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Joshua C. Agar Profile picture
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8 Jan, 21 tweets, 9 min read
Admittedly there's a research gap concerning face shields since they are mainly intended for hospital settings, hence scenarios limited to hospital settings. The general consensus is that face shields are intended for ballistic droplets, not for aerosols.

Below are the studies:
Lindsley et al. (2014). Efficacy of Face Shields Against Cough Aerosol Droplets from a Cough Simulator

Face shields are evaluated to stop the initial impact of the cough which brought heavy droplets, however, airborne droplets still make way around.

ncbi.nlm.nih.gov/pmc/articles/P…
Akagi et al. (2020). Effect of sneezing on the flow around a face shield. Phys. Fluids 32. doi:10.1063/5.0031150

A numerical simulation of a sneeze on a face shield, showing that transient effects actually directs aerosols inside even during impact.

aip.scitation.org/doi/10.1063/5.…
Pan et al. (2021) Inward and outward effectiveness of cloth masks, a surgical mask, and a face shield, Aerosol Science and Technology, 55:6, 718-733, DOI: 10.1080/02786826.2021.1890687

Face shields are rated as the poorest protective layers.

medrxiv.org/content/10.110…
Salimnia et al. (2021). A laboratory model demonstrating the protective effects of surgical masks, face shields, and a combination of both in a speaking simulation

An experimental study evaluating little to no contribution of face shield.

pubmed.ncbi.nlm.nih.gov/33485923/
Bagtasa (2021). Efficacy of face shields to ambient aerosols in local indoor and outdoor setting. 2021: Proceedings of the 39th Samahang Pisika ng Pilipinas Physics Conference

Evaluating that face masks are the ones doing the work, not face shields.

proceedings.spp-online.org/article/view/S…
Wendling et al. (2021) Experimental Efficacy of Face Shield and the Mask against Emitted and Potentially Received Particles, J. Environmental Research and Public Health

One of the flawed studies conducted by medical professionals. Fails on equipoise.

pubmed.ncbi.nlm.nih.gov/33671300/
A visualization of TU Delft shows what happens to the emissions in the first place when the face masks are interfering:

If the face mask are already directing the emissions to the sides and the back instead to the front, what's the use of Wendling's setup?
Verma et al. (2020). Visualizing droplet dispersal for face shields and masks with exhalation valves

A visualization experiment by the Florida Atlantic University showing that face shields are poor source control... They don't stop aerosols at all.

aip.scitation.org/doi/10.1063/5.…
Most of these studies were derived from hospital settings, therefore they perceived sporadic (i.e. cough, sneezes, speaking) emissions as the high risk scenarios, and focused only for that scenario.

Here is what happens at different angles of approach:
If the cough is coming from behind, the wearer of the face shield is practically screwed:
Here is what happens when you walk in an indoor space (close spaces, crowded places) saturated with airborne particles while donning a face shield:
Faster accumulation of airborne particles if you're looking side-to-side while walking:
A face shield provide a place for retention of airborne particles:
If there's wind potentially carrying SARS-CoV-2 coming from behind:
Similar scenario, only at an oblique angle:
As Dr. Jimenez has said, face shields are useless against Covid-19, now that the understanding that it is airborne. When face shields are coupled with face masks, face masks are the ones doing the work while face shields do nothing.

There are in-fact, other atmospheric consequences of face shields that lead to the increase in infectivity of SARS-CoV-2.

This is the extended abstract of the conference paper that I'll be presenting two weeks from now.
If one insist on doing RCTs on face shields in public settings, despite these studies and despite the fact that face shields are physical items, not medicine, maybe for truthfulness sake, include the Pontresina Case
thelocal.ch/20200715/only-…

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More from @JoshuaCAgar

Joshua C. Agar Profile picture
12 Oct 21
And as it turns out, the initiative of exploring the potential for wind power that led to the wind farms in Ilocos Norte...

...came from USAID!

The Marcoses have been consistent of grabbing credit from USAID!

Documentation of the Initiative:
nrel.gov/docs/fy02osti/…
The study of compiling the atlas for wind energy in the Philippines started in 1996. The atlas was finished at 2000:

(Lol. They indeed did GEV analysis and interpolated using the projected wind exposure parameters)
Bangui and Burgos became the ideal locations. Northwind invested on Bangui and First Gen invested on Burgos.
Read 4 tweets
Joshua C. Agar Profile picture
12 Oct 21
Re: Face shields on various scenarios (Another thread)

I was asked, in the spirit of the RCTs, whether I have explored the other scenarios concerning face shields.

Well, yes, I did.
The intervention of face shields against sporadic emissions at different angles of attack was simulated and observed, and as it turned out that the ballistic protection only applies for emissions coming from the front. From other angles, risk increases:

The speed of cough simulated was 50 mph. Here, it was illustrated how the momentum of the emission decreases over distance, while also noting the advection also:

Read 10 tweets
Joshua C. Agar Profile picture
12 Oct 21
Misinformation and falsehoods cascade across three layers:
First is with the perpetrators who spread disorienting misinformation in social media.

Second is with the media on which some are disoriented and pass on the disorientation to the masses.

Third is with the masses.
Indeed, the battleground may be dealing with the source. But the ripples of misinformation still trickled down to its main interest and intended audience: the masses.
Given that the surveys determined that mainstream media are still the main source of information of people, we look at media personalities who package their commentaries, which contained their personal biases, as if those were the news.
Read 6 tweets
Joshua C. Agar Profile picture
11 Oct 21
Debacle of face shields in the Philippines

(A thread)

I see that some of the scientists from other countries are considering recommending face shields to be worn in public.

I beg to differ, presenting how face shields represented the poorest pandemic response in the world.
December 11, 2020

The Inter-Agency Task Force (IATF) against Covid-19 of the Philippine Government, through its Resolution no.88, mandated the use of face shields even in public, outside of hospital settings.
pna.gov.ph/articles/11544….
The technical advisory body of the IATF, spearhead by infectious disease experts Dr. Anna Lisa Ong-Lim and Dr. Edsel Salvana claimed that a randomized control trials (RCT) conducted in the public hospitals and another performed in India reported 90% efficacy rate.
Read 31 tweets
Joshua C. Agar Profile picture
10 Oct 21
Taytay Chronicles w/ Bayaw Erik
(October 10, 2021)
The dreaded face shield
How to assemble and "use" face shields
Read 12 tweets
Joshua C. Agar Profile picture
10 Oct 21
Kindly ask those "lolo" and "lola" giving anecdotes that "attest" the Marcos regime the year-by-year state of affairs during that period. Ask them the specifics, what specifically happened in '72, '77, '81, '83, 84', and '86.

That's how historiography establishes veracity.
If they can't provide any to establish the veracity of their narrative, then that points of view that they are presenting, like the other dramatis personae in the past making good light of themselves, will be rebuked, shunned, and reprimanded.
You could also ask your lolos and lolas about their knowledge of how government works, the separation of powers, their knowledge of the constitution.
Read 5 tweets

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