Recent comments in /f/askscience

gridsandorchids t1_j5z56m5 wrote

Reply to comment by stickmanDave in Why do sample return missions such as OSIRIS-REx use their own reentry vehicles instead of just going to the space station for pickup and return with ISS equipment? by PromptCritical725

He's talking about something going wrong in the final approach to dock, which also shows how complicated the whole concept is. Once you get to a matching orbit, and close enough on a stellar scale, it's still highly delicate and specialized to actually safely recover it.

MIR had a Progress craft smash into it and almost kill the station and inhabitants and it was just docked and then pushed out a bit and brought back in.

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mckulty t1_j5z4kh0 wrote

Reply to Is it possible for me to develop a cold from a virus i was exposed to before qnd fought off and/or been gone latent in my body without being exposed to other sick people? How long can cold viruses be latent in the body with the ability to reactivate? by sewcrazy4cats

There are over 200 viruses known to cause a "cold." They include several families, like rhinoviruses, adenoviruses and coronaviruses. As a rule, those families don't "lie dormant" like herpesviruses.

Getting a cold often incurs some immunity to that virus, and maybe a few of its cousins, for a few months or years. But immunity to one virus doesn't guarantee immunity from all the other cold viruses.

Also bacteria can cause superinfections in compromised tissue, and general infections or metabolic stress makes one more susceptible to viral infections. Cold sores come back under stress, but those are herpesvirus, not "cold" viruses.

NIH: More than 200 different viruses are known to cause the symptoms of the common cold. An estimated 30-35% of all adult colds are caused by rhinoviruses. In people with asthma, particularly children, rhinovirus infections are also frequently associated with flare-ups.

Last edit.

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ZLH-040 t1_j5z1wwb wrote

Reply to How hot is the steam coming out of nuclear power plants? by ivy-claw

Reactors use a closed loop system that is prevented from escaping into the environment. There's a heat exchange process so clean outside water gets heat from the water exposed to the reactor.

After that, the clean water in the reactor turns the generator turbines just like gas or coal plants would. The steam escaping the cool towers is clean, non-radioactive water.

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LetterBoxSnatch t1_j5z15vc wrote

Reply to comment by Equoniz in Why do sample return missions such as OSIRIS-REx use their own reentry vehicles instead of just going to the space station for pickup and return with ISS equipment? by PromptCritical725

I suppose it depends on just how elastic your definition of “elastic” is…the materials may still be capable of reattaining their prior size and shape, given enough energy and engineering dollars

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mancapturescolour t1_j5z0ck9 wrote

Reply to comment by [deleted] in What determines whether we can create a vaccine for an illness or not? by ShelfordPrefect

Thank you, that is very important to point out. I appreciate your insights, it's so valuable to share.

It's a multifaceted issue and what you state, adherence, is a key point indeed: Undetectable = Untransmittable aka (U=U). For that to happen people that need these ARVs must have access, and be comfortable to take them regularly for a long time.

We're not there yet but I believe we will have the means to turn this epidemic around completely. Whether by vaccines, replacing stigma by normalization of what life with HIV is today, or arriving at an HIV free generation...as long as there's a will, there's a way. Just the idea that you can lead a "healthy" and normal life with HIV today is so mind-blowing compared to how it was only a few decades ago.

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radioactive_dude t1_j5z03ka wrote

Reply to comment by colt61986 in How hot is the steam coming out of nuclear power plants? by ivy-claw

The boiler side of reactors is not my area of expertise, but I'll try to answer your question. My understanding is the water that is used to make steam for the turbine is a closed loop because the water chemistry and steam quality is very important to safely operating the fast spinning turbines with many blades. For that reason, the water needs to be fresh water.

For desalination, my understanding is there is still enough heat in the steam after it has run through the turbines that it can still boil water, but is not useful for generating further electricity. It is a way to use this waste heat. I believe such systems completely separate the turbine loop water from the desalination water. Essentially, it is seawater sprayed on hot piping to create fresh water steam. The turbine water (downstream of the turbines) flows through the piping in a closed loop to keep it hot.

As for desalination at nuclear plants, there is experience in Kazakhstan and Japan in doing so. I don't know why it hasn't seen more widespread use. I am guessing the need is not that great as lots of reactors are located near large bodies of fresh water by design. The nuclear physics in a reactor can also be complicated by changing temperature, so complicating the heat removal system is probably avoided unless it is a specific requirement.

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Rangoras t1_j5yxvzt wrote

Reply to comment by [deleted] in How hot is the steam coming out of nuclear power plants? by ivy-claw

Sea water needs to be desalinated before being used in a boiler. If you only just filtered it for solids the salts in the water would form a nasty layer of scale on the water side of the boiler tubes quickly resulting in poor heat transfer and failure of the boiler tubes. When we make our boiler water on my ships we only use water where salinity is under 5 PPM

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