Science desk
< April 14	<< Mar \| April \| May >>	April 16 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

April 15[edit]

DNA base needed for chicken pol III transcription start[edit]

The human RNA polymerase III requires a guanine at the transcription start position. Does the chicken RNA polymerase III also require a G at this position? I can't find information either way. ----Seans Potato Business 12:33, 15 April 2014 (UTC)[reply]

This paper "Usage of putative chicken U6 promoters for vector-based RNA interference" lists some sequences wherein the start base is G, so that suggests it might be necessary? ----Seans Potato Business 15:51, 15 April 2014 (UTC)[reply]

Smell against the wind[edit]

Can wild animals smell you, or at least detect your presence, against the wind? That mean the wind is blowing from the animal towards you. If we consider that the air is not laminar, I wonder whether my smell goes up and then gets down into the animal's nostril. OsmanRF34 (talk) 15:58, 15 April 2014 (UTC)[reply]

They often can't smell you in such cases. This can be bad for people, as they might run headlong into a bear which would normally have run away when it smelled the person. StuRat (talk)

Depending on the animal, it could detect a person via sight or sound...

Anyway, you're right that wind isn't usually laminar, but eddies and other forms of turbulence usually serve to disperse scents, rather than transport them. Serious hunters are very concerned with approaching game from downwind, see e.g. here [1]. That being said, some animals have a very sensitive sense of smell, so I think it would be hard to completely rule out close-range scent detection of downwind humans. For instance, on a rather still day, smell from strongly-scented human could conceivably diffuse upstream. I can't find a good WP source for the possiblity of upstream diffusion, best I can find is a cryptic mention at Central_differencing_scheme. So if anyone can comment or add refs on the physics/math of upstream diffusion, I'd appreciate it. SemanticMantis (talk) 21:15, 15 April 2014 (UTC)[reply]

Note that if the scent does diffuse or follow wind eddies to the animal, the scent will be weaker, and the animal will have more difficulty in determining the source, both because it's weaker and because the animal can't just use the wind direction to find it. In fact, if it tries to follow the wind direction, it will look the wrong way. StuRat (talk) 12:56, 17 April 2014 (UTC)[reply]

The animal can follow your trail (assuming he is following your trail) even if you are downwind. μηδείς (talk) 02:43, 16 April 2014 (UTC)[reply]

True, but that's from scent left on vegetation, not carried by the wind. Dbfirs 06:43, 16 April 2014 (UTC)[reply]

Yes, I guess I should have made that explicit, rather than assuming it was obvious. μηδείς (talk) 16:47, 16 April 2014 (UTC)[reply]

Taste distortion by toothpastes and mouthwashes[edit]

Why toothpastes and mouthwashes temporarily distort the taste perception and which component(s) does it? For example, after Listerine the water tastes metallic and orange juice acrid to me. 93.174.25.12 (talk) 19:48, 15 April 2014 (UTC)[reply]

In my experience, it is the interaction of a strong mint aftertaste with whatever it is that is being eaten after. - Eron^Talk 20:01, 15 April 2014 (UTC)[reply]

For toothpaste, see Toothpaste#Alteration_of_taste_perception. See also this external link [2]. Both agree that Sodium_dodecyl_sulfate is the culprit responsible for "orange juice tastes bad after brushing teeth". SemanticMantis (talk) 20:59, 15 April 2014 (UTC)[reply]

Note to self. Brush teeth, then eat some Synsepalum dulcificum then eat an orange, then a lemon, gargle with whatever. Repeat experiment in different orders.--Aspro (talk) 21:31, 15 April 2014 (UTC)[reply]

Awesome. I knew nothing about the wonderberry. Thanks for that link! ---Sluzzelin talk 21:38, 15 April 2014 (UTC)[reply]

Wonder berries are Solanum retroflexum. I mean these things [3]. They truly do appear to be in the realms of a miracle to my mind. Especially, as straight from the field they cost about the equivalent of US$ O.O5 a Kilo but in the US they suddenly cost over $49 per 20 berries. I bet there are many illegal drug dealers that would like that sort of mark up!!! The only business that tops that, is microsoft selling round discs consisting of a few cents worth of polycarbonate for loads of dollars and when these discs give you indigestion they demand loads more dollars to solve your (their) problem .--Aspro (talk) 22:48, 15 April 2014 (UTC)[reply]

Ooooo, I was translating from my native language (Wunderbeere). I can't wait to sample them, whenever that's going to happen. (I'll use those discs as coasters). ---Sluzzelin talk 23:11, 15 April 2014 (UTC)[reply]

You are probably talking about "miracle fruit" (Synsepalum dulcificum), not "wonderberry" Solanum retroflexum. Cacycle (talk) 12:34, 18 April 2014 (UTC)[reply]