: does anyone out there have the details (well, more of them than was mentioned in that short Reader's Digest article) of how this guy did it, along with how he stayed motivated, how he overcame the many hurdles he surely must have encountered (including, without doubt, the pain of realizing the existence of muscles he never knew he had), what kind of exercises he started with, how he pushed himself to exercise progressively more without hurting or damaging anything, what kind of diet he followed, etc.....and most importantly, IF he was able to sustain this lifestyle change after that one year of keeping his nose to the grindstone so that it was a permanent change...or if the satisfaction of knowing that he could do it (that he in fact did it) proved enough of a reward for him to go back to his old, unhealthy comfortable ways?

My interest in this is more than academic; I will be turning fifty-one this year, and I have a lot in common with the "before" man right now. I'm not THAT flabby yet, but I'm getting there. My recent move to California from New York two years ago did a lot more than anything else to make me gain considerable weight. I would like to find out everything I possibly could about what this man did and how he did it --- because believe me, if you didn't know that this was the same man, you'd swear that those photos - spaced only one year apart - were of two different people.

Thanks in advance for any information you may be able to provide.

Ron 66.125.195.85 10:41, 18 March 2007 (UTC)

I have never heard of the the example you mention Ron. I can however say that changing ones physique is more a question of mind than body. My advise for anyone who wants to change his lifestyle is too take it one step at a time and to use self forcing practices. What I mean with self forcing is to put yourself into a position where you can't back out of your plan. Make plans,put them on paper make them visible to yourself and others and set goals. And try to meet these goals. Having other people around you doing the same will also help a great deal(imagine trying to stop smoking when the people around you aren't).

There are many websites (this one included) that can help you with practical advice on losing weight, gaining strength and increasing general fitness. I suggest you read those and ask around on fitness/weightlifting forums. You'll see that many people keep with their program because they like the results. They lose weight, get stronger, feel better. And on the oposite side when they don't keep to their self imposed program they feel bad, guilty even depressed. These positive and negative feedback systems are what keeps these people going.PvT 11:44, 18 March 2007 (UTC)

This may seem like an odd answer but I think geography has a lot to do with how long lifestyle changes take to come into effect. My opinion is that warmer climates will faciltate speedier recuperations. I have no citations and this edit may be swiftly reverted without explanation. Vranak

I think you might be right. In support of that hypothesis, people tend to weigh the most in winter, when it's coldest.[1] MrRedact 01:48, 21 March 2007 (UTC)

Have you tried contacting the people at Reader's Digest? As the name indicates, many of the articles in it (not the short bits like the joke pages or That's Outrageous! or whatever) are condensed versions of much longer print articles appearing elsewhere. You may be able to find the original article that way. This reference to the original article will appear in the print edition, so if you can dig up the actual old RD, you can get it that way, too. This might be a job for your friendly local dead-tree reference desk. --ByeByeBaby 07:37, 19 March 2007 (UTC)

[edit] Superconducting Super Collider

What happened to the partially dug part of the Superconducting Super Collider after the projects cancellation. Seeing as the tunnel system alone is potentially valuable for future large synchrotron projects surely? Or is there no benefit to a more powerful synchrotron than LHC? Philc _T^E_C^I 16:08, 18 March 2007 (UTC)

In short, politics plays a larger role than practical reasoning when it comes to multi-billion dollar science initiatives. The SSC is probably dead forever, and very probably due to a petty rift between the funding source and the potential users. Nimur 19:07, 18 March 2007 (UTC)

I live in Cedar Hill, Texas just a few miles from the site of the SSC. Part of the tunnel still exists - but they never did finish digging it - so it isn't a 360 ring - I think about a quarter of it was finished. That makes it pretty unsuitable for use for other synchrotron type applications. They used to run tours of the abandoned site - and they keep trying to come up with uses for the place - I think for a while it was used as a mushroom farm. But I very much doubt that any particle physics will ever be done there. SteveBaker 20:18, 18 March 2007 (UTC)

[edit] formula for an electric fan cooling a closed room

Is there a formula for figuring out how long it would take an electric fan to cool a closed room at a specific temperature. I have a temperature, the size of the room, the radius of the blades and the revolutions per minute. I'm trying to figure out how long a room can be cooled in the first hour it runs. If there is a formula, could you please advise?Thank you71.224.93.101 18:30, 18 March 2007 (UTC)

A fan wouldn't cool a closed room, it'd heat it up. -Wo o ty Woot? contribs 18:37, 18 March 2007 (UTC)

You might check out the heat equation, but it is of limited use since convection is the predominant mode of heat transfer in a room. You will need to make several questionably valid assumptions about laminar flow and an ideal source of cold air (i.e. fan in front of the refrigerator, or a cool outside window). Then you can apply those boundary conditions to this differential equation:

${\partial u\over \partial t} = k \left({\partial^2 u\over \partial x^2 } + {\partial^2 u\over \partial y^2 } + {\partial^2 u\over \partial z^2 }\right) = k ( u_{xx} + u_{yy} + u_{zz} ) \quad$

In practice, you will need something like a Finite Element Analysis simulator or some other computer package to solve this for a non-uniform shaped room.

A much much simpler equation is Newton's law of cooling. To apply this to a fan, you must again assume that the fan is blowing cold air from somewhere else (such as outside the room). However, it will conveniently give you a time-constant

τ

which is the closest way to answer your question. Nimur 19:12, 18 March 2007 (UTC)

In retrospect, I think these equations (and articles) might have scared you off more than helped you. Here is the first thing you need to know: fans do not cool anything, they only move air. If they are moving cool air into a hot room, that can have a cooling effect. (Thus the fan must be placed in front of a window or ice-box!) The rate of cooling depends on the temperature difference between the hot room and the cool air, as well as the amount of each.

You will have a tough time measuring how much air the fan moves, so you should make a first-approximation that it is moving air in a straight line. I can't think of a simple way to measure its speed. You might try some geometric calculations based on the pitch of the blade, the cross-sectional area of the fan, and the speed of rotation (try to imagine that you're conserving the volume of air). This will be messy and approximate, since no physical law requires conservation of volume in flowing air! Alternatively, you can look up linear flow rates from a catalog.

Once you have the amount of cool air in the room at any one time, you can apply Newton's cooling equation as linked above. Assume that the cold-source is the "constant" amount of cool air (though the actual particles are constantly moving). Solve for the time constant.

Alternatively, you could assume displacement of the room air, in a proportion of (fan flow rate)/(total room volume) per second. Calculate how long it would take to displace 99% of the room air (or any other arbitrary "final" cooled amount). Hope this helps,

Nimur 19:23, 18 March 2007 (UTC)

A fan running in a closed room would not cool the room. It would heat the room up an equal amount as an electric space heater drawing the same wattage. This sounds like someone gave you a trick question. Edison 04:46, 19 March 2007 (UTC)

Yes, as it has been repeatedly stated, the fan cannot cool anything. It can only move cool air in if there is an external source of cool air (open window, or an air-conditioning unit / ventilation system). Nimur 09:05, 19 March 2007 (UTC)

There is actually one way a fan can cool a closed room, via evaporative cooling. That is, if you aim a fan at a puddle in the room, this will cause the puddle to evaporate much more quickly than it otherwise would. And, as the water evaporates, the room cools (although the now more humid room may not feel cooler). The reason a fan blowing on you feels cool is the evaporative cooling of sweat it causes, as well as blowing cooler, dry air from the room on you and blowing the hot, humid air around your body away. StuRat 16:41, 19 March 2007 (UTC)

There is evaporative cooling, but can you prove that the cooling in a closed system is greater than the heating from the power dissipated by the fan? I once saw someone try to cool a machine in a closed room by aiming four 5 hirsepower fans at it, and the kilowatts of power dissipated by the fans made the heating worse. Can you prove that adding water to the system would have cooled the room, if it were a closed system? What happens when the air is saturated and the fans keep running? Edison 14:07, 20 March 2007 (UTC)

[edit] Trend and Pattern

I am analysing some biological data, and am having to comment on the trend and pattern in the data. I was wondering what exactly is the difference between a trend in data and pattern??? 89.241.4.129 19:32, 18 March 2007 (UTC)

I would say it is a matter of word choice. Perhaps trend is specifically within one graph (i.e. "data is a diagonal line with slope M", while pattern refers to the same trend across many different graphs of similar experiments?

Wiktionary says:

Trend - Inclination in a particular direction; tendency; general direction; as, the trend of a coast.
Pattern - arrangement of objects, facts etc. which has a mathematical, geometric, statistical etc. relationship

Nimur 19:52, 18 March 2007 (UTC)

[edit] Pig Gametes

Hi there, I'm having a spot of trouble finding what I need. I'm looking for what male and female gametes in pigs are called and I seriously can't find it. If you could help that, would be great.

Much appreciated. —The preceding unsigned comment was added by 71.229.138.46 (talk) 21:03, 18 March 2007 (UTC).

In most animals, the male gametes are spermatazoa (sperm) and the female gametes are oocytes (eggs). I don't know if there's a special name for pig gametes... My recent pig research has led me to the Pig Factsheet from the Pork Information Gateway (P.I.G.). Hope this helps, Nimur 01:00, 19 March 2007 (UTC)

[edit] LEP vs Tevatron

The LEP article states that "To date, LEP is the most powerful accelerator of elementary particles ever built." Now, I also know that LEP could only accelerate particles to 45GeV, and the most energetic collison it produced onl just topped 104 GeV. Whereas the Tevatron could accelerate particles to 1TeV, and produces collisions of up to 1.96TeV. Are these statments inconsistent, or is there some subtle distance between the energies of particles and the power of the accelerator, or is someone being perdantic with the definiton of elementary particles, seeing as tevatron accelerates protons and antiprotons, which's position as elementary particles is subject to debate seeing as they are constructed of smaller particles, however, they cannot be broken down. Philc _T^E_C^I 21:13, 18 March 2007 (UTC)

Actually, although you can't see free quarks, protons can be 'broken down' and form new hadrons. It is the quarks and gluons inside the protons which actually interact, so the centre of mass energy of the proton-antiproton collision (1.96Tev) is not the energy of the reaction, which is less. However as there are three valence quarks, a third gives an approximate guide to the magnitude of the energy of the quarks, which would still be higher than at LEP. The statement definitely refers to protons not being elementary, but is possibly misleading as elementary particles within the proton are accelerated along with the proton.Jameskeates 13:32, 19 March 2007 (UTC)

So is the statement true or not,should it be changed to most powerful lepton accelerator as opposed to elementary particle accelerator. Philc _T^E_C^I 14:57, 19 March 2007 (UTC)

I beleive the statement is true, the proton is not an elementary particle. Whether it's useful to have it in the article or not, I don't know. But that's for the article's talk page.Jameskeates 15:36, 19 March 2007 (UTC)

I think it should just be taken out, it's misleading. [Mαc Δαvιs] (How's my driving?) ❖ 16:16, 19 March 2007 (UTC)

[edit] High blood pressure - can it be alleviated by controlled blood-letting?

My grandma (who suffers from high BP) asked me this today (no, she's not thinking of trying it - it was just a hypothetical question). If a person's blood pressure is too high, would it be possible to return it to and keep it within acceptable limits by occasional, precise bloodletting? If not, why not? This has got me curious now... --Kurt Shaped Box 21:50, 18 March 2007 (UTC)

I don't think it is. If the pressure is too high because the blood is pumped 'too hard', the pressure will return when new blood cells have been formed. If the pressure is high because of clothed arteries, only operation on the arteries is going to alleviate it. And if the blood letting is not as precise as you hoped, the pressure will fall far below an acceptable limit. I'm therefore doubtful it would have a positive effect. - Mgm|^(talk) 22:42, 18 March 2007 (UTC)

(edit conflict)

No. I felt very strongly that blood pressure would go down, so I did a study at the red cross office in our hospital. Every nurse there agreed with me - BP would go down. To everyone's surprise, blood pressure goes up after giving 1 pint of blood. In some people, it goes up a lot. --Kainaw ^(talk) 22:44, 18 March 2007 (UTC)

That's the baroreceptor reflex at work. Decreasing blood volume (as occurs during phlebotomy) does transiently lower blood pressure, but the baroreceptor reflex acts so swiftly that blood pressure is rapidly brought back to its initial value. In individuals with normal blood pressure, the baroreceptor reflex would bring the blood pressure back to normal (120/80 mmHg). But in individuals with chronic hypertension, the set point of the baroreceptor reflex is elevated, so that a drop in blood pressure will be rapidly brought back to the initial hypertensive values. There's no way, save a defective baroreceptor reflex, that controlled bloodletting (ie, not a massive hemorrhage) will acutely lower blood pressure. However, I'd bet that a prolonged course of bloodletting, in which individuals are repeatedly drained, will transiently depress blood pressure so frequently that the set point of the baroreceptor reflex will be decreased, causing blood pressure to drop. I'm sure this has been tested in dogs somewhere, anyone care to check PubMed? Cheers, David Iberri (talk) 23:02, 18 March 2007 (UTC)

Maybe drinking more and thereby diluting their blood would help?

Dilution would be relatively rapidly corrected (via a decrease in vasopressin secretion), so that would be a pretty transient effect. Plus there's the danger of water intoxication by drinking so much water that you become dramatically hypoosmolal, which is a risk factor for neurological and other problems. --David Iberri (talk) 00:52, 20 March 2007 (UTC)

What about cutting yourself then drinking your own blood? would that help-- or would it just show that you have 'vampiristic' (is that a word?) tendencies? —The preceding unsigned comment was added by 88.109.124.137 (talk) 01:29, 20 March 2007 (UTC).

I believe the term for that is autovampirism. --Carnildo 23:38, 20 March 2007 (UTC)

[edit] Memory Retrieval Technology

What exactly is the status of being able to retrieve memories from one's head via technology, and save them as, say, a .avi file on my computer (ala Minority Report)? I can't imagine it's very far... Here7ic 22:45, 18 March 2007 (UTC)

Considering we still don't know how the brain really works, we're still pretty far. And I doubt my mind would resort to a Microsoft container format. --Wirbelwindヴィルヴェルヴィント (talk) 22:51, 18 March 2007 (UTC)

Perhaps AVC would be better for you?? Here7ic 23:21, 18 March 2007 (UTC)

Not enough is known about the storage mechanism to perform any real raw extraction. I'm inclined to believe that human memories are stored in wiki format, with vast amounts of metadata embedded into every element. Nimur 01:09, 19 March 2007 (UTC)

Point well stated. Here7ic 00:23, 21 March 2007 (UTC)

March 2007 issue of SA had a good article that is also available in its entirety online for free. Someday we will have digital memories. Today for some. -- atropos235 ✄ (blah blah, my past) 05:44, 19 March 2007 (UTC)

[edit] Blood test

When did it become possible to determine the gender of the unknown donor of a blood sample (by US scientists)? I want to know if it was possible in 1955 and/or 1966. - Mgm|^(talk) 22:54, 18 March 2007 (UTC)

I didn't know it was possible now. Is it possible to detect trace amounts of sex hormone or is there some other technique? I have never heard of this ability. Nimur 01:14, 19 March 2007 (UTC)

We can do DNA tests on a sample NOW; you only need to look for X and Y chromosomes. - Mgm|^(talk) 11:24, 19 March 2007 (UTC)

It has been possible since the discovery of the significance of the Barr body (present in females only) in 1949. This would show up best in WBCs when stained with methylene blue, but can also sometimes be apparent in the usual CBC stain, Wright's stain. - Nunh-huh 01:35, 19 March 2007 (UTC)

Note, most sex hormones are found in both males and females anyway. The difference is in the level. Nil Einne 09:40, 21 March 2007 (UTC)

Thanks. - Mgm|^(talk) 11:24, 19 March 2007 (UTC)

[edit] Alum

What is alum and hhow does it grow crystals????????????????? -Olivia Cole,10,IL

Did you read the Alum article? The section you are interested is most likely the Potassium Alum section. Alum is a double salt, made from Potassium, Aluminium, sulphate ions and water. It occurs naturally as a mineral. It has been known since ancient times. It is ised in dyeing. Aluminium is named after Alum. There is one Potassium atom for every Aluminium atom. The chemical formula is KAl(SO₄)₂(H₂O)₁₂. Alum dissolves more in hot water than cold, so if you dissolve as much as you can in hot water, and then let it cool there will be too much alum in the water. If you add a tiny alum crystal to the supersaturated solution, the crystal will grow rapidly. When the alum is insolution the sulphate, aluminium and potassium ions are wandering all over the place in the water. However when they turn into a crystal they are neatly arranged in a particular pattern. GB 23:33, 18 March 2007 (UTC)