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Why Birds Don’t Get Cold Feet

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Re: Why Birds Don’t Get Cold Feet

#91

Post by pfdietz »

_Microft wrote: post #45
umvi wrote: post #12

Earlier quoted context omitted.

Can you list some examples of where this is used in engineering (software or otherwise)?

Check Wikipedia, the article has examples: https://en.wikipedia.org/wiki/Countercurrent_exchange

The page also talks about a variant, countercurrent multiplication. There's a really nice example of this in hydrogen isotope separation. The technique, called CECE (Combined Electrolysis Catalytic Exchange), was developed in Canada for production of heavy water and removal of tritium from heavy water.

The centerpiece of the system is a catalytic exchange column. In the column, liquid water flows down, while hydrogen gas (of various isotopes) flows up. At each point, a wet-proofed catalyst promotes the exchange of hydrogen atoms between the water and the gas. In equilibrium, protium partitions more into the gas phase than into the liquid, so as the gas goes up the tower the heavier isotopes are stripped into the liquid phase and carried back down. At the bottom, the water is fed into electrolysis cells to produce gas to feed back into the tower. Over time, the water in the cells becomes enriched in heavier isotopes and can be tapped off.

With this system, any H2 electrolysis plant could modified to also produce heavy water. This has troubling implications for nuclear proliferation in the coming "hydrogen economy", as heavy water reactors can be small and easy to hide, and have been used in the past for nations to enter the "Nuclear Club".

Re: Why Birds Don’t Get Cold Feet

#92

Post by bloodorange »

chrisseaton wrote: post #71
m463 wrote: post #57

Earlier quoted context omitted.

Wool socks are amazing. Warm and more importantly dry. In a similar way down comforters are wonderful (get the right weight).

Don't you find wool not stretching is a real problem? I struggle to get well-fitting wool socks that I can also get around my ankle, as they have no stretch. Did you know people used to use sock suspenders to keep their saggy wool socks up before we started to use synthetic fibres for socks?

It's not a problem if you find appropriate quality and thickness. One example is Icebreaker Ultralight socks. I use them in summer and they are rather thin.

Re: Why Birds Don’t Get Cold Feet

#93

Post by dorfsmay »

Retric wrote: post #17
umvi wrote: post #12

Earlier quoted context omitted.

Can you list some examples of where this is used in engineering (software or otherwise)?

Milk pasteurization is one of the best examples. You start with milk at 4C, heat it to ~70C via heat exchanger (+66C), then 75c via heating (+5C), wait 15 seconds for pasteurization, cool down to ~9C via heat exchanger (-66C), then just chill to 4C via refrigeration (-5C). This requires ~1/14th the energy to heat the milk and also rapidly cools it down below ambient temperature afterwards saving even more energy. You…

I had never heard of this, the use of already existing heat is amazing! Do they run 24/7? If not, they must use a lot of energy to cold start the process.

One classic example I always hear about efficient use of heat exchanger is the building of.swimming pool in the same building as ice rink. The heat produce cooling one is used to warm the other.

Re: Why Birds Don’t Get Cold Feet

#94

Post by mhb »

forgotmypw17 wrote: post #80
brnt wrote: post #47

Earlier quoted context omitted.

I used to never be cold. Could sit in open below 0C air after a shower without cooling down. I never really wore thick sweaters, where some would insist in them. Then I moved to a Mediterranean climate. When I go back now, I find I've become a wuss. Can't handle cold at all anymore.

I don't often choose what I wear, though I'd choose scratchy wool over most materials. I find that layering is a great strategy, and usually wear 3-5 layers in most weather conditions.

Who chooses what you wear?

Re: Why Birds Don’t Get Cold Feet

#95

Post by Causality1 »

soheil wrote: post #24
Causality1 wrote: post #5

Earlier quoted context omitted.

Exactly. I want to know what cellular metabolic tricks they use to keep their foot cells working at just over freezing temperatures.

What about a simple anti-freezing agent used in something like a car radiator? This doesn't seem like it should be such a mystery in the age of Google and Wikipedia. There are bacteria and other multicellular organisms that function just fine in extreme cold environments. See extremophiles, psychrophiles, etc.

Freezing is not the only threat. The functioning of cells depends on proteins that only work effectively within certain temperature ranges. Ectotherms tend to have multiple different pathways for a given process that cover several different temperature ranges while endotherms don't. So, do birds have that? Do their feet still grow, heal, fight infections when they're cold or do they depend on time spent with their feet warm?

Re: Why Birds Don’t Get Cold Feet

#96

Post by chrisseaton »

bloodorange wrote: post #92
chrisseaton wrote: post #71

Earlier quoted context omitted.

Don't you find wool not stretching is a real problem? I struggle to get well-fitting wool socks that I can also get around my ankle, as they have no stretch. Did you know people used to use sock suspenders to keep their saggy wool socks up before we started to use synthetic fibres for socks?

It's not a problem if you find appropriate quality and thickness. One example is Icebreaker Ultralight socks. I use them in summer and they are rather thin.

> One example is Icebreaker Ultralight socks.

The website says they're actually 38% polyamide and 2% elastane. I think they're 'wool mix' socks rather than wool socks.

Re: Why Birds Don’t Get Cold Feet

#97

Post by davidw »

ejolto wrote: post #88
chronogram wrote: post #79

Earlier quoted context omitted.

Always use cotton as a first layer, because you can just put it in the laundry. Cleaning my woollen coat is more difficult than changing a cotton shirt underneath it. Also: most “wool” is polyester because it’s like 10 times cheaper.

No don't, you're going to be in for a bad time if you wear cotton as a base layer in -10C weather. If you wear cotton socks and they get wet you might lose tour toes. Most wool is definitely not polyester. At least not in Scandinavia.

This is good - potentially even life saving - advice if we're talking about doing serious activities outdoors. And in that case, even wool is probably best replaced with synthetics that are lighter and dry quicker when wet.

For around town, though, a cotton base layer and wool works pretty well.

Re: Why Birds Don’t Get Cold Feet

#98

Post by alexilliamson »

forgotmypw17 wrote: post #33
goblin89 wrote: post #29

Earlier quoted context omitted.

Interesting. From my experience, coldness of feet is correlated with blood circulation. There are periods when my feet are cold (going together with the restless legs syndrome at night), and I think it goes away when circulation improves. My theory is that exposing feet to elements is another trick to improve blood flow to them, I’ve been meaning to try that.

If you don't have any snow to walk through, just give 'em an ice water dip. You can do your whole body, too, with similar benefits. It's uncomfortable, but what isn't... In my experience, and I've not found any studies to support this, restless legs correlates with oxygen levels vs carbon monoxide and/or carbon dioxide levels. Check your air.

+1 for ice baths. I used to do them regularly when I ran cross country. Invigorating.

Re: Why Birds Don’t Get Cold Feet

#99

Post by simongr3dal »

alien_ wrote: post #84
pfdietz wrote: post #70

Warm bloodedness (endothermy) would not be possible without countercurrent exchange in nasal passages. We have intricate bones there that capture heat and humidity in exhaled gas, then transfer it back to incoming air on the next breath. Without this the energy cost would be prohibitive. Structures like these in fossils are used as markers of the evolution of endothermy in ancestors of mammals and birds.

I'm not a biologist, but shouldn't this only matter in cold climate? If the climate is warm enough the animals actually would need to have ways to actively cool down, like through sweating. Would capturing heat from their expiration still be needed?

Wouldn't the mechanism work wether it's warm or cold relative to body temperature? The relative warmness of the breath could be captured on the way out and heat up incoming air, or it could capture the relative coolness of the breath on the way out and cool down incoming air.

Re: Why Birds Don’t Get Cold Feet

#100

Post by DoreenMichele »

Retric wrote: post #90
DoreenMichele wrote: post #38

Earlier quoted context omitted.

The only things I can readily find just reiterate what is in this article about heat exchange in the blood vessels: https://www.birdnote.org/listen/shows/why-birds-feet-dont-fr... https://en.wikipedia.org/wiki/Bird_feet_and_legs#Thermal_reg... One article I briefly looked at indicates there isn't as much study of avian ...something ....as mammalian. Maybe fattiness because I was wondering if they have any adipose tis…

I think you’re misunderstanding how essential and varied proteins are. In simple terms they are the nano machines which actively do stuff in cells. https://basicbiology.net/biology-101/molecules-of-life Essentially, DNA encodes Proteins which manipulate everything else. Human cells for example have on the order of 1 to 3 billion proteins, remove water and over half of what’s left is proteins. https://en.wikipedia.org…

Yeah, I'm well aware that DNA encodes proteins which, when deployed properly, become nano machines.

I have a genetic disorder that is essentially a salt-wasting condition. It also results in my body significantly misprocessing fats and oils.

So I know something about salt and about fats and about how those interrelate with biology and how those can weirdly impact things.

Beyond being aware of how those nano machines get broken when protein misfolds happen at the cellular level, I haven't taken much interest in the chemical properties of protein. It wasn't essential to my survival.

So someone else can look up the proteins of bird feet and go crazy with that if they care to. It's not my niche.

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