I much prefer tests with low false positive rates.
I recently had such a cancer-related test. A cousin had a BRCA2 mutation and I was concerned I could have it also. Insurance would not pay for the testing, but one can get a panel of such genetic tests for just $250 now, so I went ahead. And it was negative. This is reassuring not just to me, but also to my children, and (somewhat) my sibling (the relevant parent is no longer alive).
Had this test been positive, the chance of pancreatic cancer would have gone way up, so frequent scans (I think annual MRI and ultrasound?) would have been justified.
Insurance-based medical systems mean the patient has transferred responsibility for saying no to those actually paying the bills. They have to draw the line somewhere.
There's excellent reason to think LNT is accurate: at low doses, almost every cell is exposed to at most one radiation event. The dose affects how many cells experience a (single) event, but does not affect the level of damage to those exposed cells. Linearity naturally falls out of this.
To abandon linearity you have to imagine some sort of signalling system (not observed) that kicks in at just the dose we're talking about (not lower, not higher) to allow exposure to one cell to affect other cells.
There's also no good evidence that LNT is wrong. The typical things that are pointed to by anti-LNT cranks are cherrypicked, often involving interim results from studies the full results from which do support LNT, which is evidence it was statistical noise.
"Nitrogen isotope fractionation (ε15N) in sedimentary rocks has provided evidence for biological nitrogen fixation, and thus primary productivity, on the early Earth. However, the extent to which molecular evolution has influenced the isotopic signatures of nitrogenase, the enzyme that catalyzes the conversion of atmospheric nitrogen (N2) to bioavailable ammonia, remains unresolved. Here, we reconstruct and experimentally characterize a library of synthetic ancestral nitrogenase genes, spanning over 2 billion years of evolutionary history. By engineering modern microbes to express these ancient nitrogenases, we assess the resulting ε15N values under controlled laboratory conditions. All engineered strains exhibit ε15N values within a narrow range comparable to that of modern microbes, suggesting that molybdenum (Mo)-dependent nitrogenase has been largely invariant throughout evolutionary time since the origins of this pathway. These results confirm the robustness of N-isotope biosignatures in the ancient rock record and bolster their utility in the search for life in extraterrestrial environments."
In fact as much as 50% of the Amazon's rain can be attributed to the trees themselves. Both through evapotranspiration strategies and increased cloud-seeding particles
However, I think the more relevant dynamic for this region is the water-holding capacity of the soil. If you get lost in a desert you are more likely to drown than to die of thirst because the water-holding capacity of the "soil" is almost nothing making flash floods likely. But soil that is at an advanced stage of ecological succession will be dominated by mycorrhizal fungi that produce glomalose. This type of soil can hold as much as 50x more water than "dead" soil
Rainforests are tropical largely because of the trees. If you cut them down, it reverts to desert. Geography helps, but it's mostly the plants changing local climate.
> [xenon is] great for in-space propulsion because it’s fairly heavy (so you get more ooomph per atom)
More specifically, for a given exhaust velocity and grid spacing, the space charge limited thrust density (thrust/area) of an ion engine scales as the square of the mass/charge ratio of the ions. So you really want heavy singly charged ions. This is completely unlike thermal rockets, where you want low molecular weight exhaust gases.
Plasma engines that accelerate a quasi-neutral plasma aren't subject to space charge limits, but even there heavy ions help because they reduce the energy used in ionizing the propellant per unit propellant mass.
BepiColombo [0] uses 581 kg of Xe gas for its electric propulsion. I remember reading at the time this was being built that it consumed a measurable portion of the global xenon production for that year. This post reminded me to look that up, and it seems to be only ~1% of the ~50 tons, which is quite a bit less than I remember but still quite significant for a single application to use a non-trivial amount of the supply.
Given that ~100 million tons of oxygen are produced annually, extracting all the xenon from that air would yield about 170 tons/year. So there's a bit of room for growth.
The BepiColombo number is similar, I think, to the amount of xenon made annually in nuclear reactors (where it occurs in spent fuel as the result of fission.)
I think it might have taken a larger percentage of high-grade ultrapure xenon, a narrower market than the global bulk supply. A 1% impurity is fine if you are using xenon for welding, not so much if you are firing zenon plasma at a grid carrying a few hundred volts. A little bit of o2 in there and your grid would be rust very quickly.
Inert gas in welding isn't used to carry heat, it's used as shielding to prevent oxidation, nitridation, and ingress of hydrogen. In any case, the heat capacity of the noble gases are almost identical. What xenon might do is reduce diffusion of heat away from the weld, as its thermal conductivity is just 1/3rd that of argon.
In practice I think a combination of argon and CO2 is typically used for inert gas welding of steel.
It depends on the process. Argon/CO2 is used for MIG welding, while TIG generally uses pure argon. In some situations that justify the expense, helium is used instead as it allows deeper weld penetration.
Sure, but one still has a savings if one goes to heavier noble gas elements over the lighter ones. The noble gases are used because they don't contaminate spacecraft surfaces.
About the only place I can think of in a plasma engine where you'd want to use light elements is if the engine is thermal: making a confined plasma, heating it to very high temperature, then expanding it through a magnetic nozzle. There, you'd want to use hydrogen to minimize radiative losses from the hot plasma, especially vs. using a plasma containing partially ionized atoms of higher atomic number elements; these can radiate fiercely.
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