Wikipedia:Reference desk/Archives/Science/2014 August 16

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August 16

Spider Gender

Is it possible to know whether a spider is male or female? I know that with many species, the female is larger, but with most species being solitary dwellers, there are usually no other spiders to compare them with. KägeTorä - (^影_虎) (Chin Wag) 03:34, 16 August 2014 (UTC)

It's going to vary by species. For some, perhaps many, only the females build webs. For some tarantulas, the males have some sort of little hooks on their forelegs which are used to hold the female in check during mating. (Talk about a "two-bag date", eh?) ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:51, 16 August 2014 (UTC)

I thought everybody knew that female spiders always have longer eyelashes; (I too, am educated from cartoons). 71.20.250.51 (talk) 18:14, 16 August 2014 (UTC)

Called "tertiary sexual characteristics" on TVTropes. -- BenRG (talk) 21:10, 16 August 2014 (UTC)

This page suggests looking at the pedipalps (along with coloration and size). -- BenRG (talk) 21:10, 16 August 2014 (UTC)

The males of some species have six legs, a mosquito-like proboscis and manage hotels. InedibleHulk (talk) 21:25, 16 August 2014 (UTC)

Spiders are feminine in the gendered languages with which I'm acquainted. —Tamfang (talk) 05:48, 17 August 2014 (UTC)

Molecular term symbols

How do you I translate a MO diagram into a molecular term symbol? How about using

as a teaching model? I understand the multiplicity number, I am most interested in the quantum number, but the remainder of the general formula is also important. Plasmic Physics (talk) 06:32, 16 August 2014 (UTC)

How does a Cross Vacuum Scale work?

A Cross Vacuum scale is a collection of 5 or 6 tubes with vacuum varying from a couple of torr to about .03torr. When a high voltage charge is placed across these tubes they glow, with different colours at different levels of vacuum. I would like to know why they glow and what voltage is required to excite these tubes.

Thanks for your help Rod — Preceding unsigned comment added by 110.175.51.176 (talk) 10:32, 16 August 2014 (UTC)

A Cross vacuum scale consists of 6 Geissler tubes (see article) with different vacuums to show their effects on electrical discharge.

From a seller's description:

tube no. 1 at 10 Torr pressure : ribbon line discharge

tube no. 2 at 5 Torr pressure : crimson band discharge

tube no. 3 at 1,25 Torr pressure : crimson coloured discharge

tube no. 4 at 0,75 Torr pressure : stratifications

tube no. 5 at 0,05 Torr pressure : grayish-white light

tube no. 6 at 0,025 Torr pressure : glows with brilliant green flourescence of glass

84.209.89.214 (talk) 11:05, 16 August 2014 (UTC)

Testing for alcohol in food

If you cook some dish using alcohol, how can you measure how much alcohol is left at the end? (I suppose there is a lot still, but I want to know how to test it empirically). OsmanRF34 (talk) 17:04, 16 August 2014 (UTC)

A hydrometer will allow testing of the liquid component, but presumably you're interested in the whole dish. Cooking with alcohol cites this paper, which anyone with a PubMed account can access - this doesn't include me, unfortunately. Tevildo (talk) 17:13, 16 August 2014 (UTC)

A hydrometer just measures density of the liquid component. That would be fine if one were to work with a solution of just water and ethanol, but breaks down if the mixture contains an appreciable amount of any other dissolved, suspended, or emulsified material which could quite significantly affect the density of the liquid.

The paper Tevildo linked noted rentention of anywhere between 4 and 85% of the original alcohol content, depending on cooking time, cooking temperature, and surface area of the cooking vessel. (Unsurprisingly, there was less alcohol retained during longer, hotter cooking in pans with larger surface area.) The method used was homogenization of the food sample and addition of water (to fully dissolve the alcohol), followed by centrifugation of the resulting slurry to remove solids. Gas-liquid chromatography was used to determine ethanol content, using the method described in Martin GE, Burggraff JM, Dyer RH, Buscemi PC. "Gas-liquid chromatographic determination of congeners in alcoholic products with confirmation by gas chromatography/ mass spectrometry." J Assoc Off Anal Chem. 1981; 64:186. I'm afraid I can't lay my hands on that paper, but Gas chromatography–mass spectrometry gives you an idea of the technique. TenOfAllTrades(talk) 19:14, 16 August 2014 (UTC)

Assuming you don't want to submit your dinner to a lab for testing, perhaps a home breathalyzer unit might give a rough indication of the amount of alcohol remaining. Take a bite of the food, then exhale into the device, and see what kind of a reading you get. Now it won't give you the percentage of alcohol in the food, but a higher number will mean there's more in the food. You could "calibrate" it by making a chart, with various test concentrations of alcohol in the food. Again, it wouldn't be highly accurate, but might be good enough to tell you if the kids should skip that meal or not. StuRat (talk) 01:24, 17 August 2014 (UTC)

Cordyceps

After playing the last of us Im just curious is it possible for the fungus to somehow evolve or adapt into infecting humans and if so would the results be like in the game or will people just start climbing buildings and wait to die like ants do — Preceding unsigned comment added by 86.44.92.8 (talk) 20:37, 16 August 2014 (UTC)

First, let's link The Last of Us. As for your question, well, I would say that nothing is impossible in biology. A science like physics, it is all about what can't be done. But biology is just a collection of things that happened. If you dream it, you can do it. But something like this is really, really unlikely without a whole lot of help, or a certain sort of luck. Wnt (talk) 22:03, 16 August 2014 (UTC)

A big diff is that ants do everything based on instinct, while humans have far more complex decision making processes. The advantage of instincts is that they require far less brain, but this also means they can be easily hijacked by activating just a few neurons. Changing human behavior in such a specific way would require a lot more than that. On the other hand, torqued up aggression or risk taking behavior can occur in humans as a result of diseases. StuRat (talk) 01:10, 17 August 2014 (UTC)

"A big diff is that ants do everything based on instinct, while humans have far more complex decision making processes." How do you know that? Can you prove it? ScienceApe (talk) 04:00, 17 August 2014 (UTC)

One fun way to show this is to lay down a circular scent trail for the ants to follow. They will happily follow the circle around and around, not noticing they are going in circles. Very reminiscent of the infinite loops a computer can get into. When you only have a very basic set of instructions to follow, this type of error can happen. StuRat (talk) 04:50, 18 August 2014 (UTC)

Mammals are highly resistant to systemic fungal infections. Mammalian body temperature is uncomfortably hot for fungi (it is even possible that a high body-temperature is partly an antifungal adaptation).

Also linking Cordyceps. There are a ton of parasites that control host behavior. Most of them don't use mammalian hosts. Here is a nice overview [1], and here is a very nice set of links to many more articles about parasite manipulation [2]. The plot for the game, while not necessarily biologically sound, is indeed informed by the many examples of parasites turning animals into "zombies". SemanticMantis (talk) 15:55, 18 August 2014 (UTC)

In general most fungi can not survive the elevated temperature of warm blooded species. Some theorize that this is the reason for warm blood in the first place. There are few that can, but they don't grow well. So it's unlikely that Cordyceps could infect a human, even an Immunocompromised one. Ariel. (talk) 18:27, 18 August 2014 (UTC)