Wikipedia:Reference desk/Archives/Science/2008 November 21

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November 21

Question for all the people in the medical profession here...

Just how common are 'strangest/most impressive foreign body retrieved from an orifice' contests amongst emergency room doctors? My aunt used to be a nurse and she told me that it went on to some extent in all the (UK) hospitals she ever worked in. Generally, they'd throw in a few quid each and at the end of each month, the doc deemed by an impartial third party to have the most impressive 'find' would receive a bottle of expensive malt whiskey, or some expensive cigars. If not the doctors doing it, it was the nurses. This was in the 70s/80s, so the culture may have changed now, I dunno. --Kurt Shaped Box (talk) 00:21, 21 November 2008 (UTC)

Would a seagull be considered a "foreign" body? -hydnjo talk 00:33, 21 November 2008 (UTC)

I dunno. Can you make it fit up there? ;) --Kurt Shaped Box (talk) 00:34, 21 November 2008 (UTC)

I read that an expensive cigar was removed from the oval orifice. Edison (talk) 00:37, 21 November 2008 (UTC)

Perfect Edison, perfect! hydnjo talk

How about these? (Oops, disclaimer - I'm not amongst ...all the people in the medical profession here...) -hydnjo talk 00:47, 21 November 2008 (UTC)

I'd seen that list before - but not recently. Still makes me giggle slightly. My aunt once told me of a man who presented in A+E with a magazine from a semi-automatic pistol (with a condom over it) jammed up his rectum. That was probably the craziest one I've ever heard (I assume that his doctor won the prize that month). There was a guy who'd slipped a AA battery into/down his urethra and lost it too. --Kurt Shaped Box (talk) 00:59, 21 November 2008 (UTC)

Shocking! -hydnjo talk 01:06, 21 November 2008 (UTC)

I hope the battery was flat (makes it easier to insert)--GreenSpigot (talk) 01:28, 21 November 2008 (UTC)

Ouch ! even just thinking about it :( -hydnjo talk 01:38, 21 November 2008 (UTC)

There sure are a lot of anal-retentive people in this world, aren't there ? StuRat (talk) 03:19, 21 November 2008 (UTC)

More receptive than retentive. —Tamfang (talk) 20:42, 21 November 2008 (UTC)

Isn't the retention the issue which causes them to seek medical assistance ? Or do they just go there to show off ? StuRat (talk) 22:39, 21 November 2008 (UTC)

Per the list cited by Hydno, the 100 watt light bulb would likely be the A19 size, 2 3/8 inches (6 cm) across at the broadest point. Such a bulb would easily shatter, complicating the removal. A spiral compact fluorescent bulb would seem even more likely to break, and in addition would release a bit of mercury. The development of small LED replacement bulbs would seem to offer advantages beyond efficiency, service life and absence of mercury. Edison (talk) 04:34, 21 November 2008 (UTC)

Thanks Edison, your bright comments are sure to illuminate the darkest recesses of our minds. (Or any dark recess, really.) StuRat (talk) 05:40, 21 November 2008 (UTC)

Yeah - but that's a little bit like packing match-heads into a tin can, isn't it? --Kurt Shaped Box (talk) 22:57, 21 November 2008 (UTC)

By tradition, if they remove an expensive bottle of malt whiskey from an orifice, the patient gets to keep the cash. --Sean 15:34, 21 November 2008 (UTC)

Where do they put the cash, exactly ? And do they wait for the receipt ? StuRat (talk) 15:43, 21 November 2008 (UTC)

Just swipe an ATM card. Though only for male patients...for ladies, no way to enter what the PINis. Okay, that was a bit of a stretch. DMacks (talk) 17:34, 22 November 2008 (UTC)

You should be ashamed of yourself... that was terrible! :) --Tango (talk) 21:53, 22 November 2008 (UTC)

Yes, you should be ASShamed. StuRat (talk) 17:02, 23 November 2008 (UTC)

Quantum dots

While doing a project involving the fluorescence of quantum dots, I noticed that only the radius of the quantum dot effected the wavelength of the light it fluoresced. The larger ones fluoresced red and the smaller ones fluoresced green. I was using an almost UV source for excitation. While doing this experiment, I did not feel the solution containing the dots changing temperature, but the energy was obviously not conserved in the form of light. So my question is, where is the extra energy going? There is quite a bit of energy between the almost UV and the almost IR. What type of energy did this become. TIA, Ζρς ι'β' ^¡hábleme! 03:55, 21 November 2008 (UTC)

It almost certainly did end up as heat. It takes quite a bit of absorbed light to generate an amount of heat perceptible to the touch. Try repeating the experiment under identical conditions, but fill the cuvette (or whatever your sample container was) with a solution of black ink or some other strongly absorbing substance. Under those circumstances, virtually all of the absorbed light gets converted to heat, but I'd wager that you won't notice a change in temperature as long as you're using your hand as a measuring device. The smll amount of excess heat gets dumped into the ambient room air just about as fast as it gets put in to your sample. TenOfAllTrades(talk) 05:14, 21 November 2008 (UTC)

Potassium bicarbonate question

Potassium chloride can be used as a substitute for sodium chloride (table salt), for those who wish to limit their sodium intake. So, can potassium bicarbonate be used as an antacid, in place of sodium bicarbonate, for those with upset stomaches who also want to limit their sodium intake ? StuRat (talk) 04:11, 21 November 2008 (UTC)

I would think that it would make a decent substitute, since it is the bicarbonate anion that functions as the antacid.CalamusFortis 04:42, 21 November 2008 (UTC)

As with potassium chloride, you would need to take care and consult a medical professional before using lots of potassium in your diet. Your body is MUCH more sensitive to fluctuations in potassium levels than to sodium levels; you can literally overdose on potassium quite easily... --Jayron32.talk.contribs 05:48, 21 November 2008 (UTC)

It is available to buy for eating and cooking purposes from some health food shops. It does not taste quite the same as the sodium salt, but has a potassium ion flavour, similar to the potassium sulfate and potassium chloride. Graeme Bartlett (talk) 11:24, 21 November 2008 (UTC)

Thanks. Which health food stores ? Does this include GNC ? StuRat (talk) 15:37, 21 November 2008 (UTC)

The last one I bought was branded Salt Skip, and from Health Spectrum. Also Healthy Life have it. I don't think we have GNC in Canberra. The price is five to ten times higher than the sodium salt, because so few want to buy it. Graeme Bartlett (talk) 20:59, 21 November 2008 (UTC)

I'm asking about potassium bicarbonate. It sounds like you might be talking about potassium chloride. StuRat (talk) 22:31, 21 November 2008 (UTC)

The product is definitely potassium bicarbonate. The same company produces both kinds of product. Graeme Bartlett (talk) 20:56, 22 November 2008 (UTC)

I wasn't aware that potassium bicarbonate was sold as a salt substitute, which seems to be what the name Salt Skip would indicate. StuRat (talk) 16:58, 23 November 2008 (UTC)

It's a bicarbonate of soda substitute. Graeme Bartlett (talk) 00:50, 25 November 2008 (UTC)

Then wouldn't it be called Baking Soda Skip ? StuRat (talk) 03:36, 25 November 2008 (UTC)

Double Gravitational Acceleration Paradox

If you calculate the gravitational acceleration of two objects with mass M and m, the gravitational acceleration will be GM/r^2 and Gm/r^2 respectively. So which acceleration should I use and what did I get wrong? ----The Successor of Physics 15:03, 21 November 2008 (UTC) —Preceding unsigned comment added by Superwj5 (talk • contribs)

The object of mass m accelerates at a rate GM/r^2, and the object of mass M accelerates at Gm/r^2. Where's the problem? Algebraist 15:07, 21 November 2008 (UTC)

Both gravitational accelerations are measured with respect to the center of mass of the system — not the other object. TenOfAllTrades(talk) 15:09, 21 November 2008 (UTC)

Or with respect to any other inertial frame, since acceleration is frame-independent (as long as you stick to inertial frames). -- BenRG (talk) 17:15, 21 November 2008 (UTC)

The acceleration of the two objects toward each other is the sum of the two. For one large object (like a planet) and one small object (like you), the acceleration of the large object is insignificant. StuRat (talk) 15:33, 21 November 2008 (UTC)

Er, actually it's GMm/r². Does that answer your question? --Heron (talk) 21:04, 21 November 2008 (UTC)

That's the force between M and m, not the acceleration!(To Heron only) ----The Successor of Physics 04:02, 22 November 2008 (UTC)

Pipe bursting temperature

A friend of mine said he was told that if you turn your house's thermostat temperature below 55ºF you run the risk of pipes bursting. This seems rather high to me (also considering we had our house at 54ºF all winter last year when we were out of the house and had no problems). What's the real risk here? For context I live in the Boston area (where it does get quite cold in the winter, from a water-freezing point of view), in a multi-story house with a basement. Our house heating is maintained through radiators in the individual rooms (fairly old house). We keep it at 54ºF at night and when we are away from the house because heating oil is incredibly expensive. --98.217.8.46 (talk) 16:31, 21 November 2008 (UTC)

The pipes will only burst if the water actually freezes, 54F is quite a bit above freezing point (although that's the temperature of the air inside your house, the pipes may be a little colder), so I would expect you'll be fine. I've only ever heard of people having problems with pipes bursting when they've not been living in the house over winter - if you are there and it's warm enough for you to be reasonable comfortable, then the pipes should be fine.--Tango (talk) 17:01, 21 November 2008 (UTC)

I had a pipe burst once, even though the house temp was set at 50ºF. It was on an exterior wall leading to an outside tap. After fixing the pipe, I installed a cutoff valve before the pipe gets to the exterior wall, so I can now turn off the water, open the outside faucet to drain the contents, and make it through the winter without a flood. StuRat (talk) 17:17, 21 November 2008 (UTC)

Yeah, we cut the water to outside taps for this reason. --98.217.8.46 (talk) 18:41, 21 November 2008 (UTC)

As long as you use your water every day, and keep water flowing through the pipes, there is little danger of your pipes freezing. I grew up in New Hampshire, where the weather regularly stays permanently below freezing for weeks at a time, and we took no special precautions as long as we were occupying the house. There can be problems if you leave the house unoccupied for several days, in that case it is recommended that you turn off the water in your house and drain all of the pipes. Also, if you live somewhere where the temperature stays above freezing for significant portions of the day (say average January highs in the 40's), and where the temperature does not drop below freezing except occasionally at night, then you are probably safe regardless of whether or not the house is occupied. I say probably, because strange and unpredictable things do always happen; if you are away on vacation from a normally mild climate, and a strange cold spell comes along while you are away, unexpectedly, all bets are off... --Jayron32.talk.contribs 17:38, 21 November 2008 (UTC)

Where I have lived, occasionally the pipes freeze up in winter, but they never burst. Are there better quality pipes that can withstand the pressure? Graeme Bartlett (talk) 20:42, 21 November 2008 (UTC)

It has to do with the way they freeze. Normal freezing only increases the size by about 10%, and most pipes can stretch that much. The problem is when the pipe freezes from both ends, pushing the water in front of it from both sides. This results in a bulge where the two ice formations meet, which can be enough to burst most pipes. Repeated freezing can also stretch a pipe beyond it's fracture limit. StuRat (talk) 22:25, 21 November 2008 (UTC)

I recently bought a home that has copper water pipes. The tees and elbows are joined to the pipes with solder (sweated). Some of the tees and elbows had become detatched from the pipes. I theorize that the water in the pipes froze and the expanding cylinder of ice pushed off the tees and elbows. The copper pipes must also have bulged a bit. The home had been empty for 3 years and unheated. It is in western Pennsylvania, where we just had 10" of snow. I am going to replace all the pipes with PEX pipe and fittings. PEX plumbing pipe, which is new, is easy to work with. There is no soldering. (A torch is a fire hazard in close places, like inside walls). PEX pipe can be easily cut without a hacksaw, and unlike iron pipe it needs no threading. PEX is also easier to cut than ordinary plastic water pipe, and it can be given a bend around a corner by hand (if the turn is not too sharp). PEX elbows are available for sharp turns. —Preceding unsigned comment added by 98.16.67.220 (talk) 00:21, 22 November 2008 (UTC)

What is glabrata?

In relation to Women's health? --Emyn ned (talk) 18:18, 21 November 2008 (UTC)

Candida glabrata. Fribbler (talk) 18:23, 21 November 2008 (UTC)

Mystery objects

Can anyone help identify these objects? They were found in the shed of a dead relative (a mechanic who was also into woodworking). Hut 8.5 20:24, 21 November 2008 (UTC)

The serrated disks are blades for a circular saw. I would guess that the rest are other components for the same device. StuRat (talk) 20:39, 21 November 2008 (UTC)

Yep, you might like to see spindle as well. Very much the woodworker... (those articles could use a pic like this). Julia Rossi (talk) 21:58, 21 November 2008 (UTC)

One of the blades is inscribed with the name Dormer, a manufacturer for precision tools in Nottinghamshire with stacks of outlets in many countries. [1] gets you to their website. --Cookatoo.ergo.ZooM (talk) 22:01, 21 November 2008 (UTC)

Thanks very much. Hut 8.5 22:28, 21 November 2008 (UTC)

Nottingham... my home town! We're apparently good for something other than violent crime! —Cyclonenim (talk · contribs · email) 23:13, 21 November 2008 (UTC)

Surely the Sheriff of Nottingham can deal with the disruptive behaviours of a few outlaws? Edison (talk) 23:17, 21 November 2008 (UTC)

You'd be right, if he wasn't dead for several hundred years. I've heard decomposed bodies left only with a skeleton find it hard to fight crime these days. Damn life cycle. —Cyclonenim (talk · contribs · email) 00:32, 22 November 2008 (UTC)

Well I'll be damned, apparently there is still such thing as the Sheriff of Nottingham, although it's appointed to the mayor and no gangs will look at him and shiver about anything but his looks. —Cyclonenim (talk · contribs · email) 00:34, 22 November 2008 (UTC)

Scientific term and research on the topic

For this question, just assume the following is true: A human is shown a pattern "abbb" and asked if it best matches "accc" or "cbbb". The human answers "cbbb" because the a is insignificant to the three b's. So, the human is biased towards whatever is mostly visible.

For a paper I'm writing, I'm discussing the tendency for AI pattern matching algorithms to be biased in the same way. However, I don't know what the scientific term for this bias is. Does anyone here know it? Also, if anyone has links to research on it that I can cite, that would be overly helpful. -- kainaw™ 22:37, 21 November 2008 (UTC)

Sounds like you might be interested in Hamming distance. --Carnildo (talk) 00:09, 22 November 2008 (UTC)

The human and/or the AI is biased by its choice of similarity measure [2] of which the hamming distance is one. Speaking of bias in general, every AI need to have some kind of bias to be able to generalize to unseen examples. This is called bias-variance tradeoff or the bias-variance theorem and is covered in most introductory books on AI and pattern classification, though I can't guarantee you'll grasp it quickly or intuitively. (I certainly didn't :-)

Thanks. I almost had it. I was looking for psychological distance. Now, I can reference that little section of this paper and wrap this thing up for review next week. -- kainaw™ 13:21, 22 November 2008 (UTC)

Would humans really favor "cbbb"? I think I'd favor "accc," it'd feel like it was "next" in the order. zafiroblue05 | Talk 01:52, 23 November 2008 (UTC)

The bias-variance dilemma is a white spot on wikipedia's coverage of machine learning. :-( Should probably get around to fix it. EverGreg (talk) 12:05, 24 November 2008 (UTC)