Wikipedia:Reference desk/Archives/Science/2008 May 1

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May 1

Using LC-MS to test purity of water

Hello. If I obtain LC-MS or GC-MS machine, and learn to use properly, can I accurately test the purity of my tap water and filter water? Thanks you. Applefungus (talk) 00:26, 1 May 2008 (UTC)

Yes and no. You may be able to detect some impurities in the water but not others. Why do you need to test it? What are you testing for? These machines are expensive so it is probably not worth paying for one just because of your curiosity.--Shniken1 (talk) 01:25, 1 May 2008 (UTC)

Shniken is right, those machines are costly. And no, they wouldn't be very effective in testing Water quality. Chromatography might tell you a few of the substances in the water, but it would probably not give you their concentrations (depending on the machine i guess), nor would chromatography give you information about biological contamination (bacteria, virii, fungi, etc.). A more viable option is Bacterial water analysis, but might not be a great idea to do unsupervised if you've never cultured dangerous bacteria before. Are you worried your water might be conaminated with something specific? Are you just curious to see if your filter is really working? --Shaggorama (talk) 05:18, 1 May 2008 (UTC)

Provided you have standard solutions you can find concentrations with chromatography, but only chemical substances--Shniken1 (talk) 11:41, 1 May 2008 (UTC)

In analytical chemistry or analytical microbiology, it is usually more difficult to determine the concentration of an impurity if you don't know what the impurity is. ike9898 (talk) 16:41, 2 May 2008 (UTC)

Lutheran Church - Missouri Synod? Edison (talk) 04:18, 3 May 2008 (UTC)

Well, obviously not! It's the Lutheran Church in Malaysia and Singapore. --Trovatore (talk) 04:33, 3 May 2008 (UTC)

Bird Identification

I'm trying to identify this bird. I saw it in Boston, MA, along with another bird that was also unusually colored (orangeish, I believe). You can't see it very well in these pictures, but both had feathers on their feet. Both were very disoriented, flying into the wall when chased by some children (I couldn't get a picture of the other one, because the children had chased it away), suggesting that they might have been bred in captivity. Is this a domesticated pigeon, and if so, what kind?

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• 
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Thanks, --MagneticFlux (talk) 02:32, 1 May 2008 (UTC)

Looks like a variation of South German Monk. But I'm no fancier. --Lisa4edit (talk) 04:35, 1 May 2008 (UTC)

I made the images into a gallery so it won't bleed through the other questions. I hope you don't mind.--Lenticel ^(talk) 06:37, 1 May 2008 (UTC)

FYI, you can also just stick a <br clear="all"> at the bottom of the section. --Sean 13:41, 1 May 2008 (UTC)

Not at all. I appreciate the help! --MagneticFlux (talk) 05:54, 2 May 2008 (UTC)

software bug

Can anyone identify what happened here? I think I was opening Adobe Acrobat, and next thing I know, dozens of blue rectangles start appearing non-stop, each apparently a resized window.

Thanks, --MagneticFlux (talk) 02:54, 1 May 2008 (UTC)

Should be on the computer desk, but it looks like you had a LOT of windows open at once and then "tiled" them.--Shniken1 (talk) 03:03, 1 May 2008 (UTC)

It looks like a regular Microsoft crash and is normal. You may lose any data you input since you last saved a file; just restart the machine and it will probably be fine. If it happens again, reinstall Acrobat.--Shantavira|^{feed me} 07:08, 1 May 2008 (UTC)

Er, this is not a "regular Microsoft crash". I've never seen anything like it in over a decade of Windows use. If you minimize a window while Explorer isn't running, it gets resized to the height of its title bar and placed along the bottom of the screen in a pattern similar to what's shown here. But that doesn't explain why Acrobat was creating all those windows, nor why Explorer doesn't see them. My best guess is that it's an Acrobat bug of some sort. -- BenRG (talk) 18:02, 1 May 2008 (UTC)

Did you try expanding the windows? It could be some sort of malfunctioning adware trying to launch pop-up windows - especially if the PDF you were trying to read was from a website. Laïka 22:19, 2 May 2008 (UTC)

The PDF was academic rather than commercial, so I don't think it contained any adware. And though I double-clicked the blue rectangles, they did not expand. --MagneticFlux (talk) 02:15, 4 May 2008 (UTC)

i just wanted to check, the windows look kinda funny to me. i've never used vista so i'm not sure if you're using that or xp with a graphics card that has window frame options... at any rate, i would highly recommend checking for malware on your system. additionally, i would be inclined to agree with the "too many windows" especially if you tend to keep windows open over long periods of time (which includes using Hibernate). -76.217.98.145 (talk) 14:33, 7 May 2008 (UTC)

Why are autopilots not better at landing?

I just watched an episode PBS's Carrier series. It shows the extreme difficulty of landing jets in a rough sea on a carrier. It seems like pretty much every plane had to try multiple times to land. It's 2008. Why are humans still landing planes? Is there some fundamental difficulty with designing a fully automatic carrier landing system that is many times as reliable as a human? On a related note, I just learned that after the Space Shuttle's autopilot gets the craft within several miles of the runway, the commander takes over to land. I can hardly believe that humans would be superior to computers at these tasks. Why are autopilots not better at landing? (Or are they...?) --67.170.53.118 (talk) 03:46, 1 May 2008 (UTC)

I'm neither a pilot nor an autopilot designer, so I can't really give any real answer other than to note the old saw: "Flying is easy. Landing is hard." Anyone who has ever played with a flight simulator can attest to that. —Ilmari Karonen (talk) 04:06, 1 May 2008 (UTC)

The difficulty is of course the accuracy of an autopilot. Yes it is indeed 2008, and we have great autopilots for flight at high altitude. At 5,000 feet or 50,000 feet, it does not matter if you are off in your position estimate by ten or one hundred feet (or even 1,000 feet!). Realistically, radar and GPS can give pretty good accuracy to within a few meters.

When you are two inches off the ground, it is very dangerous to believe you are "a few meters" off the ground. You will slam into the ground "a few meters" early!

A very active area of research[1] in today's electronics industry is so-called "centimeter-resolution GPS", and one of its first intended applications is automated landing for aircraft.

In brief summary, the hardest part of automated landing is accurately sensing position relative to the ground in a reliable way. Present radars and GPS are not precise enough. Nimur (talk) 04:20, 1 May 2008 (UTC)

Fascinating. That surprises me a great deal. I guess expected an optical rangefinder or radar or something of the sort to be able to deliver extremely accurate distances at high speed and short range. I guess that answers my question. Thanks! --67.170.53.118 (talk) 05:16, 1 May 2008 (UTC)

Another reason is that sadly humans are "cheap and expendable" you can run the equivalent of billions of dollars worth of "sensor equipment" on a chicken salad sandwich and if "it" fails you hire another one. The same amount of sensor capacity would be very heavy, impede design (aerodynamics) something fierce and likely be forbiddingly expensive. Losing the rare planeload of passengers is a lot more economical. Not to mention if I look at the relative reliability of technology and well trained human I know where I'd put my money. This is your pilot speak...speak...speak...--Lisa4edit (talk) 04:44, 1 May 2008 (UTC)

There was a Mythbusters episode [2] where they explaned that most planes had an autopilot that could land the plane if need be.--Shniken1 (talk) 04:54, 1 May 2008 (UTC)

That is indeed true. Granted the airport has an ILS system (not to be confused with localizers that may not give altitude information), modern aircraft autopilots are able to give as soft landings as pilots. The autopilot will follow a predestined glideslope, until a point decision altitude, bit over the tarmac. It is still desirable for pilots to manage the last few hundred yards themselves. Since they are already there, why not? Gives practise, and they've practised for it thousands of times before. Scaller (talk) 09:43, 1 May 2008 (UTC)

This is complete conjecture, but maybe the reason is that airports don't move around very much, so they've got very well defined GPS coordinates, while an air craft carrier is always moving, both on the surface of the ocean as well as up and down. -- JSBillings 10:37, 1 May 2008 (UTC)

I wonder what your autopilot would do if it had to pull up again for some reason. I've been in several "landings" and attempted landings like that. What system is there currently on board for things like wind-shear, pothole bounce, cow on the runway and things like that? --Lisa4edit (talk) 11:17, 1 May 2008 (UTC)

(ec)Yes that is another problem, humans can assess a situation and act accordingly even if they have never experienced it before, a computer can only handle things the programmer had the foresight to include. The amount of sensors and software to process the data that would be required to replace the human senses and brain would be cost prohibitive, especially when humans are perfectly capable of doing it. Also, I doubt you'd find many pilots willing to put thier lives in the hands of autopilot. Mad031683 (talk) 15:15, 1 May 2008 (UTC)

Note that while raw GPS data doesn't readily provide the necessary precision for aircraft landing, there are a number of methods that enhance GPS info by supplementing it with signals from fixed ground stations (see differential GPS for several examples). These can improve precision to a few centimeters when one is wiithin a few kilometers of the ground station—sufficient for landing aircraft. This doesn't address hitting the moving target of an aircraft carrier deck, however. TenOfAllTrades(talk) 15:07, 1 May 2008 (UTC)

I've never landed a real airplane, but I've landed many times in simulators (not the Windows program - the big ones that move around as you fly them for training pilots). Once you are in range of OMI towers, there is a sort of funnel that you fly into. It guides you down to the runway. It is not dependent on GPS. It is based on radio towers on the ground leading up to the runway. So, if the airport is moving, so are the towers. To keep you in the funnel, a voice tells you things like "increase throttle" or "pull up". Basically, there is an autopilot landing the plane at all times. It just doesn't control the airplane. It tells the pilot what to do. Now - why pilots? What if you were just about to touch down and some fool drives an SUV onto the runway? A pilot will pull up and avoid an accident. An autopilot will land and assume the runway is clear. If you program to handle that situation, there will be another situation. If you program to handle that, there will be another one. -- kainaw™ 15:22, 1 May 2008 (UTC)

Therein lies the philosophical question about what role technology plays in human endeavors - should it replace our labor, or augment it? Clearly our landing systems presently "augment" the pilot's sensory abilities while leaving the decision making up to a human. Nimur (talk) 17:24, 1 May 2008 (UTC)

The issue is more complicated that many think. If machines did everything - absolutely everything - then human error, idiocy, and maliciousness would not be a factor. You wouldn't have to avoid an idiot driving an SUV onto a runway or a moron drunkenly swerving around the road or some lazy person forgetting to add a part to a product or... it goes on and on. Much of what we consider to be "unexpected circumstances" are based on the failure of humans to perform as expected. Machines can perform very much as expected and, if they are the only ones performing, will not need to consider all those unexpected circumstances. Sure, there will still be a bird flying though a jet motor or a deer running into the road, but the quantity of circumstances will be greatly reduced with humans taken out of the equation. -- kainaw™ 18:29, 1 May 2008 (UTC)

Yes, that's one good reason. Of course, the original poster did tangentially mention the Space Shuttle; it's not like that thing can just pull up and loop around for another landing if there's an SUV on the runway. But I suspect there are still some things the pilot can do, and in any case it remains the case that the total sensory and contingency planning capabilities of the autopilot and the human pilot combined exceed those of the autopilot alone. —Ilmari Karonen (talk) 19:03, 1 May 2008 (UTC)

Kainaw I've been working with machines for a very long time. So far I keep being rather unimpressed with their reliability and perfection. That includes some that I built or helped build. This goes into some other threads that exist here on reference desks. Dynamic systems can not have more than a temporary optimum. (At least unless someone has come up with a very new brand of physics while I wasn't looking.) That includes life, technology and everything to paraphrase Douglas Addams. On a related yet separate note, there seems to be a universal belief in GPS as the cure to everything. I grant you that it has become ubiquitous. What do you guys think of the dangers caused by solar weather (we seem to only have a Solar wind article.) Geomagnetic storms Geomagnetic reversal and Meteor showers. Looks like me like we are becoming more and more susceptible to effects like that. Should we maybe consider designing a paddle before we go further up the creek?71.236.23.111 (talk) 07:38, 2 May 2008 (UTC)

I do not see that GPS is necessary for autopilot carrier landings. A beacon system local to the carrier should be able to guide fully automatic landings. It could be RF or even optical. Perhaps the warrior macho ethic does not encourage such research. Radar on a runway could be used to initiate waveoff when a deer ran onto a land based runway. No pilot is as efficient as a modern computer at a tracking task such as landing a plane. Edison (talk) 04:15, 3 May 2008 (UTC)

And yet obvious answers can be deceiving. When measuring a new straight tunnel for the FEL, DESY engineers were surprised to find that laser was unsuitable to guarantee a sufficiently straight line over several kilometers and that taunt wire produced better results! --Lisa4edit (talk) 09:52, 3 May 2008 (UTC)

Interesting where can I read more about this? Nil Einne (talk) 12:18, 4 May 2008 (UTC)

Sorry, the book may not have been written yet, I think. It's probably not going to be "relevant knowledge" because very few people ever need to build a tunnel that's that straight for that long a distance. Engineering focuses on getting the job done rather than publishing the "Would you look at that" moments. Maybe someone is going to write a history of "How they built it" and someone they interview will mention it. It's just one of those curious things I've encountered where I, like everyone else, would have bet the answer was A and it turned out B is correct. (Apologies for not identifying the OR content.)--71.236.23.111 (talk) 17:35, 6 May 2008 (UTC)

As with some above, I'm far from convinced you could easily provided sufficient depth for any AI to be able to make the split second judgements that are sometimes necessary of pilots making a landing. As an example of this, let's say for example you are landing a nearly empty small plane and for whatever reason there is another plane on the runway about to takeoff (say a Airbus A380). For whatever reason you don't believe you will able to recover sufficiently to avoid a crash but you believe you will at least be able to avoid this other plane. Most pilots will make the decision here to risk sacrificing their plane and hopefully save the A380. On the other hand let's say you are landing a A380 with 800 passengers and see a deer on the runway. Again you think you're likely to have a bad crash if you abort the landing. On the other hand while crashing into the deer is not going to be good for your plane (and particularly for the deer), it's likely you will suffer few casulties. Most pilots will make the decision here to crash into the deer. These sort of decisions are easy for humans to make. A lot more difficult for AIs to make without sufficient programming. Of course, if you do have a good enough system, you may be able to make a system which is likely safer then a human landing the plane (i.e. you will likely save fewer lives by avoiding human error then you will kill due to a AI lacking the ability to make certain decisions most humans will make easily) but the trouble is that's difficult to prove and you still get lambasted by the press if your AI makes the wrong decision. Also if we're talking about passenger planes there's the added problem of even if the autopilot is a lot safer then a living pilot, you have to convince your customers of that which is not so easy. Driverless trains have mostly been accepted but I suspect this has at least something to do with the fact that they're on tracks and people have the perception (accurate or not) that there's a lot less that could go wrong and that a human needs to make a split second decision for (and even most driver less trains still have a human monitoring them somewhere I believe). Nil Einne (talk) 12:15, 4 May 2008 (UTC)

Also, some of the hypothetical solutions proposed discount the detail of infrastructure overhead. Especially regarding military activities, aircraft must be able to take off and land anywhere in the world. "Sensors could do it" is very different than "if we had to make a quick deployment to somewhere in the world, sensors would be in place on every piece of equipment we need, and we would have the technicians, engineers, and support staff in place to operate and repair it." A research-setting is a very comfortable place to test a technology, and I have no doubt that some variety of computers, software, and sensors could land a plane entirely autonomously in a controlled environment. Commercial and military aviation are by nature very risk-averse. Even something such as changing the door height on an airplane requires every airport that plane serves to upgrade its jetway to properly interface with the new door. Imagine how many peripheral technologies would be affected if we were to modify the runway instrumentation to suit a new landing technology. Nimur (talk) 16:19, 4 May 2008 (UTC)

Head Injury Symptoms

what are the symptoms of minor skull fractures that are left untreated for years?Idiotsage (talk) 08:00, 1 May 2008 (UTC)idiotsage

Why do you want to know? Nil Einne (talk) 09:46, 1 May 2008 (UTC)

Can a minor skull fracture be left untreated for years? 217.168.3.246 (talk) 12:39, 1 May 2008 (UTC)

The skull is a very large and complex set of bones. A minor fracture in a cheekbone, nose, jaw, or even inner ear will most likely never be fatal or cause more than discomfort (or hearing loss in the ear). TMJ can be caused by displaced bones from a minor fracture near the jaw. If you are referring to a fracture in the skull surrounding the brain, a small fracture in that area of the skull is not necessarily life threatening. Rumor is that Jackie Chan has a hole in his skull covered by a little plug. To get a proper answer, you must describe what you mean by "minor fracture" and state specifically what part of the skull you are referring to. -- kainaw™ 13:15, 1 May 2008 (UTC)

If the person survives, evidence of healing is usually visible. Archaeologists use these signs to determine whether a skull injury was the cause of death or happened many years prior to death. If the patient survives long enough for the bone to heal, the archaeologist may be able to conjecture about the quality medical care of the time period. For example, this case of forensic anthropology investigates an eye-socket bone injury. Nimur (talk) 20:09, 1 May 2008 (UTC)

Head trauma is a tricky topic. The brain is a very complicated organ and it's pretty easy to damage to it. A "minor" (as you put it) head injury could mean a fall from 30 feet that results in a broken nose and a little {concussion|concussive]] amnesia that goes away after a few hours. My point is the term minor, as applied to head injuries, is usually defined by the aftermath and not the mechanism of injury. If a head injury causes symptoms years later, it probably should not be considered minor. Of course, concussions have also been known to add up; many boxers develop cumulative, permanent brain damage after a career's worth of blows to the noggin. --Shaggorama (talk) 18:15, 2 May 2008 (UTC)

osteopathic vs. allopathic medicine

What is the difference between an MD and a DO? Whenever i try to talk to DO's about their practice, they just reassure me that they are just like MD's, receive bascially the same training, can perform the same procedures, blah blah blah. If they're the same, then why are MD's so suspicious of them? Why are they given a different name? I am having alot of trouble learning what the difference in medical philosophy and treatment is between allopathy and osteopathy (except for the inclusion of what sounds like chiropractic techniques, which seems to imply a different theory of disease), and the wikipedia articles don't make it much clearer to me. Anyone wanna jump in? --Shaggorama (talk) 12:31, 1 May 2008 (UTC)

I looked at our pages and was just as puzzled as you were. This link, however http://www.intelihealth.com/IH/ihtIH/WSIHW000/8513/34968/358839.html?d=dmtContent#background I found rather more informative. But I'm no expert. --Lisa4edit (talk) 14:43, 1 May 2008 (UTC)

DO colleges are primarily private. Their acceptance statistics are mostly lower than MD. So why is that? Many DO colleges have smaller endowments than larger medical research facilities, so they focus on primary care. In theory, MDs are supposed to be more research based, but DO schools are moving towards research based as well (for instance, osteopathic manipulation is becoming rare). But you can go into specialty medicine as a DO. They use a different test called the COMLEX instead of the USMLE during medical school, but they are equivalent. It may be harder to get into top residency programs with DO (such as Dermatology, actually I think its near impossible for derm) because residency admissions directors are probably MDs, but the vast majority of DOs go into primary care... I've seen a few in ER as well. They are equivalent in the court of law.

For those living outside the US wondering what the heck the above discussion is about, see Doctor of Osteopathic Medicine and Comparison of MD and DO in the United States Nil Einne (talk) 15:24, 1 May 2008 (UTC)

DO's concentrate more so on skeletal-muscular factors than their MD counterparts. The schooling is virtually identical, except for a few additional courses that DO's take that are related to a more..err...ideological difference. DO's are often confused with holistic medicine, which is rubbish. Wisdom89 _{(T / ^C)} 23:02, 1 May 2008 (UTC)

I'm trying to learn what the specific ideological differences are. I'm more interested in what differentiates ostepathic philosophy from allopathic philosophy than a few minor details that distinguish practitioners training. I'm sorry if I didn't make that clear in my question. --Shaggorama (talk) 18:06, 2 May 2008 (UTC)

5-HTP

I was wondering if I could get some help finding the oral pharmacokinetics of 5-htp without carbidopa in humans. The most important piece of information would be the therapeutic window value of Ceff. Half life of 50mg is good, too. Thanks. 71.195.4.244 (talk) 14:52, 1 May 2008 (UTC)Johnnycakes.

Guanine analogue antiviral drugs and caffeine

Hi my wiki friends. In vitro assays of caffeine show a mild antiviral effect. I was hoping someone could discuss with me if caffeine would be synergistic with famciclovir, or would it be antagonistic?

I know administration of both within normal dosages for me induces severe fasciculations and weakness in my distal limbs for hours. This side is not documented in literature, however; it makes sense to me based on PNS excitation of caffeine and famciclovir's effect on the dorsal root ganglia.

Basically, if you have cold sores treated with a drug, don't drink a lot of coffee and exercise =) —Preceding unsigned comment added by 71.195.4.244 (talk) 15:40, 1 May 2008 (UTC)

If you're getting undocumented side effects from a drug, you should probably consult a doctor. We can't give medical advice here. --Tango (talk) 23:56, 1 May 2008 (UTC)

I'm sorry but Wikipedia does not provide medical advice under any circumstances. It'd be inappropriate for us to comment. Regards, CycloneNimrod^Talk? 09:15, 2 May 2008 (UTC)

Cyanide and almonds

I have often heard that (at least for a certain fraction of the population) HCN has the odor of bitter almonds. I am also aware that certain fruit seeds and pits contain a small amount of natural cyanide. However, I was recently surprised to hear (in a lecture given by a clinical toxicologist) that it ise the cyanide constituent of almond flesh which gives this nut its characteristic almond smell. I would have previously thought the smell to come from an ester, and that the sensory similarity is coincidental. So my question is this: does the smell of almonds, from an actual almond, come from a cyano compound? Tuckerekcut (talk) 16:54, 1 May 2008 (UTC)

Harold McGee's magisterial On Food and Cooking says "The seeds of citrus, stone, and pome fruits generate cyanide, and stone-fruit seeds are prized because their cyanogens also produce benzaldehyde, the characteristic odor of almond extract". --Sean 18:02, 1 May 2008 (UTC)

There appears to be too different varities[3] of almonds. I wouldn't expect to die from it, even "toxic" substances (arsenic for example) are recquired for function in the body.[4]: "arsenic has been shown to promote longevity... (in rats)" 81.132.213.167 (talk) 18:09, 1 May 2008 (UTC)

The answer is both HCN and the benzaldehyde (C6 H5 CHO) that are produced from a glucoside amygdalin in the bitter almond are described as having an almond aroma. There are sources that say that about 20 % - 40 % of people can not smell HCN due to a genetic mutation. Another study described this picture as more difficult than anticipated. Sorry, I can only get abstracts, so I can't tell you whether they can smell benzaldehyde. I'd assume yes, because the inability is usually described as not being able to taste/smell bitter. Only HCN is described as bitter. This inability to smell the substance, has led to some sources describing HCN as "ocdorless". As our article says and the poster above found, there are 2 species of almond. Sweet almonds and bitter almonds. The amygdalin is only found in bitter almonds. How the oil in sweet almonds gets hydrolyzed to produce benzaldehyde or whether there is some other process/ substance involved (rather doubt that) I can not tell. HCN is described as highly toxic and eating a few bitter almonds can kill a child. Adults reportedly can survive up to around 20 (Not worth trying.) There is a former toxicologist who claims that no substance is inherently toxic or non-toxic and that minute amounts of toxic substances actually promote health. Or in short "What doesn't kill you makes you stronger." (Sorry the name's slipped my mind. Was some years back.) Cyanide and salts have been tried as cancer treatments but by and large turned out to be too toxic. As our articles state: "An HCN concentration of 300 mg/m3 in air will kill a human within a few minutes." (The stuff is volatile because it boils at room temperature) and "Bitter almonds may yield from 6 to 8% of hydrogen cyanide." As a fountain of youth this stuff definitely doesn't gain any prizes. (Unless we are talking Darwin award) Sorry about not putting in references, I had a crash and lost the sites. But you should be able to google them. Hope this helps. 71.236.23.111 (talk) 06:48, 2 May 2008 (UTC)

While it's true that everything can be toxic in the right concentration, I don't think it's fair to say what doesn't kill you makes you stronger. A small amount of aflatoxin may not kill you in the short term but I'm highly doubtful it makes you stronger, far more likely it kills you in the long term. Of course, I'm not denying a lot of stuff we consider toxic might be beneficial in a low concentration, I'm just far from convinced it applies to everything or even most things. But this doesn't mean you should avoid anything consider toxic like the plague. Just because it doesn't have a benefit and in fact may have a negative effect doesn't mean you have to be overly worried since clearly if the effect is small enough it's not worth the concern Nil Einne (talk) 17:15, 2 May 2008 (UTC)

Laetrile was the common name for Amygdalin used as an attempted cancer treatment.

Atlant (talk) 17:19, 2 May 2008 (UTC)

Actually, what doesn't kill you in many cases does make you stronger. See Hormesis and this commentary (copies available by email). Franamax (talk) 20:35, 2 May 2008 (UTC)

I personally prefer to stick with this (from our very own article)

However, that hormesis is common or important has not been fully established. Indeed, the idea that low dose effects may be (sometimes strikingly) different is accepted, but that the low dose effect is positive is questionable. In one of the better studied areas of hormesis, radiation hormesis the United States National Research Council (part of the National Academy of Sciences),[1] the National Council on Radiation Protection and Measurements (a body commissioned by the United States Congress)[2] and the United Nations Scientific Committee on the Effects of Ionizing Radiation (UNSCEAR) all agree that radiation hormesis is not clearly shown, nor clearly the rule for radiation doses.

and

The notion that hormesis is a widespread or important phenomenon in biological systems is not widely accepted.[17]

As I said, I'm not denying it does happen, I'm just far from convinced it applies to most things, let alone everything Nil Einne (talk) 17:12, 7 May 2008 (UTC)

Thank you, 71, for your very thorough answer. I certainly was not aware of the considerable toxicity of bitter almonds, likening them more to brazil nuts (with their thorium and radium content) than ordeal beans (which contain a muscarinic antagonist, and are considerably toxic). And to Nil Einne, I might suggest you investigate the etymology and founding principles of allopathic versus homeopathic medicine. As a subscriber (and practitioner) of the allopathic school, I should say that I agree with your observation. Though toxic effects are generally issues of concentration, rather than simply of substance, there certainly do exist compounds which have only been observed to harm. Lead comes to mind as a distinct example. Tuckerekcut (talk) 19:58, 2 May 2008 (UTC)

And quoting from my ref immediately above, "numerous toxic substances (for example, cadmium and lead) enhance growth in various plant species". This is from Nature, a decidedly allopathic journal, and refers to micro-doses, not pretend-we-shook-the-water-up doses. Franamax (talk) 20:42, 2 May 2008 (UTC)

Well as it turns out, human physiology is quite different from plant physiology Nil Einne (talk)

So if I like to flavor my coffee with almond extract, am I just asking for trouble? Edison (talk) 04:10, 3 May 2008 (UTC)

No. That's benzaldehyde. Either from bitter almonds with the HCN extracted/leeched or these days more likely artificial. (If it says "natural" it may still be hydrolized oil from sweet almonds.) Look for FFPA(Free from Prussic Acid = HCN)

Lisa4edit (talk) 09:30, 3 May 2008 (UTC)

chlorine damage to bathing suits

What household product can be used to treat bathing suits after use in a chlorinated pool to prevent damage to the elasticity65.10.204.67 (talk) 19:01, 1 May 2008 (UTC)

Chlorine is soluble in water (otherwise it wouldn't work well in swimming pools), so just rinsing them out thoroughly with lots of water should do it, I would expect. --Tango (talk) 21:28, 1 May 2008 (UTC)

I don't have a source for this, but looking at the processes, rinsing the bathing suits first in water, then in fabric softener should give extra protection. Fabric softener deposits a thin film of chemicals on the fibers of the material. The chlorine attacks the elastic material in your bathing suit because it is very reactive The fabric softener will provide an extra layer before the chlorine can get at your clothes. Microfiber should never be treated with fabric softener, so check your labels. --71.236.23.111 (talk) 07:06, 2 May 2008 (UTC)

People who keep aquarium fish have various treatments (called dechlorinators) to remove chlorine from water (chlorine being added to tap water to kill bacteria, but having the undesirable side effect of killing aquarium fish too). Usually these are based off of sodium thiosulfate. Soaking the suits briefly in a solution of sodium thiosulfate may remove residual chlorine. (How you would obtain sodium thiosulfate is another question - you could use aquarium water treatment, but be careful, as a large number of the treatments now days also have other stuff in them. These may be good for your fish, but may not be good for the suits.) -- 128.104.112.85 (talk) 19:02, 2 May 2008 (UTC)

Isopropanol dehydration

I will be dehydrating 70% isopropyl alcohol using salt, with the intention of using the more concentrated alcohol to clean various metal surfaces. I have NaCl with a small amount of sodium ferrocyanide, and magnesium sulphate heptahydrate. I am under the impression that both these salt formulations are suitable for my intentions (that is, will not produce any byproducts more toxic than the reagents). Is this correct? Tuckerekcut (talk) 19:59, 1 May 2008 (UTC)

I have no idea about the effect of the salts, but you can find 91% alcohol easily in stores, and it is possible to buy 99% from chemical suppliers...that may be easier. If you're determined to dehydrate though, someone else will have to answer. --Bmk (talk) 20:22, 1 May 2008 (UTC)

70% ethanol is is a perfectly fine antiseptic (and no different than anything more concentrated). No need to go through a labor intensive chemical manipulation if all you are interested in is sanitation and disinfection. Wisdom89 _{(T / ^C)} 22:58, 1 May 2008 (UTC)

I appreciate the comments, but I'm mostly just interested to know if this is a safe method of salting out isopropanol. Tuckerekcut (talk) 23:19, 1 May 2008 (UTC)

Searching "sodium ferrocyanide msds" and "magnesium sulphate heptahydrate msds" on google shows them as stable and reacting only to strong acids. (msds=Material Safety Data Sheet). You would of course be better off just to obtain the more pure form of isopropanol, it doesn't necessarily make sense to do your own de-watering when you can get it off the shelf. Franamax (talk) 21:00, 2 May 2008 (UTC)

ALbedo.

Does greener grass have a lower albedo than yellow grass? 99.226.26.154 (talk) 21:56, 1 May 2008 (UTC)

The answer might depend on what you mean by yellow. If the grass has turned yellow because it was covered up (as will happen if you lay something on your lawn) then I would have thought that the albedo will increase because the grass has changed colour through the withdrawal of light absorbing chlorophyll. However grass that is changing colour through ripening or drought will decrease in albedo. SpinningSpark 22:44, 1 May 2008 (UTC)

Characteristics of living things

"The fish died after living in the aquarium for many years." Which characteristic of living things does this illustrate?Lwiggs (talk) 22:48, 1 May 2008 (UTC)lwiggs

Senescence for one. Wisdom89 _{(T / ^C)} 22:56, 1 May 2008 (UTC)

Impermanence for another.--Shantavira|^{feed me} 07:02, 2 May 2008 (UTC)

Before I get too tempted to give you some humorous responses could you give us a bit more context. (If it is homework be honest, but at least give us the right aisle of the library.) --Lisa4edit (talk) 23:57, 1 May 2008 (UTC)

The truly lethal effects of Vogon poetry? Boredom? Starvation?? The facts are rather scant to make a determination. Paging Gil Grissom....

Atlant (talk) 17:23, 2 May 2008 (UTC)

Huh. I thought the answer was 42. Franamax (talk) 05:30, 3 May 2008 (UTC)

autogyro backpack vs. backpack helicopter

Would a autogyro backpack be easier to accomplish than a backpack helicopter? It could work like paragliding. The rotor would only generate lift.217.168.3.246 (talk) 22:55, 1 May 2008 (UTC)

About the electromagnetic spectrum

are there any kind of wave's wavelength longer than radio wave?what's it called?

are there any kind of wave's wavelength shouter than gamma ray?what's it called?

thank you very much--24.78.51.208 (talk) 23:21, 1 May 2008 (UTC)

Electromagnetic spectrum covers it, somewhat. — Kieff | Talk 23:24, 1 May 2008 (UTC)

While there are sub-bands within radio waves and gamma rays, I don't know of anything defined to be longer/shorter than radio/gamma. EM wavelengths can get as large as you like, but they're still generally called radio waves. Ignoring quantum mechanics, they can also get as short as you like, but are still called gamma rays (I would expect quantum mechanics gives a minimum wavelength on the order of the plank length). --Tango (talk) 23:54, 1 May 2008 (UTC)

Cosmic rays are not shorter than gamma rays? (I realize the article says that "rays" is a misnomer, but I specifically remember a poster in a chemistry teacher's room at my school that showed cosmic rays to be more energetic that gamma rays). Zrs 12 (talk) 01:31, 2 May 2008 (UTC)

Unless you want to get deep into wave particle duality, cosmic rays are particles. The other examples here are EM waves. 71.236.23.111 (talk) 02:44, 2 May 2008 (UTC)

Also, the energy ranges overlap. Gamma rays do not have either intrinsically more or intrinsically less energy than cosmic rays. Dragons flight (talk) 03:12, 2 May 2008 (UTC)

Yeah, the question clearly said "electromagnetic" (give or take the spelling). Cosmic rays aren't relevant. --Tango (talk) 10:46, 2 May 2008 (UTC)

There is also no lower frequency limit to electromagnetic waves. If someone stated a lower limit, such as Extremely low frequency extending down to "three Hertz" you could generate a 1 Hertz, or 0.1 Hertz, or 0.001 Hertz wave and prove them wrong. It just might not be useful for radio communication because of the humongous antenna required for the long wavelength. But they occur in nature or could be generated, if not easily detected. Edison (talk) 15:01, 2 May 2008 (UTC)

These names are really only a matter of semantics and nomenclature. Generally, "gamma ray" refers to any electromagnetic wave at that side of the spectrum. On the low end, there's a lot more dispute about naming. Some scientists use the term "base-band" to denote any generally low-frequency waves; "voice band", "telephone band", "ELF/VLF/ULF" low frequency waves; and many other names all refer to these signals. Nimur (talk) 15:52, 2 May 2008 (UTC)

"Baseband" tends to imply "the modulating signal" (as compared to "the carrier wave"). It doesn't really imply a frequency per se. The baseband signal could be 300-3000 Hz audio, or it could be video extending to 100 MHz, or it could be a highly multiplexed carrier telephony signal extending into the GHz range.

Atlant (talk) 17:31, 2 May 2008 (UTC)

When you get down to it, the electromagnetic spectrum really only divides into three groups:

1. The wave-like range, consisting of low frequencies that exhibit wave behavior but not particle behavior. Radio, mostly.
2. The light-like range, consisting of medium frequencies that can behave like waves or like particles, depending on the experiment you're doing. Infrared, visible light, ultraviolet, some x-rays.
3. The particle-like range, consisting of high frequencies that exhibit particle behavor but not wave behavior. X-rays and gamma rays.

The boundaries between the groups are fuzzy. --Carnildo (talk) 19:53, 2 May 2008 (UTC)

If it takes the Sun 225 million years to make one revolution of the Milky Way galaxy, then would a charged object on my desk create electromagnetic waves with a frequency of about 1.4 x 10^-16 Hertz?Edison (talk) 04:08, 3 May 2008 (UTC)

In a galactic frame of reference, quite possibly. Their amplitude would be almost immeasurable, though, I imagine. --Tango (talk) 12:35, 3 May 2008 (UTC)

You have not specified whether the object was charged here on Earth (i.e. is there an equal and oppositely charged object somewhere on Earth, or in fact anywhere sufficiently nearby that it may be treated as a dipole?) If so, the "net charge" of the rotating dipole is zero and you will probably have a non-propagating electromagnetic disturbance. Nimur (talk) 03:33, 4 May 2008 (UTC)

(And by "rotating dipole," I do not mean that the two charges orbit around a common center; I mean that the entire dipole is moving as a single entity. These are entirely different physical cases; the first will produce strong propagating waves while the other will not.)Nimur (talk) 16:33, 4 May 2008 (UTC)

i can understand now,but i still don't know is there's a spectrum included electromagnetic spectrum just like electromagnetic spectrum included visible light spectrum? and i read a book named eyewitness science--lightISBN 0-7737-2616-0,it says cosmic ray is higher frequency than gamma ray, but another book says that was wrong--24.78.51.208 (talk) 23:11, 5 May 2008 (UTC)

"Cosmic ray" can often be used as a generic and (scientifically ambiguous) word for "any kind of radiation in space." If you want to be precise, you should use a more exact term such as cosmic microwave background radiation (lower frequency than gamma rays, in that case). Many space-borne high-energy particles have frequencies that are in the gamma-ray range; the highest-energy particles could be "above" the gamma range. Many scientists do not put a precise upper-boundary on what a gamma-ray frequency range ends at, so anything of sufficient frequency would also be a gamma ray. This is a problem of terminology. Nimur (talk) 00:39, 6 May 2008 (UTC)