Wikipedia:Reference desk/Archives/Science/2010 May 4

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May 4

learning skills

On one of the Nat Geo documentaries that I watched, I saw why one messes up when they get nervous. It seems that there are two parts of the brain that learns a skill. One is a learner that is very clumsy and a learned part that executes the technique. When one needs to perform and cannot overcome their nervousness, the very clumsy "learner" part takes over and the resulting performance is bad. I think they used an amateur soccer player for this experiment and tricked him by saying that he was being watched by talent scouts. Anyone can direct me to its wiki article? --121.54.2.188 (talk) 00:39, 4 May 2010 (UTC)

I've never heard this idea before and am very sceptical. It doesn't make much sense to have your brain learning something twice, once not very well. We have an article on Anxiety and also the Yerkes–Dodson law which may be useful to you. --Tango (talk) 02:20, 4 May 2010 (UTC)

I think I wasn't very clear. One part of your brain learns the skill while the other part executes the learned skills. Anyways, it seems to be Procedural memory and messing up due to choking. I was able to get to them from muscle memory.--121.54.2.188 (talk) 02:26, 4 May 2010 (UTC)

(edit conflict)Its probably closely related to concepts like working memory vs. short-term memory vs. long-term memory. The article The Magical Number Seven, Plus or Minus Two specifically discusses on theory of Working memory and also contains some great links to related articles. I think there is a specific term related to this sort of performance-learning connection. As a teacher, you'd think I remember the term. I'll do some digging and get back to you. --Jayron32 02:22, 4 May 2010 (UTC)

The article Procedural memory also discusses learning procedures and processes, and the normal way in which procedures are learned. May offer some insight into the OP's question. --Jayron32 02:27, 4 May 2010 (UTC)

How long does that 'one part of the brain' learns? —Preceding unsigned comment added by 125.21.50.214 (talk) 11:38, 5 May 2010 (UTC)

Molar mass of Aluminium

What is the molar mass of Aluminium? Thanks in advance, --The High Fin Sperm Whale 01:45, 4 May 2010 (UTC)

It is in the article, in the infobox, under the title "Standard atomic weight". --Jayron32 01:59, 4 May 2010 (UTC)

dumbest idea in the world

So this has to be the dumbest idea in the world, but please confirm that it is. They have done various nuke tests in the desert where after the bomb goes off, the sand underneath is fused into glass, maybe dozens of feet thick. The dumb idea is: what if they do that underwater, as a way to seal the burst oil well in the gulf of Mexico? Would it exchange one environmental catastrophe for another? Radiation, tsunamis, etc.? Test ban treaty issues? There was at least one deep-water test in the 1950's (Operation Wigwam) whose effects weren't all that severe. 69.228.170.24 (talk) 01:57, 4 May 2010 (UTC)

Would the explosion fuse the sand into glass, or would it rupture the entire oil deposit, and send the entire contents of the deposit into the sea instantly, making the situation MUCH worse. Its a nice line of thinking, but beware of unintended consequences. --Jayron32 02:01, 4 May 2010 (UTC)

I think most of the heat would go into evaporating the water, rather than melting the sand. --Tango (talk) 02:06, 4 May 2010 (UTC)

Controlled frac is done all the time during drilling and enhanced oil recovery. It never needs nuclear weapon sized explosions. Most of the time, just pumping saltwater or steam down the bore is sufficient to frac the entire formation. In some cases, chemical frac (chemical fracture) is used - e.g., injecting an acidic drilling mud to intentionally break up the reservoir rock. Frac often increases permeability, rather than decreasing it - though the geomechanics is very complicated and depends on the circumstances. See, e.g., Hydro Frac at the Schlumberger oilfield glossary. Blowing stuff up in the borehole will more likely increase fluid flow; but there's a possibility of plugging the hole. Remember also that there's a pressure gradient - the oil is flowing up because it is at higher pressure than the water (and the rock) above it. That is why it blew up in the first place. Nimur (talk) 02:23, 4 May 2010 (UTC)

FYI the technical term for intentionally plugging the well to stop fluid flow is "bridging" the borehole. Nimur (talk) 02:32, 4 May 2010 (UTC)

You might find this article a good description of the likely consequences. Clear skies to you 67.170.215.166 (talk) 02:48, 4 May 2010 (UTC)

I can't believe I forgot to link to Completion (oil and gas wells). This is the term for the general set of techniques to manage a well, including casing, cementing, safety valves, and so on. I don't believe any completions use explosive of any type. Most use downhole tools and careful control of fluid/mud pumping. Nimur (talk) 14:39, 4 May 2010 (UTC)

Apparently it's not such a dumb idea, because if this article can be believed, the russians actually used nukes 5 times to seal leaks. Ariel. (talk) 19:59, 4 May 2010 (UTC)

For what it's worth, the article is from the Komsomolka, which is every bit as credible as our own National Enquirer. 67.170.215.166 (talk) 01:46, 5 May 2010 (UTC)

The U.S. government in 1964 proposed to use a series of nuclear explosions in Missisippi to excavate the "Divide Cut" portion of the Tennessee Tombigbee Waterway. These would have been excavation explosions of hydrogen bombs, which would have created ground shock waves and air blast as well as radioactive fallout according to the book cited. The Corps of Engineers at the time said there would be "[no fallout or radiation problems" because the explosions would be underground. This was part of "Plowshare," a program for the peaceful use of atomic energy, in which the U.S. government also proposed to set off nuclear explosions to dig harbors. Trying to seal up an oil leak a mile below the surface far out in the ocean sounds way more acceptable. Edison (talk) 19:46, 5 May 2010 (UTC)

It also requires a lot more precision than you get from your typical nuke -- as Jayron correctly pointed out, this method is more likely to actually make the leak worse. 67.170.215.166 (talk) 00:42, 6 May 2010 (UTC)

Would a nuclear blast be any more desirable then your traditional plastic explosives? I mean, I don't know if C-4 would operate properly at 150 atmospheres of pressure, but it would be a lot more simple to control what the explosion would do then simply dropping a nuclear warhead on it. Googlemeister (talk) 13:31, 6 May 2010 (UTC)

I think it's a good idea. Then we could write an article about the results! In fact if it was a catastrophic failure it might spawn several articles! Bus stop (talk) 13:41, 6 May 2010 (UTC)

In principle, high explosives could be used to bridge a gusher, but in this particular case just plain ole C-4 won't do -- since the well is in deep water, it requires some kind of waterproof explosive (such as Torpex). FWiW 67.170.215.166 (talk) 04:28, 8 May 2010 (UTC)

refrigerating foods

I have heard from some people that refregerating some foods spoil them.Is it true?amrahs (talk) 04:24, 4 May 2010 (UTC)

Never heard that before. See Refrigerator for details. There are some issues, such as freezer burn if meat is not packaged properly before freezing. Additionally, if the fridge is not cleaned properly, food may become contaminated through a process known as "cross contamination". But a properly maintained fridge and/or freezer should be perfectly safe for all foods, so long as the foods themselves are properly packaged before storing. --Jayron32 04:39, 4 May 2010 (UTC)

Actually, some foods will indeed spoil, not in the sense of becoming contaminated or rotten but in the sense that they will turn into something I wouldn't want to eat. Bananas, for instance become pretty disgusting when placed in the refrigerator. Dauto (talk) 04:45, 4 May 2010 (UTC)

Generally speaking, foods with a high water content (like bananas) are susceptible to "freezer burn" -- since water expands on freezing, any ice crystals that form tend to burst the cell membranes and thus degrade the food item's texture. Likewise, if frozen items (like ice cream) are thawed and then refrozen, large ice crystals can form that degrade the texture. In both these cases, however, the items involved are still safe to eat (though less appetizing). Foods made from grain, though, tend to have a different problem if refrigerated -- since they have very low inherent moisture content, they tend to exhibit hygroscopic tendencies at near-freezing temperatures, which makes them soggy and also could promote mold growth. (Incidentally, I store bananas in my fridge all the time, and I hardly ever observe any degradation in texture from it.) FWiW 67.170.215.166 (talk) 04:57, 4 May 2010 (UTC)

Correction: the phenomenon I described where ice crystals burst the cell membranes is not the same as freezer burn -- the latter is caused by dehydration from contact with the air. 67.170.215.166 (talk) 05:01, 4 May 2010 (UTC)

Not really refrigeration as much as freezing but an interesting fact is the founder of the modern method of freezing food was Clarence Birdseye, founder of the Birds Eye company. Until I discovered this I always assumed "Bird's eye" was just a arbitrary name. Vespine (talk) 05:52, 4 May 2010 (UTC)

Potatoes and other foods that are rich in starch will go off faster in a 'fridge than at room temperature. The temperature promotes the conversion of starch to sugar. CS Miller (talk) 11:08, 4 May 2010 (UTC)

Not correct. Warmth drives the starch to sugar conversion, not cold; cold temperatures put the spud into hibernation. Potatoes actually have a longer shelf life when kept near 0C (Please don't just take my word for it, but I do work in a huge foodservice distribution centre where we routinely have to store hundreds of different products to maximize shelf-life.) The problem with taters in the fridge is that they are not kept uniformly chilled; every time you open the door, you introduce more warm air and humidity and this fluctuation is what kills the spuds. If you have potatoes that you're planning on using, keep them cool, dry, and dark - slightly less than room temperature if you can. If you want to keep them for more than a couple of weeks, keep them cold, dry, and dark (you know, like in a root cellar), just let them warm up before you try to make fries with them.

It doesn't have anything to do with starch to sugar conversion, but certainly breads and other baked goods don't keep as long cool. Refrigerating breads causes them to go "stale" faster. (Staling in breads has more to due with rearrangement/recrystallization of the gluten network, rather than drying out per se.) Freezing baked goods, on the other hand, doesn't have the same problem. Cookwise and Bakewise by Shirley Corriher are good reads, if you are interested in the topic. -- 174.21.225.115 (talk) 15:25, 4 May 2010 (UTC)

You're right, placing fruits and vegetables that are grown in warm regions into the fridge damages them. It is due to their plasma membranes being susceptible to chilling. Basically the membrane stops being a fluid and turns into a gel, this creates holes in the membrane allowing the cell contents to mix. This is obvious with bananas as they go black but it also happens with tomatoes (and others - not sure which). It's not due to ice crystals forming as 67.170 says. Temperate fruit + veg are used to the cold and so are preserved by the fridge - their membrane lipids are less saturated and longer, so the Van der Waals forces between the lipid tails are weaker and the membrane remains fluid and intact at lower temperatures. 131.111.30.21 (talk) 12:34, 4 May 2010 (UTC)

See Banana#Storage_and_transport - it might only be when they are unripe that the fridge damages them. Also see Tomato#Picking_and_ripening - they remain edible but lose their taste when refridgerated. 131.111.30.21 (talk) 12:41, 4 May 2010 (UTC)

Chilling also causes decreased binding of ethene to its receptor, thereby slowing down ripening as well ([1]). It looks like this may also be the same in tomatoes. 131.111.30.21 (talk) 12:56, 4 May 2010 (UTC)

Note - "if frozen items (like ice cream) are thawed and then refrozen, large ice crystals can form that degrade the texture. In ...these cases, however, the items involved are still safe to eat" - is not true.

"The third and most important reason not to refreeze is increased risk of spoilage due to microorganisms. Many people thaw food by letting it sit at room temperature for several hours, giving the microorganisms in it time to get busy and partially spoil the food before it's refrozen. The problem is particularly pronounced in large pieces of meat such as a turkey, some parts of which may be at or near room temperature for hours during thawing. That's why turkeys should be thawed in a sink filled with water--the water equalizes the temperature and makes for faster thawing. Alternatively, you can thaw in the refrigerator, which is slower but retards spoilage by keeping the meat cool. Even so you're likely to have some multiplication of microorganisms. If you refreeze and rethaw, you've subjected the food to double the microorganism growth and double the fun.

If you must refreeze food that has been thawed in a warm place (or which has remained thawed in a cold place for a long time), you should cook the food properly first, then refreeze it. Even under the best circumstances, however, multiple freezing cycles aren't recommended. If you can't finish the food yourself, you're better off giving it to your household garbage disposal--ideally the one that barks or meows."[2] Exxolon (talk) 16:06, 4 May 2010 (UTC)

Ice cream that's been allowed to warm to a few degrees above freezing and then refrozen is no more dangerous than the food in your fridge. Clearly warmer is worse than colder (up to room temperature) but lets be reasonable. Rckrone (talk) 16:27, 4 May 2010 (UTC)

"Refrigeration" is not the same as "freezing." The OP did not ask about the freezer. Bananas turn dark quickly in the refrigerator, but refrigeration is claimed to leave them edible longer[3]. Some books claim that refrigerating tomatoes [4] and avocados [5] adversely affects the flavor and texture . A refrigerator is kept in a range of perhaps 34 to 38 degrees F (1-3 C). A freezer might be at 0 degrees F( -17C).A "self-defrosting" freezer causes worse freezer burns than older manual defrost ones, because of the low relative humidy needed to remove the frost from the walls. Edison (talk) 21:11, 4 May 2010 (UTC)

Tomatoes and bread are two things that tend to suffer from refrigeration -- tomatoes turn mealy, and bread dries out. Looie496 (talk) 00:55, 5 May 2010 (UTC)

Older refrigerators, before the "self-defrosting/no-frost" feature became so common, had higher humidity and baked goods, lettuce, etc did not dry out so quickly. An ice box was probably even better at keeping a high humidity in the refrigerator. Edison (talk) 19:33, 5 May 2010 (UTC)

Air navigation

What is an aperiodic compass, and how does it work? I've seen it mentioned by both Amelia Earhart and Charles Kingsford-Smith in their writings, but neither of them explains in any detail how it works or what advantages it has (if any) over an ordinary magnetic compass, Earth inductor compass, directional gyro or any other such device. Also, is it still used for navigation, or has it been completely replaced by other devices? Thanks in advance! 67.170.215.166 (talk) 05:12, 4 May 2010 (UTC)

Aircraft are very different to ships in that they can change heading rapidly, so ideally an aircraft compass can retain a reasonable degree of accuracy during a turn, without excessive overshoot. Prior to development of the gyroscopic compass, many aircraft were equipped with a magnetic compass specially developed for use in aircraft. This was more complex than the simple magnetic compass used for surface navigation. It was called the aperiodic compass. There is some good information available HERE. In modern aircraft the magnetic compass is used primarily as a back-up for the gyroscopic compass, and to ensure the gyroscopic compass is correctly aligned. Consequently, in modern aircraft the magnetic compass is simple and inexpensive because it is not relied on when maneuvering.Dolphin (t) 05:49, 4 May 2010 (UTC)

I wouldn't call the magnetic compass a "backup". It's the reference for the gyro, which has no sense of direction of its own. The gyro is set to the mag compass on the ground, and checked periodically when it level flight. It is, as you say, used for navigation and maneuvering, because it's easier to read and interpret that the mag compass. PhGustaf (talk) 06:19, 4 May 2010 (UTC)

So essentially it's a magnetic compass with an advanced magnetic damping system that prevents oscillation and overshoot (but also makes it lag behind the aircraft when maneuvering); and there's no longer any need for it because the gyrocompass is the primary instrument when maneuvering. Thanks for the info, and clear skies to you! 67.170.215.166 (talk) 06:14, 4 May 2010 (UTC)

I wasn't clear. All the gyro can do is point the same way all the time, with a little drift and precession. It has no idea which way is north. So the pilot sets it so it's pointing North, or whatever direction the magnetic compass says. The mag compass is the primary direction reference. The gyro has a bigger dial and is easier to interpret if the aircraft is turning, because is isn't sensitive to second-order issues, as is the mag compass. You mostly watch the gyro and check every so often to make sure it agrees with the mag. PhGustaf (talk) 00:26, 5 May 2010 (UTC)

I would imagine magnetic compasses on aircraft these days are electronic, e.g. using flux gates or other such devices. 69.228.170.24 (talk) 20:23, 4 May 2010 (UTC)

Could be. My pilot's license dates from 1976, and I might have missed stuff since. But even a plane with a flux gate compass would surely have a mag compass along: it doesn't weigh much, works even when the electric system fails, and doesn't break often. Modern pilots use GPS a lot. PhGustaf (talk) 00:26, 5 May 2010 (UTC)

It isn't correct to imagine that modern magnetic compasses in aircraft are electronic. If a modern general-aviation aircraft has a magnetic compass it will only be for orienting the gyroscopic compass. It wil be of the basic variety as used in boats, not even an aperiodic one. (Modern aircraft of the highly sophisticated jet-powered variety are likely to have no magnetic compass. Modern Inertial Reference Systems, GNSS and area navigation systems render the humble magnetic compass redundant.) Flux gates are linked to the gyroscopic compass to keep it aligned correctly - they are not linked to the magnetic compass.

Back to the original question. I believe the word aperiodic was intended to refer to the expectation that the compass needle would not follow the aircraft as it maneuvered but would remain accurately in the north-south alignment. Dolphin (t) 01:33, 5 May 2010 (UTC)

That is what Dolphin51's link says. According to it, an aperiodic compass is a magnetic compass like a ship's compass, but with better damping to keep the needle from swinging erratically.

As for highly sophisticated jet aircraft having no magnetic compass and instead relying exclusively on R-NAV, personally I find it extremely disturbing -- what if there's a total electrical failure? Or if lightning strikes the plane and fries the electronics? On some aircraft, all electronics are powered by engine-driven generators without any battery backup worth the name, so if there's a double-engine failure then all the electronics fail too and the pilot has no way to determine his/her heading. Didn't the Air France disaster teach the designers anything? It's high time that the pilots got together and demanded more stand-by instruments in the cockpit as well as full manual backup for all the primary flight controls! 67.170.215.166 (talk) 02:00, 5 May 2010 (UTC)

When you talk about total electrical failure you aren't talking about Modern aircraft of the highly sophisticated jet-powered variety. Such aircraft have two or more electrical systems, all independent so that the probability of failure of all electrical systems during one flight is extremely small. Similarly their electrical systems must be designed and tested to withstand lightning strikes. In the unlikely event of double-engine failure these aircraft have ram air turbines to provide electrical and hydraulic power. Where national regulations specify a universal requirement for a magnetic compass these aircraft are equipped with same. The airworthiness certification standards don't specify a standby magnetic compass. If redundant navigational capability is provided by a couple of flux valves, IRS etc then manufacturers are happy to provide the aircraft without the magnetic compass. (I see Aspro has supplied an image of the flight deck of a Boeing 747-400. This is not really what I have in mind by a modern aircraft of the highly sophisticated jet-powered variety. I am thinking of Airbus 300-series aircraft and probably B777 and B787.) Dolphin (t) 12:03, 6 May 2010 (UTC)

Well then, how do you explain the total electrical failure on the Gimli Glider? And FYI, a ram air turbine is useless at low airspeed (e.g. when landing), so it should NEVER be considered a substitute for battery backup. The lesson of the Air France disaster is, you never rely entirely on any powered system, and you always make provision to limp home with all electrics and hydraulics completely gone, if need be. That, and nothing short of that, is what I call real fail-safe operation. 67.170.215.166 (talk) 08:47, 8 May 2010 (UTC)

Why do you say the Gimli Glider suffered total electrical failure? The crew was in contact with ATC by radio for position information. Gimli glider says that on approach the reduced power from the RAT made the aircraft difficult to control (but not impossible to control). I'm not aware of anything to suggest the RAT failed to provide electrical power at approach speed. I see what you mean by real fail-safe operation. I'm afraid no modern high-capacity airliner provides what you want. Please consider opening an account on Wikipedia - no cost but many benefits. Dolphin (t) 01:55, 10 May 2010 (UTC)

The magnetic compass on a 747

Relax. Of course modern aircraft have magnetic compasses -it part of the CIAA regulations. For instance: Smith's Industries used to make many of them and SIRS has taken over.[6]. Look on WC and you'll see them on other aircraft types. A peculiarity of the magnetic compass, that has not been mentioned yet, is acceleration error. Meaning: that when the compass is acceleratingly, the rose tilts up and towards the nearest pole. Decelerating the effect is reversed. Anyone who has a magnetic car compass will be very familiar with this. Reading a magnetic compass (on an aircraft) in unstable air to maintain a steady course can therefore be a trying exercise. --Aspro (talk) 09:14, 5 May 2010 (UTC)

Good, at least they're not totally oblivious to the need for low-tech backups for all them high-tech gadgets. Whew! As far as acceleration error, I'm actually perfectly aware of that -- it's prob'ly one of the big reasons why the DG is the primary heading reference and the magnetic compass is used only to reset the DG. Which leads me to my second question: would an aperiodic compass be less susceptible to acceleration error because of its heavier damping, or does it not make a significant difference? 67.170.215.166 (talk) 00:49, 6 May 2010 (UTC)

Personally, I would ignore the “over shoot whilst turning” remarks because a fixed wing aircraft and even dirigibles don't turn on sixpences (unless spiralling down to their doom). A turn would add more momentum to the kerosene fluid thus causing the overshoot rather than reducing it (if you don't believe me -compare the two types of compasses together). An aircraft however, is always changing speed (as far as a compass is concerned) because every change to the control surface increases or reduces induced drag, as well as being bounced around by the atmospheric conditions. The other very noticeable thing about early aircraft (and light aircraft today) is the amount of vibration (which one can describe as also periodic). This adds to the other problems and makes holding a course difficult. Military and orienteering compasses too are all fluid filled so that you can handhold them and read accurately with ease. In practical terms, I would think one needs to be able to quickly read a compass to within 5 degrees. With a wobbly pointer this is very trying and wears the patients. So, in short: the aperiodic compass would tend to cancel out the constant alternating acceleration / deceleration effects as well as cancel out the effects of vibration. However, under a uniform constant acceleration it would still eventually show exactly the same deviation. --Aspro (talk) 13:17, 6 May 2010 (UTC)

shadows, mirror images?

Are shadows mirror images? Are they superimposable? At times, i noticed the images of shadow and mirror being alike, for ex.: a word printed on a glass shows shadow (behind the glass)similar to that of the original (not reversed) and similar image is also seen when a mirror is placed behind the glass on which the word is written. Hope i am clear..- anandh, chennai. —Preceding unsigned comment added by 125.21.50.214 (talk) 05:15, 4 May 2010 (UTC)

No, shadows are caused by an object blocking light rays, while a mirror image is caused by light rays reflected from the object being reflected a second time by the mirror. FWiW 67.170.215.166 (talk) 05:36, 4 May 2010 (UTC)

Regarding your second question, shadows are not actual things. A shadow is a place where there is less light - but it isn't no light at all. There is still some light, but less. If you have a second shadow on top of the first, then you have even less light then before. Ariel. (talk) 06:17, 4 May 2010 (UTC)

If you're facing the writing on the same side as the light source, the shadow looks "normal" (i.e. you can read it easily). The mirror on the other side of the glass shows you the mirror image of the other side of the writing (i.e. the inverse of the inverse) so it looks the same as the shadow. This doesn't mean that the shadow is a mirror image - but in this case they are superimposable. Hope this helps. Zain Ebrahim (talk) 13:07, 4 May 2010 (UTC)

FORTRAN Programming (Lahey Compiler)

I am trying to run one old fortran program (1980's). I compiled it using Lahey Compiler and i removed all errors and warnings. It is not running properly, if i give some print or write commands at some particular locations in some subroutines, it starts running. I am not able to understand without making any change in the code how is it running just due to some print or write commands and the results are still some what away from expected.203.199.205.25 (talk) 07:12, 4 May 2010 (UTC)

You will probably find a more receptive audience at WP:Reference desk/Computing. I suggest you delete your message from the Science Reference Desk and paste it into the Computing Reference Desk. Dolphin (t) 08:16, 4 May 2010 (UTC)

Cross-posted at Computing desk. Nimur (talk) 12:14, 4 May 2010 (UTC)

is it HF that kills? or F-?

I'm a little confused by the articles. Is F- toxic because it can form HF, or is HF toxic because it can form F-? Ignoring acidity, which is the more toxic species here? Is it because F- is a potent nucleophile, or binds with Ca2+ to form calcium fluoride? John Riemann Soong (talk) 07:26, 4 May 2010 (UTC)

It looks like the F- reacts with the Ca++ to form CaF2, but the H+ in the HF seems to function as a carrier ion (it carries the acid into the skin); even though any F- (or fluorine gas) is toxic in itself. --Chemicalinterest (talk) 11:05, 4 May 2010 (UTC)

see Fluoride#Toxicology F- is 'mildy toxic' and poisonous by hypocalcemia at relativly high doses. Hydrogen fluoride causes burns - in addition to any toxicity caused by flouride present.

In both cases the 'solution' is Ca2+ ions (ie as calcium gluconate / hydroxide / chloride) to precipitate F- as CaF2.

HF is more toxic because it both burns and poisons.77.86.70.220 (talk) 11:35, 4 May 2010 (UTC)

Is fluoride really a potent nucleophile? It holds on to its electrons tightly, so I don't think it's very happy to donate them to electrophiles.

Ben (talk) 00:17, 5 May 2010 (UTC)

The peculiar thing about F- is that although it indeed holds on tightly to its electrons, it has a high charge/size ratio because of its small size, which causes it to bind irreversibly to both calcium and magnesium to form insoluble salts. Living cells can't function without either, so they die off. This is why HF can cause such deep burns -- it soaks into the skin due to the action of the H+ ion, and the F- ion then kills the cells by precipitating the calcium. (Which is why the folks at our alkylation unit have to wear neoprene coveralls at all times while on duty.) 67.170.215.166 (talk) 02:08, 5 May 2010 (UTC)

An additional effect is that HF isn't a strong acid, so it doesn't necessarily cause serious "acid burns" (only 1-2 pKa units stronger than acetic acid I think). But because it's not highly ionic, it would be more able to penetrate skin and other water-tight membranes. So the H+ assists getting the HF in, where F- then can do some serious damage. Glacial-acetic poured on your hand? Wash it off right away, will be red/itchy for a few hours. Dilute HF few drops on your hand? You're in for a world of hurt for a long time. DMacks (talk) 02:18, 5 May 2010 (UTC)

A few drops of dilute HF wouldn't cause a serious burn, provided that you wash it off promptly with soap and water. It's the concentrated stuff (such as what we use at the refinery) that can kill you or burn you to the bone (yes, even a few drops of concentrated HF can burn you down to the very bone, I'm not kidding). Not to mention that concentrated HF can also give off poison gas when exposed to moist air. 67.170.215.166 (talk) 04:39, 5 May 2010 (UTC)

Is it maybe a mix of effects? Someone said that you need high doses of Na+ F- to get poisoned. So why does a few drops of HF hurt so much? It looks that HF is a good skin-soluble acid, so after F- binds calcium or magnesium, maybe the remaining H+ protonates bicarbonate buffer to form carbon dioxide? I mean I've spilled 1M HCl solution on myself before ... it didn't burn at all, except for a mild sting(I washed it off within 10-15 seconds). I assume HF would be way less acidic. John Riemann Soong (talk) 04:47, 5 May 2010 (UTC)

It's the skin permeation and cellular toxicity that cause it to hurt so much. HCl just attacks your skin by acid-catalyzed protein hydrolysis, and human skin is pretty resistant to that (especially the skin of an amateur chemist). HF, on the other hand, soaks into the skin and kills the living cells underneath by calcium precipitation, and it is this destruction of living cells that causes deep, painful burns (sometimes even to the very bone, as I said before). It's all the difference between scraping your skin on rough concrete vs. falling on some punji stakes. In the first case (concrete/HCl) only the outer layer of skin is damaged, whereas in the second (spikes/HF) there's damage to the underlying tissue (which hurts a whole lot more). 67.170.215.166 (talk) 05:09, 5 May 2010 (UTC)

It seems that ingesting 1 mmol of NaF would be worse than spilling 1 mmol of HF on your skin. Apparently it's the other way round. But wouldn't 1 mmol F- have the same effect, regardless of counterion? John Riemann Soong (talk) 17:54, 5 May 2010 (UTC)

Yes. 1 mmol F- would have the same effect, but the H+ ion has certain properties, such as ability to penetrate skin and put the F- ion into your system. Na+ ion does not have any toxic effects generally. For example, HNO₃ is much more reactive than NaNO₃. One can oxidize copper quite easily, while the other one can only with difficulty (or not at all). The "carrier" ion has an effect on toxicity, too. --Chemicalinterest (talk) 18:22, 5 May 2010 (UTC)

Are Kepler's laws rigth?

Hi, I hope this is the rigth corner to open this discussion.So I copy-pasted my former talk from other wikicorners.I claim:

Planetary orbits are not elliptical,but spiraled,with the Sun at the barycenter.Newton's universal attraction force formula F=G*M*m/r^2 gives the masses a tangential velocity so that each masses have to orbit one around the other (attraction force=centrifugal force). This tangential velocity Vp is constant:Vpm for m and VpM for M until the masses reach to the barycenter.Kepler says the contrary. According Kepler the tangential velocities are variable and the areal velocities are constant.But,when you draw the polar graph of two bodies you find, according Newton's F*dt=m*dV,the motion's equation r=-a*t*(t-tmax) which shows no sign of ellipse.No ellipse,no focus,no aphelion,no perihelion,nor equality of swept out areas in equal interval of time.Consider Nasa's photos of the galaxies: you will see the spiraled orbits of celestial bodies.Newton does not confirm Kepler; except for period's law (P1/P2)^2=(r1/r2)^3 which is valid only and only for circular orbits.Does Kepler has changed his reasoning;(elliptical orbits in 1609 and circular orbits in 1618)? Yes.He wanted to say, the elliptical orbits will be transformed to circular orbits with time.How does a solid elliptical shape could be transformed to circular shape,unless the orbits are not elliptical? This is possible when the orbits are spiraled: expanding and then compressing, billions of spirals. TASDELEN (talk) 07:35, 4 May 2010 (UTC)

Think about conservation of energy and see how your proposal fits in. Graeme Bartlett (talk) 10:22, 4 May 2010 (UTC)

Kepler's laws are simplified, empirical observations that are valid to a certain level of accuracy for certain cases that are valid to describe planet-like orbits. I don't follow your description about spirals; but in any case, there are other types of orbit, including non-elliptical orbits (such as those of a non-returning comet, or the orbit of a ballistic missile, which intersects the planet it orbits). These cases require mathematical treatments using the more general laws of Newtonian gravitation (and eventually, general relativity's even more complete description of gravitation). Your polar-form equation of planetary motion is not correct in the general case - I'm not sure where you got that equation from, but it looks kind of like an equation for a parabolic orbit - only one of many possible paths. Kepler's laws are applicable only if the orbit is closed and unperturbed. Our articles are extraordinarily descriptive of all possible cases. Nimur (talk) 12:22, 4 May 2010 (UTC)

TASDELEN, you are mistaken. Kepler's laws are completely consistent with Newton's law's within the "two body problem" approximation - That is, provided any pertubations introduced by other planets are negligible. Dauto (talk) 14:40, 4 May 2010 (UTC)

Science can not prove that something is true. All that it can say is that is has not been disproved. Googlemeister (talk) 14:23, 5 May 2010 (UTC)

RE "Does Kepler has changed his reasoning;(elliptical orbits in 1609 and circular orbits in 1618)? Yes.He wanted to say, the elliptical orbits will be transformed to circular orbits with time." If Kepler said that, it was probably due to his Platonism. Ellipses are "imperfect" and circles are "perfect." Another example: Some of Kepler's insights derived from his false belief that planetary orbits were related directly to perfect poly-sided (polylateral?) geometric shapes. Similarly, Copernicus incorrectly retained a version of epicycles in his theory to preserve the "perfect" circle idea. 63.17.78.34 (talk) 04:36, 8 May 2010 (UTC)

Dears

Graeme Bartlett|talk]]) 10:22, 4 May 2010 (UTC)

When I consider energy conservation equation,I write

F*r*dt=m*r*dv (energy conservation equation), then I write

1/2*m*Vr^2+m*gr*r+1/2*I*w^2=m*r*dVr (total energy with g variable)

This is a differential equation

dr^2+K*dt^2=2*r*d(dr) (side's term analysis meter^2=meter^2)

with solution

r=-a*t*(t*tmax)+K where K=2*gr*r+I*w^2/m=-a^2*tmax^2/(1+4*a)

On Cartesian, the graph of (r) is a parabola.

On Polar, this graph is a cardioidal looking spiral: billions of spirals.

Expanding then after compressing; with a max.point, only one max.point.

Located on a paraboloid surface along the orbit of the Sun in its galaxy.(our Milky Way)

This is the shape of the orbits. No sign of ellipse, no sign of aphelion, no sign of perihelion.

See the spirals on Nasa’s galaxies photos. The barycenter is not at one focus of an ellipse.

(details on my TASDELEN (talk) 08:34, 6 May 2010 (UTC)

Nimur|talk]]) 12:22, 4 May 2010 (UTC

"Your polar-form equation of planetary motion is not correct in the general case - I'm not sure where you got that equation from, but it looks kind of like an equation for a parabolic orbit - only one of many possible paths. Kepler's laws are applicable only if the orbit..."

the equation r=-a*t*(t-tmax)+K is a derivation of Newton's F*dt=m*dv.It is similar to s=-1/2*g*t^2+Vy*t+s0. I would like to give a Polar design of this equation,but I don't know how to send it to Wiki.You may draw yourself this graph by considering (t as corresponding to angles degrees and r as corresponding to the distances from the pole).I can e-mail you this graph and if you believe you may add it to my talk.Even if you do not believe.So,you may help me.

Dauto|talk]]) 14:40, 4 May 2010 (UTC)

I would like to e-mail you my "2 body"-"3,5,.. body" graphical systeme solution,but I don't know how to upload them to Wiki.If you want to help me,I send the graphs to you,and you upload them to Wiki.Large article and graphs!

Googlemeister|talk]]) 14:23, 5 May 2010 (UTC)

"Science can not prove that something is true. All that it can say is that is has not been disproved".I like this.Don't you think that Kepler's laws are disproved,by these Newtonian mathematics.According me Newton do not confirmes Kepler,except for periods.

63.17.78.34|talk]]) 04:36, 8 May 2010 (UTC)

The derivation from Newton's [F*dt=m*dv] results to [r=-a*t*(t-tmax)+K].And the shape of the orbits for the whole universe is spiraled orbits.Conical sections should not be considered for material orbits.No ellipse,no parabola,no hyperbola.But only spirals;for our solar system,for other solar system of our Milky Way.Even our Milky Way is a material which should orbit together with other galaxies around a barycenter.Spiraled system,in spiraled system which are also in spiraled system.I can e-mail you a graph for "Sun-Earth-Moon= 3 body system" which shows spirals in spirals then again in spirals.I don't know how to upload such graphs to Wiki. TASDELEN (talk) 18:18, 9 May 2010 (UTC)

Coefficient of drag at hypersonic speeds

Hi,

I was wondering how C_D varies with Ma at hypersonic speeds? Must graphs of C_D I have seen only go up to Ma 2.0, I'd like to know how it varies up to Ma 20 (eg what the Falcon Hypersonic Technology Vehicle experiences). Thanks! --58.175.32.19 (talk) 08:36, 4 May 2010 (UTC)

At hypersonic speeds, the linear model described in drag coefficient is totally inapplicable, so there's no real need for these charts. The shape and geometry become significantly more important than the total effective surface area. This is why an aerospike reduces drag, even though it adds surface-area exposed to the fluid flow. Consider this paper, Numerical Solution of the Hypersonic Viscous Shock-Layer Equations (AIAA, 1970). Nimur (talk) 11:31, 4 May 2010 (UTC)

Newton's cradle question

I recently bought an inexpensive Newton's cradle. Much to my dismay, it is not operating as nicely as I had expected. When the outside ball hits the remaining four, the middle three do not stay perfectly still, they wiggle quite a lot - and very quickly start swinging back and forth. This causes the motion to deteriorate very quickly. If I start by putting two balls into motion, it is even worse. Are there any simple adjustments that can be done to improve it? Thanks, decltype (talk) 10:19, 4 May 2010 (UTC)

Make sure that the row of balls is precisely in a straight line. Should be able to adjust the supporting cords. Graeme Bartlett (talk) 10:24, 4 May 2010 (UTC)

Also make sure that the surface on which the cradle sits is completely level. caknuck _° needs to be running more often 05:15, 5 May 2010 (UTC)

Curvy tunnel

On Balfour Beatty's website there is a tunnel image http://www.balfourbeatty.com/bby/segments/business-intro/ - ( Image url ) can anyone identify what project this is from, and what the tunnel is for?

More importantly - can someone explain why the tunnel is so crazily curved - is this trick photography or real. Thanks. Sf5xeplus (talk) 10:59, 4 May 2010 (UTC)

Balfour Beatty's website gives a contact e-mail address. Have you tried asking them about the tunnel? Cuddlyable3 (talk) 12:05, 4 May 2010 (UTC)

No I haven't contacted them.Sf5xeplus (talk) 13:41, 4 May 2010 (UTC)

The convoluted nature, the lack of a flat foor, and the diameter, would suggest it was for carrying water. It looks like a pipe inside a hydroelectric power plant, or a pumped storage plant like Dinorwig Power Station. These typically feature wire-bore tunnels for water to pass through, either for power generation or as part of the overflow system (see these pictures for the Hoover Dam's overflow tunnels). That said, every tunnel of that nature I can find pictures of has a smooth surface (either concrete or stone). Balfour Beatty does just that kind of business, but then they do lots of large civils in general. -- Finlay McWalter • Talk 14:17, 4 May 2010 (UTC)

I was wondering about sewage (google images show some similar page 4 and 5 - but most are smooth) - The shape doesn't make a lot of sense - appears to be a S bend followed by a turn to the right - more suitable for a water slide - anyone think the image has been distorted? Sf5xeplus (talk) 15:03, 4 May 2010 (UTC)

I'd suggest that it's the pedestrian part of an underground railway station, without the floor. Bank Underground station has at least one tunnel which is essentially the shape shown, with a staircase on the bit that's not horizontal. AlexTiefling (talk) 00:13, 5 May 2010 (UTC)

Addendum: although I can't be certain, I'd suggest that it might be the new access tunnel leading to the Northern Line platforms at Kings Cross St Pancras. AlexTiefling (talk) 00:34, 5 May 2010 (UTC)

Thanks, a passenger access tunnel makes much more sense. Sf5xeplus (talk) 08:50, 5 May 2010 (UTC)

Actually, this is a Ventilation Shaft and Escape Tunnel on Jubilee Line of London Underground.Vromascanu (talk) 17:03, 15 October 2010 (UTC)

Gloria Allred

Question moved to Wikipedia:Reference_desk/Miscellaneous#Gloria_Allred

substitute for peanut butter

I initially became a big nutritional fan of peanut butter when I read that it had no cholesterol and twice the protein of calves liver. Boy was I excited - peanut butter the perfect food. Then I started gaining weight only to realize 40 lbs later that even though peanut butter had no cholesterol it had plenty of fat. Not only did it have fat but it had saturated fat but alas I could not stop eating the stuff because I also loved the taste. Now my doctor says stop eating peanut butter or die so I have to find a substitute. What tasty treats with unsaturated oil can I find that will take the place of squshed gubbers? 71.100.1.71 (talk) 15:52, 4 May 2010 (UTC)

ask your doctor. Dauto (talk) 15:56, 4 May 2010 (UTC)

I did and he said that for a longer list to consult the Wikipedia. —Preceding unsigned comment added by 71.100.1.71 (talk) 15:58, 4 May 2010 (UTC)

All right then. Here's my suggestion: Eat more fruits and vegetables andexercise more frequently. Dauto (talk) 16:17, 4 May 2010 (UTC)

While finding an unsaturated fat alternative is probably better, the real problem here is that consuming excessive fat whether it's unsaturated or saturated is likely to increase your weight, simply because fat's energy density is so much higher than protein/carbs. You need to find an alternative that's both lower in saturated fat and lower in calories! Exxolon (talk) 15:59, 4 May 2010 (UTC)

The calorie thing is under control by limiting myself to 11 grams of peanut butter per meal (3 meals per day) for a diet plan of 21% fat, 67% carbs and the rest protein. So what unsaturated substitutes do you suggest? 71.100.1.71 (talk) 16:12, 4 May 2010 (UTC)

Typing the words "peanut butter substitute" into Google returned this search result: [7]. There's lots of options. --Jayron32 16:18, 4 May 2010 (UTC)

LOL... I told my doctor that when I asked the Wikipedia they said to Google. 71.100.1.71 (talk) 17:19, 4 May 2010 (UTC)

I was surprised to find almost instantly a link to waht is being called "soynut butter". I guess this idea already took off due to peanut butter "allergy's". 71.100.1.71 (talk) 16:55, 4 May 2010 (UTC)

• However, in comparing the labels of great value brand peanut butter and peanut free soynut butter the soy actually fairs worse with 14% instead of only 10% saturated fat and 4 grams of sugar instead of only 3. 71.100.1.71 (talk) 17:12, 4 May 2010 (UTC)

Why the " " on "allergys"? 86.178.228.18 (talk) 21:20, 4 May 2010 (UTC)

clearly it's an attempt to excuse the misuse of an apostrophe --Psud (talk) 06:16, 6 May 2010 (UTC)

You eat peanut butter with every meal? One of the key features of a good diet is that it be varied, otherwise it is easy for it to be deficient in something (there are plenty of nutrients that you only need a small amount of but that aren't in all foods, eating lots of different foods means you will probably be eating at least one with each of the essential nutrients in it). --Tango (talk) 17:30, 4 May 2010 (UTC)

Ignoring the obvious problems involved with a diet high in any fat, I personally enjoy SunButter. It has multiple varieties, which are more or less similar in taste to a comparable type of peanut butter. That said, it still has saturated fat, about 2/3 the amount in peanut butter. And its overall fat content (saturated plus unsaturated) is close to peanut butter. —ShadowRanger ^(talk|stalk) 17:17, 4 May 2010 (UTC)

To be clear, there are a whole lot of varieties of SunButter, and the similarity to peanut butter varies. Natural Crunch is the only one I buy regularly (I like crunchy over creamy), and it's a very close match (a little sweeter and less oily to my taste). I can't say how close the other varieties are to their equivalent peanut butter. Also, if I didn't make it clear, the primary ingredient in SunButter is sunflower seeds plus some sugar. —ShadowRanger ^(talk|stalk) 17:20, 4 May 2010 (UTC)

I suggest you try either "organic" or "natural" peanut butter. In both cases they won't contain the added trans-fats, which make it creamy, and will have somewhat lower saturated fats, too. Without that it will separate and need stirring, but that's a small price to pay for avoiding trans-fats. You might wonder why the label says 0 trans fats on traditional creamy PB. They just keep the amount low enough that they are allowed to "round down" to zero. In the US, anything under 0.5 gram can thus be classified as 0, even though getting that much trans fat in every serving is unhealthy. Look for partially and/or fully hydrogenated vegetable oil in the ingredients, that means they added trans-fats. StuRat (talk) 17:33, 4 May 2010 (UTC)

As a side note yes I am aware of the round down problem which Congress can eliminate by requiring all nutrients be stated as grams per 1000 versus grams per serving and then let the customer do the serving math. 71.100.1.71 (talk) 18:54, 4 May 2010 (UTC)

Wouldn't it be simpler to require trans-fats be listed to the nearest tenth of a gram, or hundredth, or thousandth ? StuRat (talk) 22:13, 7 May 2010 (UTC)

Grams per thousand inherently indicates multiple servings whereas decimal grams inherently indicate a single serving. Because a kitchen scale is not accurate for a single gram a single serving measurement ends up getting rounded down as in the serving size system we use today. By forcing everyone to think initially in terms of an amount larger than a single serving we deny manufactures an opportunity to round up or down. 71.100.0.29 (talk) 17:00, 8 May 2010 (UTC)

Focusing on saturated fat for weight loss is simply wrong. It won't help in the slightest. Saturated far affects cardiovascular health, but not weight. And switching to unsaturated fat for cardiovascular health is also wrong. Because the ratio of the various types of unsaturated fat matters (the various Omega types) too. And cutting fat out entirely won't help either, because aside from being bad for you because you need essential fatty acids, carbohydrates can be converted into fat by the body. If you really do want to fix your health then for starters stop eating sweetened peanut butter, switch to unsweetened (it's harder to find though). Second stop eating a lot of any one food. There are some foods that historically have worked as the main source of calories (staples), but most are not suited for that. Ariel. (talk) 19:44, 4 May 2010 (UTC)

Even with lots of available variety, the problem of staples is taste. People have a tendency to eat over and over again only the tastes they like. 71.100.1.71 (talk) 20:20, 4 May 2010 (UTC)

My 2 roommates and I consumed 40 pounds of peanut butter one school year in college. So I consumed about 6 kilograms, or 40,000 calories, or 190 servings in 223 school days, and that seemed like a lot at the time, but we really never got tired of it. Peanut butter is the most caloric portion of a PBJ: 190 calories in a serving of peanut butter, 140 in 2 slices of white bread, and 50 in a serving of preserves, 380 total.Calories vary with variety and quantity of ingredients. Edison (talk) 19:28, 5 May 2010 (UTC)

I agree. I lived on PBJ and milk/old fashioned Coca-Cola all through high school. Its the most portable meal I know. Here, this site might be for you. 71.100.0.29 (talk) 17:08, 8 May 2010 (UTC)

Meteorological deposition of carbon dioxide snow or frost

Seeing as the coldest temperatures on earth (eg Vostok Station) are often well below the freezing point of carbon dioxide, do these areas see deposition of solid carbon dioxide from the atmosphere, such as CO2 snowfall or frost? If not, why not? —Preceding unsigned comment added by Btxtsf (talk • contribs) 16:39, 4 May 2010 (UTC)

The CO2 content of the atmosphere (around 0.05%) is so low that the snow probably would be unnoticeable. And the size of the miniscule amount of CO2 would decrease much more when solidified, since solids are generally smaller than gases. --Chemicalinterest (talk) 16:51, 4 May 2010 (UTC)

But, on the other hand, you get very little traditional snow there, due to the low water vapor content in the air, so any dry ice would therefore be a larger component of the total. An interesting Q, I wonder if you can easily tell the difference between the two. StuRat (talk) 17:45, 4 May 2010 (UTC)

An easy way to tell the difference: water snow feels wet in your hand, CO₂ snow doesn't. Clear skies to you 67.170.215.166 (talk) 02:13, 5 May 2010 (UTC)

I'm assuming the reason the massive block of CO₂ ice I touched felt wet was because of the condensation of the water vapour in the air nearby, then? Vimescarrot (talk) 06:00, 5 May 2010 (UTC)

Yeah, that's right. 67.170.215.166 (talk) 00:55, 6 May 2010 (UTC)

Another way to tell the difference between ordinary snow and CO₂ snow is to squeeze a handful in your glove -- water snow sticks together into a snowball, CO₂ snow doesn't, and also makes a whistling or shrieking sound when squeezed very hard. FWiW 67.170.215.166 (talk) 00:58, 6 May 2010 (UTC)

Like the sound you get when you crush Styrofoam peanuts ? StuRat (talk) 03:56, 8 May 2010 (UTC)

Yes, kinda like that -- it's caused by pressurized CO₂ escaping from the snowball. Ordinary snow doesn't ever make this sound, no matter how dry or how low its temperature. (Well, it could make kind of a squeaking sound if very cold and completely dry, but never this sort of screech that CO₂ snow makes). FWiW 67.170.215.166 (talk) 04:35, 8 May 2010 (UTC)

That would only work well with wet snow. Dry powdery snow will not form a snowball. Googlemeister (talk) 13:26, 6 May 2010 (UTC)

And, at temps low enough that you could have CO₂ ice, the water ice won't be wet. StuRat (talk) 03:56, 8 May 2010 (UTC)

Fill a Teflon sample bag with CO2 and seal it and the Vostokians may see some, but otherwise no. As to the 'why'. That has already been answered elsewhere, so I'll just link to it.[8]--Aspro (talk) 17:49, 4 May 2010 (UTC)

Vostok Station is over 11,000 feet above sea level, giving an atmospheric pressure only about 2/3 of the sea level value. That's enough of a difference to drop the sublimation temperature of CO2 by at least a few degrees, meaning that the sublimation point has never been reached in recorded data even there. Looie496 (talk) 00:49, 5 May 2010 (UTC)

Chemical element lists

I'd like lists for the following:

1) The state of matter (gas, liquid, solid) of each of the 118 chemical elements at STP.

2) The names from which the chemical symbols are derived, for those which are not derived from the English name. For example, W = Wolfram = Tungsten.

I could eventually figure them out by reading all 118 articles, but I hope lists are already available. StuRat (talk) 17:53, 4 May 2010 (UTC)

List of elements by name, List of elements by boiling point, List of elements by melting point might help.--Stone (talk) 18:02, 4 May 2010 (UTC)

List of chemical element name etymologies should help with 2 ? —Preceding unsigned comment added by 77.86.70.220 (talk) 19:49, 4 May 2010 (UTC)

Just to note, you are only going to find state-of-matter information for about 100 or so of the elements. Many of the largest elements have only existed briefly as a very small sample, sometimes of as little as a few hundred atoms; far too small a sample to say anything reliable about its "state". --Jayron32 19:55, 4 May 2010 (UTC)

Also, the heaviest elements are either named after famous scientists, or not named at all yet. Clear skies to you 67.170.215.166 (talk) 02:16, 5 May 2010 (UTC)

Mercury and bromine are liquids. Fluorine, chlorine, oxygen, nitrogen and the noble gases (with the possible exception of ununoctium) are gases. Rubidium, cesium, probably francium, and gallium are liquids near room temperature. The rest of the elements that can be observed are solids.--Chemicalinterest (talk) 15:16, 5 May 2010 (UTC)

Na-Latin natrium, K-latin kalium, W-german wolfram, Fe-latin ferrum, Cu-latin cuprum, Ag-latin argentum, Au-latin aurum, Hg-latin hydrargyrum, Pb-latin plumbum, Sb-latin stibium These are names of elements whose symbols do not correspond. --Chemicalinterest (talk) 15:46, 5 May 2010 (UTC)

Thanks, but that's not a complete list. And, as far as incomplete lists go, I just can't stannum. :-) StuRat (talk) 22:40, 7 May 2010 (UTC)

Hydrogen is a gas obviously as well. Googlemeister (talk) 13:24, 6 May 2010 (UTC)

PhD programs and mental health

Can a PhD program be harmful to your mental health?--Mr.K. (talk) 17:57, 4 May 2010 (UTC)

Most academics would deny it, while a lot of PhD students would say that they suffered mentally during their slave work like thesis.--Stone (talk) 18:04, 4 May 2010 (UTC)

I'm not sure that most academics would deny it. Most that I know (which is many) would say, "yes, of course." They might say it is worth it (they might not), they might say it weeds out the less fortified (but they might also think it weeds out the non-crazy, as well). Academics are surprisingly straightforward about how crappy their overall career system is, even if they at the same time are likely to be less straightforward about whether or not that implies that academia is not all it is cracked up to be. Just my anecdotal experience. --Mr.98 (talk) 21:44, 4 May 2010 (UTC)

Can anything be harmful to your mental health? Yes. It is hard to attribute it specifically to a PhD program. Consider my PhD experience. I worked full time as a software engineer. I was raising two babies. I had to teach up 80 students (including grading homework and exams). I had to write not only a thesis, but also a readiness paper. I was also pestered with attending one symposium after another. Basically, I had about 30 hours of responsibility each day for about 3 years. So, did the PhD program cause mental health issues or was it the kids or dealing with idiots as a software engineer or dealing with students who claim their grandmother died three times each semester or simply never getting more than 4 hours sleep per day (and not 4 hours of continuous sleep)? I don't think you can blame the PhD program itself. It is an entire lifestyle that easily contributes to poor mental health. -- kainaw™ 18:11, 4 May 2010 (UTC)

There has been suicides of graduate students ,for example Jason Altom. How closely this is connected to his supervisor was disputed and will never be known.--Stone (talk) 18:14, 4 May 2010 (UTC)

As an addendum, I thought it important to point out that I believe my experience of three months of boot camp in the Marines was far easier than any particular 3 month period of my PhD program. It doesn't take much to mindlessly follow orders. However, being able to mindlessly do tasks until they are done does help a great deal when you have something like 80 programs to grade, each submission about 20 pages of source code, and you would much rather be doing anything else other than read through tons and tons of code that doesn't compile, doesn't make sense, and looks like random snippets of code pasted from various websites. -- kainaw™ 18:16, 4 May 2010 (UTC)

The answer is of course yes, as can school, the army, work etc... PhD's are notorious for their stress-levels (not for everyone of course) - WP:OR and it's quite suprising the percentage of PhD students who express a hate for their supervisor, or a deep unhappiness with the process..

In particular the transistion from primarily taught courses to self propelled is a factor, as it will be also the first experience for many of truly individual responsibility for their actions.

There's some results under http://www.google.co.uk/search?hl=en&ei=gXvgS5C3KJuTsQauqYzoBA&sa=X&oi=spellfullpage&resnum=0&ct=result&cd=2&ved=0CAYQvwUoAQ&q=phd+student+stress&spell=1 —Preceding unsigned comment added by 77.86.70.220 (talk) 19:56, 4 May 2010 (UTC)

One possible form of stress release for suffering grad students is write a comic strip. 69.228.170.24 (talk) 20:27, 4 May 2010 (UTC)

Yes, that is generalizable. (rolls eyes) --Mr.98 (talk) 21:44, 4 May 2010 (UTC)

Being in a Ph.D. program can be stressful, and stress can "harm your mental health." Being up for tenure can be stressful, too. Trying to get admitted to a good college can be stressful, as can trying to "do more with less" in the deliberately stressful environment of a large (or small) business, where years invested in a career can suddenly go "poof" due to corp reorg. I would expect that being in a modern war or occupation zone is rather more stressful. Being unemployed or underemployed is pretty stressful. I would not rate a PhD program as being the highest stress level I have encountered. Edison (talk) 21:05, 4 May 2010 (UTC)

You have to consider your initial susceptibility, general stress level, and lifestyle choices. If you're already inclined to depression or anxiety, for example, even the stress of high school or undergraduate university work might be enough to induce a full-on crisis. A person who is trying to juggle single parenthood, a full-time job, and graduate work is probably going to have a harder time of it emotionally than someone who has no major responsibilities and nothing else to do but concentrate on academic work. Knowing how to manage your time and how to de-stress yourself is an important factor. And making the right lifestyle factors is crucial, especially if you're already susceptible or stressed in the first place. Eat good healthy meals, get plenty of sleep, exercise regularly, have a supportive social network, and try to find time for things you enjoy, and you'll give yourself the greatest chance to get through a Ph.D. program - or college admissions or unemployment or almost anything else - with your sanity intact. 71.104.119.240 (talk) 01:08, 5 May 2010 (UTC)

Stress in a PhD student depends on many things, though I would say it is more related to the competitiveness of a field, the funding resources available, and most importantly, the political environment of the lab. Your stress will be greatly compounded by the latter. Life can be hell if your lab-mates are leeches or backstabbers and your supervisors are abusive or incompetent. It is likely that more labs have split or died due to politics alone than any other factor. However, if you work well, know your research field, having funding, and work in a relatively tame lab environment the stress is not that bad. Sjschen (talk) 15:07, 5 May 2010 (UTC)

HTPB

Our article on Hydroxyl-terminated polybutadiene says it is a polymer of butadiene terminated at each end with a hydroxide radical. So does the reaction to make it go like this?

nC₄H₄(OH)₂ → nH₂O + (C₄H₄O)_n

Also, do the all the C₄H₄ have oxygen between them? Thanks, --The High Fin Sperm Whale 19:20, 4 May 2010 (UTC)

The Os are at the end only (if in between it would be a polyether).

One synthesis uses hydrogen peroxide [9] US patent 5159123

The link probably has much of the answers you want.

The wikipedia article Hydroxyl-terminated polybutadiene incorrectly described it as a polyol - I've corrected that. —Preceding unsigned comment added by 77.86.70.220 (talk) 19:47, 4 May 2010 (UTC)

So do you use C₄H₆ and H₂O₂? --The High Fin Sperm Whale 20:10, 4 May 2010 (UTC)

Any radical initiator should work to start the polymerization reaction. --Jayron32 21:30, 4 May 2010 (UTC)

It needs to be convertable to OH - hence why H2O2 is used.77.86.70.220 (talk) 23:02, 4 May 2010 (UTC)

So are the bonds C-C? --The High Fin Sperm Whale 00:57, 5 May 2010 (UTC)

Yes they are. 67.170.215.166 (talk) 02:17, 5 May 2010 (UTC)

Clarification: the bonds in polybutadiene are a mixture of C-C (single) and C=C (double) bonds; what I meant was they're carbon-carbon bonds as opposed to carbon-oxygen. Clear skies to you 67.170.215.166 (talk) 03:58, 5 May 2010 (UTC)

Gravity

Let's imagine I'm riding my bicycle in a frictionless world. Taking into account the following:

a) If I'm riding forwards on a completely flat road, I'll have to fight no gravity force at all (exactly 0 g), since gravity only hinders upward movement.

b) If I try to ride up a 90º wall, I'll have to fight all of the gravity force (exactly 1 g), since all my efforts will be directed towards movind upward.

Therefore, if I am riding up a 18º climb, I'll have to fight exactly 0.18 g, and if I am riding up a 23º climb, I'll have to fight exactly 0.23 g. Is that correct, or is my reasoning flawed? If so, what is the mistake? Thanks.

Leptictidium (mt) 19:32, 4 May 2010 (UTC)

The first mistake, surely, is that if 0º = 0g, and 90º = 1g, then 18º = 18/90 rather than 18/100. --Tagishsimon (talk) 19:34, 4 May 2010 (UTC)

I think force due to gravity = mgsinθ might be of use here. sin 90 = 1 and sin 0 = 0, but sin(18) degrees is not 0.18 (it's closer to 0.3, I think). - Jarry1250 ^{[Humorous? Discuss.]} 19:36, 4 May 2010 (UTC)

Not sure where this line of questioning is leading, but no, you can't even ride a bicycle on a flat road without friction. DMacks (talk) 19:38, 4 May 2010 (UTC)

What about a rocket powered bicycle? A kite attachment? A gun to fire backwards? - Jarry1250 ^{[Humorous? Discuss.]} 19:41, 4 May 2010 (UTC)

The OP is missing the necessary trigonometry to calculate the gravity force vector relative to the direction that he is traveling. I think Jarry1250 has it, you need to take the sine of the angle relative to the ground to get the portion of gravity you have to combat. --Jayron32 19:46, 4 May 2010 (UTC)

And, for completeness, you should consider the normal force of the incline. Without friction, you will experience a horizontal force, because the normal force is perpendicular to the incline, and only its vertical component is canceled by gravity. The remaining horizontal component will cause you to slide. Most often, that horizontal force is counterbalanced by static friction. Nimur (talk) 19:49, 4 May 2010 (UTC)

Sorry, yes, that was a lapsus and I was thinking along those lines. My question can be summarised as whether the force of gravity one must fight is directly proportional to the angle on which one is moving. Leptictidium (mt) 19:52, 4 May 2010 (UTC)

It is proportional to the angle in a sense. If you make a triangle such that the base is flat (zero degrees) and the angle you are riding is the hypotenuse, the height of the triangle is the amount of "upward travel" that will be fighting gravity in your example. You use trigonometry to calculate the length of the height based on the angle. Assuming that the hypotenuse is set to a length of 1, sine of the angle is the length of the height of the triangle - which is the amount of upward travel. -- kainaw™ 20:03, 4 May 2010 (UTC)

I've tried riding a bicycle on ice, which is a bit like the OP's problem statement. In a frictionless world, the driven wheel will spin without providing any forward motion whatsoever when you operate the pedals, so if stationary you will remain stationary, and if in motion you will remain in motion. You will not be able to accelerate or brake. Second, due to a lack of traction, the instant the center of mass is not directly over the center point of the line connecting the points of contact of the tires with the ground, the tires will slide sideways dumping you on the ground. Steering will not correct the condition, as it does in normal bike riding, even if you are moving forward. Any gyroscopic effect of the spinning tires is negligible (unless you get the the driven wheel spinning very fast indeed). The only ability to climb an incline would be due to the initial forward motion, since there is by definition no traction. Edison (talk) 20:53, 4 May 2010 (UTC)

"Can't Burn Your Skin"

i aw this

http://www.amazon.com/CERTOL-INTERNATIONAL-LLC-USA-128-1/dp/B000KKQ8LA

how can they say "Can't Burn Your Skin," —Preceding unsigned comment added by Tom12350 (talk • contribs) 20:46, 4 May 2010 (UTC)

That description isn't for the Muriatic acid (hydrochloric acid is the more formal name), its for something called "Acid magic" , which is described as buffered hydrochloric acid. See buffer solution for a description of what a buffer is and what it does. I can't find a full ingredients list anywhere; the best I can find is that its a "proprietary blend". Here is an FAQ about the product: [10]. --Jayron32 21:14, 4 May 2010 (UTC)

Here's a forum discussion on it http://www.troublefreepool.com/acid-magic-as-an-alternative-for-muriatic-acid-t16607.html it doesn't look like anyone has an answer. Ariel. (talk) 21:36, 4 May 2010 (UTC)

As the FAQ says to always use gloves and goggles when using it, and they also insist on good ventilation, it doesn't look like they have much confidence in their non-burning non-fuming claims. DuncanHill (talk) 01:52, 5 May 2010 (UTC)

The buffer is prob'ly a weak base such as ammonia or an amine of some sort. But c'mon, if the acid's supposed to be strong enough to do its job instead of HCl, it's gonna be strong enough to burn your skin -- that's just a fact of life, deal with it. 67.170.215.166 (talk) 02:21, 5 May 2010 (UTC)

Not necessarily. A sufficiently concentrated buffer of the appropriate pH could be very mild on the skin, and still be able to efficiently lower the pH of your swimming pool if it is too basic. Remember, the purpose of this stuff is to lower pH. There are lots of ways to do that using chemicals which aren't going to burn on contact. --Jayron32 03:12, 5 May 2010 (UTC)

Having spilled 1M HCl on myself before ... I should say H+ doesn't burn if you wash it off immediately. I take keratin is a pretty tough thing to hydrolyse. (I assume hydrolysis of skin is the main hazard of skin contact with HCl solution). You could buffer it with a very weak base like phosphate or biphosphate. This changes the dominant H+ species. HCl is a chemically mild acid... it's only hazard is H+. With H2SO4 or HNO3 on the other hand, you risk redox reactions, turning your skin a nice healthy black. Mmm, I love the smell of burnt skin and organic ash in the morning. John Riemann Soong (talk) 04:58, 5 May 2010 (UTC)

Actually, HNO₃ turns your skin yellow by oxidation (I know from personal experience). H₂SO₄ doesn't oxidize human tissue -- it dehydrates it, essentially turning it to charcoal (good thing it hadn't happened to me yet). 1M HCl wouldn't burn even if it stays on the skin a while; 3M HCl, however, will burn just a little bit (even if promptly washed away) and more concentrated HCl will burn a whole lot more. Buffering the HCl will reduce the effect by raising pH, but by the same token it will increase the amount needed to do the job required. FWiW 67.170.215.166 (talk) 05:26, 5 May 2010 (UTC)

You see the clever marketing ploy by the folks at Certol, don't you? By buffering plain ole HCl, they accomplish 3 things in 1 fell swoop: (1) they make a product that's almost as cheap as plain HCl, keeping their costs down; (2) they make something that allegedly "won't burn your skin" (but still requires rubber gloves, according to the fine print), thus justifying a higher price; and most brilliantly, (3) they also make this product less effective than ordinary HCl, so it will take more of this product to do the job than if you use plain HCl. Low production cost + higher price + greater quantity required = more moolah for the company. Good job, Certol, and may y'all rot in hell for swindling your customers! 67.170.215.166 (talk) 05:38, 5 May 2010 (UTC)

Again, not necessarily. The purpose of the stuff is to lower the pH of your swimming pool if the pH is too high due to excess chlorination. A highly concentrated buffer solution whose pKa was something close to the target pH of what you want your swimming pool to be, could sufficiently correct your pool's pH problems at volumes similar to what you would need if you tried to do the same with straight hydrochloric acid. It claims a one-to-one volume correspondance with straight conc. HCl, and also claims to be less harmful to skin and fumes much less. The only reasonable solution would be a highly-concentrated buffer system, which could in theory work exactly as described. Since the stuff does actually contain HCl (the MSDS confirms that much), then we'd need a weak base to serve as the other part of the buffer system. I with the above assessment that its like ammonia or another amine. --Jayron32 05:37, 5 May 2010 (UTC)

Yeah, they claim all this, but you don't really know unless you read the fine print on the bottle... 67.170.215.166 (talk) 05:42, 5 May 2010 (UTC)

Normally they use a weaker acid (or less concentrated) such as sodium bisulfate to prevent burns. The buffered HCl may be just a dilute solution. --Chemicalinterest (talk) 12:04, 5 May 2010 (UTC)

Um, the amine is certainly too strong a base to be a buffer for HCl. (You'd get NH4+ and not H+ as the dominant species). What you want I think is to create an acidic species with a pKa of around 0 or 1 (instead of say, -1.7). Much weaker bases like bisulfate and biphosphate come to mind. John Riemann Soong (talk) 14:28, 5 May 2010 (UTC)

I think you may be on the money - did you mean sulphate as a base? - the pkA of hydrogen sulphate is ~2 compare somewhere between -4 and -7 for hydrochloric acid - this means that an sulphate would be almost completely protonated to HSO4- (still a strong acid) - the FAQ for the product notes that it reduces the level of fuming (usually due to free HCl excaping as gas in concentrated hydrochloric acid) - in the presence of 1 mol equivalent of sodium sulphate this would almost certainly acchieve the "90% fume reduction" advertised.. whilst still having a low pH (easily 1) .. also sodium sulphate is dirt cheap. 77.86.70.220 (talk) 19:28, 5 May 2010 (UTC)

Sodium hydrogen sulfate, not sodium sulfate, which is not acidic. --Chemicalinterest (talk) 01:32, 6 May 2010 (UTC)

(outdent) Our sodium bisulfate article notes that it's easy to get solutions of this chemical are about as acidic as 1M HCl but it doesn't fume and it's used to adjust pool-water pH. "What ions are in this aqueous solution?" is a pretty straightforward analytical-chemistry question. Will have to see if any pool-supply stores near me have small amount for cheap. DMacks (talk) 13:40, 6 May 2010 (UTC)

Digestive Cycles

I've read on several websites that the human digestive process follows a specific cirdadian rhythm that has three distinct phases. The appropriation cycle begins around noon (in most people) and continues until 2000 (8 pm). During this time the body is naturally predisposed to dispense plenty of energy to the digestive tract, and a person is most likely to feel hungry (the body's way of indicating it's the right time to take in food). The assimiliation cycle lasts from 2000 to 0400 and during this time the body is most efficient at the later stages of the digestion process: the absorption of nutrients from the intestines and delivery to the cells. The elimination cycle lasts from 0400 to noon and is the time when the body is most efficient at removing from circulation the byproducts of the metabolic process. Eating during the assimilation or elimination cycles is not recommended, as the body is not prepared to devote its energy to digestion at that time, and if one forces one's body to divert energy from the intestines, liver and kidneys, and/or other parts of the body to the stomach, all processes are performed less efficiently and this can result in health problems, weight gain, restless sleep, etc. The exception is fruit, which can be consumed at any time because it doesn't take a great deal of energy to digest. (Water is another exception of course.) I may have described it a bit too simplistically and yet in rather too much detail, but what I want to know is, is any of this true? —Preceding unsigned comment added by 71.104.119.240 (talk) 21:42, 4 May 2010 (UTC)

The body will adjust to whatever food cycle it is given. If you always eat, exercise or do other events at the same time of day, that's what the body will expect. There is no fixed cycle. Ariel. (talk) 00:54, 5 May 2010 (UTC)

Food, drugs and other rewards can entrain the circadian clock in the absence of light cues (e.g. constant light / constant dark). If I remember my Circadian clocks class correctly, you can lesion the SCN in a mammal (under normal light conditions) and other cues will start to entrain the clock.

There have been circadian clock studies carried out with methamphetamine. For the purpose of circadian clock entrainment, meth is basically a more powerful version of a food cue. The clock period can be lengthened to as much as 38-44 hours (for both mice and humans), when allowed to "free run". (It also explains meth users' strange behaviours). You can also entrain the clock to shorter periods (i.e. by controlling when meth is administered).

I really disagree with the whole idea that eating/exercising during an elimination or absorption cycle results in you being less healthy. The whole "energy diversion" thing is crock. Digestion is energetically-intensive, but it doesn't consume a lot of oxygen. Blood sugar is easily produced from fat. I'd go so far to say that exercising after eating, provided you don't do anything stupid that would cause you to throw up, would increase blood sugar levels available to organs. Muscles tend to use glycogen stores (which are local) before drawing on blood sugar. There are clock effects, but they are with respect to entrainment/efficacy, etc. As a student, the thing I'm most concerned about is my alertness, i.e. studying at the optimum time.

You should be worried about efficacy when efficacy is of the utmost importance. You can administer botulism toxin via injection to mice at a time when livers are "optimised" to handle it -- generally at a time after eating. The mortality rate is around ~8%. Inject it 12 hours out of phase and the mortality rate skyrockets to 90+%. Regular food isn't like a toxin -- it doesn't hurt for its metabolism to wait. John Riemann Soong (talk) 18:08, 5 May 2010 (UTC)

Btw, "inefficient digestion" implying "worse health" sounds like a twist on colon cleansing crap. In general, slower digestion is better. Also, absorption is generally not that energetically-intensive -- it's mostly passive diffusion combined with maybe a few active transport pumps for certain ions or minerals. John Riemann Soong (talk) 18:17, 5 May 2010 (UTC)

Humans eating pet food

Is it possible to eat cat and/or dog food? What about other kinds of pet food? ScienceApe (talk) 22:25, 4 May 2010 (UTC)

Humans are potentially omnivores although vegetarians object. Cuddlyable3 (talk) 22:32, 4 May 2010 (UTC)

Chap I knew at college ate a tin of dog food for a bet once. Mind you, he also used to drink gin by the half-pint, so it is possible his judgement was somewhat impaired. DuncanHill (talk) 22:34, 4 May 2010 (UTC)

(ec)Generally, yes. We might not like them very much, having less taste for innards than dogs or cats do, but we could probably subsist on them reasonably well. It's possible to eat birdseed or fish food (it's possible to eat dirt, too) but it would be hard to derive much nutrition from them. Note, though, that dogs and cats make their own Vitamin C and we don't. There may be other such differences. So if you want to live on them, you might need some supplements. PhGustaf (talk) 22:40, 4 May 2010 (UTC)

Although pet food bags are generally labeled "Not For Human Consumption," there's nothing in cat or dog food that's really going to hurt the average person. Pranksters, mischievous older siblings, and pet-loving parents can all tell you stories of humans who ate dry pet food once or twice and lived to tell the story. It's also been reported in the past that some elderly or disabled individuals, struggling to get by on their government handouts, would eat canned wet dog food because it was cheaper than meat considered fit for human consumption. I would guess that dog food would be more nutritious for a human than cat food, because humans, like dogs, are omnivores (yes, even the vegetarians; being an omnivore is a fact of human biology and refers to what the body is equipped to chew and digest, whereas vegetarianism is a lifestyle choice), whereas cats are carnivores. Some columnist, I forget who, once said that if you could only eat one food for the rest of your life, dog food wouldn't be a bad choice - it's specially formulated to meet the complete nutritional needs of an omnivorous mammal. 71.104.119.240 (talk) 00:46, 5 May 2010 (UTC)

I've often thought there should be a "Purina People Chow", which meets all the nutritional reqs of people, just like their other products meet all the nutritional reqs of various animals. Instead we settle for packaged "food" which is completely at odds with our health. StuRat (talk) 13:57, 10 May 2010 (UTC)

The reason they say "Not For Human Consumption" is because the factories that make it don't follow the same food hygiene/food safety procedures as are required by law for food intended for human consumption. That means there is a slightly increased risk of food poisoning compared to eating human food, but that's about it (and given that dogs aren't always getting food poisoning, I think we can assume the risk is still minimal - it's probably just the paperwork they don't bother with rather than the actual hygiene). --Tango (talk) 01:08, 5 May 2010 (UTC)

But don't for get the Melamine Pet Food Recall of 2007 a lot of cats and dogs wound up in veterinary hospitals over that. APL (talk) 03:12, 5 May 2010 (UTC)

Not really comparable. That was a contamination issue. It doesn't prove anything about the healthfulness of pet food in general, any more than the occasional E. coli outbreak proves that human food is inherently unsafe. 71.104.119.240 (talk) 08:14, 5 May 2010 (UTC)

I've been told that the average dog or cat has a "hardier system" than the average human, which is why they can eat things that aren't labeled for human consumption. Whether or not this is true I can't say. You'd have to have a pretty hardy stomach to handle some of the things I've known dogs to gulp down their greedy gullets, but I don't know it would affect the average human to eat insects, burrs, and day-old things, so it's hard to say for sure whether dogs have some kind of systemic advantage. Humans are fussier than they used to be, so it's possible we can't handle some of what our pets consume, and our ancestors consumed, on a regular basis. 71.104.119.240 (talk) 01:15, 5 May 2010 (UTC)

I don't know that dogs really do have a "hardier system". Many of the things they gulp down happily do make them sick, they just aren't smart enough to avoid those foods, like we are. Then there's a range of foods we humans eat without trouble which seem to cause them problems, even death, like chocolate. My brother's dog died after eating a grilled cheese sandwich, which blocked it's intestines, caused a gas buildup, put pressure on it's lungs and heart, and then caused death. StuRat (talk) 14:05, 10 May 2010 (UTC)

It would be remiss not to mention Ann Hodgman. Her article on the subject is pretty funny. (Note that there are a lot of things that don't kill people but carry some kind of risk of long-term effects. I doubt that anyone has any interest in doing studies on the subject.) Paul (Stansifer) 02:04, 5 May 2010 (UTC)

Comedy Answer : The Monkey Chow Diaries] <-- Man decides to eat only monkey kibble for a week. APL (talk) 03:15, 5 May 2010 (UTC)

Record Maximum

link

How can the record max for Pond Inlet, NU, be 25.7C recorded in March when the temp has never reached that even in July? —Preceding unsigned comment added by 78.32.155.164 (talk) 23:50, 4 May 2010 (UTC)

Options include a) the weather event on 5 March 1993 was a freak b) the data is wrong c) you're imposing expectations on the data which are not entirely supported by the data. We had 22 degrees in July, but 21.5 in February. How much of a problem is 25.7 in March, given the February value? Sure, it's counter-intuitive, but non the worse for that. --Tagishsimon (talk) 00:01, 5 May 2010 (UTC)

Surely you've answered your own question? Nil Einne (talk) 00:10, 5 May 2010 (UTC)