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One of the things that made human cities unhealthy until modern times was that they didn't have a good system for getting poop away from where people lived. Bats don't have sewers either, so their poop (and any pathogens it contains) stays where other bats can easily come in contact with it.

That would make sense if they were talking about animals that could be domesticated. It would be pretty hard to domesticate whales. If you did, you couldn't use them for farm work or transportation, the way you can with horses, cows, or llamas. You couldn't get wool or milk from them, like you can from sheep.

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Do you work in this field of study?

So if I understand the abstract from the PCDH19 link, the problem isn’t heterozygosity on a cellular level, so much as random X-inactivation causing regions of incompatible homozygous (hemizygous?) cells. Is that correct?

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What's your opinion re: Kitum cave on the exposures to Marburg and Ebola Zaire?

The studies I'm aware of mostly discuss the area northwest of Lake Victoria.

We don't have a full understanding of all the processes involved in lightning formation, but the basics are that a large voltage or potential difference forms between cloud to cloud or ground. At a certain voltage, gases will enter a phase called electrical breakdown, which for air at atmospheric pressure is around 30 kV/cm. This is where the fun begins.

When electrical breakdown occurs in a gas, a chain reaction can form. Free electrons will be accelerated by the large voltage (I use voltage and electric field interchangeably from here on out, apologies if that's confusing, i was too far in and im too lazy to go back and edit) and will eventually collide with another particle in the gas. If the electron gains enough kinetic by the time it collides with that particle, it can ionise it, releasing a 2nd electron, which along with the initial first electron will be accelerated by the electric field. This process will repeat itself over and over again causing the number of free electrons and ions to grow exponentially, forming a conductive channel that propagates through space. This model works well enough at low pressures that you might find in a vacuum chamber but it's not so great at higher pressure like 1 atm. Why? Well because at low pressure there isn't a whole load of particles, so there isn't a whole load of collisions between particles, and therefore there isn't a whole load of energy transfer. This isn't the case at atm.

The next thing to add to the model is the large relative mass difference between electrons and every other particle in a gas. An electron is about 2000 times lighter than a neutron or proton, and as a result will gain a lot more velocity than say an ion of oxygen or nitrogen for the same electric field. This means that a localised charge distribution can form.

(Cavaet: This is where the understanding of lightning formation and propagation sort of becomes less understood and there are several theories. I'm going to stick with the one I'm more familiar with through my own work and research)

The charge distribution looks like a finger and depending on the orientation of the electric field the tip will be electrons or ions. In most lightning cases, it'll be electrons leading, as ground will be positively charged relative to the cloud. Here's a link that hopefully shows it Streamer discharge

In front of this charge distribution, more localised ionisations will build up pulling the streamer forward, towards ground, in a similar way to the avalanche breakdown, although the exact mechanism has several theories such as x rays, electron collisions and strong local electric fields. In all likelihood it's a combination of all three, plus several other factors.

The streamer will continue to propagate until it gets close to ground. At which point an even larger electric field can form due to the combination of negative electrons in the streamer and positive charge at the ground, with the field strength being the largest at higher points. If the new large field is strong enough, a secondary positive upward strike can also form. The upward strike is generally a lot hotter and more powerful than the downward strike, due to ions having a lot more kinetic energy than electrons. It's been a while since I've done any work in this area.

This is why you never want to stand under a tree or in open space and get as low as possible during a lightning strike.

So this streamer model that I've described has a few flaws. The most obvious one being that streamers only really work over short distances, around a few centimetres. Other models such as the leader model exist which try to explain the more large scale properties of lightning. It doesn't take into account the distribution of gas particles in the atmosphere, we know there are various layers etc. and has no chemical input. Plasmas like lightning will generate different oxygen, nitrogen and hydroxyl particles, like ozone or OH. In the past, I did a bit of theoretical work on what sort of impact OH would have.

A recent study that came out around Christmas proposed an oxygen meta state that could theoretically allow charge transfer but I haven't had a chance to fully look over it.

A complete picture of lightning would be either a simple model like the streamer model, or a very complicated physio-electro-chemical model. I'm happy with the streamer model for now :)

Yes, this study makes the point better, although it's still small (n=8 homozygotes), and relies on retrospective analysis of clinic records.

Based on that study, it does look like there could be faster progression in homozygotes, although I don't know if there's enough data to argue that the normal allele is specifically conferring an advantage, as opposed to simply a dose effect of having 2 copies of the mutant allele.

It's also worth noting that not all studies show this same trend. For example, a 2019 Neurology study (https://n.neurology.org/content/neurology/92/18/e2101.full.pdf), which was somewhat larger (n=28 homozygotes) and used patients who are part of the EHDN Registry Database (ie using standardized data collection protocols for clinical data) did not see a difference in disease progression between homozygotes and heterozygotes.

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If you are at all interested in how frequent earthquakes are around the world then you can use an app that actively notifies you of seismic events as they happen and shows past events. I have family in Japan and I use one to keep track of any new events there. Having been in a few earthquakes myself in Greece, Japan and Spain I kinda got hooked on tracking world events too.

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You are right. In this case, however, the sickle-cell allele is the one that confers the advantage.

And munchkin cats are exactly the same. Mm is munchkin, MM is stillborn.

Yes, there are flaws with the article I referenced. There are other articles that suggest a more negative clinical course for homozygotes.

Squitieri, F., et al. (2003). Homozygosity for CAG mutation in Huntington disease is associated with a more severe clinical course. Brain, 126(4), 946–955. https://doi.org/10.1093/brain/awg077

This was the first thing I thought of. Another good example is a specific gene for hairlessness in dogs. It's dominant, so Hh would be hairless, but HH zygotes don't make it to birth.

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/U/Tus3 was asking about underdominance though, and the examples on the Wikipedia page

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