Wikipedia:Reference desk/Archives/Science/2007 March 13

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March 13

Glucose

Hi, I read the article about Glucose and I want to know is what are the uses of glucose and what are the properties of glucose? Thanks. —The preceding unsigned comment was added by 74.14.117.171 (talk) 01:49, 13 March 2007 (UTC).

Are you sure you read the article on Glucose? I believe it has the uses and properties of glucose there. Glucose is what your body uses as energy, and in untreated diabetics, is excreted in urine. Splintercellguy 01:54, 13 March 2007 (UTC)

Yes, I have read it properly but it doesn't answer my question about the properties of the glucose. What are the properties of glucose?

Cancer

Is it possible for an infant to develop (or be born with) brain cancer? What is the youngest recorded age of anyone having brain cancer?Zain Ebrahim 09:40, 13 March 2007 (UTC)

Since genetic mutations are essentially random, it's possible. However, the chance would be on some rediculously small level, although various factors such as genetic predisposition (usually there would be significant familiy history if this were the case), or exposure to the right environmental toxins could increase the chance. So yes, it's physically possible, but darned unlikely, and I've never heard of an infant with cancer. Something worth googling, maybe. 131.215.159.161 12:22, 13 March 2007 (UTC)

Yes, it is absolutely possible to have cancer before birth, but it is also very rare. Here's a link to a paper which describes the appearance of some of these on ultrasound. (Note that the abbrevation US means 'ultrasound' in this context, not 'United States'.) While most malignancies arise later in pregnancy, teratomas can start at nearly any time. TenOfAllTrades(talk) 14:02, 13 March 2007 (UTC)

Chromosomes

How/why did chromosomes evolve? Can they relate (BE ASSOCIATED) in any way with the three biological motivational forces of SURVIVAL and REPRODUCTION and UNIFYING? (Trinological theory) Obviously, size of the chain - but what about the sorting of genes into the which chromosome? Max Greene —The preceding unsigned comment was added by 86.3.189.15 (talk) 09:52, 13 March 2007 (UTC).

For god's sake don't put your email on! I have deleted it. --Howzat11 10:25, 13 March 2007 (UTC)

Well the chromosomes determin characteristics, so the ones that are present are the best for their job, whatever that may be (eye colour, hight, etc). They evolved by mutations that were more effective that the previous chromosomes. The size of the chain is mostly because although not all of the chromosomes are in use at any one time, most of the possible characteristics are available in the chain. The sorting of genes into chromosomes is still not fully understood. Think outside the box 11:18, 13 March 2007 (UTC)

One could turn your whole concept inside-out and argue that genes are the entities that are surviving, reproducing, etc., and that all cellular machinery and life-forms as we know them are merely the mechanisms that the genes have evolved in order to perform those functions. Read The Selfish Gene. DMacks 16:22, 13 March 2007 (UTC)

In other words (and I don't know who created this line): "A chicken is an egg's way of making another egg". Bunthorne 18:09, 13 March 2007 (UTC)

Nonetheless, it's a good quote from whomever. Gotta remember that one... DMacks 18:44, 13 March 2007 (UTC)

Looks like it's by Samuel Butler (novelist). A hen is only an egg's way of making another egg.

Life and Habit, ch. 8 (1877) Skittle 20:41, 13 March 2007 (UTC)

Atomic Model by Phillip Lenard in 1904

There was an atomic model made by phillip lenard in 1904. This particular atomic model had neutrons and protons "stuck" into pairs which were called Dynamides. Ring any bells? I have tried the internet to no use. Does anyone have any information on this model? Thanks in advance.

Cheers-----Howzat11 10:24, 13 March 2007 (UTC) 10:23, 13 March 2007 (UTC)

That would be Philipp Lenard. Google finds a little[1][2]. If you read German: [3][4][5] (or run it through http://translate.google.com/). Weregerbil 13:14, 13 March 2007 (UTC)

Which way is up on a technical drawing?

Apart from the text, is there any formal way in which up and down are indicated on an engineering drawing?

ta,

Adambrowne666 11:55, 13 March 2007 (UTC)

That's pretty funny. No not really. I imagine architects and so on do assume that up is towards the top of the paper, but in the case of a drawing of a ball bearing (etc) it is meaningless. Cars are drawn on a grid, and each company will define coordinate systems to indicate which way is up, typically Z+, or Y+. Cheers Greglocock 12:01, 13 March 2007 (UTC)

Usually, the Z axis is used for 'up' and 'down' in technical drawing/CAD applications62.25.96.244 14:03, 13 March 2007 (UTC)

Most 3D CAD applications will draw a little co-ordinate graphic that shows arrows in the directions where X, Y, and Z are "increasing" and this graphic will rotate with the object as you change your point-of-view. But generally, when printed, whatever is logically "up" is shown at the top of the page.

Atlant 14:57, 13 March 2007 (UTC)

Ok, thanks very much for the answers. Greglocock, you say 'up is towards the top of the paper', but that's a circular answer, surely - how does the builder know what's the top of the paper? As you say, the z axis shows which way's up - how about back in the days of blueprints, or even earlier - was there some accepted mark, an arrow or something? By the way, this is research for a bit of silly science fiction I'm writing, to 'explain' how a building came to be built upside down... Adambrowne666 10:44, 14 March 2007 (UTC)

That's why I said it was funny. On an architect's drawings I don't remember seeing an explicit "This way up" sign. When we used to make a drawing we'd put a symbol in there to indicate whether it is first anngle or third angle projection, but that still doesn't tell you which way is up, relative to gravity. Be very careful about Z is up - in the aircraft industry Y is up. Cheers Greglocock 11:28, 14 March 2007 (UTC)

If it's any help to you, it was widely rumoured at Stevens Institute of Technology that the new chemistry building (ca 1975 or so) was built rotated 180 degrees about its Z-axis. The rumour was that the foundation forms were set incorrectly and the foundation was poured before anyone noticed. So they decided the cheapest "get well" was to build the building oriented with its foundation. I have no idea if it was true or not.

Atlant 12:01, 14 March 2007 (UTC)

Thanks all for taking the time to answer Adambrowne666 22:08, 15 March 2007 (UTC)

Spiriling Mathematical Vortex Phenomenom

Hello, and thank you for your time.

I am trying to find information about including the name of a naturally occurring phenomenon which I saw once and I know it is somewhat well known. This is a scientific/mathematical phenomenom, nothing to do with drugs, religion, etc.

In short, it is a kind of spiriling vortex, cone shaped, made up of geometrical shapes. A bit like a tornado made up of transparent leggo blocks.

Further description: Imagine an ice-cream cone with the bottom chopped off, except the 'cone', the solid part was made up of non-connected geometrical/mathematical shapes, with spaces in between. It was spinning slowly, and was transparent in that the geometrical shapes seemed to be made of yellow light.

There is a name for this thing, other people have seen it, (I even saw it in a VISA card TV commercial but didn't manage to record it in time) but if you go looking for "spiriling mathematical vortex" on the net you get a million hits about scientists discussing the movement of particles in vortexes, I can't find it in the mess, hence asking you guys who might know about it.

What I mean by geometrical/Mathematical shapes was something like the 3d blocks in the game 'block-out', like 3d tetris blocks, all different, but they all had some relationship with each other, so the whole thing gave the impression of forming a completed mathematical formula, sort of like if you represented the equasions of relativity geometrically.

If anyone knows the name of this thing or anything about it I would appreciate some info, here or via email which I am happy to include here.

Thank you. 198.142.12.199 15:41, 13 March 2007 (UTC)

Is this the second posting of the question? I don't know. [Mαc Δαvιs] (How's my driving?) ❖ 18:16, 13 March 2007 (UTC)

Your description of the phenomenon leaves a lot to be desired! It doesn't sound like anything natural - something on a TV commercial could just be some kind of computer graphic thing with no relation whatever to anything 'real'. Under what circumstances would one see this thing? Is it a weather phenomenon? SteveBaker 23:09, 13 March 2007 (UTC)

blucat: No, this is not the second posting of the question.

I thought I went into enough detail to pinpoint it. It IS something natural, seen by enough reputable scientists (mostly mathematicians to have given it a name), and featured on the TV show Millennium (with Lance Henricsen, as one of the urban legends which he investigated), and also his TV commercial VISA Card commercials, one of which gives a computer sim and the name.

Under what circumstances would one see this thing? That's a toughie. I can only tell you that I was listening to a talk on pure mathematics by Adam Spencer and he managed to get my state of consciousness into a previously unprecedented state, and suddenly in my 'mathematical spiritual state' I saw the thing. It was a big thing for me, equal to anything I have had but scientific in nature. God dam, it is a somewhat well known Urban Legend, with a name, and featured in 'Millennuim' and the VISA card commercials. Can it be so hard to track down?

Maybe we should just get some hackers to pilfer all the VISA Card commercials and solve this.

Anyway, thanks for the reply, email me at blucat@optusnet.com.au, blucat, 198.142.42.20 12:30, 10 April 2007 (UTC)

Cheers,

blucat

Pinewood derby friction

I am trying to work out the physics for determining the coefficient of friction for different pinewood derby lubricants using a rig like the one pictured here. On a rig with no eyescrew (the weight hangs straight down), what is the normal force, $N$, exerted against the axle? Without the weight, it would simply be the mass of the wheel+wooden ring assembly times the acceleration due to gravity, $N=m_{w}g$. Adding a block of mass $m_{b}$ to the end of the string creates a tension, $T$, in the string that pulls the edge of the wheel straight down, so that as far as I can see, no component of the tensional force is directed towards the axle. At static equilibrium, I assume $T=m_{b}g$, and when the block is allowed to drop freely, $T<m_{b}g$. My question is, does the normal force on the axle increase when the block on the string is added, and if so, by how much? Is the amount different for static equilibrium vs. free fall? (I took physics 101 about 20 years ago but can't quite recall how this works.) dryguy 16:16, 13 March 2007 (UTC)

Consider a section of the string wrapped around the axle that subtends an angle $d\theta$ of it. The string is curved, so the two tension forces on it (each of magnitude T) do not precisely cancel but leave a resulting force directed radially inward that is T per unit angle (the resultant force is $T\sin d\theta =Td\theta$). This makes sense: if you integrate around, say, the top half of the wheel, you get a horizontal force of 0 and a vertical force of $\int _{0}^{\pi }T\sin \theta \;d\theta =T$, just as it should be to hold up whatever the string is holding. You should note, though, that the wheel and the string touching it are never moving with respect to one another, so the normal force is not of much importance; even without friction, the string being attached to the wheel (as by the pin) is enough to hold it in place (up to rotation). Does that help? --Tardis 17:45, 13 March 2007 (UTC)

You speak of the force between the string and the wheel, but I am focused on the force between the wheel and the axle, and how much this force increases when the string pulls down on the edge of the wheel. I have spoken to a mechanical engineer who tells me that the downward force on the axle, $N$, has to increase by the amount of tension, $T$, applied by the string to the wheel, and that there will also be a torque, τ $=Tr$, where r is the radius of the wheel. Thus, $N=m_{w}g+T$. Is this correct? dryguy 19:52, 13 March 2007 (UTC)

Sorry! I took your "axle" to just mean "wheel". As for the force on the axle, we know that the total force must be the force on the wheel (already derived) plus the weight of the wheel. But as for the normal force, this is somewhat harder; a wheel, unlike a string, can have nontrivial internal stresses and might hang on the "edges" of the axle (thus using only tangential forces) or might rest on the top or bottom (using a positive or negative(!) normal force). So the question can't be answered in general; I imagine (though have not proven) that assuming the simplest, most uniform wheel and axle possible would result in the total normal force you've given (but, again, it's spread out over the surface of the axle and does not have a single value). --Tardis 15:31, 14 March 2007 (UTC)

Thanks! Since the purpose of deteriming the force is to calculate the coefficient of friction, I used the word "normal" which is what my Physics 101 textbook uses (Tipler), but in the book the example is for a block pressing on a flat surface. Here, it may be inaccurate to speak of the force as a "normal" force, in the sense of "perpendicular to a surface", since we don't have a flat surface, nor do we have a single point contact of a plane with an arc surface. What I think matters for friction is that the frictional force opposing the rotation of the wheel will be proportional to the total force pressing the surfaces together, which I hope is accurately given by $N=m_{w}g+T$. Otherwise, when in static equilibrium, the forces pushing up against the wheel up wouldn't balance those pulling down on the axle, if I understand correctly? All this is assuming that the bore hole in the wheel has a larger diameter than the axle so that there are no other "binding' forces at the axle/bore interface. dryguy 20:04, 14 March 2007 (UTC)

I don't think that you can in general rely on the total force being equal to the total force relevant to friction: the normal force is still relevant here, it's just that which direction is "normal" is different at every point. Moreover, forces are vectors, and so do not sum directly; consider someone standing on two opposite walls of a narrow room. By pushing hard against each wall, the normal force may be made large enough for the friction to support their weight, even though those normal forces obviously cancel out since the total force on the person is just the friction! So suppose your axle was heated slightly (perhaps by the very friction we're addressing) and expands, so that it's exerting quite a large pressure on the wheel; the friction may be quite large there. Or if the axle is too small and the wheel's point of contact moves on it, it may be that there is very little frictional loss (even if a notable amount of friction; see mechanical work) because the wheel is stationary (with respect to the axle) at the point of contact. Even subtler things, like the wind pushing the wheel from the side (so that it "hangs" on the edge of the axle) may reduce the normal force (if $\mu >1$) by causing friction to do part of the work of holding the wheel up. You can see why this is not a common elementary physics problem! I don't think you'll be able to solve it without making some further study of (or assumptions about) the wheel/axle setup. --Tardis 19:09, 15 March 2007 (UTC)

Solution for world hunger

Hi ! I came across this interesting & significant question in a text book of microbiology, by Ronald M Atlas , and I am really looking forward to your views on it......The question goes like this : " Can recombinant DNA technoogy help create a microbial strain that will solve World Hunger " Thanking you in anticipation,--Pupunwiki 16:45, 13 March 2007 (UTC)

Sure. It could evolve into something lethal and wipe out most of the human race, leaving plenty of stored food for the survivors. Clarityfiend 17:08, 13 March 2007 (UTC)

Before the Green Revolution, Isaac Asimov created a fictional future in which special strains of yeast cells were used to produce essentially all human food. I'm not sure if you could help poor and hungry people by creating new strains of bacteria that would enhance nitrogen fixation near the roots of various food crops. --JWSchmidt 17:14, 13 March 2007 (UTC)

could you be a bit more specific with the type of microbial strain? if not all i can say is that we already have a solution to world hunger... just watch the movie soilent green Maxx4444177 17:18, 13 March 2007 (UTC)

You might be interested in Wikipedia:Reference desk archive/Science/2006 October 7#Are there obstacles to industrial-scale production of cultured animal tissues for food?. Look at my post at the bottom. As I remarked there, one of the biggest problems is that even IF this would work in practice, the large impact of subsidies in the developed world along with consumer resistance (even if it's used as feedstock rather then consumed directly there will be a hell of a resistance IMHO, especially if it's GM) means it may not be feasible in reality. Nil Einne 20:37, 13 March 2007 (UTC)

It's not microbial, but I like a suggestion made by the sci fi writer Larry Niven - use recombinant DNA technology to give humans gastrointestinal systems as robust as those of scavenging dogs - the definition of food would become much broader for such people - they could eat rotting meat without harm ... some dogs are even coprophagous, so there's a rich source of food there too - though you'd better remember to use breath freshener after your meals... Adambrowne666 22:03, 13 March 2007 (UTC)

World hunger is more of an economic/political problem than a simple scarcity of foodstuffs, as the existence of a concurrent world obesity problem attests. --TotoBaggins 22:34, 13 March 2007 (UTC)

It's about distribution as well as scarcity. This is a rather complicated issue, as you'd expect. [Mαc Δαvιs] (How's my driving?) ❖ 23:01, 13 March 2007 (UTC)

So what we really need is little microbial truck drivers, economists and politicians? Clarityfiend 03:14, 14 March 2007 (UTC)

“ If your model for solving world hunger is one faculty member and three or four graduate students, then you're wrong. ”

-Stanford University President John L. Hennessy

Just thought I'd share. Nimur 05:51, 14 March 2007 (UTC)

tungsten heavy alloy

Can someone supply me with a compression (not tension) stress versus strain curve (or tabular data) for tungsten heavy alloy (such as 93W-5Ni-2Fe or similar)? Compression strength versus temperature (room temperature to 500 degrees farenheit) would be an added bonus. Thanks 64.154.26.251 18:36, 13 March 2007 (UTC)

A Google Scholar search suggests that these charts may exist. This link suggests a specific journal publication (MS&E `93) with that data. See also [6]. Hope this helps, Nimur 06:05, 14 March 2007 (UTC)

Weight Loss

For every 10 pounds one loses, how much is fat and how much is muscle on average? Is it any different for one who weightlifts and has protein shakes?

that is most likely so. the percentages of both vary on multiple variables such as weight lifting and protein shakes as you mentioned. it also varies based on the BMI and the BFP of the individual. but i belive i heard somewhere that for about every 10 lbs of fat you lose there is approx. 1 lb of muscle gained.(i think but am not sure) Maxx4444177 18:49, 13 March 2007 (UTC)

It also likely depends on type/variety of exercise, rate of weight loss, total composition of diet (beyond just protein), among other things. Frankg 19:12, 13 March 2007 (UTC)

The quicker you want to lose weight the more relative muscle mass you tend to lose. It can be compensated by a good diet and weight training. It is possible to lose weight and keep your current muscle mass or even increase it but this requires very slow weight loss. PvT 19:28, 13 March 2007 (UTC)

When beginning a weight training program, you may actually gain weight because muscle mass can increase faster than your body will consume fat. Losing fat/weight is best accomplished through aerobic exercise (running, jogging, etc.) which builds less muscle by comparison. Protein shakes are good when weightlifting, but when not accompanying any form of exercise, drinking them is just trading one calorie source for another, may as well eat french fries. Atropos235 23:26, 13 March 2007 (UTC)

I think that's kind of misleading - I've read a number of studies, testimonials, etc. that indicate that increased protein intake during a period of a caloric deficit provides for less muscle loss, with all else being equal. Certainly protein has a higher thermic effect of feeding compared to french fries. Frankg 07:01, 14 March 2007 (UTC)

fullname

can u tell me the fullform of the cell-line HeLA?? —The preceding unsigned comment was added by 59.95.225.76 (talk) 19:17, 13 March 2007 (UTC).

named after Henrietta Lacks in 1951 from a cervical carcinoma caused by human papillomavirus 18 (HPV18). GB 21:25, 13 March 2007 (UTC)

HeLa. --JWSchmidt 23:13, 13 March 2007 (UTC)

Oxygen-15

What fraction of ¹⁵O decays by positron emission and what fraction by electron capture? The Korea Atomic Energy Research Institute's nuclide chart lists only electron capture, but ¹⁵O is used in positron emission tomography. This document from Washington University's School of Medicine says that it decays purely by positron emission. Icek 19:39, 13 March 2007 (UTC)

The β+ decay mode is the only one listed in Nubase2003. DMacks 21:22, 13 March 2007 (UTC)

The document from Washington University also states explicitely 100 % β+. I understood this to be a synonym of positron emission, but Nubase2003 defines it as both electron capture and positron emission. Icek 00:58, 14 March 2007 (UTC)

The electron capture and positron emission pages talk about using the relative energies of the parent and daughter nuclei to figure out whether both modes are possible or (if the energy difference is < 1.022 MeV) only electron capture is expected. Just need to know the relative energies of ¹⁵O and ¹⁵N. DMacks 00:17, 15 March 2007 (UTC)

Both modes are energetically possible (the energy difference is 2.754 MeV), but I'm asking for the ratio. Icek 16:10, 15 March 2007 (UTC)

Ear Bud Pain

Why does it hurt after wearing ear buds for a while? Any suggestions on allevating the pain or alternative ways to wear my ear buds? —The preceding unsigned comment was added by Juliet5935 (talk • contribs) 20:45, 13 March 2007 (UTC).

Your ears are sensitive and the earbuds are pretty hard! You'll get used to them if you wear them enough, at least that's what my experience with headphones is. [Mαc Δαvιs] (How's my driving?) ❖ 21:30, 13 March 2007 (UTC)

You might try getting different headphones. Some are made out of softer material or are made to fit the ear better. You're just feeling the result of having something hard in your ear pressed against your skin. --24.147.86.187 00:09, 15 March 2007 (UTC)

Semen color/composition

What is it, or lack of it(s?) in semen that cause it to be colored white, yellow, or gray? [Mαc Δαvιs] (How's my driving?) ❖ 21:30, 13 March 2007 (UTC)

I don't understand what's curious about it? Have you read the article on seminal fluid? Vespine 22:45, 13 March 2007 (UTC)

The article does not state what chemicals are responsible for the colors. [Mαc Δαvιs] (How's my driving?) ❖ 22:59, 13 March 2007 (UTC)

Then my guess it is, as you say, the lack of any substance with a color which makes it neutral. Vespine 04:56, 14 March 2007 (UTC)

Plotting Titration Curves

I have some titration data I collected in a lab and would like to use it to add a proper titration curve to the Titration article. Everything I did is in Excel, but I'm not sure if taking screenshots of a graph in it is the best way to do things, are there any free graphing utilities that are usable in Windows that could give me a better plot, maybe even export to SVG? Atropos235 23:12, 13 March 2007 (UTC)

I put a copy of this question at Wikipedia:Reference desk/Computing#Plotting Titration Curves. If you want to email me the excel file I can make a graph on my Macintosh. --JWSchmidt 23:23, 13 March 2007 (UTC)

From Excel you can export the file to HTML. The chart will turn up as a .gif image in a subdirectory. From here you can open the picture in the Microsoft office picture manager, or pixia or other picture editor and export it or save it as .png format which is acceptable to Wikipedia. In the past I also used PowerPoint for this purpose as it can save directly to .png format. You can copy and past the chart to PowerPoint. GB 01:26, 14 March 2007 (UTC)

Converting the graph in Excel to a raster image is trivial for me, I would like to make it look better than Excel can, and/or save it in a vector graphics file. Atropos235 01:46, 14 March 2007 (UTC)

Gnuplot is available for many platforms, and can read many data file formats and also is capable of SVG export. See [7] for more information as well. Nimur 05:05, 14 March 2007 (UTC)

Mexican spider called El Conchlo

I was recently in Yelapa, Jalisco and my host family showed me a huge spider which they called El conchlo. If its legs had been completely unfolded it would have been 15 or more inches across. This spider, if it even is a spider, is well loved by everyone, as it eats scorpions. The conchlos are reclusive, and the only reason we saw this one was because the water heater had been replaced and it was evicted temporarily from its home and was singed a little by the plumber. This was not a tarantula, as its legs were smooth and quite thin. It seemed to have furry antennae like a moth, though it was hard to see in the semi darkness. Does anyone know what this animal is? "Conchlo" does not show up in any Spanish dictionary I've consulted, and I can't find a picture matching this beast searching "giant spiders". Thanks. 66.191.126.113 23:56, 13 March 2007 (UTC)

Could it be a type of Recluse spider or camel spider (though I think the latter are called matevenados ("deer killers") in Mexico)? Rockpocket 05:11, 14 March 2007 (UTC)

If not, you could ask for advice at WikiProject Spiders. Rockpocket 05:14, 14 March 2007 (UTC)

Here it is (maybe). It's not a spider, but it eats anything. [8] Sort of a scorpion-eating scorpion-like creature. --Zeizmic 16:05, 14 March 2007 (UTC)

Also known as a camel spider as proposed above. Rockpocket 00:39, 15 March 2007 (UTC)

This is actually an Amblypigid, or Whip Spider. The canclo is (Acanthophrynus coronatus), and a link with photos can be found at the bottom of this page: [9]