Wikipedia:Reference desk/Archives/Science/2014 September 7

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September 7

Water depth east of Gorham's Cave, Gibraltar.

According to the article Gorham's Cave,

"Gorham's Cave is a natural sea cave in the British Overseas Territory of Gibraltar, considered to be one of the last known habitations of the Neanderthals in Europe. It is located on the southeastern face of the Rock of Gibraltar. When first inhabited, it would have been approximately five kilometres from the shore but, due to changes in sea level, it is now only a few meters from the Mediterranean Sea."

The part of this statement about the distance from cave mouth to water's edge seems surprising to me. I tried to find the depth contours of the water east of Gibraltar, via internet and my local library, so far without success. No reply to my question on the article's Talk page.

I'm trying to find out how far below the present sea level the water would have been if the shoreline was 5 kilometres from the cave, and also how long ago the water level of the Mediterranean Sea was that low. Can anyone here shed any light on this? Thanks, CBHA (talk) 02:40, 7 September 2014 (UTC)

Sea level during the peak of the last ice age, 20 thousand years ago, was about 120 meters lower than today, mostly due to water trapped in large ice sheets over land in the Northern Hemisphere. Dragons flight (talk) 03:05, 7 September 2014 (UTC)

You might also want to read about the geological prehistory of the Mediterranean, particularly the hypothesized Zanclean flood. Opinions vary among geologists about the timing and magnitude of that event, if it even occurred. Nimur (talk) 09:42, 7 September 2014 (UTC)

Question regarding Riboflavin

I'm asking a question about the Riboflavin (which generates light beams). The chemicals with flourescence colors such as the traditional chartreuse, laser lemon and others are frequently used to create lightening in certain rooms that would blend through out the wall and floor backgrounds. I wonder if that yellow beaker next to the clear one has chartreuse coloring or if it's green. I know there is a chartreuse that is green and one fluorescent.--HappyLogolover2011 (talk) 05:50, 7 September 2014 (UTC)

Not really a full answer, but see riboflavin and fluorescence. The "yellow beaker next to the clear one" that the OP refers to is File:RiboflavinSolution.jpg Tevildo (talk) 08:56, 7 September 2014 (UTC)

One concern as I'm reading the question is that it seems to confuse the idea of "color" (hue, such as green, yellow, etc) with optical behaviors (fluorescence and other visible effects of light beams, etc.). Chartreuse (color) covers various possibilities from mostly to mostly green to a greenish-yellow, and seems to reach to the color I perceive for the riboflavin solution in the right-hand beaker. File:Riboflavinspectra.jpg is the exact color profile of the fluorescence of riboflavin; you can compare it to Chartreuse_(color)#Wrapping the spectrum into a color wheel to see where its dominant emission range falls on the visible range of colors. DMacks (talk) 16:37, 8 September 2014 (UTC)

How do you shame someone scientifically?

Suppose you have some kind of MRI device and you want to observe the working of a human mind during an emotion of shame. But the MRI machine is so big that you have to bring your subject to it. Now how do you shame your subject scientifically while the subject is attached to the MRI device. I mean, if the subject knows that this is all a science experiment, how can the subject feel shameful at all? 220.239.43.253 (talk) 12:40, 7 September 2014 (UTC)

First you start by defining your terms! If you read any reputable description of such an experiment, they begin by describing their model for emotional state. For example, here's a paper selected at random from the NIH's biotechnical literature collection: The Neurophysiological Bases of Emotion: An fMRI Study of the Affective Circumplex Using Emotion-Denoting Words (2009). First they define human emotion, for the purposes of this study, using a model that was first published by some psychologist in 1980. Next, they run control studies with an fMRI machine, with and without exposing the test subject to spoken words that "induce emotion." There's thirty-five years of published research on how to induce emotions using that specific model first published in 1980. We could select another experiment at random, and they'll likely have a different model with a different definition of terms and different set of historical experiments.

...And that's pretty much it. In science, when there's some vague concept like "emotion" that we want to study, we do a literature survey to determine how terms have been defined in the past. We select a reasonable model that fits our needs. We conduct controlled experiments. Easy!

The biggest advantage that an actual scientist who specializes in this area would have is experience: they'd already be subject-matter experts and they'd be familiar with several of the most famous prior works; they'd know the subtleties and the advantages of choosing any particular model; they'd be familiar with the long history of other experiments that used that model. They'd quickly identify how reputable a previous publication is. To get that kind of context, we'd have to spend hours or days or weeks or years doing literature survey to become familiar with the state of the art methods!

In some sense, this is contrary to the popular notion of scientific consensus. Not all scientists automatically agree on the correct definition of a vague term like "emotional state." Heck, we have scientists who disagree on the definition of far more concrete terms, like "mass" or "dimension"! Real scientists don't actually need to agree as long as they define what they mean, cite their sources, and make claims consistent with repeatable experiments.

So: what you want is a literature review or summary paper that will bring you up to speed on all the various techniques that are popular for inducing emotion among fMRI researchers today. Then you can dive deeper into your favorite model for more details about how it works.

Here's one such review: Functional Neuroanatomy of Emotion: A Meta-Analysis of Emotion Activation Studies in PET and fMRI, a 2002 meta-analysis of emotion-inducing techniques. The authors explain more than fifty other research publications, broadly lumping the emotion induction method into three categories (visual, auditory, and recall).

Nimur (talk) 16:14, 7 September 2014 (UTC)

If the experimenter's purpose is to explore shame as one of the 9 "affects" in emotional Affect theory, the experiment could be conducted by stimulating a range of different emotions in order to identify the brain activity that correlates (in the theory) with the specific physiological expression (i.e. eyes lowered, the head down and averted, blushing) associated with shame. It is normal procedure for subjects to be alone in the MRI scanner room (for safety close to powerful magnets); if that is their expectation they will not be prepared for whomever the experimenter may bring into the room during the scan, which offers opportunities to stimulate emotions, e.g. shame could be stimulated by a barrage of verbal accusations from persons close to the subject. See the article about Shame. 84.209.89.214 (talk) 21:53, 7 September 2014 (UTC)

I thought the answer to the question would be something like:  "Not only are you wrong, your maladroit precept defies canonical normal form."  — Preceding irresolute comment added by 71.20.250.51 (talk) 23:02, 7 September 2014 (UTC)

You could give them a verbal test on some subject they don't know well, then list all their wrong answers, perhaps having a little kid recite the correct answer for each. That should get an embarrassment/shame response in many. StuRat (talk) 19:41, 8 September 2014 (UTC)

Sounds like a plan to me. Of course one would have to pass any test that induced shame past an ethics panel. One I can think of is to have somebody lying down looking ill and dying near the entrance entreating them for help and seeing if they don't try and help them. Inside they can be told off hand just before the bit to measure shame that some poor person has just died of a heart attack near the entrance isn't it awful. On the other hand just asking people to try and remember vividly an occasion on which they felt shame would probably be just as good. Dmcq (talk) 20:48, 8 September 2014 (UTC)

Technically, shame's to do with "consciousness of foolish or wrong behavior." While StuRat's idea's good, and unlikely to cause an Institutional Review Board to harrumph, it might not be as effective or quick as a variation on the visually evoked potential study. The idea would be a succession of images likely to trigger consciousness of "wrongness" - soft-core nude photos, bacon sandwiches or baked ham (for the roughly 1/6 of the world population who are religiously forbidden to consume pork), photos of people in mildly kinky clothing... validation of the imagery might be a project in itself, a "pre-scan" to identify which images reliably evoked responses of "shame." Now, getting that past an IRB might be trickier, but it's all for science, right? loupgarous (talk) 15:26, 9 September 2014 (UTC)

Chemical lasers and expendability

I heard that chemical lasers can't fire "indefinitely". Meaning that the gas has to be replaced at a certain point. But I was under the impression that in order to generate a laser all you have to do is shine a light on a lasing material, in this case the gas. Shouldn't it work indefinitely as long as you have electricity powering the light? ScienceApe (talk) 17:20, 7 September 2014 (UTC)

Most chemical lasers utilize a chemical reaction which is not in equilibrium, meaning the reaction becomes degraded as the reactants are consumed. An exception seems to be a self-contained re-circulating chemical lasers (cf. source from our article).  —71.20.250.51 (talk) 18:02, 7 September 2014 (UTC)

There are different ways of powering ("pumping") the lasing medium in a laser. The most common method, used in diode lasers, is directly running en electric current through the medium. Another common method, which you are thinking of, is optical pumping, in which a light of higher frequency shines on the lasing medium. Light for optical pumping can come from another laser, or from a lamp such as an arc lamp or flashlamp. Chemical lasers are different: they use a chemical reaction in the lasing medium to provide the pumping, rather than an external energy source. The chemical reactants are consumed by the reaction and have to be replaced. --Srleffler (talk) 18:35, 7 September 2014 (UTC)