Failure to recognise when an aerosol isn't a droplet 26

[LittleInch]

FacEngrPE dropped this in an obscure post and it reads very well.

Basically the whole epidemiological world though various dieses and viruses were spread by "droplets" which landed on surfaces and then infected people or were sneezed at you.

And a lot of times they are probably right.

But there was a magic 5 micron cut off between droplets and aerosols. Why? Read on

https://www.wired.com/story/the-tee...t-helped-covid-kill/?utm_source=pocket-newtab

So is this a disaster - Well you tell me.
But it goes to show that just because a lot of people write something, it doesn't mean that they originally got the wrong end of the stick and then the error repeats itself until it becomes fact.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

Red, the article is about this report:

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3829873

The article is about a woman who was curious about why the CDC and WHO consider airborne transmission occurs in particles between 5um and 100um in size. The woman dug in to the history of it and found that the 5um number was based on an incorrect assumption/interpretation of past research. The past research in fact showed that while particles less than 100um stay airborne, the body is well adapted to filter particles larger than 5um. She concluded that airborne transmission of diseases occurs primarily with particles less than 5um and the CDC and WHO guidelines are wrong. The article also states that she received pushback from the scientific community for making such a claim.

 

[1503-44]

Anna, here's a link to a text copy I saved for you.

https://www.dropbox.com/s/vxpgrza5d...tific screwup that helped covid kill.txt?dl=0

Oh, Tug put another link up too. Let us know if you can access.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[RedSnake]

Okey and Thanks Tug!

And what is the size of a Covid-19 virus?
And what has this to do with the radius, volym and mass of droplets?
Or why it would make the transmission wrong?

/A



“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[Alistair_Heaton]

This volume V surface area stuff is a major driver with bio stuff for those that think Darwin had a clue.

It the reason why cold water beasties are huge and warm water are not so impressive but move twice as fast.

 

[RedSnake]

Thanks 1503-44!

/A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[1503-44]

Welcome. Sorry about the txt file, quick copy paste, but at least you can read that one.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[1503-44]

Moon161 is correct. Sorry I thought otherwise for a moment there Moon.

V 4 pi R^3
__ = _________
A 3 x 4 pi R^2

V/AR = 1/3

If that's true for all spheres, I'm good. Call it what you like. Especially irrelevant.

Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[Alistair_Heaton]

its also a major issue in criticality design in nuke fuel reprocessing I seem to remember

 

[TugboatEng]

The part the WHO/CDC got wrong was droplet transmission. This led to all of the sanitization and the arbitrary 3-6 foot social distancing recommendations. Coughed and sneezed droplets have little time to find their targets (mouth, nose, eyes) before settling on a surface. Even cold and flu virus should be considered airborne. The correct emphasis should have been on ventilation and surgical or better masks.

 

[Alistair_Heaton]

your 100% correct tug.....

but most people are not the same as us...

if you can smell a fart in my book you are breathing in something

 

[TugboatEng]

I know, I didn't want to have to put the masks bit in there but I'm trying to be unbiased in my summaries.

Speaking of masks and efficacy, it's hard to find unbiased studies in relation to SARS but, now that we know the virus is aerosolized, we can find more unbiased studies a our protection against other aerosols such as diesel particulate matter. Interesting, at 70-85% efficiency, they are not considered effective enough.

https://pubmed.ncbi.nlm.nih.gov/23104683/

https://pubmed.ncbi.nlm.nih.gov/27190072/

PM2.5 filter median efficiency only 48% and as low as 14%.

https://pubmed.ncbi.nlm.nih.gov/30308844/

 

[LionelHutz]

I wasn't go to post about it again, but. You insisted on manipulating the V/A ratio into some meaningless ratio in an attempt to prove a point and then you blamed someone else for that ratio. You own Ar/V, as meaningless as it is. Don't be blaming someone else for that garbage.

Sure, mass is important. But, it's not the single thing that is important. Mass is HIGLY dependent on the volume. The ability to heat the mass is HIGHLY dependent on the surface area of said volume. The smaller a round drop, the larger the surface area to volume ratio, and the easier it is to heat the mass.

 

[1503-44]

"Mass highly dependent on the volume."

I'll try to remember that.
Or maybe not.
Thanks


Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[LionelHutz]

So, you actually want to claim you're not trolling and that you're getting trolled when your BS is called out?

The mass of a fixed temperature water droplet will vary directly with it's volume, or in other words the mass varies varies +100% with a +100% change in volume. That's 10X that +10% increase in volume you posted for freezing a water droplet.

 

[dik]

I picked up 200 N95 masks in February of last year... and gave 100 of them away... 50 to the local clinic and 50 to an officer that I flagged down on the street. I had no inkling about how serious the pandemic could be, but wasn't taking any chances.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[1503-44]

Archimedies? You have returned!

No. I have apologised to Moon161 for blaming him. He is as correct as I am.
As for owning a whopper, "Mass highly dependent on the volume." That ugly baby is all yours.
Tell that to a rising fish fart at constant temperature..



Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[1503-44]

Dik, keep them around. Its not over yet.
New Vietnam "UK-Indian hydrid".

https://edition.cnn.com/2021/05/31/asia/vietnam-coronavirus-variant-intl-hnk/index.html

I got Pfizerized 2 weeks ago. Booster appointment on 7 June. I hope these vaccines will hold up against these mutations, but i think its too early to tell.



Statements above are the result of works performed solely by my AI providers.
I take no responsibility for any damages or injuries of any kind that may result.

 

[LionelHutz]

No. I have apologised to Moon161 for blaming him. He is as correct as I am.

He was right and properly explained V/A. You posted a completely wrong turd that makes no sense and has no meaning.

You are pulling the typical BS creating an argument crap. This happens when someone is posting about a TOPIC and writes some info related to it and then someone else feels the need to post stupid irrelevant BS that has nothing to do with the TOPIC just to shove it in the other persons face that this useless information means the info they posted is wrong. However, the info posted wasn't wrong with respect to the TOPIC.

It's also very clear you are trolling the thread with this continuous insistence that the volume to surface area of a sphere = 3.

When the TOPIC is water droplets breathed out by a person in an indoor living or office environment I couldn't give a damn about what happens to a fish fart, or how much the volume of that water droplet would change if it freezes.

 

[dik]

Dik, keep them around. Its not over yet.

I'm well aware of that... thanks. I don't think my supreme being is through 'screwing with the world', yet... as Thomas Hardy remarked, "...as playthings to the gods, they kill us for their sport."

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Eufalconimorph]

So A/V is NOT constant. It's a function of the radius. It's a linear function of the radius, maybe "linear" and "constant" got confused somehow. Either way, you don't get to say that the surface-area to volume ratio is anything other than what "A/V" equals. You can't stick an extra variable there, that's some other value. By that logic everything would be a constant, just shove all the variables to the left side until there's only a constant on the right! If you could do that, you could take the classical driven mass-spring-damper equation mx''+cx'+kx=f(t) and say it's constant, depending only on the particular spring constant chosen: (f(t)-mx''-cx')/x=k. That's obviously false, there are still variable terms in the equation!

Droplet evaporation rate is related to the A/V value. That means it varies depending on the radius. The evaporation rate is NOT a linear function of the radius alone, however, it depends on several other factors (as mentioned, eg temperature, pressure, humidity, purity of the water, etc). Exhaled droplets will be very close to human body temperature to start, so about 37°C. Not freezing, frozen water doesn't matter to this discussion. Likewise the discussion is about normal living environments, so generally between 900-1100hPa pressure, ambient temperature from 18°C to about 25°C (maybe a bit wider or narrower, depends on the particular environment). Relative humidity is the factor that varies the most. At 100% RH, no evaporation occurs for any size particle.