There is a compound in garlic called allyl methyl sulfide (AMS). It is a gas which gets absorbed into the blood when you are digesting the garlic (and onions and shallots). From the blood it is transferred to the lungs where it is then exhaled. A big part of flavor reception is through the nose so you get that lingering taste that way. Some of the AMS compound is also released through the skin.
Tuesday, 29 March 2016
ELI5: Why do flavors like garlic and onion stick around in the taste buds so much longer than others?
ELI5:How come people can't be cryogenically frozen safely as the ice crystals destroy the cell membranes, but sex cells such as sperm are kept frozen for long periods of time yet remain functional?
I work in a lab where we freeze down cells all of the time. We freeze our cells in a medium that contains 5% DMSO, which among other things can be used as a cryoprotectant. However, DMSO is also toxic to cells at the concentrations necessary for cryoprotection. Consequently, when you freeze cells in DMSO, you add the DMSO medium at ice-cold temperatures and don’t allow the cells to warm up. When you later thaw the cells, you have to dilute out the DMSO as quickly as possible without causing osmotic shock, which can pop the cells. Such restrictions on freezing and thawing would basically be impossible to control at the level of a complete organism.
However, to contradict a lot of previous posts, individual cells can be recovered from freezing with high viability. When performed properly (and this varies quite a bit by cell type), you can expect >90% of cells to be alive following thaw.
The chemicals that allow cells to survive freezing are toxic to the body. Keeping the cells cold minimized the damage that this chemical does to the cells. With single cell solutions, adding the chemical at ice-cold temperatures and immediately diluting it out when you thaw the cells can keep 90% of the cells alive. There’s no way to do this with an intact body.
It’s also worth noting that this is probably not the only reason that this technique doesn’t scale to organisms.
Wednesday, 23 March 2016
ELI5: Does a sonic boom only occur at the moment you break the sound barrier or is it constant and if it is does it get louder the faster you go?
It is constant.
A sonic boom is a shock wave that travels outward from the plane. It follows the plane wherever it goes. When the plane flies by a person on the ground, the shock wave will hit that person (and be heard as a “boom”) shortly after. Since the boom moves at the speed of sound, and the plane is moving faster than that, a cone shape develops, with the plane at the point of the cone. Here’s an example image.
As for speed vs. loudness, it’s actually the opposite of what you’d expect. The faster the plane, the skinnier and pointier the cone. As a result, the energy of the shock wave gets spread out over a longer distance. Additionally, super-fast aircraft tend to fly at much higher altitudes, meaning the boom travels through a lot more air before it reaches the ground, dissipating it. So sonic booms actually get quieter the faster the plane flies.
Saturday, 19 March 2016
ELI5: Why is charcoal so effective in fire places/pits/barbeque stands if the most of the wood/fuel has been used up?
Wood burns in two stages: the hydrogen stage and the carbon stage. In the hydrogen stage, hydrocarbon molecules are broken and oxidise. In the carbon stage, the carbon oxidises.
The carbon stage burning is a hotter and cleaner chemical reaction than hydrogen stage burning.
Charcoal is made by burning wood in the hydrogen stage (hence removing the hydrocarbons) but not allowing the carbon stage (by limiting the amount of oxygen).
ELI5: Why did old school TVs have a "layer" of static that sat on the screen? You could even "wipe it off" and it would be gone for a while then come back.
Old cathode ray tube (CRT) televisions have an electron gun which fires electrons at the back of the screen. And the screen is coated with phosphors which emit light whenever struck by an electron. The side-effect of this process is that each electron increases the static charge of the screen, and over time as the image on the TV changes it increases the charge. Meanwhile, rubbing your hand, which has a slight negative charge, across the screen will remove some of this built-up static.
Wednesday, 16 March 2016
ELI5: Why does having general anesthesia feel like you blink and you're in the recovery room when normal sleep feels like time passed?
No one really knows. Seriously we do not understand how it works. An anaesthetised unconscious state is not like sleep at all but more like a coma, though the exact details of what happens remain a mystery so far. Obviously the parts of the brain that are responsible for creating a sense of time having passed when we sleep are also prevented from working or prevented from recording it for a while.
Monday, 14 March 2016
ELI5: Why is it still so difficult to definitively determine the source of major rivers like the Nile and Yellow River?
Because hundreds of rivers merge to form these big rivers. So technically there are numerous sources. Which creek, drainage, stream or other water source is the river and which is just a feeder? Lot of options to debate there.
