This seems really nice as a sketchpad for small flowcharts. I'd definitely use it to map out a small piece of work, because I'm terrible at laying out flowcharts on scrap paper without wasting space or painting myself into a corner.
One minor annoyance: I can't use tab/shift+tab to indent or dedent lines.
I think people here (USA) see the news out of China/Italy and think it's not that bad here, without realizing we're 1-4 weeks away from starting to see how bad it will actually get.
> ...must be cleaved by furin or furin-like proteases to become fully functional. Anthrax toxin, pseudomonas exotoxin, and papillomaviruses must be processed by furin during their initial entry into host cells.
From the sound of this:
- the site on the virus gets cleaved
- Furin enables the cleaving
- Furin exists in hosts cells
What I think I understand is, the cleaving makes it easier for the virus to reproduce inside the cell?
edit: turns out I have no idea how to format things on HN
Thank you, that makes a lot more sense than some sort of “gain” (as in, increasing output levels) of “function” (as in, a mathematical calculation where each input has exactly one output).
Yeah the function here is not a mathematical function - it just means functionality, like the thing that it can do. Sometimes we biologists can be spectacularly uncreative in naming things :)
The kind of tank design that appeared in World War I. They were designed to cross the cratered wastelands and trenches created by the fighting. The crews fought from gun ports and mounted cannons/machineguns, rather than a rotating turret.
I have no idea if molten salt reactors are as awesome as this website represents them to be, but I thought the following point was interesting:
"light water reactors can use only about 4% of their available energy."
They're comparing with 1960s reactors designs, so maybe more modern water reactors are more efficient. But, it's still amazing to me that there's that much more energy that we could potentially harness from the fuel.
It's because light water reactors use thermal (i.e. slowed down) neutrons, which can only fission U235, and that's 0.7% of natural uranium. We enrich the fuel to at least 2% U235 and that's mainly what the reactor can use.
The reactor also gets about a third of its energy by fissioning plutonium, which is formed when U238 absorbs a neutron.
Without reprocessing, a light water reactor can't even fission all the U235, because some of the waste products of fission reactions are strong neutron absorbers. (If you're in France you can reprocess the waste to remove the fission products.)
Molten salt reactors remove most of the fission products continuously. Some MSRs, like Terrestrial Energy's, are still thermal reactors using uranium, so they're about as efficient as France.
Some MSR designs use fast neutrons, which are able to fission more plutonium along with other transuranics and U238. Others use thorium fuel, which can be completely fissioned by thermal neutrons. (First thorium absorbs a neutron and becomes U233, then that fissions. Heavier non-fissile isotopes aren't created in the first place.)
Currently the fuel is very inexpensive - a tiny fraction of the total cost of the electricity produced. Most of the cost is the initial capital, and most of the ongoing cost is the (highly specialized) labor. A new reactor design that saves fuel is not really what the industry needs.
According to Wikipedia current uranium reserves will last for 135 years. It would be 13 years if we increase energy production in nuclear plants 10 times to replace coal and gas.
So even if fuel is inexpensive now, it can become expensive quite quickly.
I believe Peak Oil was supposed to happen a dozen times now; we keep finding more when it becomes worthwhile to do additional exploration, and extraction technology keeps improving. Maybe uranium is different, but I would believe it when I see it.
As per wikipedia: "Peak oil is the theorized point in time when the maximum rate of extraction of petroleum is reached". You can still discover new sources of petroleum after "Peak Oil", but the idea is that you will never find enough to increase the maximum extraction rate.
What we see as consumers is conflated by the fact that there are self-imposed limits on extraction by OPEC designed to raise prices. Due to various political situations, those limits have been slowly removed. When you see predictions of "Peak Oil", often they are based on existing production and not maximum production (and hence are nonsense).
I'm not aware of any literature that attempts to speculate on current maximum production capacity. Probably it exists, but I certainly can't find it. Whether we have hit "Peak Oil" already, or whether it will come in the future, I don't know. A lot of that kind of stuff is politically very sensitive and oil companies/OPEC are understandably reluctant to be straight forward with the data.
Finite resources eventually run out. When you don't know how much you have, it's tempting to assume that because you are finding more, you will continue to find more. There is no real guarantee of that. It's a risky strategy.
EROI has been driven down with every single year. One day it will take more energy to extract it than the energy we receive from it but we won't run out.
What about the ongoing cost of waste and eventual cost of decommissioning? Are those affected by quantity of fuel used (or, more specifically, by Transatomic's design)?
When a reactor is built in the US, the operator will start paying into an account for waste disposal. This is included in the cost of energy production. Since high level waste quantities are pretty low for nuclear reactors (About 27 tons a year)[1] disposal of fuel isn't the largest issue.
Decommissioning on the other hand is remarkably expensive because of secondary nuclear waste like contaminated reactor vessels and concrete make up 99% of the nuclear waste.
1. The position and size of the upgraded engines for the 737 MAX caused the plane to tend to pitch upwards, which could cause a stall.
2. Boeing was concerned designed MCAS to automatically push the plane's nose down to prevent stalls
Every single piece of reporting I've seen on the matter refers to MCAS as an anti-stall device.
Pilots of 737 who have talked to reporters refer to it as an anti-stall device.
I have a hard time believing that this information hasn't been fact checked to hell and back yet.
> Every single piece of reporting I've seen on the matter refers to MCAS as an anti-stall device.
Assuming you are a developer, have you ever seen some reporting of something technical in the news? Does it not make you cringe?
> Pilots of 737 who have talked to reporters refer to it as an anti-stall device.
Even Boeing themselves do; so who can blame them. The reason that the certification item exists is to prevent certification of aircraft which demonstrate increasingly lighter control forces as the aircraft approaches a stall. The reason being that it makes it easier for an inattentive pilot to accidentally fly the aircraft into a stall. So if you want to shorten that to anti-stall then I'm fine with that.
What I don't really like is the retoric about how these aircraft would fall out of the sky without MCAS "controlling" the plane. It isn't a closed loop control system implementing PID control to account for some crazy instability in the aircraft.
> Every single piece of reporting I've seen on the matter refers to MCAS as an anti-stall device.
"Anti-stall" has become a catchphrase wrt the 737 MAX. I wish everyone would stop using it, but the horse has left the barn it seems.
MCAS was cooked up to maintain the handling characteristics required by the FAA certification specifications.
Other commenters in other threads have explained why consistent response curves are vital in operating an aircraft, so I won't take on the why of the regulation other than to say it's well founded and some smart systems/human factors engineers have elucidated on this in earlier threads. Otherwise, wouldn't it have been easiest of all for Boeing to beg "let us have the airplane respond this way; all planes are different, right?" And even if the FAA allowed that, it'd force a new type rating, I suspect; the very thing they so badly wanted to avoid.
The standard (see below) requires stick resistance to increase as the critical (stall) angle of attack is approached. The MAX violated that requirement due to the aerodynamics of the new engine cowls. (So: why didn't they mess with the cowls? I suspect that wasn't possible without impacting efficiency, which is a key selling point of the MAX.)
Back to the spec: as noted, it exists to provide a consistent response curve to the pilot compliant with the regulation.
As borne out by these accidents, MCAS is Boeing's (quick & dirty) implementation of "artificial feel" to meet the spec. Big, transport planes with hydraulic flight controls have had artificial feel for many years to provide a consistent and properly scaled input response (not too heavy, not too light, etc.)
As far as the FAA specification in question, the critical section is in CFR 14 §25 Subpart B—Flight ¹, notably the sections on Controllability & Maneuverability and Stability. In these sections 'stick force' appears sixteen times; 'stick force curve' appears six times.
It's "stick force curve" that MCAS was created to tweak. There's no mention of "reduce the critical angle" or "change the stall onset speed" or anything about the aircraft performance. It's about how the plane handles in a particular part of the flight envelope².
> Every single piece of reporting I've seen on the matter refers to MCAS as an anti-stall device.
Because it was printed repeatedly doesn't make it true (see, Gell-Mann amnesia effect³).
²–I'm surprised that MCAS reacts fast enough to count as artifical feel. Electric trim doesn't move all that fast, AFAIK. Still an open question in my mind.
One minor annoyance: I can't use tab/shift+tab to indent or dedent lines.