Wikipedia:Reference desk/Archives/Science/2020 December 30

= December 30 =

Cryogenic freezer at Monterey aquarium
The Aquarium has kindly lent one of its two cryogenic freezers to a nearby hospital for storage of Covid vaccine, and it made a nice news story. Not answered is: why does an aquarium have something like that around anyway? The vaccine apparently must be stored at -94 degrees F, so the freezer has to be even colder than that, and in the photo it looks pretty big (it has to hold 1000s of vaccine vials). I'm sure the aquarium has a perfectly good use for the freezers but I can't help puzzling over what it might be.

Also, are there any serious technical challenges to building lots of such freezers out of parts on hand, as part of Operation Warp Speed? It seems strange that there should be a big shortage. It's just ordinary pumps and compressors at that temperature, right? No special magnetic whatevers like liquid helium temperatures would require. Thanks. 2601:648:8202:96B0:0:0:0:313A (talk) 04:50, 30 December 2020 (UTC)


 * As to the second question, see ULT freezer and Refrigerator for the requirements. It does seem like something that could be built largely "out of parts on hand", but if course you'd have to make sure that those parts were usable at the applicable temperatures, and you'd need a suitable low-temperature refrigerant.


 * The articles also indicate that such freezers are used to preserve biological samples, so if the aquarium is doing zoological research, that'd probably be why they had them. --174.95.161.129 (talk) 05:33, 30 December 2020 (UTC)


 * Storage of proteins & enzymes, cells, DNA and RNA, and a few other things works best at -70°C or lower, so materials the Monterey Bay Aquarium uses for research or veterinary care purposes probably require ultracold freezers. You probably can't cobble together a -70°C freezer out of a random assortment of pumps and compressors, though, since there are only a few manufacturers and ultracold freezers tend to run around $15,000 US for the most inexpensive models - I'd imagine if they were easy to build more manufacturers would do so and the price might be lower. Wevets (talk) 05:58, 30 December 2020 (UTC)

Thanks all. I didn't realize that an ULT freezer is different from a cryocooler. However, it sounds like ULT freezers are expensive mostly because they are specialized lab equipment: they are basically normal refrigerators with two compressor stages without any exotic materials. Ramping up production during this past year (say some tens of thousands of extra ones are needed) even at $15k each would be in the $100mm's somewhere, not that huge an amount in the overall Covid response. It was interesting to see that Stanford University had 2000 of these freezers in 2010. 2601:648:8202:96B0:0:0:0:313A (talk) 01:57, 31 December 2020 (UTC)


 * Great responses above. Just a quick note on availability of spare parts. It's certainly possible, but one of the issues is that most refrigeration systems are built to foodservice specs and they don't require anything near that temperature. Even ice cream, which is typically the lowest-temp food item, only requires -20F for commercial storage (and honestly 0F is more common). So, most "off the shelf" components are built to that standard. Even the specialized trucks ice cream manufacturers uses only get down to -20F (ref) and simply include more insulation and barriers to maintain the temperature. This limits the user-pool and the sheer numbers. Matt Deres (talk) 16:32, 1 January 2021 (UTC)

Healing from cuts ability
Gonna preface this with a statement that this isn’t a medical question, I don’t have any cuts or anything, I’m just wondering a couple of things. So, if you get cut your blood scabs over it then it heals, by growing new skin, and bigger cuts take longer right? Does this scale linearly over the whole body? Does it even scale locally? Say if I had a 2cm cut on my left hand would it heal faster than 2 1cm cuts one on either hand? Does the body prioritise healing beyond what areas have the most blood flow? Where can I read up on this? --86.172.59.180 (talk) 23:14, 30 December 2020 (UTC)
 * Wound healing: The larger the wound, the more work it takes to repair it, because the cells have to regenerate the whole area and join back together the wound margins. Larger wounds will usually entail more damage to structures like blood vessels, and those need to regrow as well. As far as I'm aware, the body doesn't "centrally control" wound healing anywhere. Cells migrate to the wound in response to inflammation, and the wound healing is regulated by local signalling between cells. --47.152.93.24 (talk) 03:06, 31 December 2020 (UTC)


 * Here's a paper describing constant speed traveling waves of cell propagation in response to wounding. It's an in vitro model, though. JoelleJay (talk) 19:46, 31 December 2020 (UTC)