Wikipedia:Reference desk/Archives/Science/2008 December 10

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December 10

Tea and diabetics

I was in my local tea market and they had a sign warning of the dangers of drinking tea if you are a diabetic. It warned that it can increase blood sugars. I've never heard of such a thing. Obviously, if you take your tea with sugar, that's a problem. But unsweetened plain tea? Is there any truth to this? --69.149.213.144 (talk) 04:15, 10 December 2008 (UTC)

According to this article, which appears to quote a reliable source, rat studies suggest that tea may be of benefit to people with diabetes. [1]. DuncanHill (talk) 04:32, 10 December 2008 (UTC)

Here is a reference according to which "Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects". Otolemur crassicaudatus (talk) 11:22, 10 December 2008 (UTC)

Tea does not worsen blood sugar. Axl ¤ [Talk] 18:29, 10 December 2008 (UTC)

Unless, of course, you add sugar to your tea... – ClockworkSoul 19:06, 10 December 2008 (UTC)

Caffeine is a diuretic. This means that it makes you pee. Depending on the type of tea, it can make you pee, which reduces your water proportion (and I mean the percent of water you are composed of). This, inturn, will increase your blood (glucose) sugar level, because the water that is excreted in the urine will be immediately from the blood. (urinary system for more). Then nephrons of the kidneys take the toxins from the blood and in urinary tubes (it's been a while since i last did biology) funnels it to the bladder for excretory storage. Mind you, water is the solvent in the medium of these toxins. So tea may increase blood glucose levels in this way.96.53.149.117 (talk) 07:58, 11 December 2008 (UTC)

Interesting. But this market also sold coffee and there was no warning sign about coffee and diabetics. --70.167.58.6 (talk) 16:12, 11 December 2008 (UTC)

If it were a tea market, I'm guessing there would be a lot of fancy teas some of which may contain sugars natural or otherwise. This may be directed at those. Even more so if you're a Brit in which case you may be thinking of several cupsof tea within a few short hours Nil Einne (talk)

Caffeine is indeed a mild diuretic. There is some evidence that a large quantity of caffeine intake can impair glucose control. However the caffeine load is equivalent to over a litre of tea drunk, with 75 grams of sugar at the same time. Axl ¤ [Talk] 11:30, 12 December 2008 (UTC)

Fleeting bad memories

Sometimes out of the blue I suddenly remember a bad memory and makes me feel bad. My knee-jerk reaction would bedoing an intellectual na! nanana! I can't hear you! by focusing on something else (tapping my fingers for example) until it goes away. What do you call that resurgence of memory and my suppression of it.--Lenticel ^(talk) 04:45, 10 December 2008 (UTC)

There's a wiki article Flashback (psychological phenomenon) which is too stubby to be of great help, but it's a start. Suppression of it, repression, is a defense mechanism. Julia Rossi (talk) 05:04, 10 December 2008 (UTC)

Take also a look at Rumination_(mental). --Mr.K. (talk) 09:51, 10 December 2008 (UTC)

The finger tapping block is mechanical, not the same thing as a subconscious repression. Try Thought suppression for the deliberate conscious one. Julia Rossi (talk) 22:34, 10 December 2008 (UTC)

I find swearing at the people who caused the bad memories to be beneficial. Of course, only do this out loud when you're alone, or you'll have to tell everyone you have Tourette's Syndrome. StuRat (talk) 04:48, 11 December 2008 (UTC)

Jets flying over populated areas

Do fighter aircrafts have to fly over populated areas? Civil aircrafts probably have to, but why do military jets do it?--Mr.K. (talk) 09:37, 10 December 2008 (UTC)

If a military aircraft flies over populated area, that does not mean it will use its weapons system. It becomes quite tough and the route becomes quite complex if it avoids civilian areas. If there is short air route available by flying over a civilian area, the fighter may take that route. Otolemur crassicaudatus (talk) 10:41, 10 December 2008 (UTC)

I would assume the question is motivated by the F/A-18 that crashed into a house in San Diego recently, and not by concerns over weapons systems. In this case the fighter was on approach to Miramar which is surrounded on three sides by populated areas. Dragons flight (talk) 11:07, 10 December 2008 (UTC)

It is not uncommon for military bases to be surrounded by populated areas. It is not reasonable to ask the fighter jets so somehow create a wormhole through space and teleport from outside the populated area to the military base without flying over all the homes that were built around the base - usually long after the base was built. -- kainaw™ 13:38, 10 December 2008 (UTC)

It's very unusual for fighter jets to land on houses, so it doesn't make sense to give the issue much attention in their routing. You'll probably save more lives by having the houses near the base, which will reduce the number of person-miles the base workers will drive on their daily commute. --Sean 13:42, 10 December 2008 (UTC)

Why should military aircraft be held to any standard other than civilian ones, given the latter are larger, not designed as ruggedly vs things that could happen in the air (747 doing a barrel roll and getting hit during a dog-fight?), and are owned by companies deep in bankruptcy vs the cash cow that some claim US military spending is. DMacks (talk) 14:02, 10 December 2008 (UTC)

"Why should military aircraft be held to any standard other than civilian ones..."

There are dozens of reasons:

• Different aircraft design, including size, speed, type of fuel, maneuvering capability
• Different flight capabilities
• Different engines (louder, noise-complaints over populated areas)
• Different training methods and selection criteria for pilots
• Different aircraft manufacturing (materials, hazardous components)
• Different safety regulations regarding pilot state (hours of sleep, for example)
• Different ground support crew (maintenance, air traffic control, personnel supervision)
• Psychological impact due to the presence of an ejection seat on a pilot in an emergency over a populated area
• Potential to carry weapons systems
• Overall different philosophy regarding the role and operation of military vs. civilian aircraft

The result is that there is a different standard, implemented in the form of air space - there is restricted military-only airspace; there is restricted civil-only airspace, and shared airspace. The F-18 that crashed this week had already declared an engine malfunction while over the ocean, and was being routed to Miramar (instead of the aircraft carrier where it was based), because it was probably thought safer to fly overland than over water [2] - "Several experienced pilots said that if there's a nearby landing field ashore, an inexperienced pilot wouldn't attempt a dangerous, engine-out landing on the pitching deck of an aircraft carrier." Pending the full investigation, it is not clear why the pilot ditched the aircraft, but assuming his judgement was sound, a serious equipment failure may have rendered it uncontrollable. Alternatively, the pilot may have misjudged or panicked. Nimur (talk) 16:36, 10 December 2008 (UTC)

Thanks for the knowledgeable reply! I might add in reply to the question "Why should military aircraft be held to any standard other than civilian ones...", that they are already held to much lower standards. To be exact, 750 feet lower. At least that was the case in Germany, where US jets (mostly Phantoms) crashed on civilian houses on a regular basis when I lived there - they were allowed to fly at 250 feet at supersonic speed, according to de:Tiefflieger (for which there seems to be no translation. Can it be that they only did that in Germany?) I can tell you - it all fun and games when they fly slowly over you on Fourth of July, but it's brute force when they blast over your head every other day at random times. — Sebastian 18:07, 10 December 2008 (UTC)

Tieflieger trained not only in Germany, but they were a particular problem there for a number of reasons. First, Germany is simply small and full. There are few areas without significant population, particularly not for an aircraft at Mach 1 or above. Secondly, Germany was seen as a likely battlefield in the Cold War. Hence, for realistic training, Germany was preferred. And thirdly, as a result of the WW2 capitulation, the allies got fairly far-reaching military cooperation agreements that allowed them to use German airspace for training purposes without alienating their own voters. --Stephan Schulz (talk) 19:28, 10 December 2008 (UTC)

Can you define "regular basis"? Was it daily? Who's house is going get destroyed today? Was it weekly? Was it monthly? Was it yearly? Did it happen 3 times over 20 years? It is difficult to relate this singularity in the U.S. with Germany without something better than "regular basis". -- kainaw™ 18:13, 10 December 2008 (UTC)

Ah, found it: de:Starfighter-Affäre. The plane was the Lockheed F-104G, a.k.a. "Starfighter". There were hundreds of crashes. According to the German article, alone in 1965, there were 27 accidents with 17 casualties. And as I remember, this dragged on for years. — Sebastian 18:24, 10 December 2008 (UTC)

Looking at our own article Lockheed F-104, which says "flying at high speed and low level over hilly terrain, a great many accidents were attributed to CFIT or Controlled Flight Into Terrain ...", I learned a wonderful doublespeak way to say "crash"! — Sebastian 19:33, 10 December 2008 (UTC)

"Controlled flight into terrain" isn't doublespeak, it's a term of art describing a specific type of crash. Other types of crash include runway overruns, mid-air collisions, and structural failure. --Carnildo (talk) 22:34, 10 December 2008 (UTC)

But of course! It's a "controlled flight into building", as in "Controlled demolition hypothesis for the collapse of the World Trade Center". ;-) — Sebastian 23:18, 10 December 2008 (UTC)

I see, I wasn't aware of that term. But it's still strange, and it doesn't seem to be common in aviation, at least not here at Wikipedia. Even our article Aviation accidents and incidents only mentions Controlled Impact Demonstration, which uses the term in the way most people would: "Controlled" meaning "keeping things under control". — Sebastian 00:16, 11 December 2008 (UTC)

I used to work in flight simulation - it's a common enough aviation term with a very precise meaning. It means that the plane didn't hit the mountain because it was damaged or because the pilot had blacked out...the aircraft was perfectly flyable - and the pilot was fully in command of the controls - but the plane smacked into a mountain anyway. Hence it means things like flying into a mountain because of reduced visibility - or some kind of nighttime navigational error - or because the altimeter was mis-calibrated...something like that. SteveBaker (talk) 06:21, 11 December 2008 (UTC)

And I should point out that I, despite having never heard the term before nor any experience in the airline industry was able to guess more or less what it meant Nil Einne (talk) 12:20, 11 December 2008 (UTC)

My point was for User:SebastianHelm's sake, he said "I learned a wonderful doublespeak way to say "crash"!" - but it's not doublespeak (it's not a euphemism) and it doesn't mean "crash" - it means a very specific kind of crash. At any rate - no mention of the Starfighter would be complete without the saying that was prevelant in the USAF at the time: "If you want to buy a Starfighter - get a piece of land in Germany and wait!". SteveBaker (talk) 18:07, 11 December 2008 (UTC)

(undent) Out of curiosity, how unstable was the F-104? Modern fighters are designed with relaxed or absent static stability for maneuverability or other reasons with the plane kept under control by computer correction. Stealth was a future concept, but was there intentional instability in the F-104 design for maneuverability? For that matter, is an F/A-18D particularly stable? SDY (talk) 18:43, 11 December 2008 (UTC)

The Starfighter was bought because the producer bribed several politicians in europe to buy it, so they bougth the bird which was a good weather high speed high altitude intercepeter and used it for what it was needed in europe an allweather allround fighterbomber. The bad training and the design which was not for turbulent valleys and small hills made it the a dangerous witwenmacher widdowmaker.--Stone (talk) 20:45, 11 December 2008 (UTC)

The problem is that you really NEED instability in a fighter - a super-stable plane is resistant to change in attitude - so it can't manouver as effectively. Consider an airliner or a typical light aircraft - it has wings that are in a slight V configuration (it's called 'dihedral') - this is a clever stability thing - if your plane starts to roll to one side, the wing that's going downwards becomes more horizontal while the one that's going up becomes less horizontal. That causes the lift of the down-going wing to increase while the lift on the upgoing wing decreases...this causes a rotational force that acts to make the aircraft want to level out again. So as a pilot, you can be fairly relaxed because the plane tends to 'fly itself'. But if you WANT to turn rapidly, that stabilising effect makes it harder to turn. Hence fighters typically have wings without dihedral...or perhaps the have wings that droop downwards ("anhedral") which has the opposite effect...when the plane starts to roll - the upgoing wing now gains lift and the downgoing one loses lift - so the plane tries to roll even more...this makes the plane MUCH harder to fly - but gains manouverability. The Starfighter has all sorts of these kinds of feature - designed to make it INTENTIONALLY unstable - because instability creates manouverabilty. More modern fighters are designed to be crazily unstable - and most of them would be impossible for a human to fly. Fortunately, we have computers to help out - the computer can fly the plane so well that even though it's unstable, it doesn't FEEL unstable to the pilot. The trouble with the Starfighter is that it comes in that period of time when instability was thought to be good - but the computers needed to tame that instability didn't exist. SteveBaker (talk) 04:33, 14 December 2008 (UTC)

Reducing fat

There are a myriad of products on the market that promise to reduce the fat in your body. In a series of them, the effect is from outside the body (heat waves, cream, vibrations, small electro-shocks). Excluding surgery, is there any possibility to reduce fat through this way or fat can only be reduced from inside?--Mr.K. (talk) 09:47, 10 December 2008 (UTC)

Dieting may help. Physical exercise is the best option to reduce fat. It depends on the amount of body fat a person has. There are anti-obesity drugs also available. In extreme cases where the person is too overweighted, surgery is generally required. Otolemur crassicaudatus (talk) 10:47, 10 December 2008 (UTC)

The question is actually about ways of reducing fat with an external procedure (not diet, exercise, ...) and excluding surgery. Is it possible?Mr.K. (talk) 11:08, 10 December 2008 (UTC)

Well exercise is arguably an "external procedure", and likely to be effective. In principle, electrical muscle stimulators should be capable of improving muscle strength and tone in a way that is similar to (but probably inferior to) that of exercise. That would probably have an indirect effect on fat. I have also seen some studies (in rats) supporting the notion that vibration reduces fat deposition, though that is not the same as removing existing fat deposits. The best thing for reducing fat though is almost certainly dieting. Dragons flight (talk) 11:17, 10 December 2008 (UTC)

In the case of exercise, our body burns the fat to obtain energy, definitely a natural process of our body. --83.40.248.171 (talk) 11:39, 10 December 2008 (UTC)

Clockwork Toy (Homemade)

I'd like to make a gear-based toy, but I don't know a good source for cheap gears and such. Any suggestions? Preferably plastic. Black Carrot (talk) 10:56, 10 December 2008 (UTC)

McMaster-Carr has all sorts of those kinds of bits and bobs. --Sean 13:48, 10 December 2008 (UTC)

Lego Technic? SteveBaker (talk) 21:19, 10 December 2008 (UTC)

You may also consider the Meccano toy sets, which (if childhood memory serves me) had all sorts of cogwheels and related bits for technical models. --Cookatoo.ergo.ZooM (talk) 20:28, 11 December 2008 (UTC)

LPG

At what temp. does LPG turn to vapor for use on a furnace in a camper?```` —Preceding unsigned comment added by Raytrudell (talk • contribs) 13:34, 10 December 2008 (UTC)

Assuming good faith that it is not a homework question, the answer to your question is -42°C. Otolemur crassicaudatus (talk) 13:50, 10 December 2008 (UTC)

This temperature is appropriate for propane, however in case of LPG it may vary from -44 ºC to 0 ºC. Otolemur crassicaudatus (talk) 14:01, 10 December 2008 (UTC)

Doesn't pressure have something to do with it? —Preceding unsigned comment added by 98.17.46.132 (talk) 14:03, 10 December 2008 (UTC)

Yes, it is in "normal" atmospheric pressure. Otolemur crassicaudatus (talk) 14:20, 10 December 2008 (UTC)

LPG in a cylinder is at a higher pressure than atmospheric. When an appliance connected to the cylinder is turned on, the pressure in the cylinder is reduced somewhat and the liquid boils, thereby releasing gas. It will always boil, regardless of the temperature of the LPG liquid, unless the ambient temperature makes the temperature of the liquid LPG in the cylinder extremely low. LPG is mainly butane; in winter months, LPG suppliers mix some of the more expensive propane with it to ensure it will boil. —Preceding unsigned comment added by 98.17.46.132 (talk) 15:00, 10 December 2008 (UTC)

Yes it will boil in any temperature above 0 ºC which we see in our every day life, but it needs the minimum temperature -44 ºC in "normal" atmospheric pressure to boil. Otolemur crassicaudatus (talk) 15:16, 10 December 2008 (UTC)

"LPG" and "vapor pressure" in Wikepedia have information on this.

Test your microwave with a mobile phone?

On a recent episode of the Gadget Show it was claimed that you can test the shielding on your microwave oven by checking whether a mobile phone will receive a call when inside the oven [3]. I have tried this on two microwaves so far, and in both cases the phone could receive the calls. I have also read elsewhere that the shielding should not stop mobile phone calls because the frequency differs too much from those used by the microwave. Can anybody clarify this please? Larry Mystery (talk) 15:21, 10 December 2008 (UTC)

The question you are asking is, roughly restated, "does the microwave have a shield?" It should be more properly restated, to be very precise, as "What is the non-linear anisotropic attenuation-vs-frequency characteristic of the microwave casing, and what frequencies of attenuation overlap those frequencies used by the cellular phone?" First of all, let's clarify a few details:

• Microwaves and cell phones commonly do operate at the same or similar frequency band (for example, 2.45 GHz). But, maybe your microwave and cell phone operate at different frequencies... it depends on whether your phone uses GSM, where you bought your microwave, etc. You can check this with the marshmallow test, or if you're smart, just read the label on the back of the microwave oven.
• Microwaves commonly include a few features, such as a wave guide or horn to guide the microwave energy in a specific direction (towards the food)
• After the microwave energy is "in the oven", it bounces around, off the walls, maybe even setting up resonant waves. So, any "shielding" should really be surrounding the entire oven, with strongest protection at the places of strongest electromagnetic fields (typically, directly opposite the "horn" where the waves come in.
• Microwave ovens probably use a "crappy" but generally single-frequency tonal magnetron to create the electromagnetic waves. So, the shielding is quite probably a "notch filter" (isolating out that single frequency and preventing it from passing).
• By the second law of thermodynamics, any (passive) shielding should be bidirectional - that is, if the energy can't get out, then energy can't get in, either.
• Shielding is also not measured as "all or nothing" - it's measured as an attenuation. That means that the shield lowers the intensity of the radiation, but does not make the signal disappear completely. Now comes the non-linear part. The case in consideration compares two very very very different orders of magnitude - nearly one kilowatt of oven radiation, blasting from eight inches away, compared to a few milliwatts transmitted by the phone and maybe nanowatts (picowatts even!) received from the tower. (Depending on "details," your phone may need bi-directional communication to initiate the reception of a call; or it may just need to receive a single incoming message from the tower). So it may not be safe to say that the shielding materials attenuate by a fixed amount over this entire range of power levels. It's possible that very-low intensity signals, like those from the phone, are not attenuated much at all; while high-power signals are brought down to safe intensities (and no further)
• Cell phones use very complicated modulation to make sure that the data can be deciphered even when the signal is very very weak. This is what advertisers often mean when they say "fewer dropped calls" (though they might also be talking about density of towers). Specifically, some of the QAM spread-spectrum coding schemes are particularly insensitive to single-frequency interferers. So if the So even if the microwave shielding is "pretty good" at notching out (stopping) that single frequency that the oven operates at, the cell phone data may be fairly undeterred.
• And the anisotropic part makes a huge difference! The cell-phone probably has a crummy antenna, which may mean it has a weird angular reception pattern. And, the microwave oven shielding is probably not uniform either (presumably concentrated on blocking regions of highest radiation while cooking!) So, if you rotate the phone, you may get dramatically different reception patterns. And this is totally assuming that there is no resonant coupling between the 2.4-GHz resonant chamber of the oven, and the 2.4-GHz dipole antenna inside the phone. Who knows what may happen to the reception pattern if that effect is non-negligible! In summary, the orientation of the phone with respect to the oven, and the orientation of the oven with respect to the nearest tower, will dramatically change the results. (see Radiation pattern for more graphical explanation).

So, it can actually be fairly complicated to say whether a given microwave will "shield" a given cell-phone from a call. Irrespective of the result of that test, it is not really a good way to determine whether the oven casing effectively blocks out the microwave energy used during cooking. Nimur (talk) 17:00, 10 December 2008 (UTC)

paper mache external fuel tank

I attended a lecture at the Naval War College by Dr. Paul Kennedy of Yale University where he stated that during the second World War, the British developed paper mache external fuel tanks for the P-51 Mustang. He showed a picture of two Brits unloading one such tank from a stack. At that time, the Americans were using aluminum external tanks and the Germans were picking them up off the ground after they were dropped in Belgium and then they (the Germans) would reuse the metal. The paper mache tanks, however, when hitting the ground would become unusable. I have not been able to find any reference to paper mache tanks on the internet or in published materials I have on planes of the second World War. East5426 (talk) 15:58, 10 December 2008 (UTC)

Mildly related: the Tom Clancy movie Clear and Present Danger featured a paper bomb/missile that was used to blow up a drug kingpin's house such that it could not be traced to the US source by the shell fragments. Or something like that. --Sean 16:52, 10 December 2008 (UTC)

I've looked around on google a bit, and mostly all I see are modeling sites selling tanks for use on static models and discussion board posts, none of which meet WP:RS. Definitely happened, but you may need a bricks and mortar and, ironically, paper library to find references. SDY (talk) 16:59, 10 December 2008 (UTC)

It's possible the professor was making a vague allusion towards early research in composite materials, which now make up an entire class of aerospace engineering materials research because of their light weights. I don't know that any such materials were in use in research labs, let alone combat, in World War II. Nimur (talk) 17:12, 10 December 2008 (UTC)

In early 1943, the Eighth Air Force was looking for ways to escort B-17's to Germany and back. The YB-40's were no match for the German fighters, and once the B-17's had dropped their bomb load, the YB-40's were too heavy to keep up with the lightened bombers. Ira C. Eaker began looking at adding drop tanks to P-47 fighters. The U.S. was then using 200 gallon paper tanks for ferry flights, but these were mostly useless for combat, they added a great deal of drag to the airframe, tended to leak if filled with fuel for more than a few hours, and could not be used at altitudes greater than 23,000 feet.

Eighth Air Force fighter command, with the help of British engineers, designed a 108 gallon metal tank suitable for combat operations that was tested in May of '43, but a steel shortage prevented production. The Brits would begin supplying a paper 108 gallon tank which they had developed for their own use in September of '43. The British 108 gallon tanks extended the P-47's combat range radius from 190 to 375 miles.

The U.S. began manufacturing a 200 gallon paper tank (which was only half-filled on the P-47) that became available 28 July (260 mile rangeradius), and an 85 gallon (photo) (referred to as 75 gallon tanks, but actually held 85) metal tank (340 miles). On 27 September '43 the eighth flew it's first escorted mission to a target inside Germany using a mixture of the 85 gallon metal tanks, as well as the British 108 gallon paper and metal tanks. Levine, A. J. (1992). The Strategic Bombing of Germany, 1940-1945.] pp. 90-1. OCLC 25131830

Still looking for paper tanks for the P-51.—eric 21:17, 10 December 2008 (UTC)

This is a longshot but the search might work better in some search environments using "papier mache" instead of "paper mache". CBHA (talk) 21:28, 10 December 2008 (UTC)

[4] [5] w/ photos of the 108 gal. paper tanks.—eric 21:55, 10 December 2008 (UTC)

Diamonds Part 2

A few days ago, I posted a question about Diamonds. For the original question and discussion above, see this link: Wikipedia:Reference desk/Science#Diamonds. A follow-up thought (and question) came to mind after reading the input from my original question. So, we now have "real" (natural) diamonds that one can purchase for, say, $1000. And we have the "same exact thing" (synthetic) that one can purchase for, say, $100. Much of the discussion centered on purchasing the cheaper synthetic diamond, because it is exactly the same thing as the more expensive natural diamond. The only real difference is purely psychological and is a product of emotion and of clever marketing. But, what about looking at this issue from another perspective? Let's say that I indeed want to buy the "real thing" (natural diamond). As a consumer ... when I purchase what I think is the $1000 "real thing" … how do I know that I am not, in fact, being swindled and getting the $100 synthetic one in its place? Thank you. (Joseph A. Spadaro (talk) 18:23, 10 December 2008 (UTC))

Via grading and certification services such as the Gemological Institute of America. — Lomn 18:40, 10 December 2008 (UTC)

A related issue is how one is able to know that a natural diamond is not a blood diamond. Although there are industry procedures in place to ensure that synthetic diamonds or blood diamonds are not misrepresented, as an end consumer, you ultimately have to rely on your trust in the vendor. Past that, the article section Diamond#Synthetics, simulants, and enhancements notes that "Today, trained gemologists can generally also distinguish between natural diamonds and synthetic diamonds." It also mentions several machines/methods to distinguish them (DiamondSure & DiamondView). Additionally, most synthetic diamond producers are upfront about the nature of their wares. Many even visibly (under a loupe) mark their gem-quality diamonds with logos or other such items which shows who produced them. I believe DeBeers has even started marking natural diamonds in a similar fashion, to show that they are "real" diamonds. Natural diamonds from Canada are routinely marked, e.g. with the "CanadaMark" service. High carat diamonds may be marked with a serial number, and registered with institutions like the Gemological Institute of America, which record their provenance. (Unfortunately, I can't seem to find an article about diamond marking.) -- 128.104.112.113 (talk) 19:15, 10 December 2008 (UTC)

Could crooks put counterfeit certification markings on diamonds? Even if a serial number on a natural diamond is registered, how would a person know which diamond is the natural one? A record of all sales and purchases of a natural diamond would have to be kept as well. —Preceding unsigned comment added by 98.17.46.132 (talk) 22:09, 10 December 2008 (UTC)

Artificial gem diamonds aren't identical to natural gem diamonds. If made without further intervention, a lab diamond is (scientifically) superior - there are no almost impurities and a much lower incidence of flaws. To compete in the gem market, the lab people have to add impurities (mostly metals) to allow them to control the colour and clarity of their product; in particular they produce lab gem diamonds in colours that occur infrequently in nature. For now (because they don't feel the need not to, and to avoid stirring up a war with DeBeers) they do so in a fashion that simulates a natural diamond to casual (and fairly close) inspection, but isn't intended to deliberately appear entirely natural. DeBeers has a number of technologies to distinguish any of these from the "real" thing (as 128.104.112.113 notes above, they sell equipment to dealers for this purpose). Some other synthetic gems (such as emeralds) are made with deliberate un-natural additions that assist detection. If the lab people really wanted to, I imagine they'd be able to "improve" the growing process to produce the adulterations and defects that the gemologists and their machines look for. I guess (were that to happen) a technological tit-for-tat would ensue for a while (much like CAPTCHA) but eventually the lab ones would be sufficiently imperfect as to be entirely indistinguishable. Diamond marking is (in part) a recognition of this inevitability (the blood diamond thing is also a factor). But it's not much of a solution - numbers can always be cloned, and many gem diamonds turn over in the market so infrequently (decades) that the cloning won't be detected. Even if it is, if ten people all have identical diamonds with the same number, whose is the real one? And if a major player (say Russia or China) decided to mass-produce indistinguishable lab gem diamonds and tag them as coming from a mine that they really only bother to run when the inspector comes, they can produce fully certified artificials. And a major production of such diamonds could lower the price of all diamonds (except the truly exceptional ones with a provenance) as to make chasing after suspected "fakes" uneconomic. The only thing stopping this all from happening is that it's not in the interest of the artificial makers to ruin the market they've just joined - they want to be competitive, but they don't want to end up making diamond so cheap that there's only a decent profit when you make it by the ton. So they have a gun to DeBeers head (once they don't want to use) and DeBeers have one back - they can dump their (reportedly huge) reserves onto the market which zaps the artificial guys profit margins and makes their venture capital dry up (it's a Phyrric victory, as it also ruins DeBeers market for years to come). This stalemate won't last forever, I think. All those new members of the Chinese and Indian middle classes have a taste for things that the western middle classes already enjoy. Sooner or later someone will decide he can make his fortune selling a nice 1 carat artificial to 100 million people, and the game's up. 87.114.128.88 (talk) 23:08, 10 December 2008 (UTC)

...which, incidentally, is (in the long term) an unalloyed good for the Human Race. Diamond, like gold, is amazing stuff, and it's a shame it's been wasted in gaudy frivolity. The same technological improvements that will lower the artificials' prices so that everyone in India can have one will (hopefully) improve the diamond makers' abilities to the point where they can make affordable diamond an engineering material. Diamonds as bearings and bushings and joints, diamond coatings to metal components, diamond elements in aircraft wings and car engines, maybe even diamond beams holding up a three-mile skyscraper. 87.114.128.88 (talk) 23:19, 10 December 2008 (UTC)

I agree. Debeers has had people paying insane prices for shiny baubles for too long now. It's time that diamonds were made available to everyone at reasonable prices. An interesting side-effect will be that diamonds, once no longer rare or expensive, will no longer be valued in jewelry. Other gems will take over that position, like pearls, at least until they can be exactly replicated in the lab. StuRat (talk) 04:21, 11 December 2008 (UTC)

It's possible for diamond to remain popular in jewellery even after you can pick up a one carat rock for a buck and a half. They make excellent stones for decorative purposes because they don't get damaged (diamond being spectacularly hard) - and they have this HUGE refractive index which is what makes them sparkle so alluringly. Perhaps the trend will merely be for jewellery sales to trend towards much bigger and more perfect stones while the price remains pretty much stable. It's hard to predict when human emotion is so tied up in what happens. SteveBaker (talk) 06:14, 11 December 2008 (UTC)

I fear that super-cheap diamonds would suffer a "bling" problem (with gaudy people festooned in them like some kind of insane pearly king) that diamonds would become gauche; I guess it's much the same as how wearing purple was once such an indicator of success and thus prestige, but with the advent of synthetic dyes anyone can wear purple so it has no cachet whatever anymore. 87.114.128.88 (talk) 13:30, 11 December 2008 (UTC)

Also remember that when first isolated, and for many decades afterwards, aluminium was fantasticly expensive. During most of the 18th and 19th centuries, it was more expensive than gold and was used decoratively and in jewlery! These markets definately fluctuate greatly depending on availibility and public perceptions... --Jayron32.talk.contribs 13:37, 11 December 2008 (UTC)

It would be amazing what we could do with tons of cheaply mass/produced diamonds. Construct buildings from it. Unbreakable windows. The possibilities are nearly endless.

An interesting note: I remember reading a science-fiction book from the end of the 19th century, where the Austro-Hungarian Empire develops some kind of highly advanced, completely bullet-proof armored suit for their soldiers, and goes to war with Russia. The russians have a huge numerical advantage, but they lose every battle because they cannot even harm their enemy. So a great (economical) sacrifice has to be made: they gather all the diamonds they can get hold of, and forge bullets for their rifles out of diamond, this being the only material which can penetrate that armor. --131.188.3.20 (talk) 14:00, 11 December 2008 (UTC)

Let's all not get collective hardons (excuse the pun) over the potential applications of diamonds. The high refractive index makes them unsuitible for windows, for example. Also, diamonds, being flamable, are not very well suited for high temperature applications; I wonder if a diamond bullet wouldn't just burn up in the cartridge at ignition! Diamonds do have quite important industrial and commercial applications, but they are not a miracle substance and there are practical limits to their use... --Jayron32.talk.contribs 14:16, 11 December 2008 (UTC)

Well it's more about a normal bullet with a diamond tip than a fully diamond one. I wonder if the Mythbusters will get the funding to play with it. Lat's say, trying to fill a ballistic dummy with 0.55 caliber completely diamond musket balls. --131.188.3.21 (talk) 16:00, 15 December 2008 (UTC)

Flammable?? Really??

That's a helluva factoid! So, got any pictures of flaming diamonds? --DaHorsesMouth (talk) 23:59, 11 December 2008 (UTC)

Diamonds are carbon, the same basic material as coal, and are equally flamable. Our article on Material properties of diamond notes that "they can burn in the presence of oxygen if heated over 800 °C (1500 °F)." This google search as well as this one show enough links that this is a real phenomenon. Several sites agree with the 800 deg C/ 1500 deg F roughly. It is enough of a concern that jewlers need to be careful when soldering jewlery with diamonds on them, see this page with instructions on the problem. --Jayron32.talk.contribs 05:47, 12 December 2008 (UTC)

Hardly indestructible

Despite the assertion that "diamonds are forever", they aren't particularly tough. While they are extremely hard, that makes them more likely to chip than softer materials, like steel, which can deform to absorb an impact. Consider that glass is also very hard, although not quite as hard as diamonds. So, is glass difficult to break ? Not at all. Why isn't every diamond chipped, then ? Because small, roughly spherical shapes aren't all that likely to be chipped. Most glass marbles survive without chips, even though they are quite a bit larger than the average diamond. StuRat (talk) 17:28, 12 December 2008 (UTC)

Graphite is actually more stable, which is highly ironic given that saying "a pencil is forever" is precisely contrary to the primary advantage of a pencil over a pen... SDY (talk) 17:32, 12 December 2008 (UTC)

Thanks to all for your input ... I really appreciate it. This discussion was very informative. (Joseph A. Spadaro (talk) 15:47, 13 December 2008 (UTC))

Travis Pastrana

I was reading about Travis Pastrana. During an athletic competition, he sustained an injury in which his spine was separated from his pelvis. While I was continuing to read about him, I was assuming that this injury would have left him paralyzed. Seemingly, it did not. Why / how could that be? Thanks. (Joseph A. Spadaro (talk) 19:43, 10 December 2008 (UTC))

By not damaging his spinal cord, or otherwise causing significant nerve damage. This is one reason why the common advice is not to move an accident victim: if the spine is damaged, moving the victim can indeed lead to spinal cord injuries and, potentially, to paralysis. 198.29.191.149 (talk) 20:11, 10 December 2008 (UTC)

In an adult human, the spinal cord only extends about 2/3 of the way down the back. Below that point, there are several nerves that travel the remaining distance through the vertebral column and exit at various lumbar and sacral segments. Without knowing much about the injury you describe, I would assume that a separation between L5 and S1, while painful and probably dangerous, could plausibly fail to sever any of the sacral nerves that exit from the sacral region. He may well have suffered some stretch-induced injury (similar to a brachial plexus injury) that might include temporary numbness or weakness of the lower extremities. -Medical geneticist (talk) 20:16, 10 December 2008 (UTC)

Thanks for the info ... much appreciated. (Joseph A. Spadaro (talk) 15:47, 13 December 2008 (UTC))

Washing up

When washing up, does one get better results if one puts the Fairy liquid in the bowl before filling it with hot water, or after? And if so, why? DuncanHill (talk) 22:36, 10 December 2008 (UTC)

I doubt you'd get much (if any) difference by placing the washing up liquid in the bowl before or after. There might be a slight difference as the splashing of water on the liquid when placed before the water may increase the 'bubbliness'. That said, I imagine the best results in those terms would come if you placed the liquid in during the fill-up process. —Cyclonenim (talk · contribs · email) 23:28, 10 December 2008 (UTC)

Agree with Cyclonenim, definitely during. And for the foreigners here, it's Fairy liquid  :) hydnjo talk 02:53, 11 December 2008 (UTC)

Towards the end is better, because the earlier you add it, the more foam you get. While a bit of foam is good as a thermal insulation, it doesn't drain as well when you dry your dishes. — Sebastian 08:58, 11 December 2008 (UTC)

I always rinse the dishes with hot water, so lather is not a problem. DuncanHill (talk) 13:08, 11 December 2008 (UTC)

How about omitting the Fairy liquid and just leaving the dishes in the sink and waiting for Elves to wash them up? Edison (talk) 20:09, 11 December 2008 (UTC)

Lonely inventor builds working cyborg girlfriend in own home - malarkey or effective way?

Just read a news story where this is claimed to be the case.

Any thoughts on the matter? I'm immediately suspicious of his claims, as the videos presented in the article only show a working head and working hand. There is nothing showing the entire femmebot up and about and performing the tasks he says that it can perform (which, to my mind would be the vids that would really wow everyone). The still photos kinda look like he's just posed a rubberised mannequin in various places.

Also, the story appears in The Sun - which, as any fellow Brit will know, doesn't exactly have the best reputation as a newspaper for fact-checking.

So, what do you think? BS or not BS? --Kurt Shaped Box (talk) 23:38, 10 December 2008 (UTC)

Well, leaving aside The Sun's unassailable history of quality reportage, the official website of the project is at [6]. DuncanHill (talk) 23:42, 10 December 2008 (UTC)

Dunno about you - but programming the gynoid to violate the First Law of Robotics (she can apparently slap humans) seems like a really bad idea to me. --Kurt Shaped Box (talk) 01:07, 11 December 2008 (UTC)

It's a pretty impressive project for a one-man hobby effort - but it's FAR behind the state of the art. He's got together a large collection of miscellaneous bits of software and wedged them into the computer that drives the robot - but look at the movements of mouth and eyes in the video - they are laughably pathetic. A lot of the claims on the web site are of the form "In theory she could be programmed to..." - meaning he hasn't done these things and in all likelyhood is unable to do so. Move along - nothing to see here. SteveBaker (talk) 06:08, 11 December 2008 (UTC)

It was also claimed that this robot was built on a budget of $21000, which is pretty low-cost for a research robot prototype. I know of at least five or six robotics projects around here (e.g. [7], [8], [9] ) with a budget orders of magnitude larger - and it shows, in terms of equipment quality, manpower available, and total "advances" on the cutting edge. I would put this robot into the regime of "advanced enthusiast hobbyist" project - clearly the designer is very skilled but he's not a professional robotics engineer. On the one hand, "kudos" for doing a low-cost, low-budget innovation; on the other hand, if there was anything really innovative, then why isn't this guy doing it professionally? Nimur (talk) 15:16, 12 December 2008 (UTC)

Fascinating. Would it be possible for an amateur scientist such as myself to build myself a female android with Terminator style tissue engineered skin? My plan is to send them to Afghanistan without their burka, and when the fundamentalists try to attack them, they will be terminated instead. I think along with silent artificial muscle, which I think would be challenging for an amateur, these are the real problems, the rest is just artistic skill and programming (no problem in my case) because these artificial humans seem like an animated corpse with their dead eyes, odd cerebral palsy like movements and plastic skin, which does not have the unique translucency and texture of the real thing-a similar problem exists with CGI skin. I don't know if a real girlfriend would be cheaper, what with alimony settlements in Britain these days. And you can turn a robot off when it starts nagging, though it would have to nag a bit for realism. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 06:37, 14 December 2008 (UTC) Trevor Loughlin (talk) 06:40, 14 December 2008 (UTC)

I had the chance to visit Artificial Muscle, Inc., a few years ago - they're a spinout of SRI International that manufactures and sells ... artificial muscles. They target consumer products and research applications [10]. They built their material out of an electromechanically active polymer, and have used it for everything from replacing pump motors and camera lens zoomer mechatronics, to biomedical-research and robotics. It's not really "amateur"-grade, but you could probably purchase actuators from them. Nimur (talk) 15:58, 14 December 2008 (UTC)