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When you're talking about high doses, fractionating the dose definitely does reduce the damage due to the fact that DNA damage does have some capacity to repair. But that's not because of some hardening effect, it's because damage that could have gotten worse with further exposure has a chance to fix itself before the killing blow arrives. When you're talking about low doses, who knows, but I'd expect that the same things are happening just on a much harder to detect scale rather than some hardening effect.
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May 1, 2017 21:14
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Platystemon posted:It gets statistically messy. Not to mention different types of radiation, internal or external exposure, different isotopes affecting different organs...yeah, that's messy.
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May 1, 2017 21:16
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So what I'm hearing is dose yourself with small bits of rads over time to build up an immunity, like poison or bullets 
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May 1, 2017 21:40
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Light Gun Man posted:So what I'm hearing is dose yourself with small bits of rads over time to build up an immunity, like poison or bullets the tumors will absorb all the radiation before it gets to your more important organs
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May 1, 2017 21:59
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Luneshot posted:Honestly if I ever received a dose of radiation that would kill me within a couple days I'd just find a gun and skip the "excruciating death" part. You might not get much of a choice, but they might do something nice like put you in a medically induced coma do you're not present as your body rots away.
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May 1, 2017 22:04
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Wasabi the J posted:You might not get much of a choice, but they might do something nice like put you in a medically induced coma do you're not present as your body rots away. Unless your consciousness is necessary to their experiments.
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May 1, 2017 23:00
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BattleMaster posted:But that's not because of some hardening effect Idunno if you can say this conclusively
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May 1, 2017 23:07
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In fact I'm fairly sure that's wrong, non-fatal doses of ionizing radiation seem to upregulate heat shock protein generation at the very least.
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May 1, 2017 23:08
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Moist von Lipwig posted:In fact I'm fairly sure that's wrong, non-fatal doses of ionizing radiation seem to upregulate heat shock protein generation at the very least. Well, yeah. Radiation does all kinds of weird things to physical matter. It turns hydraulic fluid into goo, and hardens wood.
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May 1, 2017 23:40
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Hardens wood you say?
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May 1, 2017 23:48
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Moist von Lipwig posted:In fact I'm fairly sure that's wrong, non-fatal doses of ionizing radiation seem to upregulate heat shock protein generation at the very least. So what? Radiation "kills" a cell by tearing DNA strands so it can't reproduce properly. What will those proteins do about that? edit: the reason fractionated doses produce better survival rates than a single dose of the same total magnitude is that higher doses have a higher chance of causing a double strand break in DNA which has a chance of being repaired, but lower doses with time in between have a higher chance of causing single strand breaks that can be repaired between doses BattleMaster has a new favorite as of 00:11 on May 2, 2017 |
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May 1, 2017 23:55
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Heat shock proteins mop up unfolded or damaged proteins and repair broken sections of DNA in response to oxidative stress. If you get really slammed by radiation there's nothing that can be done but iirc there's a few cases of radiation resistant tumors that needed to be blasted harder because they had robust HSPs.
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May 1, 2017 23:59
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I don't think it's a particularly controversial statement that higher doses are more likely to screw up DNA beyond repair than lower doses, even with the presence of that protein. edit: I mean the stuff I've been posting lately isn't my opnion but it's what I've studied as a health physicist
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May 2, 2017 00:07
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BattleMaster posted:I don't think it's a particularly controversial statement that higher doses are more likely to screw up DNA beyond repair than lower doses, even with the presence of that protein. Nah, man, it’s like weed: Even if it causes cancer, its anti‐cancer properties more than compensate for that. 
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May 2, 2017 00:09
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zedprime posted:<50msv is well established as in the indistinguishable from noise part of LNT by airline pilots, >300 is established as linear as all hell by the studies on Japanese nuclear bomb survivors and the space in between doesn't really matter because it's just a range noone is exposed to often enough to characterize. Where do the different levels of space travel exposure fall on this scale? I know the Van Allen Belts are dangerous but what about past them or LEO?
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May 2, 2017 01:46
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Communist Zombie posted:Where do the different levels of space travel exposure fall on this scale? I know the Van Allen Belts are dangerous but what about past them or LEO? That'd depend on where you are how long you're there. Other planets have Van Allen belts as well. Solar flares are locally very bad news. A few hours on the surface of Io is a 100% lethal dose.
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May 2, 2017 02:39
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Notably, that last one's because Io is right smack-dab in the middle of Jupiter's Van Allen belt, or at least a high-energy radiation belt.
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May 2, 2017 02:43
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A long time ago I read James Michener's Space. It was a long book. The only part I found really memorable involved the effect that a decent sized solar flare would have on the crew of a lunar lander. It gave the impression that without a magnetosphere, you need to be able to put several feet of soil or several inches of metal between yourself and the sun if you want to survive a solar storm. afaik that's factored into spacecraft & station designs now, but was russian roulette in the Apollo days. Speaking of unforgettable reading, thx to whomever posted the link to stories of drag racers boosting their fuel with hydrazine.
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May 2, 2017 12:07
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Yeah, without a magnetosphere to deflect and trap the charged particles, you'll get a dose of radiation from a solar flare, mostly x-rays and energetic protons. I don't think any human astronauts have been hit so far, but it's one of the big challenges of building bases on the Moon or on Mars.
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May 2, 2017 12:17
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If you're on a planet then at least you can go underground. A big issue is what to do if a solar flare hits while you're in transit between planets. One suggestion is that while it's impractical to put that level of shielding on the entire vehicle, you can shield one small room. In the event of a solar flare everyone crams themselves into the storm shelter for several very uncomfortable hours.
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May 2, 2017 12:41
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Does the sort of particles in solar flares have adverse effects on electronics and the other equipment? I know chips have to have extra error checking and redundancy from the increased background radiation flipping bits occasionally.
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May 2, 2017 13:19
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A CME is all plasma, so the ship's going to be getting hit by a lot of charged particles. It'd be an incredibly powerful EMP that would most likely kill all electronics in the ship. The Carrington Event in 1859 was when a CME that hit Earth directly; in addition to the tropics getting to see auroras, above-ground telegraph wires were set on fire by it. Some operators got shocked as their lines discharged through them, and others were able to turn off their power supplies and send messages using the solar flare's charge. That's what got through our magnetosphere and our atmosphere, so I would be very surprised if it was even possible for a ship in interplanetary space to survive. The shell would, probably, but anything that requires electricity wouldn't, such as the life support. You may as well not include a storm-shelter room, since the heat / lack of oxygen would kill the astronauts far before the cancer or their bone marrow liquefying. Obviously getting hit by a Carrington Event CME is worst-case, but even a "small" one would really gently caress up the ship's systems.
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May 2, 2017 13:33
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That's assuming it was hit directly by the CME, even as big as Coronal Mass Ejections are, it's rare that they actually collide with things. The increased activity from a solar flare though is spread over a much wider area and is something you'd have to prepare for and plan around. Getting directly hit by an energetic stream of plasma from a CME in a spacecraft isn't something you can prepare for, except by making out your will.
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May 2, 2017 14:09
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Hremsfeld posted:A CME is all plasma, so the ship's going to be getting hit by a lot of charged particles. It'd be an incredibly powerful EMP that would most likely kill all electronics in the ship. The Carrington Event in 1859 was when a CME that hit Earth directly; in addition to the tropics getting to see auroras, above-ground telegraph wires were set on fire by it. Some operators got shocked as their lines discharged through them, and others were able to turn off their power supplies and send messages using the solar flare's charge. But that's a geomagnetic phenomenon: the plasma interacts with Earth's magnetic field and as that field moves around in response to the plasma it drives geomagnetically induced currents. If Earth had no magnetic field, the things observed during the Carrington Event wouldn't have happened. Solar plasma itself is a neutral plasma, it's not going to generate an EMP all on its own out in space somewhere. Solar flares and CMEs can absolutely wreck spacecraft electronics, but they do it by just being a bunch of high-energy protons and electrons that wind up where they shouldn't be. It's not a matter of EMP. The answer to that is hardening of the components to withstand radiation, and redundancy. We build spacecraft that have withstood intense radiation for considerable periods of time, and while there are occasional current leaks and latch-ups and transitions to safe mode, it's something that's generally survivable. Galileo took a "whole body" dose of well in excess of 6,000 grays, including a hit from a massive (X5+) solar flare in 2000, and while it experienced degradation (including its camera completely whiting out, despite being protected by a centimeter of tantalum), that spacecraft survived far longer than its design lifetime. For stopping protons, you want something with a lot of protons in it per unit mass. Polystyrene is good. Hydrocarbon fuels are good. One thing that any interplanetary traveler would need a lot of is water, which is also good. And since you have to carry all that water mass along with you anyway, it'd be a good idea to design your ship so that your water tanks are also your radiation shielding, at least for a storm shelter. Phanatic has a new favorite as of 14:59 on May 2, 2017 |
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May 2, 2017 14:55
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It's a bit more complicated. You need something dense to stop the protons, then you need something to moderate the high energy neutrons that are knocked out, and then you need something to absorb the neutrons. Water is a great moderator but then you'd want something with boron or cadmium or gadolinium to actually stop the neutrons. And then you might want something to stop the capture gammas that will be released if the flux is going to be high enough. Radiation shielding can be kind of annoying to design because of interactions like that
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May 2, 2017 15:05
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BattleMaster posted:It's a bit more complicated. You need something dense to stop the protons, then you need something to moderate the high energy neutrons that are knocked out, and then you need something to absorb the neutrons. Would you get any appreciable neutrons from solar wind impacts? The particle energies aren't all that high. And note that you don't really want something *dense*. You want dense high-Z materials for stopping photons, because they're stopped by electron interactions so you want as many electrons per volume as you can manage. But a proton (or neutron) that smacks into a heavy nucleus is going to be like a tennis ball hitting a brick wall, it's just going to bounce off in a new direction and retain most of its original energy. You want the proton to smack into something that's roughly as massive as it, so it will transfer a bunch of energy to that thing and slow down. That's why you stuff with as much hydrogen in it per mass is what you want. quote:Water is a great moderator but then you'd want something with boron or cadmium or gadolinium to actually stop the neutrons. It pretty much does that. I mean, it doesn't bring them to a total stop but neither would anything else. It thermalizes them down from however many MeV they had when they were ejected from their parent nucleus and brings them down to a fraction of an eV, that's pretty much as stopped as they're going to get. A .025 eV neutron isn't a radiation hazard to anything, except for the recapture gamma. quote:And then you might want something to stop the capture gammas that will be released if the flux is going to be high enough. Well, there is that. The hydrogen will absorb the thermal neutron and turn into deuterium and emit a 2 MeV gamma as it does so. But the neutron flux isn't going to be high to begin with I don't expect. quote:Radiation shielding can be kind of annoying to design because of interactions like that And with high-energy cosmic rays you can be better off *not* stopping them, because they can have enough k.e. in the first place to create a huge shower of secondaries if they smack into something.
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May 2, 2017 15:51
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I thought the current philosophy was water + boron shielding for a storm shelter. Relatively inexpensive and boron is pretty lightweight too.
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May 2, 2017 16:09
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Phanatic posted:Would you get any appreciable neutrons from solar wind impacts? The particle energies aren't all that high. Protons and neutrons don't work the same way as far as shielding. Heavy charged particles like protons stop almost entirely due to coulomb force while neutrons interact only with the nuclei via strong nuclear force. The only thing that matters for heavy charged particles is density of electrons (which correlates with both Z and mass density), while the mass of individual nuclei don't matter; it's just that higher masses correlate with higher numbers of electrons in most cases. That's why you want metals like lead for stopping protons. You're right about neutrons though. Because they interact directly with the nucleus and only the nucleus they won't lose much energy unless the nucleus is of a very similar mass. I'd disagree with thermal neutrons never being a hazard - remember that humans are made of hydrogenous materials - but as with all radiation it heavily depends on the flux. I thought we were talking about really crazy situations like solar flares where you'd have high fluxes, high energies, and want to have a multilayer approach. This could be an issue on long duration journeys like to Mars. BattleMaster has a new favorite as of 16:15 on May 2, 2017 |
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May 2, 2017 16:11
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BattleMaster posted:Protons and neutrons don't work the same way as far as shielding. Heavy charged particles like protons stop almost entirely due to coulomb force while neutrons interact only with the nuclei via strong nuclear force. Derp. I knew that. In my defense, I am sober right now. Anyway, here's an exceptionally detailed paper on rad hazards to astronauts on the ISS and during EVA: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.118.2763&rep=rep1&type=pdf
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May 2, 2017 16:53
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Phanatic posted:Derp. I knew that. In my defense, I am sober right now. Thanks for that, space isn't something I've studied a whole lot so it will be interesting.
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May 2, 2017 17:02
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I know a poo poo ton more about toxic chemicals (Chem Engineer) than radioactivity so thanks for all this info. Terrifying and fascinating.
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May 2, 2017 19:27
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https://i.imgur.com/dTY8Odm.gifv The title on reddit said "The world's strongest acid versus a metal spoon", but it was debunked as a gallium-aluminum spoon and warm/hot mountain dew.
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May 2, 2017 19:31
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`Nemesis posted:https://i.imgur.com/dTY8Odm.gifv Except gallium drops down as a blob on the bottom of the glass, and doesn't turn black. This might be actual acid.
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May 2, 2017 19:37
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Speaking of gallium, does anyone know if there's any toxicity associated with it? I may be using it for some "magic" for a show that would involve people handling it fairly often.
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May 2, 2017 19:57
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Carbon dioxide posted:Except gallium drops down as a blob on the bottom of the glass, and doesn't turn black. This might be actual acid. He sticks his hand in after if you watch the video. https://www.youtube.com/watch?v=5Qc_Sy6IAlI The black is from the aluminum the gallium was alloyed with, which forms gray aluminum oxide and hydrogen bubbles.
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May 2, 2017 20:02
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chitoryu12 posted:Speaking of gallium, does anyone know if there's any toxicity associated with it? I may be using it for some "magic" for a show that would involve people handling it fairly often.
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May 2, 2017 20:03
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zedprime posted:Its a light metal so its fairly harmless unless you are reacting it with things that make it less fairly harmless. If you're talking about randos handling it your wallets going to hurt more from attrition than anybody is going to get hurt by chemicals. I was thinking of having one of the guests handle it incidentally to let them know that it's actually metal they're touching, followed by the person performing the magic taking it from them and doing something with it like causing it to rapidly melt in their hand or dissolve into a glass of tap water. One possible idea is a modified glove with a heating pad or similar heater in it.
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May 2, 2017 20:21
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Carbon dioxide posted:Except gallium drops down as a blob on the bottom of the glass, and doesn't turn black. This might be actual acid. It's definitely dropping down as blobs on the bottom of the glass, you can see them rolling around there and not reacting with anything.
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May 2, 2017 20:20
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Gallium seems like it would be such fun to play with.
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May 2, 2017 20:23
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I've seen reusable gallium spoon kits available; might want to track one of those down if you can find it at a price you're willing to pay.
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May 2, 2017 20:40
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