Wikipedia:Reference desk/Archives/Science/2015 March 25

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March 25

Variable ginger sensitivity ?

I notice I am really sensitive to the spice, ginger. I don't have an allergic reaction or anything, it's just that the tiniest amounts make my food seem really hot. I don't seem to be any more sensitive to capsaicin than others, but that's known to have a variable response (or at least a resistance that builds up). Since I usually consume dried ginger, the active ingredient is shogaol, I believe. So, is there a variable "heat" response to this ingredient ? StuRat (talk) 06:12, 25 March 2015 (UTC)

Shogaol and capsaicin both bind predominantly to the TRPV1 receptor, which gives you the 'heat' effect, so it's hard to explain why you would be more very sensitive to one, but not the other. Must be secondary binging to other receptors, or a different component in ginger. 131.251.254.154 (talk) 11:08, 25 March 2015 (UTC)

I didn't see anything jump at me from the literature, but this might be obscure and I didn't really look that hard. It is by no means sure that shogaol is the difference unless you test the pure compound. Even more generally, you should figure out first if you are a supertaster and whether a variety of compounds have stronger taste to you, in which case this one interaction may not be the point at which the pathway differs. Wnt (talk) 11:36, 25 March 2015 (UTC)

It's not impossible that you have an altered form of the TRPV1 or TRPA1 receptor, which binds shogaol with higher affinity than the more common allele. But the only way to tell for sure would be to sequence your genome, or at least the part that contains the genes for those receptors. It might be interesting to know whether any of your relatives have the same hypersensitivity. Looie496 (talk) 13:44, 25 March 2015 (UTC)

Stu could also do some quantitative experiments. Not by asking people "how hot/spicy is this to you" but by continual dilution until the ginger is undetectable, analogous to the scoville scale. Obviously this isn't a genetic test, but it could still detect if Stu or his clan is objectively more sensitive to ginger than the average population. SemanticMantis (talk) 14:52, 25 March 2015 (UTC)

I'd say any results of such an experiment are likely to be dubious. Notice that scoville scale is for detecting the relative pungency of the stimulus itself, not for assessing the sensitivity of individuals to the stimulus, and even in that case the number of confounding factors listed in just our article's review of the scale are significant and findings in this area are even harder to establish with empirical validity, given the reliance on subjective reporting by participants. In the case of establishing relative thresholds of sensitivity in individuals, you'd need to control for a huge number of factors, you'd have to have a significant number of participants, and even then the element of subjective assessment of qualia would remain a huge issue. Snow ^{let's rap} 15:42, 25 March 2015 (UTC)

Sure, it's not the most rigorous thing, and I wouldn't try to publish it. But if I tested 10 of my friends and found that one of them consistently could detect ginger in lower concentrations than the rest, I'd still find that interesting, and more compelling than "I think I have a high sensitivity to ginger". SemanticMantis (talk) 18:01, 25 March 2015 (UTC)

Maybe "more compelling" in the strictest technical sense, but both scenarios are well bellow the threshold to make even an idle assessment of veracity, imho. Snow ^{let's rap} 19:33, 25 March 2015 (UTC)

As long as it's a double-blind test using a control, then some people consistently being able to detect ginger at lower levels would seem to be good evidence for a variable detection threshold in the general population. Of course, that says nothing about the reason for the difference. StuRat (talk)

And just how are you going to conduct this as a double-blind (or even a single blind) procedure when the entire point is to assess your specific sensitivity relative to others, and you are aware of this fact? Are you sure you fully understand what that term means in relation to this kind of inquiry? Even putting the issue of the blinds aside, the methodology for perceptual studies that involve self-reports are more complex than you seem to think, especially when the individual involved knows what they are being tested for, is convinced of what they will perceive, and has a vested psychological interest in confirming that self-derived assumption. And your involvement is just the tip of the iceberg in the factors that are difficult/bordering-on-impossible to control here. As to the reason, if I can do so without insulting you, I'd like to suggest that the most likely explanation is that any difference in minimum perceptual threshold is in your head, at least in-so-far as it represents anything beyond normal human variation. Most anyone who's done work in testing any modality of perception will tell you that it's a fairly common thing for people to be convinced that they have a sense that is atypical or especially sensitive, only to have testing fail to verify it. Snow ^{let's rap} 05:30, 26 March 2015 (UTC)

The test would be very much like standard hearing frequency tests, where they play (or don't play) sounds at various frequencies, asking the person to click the button if they hear it. We've managed to figure out the range of human hearing with such tests, as well as to identify the range for individuals. So what's so different about this that would prevent getting comparable results ? In case it isn't obvious, what you don't do is say "now I've cut the amount of ginger in half, can you taste that ?". Instead you would have random concentrations in food samples, with code numbers on them that can later be used to correlate the results. As suggested, you would simply ask "Does this sample contain ginger or not ?". If a given person reported yes down to a certain concentration, then no below that, this is a fairly reliable indication that they can detect ginger above that level. If there's no single line below which they can't detect it and above which they can, then something has gone wrong with the experiment, such as the subject lying. StuRat (talk) 05:41, 27 March 2015 (UTC)

Stu, if you can't tolerate Ginger, you should probably stick with Mary Ann. μηδείς (talk) 17:09, 25 March 2015 (UTC)

Or maybe I should ask the Professor for the answer. I'm sure he can rig up some device, using coconut shells, to do the tests. :-) StuRat (talk) 19:01, 25 March 2015 (UTC)

I suspect the ratio of my reaction to ginger varies at different levels. So, I might be 10x as sensitive at low levels but normally sensitive at higher levels. I've been having meals at BD's Mongolian Barbeque, which has powdered ginger as one of the spices you can add. I started with one tiny spoonful. That was too strong, so I went to half a spoonful, also too strong. I am now down to just a few grains of ginger, and amazingly it still seems almost as hot, despite having maybe 1/20th as much ginger as before. (Or does heat perception just work like light perception, in that dropping the light level to half as many photons is barely detectable ?)

I suppose another possibility is that they just don't clean the grill very well between customers, so I'm getting the spices from the last customer's meal. I'll have to do some experiments at home. StuRat (talk) 19:08, 25 March 2015 (UTC)

Geoid: how far from the center of earth does gravity point?

What is the distribution of distances between the normals of the geoid and the earth's center of mass? NeonMerlin 08:06, 25 March 2015 (UTC)

The article Vertical deflection gives some brief detail. Dbfirs 08:23, 25 March 2015 (UTC)

What vacuums are the most approximate to the absolute vacuum?

What vacuums are the most approximate to the absolute vacuum, it is a liquid vacuum or gas vacuum?--85.141.234.140 (talk) 08:42, 25 March 2015 (UTC)

A vacuum is the absence of matter; I don't know what you mean by a gas vacuum or a liquid vacuum. You might find it useful to see the list of examples listed in the vacuum article. Deep space is generally much more empty than any artificial vacuum.--Shantavira|^{feed me} 09:22, 25 March 2015 (UTC)

Probably, a vacuum possible in all environments in which there is been pressure (dynamics pressure)!--83.237.201.198 (talk) 12:12, 25 March 2015 (UTC)

Are you asking about how we create near vacuums for scientific experiments? If so, vacuum pump discusses several different types. SemanticMantis (talk) 14:54, 25 March 2015 (UTC)

The closest thing I can think of to a "liquid vacuum" is cavitation/supercavitation, but that's not really a vacuum at all, just an absence of liquid, filled in with a gas, such as air or water vapor. StuRat (talk) 18:58, 25 March 2015 (UTC)

The Sprengel pump uses liquid mercury. Some Diffusion pumps might use liquids. Rmhermen (talk) 22:28, 25 March 2015 (UTC)

Medication d codes

I have seen an identification code for medications that begins with a 'd', but I cannot find any reference to what this code is called. As an example, Altoprev 20 mg has the code d00280. This is not the NDC code (which is 59630-628). Anyone have an idea what those 'd' codes are? 209.149.113.207 (talk) 12:15, 25 March 2015 (UTC)

It seems to be the drug id for Lovastatin (which is where Altoprev redirects to on wikipedia). See here: http://www.cdc.gov/nchs/data/nhhcs/2007NHHCSMedicationsSupplementalDrugInformation.pdf 196.213.35.146 (talk) 13:38, 25 March 2015 (UTC)

"Drug ID" is a vague term. NDC is a drug ID. RxNorm CUI is a drug ID. FDA ID is a drug ID. They are all different IDs. I'm still looking, and it appears the the IDs that are preceded by a 'd' are Multum codes. 209.149.113.207 (talk) 14:16, 25 March 2015 (UTC)

Social indicators of Asperger's syndrome

Is it absolutely necessary for someone with Asperger's syndrome to show some sort of deficiency in social interactions beyond what could easily be chalked up to personality quirks? If someone has that diagnosis, is it logical to assume that there are noticeable differences in the way they interact with others? Kurtis ^(talk) 16:53, 25 March 2015 (UTC)

If somebody is diagnosed with Asperger's syndrome, the only logical conclusion to draw is that they should talk to the professional, medically-licensed expert who diagnosed them. Different professionals may differ in their diagnostic opinions. Nimur (talk) 17:01, 25 March 2015 (UTC)

According to our article on the diagnosis of Asperger syndrome, which matches my understanding, it is absolutely necessary to have some sort of social interaction impairment in order for a diagnosis to be valid, according to both DSM-IV and ICD-10. (In DSM-5, Asperger syndrome no longer exists as a distinct entity.) Looie496 (talk) 18:51, 25 March 2015 (UTC)

Remember however you still need to consider what's considered am impairement of social interaction. "easily be chalked up to personality quirks" could cover a wide range of things. Nil Einne (talk) 01:40, 26 March 2015 (UTC)

What I was trying to say, and didn't manage to say very clearly, is that the standard psychiatry manuals list social impairment as mandatory for diagnosis. The way that any given psychiatrist uses the definition can vary. Looie496 (talk) 12:25, 26 March 2015 (UTC)

555 timer

hello, I just found out that apparently the upper resistor Ra (between Vcc and pin 7) must be at least twice the value of the lower resistor Rb (between pins 7 and 2/6) such that Rb < ⅓(Ra+Rb), i.e. Rb < ½Ra, otherwise it won't oscillate because the capacitor can't discharge to less than V=Vcc/(Ra+Rb)*Rb. In other words, Rb should pull to pin 7 stronger than the sum of Ra+Rb pulls to Vcc. Is this correct? Three books and not one to say this explicitly in words Asmrulz (talk) 17:17, 25 March 2015 (UTC)

Our 555 timer IC article talks about lots of timing characteristics and technical discussion of them, but I don't see your analysis noted there either. With WP:V, it should be added. DMacks (talk) 19:11, 25 March 2015 (UTC)

Some of the 555 timers is described in Ulrich Tietze; Christoph Schenk (1993), Halbleiter-Schaltungstechnik (in German) (10. ed.), Springer, pp. 190–191, ISBN 3-540-56184-6, but that is written in German language. The article uses more weblinks than usual and links to data sheets so cover such details or provide such information from different authors. pending on the manufacturer you will find 555 timers with stronger outputs. Basics of the 3 resistors inside the 555 are their precise hysteresis, called window comparator, an used but never described word in the Wikipedia. This make the 555 change it's operation when the input voltage reaches 1/3 or 2/3 of VCC. The resistors needs to be selected by the wanted timing behavior and duty cycle or pulse duration when the 555 is used as a monoflop. This resistors need less ohms to make the circuit reliable under infuence and as many ohms as possible to save energy and not kill the transistors inside the 555. Then using a smaller capaitor, the same timing is being achieved with higher resistors. As the transistors inside the 555 are no ideal components that differ from a theoretical supra conducting switch. The external resistors need to be varible to use the 555 in different applications. The internal resistors are built-in to prevent a different temperature causing to shift the 1/3 ratio of VCC each where the 555 flips its status of operation. This is one of the essentials of the 555. --Hans Haase (有问题吗) 13:37, 28 March 2015 (UTC)

Standard 555 astable circuit

differential amp

I meant the two external resistors in the (most common) astable configuration. I was saying that if the upper resistor R₁ is too small (less than half of the value of the lower one R₂), then there'll be more than ⅓Vcc dropping across R2 and the capacitor won't be able to discharge enough to trigger a new cycle (when the 555 internally shorts pin 7 to ground, the capacitor essentially sees R₂ to ground and R₁ to Vcc), and that I wished (assuming this is correct) that some of the books (or WP for that matter) said explicitly that even though the resistors' values can be varied over a wide range to achieve a certain duty cycle and frequency, it must be ensured they have this ratio (R₁>½R₂) Asmrulz (talk) 20:11, 28 March 2015 (UTC)

The input pins 2 and 6 have very high impedance. Reading the circuit diagram, see them as volt meters. This are operational amplifiers, based on the differential amplifier, used as comparators. Do not calculate the base-emitter diode inside the transistor as a single diode, its current will be amplified by the collector-emitter-current of the transistor it the ratio of the transistors amplication factor. The common emitters of the differential amplifier add their output to rise the voltage to the common emitters resistor by the output current, following Kirchhoff's circuit laws and Ohm's law. This will also push back the base voltage of the inputs. This are basics of the differential amplifier. Refer the data sheet to know the impdance of these input pins.

Now operating the astable 555: See the discharge transistor (pin 7) as a switch. When turned off, see the external R1+R2 as one resistor, chargeing the capacitor. When turned on, it pulls the R1 from VCC to GND as a unneccessary load of battery or supply usage, but R1 limits the current of the discarge transistor and the capacitor is discharged via R2 also used as current limiter and part of the timing. --Hans Haase (有问题吗) 09:53, 29 March 2015 (UTC)