Wikipedia:Reference desk/Archives/Science/2007 January 20

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1 January 20

[edit] January 20

[edit] What does RCSWI mean?

I have a card from a Psychotherapist that has RCSWI along with Ph.D. and MSW. I know what the latter two mean but I cannot seem to find out what RCSWI means. Can anyone help me?72.153.131.41 01:31, 20 January 2007 (UTC)

Rape Crisis Social Work Intern --CBD 15:34, 20 January 2007 (UTC)

[edit] Paracetemol

Is paracetemol completed metabolised by the liver, or does it remain in the body? The Paracetemol#Metabolism section helped a bit though, very sciency :/ Thanks, RHB ^{Talk - Edits} 01:59, 20 January 2007 (UTC)

The vast majority of paracetamol (acetaminophen, for those to the west of the Pond) is indeed metabolized in the liver. About five percent gets excreted in a chemically unchanged form; see [1]. Most of the rest (about 90%) gets combined with glucuronide and sulphate and excreted; another five percent of a typical dose ends up oxidized to benzoquinoneimine: the toxic species in a paracetamol overdose. (The liver can normally detoxify benzoquinoneimine by combining it with glutathione and further matabolizing it; in an overdose the liver's supply of glutathione is depleted, resulting in an accumulation of benzoquinoneimine and toxicity.) TenOfAllTrades(talk) 02:15, 20 January 2007 (UTC)

[edit] Accented beats in music

How much louder are the accented beats (on 1 and 3 say) than the other beats in dB?

~~There is no standard; you should just make them noticed over surrounding,~~ If the note has a marcato accent over it, you should play them louder than surrounding unaccented notes. If it doesn't there still is no standard, however you should not make it that significantly noticeable. X [Mac Davis] (DESK|How's my driving?) 05:36, 20 January 2007 (UTC)

The question doesn't make sense and indicates a basic misunderstanding of the concept of accent. Metric accents ("on 1 and 3 say") are distinguished only by their position in the rhythmic structure and are often softer than other notes. Even dynamic accents, the only kind which are necessarily louder, can be louder by any amount, from the just noticeable difference to the entire dynamic range of the instrument or ensemble. —Keenan Pepper 19:51, 20 January 2007 (UTC)

[edit] RF Load

Greetings, I am building a RF Load as a part of engineering sylabus. I want to know why the resistive element is kept in a exponentially tapered housing. Why exponential? How will it vary the resistance in the resistive element? —Preceding unsigned comment added by 203.187.198.33 (talk • contribs)

You dont say what freq you are operating at, but I dont think theres any need to make the housing exponential in shape. (think of Waveguide loads for example -threy arent exponetially varying in dia. However, since the RF energy flows through the dielectric rather than the conductors, any absorbing elements should be placed in this path such that the energy enters them sideways.. ie the load resistors should be wired radially from the centre conductor to the screen. It is prefereable to use many(low inductance) load resistors spread around the circumference of the screen to absorb all the energy. Resistors placed in the cenetral conductor will appaer inductive and will not give a good 'match' to the source. xxxx —The preceding unsigned comment was added by 88.109.209.79 (talk) 02:22, 21 January 2007 (UTC).

Thank you for your swift reply. I understand what you have mentioned. But the question still remains. If you say exponentially tapered housing is not necessary then why all manufacturers use it? I have tried to contact the manufacturers but haven't got any reply yet.

(Cant resist this one) Exp matching sections act as impedance transformers, though why you would need one in a well designed load, I dont really know. Do you have any pics or diagrams of the loads you describe.?--Light current 05:13, 21 January 2007 (UTC)

OTOH, having thought about this, I think if the load resistor was axial in the centre conductor, and the outer shield dia was to taper (conically) from the cable dia down to zero (where the other end of the load resistor is connected), then this would probably give a good match. THis would be because the line imepdance gets lower and lower as the wave travels towards the earthing point due to the changing dimensions.

However, I do not know if any commercially produced loads use this technique. Maybe the very high power water or oil cooled ones do. —The preceding unsigned comment was added by Light current (talk • contribs) 17:26, 21 January 2007 (UTC).

(Moved from my talk) Thanks a lot for that stuff on RF Load. Yes, you are right. Conical tapering is used in high powered Loads that are oil cooled.

--Light current 05:46, 22 January 2007 (UTC)

I vaugely seem to remember some (RF?) components that were shaped like 2 cones joined together at their open ends. THis could hve been for:

increasing diameter of the both inner and outer (at constant impedance (50R)) to allow for large dia of resistor cf inner of cable.
decreasing dia of outer towards earth to give decreasing impedance towards the apex of the cone wher the other end of the resistor is terminated.

I cant remember where I ve seen these things! Pictures would be nice. --Light current 16:04, 22 January 2007 (UTC)

Aha! the almost complete answer to the question! [2] --Light current 21:34, 22 January 2007 (UTC)

Thanks for the continued interest. I am not able to get the equations for the tapering? Related to frequency I am sure but how exactly I cannot fathom? I would put snaps of the tapered loading, only I dont how to put pictures. Am a new user so you'll have to help with that too

Hmm. Did you not look at the reference I linked in my last post above? It gives the formulae--Light current 15:49, 23 January 2007 (UTC)

Thanks a lot.. I did overlook the link before but now i got it. Anyway do tell how to put up pictures here for u to see??

To upload a picture: just click on 'upload file' and follow instructions --Light current 20:12, 24 January 2007 (UTC)

[edit] Further details from OP

why the tapered housing is needed in rf load? and what the dimensions of housing? means what is the distance between the housing wall and resistor?i m designing rf load for frequency up to 3 ghz and power rating up to 600watts.

I'm not totally following your question, but you need to be thinking about transmission line effects in your leads at high frequencies. -- mattb @ 2007-01-24T15:59Z

The design I referenced is designed to work well upto a few hundred MHz I think. You need a proper microwave load design really. You may get away with the exponential housing and axial resistor idea, but your acuracy is going to have to be very good to get a good match at 3 GHz. Do you have a target for the return loss in dB? --Light current 17:23, 24 January 2007 (UTC)

[edit] Waveguide or coaxial cable feed?

Really the design of your load will need to be urgently considered with regard to the feeder. Microwave loads look a lot different from those for a few 100 MHz. In all, I dont think this is a simple project for one inexperienced (like me) at these frequencies. --Light current 18:11, 25 January 2007 (UTC)

[edit] Silicon oil

I am making an oil cooled RF Load as a part of my project. I am thinking of using Silicon Oil as the coolant. Can anybody tell me the electrical properties of Silicon Oil, please?

As the large notices at the top of the page say, this is an encyclopaedia. The answers you are looking for are here. yandman 14:15, 23 January 2007 (UTC)

What about transformer oil? Also can you not tell us what power and at what frequency you are dealing with. THis would make it easier for us to help you!

See Transformer oil. See also Material Safety Data sheets for any insulating fluid you choose. A generation ago the Heathkit company sold the Cantenna [3] for ham radio operators to use as an artificial load for transmitter testing. It was a looked like a big paint can with resistors inside. The instructions said to fill it with transformer oil. The source above says they ship a can of oil with their recycled Cantennas. They might sell the oil alone. I suppose some hams just asked nicely at the testing/maintenance department of the local electric utility, who buy the stuff by the drum or by the train tank car load. Do not even consider just draining or siphoning oil from a transformer. See also [4] for home brew 1 KW wet dummy loads. See also [5] re: transformer oil sources. Utilities once used mineral oil in transformers to cool and insulate the transformer windings and core. It had to be tested with a high voltage tester to make sure the moisture content and acid content was excruciatingly low, because any moisture would reduce the insulating quality and cause flashovers. It was flammable. Askarel/Pyranol/PCB was used instead of oil as a nonflammable (or less flammable) coolant and insulator until the 1970's, but electrical arcing would convert it into dioxin, very bad stuff. Old utility transformer oil (mineral oil) was likely to be somewhat contaminated with PCB because the same tanks and filter presses were used for both oils. Utilities went through a frenzy of testing and elmininating PCB, but some transformers may still be PCB contaminated. Motor oil is not recommended as a substitute. The replacement for Askarel was silicone fluid, which had many of the same advantages as Askarel, but could reportedly explode if it had much moisture in it and there was an arcing fault in the transformer. So dry silicone oil is a great insulator and a good heat transfer medium, but explosive if contaminated with moisture and exposed to high temperature and electrical arcing. It is far less of a biohazard than Askarel or petroleum oil. Online I do not see any references to the usability of silicone oil in a cantenna, so you would need to do further research into the feasibility. For safety, be aware that under extreme heat or in the presence of arcing, transformer oil can break down and release combustible gasses. If there is sufficient oxygen in the enclosure, in the presence of a flame or spark these can detonate and rupture the container, followed by an intense oil fire. The fluid expands when heated. Part of your design can be looking at the specific heat of the fluid you use to see how much it will heat up over how long (neglecting radiation out) and its expansion coefficient to see how much that would make it expand. It could come squirting out a relief valve on the top, so provide for that with containment under the can. Your RF load must somehow make provision to transfer the heat of the power dissipated to the surrounding atmosphere by some means. That is an essential part of the design. Youi might wind up rating your RF load at so many watts for so many minutes like tha Cantenna. A thermometer or thermocouple might be used to sense the oil temp and the resistor temp, with an alarm. If the resistor is partly out of the fluid or in the wrong position there will be local overheating and an danger of fire or explosion. Remember that the device is basically a powerful heating element in a fuel tank. Small oil filled poletop transformers may transfer the heat by internal convection and by radiation and conduction to the air from the cylindrical can itself, or higher wattage units may have radiators on the outside. Substation transformers have pumps connected to the radiators and fans to cool them. On a really bad day, they train fires hoses on the steaming transformers, creating a problem with moisture creeping in. Water cooling was tried, with internal or external cooling tubes and circulating water. This introduces additional obvious mechanical complexity. The internal tubes sometimes leaked. The transformer fluid absorbs oxygen and moisture if exposed to the atmosphere; a dry nitrogen blanket is often placed above the oil level in a transformer. Filling a container to the brim and sealing it will be a problem because of the expansion of the fluid when heated; some utility transformers had a conservator tank above the transformer to make sure the oil could expand but the trnansformer stayed full. The conservator had a pressure vent for air to go in and out. Electrical transformers filled with oil must be in special fire resistant transformer vaults if indoors. Transformers and oil filled circuit breakers are provided with pressure relief. You are probably aware that the resistance and inductance at DC or audio frequencies will not be the same at RF or microwave frequencies. Good luck with your design. Edison 16:35, 23 January 2007

Thanks a lot!!!

[edit] Head on collision between atoms and thermodynamic temperature

Ok, so temperature is the average kinetic energy of atoms. What if there are 2 atoms with the exact same speed collide perfectly head on at slow speed (ie. not enough to break the atom or fuse them together), would the atoms stop and appearantly lose kinetic energy? --antilived^{T | C | G} 10:45, 20 January 2007 (UTC)

Nope. If they're capable of reacting chemically, then they might form a chemical bond; two hydrogen atoms will do this, for example. If there's no chemical reaction, then they'll just bounce off each other. If you roll two billiard balls towards one another, you'll see the same phenomenon—the momentum and kinetic energy of the system will both be conserved. TenOfAllTrades(talk) 10:54, 20 January 2007 (UTC)

OK, guess I forgot that the third law applies to atoms is well... :p --antilived^{T | C | G} 11:03, 20 January 2007 (UTC)

To clarify - the temperature of a substance is a measure of the average energy of its atoms or molecules; for an ideal gas, we assume that there are no intermolecular forces and that collisions between one molecule and another and between molecules and the walls of the container are perfectly elastic; with these assumptions, we can use the kinetic theory of gases to determine that the temperature of an ideal gas is proportional to the average kinetic energy of its atoms or molecules. Note that if the gas is not monatomic, some of this kinetic energy will be rotational energy. The assumption of perfectly elastic collisions is required so that the total kinetic energy of the atoms/molecules is conserved in inter-molecular collisions. Note that this is not a consequence of Newton's third law, because Newton's third law also applies to inelastic collisions. We can show experimentally that real gases behave as if they were ideal gases under most conditions, but the ideal gas model does not work at high pressures and low temperatures. Gandalf61 13:42, 20 January 2007 (UTC)

[edit] Vocal loading

I show show all the signs of overloaded vocal cords. I have a relatively low pitched voice (for a male), and though I was quite a mumbler when I lived back home, since I've been overseas, I have to clearly pronunciate myself in English, not to mention that I'm speaking another language half the time, one that doesn't give many allowances for "mumbled speech". This causes extra strain on my vocal muscles, even to the extend that I get very tired after a day of simply talking. Another one of the symptoms listed for vocal loading is a limited vocal range. When I was young I had a decent singing voice, I could hit all the notes, even if it wasn't the most beautiful voice to listen to. After puberty my vocal range completely dissapeared and I can no longer sing even easy songs without fading out on slightly high or low parts (becaues I'm already singing at a lower octave).

It's quite frustrating! I try to conciously decrease the volume of my voice, and at times I will even press on my neck while talking in order to reduce the vibrations/slightly decrease the tone of my voice, but that doesn't really do anything at all. Does anyone know of a way I can get beyond this vocal loading? If I could just somehow increase the efficiency of my speech voice, or increase the strength of my vocal muscles without tiring them out. 222.158.163.22 12:15, 20 January 2007 (UTC)

This is a bit of a personal medical question, so we can't really do much for you (see the preamble at the top). But I've had the same problem when I was choir singing. Gargling with salt water helps, but you should see a voice coach to stop doing what you are doing to the chords. Nevertheless, I had to give up choir singing. :( --Zeizmic 13:07, 20 January 2007 (UTC)

From personal experience, I suggest you schedule a consultation with a laryngologist (or ENT, i.e. ear, nose, and throat specialist), a physician who will examine your vocal cords for structural damage and other abnormalities. Ruling out these, you may be referred to a speech therapist who will evaluate how you use your voice and provide remedial exercises. In my case, a course of this sort of therapy succeeded in resolving an actual case of vocal cord nodules that might otherwise have been treated by surgery - and the latter might not have prevented recurrence anyway. Be sure to mention your particular vocal activity (everyday as well as singing) to the doctor and therapist. -- Deborahjay 16:03, 20 January 2007 (UTC)

Further: consider that like any medical condition that can become more serious, catching it in its early stages improves your chances for a less-invasive, more successful treatment. A related therapy worth investigating is the Alexander technique, though this is along the lines of treatment and not a substitute for diagnosis. Otherwise, as a vocalist you may benefit from voice coaching, particularly breathing techniques that will help you learn to produce sound more effectively without undue strain on your vocal cords. -- Deborahjay 17:16, 20 January 2007 (UTC)

Sorry, I'm not a vocalist, I didn't mean to put across that message. And it's nothing serious, really. If I speak to someone from my hometown my voice naturally relaxes a level (and I start mumbling again), and I feel no stress in my vocal cords while talking any more. It's been 3 years and it hasn't gotten any worse or better (it's not painful or anything, I just can't belt at all), so I was just wondering if there was any way I could personally train my voice, without resorting to something like therapy. 222.158.23.50 04:48, 21 January 2007 (UTC)

To "personally train" without knowing the nature and extent of any structural changes to your vocal cords, may not yield much in the way of meaningful results. Perhaps you can retrain bad habits that may be causing further, cumulative damage: see new content I've added to the laryngitis page. -- Deborahjay 07:22, 27 January 2007 (UTC)

You describe your voice "relaxing" when you speak to someone from your hometown – does this mean, in your native language? If so, I'll offer the following personal anecdote as testimony (FWIW): In my early years of living overseas and speaking a foreign language (unrelated to my native English) on a daily basis, I had a prolonged case of hoarseness that led me to consult an ENT. Laryngoscopic examination revealed I'd developed vocal cord nodules, a chronic condition resulting from cumulative ill-use of my voice in speaking (including working in a preschool) and performing as an amateur vocalist. I was referred for speech therapy to see if this noninvasive treatment would alleviate the condition. The therapist assessed my speech in both Hebrew and English, while determining the natural pitch of my speaking voice. It became apparent that in order to modify my objectionable "American accent" and to approximate a native pronunciation of certain guttural consonants, I was (though not consciously) mimicking the voices of female television announcers - several tones lower than what was natural for me. Correcting this abusive practice required a conscious effort for some weeks to months to maintain and become accustomed to my natural pitch, but the results were conclusive. The nodules resolved (confirmed on followup laryngoscopy). I had a recurrence some years later, due to increased activity in amateur vocals. At that time, a voice coach determined that I was attempting a too-low range. The new nodules resolved conclusively after a booster course of speech therapy and drilling. -- Deborahjay 08:39, 27 January 2007 (UTC)

[edit] Arun arun arun

what is the fullform of AAA used in dry batt
what are the names of black and white keys of piano or synthesizer?
what is the name of suicide by cutting wrist?

—Preceding unsigned comment added by 221.134.58.145 (talk • contribs)

1) I don't think it means anything. There are C and D batteries, as well as many others.

2) Major scale is the closest answer I can give you

3) Exsanguination, I think. — Kieff 13:22, 20 January 2007 (UTC)

1) I'm guessing one A stands for alkaline. -Obli (Talk)^? 13:28, 20 January 2007 (UTC)

No, it doesn't. AAA refers to the size only. See battery (electricity). They are not necessarily alkaline batteries. The keys on a piano keyboard don't have names, but the notes they play do. See musical keyboard.--Shantavira 14:04, 20 January 2007 (UTC)

The words "Naturals" and "Accidentals" are used for the white and black keys respectively. See Musical keyboard. I found the article by looking for Key, and then, under "Music" heading, for Key (instrument), and thence to "See also musical keyboard". --Seejyb 21:23, 20 January 2007 (UTC)

Well, no, actually: for example, a C-flat would be played on a white key (B), a C-double-sharp on a white key (D), and both are accidentals, given, say, a key of E-flat for the C-flat, and D-sharp minor for the C-double-sharp. I have fixed the musical keyboard article accordingly. White keys and black keys are absolutely not called "naturals" and "accidentals", at least not by any trained musician. Antandrus (talk) 02:47, 21 January 2007 (UTC)

They are supposed to be natural and accidental based on C Major. --Kainaw ^(talk) 12:37, 21 January 2007 (UTC)

As a group, the white keys are known as "the white keys", and as a group, the black keys are known as "the black keys". Individual keys do have individual names (I must respectfully disagree with Shantavira about this). When I touch "middle C" on a piano, I am touching a physical object. The note made by depressing that key is called "C". JackofOz 03:56, 22 January 2007 (UTC)

[edit] Metal identification and care

I recently moved into a new home, with a gas stove included, and would like help in identifying the "splash plate" underneath the stove burners. This is designed to be removable so it can be cleaned, which I've done. Initially the metal was completely black. This would have led me to think it was cast iron, except that it appears to be too light and didn't show a speck of rust, even when soaked in water. Here comes the odd part, merely soaking it in water changed the color from black to roughly the color of steel. Now this seems quite strange to me, I've never heard of a metal losing it's patina simply by soaking it in water. I didn't add any dishwashing detergent, but some might have gotten on it from when I did some dishes above the soaking plate, by hand. At any rate, I was quite happy, it looked like I only needed to soak the metal in water to get rid of that jet black coating. But, then when I pulled the plate out of the water and left it to dry, it first developed a greyish-blue patina, then turned jet black again, within a day. So much for that approach.

My first question is what metal I have here. I don't think it's steel or iron, as noted above. Aluminum (aluminium, for you Brits) is lightweight, but I believe it oxidizes to form white spots. Magnesium is also lightweight, but flammable, so I doubt if they would use that. Chromium, or at least a chrome plating, would be shinier, I think. I'm thinking perhaps it's tin or nickel plating. Does this behavior sound correct for either ?

My next question is how to keep it from turning that horrid black color. The previous resident just wrapped it in aluminum foil, and I may end up doing the same unless anybody has any other ideas. The oven/stove combo is made by Electrolux, it's brand is Tappan, and it's model is Meadowbrook, if that helps. I'm guessing it's pretty old, perhaps as old as the 1920's, as that's when the house was built. StuRat 19:01, 20 January 2007 (UTC)

Is it magnetic? Could the "patina" actually be some kind of coating? Im think the colour may have something to do with the surface being microscopically rough and the water filling in the holes so to speak. Although come to think of it, that usually makes a material become darker when wet. Theresa Knott | Taste the Korn 09:10, 21 January 2007 (UTC)

A magnet does stick to it, yes, so it's likely steel underneath. I've concluded it's got a thick layer of chrome plating, too. It doesn't have the shiny look I associate with chrome plating, which threw me off at first, but chrome plating apparently loses that shininess with time and heat, as per the next response. The lack of rust would indicate that the chrome plating hasn't yet eroded through, however. StuRat 06:32, 22 January 2007 (UTC)

~~I'm guessing it's probably thin steel with a Teflon coating, although I've never noticed a color change from soaking those in water.~~

[For electric stoves, which you don't have, and which I bring up only because I'm an idiot who wasn't paying attention,] You can buy replacement stove pans in many stores, of a universal design that (in the U.S., anyway) fits most "ordinary" [electric] stove burners. I generally see these in two styles: chrome-plated steel and Teflon-coated. The chrome-plated ones wear out after a while: the chrome pits through, the steel begins to rust, they get less and less shiny and more and more difficult to clean. Presumably the Teflon-coated ones are supposed to be "better" at this. But I believe (unsourced, original-research opinion alert:) that this is fallacious: for one thing, Teflon coatings eventually wear off, too, and for another, black is a horrible color for stove pans. Since it absorbs heat, the pans get wickedly hot, and any spilled food just gets baked on more strongly.

I've decided that the right approach to [electric] stove-pan cleanliness is to (a) use the chrome-plated ones, which reflect heat instead of absorbing it and are therefore likely to be more efficient to boot, and (b) simply replace them every year or two when they start getting dingy-looking -- they're really not that expensive. (You spend much more time than they're worth trying to clean them when they're corroded, or painstakingly wrapping aluminum foil over them, which of course looks dreadfully tacky.)

—Steve Summit (talk) 16:06, 21 January 2007 (UTC) [edited 00:43, 23 January 2007 (UTC)]

I would guess I have the chrome plated steel. I will look for replacement parts. Each plate is for two burners, is this standard ? I agree that the aluminum foil looked tacky, that's why I removed it (the previous resident had left it that way). BTW, why don't they use stainless steel ? Doesn't that hold up to the high temps ? StuRat 06:21, 22 January 2007 (UTC)

I'm sorry, I wasn't thinking, and I didn't pay attention to the fact that you said you had a gas stove, and consequently my answer is rubbish. The "universal" pans I described are for electric stoves; gas stoves don't have them. (And they're for individual burners, never two-burner combinations.) —Steve Summit (talk) 00:43, 23 January 2007 (UTC)

[edit] Sleep and long-term memory

I've noticed something disappointing and strange about my memory. I have always done better than nearly anyone else in my classes in history. On tests covering a week or two of material, I almost always end up on top gradewise. But when I get to exams, although I study as much as--and probably more than--most people, my average is usually far worse in relation to other students than is my short-term test average. I also notice that I have trouble remembering facts from the last year, whereas some students who didn't do as well in last year's class remember dates, names, and similar info from that class now better than I. This is really irritating, so I've spent some time thinking about possible causes. One is that I'm just taking more classes at once than most of my friends and therefore focusing on too much at once, so my memory is, in a way, spread thin. Another idea that came to mind, and one I'd like to verify, is that because I have so much work and stay up so late getting it done, my lack of sleep (usually 4 or less hours of sleep per night) is affecting my long-term memory. I don't know what made me think this. Is that at all a plausible idea? I can't think of anything else. I don't smoke pot often or anything, and I usually have a very good memory and have, for instance, been able to memorize a song's lyrics after just a listen or two and not forget them for many years. Any other possible explanations? Any suggestions? Thanks a lot. Sashafklein 19:28, 20 January 2007 (UTC)

Yes, this is a very plausible idea. Sleep is the time for memories and other information to be consolidated within the brain, so getting half the recommend amount of sleep (eight hours) can't be good for your long-term memory. Please, do yourself a big favor and take a nap right now. :) Vranak

I believe what we memorize (or, more specifically, what goes into our readily accessible "high priority memory") is decided by how important we think something is. Those song lyrics are important to you and history is probably not. You may be able to trick your brain into giving history a higher priority by putting history facts to the tunes of songs you like. Another common method is to repeatedly expose yourself to the thing you want to memorize, as with flash cards. Be sure to repeat this throughout the year to keep the memories "fresh", otherwise your brain decides "I haven't used that bit of info for a while, so it can't be all that important, let's push that memory way into the back room". StuRat 20:58, 20 January 2007 (UTC)

Both of these suggestions are mentioned in the article on Long-term memory (if you remember for a week that is long-term memory). It looks as if StuRat's advice on repetition should work wonders for you - the article has a link to Spaced repetition - and Vranak's suggestion is echoed in the reference to Sleep and learning. So there, the thoughts of two respected editors and all those linked articles seems like the way to go. --Seejyb 21:42, 20 January 2007 (UTC)

I'm going to stick with sleep, because I really do like history, and I'd like to hope my brain doesn't disagree with me. I guess I'll just try to sleep more. Sashafklein 21:43, 20 January 2007 (UTC)

I have a similar but different problem. I forget everything after a long deep sleep whenever I have not had enough sleep and my mind and body begin to shut down by practically putting me in a comma. When I wake up I can not seem to remember the project I was working on or if I do where exactly I left off, especially any completion plans I had for when I woke up. Unless I remember to write down everything before I go to sleep (which the overpowering need for immediate sleep may prevent) I'm totally lost when I wake up as to what I need to do. Keeping constant notes of what I am doing is the only guard against complete and total loss against waking up with no idea of whatever has gone before. [BTW - sometimes I even forget I have made any notes and do not even look for them when I wake up.] -- Barringa 03:34, 21 January 2007 (UTC)

I don't think that's specific to sleep, if you took an 8 hour break without sleeping you would likely also forget where you were when you went back to work. I have the same problem, so either try to find a good "stopping point" (where one task was completed and the next not yet started) or would have to leave myself detailed notes on what parts of the task were done and what parts were not. StuRat 04:40, 21 January 2007 (UTC)

Unfortunately when the need for sleep comes on me its is sudden or instant. Since I multiplex tasks its rare when I have no tasks I'm in the middle of and when this rare occurance does happen its usually close to the time when I've woken up and completed every task and not lilkely to be "called" back to sleep. Also my waking hour vary to such an extreme degree there is not way of projecting. -- Barringa 08:13, 22 January 2007 (UTC)

Are you elderly by any chance ? Those sleep patterns are identical to my father's, he falls asleep mid-conversation at random times of the day. (Small children do the same thing, but you're obviously not a small child.) I think I'll post a question on this at the bottom of this question. StuRat 22:58, 23 January 2007 (UTC)

This is a natural memory trait common among actors. I can read a script a couple time and recite my lines rather well for a few days. Ask me lines from a play I was in last month and I'd be lucky to remember anything from it. I've often been told that if you have to memorize lines, you'll always have trouble. If you have an actor's memory, you'll do well. --Kainaw ^(talk) 12:42, 21 January 2007 (UTC)

If someone read a few lines of the older play, could you then remember what was after that, and after that &c :)Hidden secret 7 18:48, 22 January 2007 (UTC)

No. When the play is flushed it is gone. (I can't avoid dropping names in the next comment, so please forgive.) It often happens during filming, but it usually hard to tell. Sam Jackson had to recite the same line three times in Pulp Fiction (the Bible scripture). Each time he said it with slightly different words. I asked him about it and he said that he is constantly asked to recite that line and he can't remember it, so he asks the fans to recite it to him "just for fun". --Kainaw ^(talk) 04:41, 23 January 2007 (UTC)

[edit] Sleep patterns in the elderly

I've noticed that some of the elderly fall asleep at seemingly random times, when engaged in activities which would keep a middle-aged person awake, like talking or riding in a car. This seems like a mild form of narcolepsy. It's not total narcolepsy in that they still have some control over when they go to sleep, but far less than younger people do. For example, a middle-aged person might start feeling tired but be able to finish their current tasks, get ready for bed, and then go to bed. This process could be stretched over several hours if they have a lot to do. With at least some of the elderly, however, they have a few minutes at best between when they first feel tired and fall asleep, not enough time to finish their current task, get ready for bed, and physically get into bed. They frequently fall asleep where they are sitting, as a result. By contrast, someone with narcolpesy may fall asleep with no warning at all. The elderly also seem to have more shallow sleep and wake up often. So, the question is, what causes these changes in sleep patterns among the elderly ? StuRat 22:58, 23 January 2007 (UTC)

[edit] Why do we steadily lose high frequency hearing ?

I know that it happens, from the teens onward, but my question is why ? If there is enough of an evolutionary advantage for high frequency hearing to have developed in kids, why is it not also as important for adults ? At first I was thinking this high frequency hearing loss was due to listening to loud music, but I believe I may have been wrong on that. Therefore, I need to find another explanation. If it happened only in the elderly (specifically, after the end of the reproductive years), it would be easier for me to understand. StuRat 20:45, 20 January 2007 (UTC)

I expect the higher frequency hairs in the cochlea are damaged more readily. Right now we think it happens because of cumulative damage from hearing any noise, or any noise above 70 dBa (100 was the old number). X [Mac Davis] (DESK|How's my driving?) 21:14, 20 January 2007 (UTC)

Possibly this was all lies, but my teacher told me, a long time ago, it was because the eardrum became less taut over time. As to evolutionary advantage: if hearing is going to lose a certain amount of range, and a certain range is required, I would think it would make sense for children to have unnecessarily acute hearing so that when they lose the higher ranges they are left with enough. Ie. if you need to be able to hear as high as 'b', and you're going to lose 'x', children should be able to hear 'b +x'. The first part of this answer comes from unreliable teachers, and the last part is original research ('what I think'), so don't rely on it or anything. Skittle 22:55, 20 January 2007 (UTC)

I find Mac Davis's explanation very convincing. Hair cells in your cochlea could be to blame. --Kjoonlee 04:00, 21 January 2007 (UTC)

[edit] Atoms & subatomic particles

Can atoms and/or sub atomic particle be viewed under a microscope? I have been trying to get this info for years - ever since I learned about atoms & subatomic particles in elementary school, but have, somehow, not been able to find it.

Thanks, Janet Akpobome

Images of structures at atomic level can be generated using devices such as a Scanning tunneling microscope and an Atomic force microscope. Remember this is not "seeing under a microscope", as we normally think of. If you read the "See also" articles at the bottom of those pages, you would get a wider picture of this field of Nanotechnology. --Seejyb 22:09, 20 January 2007 (UTC)

The phenomenon of "seeing" an object is a result of many photons being emitted from an object's constituent atoms and entering the eye to produce an image. The concept of sight is somewhat difficult to define when the size of the object is comparable to the wavelength of the light being used to see the object. --bmk

Generally speaking, under an optical microscope you cannot differentiate individual atoms, much less subatomic particles. --24.147.86.187 23:33, 20 January 2007 (UTC)

I did find the Gold Foil experiment and the Oil-drop experiment interesting when I was taking a physics course. Those have some relevance with seeing electrons (although you can't see them with a microscope, you can still prove their existance). --Wirbelwindヴィルヴェルヴィント (talk) 08:38, 21 January 2007 (UTC)

An atomic force microscope feels the atoms in much the same way that a blind person feels the dots of braille. I can't think of an analogy for the scanning tunneling microscope :-( Theresa Knott | Taste the Korn 09:03, 21 January 2007 (UTC)

Also see Field ion microscope (and the "See alsos" on that page).

Atlant 00:40, 22 January 2007 (UTC)

[edit] Number of farads per square foot or pound...?

What is the largest capacitor commercially available and what portion of a square foot does in occupy or in the alternative how much does it weight? Also if you know the cost, that too. -- 71.100.10.48 22:30, 20 January 2007 (UTC)

Supercapacitors can be over 2600 farads

Even though I did not find this claim documented in the article that was not the question. 2600 Farads can be achieved using 2600,000,000 1 microfarad capacitors. The question is the largest number of farads per square foot or pound. BTW - please provide your user name or IP when responding. -- 71.100.10.48 03:16, 21 January 2007 (UTC)

Chasing links from Supercapacitor to "Maxwell" to their corporate web site to their product page

[6], I get 3.81 Wh/Kg for the big ones. -Arch dude 18:11, 21 January 2007 (UTC)

The total capacitance in Farads is not the be-all and end-all with respect to energy storage in capacitors. The voltage rating is critically important, since the energy stored varies as the square of the voltage. A 1 Farad 20 volt capacitor would store

$E_\mathrm{stored} = {1 \over 2} C V^2 Joules$

=200 Joules of eneregy. A .5 Farad 40 volt capacitor would store 400 Joules. Keeping the dielectric material the same and the area of the capacitor plates the same, doubling the thickness would in general double the voltage withstand ability of the device, while cutting the capacitance in half, per : $C \approx \frac{\varepsilon A}{d}; A \gg d^2$ . As above this would double the energy stored. If the dielectric were made 10 times as thick, the voltage rating would in general go to 200 volts, the capacitance would decrease to 0.1 Farad, and the energy stored would increase to 2000 Joules. Edison 15:52, 22 January 2007 (UTC)

As far as I know, there are very large capacitors on the powergrid that discharge enough energy to hold up the whole power grid. (For short amounts of time <1sec). Those are probably up on the list of largest commercially available capacitors. Jeff Carr 05:55, 26 January 2007 (UTC)

[edit] Heat

what is heat? —The preceding unsigned comment was added by 68.74.79.7 (talk • contribs).

The article on Heat may be a good place to start. You can search for topics yourself using the seach box on the left side of the screen. Feel free to ask another question if the article is not clear or you still have questions. Thanks and best wishes, --TeaDrinker 01:56, 21 January 2007 (UTC)

Energy in transit according to the article listed above. This sounds about right to me. Vranak

In short though, it's just energy. I'm not even sure I agree with the transit part. --Wirbelwindヴィルヴェルヴィント (talk) 08:27, 21 January 2007 (UTC)

First, remember e=mc²; matter is energy. Second, one does not feel heat unless it is in transit into them. Vranak

I guess an important conceptual detail is that heat and temperature are different, though related, quantities. Heat is the energy, and temperature is the average energy per molecule (often times, the "average kinetic energy of the molecules of a gas"). In this way, something small (with few molecules) can have a very high temperature, but not have much stored heat energy. A good example is "flying sparks," which glow white-hot with temperatures probably in the thousands of degrees Celsius, but with so little actual heat that they are harmless to most things they land on (keyword - most :) Nimur 21:25, 21 January 2007 (UTC)

[edit] water body

If an average human body was completely ridded of bones, organs, muscles, etc, how much water could the empty body hold? assuming it was filled until it was firm, not until it popped. —The preceding unsigned comment was added by 129.123.214.24 (talk) 04:13, 21 January 2007 (UTC).

Approximately the same weight in water as the person weighed before their unfortunate run-in with you. StuRat 04:26, 21 January 2007 (UTC)

Minus the weight of the skin, which takes up 13% of the body weight (http://hypertextbook.com/facts/2001/IgorFridman.shtml). --Bowlhover 05:00, 21 January 2007 (UTC)

So... What would be the average density of the human body? --Kjoonlee 05:41, 21 January 2007 (UTC)

And the average volume? --Kjoonlee 05:42, 21 January 2007 (UTC)

Average density of the human body is about 1.1g per cm cubed, or slightly higher then that of water. Which is why if you are in a pool and exhale as much as you can you will typically sink slowly. So the average volume is just under one cm cubed for every gram of weight, or just under ten cm cubed for every kilogram. Vespine 06:08, 21 January 2007 (UTC)

Surely you mean 1000 cm^3 for every kilogram. --Wirbelwindヴィルヴェルヴィント (talk) 08:21, 21 January 2007 (UTC)

Surely I do, 10cm x 10cm x 10 cm is 1000 cm^3, I had 10 centimeters cubed rather then 1000 cubed centimeters in my head... Vespine 23:37, 21 January 2007 (UTC)