Very Interesting!

Alcohol is an antidiuretic hormone inhibitor. There's this substance in your body that works to keep you from peeing out more of the water inside of you than is healthy, but alcohol gets in its way and interferes with its work, so when you drink, you pee too much.

https://en.wikipedia.org/wiki/Vasopressin

The other comments about alcohol being an antidiuretic hormone inhibitor are correct but a study I can't find atm found that upto 4% alcohol still hydrates you as the ~96% water you're drinking outweighs the keeping less water. And really you're only going to the loo more because you're often drinking a lot of liquid when out drinking.

Alcohol is a diuretic which causes your kidneys to pull more water from your body and produce more urine. If all you drink is alcoholic beverages you are not replacing the water you are losing, which can lead to dehydration and hangovers. Best advice, for every drink you have, drink a glass of water.

Your kidneys think you are being poisoned by the toxic alcohol and therefore trying to wash it all away, by using whatever water in your body it can find. To that end your dehydrated.

There is a hormone called ADH that tells your kidneys to just filter water but keep some and send some to the bladder. Alcohol won't let it be produced by your brain so your kidneys just assume that there is too much water in your blood stream and send it all to your bladder.

So you pee like you are well hydrated, while actually becoming dehydrated. The common term "breaking the seal" is really just the start of this cycle of your bladder not holding anything back.

Military aircraft are equipped with radar warning receivers (RWR) which works just like a radar detector people put in their cars. Radars work by transmitting a pulse of radio waves and waiting for the echo. Based on the frequency of the pulse and the pattern it pulses at it can make a guess as to what kind of jet or surface radar it came from. If you're an american F-16 and you hear the pulse from a french rafale you can assume he's not trying to shoot you down. If you hear a pulse from a russian bult SU-27 you can assume it's not friendly.

When you lock on to an enemy jet the pulses coming out of your radar are much more frequent so you can assume the enemy pilot is trying to shoot you down. Once the enemy has you locked up and fires a missile at you, if your jet is equipped with missile waring system (MWS) it can detect the flare from the rocket motor and warn you there's a missile inbound. Not many jets are equipped with MWS though. If it's a heat seeking missile you have no warning besides that; active radar guided missiles will have their own radars inside, once it's close enough the radar inside will turn on and you will get another warning once your RWR picks up the missile's radar.

Imagine you're in the dark with a flashlight. You're looking for someone, but you don't know what direction they're in, so you wave the flashlight around.

This is kinda like a normal radar sweep. you might see someone, but it'll be a second before you see them again, as your flashlight eventually comes back to them.

When you see someone you want to "track", you point your flashlight directly at them (or, in the case of radar, you waggle your flashlight over a very small area)

But now imagine you're the one being looked for. If there's someone with a flashlight looking for you, they'll be waggling their flash light all over the place. It might pass over you once, but if it keeps going, it's probably just a normal sweep. If, however, if they start pointing the flashlight directly at you, and ignore everything else, it's pretty safe to assume they've got a lock.

Missile lock warning systems like that but they are for radar-guided missiles. Radar works as a transmitter that emits microwaves and is reflected back to the missile and it follows the reflection. So the aircraft have microwave receivers that detect when it is illuminated by a radar.

You can compare it to old searchlight where the crew can use their own eyes to see that they are being tracked. The radar warning is just it another frequency.

You tend to use different frequencies microwave frequency for detecting them with radar and for guiding a missile. It is about how excited you know the position vs how easy it is to scan large areas. So the aircraft look at the frequency of the signal. So it can warn the pilot when a radar used to guide weapons is illuminating the aircraft. An enemy radar lock on you is when they continually illuminate you with a radar beam.

So you can detect a radar-guided missile because there is active radar illumination of the target aircraft. You can detect a heat-seeking missile the same way because it is passive and looks at the heat the aircraft emit by itself.

You can have a system on the aircraft that tries to spot a missile regardless of the guidance system. They do not detect a missile that has locked onto you but look for a missile itself by detecting the IR or UV light the missile's rocket engine detects when it is launched. That is like if the pilot looks out of the aircraft and sees the missing getting launched but in a different frequency.

You can also have radar on the aircraft that detect enemy missiles by sending out microwave and there it getting reflected back

Missile launcher warning system is newer technology then warning for radar locking

You can have a radar-guided missile that uses an enemy radar and fly towards it. It is used to attack ground-based radars for air defense systems but to my knowledge not against enemy aircraft. It is relatively simple to defend against, you just turn off your own radar. That is good enough against the air defense system because if they can see you they can't fire at you, that is like they were not there in the first place. It is not that useful against an aircraft, a attack aircraft can still fly with radar off to the target.

So you can get a missile launcher warning for any missile type but only a missile lock warning for radar-guided missiles.

Neatsick video of a dude dodging missles

sick explanation of that video

depends on the missile. For a heat seeker, no you get nothing because there is no way to know. A heat seeking missile is totally passive.

For radar guided missiles you do get some warnings. The plane that is being attacked has radar detectors that let the pilot know they are getting hit by radar. Now it's important to know that all radars are going to be a bit different. i.e a search radar vs fire control radar, vs the missiles own radar, assuming it has it's own not all do, look different to the detector. Fire control radar and the missiles own radar are what is actually used to guide the missile in for a kill. So when the plane is getting hit by fire control radar or the missiles radar you will get an alarm telling you that. These warnings do not necessarily mean you have been shot at, only that the attacker has you locked up and can shoot at any moment.

1. Neurology is a branch of medicine that deals with the nervous system. Psychiatry is a branch of medicine that deals with disorders of “the mind”. If that sounds vague, it’s because it is. Generally, personality, behavior, mood, psychoses, and things in this nature are historically managed by psychiatrists. Are there grey areas? Sure. As things become better known in etiology, we may find more organic causes for diseases. For example dementia is studied by neurologists and psychiatrists. In general, psychiatric disorders are more inclined to have multifactorial, social, behavioral, or unknown causes than neurological disorders.

2. Psychiatrists are, as mentioned, medical doctors. So if there is a medical or organic issue, psychiatrists are trained to deal with them and can provide medical treatment. This is as opposed to psychologists who are not medical doctors. Clinical psychologists study psychiatric disorders, and usually can help with non medical management of these disorders. For example, if someone needs therapy, a psychologist could help. If they need medication, usually a psychiatrist will help. So the fact that a psychiatrist manages a certain disease or not may not be as important as which specialty trains people for managing that disease. For example, back pain might be managed by orthopedics, neurosurgery, or rheumatology. But if in some country, one specialty is trained to manage back pain more than the others, that’s the one you should go to first. It doesn’t matter that much how we think it should be categorized. It matters who knows most about it.

3. ADHD may very well have a neurological basis. As one of the comments points out, many psychiatric disorders may very well have a neurological basis. But are we there yet? Probably not. ADHD may still have other components to it, so categorizing it with things that psychiatrists manage isn’t very out of place.

In the US, when you get board-certified for psychiatry or neurology, you get certified for the other as well due to the huge overlaps in diseases and treatments. Some neurologists do treat adhd, but most focus on seizures, migraines, dementia, strokes, etc. Some psychiatrists will treat the same disorders but mostly focus on anxiety, depression, etc.

ADHD might be caused by a difference neurodevelopment, but the symptoms you see the doctor for are behavioral (executive dysfunction, inattention, hyperactivity, troubles focusing, etc.) These symptoms are common across many psychological and mental disorders and there is no diagnostic test to measure if your brain is simply "wired differently" or if your inattention is because you're struggling with depression or insomnia. Diagnosing and treating ADHD takes somebody who is skilled in assessing someone's behavior and mental process for an underlying cause/reason (i.e. a psychiatrist.)

Simple answer is. Neurologist are treating ADHD patient but because of the complexity, there is no one method that works for everyone. While there is no cure for ADHD, there are treatment options available to successfully manage symptoms and improve your child or teenager’s functionality in his or her daily life. And depending which path you choose you will look for different types of experts (Medical or Behavioral Therapy).

Personally I was treated by a neurologist for ADHD from when I was 9 until I was 18 (where I no longer was seen at the children’s hospital and instead had to see my family doctor for medication and a psychologist for extra help). I was surprised when I found many Americans are treated by psychologists even as children. I’m no expert on this but I’m now wondering if I was ever supposed to be treated by a neurologist? I’m confused now!!!!

edit: I live in Canada fyi

I've actually developed loading bars for applications before.

99 times out of 100 a loading bar is set by dividing the number of tasks to accomplish by the number of tasks already accomplished. Rarely is there any consideration to the length of time it takes to do a task. If there is, it's a best guess. Not many people want to pay for time studies to get it to be a realistic loading bar. They just want a notification of progress so they don't think the application is frozen.

Just for kicks and giggles. I have done a time study on an application loading and normalized the loading bar to be fairly accurate as a countdown. On the computer I was developing with. I transferred the application to a user's computer and it was way off. (Maybe my HD was fast or slower than the user's, or their network connection was flaky. Who knows. There's a million reasons).

Not saying you can't figure it out, but no one is going to pay a developer to do it.

You shouldn't really listen to anyone here. The answer is that it's implementation dependent. Maybe the engineer wrote it so that there are four steps of 25% each. Copying files is maybe step 1 and is super fast. Step 2 is a big database operation and is slow... etc. Maybe the steps are totally fake. Maybe there is a simple timer that moves the progress up 10% every second until 99% where the last percent is actually dependent on something.

Its completely unique to the person who programmed it or a commonly used installation software.

Basically, the computer has no idea how long it's going to take. It knows there is X number of steps and how far a long It is for each individual step and its going to try and predict how long it's going to take based on the information it been given by the dev inatally.

There might also be a psychological explanation as well but I'm not sure

Edit: tom Scott explains it so much better

Computer aphorism: The first 99% of the install takes 99% of the time. The last 1% takes the other 99%.

That first 90% is you dumping a moving box all over the floor

The last 10% is putting everything away nice and neat

Basically, just in case. There's no other reason. Moderna could set their dose at 30ug (probably even lower) and it would work - they just didn't know that at the time so they wanted to play it safe instead of flopping.

MRNA chose 100ug based on an early study. Later results showed their lower doses worked fine but the phase 3 was already designed.

MRNA vaccine had more adverse effects than PFE- Id guess because of the higher dose. But apparently there’s a non linear relationship between your immune response and the initial bolus- at some point it capped out.

Moderna early reports: https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-positive-interim-phase-1-data-its-mrna-vaccine

Edit: interesting pre print https://www.medrxiv.org/content/10.1101/2021.03.06.21253058v2.full.pdf

Even 1ug dose x2 of pfe had comparable lab markers of immunity to a single 30ug.. and 10ug x2 was comparable.

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Short answer. They arnt the same.

Technical answer. Even though they're both "messenger RNA" vaccines, and this sounds the same its not, there from the same family line, but far enough apart to have noticeable differences, mainly in the delivery system which is a fat which contains the mRNA and is susceptible to temperature. Hence why the Modena vaccine doesnt need super cold storage, the Pfizer does. Modena have (total guess) worked out a way of keeping the fatty substance viable at higher temperatures by changing the quantity.

Ideal locations for geothermal power are those where you can easily reach the target temperatures (50 - 150 C depending on the type of geothermal power plant) at relatively shallow depths. This essentially means that an ideal location is one where the geothermal gradient is relatively high in the shallow crust. Generally, geothermal gradients are higher in areas with active deformation and/or volcanic activity. If you look at a variety of efforts to map geothermal potential, e.g., these global map from Coro & Trumpy, 2020 or these maps for Europe from Limberger et al., 2014, you'll notice that the correlation between high geothermal potential and locations of active tectonics / volcanism is pretty good (though in the case of Coro & Trumpy, this is kind of baked in as they're taking a machine learning approach and using earthquake activity as one of the datasets in their model).

Getting back to the question, theoretically you could build a geothermal plant anywhere because if you drill deep enough, you will get to your target temperature. However, there are significant differences in the depth you need to drill and thus the cost. As a trivial example, if we assume we need to drill down to a depth where the crust is 100 C, this requires very different amounts of drilling if you're in a place with a relatively high geothermal gradient of ~50C/km (so 2 km down) vs someplace with kind of the global average of 25C/km (4 km down). The Limberger analysis is useful because they go through the economics and highlight that in most cases, the cost of drilling increases non-linearly with depth (i.e., costs increase rapidly as depth of the well increases). More generally, the economics are a critical component because no one is going to expend the (significant) cost of drilling geothermal wells and building the plant itself if the cost cannot be recouped (and make a profit) by selling power over the expected lifetime of the plant. The Limberger paper considers a lot of the details and is quite useful for thinking about all the considerations going into whether a location is feasible, now or in the future, for geothermal power.

In short, you could build a geothermal plant anywhere, but it's really only economically viable in places that have moderately high geothermal gradients, which tend to be tectonically or volcanically active locations. Much of this is driven by economics, so as power becomes more expensive and/or technology makes it cheaper to produce geothermal power from lower temperatures, the range of locations where you can build an economically viable geothermal power plant would expand.

Great explanation about the geothermal gradient by u/CrustalTrudger. In conventional geothermal systems, you also need fluid and/or steam to spin a turbine. Porosity/permeability and fluid play a huge role as well as just heat.

Tons of geothermal exploration wells have been drilled into hot dry rock, but the absence of any fluid flow usually proves the well a failure.

The most productive fields today are extremely hot (600°F), and have either a porous reservoir or extensive interconnected fracture network, and fluid.

Enhanced Geothermal Systems (EGS), which attempts to use hydraulic fracturing to stimulate a reservoir, has yet to be successfully implemented on an economically viable scale. It's a promising idea though. Hypothetically if you had a good geothermal gradient, you could create your own system and boom, megawatts.

Essentially yes, geothermal can be constructed anywhere. It isn't necessary to build geothermal in tectonic or volcanic areas since you can build geothermal power that uses a thermal exchanger to vaporize a low boiling point fluid and spin a turbine e.g. 75C works iirc. That means the temperature of the water below doesn't need to be very hot. It's also an earthquake/ eruption hazard to drill and especially fracture or enhance your well by pumping water back underground at volcanic or fault line sites making them often a point of political deadlocking.

When picking sites groundwater flow should be considered. Since for bigger diameters bore holes and for deeper wells (increased pressure) you get more flow to exit the well, you can therefore adjust the output power level by drilling wider or deeper. But if you build a well that depletes the thermal groundwater resource then a new lower subterranean hydraulic equilibrium could take hold and reduce your power extraction permanently. A good target location takes into consideration watershed not just temperature gradient so that output will be sustainable.

Also, a great number of acids and chemicals come up from deep groundwater. One of these is valuable, methane, aka natural gas. The way natural gas is extracted is from high pressure ground water and that is similar to boring a geothermal well. Also importantly natural gas occurs at a depth where the earth's temperature warms the extracted water enough to extract heat using a thermal exchange fluid. The opportunity to combine natural gas extraction projects with geothermal energy extraction was noted in MIT's study of geothermal development. This means good geothermal opportunities can also target natural gas sites. (find the MIT report at this link MIT-FutureofGeothermalEnergy)

In Iceland, they are experimenting with drilling a super deep hole towards magma where water is >400C in a state called supercritical. This technology is experimental and stands to evolve geothermal technology but to my knowledge it is not operational let alone widespread. If it became very effective then supercritical geothermal would target specifically volcanic sites to get close to magma while only drilling 10-15km deep (continental crust \~30-65km).

It is possible in regions without volcanic or tectonic activity.

My house is heated with geothermal power and I'm liviving in the east of Munich, Germany. We have absolutely no volcanic or tectonic activity here. Next sites I know of are in northern Italy or in mid-west Germany. Both several hundred kilometers away. I might also add, that there are several geothermal powerplants in my area and there are plans and to build even more.

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Early ones were really simplistic and just pointed the missile to the hottest thing it sensor could detect, be that a planes exhaust, the sun or flares (decoys). They had limited steering ability and only worked when shot at a plane from behind it (called "rear-aspect"), and even then weren't that reliable.

Modern ones are much much more sophisticated. They have high-resolution infrared cameras, can detect and track planes from all angles, ignore flares, plot efficient intercept courses, are much more manouvrable and fully integrated into the planes targeting systems.

A modern AIM-9X for example can be given targeting data from the planes radar or helmet mounted sight prior to launch and can track a target up to 90° to the sides (of boresight), allowing pilots to shoot at targets without having to point their own planes nose even close to it.

One thing usually gotten wrong in movies is that most missiles, including many if not all heatseekers, have a rocket engine that burns only for the first few seconds of flight. Hence, kinetic energy of the missile starts getting lower once the engine shuts off, and the missile is less maneuverable and therefore has a lower chance of hitting a maneuvering target at longer range.

Therefore, maximum range and maximum effective range can be quite different. Some missiles do have sustainer rocket engines to maintain propulsion over a longer period of flight but I can't think of any heatseeker missiles with sustainerers.

I still haven't seen an explanation of the "heat-seeking" logic of the problem that I really like so here's my attempt.

Starting with the old IR (infrared) missiles it's fairly simple. If you take an IR camera and point it at the back of an engine it there will be a very obvious hot spot. (https://youtu.be/2C6ZcqeIvjw). Because the difference in temperature between the engine/its exhaust and the environment is so large its easy to identify that as a targeting point. That is why the earliest missiles could only be fired from directly behind the target where they could see directly into the engine where the largest temperature difference would be. Then versions were made where they could detect the difference using just the exhaust instead of the engine core which greatly expanded the angles they were usable from, but still weren't effective if the exhaust was out of line of sight.

Flares exploit the simplistic nature of this temperature difference logic by creating a larger temperature difference so the missile tracks them instead. To combat this engineers changed what the IR camera is looking at essentially. With better sensor technology the missiles no longer look at just what is the brightest thing in the field of view, instead they look for airframe heating. As a plane flys it encounters air resistance which is essentially friction between the plane and the air. That friction heats up the plane (this is part of why the fastes aircraft require special materials). The temperature difference between the friction heated aircraft and the rest of the sky is measurable but still fairly small. There can certainly be other things in the missiles field of view that have a larger temperature difference, so the missile has to know what it's looking for. To solve this these missiles have a form of image recognition built into their computers so that they can recognize aircraft shaped temperature differences and target those specifically. That makes it much harder for flares to fool these missiles while also allowing the guidance computers do a better job figuring out where the target is going so the missile can get there first.

Others have covered this in other ways but "Do they work exactly like in the movies?" No. If a missile goes past a target will it turn around to try again? No, at that point it has been defeated. Will a missile chase for over a minute while right behind a plane very slowly getting closer? No, most missiles travel far faster than the aircraft they're targeting and aren't going to slow down to give you time to think. Can you out maneuver a missile? Yes... But it's very very rare and will usually leave you in a very vulnerable position to the next missile. There are methods to reliably defeat missiles, but that isn't one usually.

When in doubt, assume the movies are portraying everything incorrectly.

In this case, the big difference between the movies and real life is that missiles are wildly faster than planes. The classic visual of a pilot frantically dodging while a missile follows just on their tail is nonsense.

As Scott O’Grady pointed out, they are much, much faster than depicted in movies. Like no time to react at all fast and one nailed him brought the plane down.

My mum has got ALS and as she’s losing her speech we recently digitised her voice so she can talk through that in the future.

All she had to do was record 60 sentences with a budget microphone, send it off and a few days later they sent back her digital voice file and now when she typed anything it talks like her.

There are several ways this is done. I worked in a commercial system in the early 2000s but not a whole lot has changed since then. Your idea is one of the more popular ways of producing natural sounding speech. A large amount of audio is recorded by a single speaker, and then chopped up into tiny bits and then put back together in different combinations. Older systems like this would use full phonemes (the basic sounds of speech) like the “s” sound combined with the “e” sound to make the word “see”. This was unnatural because there’s always some mismatch at the start and end of the sounds. By cutting the recordings into smaller pieces the speech can be made more natural sounding when it is put back together. This process of cutting up the recordings takes a lot of time although it can be sped up by using machine learning and speech recognition techniques with some human intervention. We needed about 6 hours of quality recordings including all possible sound combinations multiple times to make a new voice. Less than that would work but 6-12 hours would give the best results.

There are other ways of producing speech that involve mathematical models of the human speech system. This is how some of the earliest computer speech was produced in the 70s and 80s, but it is less natural sounding (like the speech synthesizer that Stephen Hawking used)

Finally more recently there are AI/machine learning generated voices that use neural networks or other “deep learning” techniques to generate the speech sounds.

All of these techniques can be combined to make very good sounding voices these days. When I was doing work in this area some of the biggest challenges were around making the tone and cadence of the voices more human-like. We are still not all the way there but I am really impressed by the progress that has been made even in the past few years.

A friend of mine is a voice over artist that has done work for GPS systems and automated banking hotlines. She told me they recorded her saying every letter of the alphabet, many variations of vowel sounds and common key words and phrases. Skynet does the rest...

I saw an article some years ago who interviewed the woman who provided the voice for Siri, and she said that at the time she didn't even know it was going to be for an AI, and that they basically just had her make a lot of sort of "nonsense" noises that were pretty much broken down words/syllables.

Because there was so much she did it for a while I'm pretty sure.

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This is a very complex issue with no clear answer. The half-life effect is still the case but this just says that memory cell pool against any specific pathogen will slowly (it varies) decrease over time but it doesn't say how. Some times this decrease still means protection over decades which practically means lifetime, some times it is a few years with varying levels of protection.

Though there is a lot of research for that, there is no definite answer of even why some pathogens (or vaccines) tend to induce a more long lived or effective memory pool than others.

Tissue residency, combinations of surface markers, cytokines, expression (or non expression) of specific transcription factors all play a role in how the half life of memory T and B cells works over time. And although you can find research that may suggest one mechanism or another or build upon a previously suggested mechanism, there is no definite universal answer AFAIK.

I would second /u/kd-_ 's answer and add: There definitely isn't a super clear answer yet at the detail you might want - part of the difficulty is that the answer is "lots of things."

Amount of virus/bacteria at the time of infection, length of time of infection, general immune state of the individual, other cell types present at the infection, age, maybe sex, if there is a second infection (whether the host knows it or not - this is why we get boosters, the second infection makes memory cells last longer), TCR binding affinity... it's a ton of different things.The answer definitely lies in part in transcription factors - especially FoxO1 for long term memory ("central memory" T Cells) - but what specifically causes some T Cells to ramp up FoxO1 expression vs. other transcription factors that would make them cytotoxic and short lived (e.g. Blimp1, Tbet, Eomes) aren't clear in every case. This is a pretty good review on the topic if you want specific cytokine signaling pathways in the body that effect specific transcription factors and protein expression in T cells.
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At a more conceptual level: the half-life answer is correct. Even memory T cells undergo apoptosis over time, and there is a stochastic decay of memory pools (stochastic might just be a fancy word for "we don't know exactly when/why"). You can lengthen the half life in mice by injecting certain cytokines - but these carry unacceptable side effects in humans, it's really artificial and not relevant to actual medicine.What is relevant to human medicine is that reinfection with the same virus causes an increase in the size of the memory pool and extends the half life - this is why we give booster shots.

Conceptually, the immune system builds up a memory pool after the first infection (or vaccination), but seeing that infection a second time (or receiving a booster) tells the immune system that this is going to be a recurring problem, better create a lot of memory cells and keep them around for a long time.That's why the mRNA vaccines require boosters shortly after the first shot - it bolsters both the size of the memory population and will make it last longer. Doing this multiple times in succession stops helping more, and doing it too many times is actively harmful (T Cell Exhaustion). If you wait years between boosters, you can probably avoid exhaustion, while still expanding the memory pool.

A lot of the people saying we'll need boosters for COVID [at X time] are 1) pharmaceutical companies or 2) not looking at (or spoke before) the recent data for mRNA vaccine protection against variants. We don't know how long COVID protection will last from these vaccines - mice only live 2 years, and it's not that every process happens at 40x speed of a human, so if an mRNA vaccine gives a mouse 2 years of protection that isn't a guarantee of 80 years in humans. This will need to be determined empirically, we don't have a set rule for how long immunity lasts for mRNA vaccines in general, let alone specifically for these vaccines (as there will definitely be some variability between mRNA vaccines - different peptides generate different strengths of immune response, which is a very active area of research currently).

So we may need boosters in a few years. Option 3) is scientists being cautious, and preparing us for a real possibility. Perhaps COVID immunity from mRNA vaccination only lasts for a couple of years. Perhaps some variants will evolve to evade mRNA vaccine immunity - there's certainly going to be a very strong selective pressure for SARS-CoV-2 to mutate to avoid mRNA vaccine immunity, as billions of people will have that immunity and be hanging out maskless indoors very soon. Perhaps "need" is too strong of a word and people will want them (I will take one in a year or two if they offer an mRNA cocktail containing a few variant Spike sequences). And I don't have the data to back it up, but people who got Adenovirus-based vaccines are going to want a booster in a year or two if they want to maintain their immunity.

So this is a different angle than you were asking, but: Epstein-Barr virus apparently persists by making B-cells it has infected persist.

We propose that EBV indiscriminately infects B cells in mucosal lymphoid tissue and that these cells differentiate to become resting memory B cells that then enter the circulation. Activation to the blastoid stage of latency is an essential intermediate step in this process. Thus, EBV may persist by exploiting the mechanisms that produce and maintain long-term B cell memory.

Courtesy of last year’s reading up on human herpesvirus persistence strategies, and that was the coolest one.

There are different types of memory cells, each with varying homing properties and degrees of 'stemness'.

It is important to understand that when an adaptive immune response occurs, what's happening is that the relevant naive or pre-existing memory compartments aren't just being activated, but actually differentiating into an effector phenotype aimed at clearing out infected or aberrant cells, and that these have a pretty short lifespan (a few weeks). Meanwhile, however, a subset of these activated cells differentiate into or remain in a self-renewing memory state and localize to 'home base' (typically the lymph nodes or spleen - making them hard to detect in the blood). These are generally referred to as central memory cells but, in recent years, another memory subset of T cells has been characterized (called Tscm or stem-like memory T cells). These cells are rare but are extremely long lived and proliferate quite explosively when simulated with their antigen.

The overall point here is that memory cells bear a lot of similarity to how stem cells work and are generally a small population of self-renewing cells that are retained long after the proliferative burst that happens during the course of a memory or "recall" response. Individual memory cells have a limited lifespan but they are able to self-renew so that the repertoire at-large remains poised to react to threats it has seen before.

What dictates whether or not people need booster vaccines for some pathogens and don't need them for others is, as others have said here, is largely unpredictable at this time. I'd speculate that the main differences lie in the conditions of an infection or vaccination and how efficient they are in inducing activated T or B cells to differentiate into memory phenotypes. This could include factors like the cytokine context (which would be influenced by the adjuvant cocktail in the vaccine or by how the innate immune system is reacting to the pathogen) or the potency of the individual antigens responsible for driving responses.

If you want to add another layer of complexity to the "we're not certain how this works" game: Measles virus is now known to destroy immune memory for other infectious agents, making people infected with measles more susceptible to opportunistic infections and death even months post-measles.

The mechanism is suspected to be killing plasma cells in the bone marrow, but that's not 100% confirmed.

https://www.nature.com/articles/d41586-019-03324-7

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Our body feels a feeling when its nerve receptors are triggered the way it is supposed to be triggered. Tiny hairs in our respiratory tracts are designed to trap foreign bodies and make us feel them so that we sneeze and push them out. For this our body inhales a lot of air so that it can exhale it all together forcefully in order to dislodge the particle and spray it outside which is basically what sneezing is. When you are about to sneeze and you don't, which is probably because these processes are somehow interrupted, maybe because of not inhaling a lot of air and holding it (what women do to silence their sneeze)...or maybe because the particle dislodged itself too early... In all the cases, the stimuli that triggered the response is still there, which continous to irritate you the way that it did, but if you were to sneeze properly when you were supposed to, the sensation would have disappeared. That is why starting to sneeze and not sneezing feels more uncomfortable.