Wikipedia:Reference desk/Science

March 12

pH value from dissociation constant

This is based on a homework question with specific values, but I am asking only for general formula.

If I know the acid dissociation constant (pKa) and the concentration of a weak acid, how would I find the pH? How do I find the pH after adding a certain volume of a strong base? − Twas Now ( talk • contribs • e-mail ) 00:58, 12 March 2007 (UTC)

Take a look at Henderson-Hasselbalch equation

${\textrm {pH}}={\textrm {pK}}_{a}+\log _{10}{\frac {[{\textrm {A}}^{-}]}{[{\textrm {HA}}]}}$

From the pKa page the ionised acid and H+ concentration will be the same, so you end up with pH+pH=-log10(concentration of a weak acid)+pKa.

${\textrm {pH}}=({\textrm {pK}}_{a}-\log _{10}{[{\textrm {HA}}]})/2$

GB 02:18, 12 March 2007 (UTC)

Thanks. I guess what confuses me is how do I determine [HA] and [A^-] for a given weak acid (and its conjugate base)? − Twas Now ( talk • contribs • e-mail ) 03:09, 12 March 2007 (UTC)

It's really very simple. All you need to do is set up an ICE table for the ionization equilibrium of the acid, i.e. HA ⇌ A^- + H⁺ :

	[HA]	[A-]	[H+]
I	c0	0	0
C	-x	+x	+x
E	c0 - x	x	x

Because $pH=-\log {[H^{+}]}$, and you can tell from the table that when the ionization is over [H⁺] = x, then $pH=-\log {x}$. So, your job is to find x.

The equilibrium constant expression for the ionization is:

$K_{a}={\frac {[H^{+}][A^{-}]}{[HA]}}$

Substitute the concentrations with the values found in the last row of the ICE table.

$K_{a}={\frac {x.x}{c_{0}-x}}$

Now plug in the specfic values for c₀ and K_a ($K_{a}=10^{-pK_{a}}$) provided in your question, then solve for x, and you're done!

If you do some math, you can quickly figure out that the relation GB provided is only a different (and handier) way of expressing K_a, especially when you're working with buffer solutions.

Now for the second part of your question: when you added a certain quantity of a strong base, the OH^- ions you just added will react with some of the H⁺ in solution. From the OH^- - H⁺ reaction stoichiometry, you can calculate the number of moles of H⁺ that have disappeared and how many moles are left. Then you can find the new concentration of H⁺ ions (keep in mind the change in volume) and the new pH. —LestatdeLioncourt 14:45, 12 March 2007 (UTC)

Tin can water battery sparking experiment thing :-)

I am trying to find if there is an article or other information about a physics set up of a water spark experiment.

Basically you have a tank of water with 2 holes in it. Water falls out each hole and falls through two cylinders and into two tin cans. Each tin can is wired to the opposite cylinder (not the one its own water falls through). As the water falls it appears a charge builds up and high kv spark can be generated across points that are connected to the tins. There are no other components or sources of power. I saw this in a movie of a lecture and wanted to read about it. As the charge builds up it causes the water falling to repel itself or something, such that as the charge builds up the trikles of water change from being smooth and straight to rain drop like and then when the energy is discharged it instantly goes back to smooth and straight.--155.144.251.120 02:42, 12 March 2007 (UTC)

Here it is. [1] --Zeizmic 13:27, 12 March 2007 (UTC)

And our article on it is here, though it's a tad stubbish at the moment. GeeJo ^(t)⁄_(c) • 07:32, 15 March 2007 (UTC)

Force of Impact?

Here's a question I've asked in the talk page of Impulse and I began to wonder if it would not be better of me to ask it here, so I quote it verbatim.

Often one hears the term "Force of Impact". Say you can calculate/estimate the impulse of an impact but you want to estimate (perhaps) the maximum force of collision, or possibly the average force of the collision, or maybe even the average force for the top 25% of the most forceful moments of the collision. Is any of that information relevant? I'm interested in the relationship between the fracture strength of materials and "how forceful" an impact an object of said material can take. It would seem that Impulse is a desired quantity to know, but what else should I know? IIRC to get average force, I just divide divide the impulse over the time it takes for the the impact to take place. But how would one estimate this time? How would I estimate the average force imparted by one billiard ball on another over the lifespan of the impact, which I cannot estimate with the unaided eye. How high could I drop a billiard ball in a frictionless environment from a building before cracks of a certain size develop on its surface (I.E. the force imparted exceeds locally the fracture strength of the material the billiard ball is made from but it does not fracture the ball). How do I estimate how much effect the ground chosen for the ball to impact has on this? If the fracture strength of the ground is quite low, energy from the impact will be dissipated by "flakes" of the ground being thrown outward, and it would seem that also needs to be taken into consideration.

It seems methods to estimate information is relevant and related to the article, but no description or references are included in the article. What quantities are these and how are they measured or estimated?

I'm not a physicist and I wouldn't even know where to begin to look (other than, say, research into stuff like bicycle helmets).

Might any of you be any help on this? I'm interested in any comment, even if you might consider it to be off-the-wall. Thanks.

Root⁴(one) 03:58, 12 March 2007 (UTC)

I think it is pretty rare to do such experiments or observations in the time-domain. The impact duration for a "mostly elastic" collision such as a billiard ball is extremely short. A few high-speed photography experiments have been done (this guy from MIT was famous for his photos of things colliding). My guess is that it is easier to measure the peak force than the impact time. You could then model the time-varying force with a Gaussian function force-vs.-time relationship based on the measured peak-force (or invent a different theoretical model). Then, you could integrate for the total impulse (momentum transferred).

As far as the material strength, you might look at bulk modulus or Young's modulus, which are useful for calculating solid object deformation as a function of force. Naturally, more sophisticated analysis can be performed per material, with loss of generality, to account for nonlinear, anisotropic effects, for example.

Here is a photograph of a golf-ball at the instant of impact. Clearly deformation occurs. If I recall, this image is taken in a dark room illuminated by a single strobe-flash, so the image exposure is on the order of 10 micro-seconds. Nimur 05:03, 12 March 2007 (UTC)

Thanks, your reply indeed does help, although it appears to mean I may need to learn/re-educate myself on a few maths I can't say I know at present. The Young's modulus article was quite insightful, as I had forgotten how important the cross sectional area is to what I'm trying to learn.

If you wanted to know what got me started on this road, its research into this "5 pounds to break a collarbone" myth. It is true that it does not take much force to break the clavicle, or rather, pressure solely exerted on the clavicle itself, but 5lb == 22 Newtons seems awfully low. however, if that 22 Newtons is spread over a small enough area on the clavicle, this maxim may be more true than I realize.

I also was involved a few months back in a minor accident on a bike that separated my shoulder, and I've often wondered how to demonstrate, in terms of physics, how and why it happened, which recommendations for prevention are better and why they are better in certain situations. I already know what I should have done, but knowing the physics behind why the technique works and in which situations the technique is better or worse, I think, would be helpful, and would help put my mind to rest as to what truly is good advice. I'm not sure how I could contribute this information to Wikipedia, as I'm sure this would qualify as "original research", but maybe at least I could use it to help defend against bad information and advice. At least maybe I could put in on a blog somewhere if I choose to set one up.

But given how complicated the mathematics appears be for simple collisions of "anisotropic" materials, I may need to research this for a while. I seriously doubt I'm the only one to have considered these questions, so hopefully with enough research I can find solutions to problems already answered relating to the physics of protecting the shoulder.

Root⁴(one) 11:58, 12 March 2007 (UTC)

In the special case of a ball or cylinder bouncing off a hard plate the answer is complex.

Not very surprisingly Timoshenko covers this problem in "Theory of Elasticity".

Unfortunately I didn't copy all the right equations down, so I'll just solve the simpler case of a steel ball bouncing off its twin. If you think about that case it is likely that this is also the same as the steel ball bouncing off an infinitely stiff flat plane.

The time of the contact is

t=2.94(1.25*sqrt(2)*pi*rho*(1-nu^2)/E)^0.4*R*v^-0.2 eqn 244

R=0.031 m

v=3.132 m/s

rho=7843 kg m-3

E=210*10^9 N m-2

nu=0.3

t=0.1493 ms

The average force, F during the contact is 2*m*v/t (ie the change of momentum divided by the time)

F=42 kN, ie a little over 4 tons force.

Timoshenko actually gives a direct solution for a ball on a flat plate, and the peak force rather than the average force, but it is spread over two pages. This solution assumes that the contact time is long compared with the period of the lowest modes of vibration. Greglocock 01:06, 14 March 2007 (UTC)

Artificial Sweeteners

Can chronic fatigue be from overuse of artificial sweeteners? I am 22 years old, in great health, sleep well, and take my vitamins, but I am tired all the time. Could it be from the 36 packets of splenda I have everyday?

Splenda#Safety does not list anemia or fatigue as a side effect. You might suffer from mild anemia, unrelated to your splenda consumption, that could be due to genetics, diet, or some chronic medical condition. This causes sleepiness and exhaustion. You might consider consulting a physician. Sometimes, the best solution is a change in diet (more iron-containing, green leafy vegetables and legumes, and more red-meat), and sometimes dietary supplements or medicine is necessary. See also Iron deficiency (medicine). P.S., this is not medical advice, consult a physician, etc. etc. Nimur 04:52, 12 March 2007 (UTC)

As Nimur said, you might want to consult a physician. However, fatique can come from many things, including the room being too hot / cold, or a non-fixed sleeping schedule (something a 22 year old is more likely to engage in). --Wirbelwindヴィルヴェルヴィント (talk) 04:58, 12 March 2007 (UTC)

doh. I think sugar substitutes may trigger the same insulin response as sugar. Jsut a guess and certainly not medical advice but maybe that much splenda is giving you the sugar crash without the prior rush. Use regular sugar for a week and see if it changes. --Tbeatty 05:19, 12 March 2007 (UTC)

I thought splenda is safe for diabetics because it doesn't trigger the insulin response? --Wirbelwindヴィルヴェルヴィント (talk) 05:28, 12 March 2007 (UTC)

Chronic fatigue can be a sign of a lot of things. That is, you could potentially have a real problem. Visit a doctor, and they'll be able to check if anything is wrong. Even if you don't have one of the really big problems, they will also be able to get a much better idea of what is causing your fatigue than we can, so they are more likely to be able to help you cure your fatigue, which I'm sure you see as a positive thing. Please, see a doctor. Skittle 16:56, 12 March 2007 (UTC)

You say you sleep well. Does this mean you fall asleep readily? It could be that you are not getting enough sleep and hence feel tired during the day. I suggest trying giving up all caffeine for several weeks. At first you will feel worse due to withdrawal, but after a few weeks you will all the time feel as alert as if you'd drunk strong coffee. I know, I've been caffeine free for years. I'd thoroughly recommend it. —The preceding unsigned comment was added by 62.253.53.39 (talk) 21:21, 12 March 2007 (UTC).

Feeling tired all the time could be a symptom of diabetes, so you must see a doctor about this. Untreated diabetes causes blindness, loss of limbs, etc. 62.253.44.18 19:54, 13 March 2007 (UTC)

If someone were to ask you, what do you think a potential side-effect of artificial sweetners would be, chronic fatigue sounds about right. Sugar is basically pure energy, and a substance that mimics the taste of sugar but isn't quite the same sounds like 'tainted fuel' to me. Vranak

My friend has Chronic fatigue and he has found the Gluten makes it much worse. Try going gluten free for 2 weeks, it really helped him. I know this doesn't really answer the question. CaptinJohn 12:30, 14 March 2007 (UTC)

Ionization of acetic acid

How much does acetic acid to ionize in water? For example, if you have one mole of acetic acid, would it ionize into only a small amount of CH₃COO^- and H₃O⁺ (e.g. 5% or 0.05 moles each), or would it be much more (e.g. 95% or 0.95 moles of each)?

I know acetic acid only ionizes partially, but both 5% and 95% are partial. So when chemists refer to "partial ionization", what is their threshold for "partiality"? − Twas Now ( talk • contribs • e-mail ) 05:43, 12 March 2007 (UTC)

I think the pH might be a starting place. The pH specifically gives the concentration of the ionized acid, (given in a logarithmic scale described in the article). You can then compare with the total molarity of the solution to determine the amount of "partiality." Actually, that article contains a pretty useful example here. Nimur 06:03, 12 March 2007 (UTC)

Also, directly from the acetic acid article, the constant is given: "A 1.0 M solution (about the concentration of domestic vinegar) has a pH of 2.4, indicating that merely 0.4% of the acetic acid molecules are dissociated." Nimur 06:09, 12 March 2007 (UTC)

Thank you. I understand pH, but the ionization percentage is not directly evident from a pH value. The second comment definitely helps though! Thanks. − Twas Now ( talk • contribs • e-mail ) 06:14, 12 March 2007 (UTC)

Yes, it's not directly evident, but it can be solved with the equations (as in the example above). Good luck! Nimur 06:36, 12 March 2007 (UTC)

How much should we trust in sunglasses?

As I know, it is dangerous to wear sunglasses without uv shielding, because the pupil will grow bigger to let more light in, so it would let more uv radiation in. So what is the most simple (or lest expensive) experiment to decide whether our sunglass does have uv protection or not? --V. Szabolcs 07:55, 12 March 2007 (UTC)

AFAIK glass is mostly opaque to UV anyways (that's why they need to use quartz to make Germicidal lamp), but most plastics are not, and should have a UV coating on it. --antilived^{T | C | G} 08:14, 12 March 2007 (UTC)

An easy way to determine the existance of UV shielding would be using a black light or a halogen light with its glass UV filter removed and some flourescent substance (glow in the dark toys, some especially bright t-shirts etc.), and compare the normal brightness to the brightness under the sunglasses. But any more than that I think you will have to visit an optometrist where I've seen a machine that does exactly what you said. --antilived^{T | C | G} 08:27, 12 March 2007 (UTC)

Oh man, you've got me all scared to ware my sunglasses now; and I need 'em man! Really I do - how else am I gona look cool? Think outside the box 12:45, 12 March 2007 (UTC)

By rights, you ought to repeat your experiment at several other ultraviolet wavelengths rather (UV-B and full-spectrum UV-A) rather than just the near-UV (360 nm light) emitted by blacklights.

Atlant 15:28, 12 March 2007 (UTC)

I heard recently that most modern mobile phone screens will turn black when seen through some sunglasses. Does it only prove that the glasses have some sort of polarization, or does it also have something with uv shielding? --V. Szabolcs 16:13, 12 March 2007 (UTC)

The light passing through liquid crystal displays definitely becomes polarized, but unfortunately, usually not at the same angle as that admitted by polarized sunglasses (which leads to people outdoors holding their heads tipped at a 45 degree angles to look at their laptop screens). The effect has nothing to do with UV light.

Atlant 16:58, 12 March 2007 (UTC)

If in Britain, I would look for the little sticker that told me they met EC or British Standards, and the one saying they blocked 100% of UVA and UVB [2][3][4]. I imagine the same applies elsewhere in the EU, and similar in the US. Skittle 16:52, 12 March 2007 (UTC)

How to add fat in raw milk

AS I WAS READING THE TEXT THE QUESTION WAS RAISED HOW TO REDUCE FAT, BUT I WANT TO KNOW HOW FAT CAN BE ADDED IN COW MILK THAT CAN BE INSTANTLY SOLUBLE OR MIXED. —The preceding unsigned comment was added by 203.101.172.199 (talk) 13:52, 12 March 2007 (UTC).

You can always add dairy creamer, thus putting back what was taken out. Root⁴(one) 14:15, 12 March 2007 (UTC)

The key question is how to keep the added fat from separating back out again. See homogenization (what a pathetic article!) and emulsification.

Atlant 15:25, 12 March 2007 (UTC)

The cream in whole (raw) milk naturally separates from the aqueous phase and rises to the top. Homogenisation only provides a temporary solution because the fat will separate out again given time. Hexane2000 16:09, 12 March 2007 (UTC)

Sure, but the milk will usually sour before commercial homogenization fails.

Atlant 16:54, 12 March 2007 (UTC)

Bizzare

I found this picture on the internet and I have absolutely no idea what it is. It looks like some sort of animal, having a body and arms, but I don't know. Maybe someone here knows.

File:BizzareThingy.jpg

I didn't take the picture myself, so i don't know where it is indeigenous to or anything like that. Thank you for your help. schyler 16:26, 12 March 2007 (UTC)

Jesus! After looking at it for a while trying to figure out what it is, I've decided that it is a bird. The photo is taken from behind (i.e. that pink thing at the top is the back of its head and those little things on the sides are wings). I'm no bird expert, so I don't know what type it is. GhostPirate 16:39, 12 March 2007 (UTC)

I agree, looks like a baby bird seen from behind. (thanks for switching my perception GhostPirate, that was disturbing) Skittle 16:42, 12 March 2007 (UTC)

Wow. Okay. What strange lookig bird! schyler 20:32, 12 March 2007 (UTC)

Maybe because my dad used to keep doves and pigeons, but I saw it as a bird right away. It looks like it could be a baby vulture from the back, before the feathers grew out. --Wirbelwindヴィルヴェルヴィント (talk) 23:53, 12 March 2007 (UTC)

You can see the very tip of the beak if you look closely --VectorPotential^Talk 00:08, 14 March 2007 (UTC)

OMG! (oh my gosh!) it looks like a person (possibly a baby) with no face!--Lerdthenerd 09:52, 14 March 2007 (UTC)

It is a baby bird, but difficult to tell which species. Might be chicken, turkey, any similar domesticated bird. --Nirajrm ^{talk ||| sign plz!} 22:40, 14 March 2007 (UTC)

Moden physics

if the probability density at certain points for a particle is zero, does this imply that the particle cannot move across such points—Preceding unsigned comment added by Hjchen1010 (talk • contribs)

No, it just means you can't ever find the particle at that point. To move past such a point or region is a phenomenon known as quantum tunneling. 131.215.159.161 17:35, 12 March 2007 (UTC)

Note that quantum tunnelling is a class of phenomena that involves particles passing through forbidden states under certain specific conditions (generally, allowed states on either side of a thin forbidden zone). -- mattb @ 2007-03-12T19:22Z

It depends on whether the probability density is zero before or after quantum effects are taken into account. While most problems that have a zero p.d. classically have a non-zero function for a quantum particle, it is technically possible to have a p.d. that is also zero in the quantum case, which the particle cannot enter. In nature it's practically impossible (very, very small, but not zero) and the above answers are correct; but it's quite a common thing to have in a homework or exam question (an infinite potential). Spiral Wave 21:28, 12 March 2007 (UTC)

Low pass filter

I gotta implement a Hanning window-shaped LPF. Have I to weighten the magnitude samples only or the phase too? tia —The preceding unsigned comment was added by Ulisse0 (talk • contribs) 17:17, 12 March 2007 (UTC).

If you are concerned about output phase, you must also include those in your specification of the filter design. If not, you don't. Either way, make sure your filter is stable (phase should be greater than -180°). Nimur 19:58, 12 March 2007 (UTC)

A window function is applied to the magnitude. A filter designed by windowing the impulse response will typically be FIR with real coefficients, unless you're working on complex-valued signals. Outside of a homework problem or laziness, there's better ways to design a low-pass filter. 24.91.135.162 15:51, 15 March 2007 (UTC)

Fireproofing MDF

For my friend's birthday, I'm going to drill holes in the form of "Happy Birthday Name" into a peice of wood and put matches in all these holes, the idea being that I can light one match and the fire will spread to present the message (in a darkened room). What can I cheaply coat the wood with so it wont burn if the matches burn all the way down and will MDF be suitable? --Seans Potato Business 17:32, 12 March 2007 (UTC)

Just soak the wood in water before you light. Of course, if it's a horrendously long name, you might start a firestorm. --Zeizmic 20:03, 12 March 2007 (UTC)

Lower pitch of voice

Anyone know of something that will lower the pitch of the voice like a thyroplasty but without surgery and at the same time won't cause side-effects on other parts of the body like taking steroids would? Perhaps a chemical applied just to the vocal chords? SakotGrimshine 19:35, 12 March 2007 (UTC)

• <inappropriate suggestions removed to talk page>Edison 16:48, 13 March 2007 (UTC)

I was hoping for permanent. Basically it might be nice if I can get steroids just to go to my voice box and not elsewhere (like my hair folicles on my head). I doubt a rub-on cream would do it. SakotGrimshine 23:56, 12 March 2007 (UTC)

Going to a competent and qualified public speaking or singing teacher would help you find your natural speaking voice, which may well be pitched lower than you currently use it. It won't happen overnight, only with training and practice, but the permanent change would be well worth the effort. JackofOz 02:31, 13 March 2007 (UTC)

I don't think there is a quick/easy solution. I know that men who have undergone a sex-change have a lot of difficulty pushing their voices up in pitch (so they sound more feminine) - and the only thing they can do that really helps is professional voice training. I would guess (although I don't know for sure) that lowering the pitch of your voice would be a similar problem. SteveBaker 23:19, 13 March 2007 (UTC)

Well lowering it is posible if I take anabolic steroids, but those cause unwanted effects to the rest of my body when I only want their effects on my voicebox. SakotGrimshine 12:49, 14 March 2007 (UTC)

Some of you may recall the TV & Movie Star, Rock Hudson?? Among other things, he had a reputation for his deep, "swarthy" voice. I'm only paraphrasing, but his biography describes his initial entry into the entertainment business. Supposedly his agent thought he had the 'looks and the talent' to become a star, but his then "squeaky" voice would be his failing. His agent took him somewhere into the Hollywood hills...the middle of no-where...and made him scream at the top of his lungs, until he could scream no more. Subsequently he had NO voice for a few weeks, but upon getting it back, voila!, he had his legendary deep voice. (Perhaps an MD or, more specifically an ENT Dr. could explain whether his vocal cords were lengthened or shortened.) User: ashley604

Reccomendations for alarm clock

Strange question but does anyone know of an alarm clock available for purchase in the UK that is very loud and doesn't stop unless turned off? I am a very heavy sleeper and normal alarm clocks bleep or ring for a while and then stop, I want one I cannot sleep through! GaryReggae 19:46, 12 March 2007 (UTC)

Turn up the volume and put it far away from your bed so you have to walk to it. Nimur 19:55, 12 March 2007 (UTC)

Google 'very loud alarm clock' and it's hilarious! --Zeizmic 20:00, 12 March 2007 (UTC)

You can set your radio to function as an alarm clock and set it to a really loud volume. Also, set it to a talk radio station, rather than music, because we tend to orient towards voices.

If you have a good (or at least loud) set of speakers on your computer, you can use any of several different programs to act as an alarm clock. You can use whatever sound file is most likely to get you out of bed -- anything from a scream to a recorded threat to "Thus Spake Zarathustra." -Arch dude 21:35, 12 March 2007 (UTC)

If you regularly need an alarm clock then it suggests you are not getting enough sleep. You may be being kept awake in the evening by caffeine. I suggest giving up caffeine and going to bed earlier, you will feel much better after the first couple of weeks of caffeine withdrawal. Apart from that I second the suggestion of buying a clock/radio. I think ones from Argos only cost a few pounds. 62.253.49.0 21:59, 12 March 2007 (UTC)

Sounds like you need The sonic bomb with bed shaker alarm. :) Vespine 22:42, 12 March 2007 (UTC)

I use a $5 analog clock that I got from Goodwill. It takes a single N battery that lasta a couple years. Unfortunately, N batteries are hard to find in the US. Regardless, it is dirt cheap and the alarm is a high-pitched chirp that repeats forever until you turn it off. It wakes me up right away. Radio alarms never work for me unless I turn them up so loud that they wake the neighbors. Also, since most radio alarms plug into the wall, they reset to 12:00 every time power blinks. --Kainaw ^(talk) 00:14, 13 March 2007 (UTC)

My battery powered alarm reset to 00:00 occasionally for no reason :( You could get two alarms, on set a few minuites later than the other, and put it on the other side of the room, so you have to turn both off :] HS7 09:39, 13 March 2007 (UTC)

[5] looks entertaining, as does this, although it appears to be unavailable anywhere. Otherwise, try looking at alarms for the hearing impaired. Skittle 15:42, 13 March 2007 (UTC)

Green Beer

Does anyone know the specific ingredients in green St. Patrick's Day beer and why it results in horrible hangovers? I recall hearing somethign about the interaction of alcohol with dye. Any clarification from anyone? —The preceding unsigned comment was added by 74.12.102.224 (talk) 19:55, 12 March 2007 (UTC).

In general, green beer is just beer with added green food colouring. There shouldn't be any sort of interaction which results in a more severe hangover; any effects are due to excessive consumption – it's a special occasion, right? – and the nocebo effect. TenOfAllTrades(talk) 20:18, 12 March 2007 (UTC)

Exactly. I grew up in our family business, a tavern. We used McCormick Green Food Color. Of course, we would buy the dye in a pack of four colors and so had all sorts of blue, red, and yellow coloring left over that I as a child would divert to various projects... --BenBurch 00:07, 13 March 2007 (UTC)

OK: You can use two bottles of red food coloring to bake a Waldorf Red Cake. What can you do with blue and yellow? - Nunh-huh 00:10, 13 March 2007 (UTC)

Why, dye my sister's dolls hair. (this was not a popular experiment) And I used to dye 7-up odd colors too. --BenBurch 00:25, 13 March 2007 (UTC)

Of course, I should have thought of Barbie's blue "do". Five time science fair winner :) - Nunh-huh 00:57, 13 March 2007 (UTC)

Perhaps the focus on "green" instead of "quality" means that bars can charge premium price for a nasty beer (with green dye). I've found the extremely low quality beers make you feel far worse than higher quality ones. --Kainaw ^(talk) 00:10, 13 March 2007 (UTC)

Maybe it's because you just can't handle the Irish stuff? Nil Einne 20:40, 13 March 2007 (UTC)

Our article on Saint Patrick's Day shows an entire river dyed green--VectorPotential^Talk 00:14, 14 March 2007 (UTC)

Global Warming and Greenhouse Effect

What is the difference between global warming and the greehouse effect? —The preceding unsigned comment was added by 199.2.112.34 (talk) 21:02, 12 March 2007 (UTC).

Check out our articles on Global warming & Greenhouse effect. Simply, the greenhouse effect is one of the main mechanisms that may cause global warming, but not the only possible one. -- Scientizzle 21:08, 12 March 2007 (UTC)

Actually the oceans would be frozen over all or most of Earth's surface and Earth would not be inhabitable as we know it if we didn't have some greenhouse effect. Global warming refers only to the phenomenon of human-induced enhancement of the greenhouse effect. -User: Nightvid

Correction: Global warming refers not necessarily to a human-induced or anthropogenic global warming, but just the recent global warming activity of the Northern hemisphere. [Mαc Δαvιs] (How's my driving?) ❖ 18:13, 13 March 2007 (UTC)

Simply: The greenhouse effect is the cause. Global warming is the effect. An increase in the amount of greenhouse gasses in the upper atmosphere is causing more of the sun's heat to be trapped - which is a "warming" effect - and it's happening "globally" - hence Global Warming. SteveBaker 23:15, 13 March 2007 (UTC)

Tea: the cup that cheers

In Britain tea has sometimes been referred to as "the cup that cheers", meaning it cheers you up and improves your mood (it is nothing to do with cheering or shouting out loud). I know from personal experience that it often does this.

What is it in tea that improves mood? Drinking coffee or cocoa does not improve mood in my experience, so it is unlikely to be something like caffeine which is also in those other beverages. I have looked through the tea article and linked articles and this mood enhancing effect is not mentioned.

Second question about tea: how does the amount of catechins in leaves of the tea plant compare with the amount in vegetables? How much vegetables or fruit would I need to eat to get the same amount of catechin as found in say, one cup of black or green tea? Also not mentioned anywhere. 62.253.49.0 21:38, 12 March 2007 (UTC)

I've read some articles on wilderness survival that recommend brewing a cup of tea when you find yourself in a survival situation. The reason for this is that it keeps you from panicking unproductively, it gets you to do something productive (building a fire), and it's a familiar and soothing activity. Perhaps the latter is the reason tea cheers you up. Making tea is a very personal and calming activity, where coffee is usually made by machine. Shui9 02:13, 13 March 2007 (UTC)

Caffeine cheers me up. So that could be it as well. Both coffee and tea make me happier for that reason. They clear my head. 70.108.199.130 04:59, 13 March 2007 (UTC)

For your first question, have a look at our article on theanine. — Matt Eason ^{(Talk &#149; Contribs)} 14:13, 13 March 2007 (UTC)

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[6][7]. If you read German: [8][9][10] (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 [11]. 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 [12] 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. [13] 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: [14]

March 14

Interested?

I've listed a reward for the creation of the article Interdental plate on the Reward board. It's an easy job & would help me & other articles in the long run. I didn't know where else to post this message, but I figured a bunch of master mind/science guys would be patrolling around this page, so I posted here. Hope you don't mind. Thanks for reading - Spawn Man 06:33, 14 March 2007 (UTC)

• I have created a decent stub with three references. I look forward to seeing what others can add. Johntex\^talk 06:40, 14 March 2007 (UTC)

Great work Johntex. The reward has been completed & your barnstar awaits you. The article looks great, but if anyone wants to expand it, go right ahead. I might post more reward notices here soon, so keep an eye out guys (& girls). Thanks again... :) Spawn Man 06:53, 14 March 2007 (UTC)

Its a struggle finding material for this, but I eventually found an important use for it in fossil cladistics! Rockpocket 07:42, 14 March 2007 (UTC)

Alcohol and Muscle loss

My trainer says that everytime I drink alcohol, I lose some muscle, is there any truth in this? —The preceding unsigned comment was added by 76.167.136.84 (talk) 06:52, 14 March 2007 (UTC).

I am not a professional trainer, but I guess that's complete nonsense. Some people say, however, that alcohol contains a lot of calories, what means that you will get more fat and, therefore, less defined. "Maybe" your trainer meant that. --Taraborn 12:51, 14 March 2007 (UTC)

Alcohol denaturates proteins. Since muscles do basicly consist of proteins they might be destroyed by alcohol. This is also true for brain cells and every other cell type. However, the effect depends on the dose. Falk Lieder 17:06, 14 March 2007 (UTC)

Rubbish. [Mαc Δαvιs] (How's my driving?) ❖ 19:15, 14 March 2007 (UTC)

As for the affects on "intelligence" caused by heavy drinking, it could be useful to note the case of the really heavy-drinker Alexandre Alekhine. --Taraborn 21:29, 14 March 2007 (UTC)

Yes, alcohol does denature protein, however, the idea that it would somehow leap out of your blood vessels, burst through the cell membrane and start going to town on your muscle cells is at best rather silly. Alcohol is high in 'empty' calories, but it woun't 'destroy' muscle tissue. Wintermut3 18:04, 15 March 2007 (UTC)

smd vs. through-hole (moved from Computing desk)

In the case of a varistor, how do its parameters such as maximum energy and maximum continuous voltage vary when you convert a through hole varistor to an SMD? thank you.Gfranz G 03:03, 14 March 2007 (UTC)Gfranz [--Ouro (blah blah) 07:13, 14 March 2007 (UTC)]

What do you mean by "convert"? Cut/bend the leads so it will surface-mount? Continuous voltage obviously wouldn't be affected. Power ratings might vary a bit but I'd imagine they'd vary just as much depending on the lay-up of the PCB; soldering the varistor leads into/onto massive ground or power planes would obviously have some positive benefit to the long-term power rating although the impulse rating probably wouldn't change noticeable.

Atlant 12:05, 14 March 2007 (UTC)

The RF characteristics more than anything else are prone to being affected by lead geometry. -- mattb @ 2007-03-14T17:10Z

Thanks for taking the time in answering my question but I guess I didnt communicate my ideas well. What i meant by "converting" is to look for an SMD equivalent of a present through-hole varistor. In my case, the maximum continuous voltage of my through-hole varistor is 275Vdc and its maximum energy is 104J. I've looked up to the internet looking for SMD Varistors with the same or even almost equivalent parameters but the maximum contiuous vaoltage that I saw was around 56Vdc and worse for the maximum energy, the highest value that I got was 1.5J. that is why I was thinking that maybe some of the parameters of a varistor would be changed when it is "converted" from through-hole to SMD.

Gfranz G 00:40, 15 March 2007 (UTC)Gfranz

science behind the instrument triangle

Im doing a sound wave assignment in yr11 physics and i need to find out the science behind the instrument triangle but i can't find a thing on the internet. If anyone knows anything about it i would be very gratefull if they would share it with me.

Information after the 19/03/07 will be to late for my assignment

Thanks to anyone who helps —The preceding unsigned comment was added by 202.83.76.13 (talk) 09:40, 14 March 2007 (UTC).

I think you'll find that a triangle isn't so special; it's mostly just a compact form (of a cylindrical chime) that's cheap to manufacture. You might investigate this with a stroboscope. You might also consider tubular bell and mark tree.

Atlant 12:10, 14 March 2007 (UTC)

Resonance is my most favourite subject, but I can't find anything I really like with Triangle (instrument), and Bell (instrument). Link all of these with Standing waves, and you have a good paper. --Zeizmic 12:24, 14 March 2007 (UTC)

When you touch something, your atoms don't actually hit its atoms?

Hi all. I read somewhere that when you touch something, your atoms are not actually touching the atoms of the other object, but the electromagnetic force it exerts on your atoms, or something like that. Can someone please give me the specifics of that, as I found touch unhelpful. Or a wiki article referencing it would also be useful. Much help appreciated ! Xhin Give Back Our Membership! 09:56, 14 March 2007 (UTC)

Well, it really depends on how you definte touch. Everything is made of atoms, so practically, you're touching atoms. You're made of atoms, and the atoms on your hands are touching the atoms of whatever you're touching.

but if you want to get technical about it - then yeah, atoms don't actually "touch" atoms. It's like, the bits of one atom doesn't actually physically bump into the bits of another atom. The feeling of "solid"-ness is more to do with the energy field or repulsion around atoms. Atoms are mostly empty space anyway.

Then again, you can also say that the atoms on your hands aren't touching anything, because your hands aren't clean - they've covered in grim and dust and bacteria and all the rest. Our articles on atoms would probably help you more. And you may be interested to look at Cold welding too. --`/aksha 10:15, 14 March 2007 (UTC)

It's all true, in a way nothing ever touches anything else (or at least very rarely, where nuclear reactions aren't involved). Atoms are mostly empty space, and the 'contact' you feel in your fingers, the force that stops you falling through a chair when you sit on it, or stops a liquid seeping through the sides of a solid container, is the electrostatic force between the electrons in the atoms of one body and the electrons in the atoms of the other. Spiral Wave 11:54, 14 March 2007 (UTC)

As has been said it depends on how you define "touch". If you think about it as proton-on-proton action then no, you never "touch" in a very base kinetic sense. However once you realize that what we really mean by "touch" is not proton-on-proton action then it is not that weird. --24.147.86.187 00:08, 15 March 2007 (UTC)

'Solid on solid' doesn't exist, even in nuclear reactions. Every 'particle' is surrounded by force fields and the particles themselves have no 'solid' physical shape or size - the closer one examines a particle, the more insubstantial it appears. That doesn't mean that a force field isn't 'solid' - try jumping off a tall building to see the damage that force fields can do.... Paul venter 06:56, 15 March 2007 (UTC)

Yeah, 'particles' are pretty much just bundles of forces in the first place. More practically speaking, no, you're not floating above the ground or repelling off furniture, any more than you're mostly empty space. As long as you can't fly or walk through walls, atomic physics is academic. Black Carrot 06:56, 15 March 2007 (UTC)

Until someone drops an atom bomb on your city, sure it's academic. -GTBacchus^(talk) 07:00, 15 March 2007 (UTC)

Planet Fire

If you sent a space probe down into the atmosphere of a planet or moon made up of high levels of methane or any other flammable gas. Could the probe theoretically ignite the methane and set the whole atmosphere on fire? —The preceding unsigned comment was added by 212.219.119.130 (talk) 10:15, 14 March 2007 (UTC).

Not really. You need fuel+oxygen. If the atmosphere already consisted of fuel+oxygen then things like lightning or volcanoes would have set it off, in all probability. Pure methan can't burn unless there is an oxidant present. Greglocock 11:31, 14 March 2007 (UTC)

It's worth adding that, despite the massive abundance of oxygen in the universe, free (or molecular) oxygen is notoriously rare in planetary atmospheres, very rarely enough to fuel any sort of combustion. (Although ozone seems to crop up nearly everywhere.) Spiral Wave 13:02, 14 March 2007 (UTC)

The lack of free oxygen in planetary atmospheres - is precisely because if it existed, it would react with something and then it wouldn't be free oxygen anymore. The only reason we have it here on earth is because we have photosynthesis in plants continually pulling CO2 molecules apart and releasing free oxygen into the air. For this reason, if you did find a planet with abundant free oxygen, it would almost certainly be an indicator that there was life there. —The preceding unsigned comment was added by SteveBaker (talk • contribs) 16:59, 14 March 2007 (UTC).

The oxygen formed during photosynthesis comes from water molecules. The oxygen atoms from CO2 end up in organic compound such as sugars; see carbon fixation. --JWSchmidt 20:40, 14 March 2007 (UTC)

Jupiter, for example is mostly comprised of hydrogen which is highly flammable, but it cannot "burn", see Fire triangle. The vast majority of oxygen that is present is tied up in other chemical compounds, mostly water. Also, unless the oxygen concentration is large enough (beyond 5% or so) sustained fire is impossible, so any sort of "spark" will die. I'm not sure of the mechanism, but the Helium article gives the impression that the Helium mixed with natural gas (mostly methane) prevented combustion. Atropos235 23:58, 14 March 2007 (UTC)

c:) HS7 21:15, 14 March 2007 (UTC)

This also means that a lander could use a "jet engine" by supplying only the oxygen, and using methane from the atmosphere. This is the opposite of a jet engine in earth's atmosphere, where we carry the fuel and use oxygen from the atmosphere. -Arch dude 01:08, 15 March 2007 (UTC)

Magnetic strip

An easy way to check whether a magnetic strip is working or not? Another easy way of nullifying it? Thanks. --Taraborn 12:50, 14 March 2007 (UTC)

Per your first question: Dip it in Magnasee. Pass it through a skimmer.

Per your second question: Use a degausser. Run a rare-earth magnet along the stripe. Scrape the magnetic stripe entirely off.

Atlant 15:56, 14 March 2007 (UTC)

I had a magnets set when I was younger. It contained some sort of dull greenish "wax-paper" that could be laid on top of a permanent magnet. It would sort of glow brighter green indicating the field strength (I think I remember even seeing sharp green lines, which I always assumed were the division between north- and south- pole, but in retrospect, they are more likely transition regions between differently aligned magnetic areas). What in the world could that greenish paper be made of? Nimur 20:46, 14 March 2007 (UTC)

Apparently it is Magnet Viewing Film. Do we have an article? Nimur 20:48, 14 March 2007 (UTC)

Great answers! Thank you very much. --Taraborn 21:33, 14 March 2007 (UTC)

Acidity of oil

I read that the difference between extra virgin olive oil and regular olive oil is the acidity. Since oil and water don't mix, how can oil have acidity? --69.155.128.15 15:07, 14 March 2007 (UTC)

Fatty acids. See the Olive oil article for a starting point.

Atlant 15:53, 14 March 2007 (UTC)

How does taking breaks restore mental capacity?

I have read many suggestion on when and how long one should take breaks. However, I don't know any experiments on this subject. I also wonder how taking breaks restores mental capacity. Are there any neural correlates of mental capacity? If yes, do they change during demand and reverse during breaks? How well can blood sugar levels explain the effectiveness of breaks? Which effects do breaks have in addition to reducing monotony? I am looking for some information on research findings and references. Falk Lieder 16:56, 14 March 2007 (UTC)

Your subconscious mind often continues pondering things even while you're taking a break (or even sleeping). Unconstrained by the rigorous direction of your conscious thought processes, it often manages to look at your current problem from a new, unique, and useful point-of-view, thereby seeing a solution (or three).

Atlant 17:09, 14 March 2007 (UTC)

Breaks bother me. My mind works in turbo-charged mode, normal, or boring mode. I just do whatever each one tells me to do :) Boring mode, means sleep. Normal is normal, and turbo-charged means writing, reading, and talking. If I am like that I don't want to take a break and lose that, or my chain of thought. Lose the sense of discovery and learning. [Mαc Δαvιs] (How's my driving?) ❖ 19:14, 14 March 2007 (UTC)

I remember reading that a chemical in your brain is exhausted as you study/work/do whatever, and by taking a break, you allow the brain to recover its reserves of said chemical. I've been trying to remember the name of the thing for the last five years, though... Titoxd^{(?!? - cool stuff)} 19:59, 14 March 2007 (UTC)

Maybe you should take a break for a few minutes. [Mαc Δαvιs] (How's my driving?) ❖ 20:46, 14 March 2007 (UTC)

Improve hearing with training

Is it possible to improve your hearing by training yourself? Kind of like you can train your memory. Thanks in advance, Jack Daw 19:36, 14 March 2007 (UTC)

You can improve your listening skills by listening. You can practice identifying sounds, hearing a person speaking in a croud, identifying the direction a sound comes from. These will all involve the higher brain function rather than the brain stem nuclei improving. I dont know about improving your hearing however - cut down on the alcohol consumption and loud noise or music and clean the wax out of your ears! GB 20:54, 14 March 2007 (UTC)

Of course any ear doctor would recommend not sticking anything in (or even near) the ear canal without proper medical training. [Mαc Δαvιs] (How's my driving?) ❖ 21:02, 15 March 2007 (UTC)

Rumour

Is it true that you can get high off Earl Grey tea? I seriously doubt it is true, but people i know are convinced it is true, i cannot understand any scientific reason why you could get a 'high' off it.

Thanks a lot Dave 19:57, 14 March 2007 (UTC)

Bergamot orange says the oil has been linked to several negative side-effects such as photosensitivity (due to the chemical bergaptene) and the prevention of intestinal absorption of potassium. ST47Talk 20:49, 14 March 2007 (UTC)

If they are smoking the tea, they may be suffering from oxygen deprivation as the smoke displaces air in their lungs... Nimur 21:06, 14 March 2007 (UTC)

I have also heard this; the 'high' supposedly kicks in only upon smoking exceptional (although the numbers I do not have) amounts of the tea leaves. But I also suppose, if you'd be doing this with good Earl Grey, that it's a waste of perfectly excellent tea. --Ouro (blah blah) 21:41, 14 March 2007 (UTC)

I also seriously doubt it is true. BTW, how much does an ounce of "Earl" cost?  ;-) --hydnjo talk 00:19, 15 March 2007 (UTC)

What, are the banana peels not doing the trick? Never underestimate the ability for people to be willing to believe and re-tell utter nonsense. --24.147.86.187 03:45, 15 March 2007 (UTC)

I don't know about ounce, but a few months back I had bought really wonderful Earl Grey, selling for 8 Euro for half a kilo (=just a bit more than a British pound) in Germany. So, at rough count, it's equal to 16 ounces, so it's something round 50 cents for the ounce. The brand is Messmer, if I may. --Ouro (blah blah) 06:17, 15 March 2007 (UTC)

base metals

I have searched for info regarding base metals, specifically gold, sodium, and magnesium. I'm certain that gold is a noble metal. I'm fairly sure that magnesium is a base metal, but sodium confuses me. Sodium is referred to as a alkali metal and magnesium is referred to as a akalne earth metal. Does that description answer my question or am I missing something? Thank you for your help.

Base metals are common, such as copper lead zinc or tin. Although sodium is common as an atom it is not often found as a metal. Magnesium is a marginal case as you noticed, I would not have counted it as a base metal as it is still slighly exotic. GB 21:06, 14 March 2007 (UTC)

There are articles on gold, sodium, magnesium, base metals, alkali metals and alkaline earth metals. Take a look and start from there. I'd answer myself, but chemistry was a looong time ago :) Cheers. --Ouro (blah blah) 21:38, 14 March 2007 (UTC)

According to the first, chemistry, definition of Base Metal given in the article Base metal, it looks like magnesium and , I'd say, sodium are base metals. According to the alchemical definition, they probably aren't, although they're not really precious metals either (in the alchemical sense) or noble (in the chemistry sense). Since it looks like you're looking for chemistry, I'd say they're both base, but I'm not sure how useful such description is. Oh, and I'm pretty sure the use of the word 'base' here is unconnected with acid/alkali, in case that was the problem! If you're looking for an alchemical answer, based on their value and such like, I don't think the alchemists had them. Skittle 00:35, 15 March 2007 (UTC)

PE at absolute zero

Hi all,

I have a physics simulation that I'm working on which models the movement of atoms. With this model, I can add or subtract heat from the system, and am able to move down to absolute zero where there is no motion. All the particles in the system are essentially frozen in place.

When I stop actively subtracting energy, the model slowly warms back up again. Looking in closer depth, I see that this is because the attractive forces between the atoms, however slightly, draw the atoms towards each other, which causes motion. That is, when the atoms in my model are at "absolute zero", they still have some potential energy.

Wouldn't this happen in the real-world (were it possible to reach absolute zero, which it isn't)? Or, if a system is at absolute zero, are all the atoms in the system at exactly the right distance such that their attractive forces and repulsive forces are absolutely balanced?

Thanks,
Michael 20:50, 14 March 2007 (UTC)

Of course this will depend on how you model your attractive forces. Can you shed some light on what attractive/repulsive system you are using? If you are using 1/r^2 (inverse square law forces), I think I recall that there are only stable equilibria for certain configurations. Also, be aware of numerical error (roundoff or quantization error) in any computational simulation - this error may accumulate depending on your method of computation. Also, it sounds like your "subtracting of energy" is done by decreasing the velocity - in that case, it is only affecting Kinetic Energy. In that case, you are not affecting Potential Energy at all. Can you describe your model a bit more? Nimur 21:01, 4 March 2007 (UTC)

In real life the collection of atoms will warm up by energy coming in from outside. If there is potential energy that can force an atom to move it is not at absolute zero. An isolated collection of atoms staying in the same position, that is not undergoing some transformation (eg chemical or radioactive) should stay at the same temperature. Nether-the-less there is still unextractable energy at absolute zero, due to the uncertainty principle. An atom in a fixed position cannot have its veolcity or energy known precisely, or coversely if you precisely know the energy of an atom, you will not know its position. Interesting things hapen when the uncertainty in the position becomes macroscopic. GB 21:02, 14 March 2007 (UTC)

1) Yes, the energy is "subtracted" by slowing down the atoms. Since temperature is the average KE, then slowing down the velocity to zero will make the temperature zero Kelvin. When I said there was still PE, what I meant was that there was still a force on the atoms from the other atoms which would incline them towards motion

2) If we were to suddenly make all atoms in the universe absolutely motionless for an instance, removing all their KE and momentum, would they not return to motion again because of the forces between them? This is the situation my model seems to be in.

3) Am I right in thinking that, at real absolute zero, the atoms ought to be in some stable configuration around each other?

Thanks --Michael 01:25, 15 March 2007 (UTC)

Regarding your first point, I want to add that there's a bit more to absolute zero than the stopping the motion of whole atoms. Absolute zero implies the total cessation of thermal motion: no vibrational motion in the nucleus, no orbital motion of the electrons, nothing. And if you could "stop" the electrons, then all sorts of funny stuff would happen (and very little of it stable). (Edit: 2 am and back from the pub, this was meant to be read as tongue-in-cheek, but it doesn't come across as such. My apologies again.) So asking what happens when everything gets - if I may paraphrase - "slowed to a stop" is probably not going to properly answer your question. Instead, you would do better to try and model what happens when you get arbitrarily close to zero, a more physically realistic getup. Spiral Wave 01:58, 15 March 2007 (UTC)

No, I'm sorry, that's just not accurate; absolute zero does not imply anything of the kind. It doesn't even imply that the individual atoms are not moving. In fact, they are moving, even at absolute zero.

You have an overly simplistic notion of what "absolute zero" means. It can't be characterized completely in terms of motion. What it means is that the first derivative of entropy with respect to internal energy is infinite. --Trovatore 02:40, 15 March 2007 (UTC)

While I would agree that I have an overly simplistic view of A.Z., the point that it can't be completely characterized in terms of motion is exactly what I was trying to get across. I wasn't concerned with being overly accurate; just to show how bizarre things become (although I plainly pushed it way too far; my apologies to our questioner). That mathematical description of entropy is of course far better; but it's not going to help this person with their physical model, which is why I linked the appropriate subsection. Spiral Wave 02:55, 15 March 2007 (UTC)

Correct if I'm wrong, but I understood that AZ had no Latent heat in the system. This implies a solid and an equilibrium such that bonds of the solid have any potential energy transfer due to vibration and attractive forces are balanced by the forces of the solid. --Tbeatty 03:07, 15 March 2007 (UTC)

Helium is not a solid at absolute zero (at atmospheric pressure). --Trovatore 03:15, 15 March 2007 (UTC)

It's a meaningless question - the Third law of thermodynamics says that no real world system can ever reach absolute zero. It's similarly meaningless to say what happens to Helium at a temperature that it simply can never reach. SteveBaker 06:32, 15 March 2007 (UTC)

Not at all. As I recall, the superfluid phase of Helium II is at absolute zero. Liquid helium below the lambda point is a mixture of Helium I and Helium II, so the system as a whole has positive temperature, but if you restrict attention to just the Helium II, it's actually at absolute zero.

Neither is it impossible in principle for a body to reach absolute zero. You can't get it there mechanistically, but if all the phonons radiate away just by chance, it can get there on its own. Entropy reversals can happen, if you wait long enough.

The point is that the zero-point energy of helium is sufficient to overcome the interatomic attraction. While you can't (at least on purpose) get its internal energy down that low, you can get very close indeed, close enough to tell that the little bit you have left to go is not enough to allow interatomic attraction to cause the helium to freeze. This, if you like, is the real-world meaning of the statement, without waiting for all the energy to radiate away by chance. --Trovatore 06:57, 15 March 2007 (UTC)

Indeed, you can get arbitrarily close, which is why I think our questioner would be better off trying to describe a superfluid (or a supersolid) rather than worry about what happens at zero itself.

The helium II is a good case, but it depends on the complexity of his model; a thermodynamic description of one component of a 2-fluid mixture may or may not be of any use. (Is it, Michael? I'm curious myself, now!) Spiral Wave 10:10, 15 March 2007 (UTC)

Individual atoms (or, I guess, very small groups) could happen to get to a zero energy state - but temperature is a bulk property and the laws of thermodynamics most certainly apply. SteveBaker 14:58, 15 March 2007 (UTC)

The laws of thermodynamics are probabilistic, and apply only probabilistically. That means they can be violated just by chance. The chance is extremely small, of course, but if you're arguing that something is meaningless because it can't happen, well that's wrong. --Trovatore 17:30, 15 March 2007 (UTC)

The short answer is Simulations with classical mechanics can't reproduce 0 Kelvin - you need Quantum Mechanics. WilyD 15:21, 15 March 2007 (UTC)

Fine fine, let's call it "arbitrarily close to absolute zero". It doesn't really change my question. If I suddenly slowed all the atoms in, say, a liquid, so that their KE was arbitrarily close to zero, but they remained in the same general location as before I slowed them down, they would still have attractive and repulsive forces between them, right? So in this bizzare simulation, I'd expect the atoms to start speeding up again, right? Or not? --Michael, 16:46, 15 March 2007 (UTC)

You can't just stop the atoms in place where they happen to be, they have to moved to the position where they have no potential energy, as you have already observed they will start moving again. You need to take out all the available energy to get to AZero. GB 00:40, 16 March 2007 (UTC)

what is the difference between denaturing and melting?

ditto.

HS7 21:17, 14 March 2007 (UTC)

Depends on context, of course, but Denaturation (biochemistry) and Melting may help. If you are talking about these in terms of DNA, then "melt" is just a term often used to descibe the denaturation of a double strand into two single strands. Its not technically an example of true melting. Rockpocket 21:22, 14 March 2007 (UTC)

They both seem the same to me, things falling apart because of the particles they are made from moving more :( HS7 19:08, 15 March 2007 (UTC)

Yeah, they both involve the same molecular process, but the difference is the change in state. Melting requires a change from s solid to a liquid, denaturation doesn't. Rockpocket 19:19, 15 March 2007 (UTC)

What is rescued virus?

Hi all, Can anybody please tell me what is rescued virus as they are making in all of the experiments and why we need to make them in the experiments? I am referring about the virology and molecular biotechnology stuff. Thanks! --Nirajrm ^{talk ||| sign plz!} 22:37, 14 March 2007 (UTC)

I'm not 100% sure, but I think a "rescued" virus is a virus that is missing in its genome a key component for viral replication, but when infected into a cell line expressing that key component, allows replication. As to why that strategy is used, there could be several reasons (control of replication, protein/gene of interest is what's "rescued", other things I don't know about since I'm not a virologist...). Hope that's sorta right, and it helps. -- Scientizzle 03:01, 15 March 2007 (UTC)

In molecular biology the term "rescue" is typically used in the sense "recover". Plasmids, genes and other entities can be rescued from cells containing them. In the context of viruses the term is most often used to mean recovery of infectious virus particles from a cell line that has been transformed with one or more pieces of viral DNA. This way the researcher can first manipulate the viral sequence using standard molecular biology techniques (e.g., pcr) and subsequently obtain virus particles containing the manipulated viral genome. This is useful for vaccine construction for instance. [15] -- Gorm 12:12, 15 March 2007 (UTC)

Thanks a lot and I think I got the answer. Thank you Scientizzle and Gorm! --Nirajrm ^{talk ||| sign plz!} 21:39, 15 March 2007 (UTC)

March 15

Want to disinfect clothes during washing but without disinfectant smell

I have a harmless skin rash caused by bacteria. I have been to the Doc and got some ointment for it which did work and clear the rash. However it now seems to have re-occurred, which from what I've read about it on the internet is not uncommon.

I suspect it may be lurking in my clothes and sheets.

Is there any safe odourless liquid that I can add to my washing machine to help disinfect my clothes? Or for that matter, to my bath?

Ordinary disinfectant could be used, but it does make your clothes smell. Bleach may also be effective, except it damages colours.

Does anyone know of anything else that could be used please? —The preceding unsigned comment was added by 62.253.48.122 (talk) 00:19, 15 March 2007 (UTC).

• Bleach and ammonia will both effect colored clothes. A -really- hot wash would probably kill most bacteria. For maximum hotness you could try taking everything to a laundromat and washing and drying it there with the washer and dryer on their hottest settings. --Peta 00:26, 15 March 2007 (UTC)

• Washing at 60 degrees C (140 degrees F) should kill most bacteria [PubMed]. Of course you also want to make sure that the rash is not caused by allergy to laundry detergent additives such as fabric softener or perfume. Gorm 10:36, 15 March 2007 (UTC)

SMD VS. through hole

Thanks for taking the time in answering my question but I guess I didnt communicate my ideas well. What i meant by "converting" is to look for an SMD equivalent of a present through-hole varistor. In my case, the maximum continuous voltage of my through-hole varistor is 275Vdc and its maximum energy is 104J. I've looked up to the internet looking for SMD Varistors with the same or even almost equivalent parameters but the maximum contiuous vaoltage that I saw was around 56Vdc and worse for the maximum energy, the highest value that I got was 1.5J. that is why I was thinking that maybe some of the parameters of a varistor would be changed when it is "converted" from through-hole to SMD. —The preceding unsigned comment was added by Gfranz G (talk • contribs) 00:36, 15 March 2007 (UTC).

SMD components are typically smaller. The size of many thru-hole electronic devices are often grossly larger than they need to be, with most of the space being taken up by packaging, and some devices don't need as high power ratings, so resistors can be made the size of a period that can handle 1/100 of a watt. However, for power devices this is another matter, power devices need a certain physical size to be able to handle large amounts of current, voltage, and dissipate power. Interesting that you bring up varistors, because where I work, we have several automotive electronic devices that are completely SMD except for the varistors, and I assume it's because they just can't make a device (the varistor) that can handle that much energy into a SMD component, and if they could, it would have poorer characteristics and likely cost more than the "bulky" thru-hole component. Atropos235 04:29, 15 March 2007 (UTC)

Is Miconazole nitrate safe to apply long-term to skin?

I have a harmless(?) skin rash called Erythrasma which is caused by Corynebacterium minutissimum. I had it in my groin and axilla. It was treated with a Miconazole nitrate ointment preperation and did almost disapear, but has now re-appeared in my groin. I have by the way already seem my doctor about this.

My question is, is it safe to apply a spray of Miconazole nitrate to my skin as a preventative measure over a period of months say?

Miconazole nitrate is also the active ingrediant in a spray sold in supermarkets etc in the UK under the trade name Daktarin used to treat Athlete's foot, so it is easy to get and use.

Is it nitrates or nitrites that are carcinogenic?

62.253.48.38 00:44, 15 March 2007 (UTC)

Wikipedians may not offer medical advice, therefore you should ask your doctor (or perhaps your pharmacist) about the safety of preventative treatments. Regarding nitrates and nitrites, i'm not sure either are a proven carcinogen. However, in the presence of amines, nitrites can form nitrosamine, which is a carcinogen (at least in animal models). Rockpocket 00:51, 15 March 2007 (UTC)

Old age memory loss

Does the first sign of old age memory loss start with for example wanting something from another room and then not being able to remember what it was you went in the other room to get, or is this problematic at any age? Diligent 01:39, 15 March 2007 (UTC)

I think it happens to everyone. -Wooty Woot? contribs 01:43, 15 March 2007 (UTC)

It's pretty clear that memory efficiency gets worse and worse as you get older - but this is somewhat compensated for by older people adopting cleverer ways to remember and recall things. I have no clue what the first sign of the very gradual process is - I doubt that there is one single thing you could use to pin it down. The specific case you mention could be a symptom. SteveBaker 06:26, 15 March 2007 (UTC)

Your doctor would be a good person to discuss this with if it is a concern in your own life or that of someone in your family. We cannot give medical advice here. Edison 22:22, 15 March 2007 (UTC)

Solar Energy

what are the advantages of using solar energy and what are the costs as a alternative fuel for petroleum? —The preceding unsigned comment was added by 69.211.138.45 (talk) 01:51, 15 March 2007 (UTC).

• I suggest you start with Solar energy and Hubbert peak theory. Basically, solar energy is free, but equipment to make it and transport it consumes resources (including usually petroleum). Solar energy is not available at night unless some sort of energy storage is available. Also, not all areas are sunny, especially during the local stormy season. On the other hand, our oil will run out long before the sun will. In human terms, the sun is inexhaustible. Not true for oil. Johntex\^talk 02:27, 15 March 2007 (UTC)

Cancer and Tumors

I was looking at the cancer article and it mentions tumors, but do all cancer include tumors? Or can you have cancer and not have a tumor? —The preceding unsigned comment was added by 76.167.159.75 (talk) 02:33, 15 March 2007 (UTC).

All cancers have tumors, not all tumors are cancers. There's a whole section at the cancer article. - AMP'd 02:44, 15 March 2007 (UTC)

Check out Tumor as well... -- Scientizzle 02:57, 15 March 2007 (UTC)

What about leukaemia? It's a cancer but there's no tumour in sight, is there? Aaadddaaammm 03:04, 15 March 2007 (UTC)

I was thinking the exact same thing. Leukaemia creates bad blood cells, and I don't think those are considered tumors. --Wirbelwindヴィルヴェルヴィント (talk) 07:28, 15 March 2007 (UTC)

glasses

if a pair glasses increase in power, does it make the wearer's eyes even smaller than before? —The preceding unsigned comment was added by 219.88.175.202 (talk) 03:01, 15 March 2007 (UTC).

The power of glasses is usually measured in diopters. People with myopia (nearsightedness) use glasses with negative diopter values; those lenses are concave, while people with hyperopia (farsightedness) wear glasses with a positive diopter value, which are convex. Magnifying glasses are of the convex type, they will bend the light to make things appear closer or larger than they truly are, which would include someone's eye behind a pair of glasses. However, when someone says an "increase in power" of glasses, it could go either way, a more positive diopter would mean a more convex lens, increasing the apparent size of their eye, or a more negative diopter which would be a more concave lens, decreasing the apparent size.

There is another factor though, the distance of the lenses from the person's eye. As you notice with a magnifying glass, when you pull the lens away from the object under study, the image increases in size, and the opposite holds true with a concave lens, so a new frame for the lenses could also change the apparent size of the eye to an observer.

Read up on Optics, it's an interesting topic and you can do some neat experiments. Atropos235 05:01, 15 March 2007 (UTC)

If you mean, does it gradually physically change the shape of the wearer's eyes and possibly make his or her eyesight get worse, the answer is, as far as I know, no. Clarityfiend 07:01, 15 March 2007 (UTC)

capacity of an electrical circuit

This is probably a ridiculous question, but bear with me, i don't think i'm very good at electricity.

As i understand it, each circuit in a house has a certain limit as to how much electricty can be pulled from it (15 or 20 amps or whatever i guess?). In other words, no matter how many receptacles you install on that circuit, you're always going to have to work within that limit, there's no way around it.

Assuming that all is right, here's where i get confused. I have always been taught not to plug too many things into a single outlet, because otherwise they'll catch fire and it'll be armageddon and so on. I can't see how this is the case, though, if what i said above is true. If there's the same limit on the capacity of the circuit whether you have one outlet or a hundred, why should it matter how many outlets my stuff is plugged into? They all go to the same place, right? How is plugging twenty things into one outlet (assuming the power strip or whatever is rated for it) less safe than spreading those things out amongst two or three outlets on the same circuit?

Have i been taught wrong or is there something i'm missing?

FYI: The reason i ask is, in my bed room i only have one receptacle. This is very annoying, because between all my computer stuff and my TV stuff and lamps and hair-straighteners and phone-chargers and so on i (obviously) have way too much stuff to fit into it, not to mention it's very inconveniently placed (which forces me to use extension cords, blah blah). So i'm debating trying to get somebody to install a new receptacle or two for me.

A much easier (and cheaper) option, though, would be to make use of our drop ceilings and just run an extension cord up there leading to like a $40 APS BackUps thingie on the other side of the room, so i can plug my 'puter junk in, and then leave a power strip plugged into the other outlet in the receptacle for the TV and stuff. My mom advises against it, though, due to the above too-much-stuff-plugged-in-makes-a-fire reasoning.

Opinions? ~ lav-chan @ 04:28, 15 March 2007 (UTC)

The 15-20 amp limit you mentioned is usually determined based on the gauge of wiring used in the house, which is then enforced by the appropriate selection of a fuse or circuit breaker. Older houses often used thinner wire that can only handle a continuous 15 amps safely, while newer houses will commonly have heavier gauge wire that can take 20. More to what you're saying, yes, theoretically it would be safer to plug 10 devices that each draw 1 A into a circuit than one 15 A device, but there really should be no danger because if things get unsafe (at least within the walls of the house) the fuse/circuit breaker will interrupt power.

However, just because the house won't catch itself on fire, doesn't mean that poorly designed devices plugged into the house can't. Computers and phone charger cords in my experience don't really cause much heat (unless they are confined in a small space with almost no airflow) like an ancient (50's) space-heater we have does, where the cord probably could singe stuff if it was left on for a long time. Some lamps can be poorly made, thin lamp cord + high wattage lamp could get hot, but anything made this decade should be fine, especially if it has a UL symbol on it.

In short, using a power strip is OK, just don't cover it up under blankets or dirty clothes, let it get some air. Atropos235 04:47, 15 March 2007 (UTC)

The U.S. Consumer Product Safety Commission estimates that about 3,300 residential fires originate in extension cords each year, killing 50 people and injuring about 270 others, and recommends against using them in place of permanent wiring,[16] as does Underwriters Laboratories[17] and the United States Fire Administration[18].—eric

Fundamentally, there's no difference between plugging many appliances into many different outlets (assuming those outlets are on the same circuit), and plugging the same appliances into a single outlet using a power strip. There's a least two reasons why extension cords tend to be more dangerous, though.

First, the thickness: The required thickness of a piece of wire, whether it's an extension cord or Romex installed in your walls, is determined by the current through the wire, and the thermal environment of the wire. The more current you put through a wire, the more heat it generates. The thinner the wire, the more its resistance, so the more heat it generates for a given current. The wire must stay cool enough that it doesn't melt or burn its insulation, or anything else nearby.

Permanently installed wiring is hidden in the walls, where the code writers assume that it is fairly well insulated thermally. This means that it will take only a little bit of heat to get the wire very hot, so it's important that the wiring generate very little hit. Typical houshold wiring is 14 gauge, fairly thick. Whoever designs the extension cord assumes that it will just be sitting out in free air, so it doesn't matter if it generates more heat, because the environment will keep the extension cord cool. A typical extension cord is 16 or 18 gauge; higher gauge is smaller, so that's thinner.

Second, and possibly more important, extension cords are more subject to mechanical damage. Permanent wiring is safely behind drywall, but extension cords tend to get stepped on and abraded.

I'd get an electrician to run a new outlet. They might be able to just run armored cable in the suspended ceiling, like they do in commercial buildings, in which case it would be fairly cheap. Modern building codes tend to require multiple outlets on multiple circuits in many rooms (especially kitchens etc.), which is very convenient. If you don't run a new outlet, it's probably safer to run the extension cord in the ceiling than under a rug. 24.91.135.162 11:28, 15 March 2007 (UTC)

That's helpful (all three of you), thanks. ~ lav-chan @ 18:58, 15 March 2007 (UTC)

One factor in addition to basic amperage the circuit can carry is power quality. When plugs are plugged into extension cords I have seen power quality problems due to the higher resistance in the ground path. The more plugs there are in series the worse it is. Outlets generally seem to have more solid connections. Edison 22:17, 15 March 2007 (UTC)

Penguins and white bears habitat

Why polar bears live only in Arctic but not in Antarctic? Why penguins are confined to the Southern Hemisphere and are absent from Arctic?Fo63 04:37, 15 March 2007 (UTC)

And while we are at it, why are kangaroos found only in Australia and not on the North American plains, and why are gila monsters found in North American deserts but not Australian? Gee, maybe we could generalize the question to "why is every species where it is instead of a similar environment on another continent?" The answer is historical contingency [19]. alteripse 05:09, 15 March 2007 (UTC)

Basically, if you are a cold-weather animal and you evolve at the North Pole, you have no way to get to the South Pole without crossing the insane temperatures of the Equator to get there...and vice-versa. But in any case, there are very significant differences between the two poles. For one thing, you can get from warmer weather climates to the North pole by walking and swimming short distances - so a group of warmer-climate bears could gradually move further north, evolving the adaptations needed for severe cold. But the antarctic is a long way from any other continent - far too far for a land animal to swim. Birds, on the other hand, could have flown there - then evolved to lose their flying ability - which might interfere with efficient swimming or something. Fully evolved penguins are like ducks though - they can happily bob around on the water without needing to expend effort to avoid drowning - so Penguins could have been blown off course and over to the antarctic at some time in the past. SteveBaker 06:21, 15 March 2007 (UTC)

And penguins are pathetic. The only reason they aren't extinct is that there are no predators (such as bears) there to eat them

Dear anonymous. I think you will find that penguins are awesome. Yours sincerely, Capuchin 13:33, 15 March 2007 (UTC)

Yes! They are indeed awesome. Ungainly on land, granted - but underwater they are graceful, fast, highly effective. And in any case, Penguins do indeed have predators - Leopard Seals, Killer Whales and other birds that steal their eggs - to name but three that I know off-hand. SteveBaker 15:04, 15 March 2007 (UTC)

Don't forget the Penguin's biggest enemy: Batman. Clarityfiend 17:10, 15 March 2007 (UTC)

You can see how birds evolve into penguin, see Great Auk. 202.168.50.40 23:26, 15 March 2007 (UTC)

Or indeed, the Great Auk can tell you that we did, kind of, have penguins in the northern hemisphere, or very like. The penguins are still around, unlike the great auk, because we couldn't get to themoriginal research... Skittle 23:48, 15 March 2007 (UTC)

Has there been any research in the effect of visual cues on the perception of temperature?

For instance, let's say I have a red tube, and I have it cooled to a low temperature. And then I have a blue tube, and I have it cooled to the same temperature. And then I ask random people to touch the red one, and record the apparent temperature on a comparison scale. Then I have a separate group of random people to touch the blue pipe, and record the apparent temperature. Have there been any tests like this, in order to test whether preconceived notions about colors (red = hot, blue = cold) affect the perception of the temperature? And of course, the experiment could also be reversed, with the tubes heated instead. Thoughts? --Ķĩřβȳ♥ŤįɱéØ 07:02, 15 March 2007 (UTC)

Good question. A search of PubMed reveals a study that appears related, but not using your exact experiment. PMID 1155649 reports that "hot/red, warm/yellow, cool/green, cold/blue" associations are a learned trait and thus have a cultural, rather than a evolutionary or physiological, basis. Rockpocket 07:42, 15 March 2007 (UTC)

I agree - it doesn't seem likely that evolution could get us "red=hot" because only things that are literally 'red-hot' would look like that - and in nature, only stuff like lava flows is ever that hot and I doubt that enough early humans ever got close enough to lava (and survived) to have any evolutionary pressure. Like a lot of colour "meanings", it's highly cultural. We're more likely to have evolved "Red==Ripe & Delicious", "Green==Unripe or Leaves, avoid", "Blue==Severely mold-infested!" SteveBaker 14:49, 15 March 2007 (UTC)

I don't know whether there would ever be an evolutionary advantage to associating colours with temperatures. Humans have resonable enough temperature sensors that it seems unlikely to me this would have any real advantage. I.E. even if there there was some learned association, I doubt there would be an evolutionary reason an inate ability will be favoured evolutionary wise Nil Einne 15:10, 15 March 2007 (UTC)

I guess the more interesting question is whether all human cultures make the same basic colour/temperature associations. If so, there may indeed be some inherent element, a bit like Chomsky's theory of universal grammar. Rockpocket 18:10, 15 March 2007 (UTC)

Science Magazine

Hello I've been reading New Scientist for the past two years and really like it. Now that my subscription has come to an end I'm considering trying a different magazine. Unfortunately individual editions are not available for purchase where I live so I'd have to buy a subscription straight away. I was thinking maybe trying Scientific American. Could you recommend general scientific magazines, which one(s) do you think are better for a non-scientist who likes to read about science? Thank you 81.242.185.120 11:15, 15 March 2007 (UTC)

IMHO, Scientific American is at about the same technical level as New Scientist - but it's less like a newspaper and more like a typical science journal compared to New Scientist. I think you'll like it. The biggest problem for me when I switched was that New Scientist is weekly - Scientific American is only monthly - which left me frustrated because I had nothing to read. Neither New Scientist nor Scientific American are 'peer reviewed' - which makes them a little less reliable than other scientific journals - but since peer review takes time, it means they can carry the breaking stories months sooner than their competitors. If you are ready for something a little more 'hard core' (and peer reviewed), you might want to check out Nature (Monthly, very well respected, peer reviewed, but harder reading than Sci-Am or NS) and Science (Weekly, peer reviewed and more "newsy" than the others - also harder reading than Sci-Am/NS). Those are the only journals that come to mind that cover a broad spectrum of the sciences - most others specialise in one field or another. I suggest you visit a library (they usually have back-editions of these magazines) - or perhaps a book store or good magazine stand - they should have Scientific American...and maybe Science. SteveBaker 14:41, 15 March 2007 (UTC)

How do you find the focus of SA compared to NS? I've never really read SA but I feel NS (which is British) provides a resonably international focus and often wonder if SA is as good or has too much of an American focus. It's probably primarily the name that makes mean doubt SA tho which doesn't really make sense I guess Nil Einne 15:05, 15 March 2007 (UTC)

I don't really see much of a spin or other bias in SA. My threshold for that kind of stuff is usually low, especially on anything labeled "Scientific", but I'm an American, so what do I know. Atropos235 00:41, 16 March 2007 (UTC)

As a minor correction, Nature is also weekly. Dragons flight 17:03, 15 March 2007 (UTC)

I wouldn't recommend a subscription to Science or Nature to someone who has been reading New Scientist without them looking at it in their local library (or wherever else) first. The articles in them are usually very high-level, and even someone experienced in one field would be baffled by some of the other fields they cover. Scientific American is a nice choice, often authors that publish papers in the other journals write a more user-friendly, approachable article for SA, so yes, while it is not peer-reviewed, the articles are not themselves novel, instead based on research first published elsewhere. Weekly vs. monthly...that's up to you. On a personal note, I've had a subscription to SA since 1998, and through a combination of a few people giving me gift subscriptions and me buying them, it won't run out until 2012. Atropos235 19:27, 15 March 2007 (UTC)

I personally prefer Scientific American over New Scientist and Discovery. [Mαc Δαvιs] (How's my driving?) ❖ 20:57, 15 March 2007 (UTC)

I think he means Discover there. --Anon, March 15, 2007, 23:30 (UTC).

Yep. I was thinking about the channel when I wrote that. [Mαc Δαvιs] (How's my driving?) ❖ 00:19, 16 March 2007 (UTC)

Could you actually give reasons and explanations for what you prefer about it over the others? Otherwise you've just given your preference, which is facinating but doesn't really help the person make a decision. Skittle 23:37, 15 March 2007 (UTC)

I would, but I can't say why. I just like SA better. Discover is too thin too. [Mαc Δαvιs] (How's my driving?) ❖ 00:19, 16 March 2007 (UTC)

Scientific American's articles are written at a level high enough for someone who has a better-than-average knowledge base to enjoy. Magazines like Popular Science are really off-putting to me because the articles contain no skepticism whatsoever, and they're written to be just that, popular, not informative. On the other extreme, the Science and Nature journals are extremely thick (intellectually). Don't get me wrong, they're great for journals, and that's where you'll find all the cutting edge stuff, and it's a great reference if your library has a bunch of the previous issues (I actually just dug an article out of Science for a project), but it's not really for reading through. SA is the happy medium for me, where I can pick up an issue and read it cover to cover, understand, and enjoy it. For a weekly science fix, I like the Nature podcast and Talk of the Nation - Science Friday (on your local NPR station on Fridays). Atropos235 00:38, 16 March 2007 (UTC)

Oh, NOVA...another weekly fix. Not really a magazine...but it can be very interesting. -- atropos235 ✄ (blah blah, my past) 04:19, 16 March 2007 (UTC)

Veins

Are bodybuilders veins that become visible (like in their arms by their bicept) because of the muscle pushing on the vein or do the veins actually get thicker and bigger?

It's a combination of the muscles being a firmer base for the veins and the bodybuilder having less body fat to mask the veins. Anchoress 18:40, 15 March 2007 (UTC)

Note that the veins do actually get larger as well. More muscle = more tissue which requires nutrients and oxygen = more blood required = bigger tubes. TenOfAllTrades(talk) 19:18, 15 March 2007 (UTC)

Vasodilation may be a factor also, I bet you get pretty warm injecting steroids working out. Rockpocket 19:45, 15 March 2007 (UTC)

How Do E-Mail, FTP, Newsgroups and Message Boards, Mailing Lists, Chat Rooms, and Instant Messaging Work?

Not sure about the bodybuilding question. Your second question I can answer. Internet e-mail is basically an easy way of transferring messages between computer systems. Modern e-mail systems typicall use SMTP for the protocol. FTP stands for File Transfer Protocol, and it is a way to transfer files between computers easily. FileZilla is a popular FTP client. Newsgroups are a way of getting "news", whether text or binary, from a central server. NewsLeecher is one client I can think of top of my head. Internet message boards are basically places to discuss. Mailing lists are basically lists of e-mails which are used by e-mail programs to massively send to all e-mails. Chat rooms on the Internet are in the form of Internet Relay Chat, an Internet protocol. IRC basically allows real-time communication on public servers. Instant messaging same thing, except proprietary servers with extra features. Sorry if I missed stuff, quick response. Splintercellguy 18:27, 15 March 2007 (UTC)

about algae growth

normally if an aquarium placed outside of the house, the water turn to become green.. this is because of the algae growth.. algae grow with the sunlight and a proper temperature.. well my question is will the algae grow eventhough there is the sunlight but the temperature isn't proper for the algae..

There aren't too many temperatures where algae won't grow, except solid ice, or boiling. --Zeizmic 22:00, 15 March 2007 (UTC)

Coffee Question

(split from above question by Atropos235)

and another question will a coffee moleculs can be break or separated after the plain water mixed with the coffee powder.. and what are the chemical or nature way to separate back the moleculs..

thanks for the time and patients sir/madam..

Er, well for starters, coffee grounds do not consist of a single type of molecule by any means. They are a mixture of all kinds of organic compounds, which probably interact with water in different ways. -- mattb @ 2007-03-15T20:49Z

You might start be reading about solutions, the chemical name for the special type of mixing of molecules in coffee. Some of the chemicals may be in suspension, while others are chemically dissolved. Molecules in solution can not be easily separated by physical means (this is why the coffee liquid goes right through the coffee filter! However, the coffee grounds do not dissolve, and therefore can be separated out (i.e. they stay behind after filtering). Hope this gives some pointers towards the answers you seek. Nimur 20:54, 15 March 2007 (UTC)

Since you ask about coffee powder, it is possible you mean instant coffee, which dissolves in water? If so, in the powder, each grain of powder is made up of lots of different sorts of molecules, because coffee is made of more than one type of molecule. It is a mixture. In the powder, these molecules are held to each other by various bonds. Each grain of powder is solid. When you mix this powder with water, the water molecules (which are moving around, because water is a liquid) will bash into the solid grains of coffee. This will cause the molecules on the outside of the grain to break off and float around in the water; these molecules are said to be 'in solution'. Eventually, if there's enough water for the amount of coffee, all the molecules that made up the solid coffee powder will be in solution. So the molecules do not break, but they do seperate from each other. You can seperate the coffee molecules from the water molecules by evaporating the water away, although a small number of the coffee molecules (responsible for the coffee smell) will also evaporate. You could solve this problem by first evaporating off the smell molecules, condensing them and storing them, then evaporating off the water to leave the solid coffee behind, to which you could readd the smell molecules. And that, greatly simplified, is how they make instant coffee in the first place! Skittle 23:31, 15 March 2007 (UTC)

Loss of memory caused by aging

What are some of the clever ways old persons use to overcome the effects of their gradual loss of memory? 71.122.101.15 19:36, 15 March 2007 (UTC)

Constant social interaction seems to be important. I'm sure you can find numerous scientific studies which support this idea. Nimur 21:33, 15 March 2007 (UTC)

Forgetful people in general have lots of tricks. Lists and daily calendars are widely used, as well as personal organizers which alarm to remind of appointments. Pill minders (boxes with compartments) help keep track of whether medicine has been taken. There are electronic beepers which can be used to find important objects. Then there is the old trick of checking whether the toothbrush is wet. One common trick is putting a note where it will be seen: on the refrigerator or inside the front door, with a reminder. Some phone message systems allow you to prerecord a phonecall to yourself with a reminder. Edison 22:13, 15 March 2007 (UTC)

Technology

I can't think of any way technology has improved product safety. Can anyone help me? I can only think of ways technology's made things more safe for workers. Also, I don't really understand the control system article. A question I have is to "Describe the stages of a control system you have studied." I have to specify the input, process and output (each is worth 2 marks). I haven't studied a control system so I don't know what the article is talking about. For the thermostat example at the control system article, I would guess that the input would be whether the room temperature is lower than the temperature the thermostat is set at (A) or not (B). Would the process be to turn the heating on (A) or to leave it as it is (B) and the output be (A) more heat to the radiators or (B) be no heat to the radiators? Thanks, My Username is... 20:10, 15 March 2007 (UTC)

As for the product safety issue, wouldn't seat belts count? Airbags? Dismas|^(talk) 20:12, 15 March 2007 (UTC)

Yeah, they would! The only thing I could come up with was making edges round but that's always been done (except on knives!) Thanks, Dismas! My Username is... 20:14, 15 March 2007 (UTC)

I don't really understand the question, but I'll have a go. How about using technology to test donated blood for infectious diseases? Blood is the product, the technology is used to make it safer... Aaadddaaammm 20:31, 15 March 2007 (UTC)

For the thermostat example, I think it would go a bit more like this (I'm kind of assuming it's analogous to a function in programming):

• The input is the value of the actual temperature (measured by a thermistor or thermocouple)
• The process is comparing the input temperature to the setpoint temperature
• The output is the signal sent to the heating/cooling equipment to adjust the temperature

— Matt Eason ^{(Talk &#149; Contribs)} 20:35, 15 March 2007 (UTC)

Every day, engineers and scientists make your life safer and you probably don't even know it. Bridges, highways, automobiles, electric lighting, cell phones, textiles, medicine, ... you wake up each day without electrocuting yourself, poisoning yourself, getting crushed, ... Yikes. I don't even know where to begin. Think of anything you do, and then think about all the ways that you might die by doing it. You can guarantee that somebody else has thought of a technological solution to make sure you don't.

Regarding Control Systems, think about the last time you were in a car. The driver presses the brake pedal. This is the input. The car's hydraulic system senses the pedal, applies the brakes in a controlled, safe way to slow the vehicle without flipping over or crashing. This is no easy task! Applied too rapidly, the car would swerve and you would slam through the front window. Applied too slowly, the car will keep going and hit whatever you tried to avoid. Somewhere in the middle is a safe, controlled braking time. This process may involve mechanically calibrated pipes or hoses, a master cylinder, and electronic and computer assisted control such as ABS. Finally, the output is a mechanical clamping of the wheel (the brake shoe), and the safe slowing of the vehicle.

I suggest you think about all the things you use every day. Every little task is very simple, but imagine what it takes to make it so simple. THAT is technology, and it is everywhere. Nimur 21:04, 15 March 2007 (UTC)

Thanks for all your help I understand it now (I think!) My Username is... 21:16, 15 March 2007 (UTC)

Additionally mass production has reduced hugely the amount of goods that are of differing quality. Consistency and reliability are huge. As things are made not in small batches but by the millions the process is so well honed that there is minimal wastage (as that drives up costs) and maximum repetition quality. Technology has also allowed for things such as computer-model testing of quality/safety features. Measuring using lazers has helped make sure that the quality of huge products (such as ships/planes) are made to a degree of accuracy that is almost mind boggling. Automated control of production and automated stress/safety testing has led to an increasing in qulaity and therefore safety. Of course many will argue that because mass-production is so popular the real quality is now found in batch/small scale production. This shouldn't be taken to mean that unautomated-production = higher quality, rather that maintaining quality over millions of units is harder than over just 100s. Hope this helps ny156uk 21:55, 15 March 2007 (UTC)

Is that more because people equate quantity with reduced quality; people's desire to possess something unique?

Accidental electrocutions have been reduced in number by the requirement that all bathroom and kitchen outlets where an appliance might be close to a tub or sink be protected by Ground fault circuit interrupters which was a simple concept borrowed from the utility industry. Edison 22:02, 15 March 2007 (UTC)

Product: Shaving Razor

Technology: Safety Razor

202.168.50.40 23:16, 15 March 2007 (UTC)

Osteon

Are primary osteons the interstitial lamellae i.e. the initial bone synthesised from woven bone? Does that therefore make secondary osteons the 'complete' osteons (usually just referred to as just osteons)? Or is the woven bone itself the primary osteon? With remodelled bone the secondary osteon. Thanks in advance.

Primary osteons can form their lamellar calcifications in a matrix of woven bone. During formation of secondary osteons, osteoclasts degrade much of the structure of the earlier bone allowing a new organized array of secondary osteons to form. The term "interstitial lamellae" is used to refer to remnants of earlier osteons that are scattered around between more complete osteons. Take a look at bone, this and this. --JWSchmidt 03:41, 16 March 2007 (UTC)

earthquakes

Can you feel earthquakes in an airplane? —The preceding unsigned comment was added by 69.108.166.83 (talk) 00:05, 16 March 2007 (UTC).

No. [Mαc Δαvιs] (How's my driving?) ❖ 00:18, 16 March 2007 (UTC)

Unless the airplane is on the ground. [Mαc Δαvιs] (How's my driving?) ❖ 00:18, 16 March 2007 (UTC)

Secondary question: Could a seismic instrument of some sort detect an earth quake from a plane in flight? I imagine a precise radar altimeter or some sort of laser might possibly detect ground vibrations. There would be some severe signal/noise issues, as the airplane jostles through turbulent air. I can't imagine that acoustic waves would propagate to the height of the aircraft via the air, but would another technology work around that limitation? Nimur 00:51, 16 March 2007 (UTC)

I doubt it, because using a fast moving object as a frame of reference to measure something not as fast probably won't give you very good results. --Wirbelwindヴィルヴェルヴィント (talk) 03:11, 16 March 2007 (UTC)

Add to that the shakiness of a plane. Even an apparently smooth airplane ride would affect the seismometer a lot. − Twas Now ( talk • contribs • e-mail ) 04:19, 16 March 2007 (UTC)

incandescent/florescent bulbs

Since incandescent bulbs emit 95% of the energy consumed as heat, wouldn't that make them more efficient in colder climates or winter. where it would spare the heating system extra work? Dan Oprisko (email removed) —The preceding unsigned comment was added by 70.174.95.114 (talk) 00:28, 16 March 2007 (UTC).

If the furnace were an electric heater, you are correct. If it were gas heat, which is somewhat more efficient, I think the increased heating due to the lightbulb would be less efficient than the gas it would replace. Nimur 00:48, 16 March 2007 (UTC)

PS I have removed your email address to minimize spam. Nimur 00:49, 16 March 2007 (UTC)

If you have a use for the heat, then sure, it's no longer "wasted", but you've done nothing to improve the efficiency of the conversion to light. Regardless of the type of light source, converting electricity to light is pretty inefficient so you'll always have some heat to heat a building with in the winter. Atropos235 00:52, 16 March 2007 (UTC)

If it isn't glowing, then what is it?

A recent question brought up the Magnet viewing film. This piece of film/paper undergoes a color change in the presence of a magnetic field. I created the article, and User:SteveBaker made the valid point that glowing requires energy. Does anybody know if the strip is actually emitting light, or if it is just undergoing a color change to a lighter shade of green? Is energy being absorbed from the magnet? Could that energy be converted to light? Nimur 00:54, 16 March 2007 (UTC)

From [20]

When a dc magnetic field is applied to the bonded film, the nickel particles congregate in alignment with the flux lines emanating from the dc magnetic source. This mass grouping together of nickel particles causes a darkened appearance to the film directly where the magnetic field is impinging on the film. As a result, an exact two-dimensional image or impression of the magnetic pole or pole pattern (if there are more than one) is produced. This image is easily erased once the film is removed from the magnetic source and the nickel particles are allowed to freely re-disperse within their gelatinous cells. A common bar magnet can be swiped across the film to ensure complete erasure of the previous image, or by reapplying the film to another magnetic source the new image produced will completely replace the old one.

Atropos235 01:08, 16 March 2007 (UTC)

Fall in a barrel of water

Background: To my understanding injuries/death from a fall (of a human) of a considerable height result from the differences in deceleration of the different body parts on impact (i.e. legs break, because feet stopped and legs still have downwards speed).

Now what would happen if you would suspend (diving somewhere around the center of the water mass) yourself inside a large barrel of water and that barrel would be dropped?

Would it make a difference whether the top of the barrel was closed or not? —The preceding unsigned comment was added by Lukas.S (talk • contribs) 02:17, 16 March 2007 (UTC).

I thought it was because of the bouyancy of water. Even though water is fluid, the surface tension forever over the area of a human body takes considerable force to break, so I would think that because the barrel is the one penetrating the water, the human inside would suffer less damage. --Wirbelwindヴィルヴェルヴィント (talk) 03:09, 16 March 2007 (UTC)

hmm, curious question, you mean the barrel with water and human are dropped onto the round right? Not into water? If so then you have to remember that a breathing human is actually not as dense as water so being suspended in water and dropped, I don't know if that saves you from any impact, wouldn't you still feel exactly the same force since the water is de accelerating just as fast as you? There is a big difference if you jump into a body of (relatively) stationary water. Vespine 03:31, 16 March 2007 (UTC)

I'd guess that if you were kept submerged in an unbreakable tank of water, sealed to prevent it spilling out when weightless, and dropped you would not suffer any bone injuries like you would in an ordinary fall. However, beyond some threshold the compressible air spaces of your body would experience a shock too great and might turn into a bloody pulp. Very interesting question. atropos235 ✄ (blah blah, my past) 03:51, 16 March 2007 (UTC)

Thanks for the ideas. Wirbelwind, the idea was to drop the barrel onto land, not in water. The barrel is filled with water. So does anyone have an idea what height would be actually survivable? Escape barrels instead of parachutes? : )Lukas 04:00, 16 March 2007 (UTC)

Real Population Density

This question is one I've researched a couple of times in my life and, for me, comes under the heading "Questions that seem important but I don't see a lot of attempts to answer it". Basically, the question is: what is the real population density of earth (or could be asked of a nation or area) given the amount of usable land and resources available? When I last tried to answer the question for the date 2050 AD, I assumed that the population would be 9 billion and the land area was 57,500,000 sq miles. This gave a crude density of 157/sq mi. However if only half the land is usable (not ice, rock, desert, etc.), then the density would double at 313/sq mi. So, different answers depending on assumptions about usable land area. If resources were taken into account, the answer would be more complex in that mere square miles of land would then become unit-areas of viability in some way of measuring that. So, anyone have any ideas on the topic, or know of interesting efforts to answer this? --Quark —The preceding unsigned comment was added by 71.58.57.171 (talk) 03:43, 16 March 2007 (UTC).

Very few parts of the world are totally inhospitable to humans, that is where they cannot be self-sustaining. The south pole is such a place, but if history has taught us anything it's that people are insanely good at adapting to virtually any environment. Native people live in Siberia where it's rarely above freezing. The Sherpa live miles above sea level in the Himalaya, where it isn't very kind either. Carrying capacity is the term that describes the theoretical limit, but this limit constantly changes, usually upward, due to innovations in technology, occasionally down, because of things like localized climate change (drought) -- atropos235 ✄ (blah blah, my past) 04:32, 16 March 2007 (UTC)

Butter or Spread

I just learned that even though the spread I eat, country crock, says it has 0 trans fat, it could actually still have some because the FDA allows any product with less than 0.5 grams of trans fat to be declared trans fat free. I looked at the list of ingredients and sure enough it contains partially hydrogenated oils. I have been browsing the internet, and while I learned that trans fat is very bad so is saturated fat as well to a lesser degree.

So should I go with the spread that has between 0 and 0.5 grams of trans fat, 1.5g saturated, 2g monounsaturated and 3.5g polyunsaturated

or

butter, which is pure saturated fat? Which one is healthier?