Wikipedia:Reference desk/Archives/Science/2007 February 3

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[edit] February 3

[edit] Abs and Resting Time

How often can you work out your abs without them needing rest? I've heard that you can work out the abs nearly every day, whereas the other muscles need rest. Why the difference? Also, how much resting time is needed for abs? PitchBlack 03:45, 3 February 2007 (UTC)

Do sit ups until it hurts? --Russoc4 04:17, 3 February 2007 (UTC)
I didn't find any real sources, but google results did say to treat your abs like any other muscle and excercize them about 3 times a week. On a related note, 6 Week Abs has 7 myths about abs. I'm curious now too, because when I used to work out (yea, yea, I got lazy), I could lift barely more than I weigh with my upper body, but I can use ab machines at max weight and not have them hurt afterwards while my arms did. --Wirbelwindヴィルヴェルヴィント (talk) 06:19, 3 February 2007 (UTC)
I have never had sore abs when I would exercise them 5-6 times a week, whereas my arms and legs needed a day to rest afterwards. − Twas Now ( talk • contribs • e-mail ) 23:50, 3 February 2007 (UTC)

[edit] A plant that is also a pathogen

I recently added to the article protothecosis that Prototheca was the only known pathogen that is also a plant. I got this from the Journal of Clinical Microbiology. Is it true, or am I forgetting some other plant that causes an infectious disease? --Joelmills 04:19, 3 February 2007 (UTC)

Wow, that's pretty cool. [Mαc Δαvιs] X (How's my driving?) ❖ 05:26, 3 February 2007 (UTC)
Hello Joelmills, this is very nice, but when you're not sure, why not asking before updating ? Now it's only because fungus are not sorted along with plants that your first case [meaning of prototheca] is an 'only plant' candidate. -- DLL .. T 10:57, 3 February 2007 (UTC)

I was sure when I added it, having the reference to back me up and a precursory google search not showing any contradiction. But then I thought that it was a pretty big claim to make, so I better ask here, where I know that there are a lot of knowledgable people. Protothecosis hasn't attracted many edits in the months it's been in existence, so I figured a few hours of waiting to doublecheck something was OK. --Joelmills 19:37, 3 February 2007 (UTC)

[edit] Wireless control

HI friends,I have undertaken a project "Multi-axis wireless control for Robots".In it's details,all I have to do is to control the robot using my transmitter pad.I have planed to use 5 to 6 keypads to control different axis.Then at the receiving end,using some RF module,the data is decoded and it will be used to control the relay using a microcontroller and ULN driver.Which will then be interfaced to PLC for robotic arm movement....For this entry level,I have stuck somewhere in choosing the exact means of communication.At first someone stated to go for IR,later someone suggested RF and now few others state to pick bluetooth for industrial standard...Now I have decided to ask to you guys in this forum so that I can get a good solution for this..For IR based TX and RX,I have seen many circuits practically used,but I still can't get one for multiple device control...For Rf based TX and RX,I tried MAXIM-1472(TX) and 1473(RX)...All pin connections and other spec seems pretty nice but I'm not able to get any practical circuits for it's contruction.I also tried Cypress wireless solution.But the practical construction seems almost impossible...Should I have to only buy modules?.Isn't there any other solution?..Guys can anyone get me some more detailed view in designing using such SOCs please?..I don't know what type of data format that should be used for this chip.No proper details in Maxim Website...I tried...Please someone help me out...And about bluetooth project,I have simply no idea...I thank you all in advance for you consideration..Looking up for the suggestions........ —The preceding unsigned comment was added by 59.96.23.95 (talk • contribs).

I'm slightly confused about what you're asking. When you mean practical circuit, you mean you can't do it because the traces of the MAX1472 and 1473 are too small, or you don't have a schematic? IIRC, one of those is TSSOP and have a pin clearance of like 0.2 mm or something tiny. There are adaptors available for them, I believe, which cost around $10 a piece. But even then, they're surface mount. I'm not sure what your level is, etc, so it's hard to tell if I can even provide you an answer when you ask for a more detailed view in designing. The datasheet usually has that kind of info, and the 1472/1473 uses SPI I believe. If the problem is that you're making prototypes, you should look for DIP packages for chips to construct them easily. Somehow, I doubt I helped any, so do tell if anything applies, and if not, what info you need (design software, RF packages, comparison of RF / Bluetooth / IR, etc). --Wirbelwindヴィルヴェルヴィント (talk) 08:54, 3 February 2007 (UTC)

[edit] How does window gel work?

My kids have window gel toy stickers (hearts, snow flakes, and so on) that stick to non-porous surfaces like windows, mirrors, and metal. They don't stick to fingers. From my research all I've been able to determine is that window gel toys are primarily manufactured in China and South America, mostly Brazil.

What is window gel made of? How is it made? How does it work? Does it leave a film behind? —The preceding unsigned comment was added by Dstinchf (talk • contribs).

They appear to be static cling vinyl. See also Colorforms. --Wirbelwindヴィルヴェルヴィント (talk) 17:50, 3 February 2007 (UTC)

[edit] Unknown Bird

Found browsing flickr : "IF anyone know the bird's name please write clicking the comments link. " http://www.flickr.com/photos/subirbose/167852801/. Seems the guy's photos are from the Himalaya and surroundings. Thanks for your help and more : which method do you use and recommand to find the name of a [living creature] from its photo or sketch ? -- DLL .. T 10:50, 3 February 2007 (UTC)

To find a species, you want to use an Identification key. There are plenty around; you'd need to find one for the class Aves (birds) to find the identity of this bird. Laïka 13:18, 3 February 2007 (UTC)

[edit] Skin aging

I was trying to find some information on the process of the aging of the skin, and I guess both physical aging in general and the (human) skin are not as well covered, unfortunately, as some other biology-related topics on WP. I am particularly interested in how the dermis ages vs. the epidermis - it is my intuitive understanding that while the epidermis' aging concerns wrinkles and other skin imperfections more, it is the dermis' aging that is responsible for the sagging of the skin and the fact that our cheeks and neck don't look south youthful anymore :(

I was inspired to research Wiki for that by reading about this company's product: [1]. Even if their product actually works, it is my understanding that it affects epidermis only (even if it's "all five layers of the skin" as the company claims, I understand it is epidermis), so the product wouldn't prevent the skin from sagging anyway. OTOH, Wikipedia says stretch marks form in the dermis, and the company advertises using a "testimonial" from a customer saying her stretch marks have "faded" after using the product.

OK, what I would like to learn is how the skin actually ages and how, theoretically and practically, it can be prevented/alleviated, and what is the state of research into it - not to mention it would be nice to be able to find out the same about other tissues... I guess it is not a "question" one could answer overnight at the reference desk, I am rather counting on drawing the attention of editors who are into biology/medicine to that topic. It wouldn't hurt, though, if somebody could provide a quickie lowdown on the topic here :D

Thanks a lot to any merciful soul who would take interest in that request. PrinceGloria 11:17, 3 February 2007 (UTC)

[edit] Energy saving Light bulbs?

I'd like to know just how much energy it takes to make an energy saving light bulb compared to the older glass filament type. It is widley known that the energy saving kind will use less energy to generate light of a similar intensity as a filament type and will last around ten times longer. But what about the enery of production? Hesaurus 12:37, 3 February 2007 (UTC)

See Talk:Compact fluorescent lamp#Energy used to manufacture CFLs Rmhermen 01:38, 4 February 2007 (UTC)

[edit] Genetic Variation in and between Populations

I have heard many times, normally when discussing race and whether it exists, sentences like (and this is a real example from the reference desk) "there is more genetic variation among Africans than there is between Europeans and Africans". What does this mean? That a randomly selected African will have more in common with a randomly selected European than another African? Because that sounds hard to believe. Or that the standard deviation in the African population is larger than the differences between an average European and African? 85.1.5.207 13:37, 3 February 2007 (UTC)

It means that there is more genetic variation within an African population than within a European population, measured by things like the number of minor varieties of genes (called polymorphisms). The most economical explanation is that several African "peoples" (i.e., populations, like Bantu, Khoisan, etc) partly separated from each other far longer ago than did the various European "peoples" (like Nordic, Mediterranean, Basque, etc). It does not mean that a random African is likely to share more gene polymorphisms with a random European than with another African. alteripse 14:22, 3 February 2007 (UTC)
Thanks, although the statement made seems to suggest that there is more variation within Africans, than between Africans and Europeans. Are people who make this statement misunderstanding the claim, or is this a different claim? It is normally made in the context of proving how similar humans are, so we shouldn't be racist. Maybe it should be that we shouldn't lump all blacks together as one, which we don't do to white Europeans.85.1.5.207 14:45, 3 February 2007 (UTC)
Which "statement made"? A number of research studies have shown more genetic variation among the large population of people whose ancestors lived in Africa a couple of centuries ago than among those whose ancestors lived in Europe a couple of centuries ago. I do not know how to say it any more plainly. This statement itself is neither racist nor anti-racist. All of us recognize gradations of physical difference more easily among those who are most similar to the people among whom we grew up. This is the origin of the "all ___ look alike to me" kind of statement-- it reflects a nugget of truth about human perceptions and recognitions of other people, but it is an entirely relative fact, as the same assertion can be made by a member of the "other" population. Or should I have simply stopped at the first sentence? alteripse 23:34, 3 February 2007 (UTC)
It means that two randomly selected Africans have less in common with each other than the average African has with the average European. − Twas Now ( talk • contribs • e-mail ) 23:43, 3 February 2007 (UTC)
The above statement is true, however: there is more genetic variation among Africans than among any other group (Asians, Native Americans, Europeans, Australian Aborigines). This is, in very simle terms, because they have been there the longest. − Twas Now ( talk • contribs • e-mail ) 23:45, 3 February 2007 (UTC)
Thanks to both of you. Alterprise, the statement I was referring to was the quote in my original post, but thanks for your info. The stuff I mentioned on racism was simply to try and clarify the difference between your explanantion and how I interpreted the original quote. Obviously facts cannot be racist or not, they are simply facts. Also thanks Twas Now for your answer, that would have been my guess but the statement seemed open to interpretation. (Same user - different IP!)137.138.46.155 08:05, 5 February 2007 (UTC)

[edit] Sex in evolution

How can evolution explain how species evolved sexes? The primitive life forms didn't have sexes, so when did it all start? Did it have to evolve in one generation of a species? Or what? My biology teacher said that no-one really has an answer for this. Also, if natural selection or whatever found it necessary for two sexes to exist, will we be able to evolve a third or fourth sex? Please take this seriously, I'm not trying to attack evolution or anything, I'm just really interested in this. ► Adriaan90 ( Talk ♥ Contribs ) ♪♫ 14:33, 3 February 2007 (UTC)

Well, no one has a definite answer to this, though there is a lot of speculation going back even before Darwin's work. You might check out our article on evolution of sex for quite a lot of discussion of it. Once you've evolved sexual reproduction of this sort, the specialization of the different sexes to different functions, appearances, etc. is, I think, a comparatively easy thing to understand. --24.147.86.187 14:45, 3 February 2007 (UTC)
Sex#Animal species shows that there are several animals with more than two sexes. − Twas Now ( talk • contribs • e-mail ) 23:41, 3 February 2007 (UTC)
Yeast is a "primitive life form," and it has a sexual form of reproduction, too. In fact, bacterial conjugation is kind of like sex. -- Scientizzle 01:26, 4 February 2007 (UTC)

[edit] Land fill solution or not...?

After watching the movie Soylent green and reading the article on Digestion I was wondering if it would be possible (and practical) to process solid waste both mechanically and chemically in a similar fashion as digestion or using the steps in Quantitative analysis or Qualitative analysis to produce a resource for useful byproducts such as plastics or for other purposes such as eliminations of Toxins or Pathogens? 71.100.10.48 15:23, 3 February 2007 (UTC)

Yes, indeed - I assume you mean household waste..
There are methods similar to digestion for treating household waste, see Waste_management#Waste_management_techniques subsection Composting and anaerobic digestion, also for sorting the waste see subsection Mechanical biological treatment - just as food is broken down in the gut by enzymes (an sometimes bacteria) - in the treatment of biodegestible household waste bacteria and enzymes break down some waste producing 'soup' that may be suitable for fertilizer, and possibly gas (methane). Any organic matter might be suitable for this - includes waste food obviously, but also wood, paper, some plastics, non synthetic clothes - it all depends on how good the bacteria are..
As for a similar process to the steps in Quantitative analysis or Qualitative analysis - I assume you mean as in chemical analysis, and again the answer is a resounding yes.
See subsection Pyrolysis & gasification in Waste_management#Waste_management_techniques - in this case waste is heated to a very high temp (eg much greater than 200 degrees C - maybe much greater than 1000C depending on method), but air (oxygen) is excluded so it doesn't burn - this causes all organic matter including synthetic plastics to break down (see also cracking (chemistry)) - the process typically yields a great mixture of products - that can be separated by distillation. It's comparable to the process where chemicals used to be obtained by heating coal (eg Karrick process or similar).

We have excellent articles on this see pyrolisis and gasification - both are great routes to synthetic 'diesel' and other petroleum replacement products - it's a form of recylcing of organic matter.87.102.9.55 16:20, 3 February 2007 (UTC)

If you want to read more I can suggest

Gasification#Gasification_process_examples and all the article pyrolysis - similar to chemical analytic methods.

For methods similar to digestion see Anaerobic digestion

If you look at the page on waste_management you may find other useful links.87.102.9.55 16:26, 3 February 2007 (UTC)

As for getting rid of toxins and pathogens - there is some infomation in the articles - the answer seems to be yes in some cases - specifically biological toxins.87.102.9.55 16:31, 3 February 2007 (UTC)

[edit] This is not a joke and is not me trying to be sarcastic

This is not a joke so please answer seriously. Is it possible to kill someone by throwing (using their arms) an almond or a soybean at high enough velocity or by hitting a vulnerable part of the head. If you have heard any anecdotes of this please respond. Thanks. Again, this is not a joke, as ridiculous as it may sound. 63.135.8.94 15:42, 3 February 2007 (UTC)

No. A human arm can't give those objects enough kinetic energy to do any lethal damage on their own. But, I guess the person could choke and die of asphyxiation if it happened to go down their throats... — Kieff | Talk 15:46, 3 February 2007 (UTC)

Even if the KE of the almond cannot exceed whatever amount of joules, is it not entirely impossible that it may hit a certain area of the head, such as a vein or artery or a nerve and cause death or serious injury? Thanks again for your previous reply63.135.8.94 15:54, 3 February 2007 (UTC)

Sure it is possible, but then any small, light object could also be considered lethal in these conditions. — Kieff | Talk 16:15, 3 February 2007 (UTC)
Even with the assistance of a sling or slingshot, you need a projectile of at least 50 grammes to do any damage - many times heavier than an almond or soybean. The part of the body most vulnerable to injury by a small hand-thrown projectile is probably the eye. But I really don't see how it could be lethal (apart from the choking danger that Kieff mentioned). Gandalf61 16:29, 3 February 2007 (UTC)

There are no parts of the head and neck that vulnerable to a small hand-thrown projectile in a healthy person If you want to make the person unusual, or if you want to add some more conditions, you can concoct all kinds of semi-plausible scenarios. The person has heart disease, gets angry, and dies of a heart attack. The person is standing on the edge of a crowded train platform as the train is approaching, and the thrown object startles him and causes him to fall in front of the train. The person is so depressed that this one additional unexpected expression of contempt and anger from a previous friend causes him to decide life is too painful. And so forth... alteripse 16:35, 3 February 2007 (UTC)

It would be very, very difficult to kill (or even injure) someone with an almond or soybean. (Apart from Alteripse's "cooked" solutions, that is.) Theoretically, you can give even a lightweight projectile a lethal amount of momentum by shooting it fast enough. In practice, however, there are two crippling difficulties: (1) neither an almond nor a soybean is particularly aerodynamic -- they'd lose velocity rapidly between your gun and the target; and (2) neither an almond nor a soybean is particularly rigid, so it would be nearly impossible to accelerate them up to the stupefyingly high necessary velocity without disintegrating them. —Steve Summit (talk) 18:35, 3 February 2007 (UTC)
If you think we don't take silly things seriously, check out Wikipedia:Reference desk/Archives/Science/2007 January 26 & 27#My other planet is made of meat. In high school, a guy I knew had a pencil thrown at him that lodged into his temple, and just stuck there. He was OK, and I think he didn't even notice until someone pointed it out. − Twas Now ( talk • contribs • e-mail ) 23:39, 3 February 2007 (UTC)
I saw someone's eyeglasses broken by a thrown pingpong ball. An almond should have an easier time breaking the glass lens, and the broken glass could penetrate the eyeball leading to lethal infections. (Sure it's funny, until someone looses an eye) Edison 00:02, 4 February 2007 (UTC)

[edit] Total Cholesteral Reduction

I am a 61 year old male. My TC was measured twice at a six month interval. It was 234 each time. The doctor reccommended exercise and diet to reduce the TC. I've engaged in 20 minutes per day of aerobic exercize and reduced my intake of cholesterol to less than 100 mg/day. I've also increased my intake of soluable fiber to more than 4 gm/day. I've followed a diet aimed at weight reduction and have lost 14 lbs in the last 33 days putting me at 192 lbs. What level of reduction in TC can I reasonably expect to achieve following this regimen? From a minimum to maximum?Brucearugg 17:56, 3 February 2007 (UTC)

Because your cholesterol levels are going to be based on the interplay of a number of factors – environmental ones related to the changes you've made in your behaviour as well as luck-of-the-draw genetics – and because you've made so many (healthy!) changes to your lifestyle, any answer we give you here would be no better than a wild guess.
Moreover, total blood cholesterol is only one indicator of health. More important are the levels (absolute and relative) of HDL (so-called "good cholesterol") versus LDL ("bad cholesterol").
In any case, you're best off just asking your doctor or cardiologist what changes or benefits are likely to accrue from the specific changes you've made to your own, unique lifestyle. TenOfAllTrades(talk) 18:22, 3 February 2007 (UTC)
I don't know the answer to your question, but let me just say: kudos on the positive changes you've made! Keep with it! —Steve Summit (talk) 18:29, 3 February 2007 (UTC)

[edit] Do rats have spleens?

?

Don't you ? We're all mammals, ain't us ? -- DLL .. T 18:52, 3 February 2007 (UTC)

I read that rats don't have bladders, so there might be other differences too. --84.69.30.24 19:26, 3 February 2007 (UTC)
Rats have bladders. Chickenflicker---♣ 19:28, 3 February 2007 (UTC)
There's a diagram and a discussion of rat dissection here: [2]. Rats do indeed have bladders, as well: [3]. TenOfAllTrades(talk) 19:31, 3 February 2007 (UTC)
Sorry. I've clearly been misinformed. It was an article in the newspaper about ratcatching where it was stated by a ratcatching expert that rats do not have bladders and hence constantly dribble piss behind them wherever they go to mark a trail for other rats to follow. --84.69.30.24 19:36, 3 February 2007 (UTC)
Rats don't have gallbladders. Maybe that is the source of confusion. --Joelmills 19:39, 3 February 2007 (UTC)
....and ratcatchers have a wicked sense of humour. (At least, they're usually portrayed that way.)--Shantavira 09:12, 4 February 2007 (UTC)

[edit] Question about pets and domestication

What's the difference between a tame pet and a domesticated pet? This comes up a lot on the birdkeeper forums and people actually have big arguments about it. Why would a cat be considered a 'domestic' pet while a cockatoo (for example) would be referred to by avian science people as a 'tame' pet? Is a budgie 'tame' or 'domesticated'? --84.69.30.24 19:25, 3 February 2007 (UTC)

If you take a look at the article on domestication, it says that budgies are considered domesticated. "These species or varieties are bred and raised under human control for many generations and are substantially altered as a group in appearance or behaviour." As for cockatoos, the same article would probably put them in the category of "raised commercially" or "semidomesticated" rather than fully domesticated. Chickenflicker---♣ 19:47, 3 February 2007 (UTC)

[edit] How should you heat up an embryo?

I have a curiosity about how can embryos be defrosted from the fridge prior to being implanted to avoid that the water present expands thus damaging it. Can you heat it rapidly without burning the specimen?20:09, 3 February 2007 (UTC)

I'd just let it warm up slowly, or in luke warm water - I think your question/my question should be "how can an embryo be frozen without causing frost damage from the ice crystals that will inevitably form" - the same goes for sperm.213.249.232.136 20:12, 3 February 2007 (UTC)
Our article on cryopreservation gives a good overview of the challenges associated with freezing (and thawing) viable tissue and cells. Cryoprotectants are chemicals which are added to cells at the time they are frozen; these chemicals typically discourage the formation of ice crystals which would otherwise puncture and kill cells.
Thawing most frozen tissue or cells is actually a very straightforward process. There are two key goals in thawing. First, one wants to warm the tissue fairly rapidly through the temperature range where ice crystals are most likely to form; this runs from roughly -50°C to -15°C, give or take. Second, you want to wash off or dilute out the cryoprotectant. (Prolonged exposure to cryoprotectants will kill a warm cell.)
Accomplishing these goals is generally straightforward. Frozen specimens are normally in glass or plastic tubes or vials. They can be warmed rapidly by immersion in a body-temperature (37°C) water bath; this thawed solution can then be diluted to reduce the concentration of cryoprotected to below toxic levels. For thawing small volumes, rapid warming and dilution can be accomplished by directly adding warm liquid to the frozen-solid sample. TenOfAllTrades(talk) 21:27, 3 February 2007 (UTC)
DMSO is commonly used for cryopreservation of cell lines...but I'm not sure if it's used for embryos... -- Scientizzle 07:28, 4 February 2007 (UTC)

[edit] Scarlet Fever

I am doing a report in science on an infectious diseases caused by bacteria. I picked scarlet fever. Please tell me all that you can!!!!!!!!!22:44, 3 February 2007 (UTC)

Have a look at scarlet fever and Streptococcus pyogenes, the latter being the species of bacteria that causes the disease. --David Iberri (talk) 22:46, 3 February 2007 (UTC)

[edit] Is FM radio lossless? If not, what bitrate is it at?

Hello, my question is concerning the audio quality of FM radio. Does the transmission of the sound through the air bring the quality down? Do radio stations load up lossy files on their playlists, like 128 kb/s mp3 files? Basically, what bitrate would be comparable to the quality of FM radio on the receiving end/through my stereo? Thanks! NIRVANA2764 23:11, 3 February 2007 (UTC)

Its complicated to say, as it will depend upon the audio codec imployed, in the UK DAB broadcasts at 160 kb/s IIRC, via a form of MP2 encoding, with the speech only networks at a lower 128 kb/s and Radio 3 (classical music) at 192 kb/s. It is suggested that 192 kpbs is needed to give high quality audio broadcasts.
For more info checkout the Digital Audio Broadcasting page, more specificaly this section.
There are other issues of course - often audio will sound different between a CD, radio and television broadcast, and if you are used to a particular version of a song then even though the other is at a higher rate of transmission it may still sound worse! --Neo 23:31, 3 February 2007 (UTC)
Er... Traditional FM radio uses a purely analog modulation method (ignoring some of the sub band extensions). You can't talk about it in terms of "bit rate" (as you could with digital modulation schemes like PSK and OFDM). Your usage of "lossless" seems to be in the sense of digital audio compression methods, which is simply irrelevant here. The article on frequency modulation proper provides some insights on maximum bandwidth, drift, SNR, etc. -- mattb @ 2007-02-04T03:30Z


FM Radio has a Signal to Noise ratio and is not digital. 1 bit corresponds to roughly 6 db (6 db is double signal level, 1 bit in base 2 is double). Original CD quality is 16 bits which corresponds to about 96db of S/N. Bit rate corresponds to the frequency range. IIRC, CD's are about 24KHz of range which for Nyquist is 48 KHz. So a CD plays 16 bits at 48 KHz => 768 kb/s. You can trade frequency or S/N to reduce this number and compression does it smarter than just the baseline cut.
FM as implemented has a frequency range to 15 kHz (30 KHz Nyquist) and I believe the noise floor give about 60dB of dynamic range (~10 bits). Note that this is best case in FM and in practice is worse than this. That's 30*10 or 300 Kbps for Nyquist sampling to Digitally recreate the best possible fidelity of FM analog. --Tbeatty 07:02, 4 February 2007 (UTC)
A fair point - but FM is analogue - therefor the resolution (eg CD resolution is 16bit) could be considered infinite..(not quite true)
Resolution, whether it's digital or analog, is expressed as signal-to-noise ratio. Quantization error (the error between "infinite" analog and discrete digital) can be expressed as noise. In fact, moving the quantization error out of the baseband frequency is how 1-bit, oversampling works. It is entirely accurate to compare digital resolutions with S/N and analog with S/N. There is no additional resolution because of the continuous nature of the analog signal. That portion of continuity that distinguishes iteself from the digital portion is unrealizable signal that is lost in the noise. Analog FM is not infinite resolution because there is a finite noise floor that limits it. Currently that noise floor is 60 dB and that is an equivalent noise floor to 10 bits. You have to think in the frequency domain (for both anaolog and digital) to understand the mathematics that proves this. Fourier Transforms and the Discrete Fourier Transform/Fast Fourier Transform is the mathematics required for the analogue and digital respectively. --Tbeatty 19:22, 4 February 2007 (UTC)
FM quality depends critically on reception conditions as it is an analogue signal - in general a good signal strength of FM radio would produce audio quality comparable to analogue records or cd's - but not quite as good - better than cassette tape though.
The weaker the signal the poorer the sound so yes - transmission affects quality.
I'd guess that FM radio stations don't usually transmit MP3 files - most likely they use CD's or another digital source such as DAT. However audio level compression is common on FM - resulting in a percieved loss of quality.
I wondered if you were thinking about DAB - digital radio - apparently a FM gives a comparable quality of sound as 192kbit/s digital radio as a best case - in reality it's probably a lot less.87.102.7.169 10:23, 4 February 2007 (UTC)

[edit] Cold fusion? real?

How come wikipedia's article on Cold Fusion is written from the POV that Cold Fusion is real? Isn't it odd for an article to be writtin from such an obscure perspective?--71.249.19.4 23:43, 3 February 2007 (UTC)

Could you quote an example of this alleged bias? I looked it over just now and it seems fine, but of course I could have missed something. Anyway, the reference desk is not for questions about Wikipedia. Next time bring it up on the talk page. —Keenan Pepper 00:39, 4 February 2007 (UTC)
Actually, the Reference Desk can be for questions about Wikipedia. One of the Reference Desk's primary purposes is to help the project, and one way it does this is by assisting editors in their research. (There's a fine example just below.) —Steve Summit (talk) 01:05, 4 February 2007 (UTC)
IMO, it does seem to be a bit biased towards cold fusion, but nothing blatant enough for a non-expert to object to. It would take someone really knowledgeable in the field to do that. Clarityfiend 03:16, 4 February 2007 (UTC)
The original cold fusion claims reportedly lacked the emission of neutrons sufficient for the energy claimed. As I recall, the energy production was chalked up to normal electrochemical processes and inadequate process control. Reading this article, I get more of an impression of there being fusion than the earlier analyses implied. I believe there have ben recent reputable claims of cold fusion, but in processes which could never be energy sources, but still useful as neutron sources. Any nuclear engineers out there? Edison 05:14, 4 February 2007 (UTC)
I too agree that there is no noticable bias - to a non expert - and in terms of the info. in the article. It is possible that information/papers against cold fusion occuring are underepresented and evidence for is over represented... But in terms of the writing style I can see no bias.

87.102.35.119 12:57, 4 February 2007 (UTC)

The perceived "bias" may be that the article does not come out and say "Cold fusion is wrong! R O N G wrong! Fleischmann and Pons were charlatans and frauds! It was all a hoax!" But of course, that would be just as badly POV, in the other direction. —Steve Summit (talk) 13:40, 4 February 2007 (UTC)
Now, now. Cool down; don't go nuclear on us. Clarityfiend 17:19, 4 February 2007 (UTC)