1/ Automobiles and Intake Fraction. Since cars are back in the news I thought I would retweet this model result I offered in early April 2020. I focused only on 1 micron particles & accounted for windows completely closed & cracked slightly open.

2/ Related air exchange rates were based on experimental results in literature for mid-sized sedans. Particle deposition to indoor surfaces were accounted for, as the surface to volume ratio in a 3 m3 cab is large. An important outcome was the intake fraction (IF)
3/ Here, IF is the number of particles (or virions in collective particles) inhaled by a receptor DIVIDED BY the number or particles (or virions in collective particles) emitted by an infector.
4/ Integrated over the two hour drive (in this example) the IF for all windows closed & a receptor at rest is 0.08 (8% of what comes out of the infectors respiratory system ends up in the respiratory system of the receptor). 8%! That is a very high intake factor.
5/ With additional ventilation from cracking a window open drops the IF to 0.012 (1.2%) still relatively high. Can get lower by opening more windows.
6/ An important point is that the intake fraction is not dependent on the amount emitted, and so the value is applicable to whatever the number of particles (or virions in particles) are being shed by an infector. Emission rate can be multiplied by IF to get at inhalation dose.
7/ In this analysis the IF ranges from approx 0.01 to 0.1. For a wide range of indoor spaces in buildings IF ranges from 0.0001 to 0.001. Intake fraction can be lowered w/ higher ventilation and/or better filtration (including portable HEPA filters), as well as UVGI for virions.
8/ Note that for large outdoor sources of pollution (think busy highways, power plants) with a receptor on the order of hundreds of meters to kilometers downwind the IF is typically on the order of 1 billionth to 1 trillionth.
9/ For the very special case of an inert pollutant (non-reactive and not removed by controls or surfaces) at steady-state IF = respiratory minute volume / volumetric flow of outdoor air through indoor space. IF = Qb/Qv
10/ I am working on a blog related to the use of intake fraction as a conceptual and quantitative tool for assessing indoor environments where exposure to SARS-CoV-2 may occur.
11/ Until then, I have posted some old handwritten course notes on intake fraction at https://t.co/iKuCeJKsrt

Apologies for sloppy writing. Enjoy the analogy of candles vs power plants in terms of inhalation of fine particles. Candles 👎. I know, different compositions.
12/ Also, if everyone in the vehicle wears masks the intake fraction is reduced on two fronts, less emissions from the infector and less inhalation of virus-laden particles by receptor. To be included in blog. Just do it!

More from Science

1. I find it remarkable that some medics and scientists aren’t raising their voices to make children as safe as possible. The comment about children being less infectious than adults is unsupported by evidence.


2. @c_drosten has talked about this extensively and @dgurdasani1 and @DrZoeHyde have repeatedly pointed out flaws in the studies which have purported to show this. Now for the other assertion: children are very rarely ill with COVID19.

3. Children seem to suffer less with acute illness, but we have no idea of the long-term impact of infection. We do know #LongCovid affects some children. @LongCovidKids now speaks for 1,500 children struggling with a wide range of long-term symptoms.

4. 1,500 children whose parents found a small campaign group. How many more are out there? We don’t know. ONS data suggests there might be many, but the issue hasn’t been studied sufficiently well or long enough for a definitive answer.

5. Some people have talked about #COVID19 being this generation’s Polio. According to US CDC, Polio resulted in inapparent infection in more than 99% of people. Severe disease occurred in a tiny fraction of those infected. Source:
All modern research questions frame your mindset and self-frame research paradigm. Broad thinking: how little of everything can a citizen survive on; how cheap can your upkeep be? /1


When an American patient lands in an Austrian hospital for a back problem, a doctor tells him to perform a set of exercises.

- How many?
- Do you have anything else to do? /2

This interchange illustrates two mindsets colliding at bedside. How little can I get away with vs there is no limit to effort when it comes to your wellness. /3

When you were robbed of movement, somebody started selling you exercise. To understand that digging a ditch, to build a house, or to carry a child around, or waking to your grandparents for an hour is not the same as jogging on a treadmill... will reveal what research hides.
/4

When I talk about doing a purposeful activity outdoors, I look at complexity of movement, purpose, meaning, sun, and air, even an opportunity to meet a neighbor... that is now reduced to a calcium pill, vitamin D, an antidepressant, an osteoporosis shot, and an oxygen tank. /5
This is a thread on statistics in science: 1/7 (via @LogicofScience)

Basic Statistics Part 1: The Law of Large Numbers https://t.co/wUH8eAAIak

#Science #Statistics


Basic Statistics Part 2: Correlation vs. Causation

https://t.co/Azhyl8pDsX (2/7)

Basic Statistics Part 3: The Dangers of Large Data Sets: A Tale of P values, Error Rates, and Bonferroni Corrections

https://t.co/LetN6aEBRM (3/7)

Basic statistics part 4: understanding P values

https://t.co/K8MMMgTCOf (4/7)

Basic Statistics Part 5: Means vs Medians, Is the “Average”

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