10 years ago, Congress decided we needed to transition off of it. Large amounts of the stockpile were sold off from 2013-2018 and this is the final part of the plan.

https://www.blm.gov/programs/energy-and-minerals/helium/fede...

Transition off of it? Dont we need it for superconducting coolant and some other things?

Yes. MRI machines need it, although I guess that kind of falls into the superconductor category. But I call that use case out because it's probably a good idea to have the government, or some trusted caretaker, look after at least two strategic stockpiles.

FWIU Nuclear Fusion can use (and produce) 4He ('He4') as fuel.

I think it makes sense to retain our nation's helium reserves.

You are thinking of helium-3, of which there is none stored here.

It is very much harder to fuse helium-4.

I think it's both Helium-3 and Helium-4?

(Tritium (3H) decays into 3He with a 12 year half life. Before 12*n years, tritium is radioactive and denser than water and so it will pool and concentrate in ocean cavities for example at the seafloor. Tritium also probably has affinity for certain types of trash floating in the ocean, which Seabin and The Ocean Cleanup are addressing.)

Is laser-based nuclear transmutation of e.g. He4 into He3 easier with the high heat of a nuclear fusion reaction?

Helion's fusion process involves both He3 and He4: https://news.ycombinator.com/item?id=37403522

Thanks!

Heads up, the danger with charging LFP at low temperature is that you will begin lithium plating. While this is a driver of degradation of LFP batteries, it's also a safety risk as lithium plating can lead to dendrite formation, internal shorts, and thermal runaway (i.e. fire).

Contrary to popular belief, LFP is not immune to thermal runaway. While LFP batteries do release less heat than Nickel based cathode chemistries, they can still cause a building to burn down when you have 200Ah or more.

You drive current through the outer probes. The inner probes measure voltage and are not driven. When measuring non-zero resistance, you can vary the driving current to confirm the voltage you measure also varies linearly (ex thermal effects, capacitance of the material etc.). When measuring zero resistance, you can't distinguish vs a voltage probe error.

I know a dev fresh out of college who became proficient in COBOL, got a govt job offer, and now is working as a lifeguard because places that hire COBOL programmers take forever to process their paperwork. Presumably he'll start his real job in late summer when they get their act together.

You're in an enclosed tube with lots of people, so fire is a lot worse.

Most lithium ion battery fires in cabins are from loose vape batteries, probably shorting on keys or change.

Some are from crushing pouch cells in tablets or phones, sometimes by seats.

Besides that, there isn't anything about planes that is causing these fires.

I would imagine that the proliferation of cheap devices using lithium batteries also contributes to the issue somewhat. While anything with a lithium-ion battery is susceptible (as seen with the exploding Samsung Note debacle), bargain bin electronics are almost certainly not selecting batteries to as high of a standard as something with better profit margins, like an ultrabook or flagship phone.

Cheap chargers also likely contribute. There's limits to how much charger misbehavior even the best batteries can tolerate and some of the charger bricks sold on Amazon, in gas stations, etc are horrifyingly bad.

One contributor is that most batteries have a protective circuit built in. It usually has a DW01 chip and a pair of MOSFETs to prevent overcurrent charging, overvoltage, undervoltage, and overcurrent discharging, all for under a cent.

Since most batteries are protected, the cheapest chargers can be 'dumb', with a simple constant current output. When the battery is charged, the built in protection device will stop the charge when charged.

However, only most batteries have this protection. If you plug one of these cheap dumb chargers into a battery that doesn't have the protection circuit, then it will catch fire after a few hours.

The usual culprit is 'replacement' (non-OEM) batteries for an expensive device, for example a drill. The OEM version has a smart charger and a protected battery. A non-OEM battery lacks protection. A non-OEM charger is dumb. Either alone is safe. Combine them, and a fire happens. And because the device is expensive, the people in China who designed the battery and charger never had the original device to do proper testing with.

There really need to be rules in place to prevent these ticking time bombs that are cheap devices with 0 safety considerations or QA from being brought onto planes.

Yes, cheap devices are real problem. China has strict rules for transporting batteries that are actually enforced.

Also no lighters on plane, because they know in practice they will be used in lavatories. They will find a lighter, or even just a spring from a lighter that fell apart a long time ago. Beijing airport security is quite impressive actually. They probably won't notice the knife you accidentally left your bag, however.

NaCl isn't bonded in water, it's ionized and dissolved. Each ion (Na+ or Cl-) is surrounded by a large number of water molecules due to the electric field of the ion.

That's not completely helping me visualize why it doesn't pass through the membrane. Are you saying that each water molecule surrounded (Na or Cl) ion stays intact as a group, and is too collectively too large to pass?

The water molecules aren't chemically bonded to the ions, but they are "bonded" by intermolecular forces. Although weaker than a chemical (intramolecular) bond, the intermolecular forces are still strong enough to "bond" water molecules to the ion. So either only water molecules not "bonded" to ions can pass through these channels, or the pressure differential across the channel can free the water molecules from the ions.

It's not quite a pressure differential, but a chemical potential differential (but thinking of it as a 'pressure' gives a useful mental model).

It’s force per area so it’s definitely a pressure, the difference is just that the driving mechanism is chemical potential instead of a difference in number of particles.

Tough a system put into contact with a resevoir of a constant concentration should try to increase in volume until the concentrations on both sides are equal.

It's probably the 'constant concentration' part that is confounding the two. It is connecting number of particles with volume, whereas the canonical ensemble has them as separate terms.

Yes, that would be a membrane. There a number of membranes with larger pores that are fabricated like above, but out of polycarbonate (track etch membranes).

Some people have also experimented with single and double layers of graphene with a few very small pores. Because they are so thin, you don't need as much porosity for high transport rates.

You still have fouling issues, though.

You can declare a type-hint beforehand without setting the value of the variable. See: https://peps.python.org/pep-0526/#global-and-local-variable-...

Yes, but then those variables are not visible when we dir(object), which makes it harder for the user to prototype. Certainly, type hinting should not get in the way of the users.

The title says this is expanded PTFE, which seems like it wouldn't need an additional PFOTS coating. I doubt it would shed similar small molecules to a PFOTS coating as it's a different material (polymerized tetrafluoroethylene).

I also doubt you would get similar endocrine disruption with PTFE polymerization biproducts since you won't have the "polar head/fluorinated tail" structure that PFOTS has.

Lithium Ion batteries do burn much more readily when fully charged than when discharged -- this is because they self-discharge rapidly at elevated temperatures, which provokes an even greater reaction of the materials inside of them. Specifically, if the cathode of NMC/NCA batteries gets hot enough, it will decompose into oxygen and really kick off the graphite + electrolye burning. Discharged batteries are tougher to get to burn since it's harder to heat the cathode to that point externally so oxygen has to come from the environment.