!!
Or, you can also use WinCompose (or Xcompose for X Windows users. For tty users, tough luck). At least, on my installation, it can be typed as "Compose Compose d e g f".
My assumption is the skeleton, marrow and body fat (or some other body structure with high thermal mass) act as a heatsink that expels some built up heat.
cartelige is a permeable material for various occupants, oxigen being one.
So we find that highly oxigenated creatures are larger and more carnivorous
we also know that high ingestion of oxygen results in larger creatures
so if a shark has a larger ability to permeate oxygen into the muscles and have the ability to store heat, plus the ability to transfer heat/oxy btwn bodies...
This is why we can see a body +500 years old..
buoyed by the buoyancy of less dense bones, such as cartilage.
> It is known for its ability to maintain stomach temperature (homeothermy), which is unusual among fish. This shark has not been demonstrated to maintain a constant body temperature.
https://en.wikipedia.org/wiki/Salmon_shark
But there is indeed a vascular heat exchanger involved:
The shark can raise its body temperature 14-20 degrees more than the environment. I think it fits the definition of warm blooded.
I used to be able to do homethermy by thought when I was younger... but I have lost the ability.
(SERIOUS); I used to be able to direct heat to various extremities by thought when I was laying in bed in really cold environs... but I seem to have lost that ability.
I was under the impression that bird lungs do have continuous flow.
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2681264/#:~:tex....
When we inhale cold air, these structures warm it, and thus become colder.
When we exhale hot air, it heats these structures, making them warmer again, to allow heating the next breath in.
It's of course not 100% efficient, but it's better than nothing. I wonder uf there are more advanced strictures, like circulating liquid, to improve efficiency.
How so? When you breathe in, your nose tissues will cool down to a temperature T_N and the air you inhale will heat up to a temperature T_A. Physics (the second law of thermodynamics) dictates that T_N >= T_A.
Moreover, the nose tissues are connected to a large heat reservoir (the body), so we might as well assume they go back up to body temperature very quickly, so T_N = 37°C after a second or two.
Either way, when you breathe out you still have T_N >= T_A. In this situation, there is no way the air could transfer back heat to the nose without a violation of the second law or, well, a heat pump. Hence my question.
When breathing in, the air is gradually heated by the nasal passages. The temperature in the nasal passages increases along the channel, so at all points there's a small temperature drop, minimizing production of entropy.
When breathing out, the air is cooled in the same way. Again, there's a small temperature drop (now of the opposite sign) along the channel, again minimizing entropy production.
Moisture is also conserved here in a similar way.
Countercurrent heat exchange is also used in biology to minimize heat loss in extremities. The arteries of your arm, and the deep vein returning blood there, are wrapped around each other to transfer heat. In some vertebrates elaborate artery/vein structures have evolved to make this more effective.
https://en.wikipedia.org/wiki/Rete_mirabile
Countercurrent exchange is a fundamental engineering concept I feel more people should know about.
I do find it remarkable, though, that the nasal turbinates don't seem to thermalize with the rest of the body in the time between inhale and exhale (which is of the order of several seconds). Or maybe it does thermalize quite a bit (even though not fully): A quick search for "nasal turbinates countercurrent heat exchange" reveals that human nasal turbinates are not particularly great heat exchangers, with air exiting at temperatures of up to 33°C during exhales.