Wikipedia:Reference desk/Archives/Science/2008 January 13

= January 13 =

Help! I have woodlice in my house!
Every morning, when I wake up, there are woodlice all over the floors of the rooms in my house. A lot of woodlice. Possibly thousands. What's the best way to get rid of them completely? They're getting in my food, congregating in my bath (they're not coming up through the drain - I've checked) and getting on my mattress now and it's really beginning to piss me off.

I've tried putting down woodlice powder, which has killed quite a few (but not enough to make a dent in their numbers). I have filled in just about every crack, hole, nook and cranny I can find at floor level that I've seen them retreating into (but it doesn't seem to have stopped them getting in). I also go around with my vacuum cleaner, sucking up as many as I can before they skitter away, to very little effect.

Any DIY tips? I don't think that I'll be able to afford an exterminator. —Preceding unsigned comment added by 81.76.46.10 (talk) 00:32, 13 January 2008 (UTC)


 * Sorry, don't have an answer; just a remark on the things you learn from WP. I had expected something much more disgusting to answer to the name woodlouse -- who knew it's just a roly-poly. --Trovatore (talk) 03:58, 13 January 2008 (UTC)


 * I'd check out what the Broxtowe Borough Council has to say. In short -- you're doing the right thing by repairing all the cracks and holes in your home, but there must still be a source of moisture in your house.  If you've had similar problems in the past, like mold or rotting wood, then you probably need to buy a dehumidifier.  Wood lice don't cause much problems, but lots of little nasties like moisture, and soon you'll have to be prepared to shell out the cash for exterminators or home repairs. --M @ r ē ino 04:20, 13 January 2008 (UTC)
 * If you can dehumidify, the woodlice should die, as their gills need moisture (actually, that sounds like a less pleasant method of death than a bug spray). We get a few during the year in the basement, along with millipedes in the fall, which have the same physiological limitation. However, I agree with Mareino - if you've got these in quantity, I'd watch out for other problems related to excess moisture. J. Spencer (talk) 05:07, 13 January 2008 (UTC)


 * Sodium bicarbonate is also supposed to be effective. But you really need to deal with the dampness problem or find their nest(s).--Shantavira|feed me 10:16, 13 January 2008 (UTC)


 * Do you have partition walls? A friend of mine (with a damp flat) had woodlice living and breeding *inside* his PWs. The structure inside the wall was some sort of honeycombed cardboard - which the 'lice seemed to love. Check there. --Kurt Shaped Box (talk) 12:39, 13 January 2008 (UTC)


 * Maybe you could raise a family of Dysderidae. jeﬀjon (talk) 15:55, 14 January 2008 (UTC)


 * And then, maybe set up a colony of wrens. 79.66.24.40 (talk) 23:30, 15 January 2008 (UTC) [[Image:Zaunkoenig alleinerziehend.jpg|thumb|See the dead spider]]


 * I knew an old lady who swallowed a cat. Imagine that, to swallow a cat! --Trovatore (talk) 00:09, 16 January 2008 (UTC)

Mercalli scale
what are the countries that is using mercalli scale for measuring earthquakes —Preceding unsigned comment added by 124.217.98.24 (talk) 05:08, 13 January 2008 (UTC)
 * Any country can use it. A lot of people seem to think that the difference between the Mercalli scale and the Richter scale is like the difference between the metric system and traditional Anglo-American measurements -- different scales to measure the same thing. It's not. The Mercalli scale measures the local intensity of an earthquake -- how much shaking is felt at a given place. The Richter scale, and other measures of magnitude, measure the total size of the temblor. These are two completely different things. --Trovatore (talk) 05:38, 13 January 2008 (UTC)


 * Seismologists now universally use the Moment magnitude scale. Only the press use the Richter scale now.--TreeSmiler (talk) 10:00, 13 January 2008 (UTC)
 * Well, but it's calibrated to agree with the Richter scale pretty closely in most situations, so that's a second-order issue. Probably the labs report moment magnitude and the press reports the same number and calls it "Richter" for familiarity to the public. --Trovatore (talk) 21:52, 13 January 2008 (UTC)

Methysergide
Methysergide is the N-alkyl derivative of Lysergamide or not? Please help. —Preceding unsigned comment added by Gcllau (talk • contribs) 05:12, 13 January 2008 (UTC)
 * We have pages about both Methysergide and Lysergamide. That latter page is actually about a whole family of related structures, so you can see what the differences are, what the features of your particular compound of interest are, etc. DMacks (talk) 16:38, 13 January 2008 (UTC)


 * Compare Ergine (lysergamide) with methysergide. You could say that methysergide is a substituted lysergamide (i.e. it carries the additional 1-methyl and Namide-(2-propan-1-ol) groups. —Preceding unsigned comment added by Cacycle (talk • contribs) 00:00, 14 January 2008 (UTC)

The problem is that whether the (2-propan-1-ol) is considered to come within the meaning of Alkyl (-CH3) derivative? Please help. Gcllau (talk) 13:55, 14 January 2008 (UTC)

molecular weight
What is the unit (ug??, etc) of the molecular weight? Gcllau (talk) 05:48, 13 January 2008 (UTC)


 * According to our article molecular weight, it is the unified atomic mass unit. DuncanHill (talk) 05:58, 13 January 2008 (UTC)
 * typically in grams/mole (g/mol) Furmanj (talk) 15:45, 13 January 2008 (UTC)
 * ...which, in biochemistry, often gets called a dalton (symbol: Da). The molecular weights of proteins, protein complexes, and other heavy structures are often expressed in units of kilodaltons (kDa, a thousand grams per mole) or megadaltons (MDa, a million grams per mole) for convenience. TenOfAllTrades(talk) 16:41, 13 January 2008 (UTC)


 * per the OUP Concise Science Dictionary, (1984, p. 54) the dalton or atomic mass unit is equal to 1.66033 x 10-27kg. DuncanHill (talk) 16:46, 13 January 2008 (UTC)

Obesity/popular culture
Cross-posting with Reference desk/Humanities

For some time I've been working on the obesity article. It contains a commonsense but entirely original research section on the place of obesity in popular culture. I cannot imagine there are no academic sources that deal with this question, but I have had great difficulty in finding the most suitable (and accessible) sources on this topic. Would anyone know of a source that deals with this reliably? JFW | T@lk  06:59, 13 January 2008 (UTC)
 * Hmm, maybe there's some interesting references Category:Obesity; Super Size Me is very popular, but culture not so much. --Ouro (blah blah) 07:36, 13 January 2008 (UTC)


 * This is also in the other place: ":For scholarly articles on obesity in popular culture see list at ." Still, I haven't read them. Julia Rossi (talk) 08:44, 13 January 2008 (UTC)


 * Guys, these are things I have already done. I was thinking more about a respected textbook or article in a social sciences journal. I am sure these things exist, but using Wikipedia as a self-reference is not really useful and the Google Scholar search turned out garbage. JFW | T@lk  10:29, 13 January 2008 (UTC)
 * I'm not sure what you are looking for. Possible starting point in the literature: Portrayals of Overweight and Obese Individuals on Commercial Television. --JWSchmidt (talk) 17:38, 13 January 2008 (UTC)

Does light stop at the surfaces it's reflected from?
I'm sure there's a sensible answer to this, but when a ball bounces straight back off a wall, its velocity is zero at the point at which it changes trajectory. Why isn't this true of photons reflected off a mirror?

Thanks Adambrowne666 (talk) 11:32, 13 January 2008 (UTC)


 * The reflected photon is not the same entity as the incident photon. One photon gets absorbed, then another one gets emitted. See Reflection (physics). At the moment of reflection, the photon doesn't exist at all, so it doesn't have a velocity. --Heron (talk) 12:06, 13 January 2008 (UTC)

Uh, weird - thanks Adambrowne666 (talk) 22:09, 13 January 2008 (UTC)


 * Weird indeed - this may help your understanding. hydnjo talk 01:35, 14 January 2008 (UTC)


 * I wondered if this might be a question that comes up periodically, like the one about infinitely stiff materials transmitting information faster than light. Thanks for your answers, which make sense in the way so much quantum stuff does - it feels like someone's fudging something somewhere - like nature is jury-rigging arbitrary fix-its to cover up problems it didn't think of when it started off, and hoping no one will notice because it's down at such a micro level... Adambrowne666 (talk) 10:34, 14 January 2008 (UTC)


 * We don't have an article on circlons. They're mentioned in the article and are a key component to that theory...so shouldn't we? --71.98.14.236 (talk) 17:43, 14 January 2008 (UTC)


 * We don't have that article because (to my knowledge) they are not an accepted physical explanation for the phenomenon (outside of that site; note its domain name). The standard theory describing such interactions is quantum electrodynamics.  --Tardis (talk) 17:53, 14 January 2008 (UTC)


 * Oh, thank you very much for the info! --71.98.14.236 (talk) 04:04, 15 January 2008 (UTC)

Precisely how do baleen whales exist during the many months they abstain from eating?
Many species of baleen whales spend part of the year feeding on krill etc in the rich polar waters, putting on multiple tons of blubber. They then spend many months away from this food source -- the grey whale migration is thousands of kms, the longest of any mammal. Other large animals that go without food for long periods of time (e.g. some bears) hibernate, so their body systems shut down to some extent. But these whales are mightily exerting themselves, swimming, and of course in many cases pregnant or lactating. How do whales do it? How does their digestive system switch from working on food to working on fat, so completely, for such a long time? And then back again, year after year for up to 100 years? If humans tried this sort of yoyo dieting we'd screw up our metabolism. What mechanisms kick in for cetaceans? —Preceding unsigned comment added by BrainyBabe (talk • contribs) 12:32, 13 January 2008 (UTC) Sorry I meant to sign that. BrainyBabe (talk) 12:33, 13 January 2008 (UTC)


 * Yo-yo dieting is key here. For the whales the feeding is not necessarily followed by abstaining. The sequences are part of a cycle with a long trajectory built in. For humans who feed largely in a frequent browsing/grazing way, to mess with the cycle in a polarising, all-or-nothing way puts stress on the system. If a whale were to miss out on one of those shrimp feeds my guess is they'd be in big trouble. There's also an economy of input, output and sustainability level that maybe could be compared – somewhere. Julia Rossi (talk) 08:33, 14 January 2008 (UTC)

Microwave cooking
When cooking soup in a microwave oven, I've noticed that time taken to heat a given volume of soup depends on the shape of the container. I'm guessing the effect is caused by having a surface area exposed to the microwaves, but the heating times are the opposite of those you'd expect - a mug of soup (low surface area) heats very quickly, frequently boiling over before the 2 minute recommended time is up, while a shallow dish of soup, which has a much greater surface area, doesn't get above lukewarm unless heated continually for several (up to 5) minutes. So what causes this effect? Laïka 19:04, 13 January 2008 (UTC)
 * My first guess would be that the microwaves are horizontal. Therefore you need to consider the surface area of the 'walls'. 81.93.102.185 (talk) 20:21, 13 January 2008 (UTC)
 * To a first approximation, all of the microwave energy is absorbed in the water if you are using an acceptable container. In an uncovered shallow container, you lose more of that heat in evaporation before the water boils because of the much larger surface area. If you put a top on the shallow container, teh time should be about the same: for instance, put a saucer on top of the soup bowl-- faster and less wasteful than using plastic wrap. -Arch dude (talk) 21:18, 13 January 2008 (UTC)

tweaking a pellet fired boiler
I was nice and toasty warm and happy thanks to my oil fired boiler and radiant heating system&mdash;until i found that it was using nine gallons (34 L) of heating oil per day. That rate of consumption is likely less than that of Al Gore's jet aircraft, but is probably more than my fair share of contribution to a few global problems we are having at the moment (not to mention just a tad bit expensive). We've now switched to burning wood pellets, after repairing an abandoned feed system (late '80s vintage?, no instruction manual or even a manufacturer's nameplate) and making a few plumbing and wiring adjustment which i'm sure helped to reduce fuel usage, i was able to raise the building temperature from 40 F (4.5 C) back to the toasty warm 68 F (20 C) using only 30 lbs (13.6 kg) of pellets while the outside temperature averaged 20 F (6.7 C).

This was seemingly a spectacular gain in efficiency, until i reconnected all the thermostats and allowed the system to run unsupervised (starting at toasty warm) during a fairly mild 24 hours&mdash;and burned up 160 lbs (73 kg) of pellets. The pellet manufacturer claims 8.6 MBtu per pound (4,115 kJ/kg), that's 1,376 MBtu (1,452 MJ) in a day, ten percent more than the 1,251 MB (1,320 MJ) the nasty old oil was inputting to the boiler.

I should have seen a healthy jump in efficiency, i reduced the heated area by around 25 percent and lowered the temperature of the water which gets pumped to the radiators, but did not. This leads me to believe that either we were in fact burning more oil than i thought (possible, it was all free, leftovers in a tank that needed emptying so it can be moved, i wasn't really paying attention until i had to buy it, and other excuses) or the pellet combustion is horribly out of kilter and needs some adjustment. A few temperature sensors and a computer to measure, control, and record boiler output, HVAC calculations, more and better insulation, and improved zoning etc. are all projects for this summer. Here's what i can control right now for a more economical and earth friendly remainder of the winter:


 * firing rate The boiler is rated at 585 MBtu (617 MJ) per hour, the oil burner was supplying 556 MBtu (587 MJ) an hour, and with a duty cycle of about five minutes of firing and around eight not (very approximate, again i wasn't paying attention) was maintaining the water temperature between 202 and 208 F (95–98 C). When the auger on the pellet system is turning, it meters fuel at a constant rate of 44 lbs (20 kg) an hour, but is connected to a repeat cycle timer to control feed rate. The electro-mechanical timer that was present on the system was set for 12 minutes of on time and either 30 or 42 minutes of off time, since the mechanical part no longer ticks i can't tell which. The replacement timer was designed to be adjustable from 0 to 30 minutes of on time and 0 to 60 minutes of off time, but in actual operation has a maximum on time of one minute. With a few more rolls of solder from RadioShack i might be able fix this problem, but would prefer not to mess with the limited success i've had so far. It is now set for 1 minute on and 2.5 minutes off for a firing rate of 108 MBtu (114 MJ) per hour and with a boiler heating cycle of around 30 minutes on and 20 off (varies much more than when burning oil) maintains the boiler's water temperature between 160 and 166 F (71–74 C).


 * forced air supply and draft The pellet feed system has a blower with a single speed motor which delivers air to the burn pot. It was wired in such a way that it only operated while the pellet auger was turning, and the intake was completely closed off providing very little air. That didn't look quite right, during the on time the pellets would burn with a weak orange flame and during the off time would smoulder and produce black smoke. Pellets would overflow the burn pot and make a mess. I rewired so that the blower would provide continuous air during the boiler heating cycle, and by loosening a screw and shoving a wedge under a cover plate i have some fine-grained control over the air supply. There is now a nice bright yellow flame around the edges of the burn pot, bright red glowing pellets, and a nice jet engine sound when the boiler door is open. I've been able to find a bunch of information on how to get maximum efficiency from an oil fired boiler with natural draft&mdash;measure flue temperatures and CO2 percent and adjust the draft accordingly. I have no way handy of measuring these values, and have no idea what they should be when using forced draft and burning pellets. When the oil burner was operating i could place the palm of one hand against the flue near the exit from the boiler for only a few seconds. With pellets the flue is barely warm at the beginning of a cycle, and near the end i can hold my hand at the exit for around 20 seconds.


 * boiler water temperature i've lowered this from a maximum of 208 F (98 C) to 166 F (74 C). I think lowering this temperature should only improve efficiency, and it should be set as low as possible&mdash;too low and it will take too long to heat up the building in the morning&mdash;too high and the boiler room and crawlspaces with distribution lines get warmer than they should.

Any ideas on how to adjust the system for more efficient combustion? If you have a pellet stove, what color is the flame? Is there any smoke? Don't worry about any of the safety aspects of this question. It's a boiler, but only produces hot water and not steam, there's a functioning pressure relief valve and a thermostat to prevent explosions. Too much forced air and not enough draft would force hot gasses through the pellet feed system and eventually ignite the hopper, but the fire department is less than a block away, the chief lives next door, i'm a member, and a hopper fire would make a big mess but would not spread to the rest of the building anyway.&mdash;eric 22:04, 13 January 2008 (UTC)

Subatomic particles
Here is a question: does an electron love a proton, or does it love a neutron? Neon Merlin  22:38, 13 January 2008 (UTC)


 * Electrons love protons, and barely notice that neutrons exist. However, protons can only accept so much love. Someguy1221 (talk) 22:42, 13 January 2008 (UTC)


 * WOW! I wish my prof explained it that way! ;-)  hydnjo talk 23:41, 13 January 2008 (UTC)


 * Yes, and when electrons get excited, they ejaculate photons! Ironic though that the less excited they are the closer they are to their lovers.  Or is it?  Root4(one) 04:26, 16 January 2008 (UTC)


 * And now I don't want to know what electron capture or neutron decomposition would be... Someguy1221 (talk) 04:38, 16 January 2008 (UTC)