Wikipedia:Reference desk/Archives/Science/2019 November 18

= November 18 =

Cytotoxic CD4 T cells
I looked at the abstract of this and can't make head or tail of it, even after looking at our article Cytotoxic T cell. Is the implication that very old people's cells change to make them more likely to get autoimmune disorders? Or that they have somehow already gotten autoimmune disorders that cause them to develop these cells? Or what? Thanks. 67.164.113.165 (talk) 07:13, 18 November 2019 (UTC)


 * Nothing about autoimmune disorders is implied. In fact, the authors explicitly have no idea what these CD4 CTLs are programmed to do. The main finding is simply that these cells (previously reported as very rare in healthy individuals) are found in very high numbers in healthy supercentenarians. They also show that these cell populations are stable over time, and to the extent testable, the cells appear to be functional cytotoxic cells, meaning that they can probably kill their target cells, whatever those are. Someguy1221 (talk) 07:46, 18 November 2019 (UTC)
 * Cytotoxic T cell does not mention cytotoxic CD4 T cells, which is a pity. Ruslik_ Zero 20:54, 18 November 2019 (UTC)
 * This explains a little more. Thanks. 173.228.123.207 (talk) 09:00, 21 November 2019 (UTC)

Water level in a filtering pitcher
I noticed that the water in my Brita filtering pitcher doesn't flow downwards until the end - there's always some water remaining in the funnel above the filter, after the rest is filtered down. Is it because of insufficient pressure to push through the filter or something else? 212.180.235.46 (talk) 19:33, 18 November 2019 (UTC)


 * I suspect that eventually the levels would equal out, but the tiny amount of (over)pressure exerted by the water on top isn't enough to quickly force the water through the filter. Try leaving it alone for days, and see if it doesn't even out. (Be sure to cover the top, so evaporation doesn't become a factor.) SinisterLefty (talk) 19:38, 18 November 2019 (UTC)
 * Sorry, put it wrong a bit: the water that doesn't seep through is stuck at the bottom of the funnel below the filter. Flushing it out and filling again doesn't help, as the issue persists. 212.180.235.46 (talk) 22:59, 18 November 2019 (UTC)


 * Sounds like the filter paper produces a Capillary effect on a small remaining rest of water. --Kharon (talk) 05:06, 19 November 2019 (UTC)


 * It sounds like capillary action is holding it back butI can't see the difference between the water that has filtered down into the lower chamber and a small amount left in the filter chamber. I mean, the filter is not toxic and that water will be flushed down when you next fill the pitcher - ?later in the day or the next day. Richard Avery (talk) 22:43, 20 November 2019 (UTC)