skillissuer

skillissuer , 3 months ago

robots, satellites, or for that matter fighter jets or artillery can't hold ground, all these units work in support of infantry. the future belongs to what we already have: combined arms warfare

skillissuer , 3 months ago

not when there's a shortage

skillissuer , 3 months ago

russia and nk uses 152mm, not 155mm

skillissuer , 3 months ago

GLSDB is cheaper than regular GMLRS rocket. ramjet 155mm is prototype. there's another obscure 155mm ammunition called vulcano that basically packs smaller HE sabot round in 155mm, trading off payload for range, ramjet takes it even further

skillissuer , 3 months ago

somebody already put lasers on F35 and israelis are using ground-based lasers as a complement to iron dome

skillissuer , 3 months ago

is that autoturret in the room with us?

skillissuer , 3 months ago

there are also fiber lasers with enough power for small, slow targets like drone and size small enough to fit in a modern western fighter jet pod. targeting is done via radar roughly and then the same optics , or similar optics that laser uses later

skillissuer , 3 months ago

the difference is in different cost of workforce, different manufacturing standards, different materials, different fill, different fuze (easily 1/3 of cost),

skillissuer , 3 months ago

you're thinking of scihub. if you have some 130 TB? of spare storage you can mirror their entire repository

skillissuer , 3 months ago

yeah it's even out there as a list of torrents

skillissuer , 3 months ago

sci-hub and libgen already outputs list of torrents. do they also archive supplementary information? that's where most of actual interesting data is, sometimes it's open source, sometimes it's not. (at least in my field)

skillissuer , 3 months ago

elsevier doesn't want you to know that, but you can download sum total of human knowledge for free. i have 3924 papers

skillissuer , 4 months ago

helium just boils off in MRI/NMR machines, this is the major use of helium i think. if you could recycle that in machines that already are out there, that would solve lots of problems. there are newer systems that do not require cryogens or just require liquid nitrogen which is much cheaper and less energy intensive. these things use closed loop refrigeration, but in turn you need to supply them with power

skillissuer , 4 months ago

wdym by "low purity" helium, helium that has been purified cryogenically is easily 99.999% if not better, and this is the main process used worldwide iirc

skillissuer , 4 months ago (edited 4 months ago)

Tommy's dad didn't steal tank of 6N helium, but it did rolled off the same facility using the same process, main impurity being air (considering it's a rather minor use, maybe balloon gas is just what is left after cleaning or purging empty helium tanks of higher grade. so it's maybe not a massive loss. recycling helium within cryogenics and MRI would provide more benefit)

also wtf is "grade", 6N means "six nines" means 99.9999%. (americans will use anything but metric units) liquid helium freezes everything else out so it's 5N without any special extra purification, or at least that's my impression from looking up spec sheets of helium from facility that i know uses cryogenic purification for it

skillissuer , 4 months ago

it's much more complicated than that, and the most useful property of helium is its low boiling point. it goes like this:

first, you start with natural gas that has some nitrogen, some water, some helium, some carbon dioxide, heavier hydrocarbons, thiols, dust, and such. mechanical filtering gets rid of dust and mist, water, carbon dioxide and thiols are removed chemically, heavier hydrocarbons are removed on active carbon. now we have mix of methane, ethane, hydrogen, helium, nitrogen, traces of carbon monoxide, dioxide and water. this all is cooled down, first just to freeze out these trace amounts of water and carbon dioxide, then to liquefy what is left.

next this liquid mixture is put through massive distillation tower, allowing for separation of mainly nitrogen and methane. this nitrogen and methane are end products, some are sold as liquids but most are regasified in order to cool down incoming gas and save some energy. another product is helium concentrate, at this point it can be 50% to 80% with rest being nitrogen but this depends on exact facility.

then, some extra air is added to helium concentrate, it's heated up and passed over catalyst bed. this is done in order to burn out hydrogen and any hydrocarbons, because separating oxygen from helium is much easier than separating hydrogen from helium. products of this burn are water and carbon dioxide that can be separated chemically. then again it's all cooled down, nitrogen and oxygen are liquefied, then it's all cooled down further and from some 30K on it's just helium being circulated as gas because you can't liquefy it like any other gases, it needs a special process. on every pass, with extensive recycling of heat some part of it is liquified and this is the final output, 5N liquid helium.

at least that's how it works in a facility built in 70s in then eastern block. now it supplies half of europe and a research facility situated nearby. i suspect it was built with at least some military applications in mind during this time, namely helium is used for pressurizing hydrogen tanks of rockets, but also soviets toyed with an idea of using gas lasers militarily. this requires a supply of helium, and a supply of neon is also a nice thing to have in this situation. neon was produced in Azovstal cryogenic oxygen factory serving nearby steelworks, as it can be separated from air. it ended up providing virtually all neon for semiconductor manufacturing in the world, but from what i understand there are alternative suppliers by now

skillissuer , 4 months ago

yes you can, crude helium + air mixture (few %) is used in first stages of cryogenic helium purifying

skillissuer , 4 months ago (edited 4 months ago)

technology is there, the issue is to run it cheaply, reliably and on scale. this is the actual problem

edit: i mean it's a problem that responds well to throwing money at it. if there was extra need for helium that would be met by diverting balloon gas, then it would work at some price, but we're nowhere close to it

skillissuer , 4 months ago

it's pretty fucking hard. only six countries in the world produce helium, and you get engineering challenges that don't exist anywhere else. for example you can't use any grease on helium turbine bearings in the lower temperature stages because all of them freeze, so the solution is to use gas lubricated bearings. this is some serious precision engineering that has to work in extreme conditions

it's also hard because the simpler way of liquefying gases, like the one used for nitrogen that uses no moving parts in the coldest part, fails for helium, this makes liquefying helium harder than any other gas. it's also hard because of limited availability. it's hard because of massive capital costs and lots of custom machinery. it's hard because of scale required. about any other compound can be manufactured without at least some of these problems

skillissuer , 4 months ago (edited 4 months ago)

balloon helium has some air in it, it's still 90%+ helium, probably

skillissuer , 4 months ago (edited 4 months ago)

energy expenditure would be similar to purifying it from helium concentrate, so not much difference. considering small volume of balloon helium this wouldn't probably mean large increase. i also don't know what this guy is about

skillissuer , 4 months ago

yeah it's distilled off from nitrogen-heavy natural gas, like you could do with nitrogen-heavy gas without helium, or even air. all three processes are done commercially. the issue is that helium bearing natural gas is limited in supply and getting low enough temperature at latter stages of helium refining and liquefying requires bespoke facility. this part is hard

skillissuer , 4 months ago

hydrogen is the easy one, because you can burn it off on catalytic bed, then pass through bed of 3A MS to trap water. done

separating excess oxygen and nitrogen is easier and there's already some nitrogen (as much as 50%) in crude helium

skillissuer , 4 months ago

depends on manufacturer, some state it's just 50%

skillissuer , 4 months ago

i've took time to actually look up various manufacturers' datasheets and it's: range 50-99%, 95%, 97%, range 95-100%, 99%, unspecified or just data for pure helium. at this point i'm pretty sure there's no such thing as "balloon gas manufacturer", everyone buys 4N+ cryogenic helium and balloon gas consists of odds and ends that come from flushing piping and empty bottles with better stuff

skillissuer , 4 months ago

how much do you need to float, if it's helium then 1L lifts about 1g of mass, if it's 50% helium 50% air it lifts 0.5g per liter, then it depends on how heavy balloon is in relation to its volume

skillissuer , 4 months ago

not exactly, because if someone finds out that high temperature superconductor works even better at 4K, then it will be running at 4K, making entire thing more compact or allowing for higher fields

skillissuer , 4 months ago

wait, that wasn't the entire point?

skillissuer , 4 months ago

it's part empty marketing fluff and part SEO

skillissuer , 4 months ago

on the internet nobody knows you're a bot (or damage control PR shill)

skillissuer , 4 months ago

how many of them are dummy accounts or bots?

skillissuer , 4 months ago

nope, grue is right. medical anti-adhd amphetamines use vs street use mostly boils down to dose and route of administration. there is difference in potency but not some massive like with fentanyl vs heroin (20x)

skillissuer , 4 months ago

contamination with weird shit only happens with small scale manufacturing using no purification at all. large scale manufacturers will usually know a bit or two about organic chemistry, and processes more suitable for large scale manufacture don't introduce them at all (and don't require pseudoephedrine)

yes, the difference is dose, you'll see the same shit in people popping 50 adderal pills a day

skillissuer , 4 months ago

the only real difference is t1/2, fine, but it hits the same receptors with potency that is at least in the same ballpark (as in, not 10x, more like 2x)

skillissuer , 4 months ago

well, i guess you're guessing correctly about yourself, but you're guessing wrong about me (partially)

Most of the people who were busted working there ultimately died of liver failure.

as a chemist this doesn't surprise me at all. at every step you'll see, typically, something like 10g of solvent per 1g of product. then there's some solvent being used for purification as well, how much of it depends on technique being used. i doubt that visit of osha is the top concern of cartel lab manager, so these poor sods are going to be soaked in solvents, or at least solvent vapours 24/7. it's the liver that deals with it all and if it can't do it effectively, most notably this happens with chlorinated solvents (cheap, convenient, low boiling: DCM) liver gets fucked and that's the end result. some routes involve such friendly chemicals like benzyl chloride, this won't help either

when i was talking about impurities i was mostly talking about residual iodine, alkyl iodides, some weird phosphorus(III) compounds, occasional aziridine and such. similar compounds were responsible for side effects of a drug most commonly known as krokodil. i forgor about (R)-meth, chemically speaking, both (S)- and (R)- isomers are meth, these just differ in pharmacology, the active being (S)- and (R)- just being decongestant. usual P2P process provides 1:1 mix of them, but separation could probably make the process rather expensive (and what do you do with (R)-meth?). i suspect that instead someone developed an asymmetric P2P process, or something else entirely, which means that big meth labs moved from first year organic chemistry lab level to bsc thesis level. that's a progress, i guess, probably to be accompanied by new and exciting cases of heavy metal poisonings in the future

i understand it's a cultural thing. in US, as i suspect you are american, meth is sold in bulk drug of the poors, and amphetamine is (illegally) sold as pills to stock gamblers^W^W^W traders and SV engineers, that is the rich. this is absolutely not a global situation and for example in my country the street stimulant of choice is amphetamine sold as a bulk powder and i can assure you it can be every bit just as destructive. and this is before you consider things like alpha-pvp that have paranoia as an intended feature and there are people that like this effect specifically. goes without saying that street stimulant users won't be usually very picky about what they will try that day. just in the case it's unclear: i'm not saying that meth is good or that evil psychiatrists poison kids with adhd with drugs, i'm saying that you're underestimating how dangerous amphetamine can be, in some contexts, in comparison to meth.

my source for that is my own degree in organic chemistry, former flatmate that worked in harms reduction organization, and not having my head firmly embedded in my ass. i won't disturb your smug undeserved sense of superiority anymore, have a nice day

skillissuer , 4 months ago

already done and with crypto at that

skillissuer , 4 months ago

can you really trust them in this assessment?

skillissuer , 4 months ago

last time i've checked ais are pretty bad at recognizing ai-generated content

anyway there's xkcd about it https://xkcd.com/810/

skillissuer , 4 months ago

this is explicitly illegal under GDPR

skillissuer , 4 months ago

but you can sue their ass over it

skillissuer , 4 months ago

ah yes, the wonders of predatory publishing

skillissuer , 4 months ago

ah yes, the torment nexus

skillissuer , 4 months ago

stop the presses!! a cryptobro got scammed out of 90k$ "worth" of fake money, we must slow down all computation! for safety

https://discuss.tchncs.de/pictrs/image/5aef89b1-67d3-40a8-b869-a7adbb3438e6.jpeg

skillissuer , 4 months ago

the money was lost the moment it hit exchange account full stop

skillissuer , 4 months ago

You don’t use crypto

ftfy

skillissuer , 4 months ago

yall have no cheap/free bank transfers? is that some american problem i'm too european to understand?

skillissuer , 4 months ago

you've linked entire community, not single thread

skillissuer , 4 months ago

just after nitter was killed