Last week I attended a meeting in Cambridge: the 7th Edwards Symposium – New Paradigms in Soft Matter and Statistical Physics. I even chaired the last session. It attracted a diverse range of attendees. As an example: As head of a research group in my University I am in charge of a £7,000 group budget. A speaker in the session I chaired – Jean-Phillipe Bouchard – is Chair of Capital Fund Management, which controls roughly €7,000,000,0000 of investors money. As I said, diverse range of attendees.
Combining data on the filtration efficiency of masks, with epidemiology studies of mask use
The previous post was perhaps a bit of a moan about epidemiologists and medics focusing on randomised controlled trials (RCTs) and observational studies, to the exclusion of absolutely every other study. This was in the context of using masks to reduce the probability that you catch COVID-19. But moaning is not very constructive. A better approach is to say: OK so epidemiologists are not combining epidemiology data with other data, but there is nothing to stop you doing this. So what can be done if data from epidemiology studies are combined with data of other types?
We all have blind spots, but maybe some are bigger than others
A question for you. It concerns mask wearing to prevent infection with COVID-19. Which do you find the most convincing evidence for wearing an FFP2 mask as opposed to a surgical mask?
- A study of 500 surgical mask and FFP2 wearing healthcare workers in which about 100 of them became infected with COVID-19. In other words quite a small study of people becoming infected.
- Studies of masks that show that an FFP2 reduces the dose by around 95% while for masks it is typically in the range 40 to 60%.
There is no real right or wrong answer here. Personally, I would vote for 2. as a study of 500 people, only 100 of whom became infected is pretty small. Whereas I assume that the lower the dose you inhaled, the lower the risk. So I am all for lowering the potential dose, and if you tell me by switching from surgical masks for FFP2-rated masks I can reduce the dose by about a half, I will do that. But I am nobody’s idea of one of “world’s most eminent scientists” and they went hard for option 1., completely passing on 2.
Web app for simulating a von Karman street
In the autumn I have some new teaching: a small project to simulate a problem — von Karman streets — in the physics of fluid flow (see earlier post). I will be showing the students how a simple Lattice Boltzmann code can simulate a fluid flowing past a cylinder, and creating what is known as a von Karman street of vortices downstream of this cylinder. The code is on github, and works great on linux machines. In particular it can show the flow around the cylinder evolving in realtime as the simulation runs. This is useful as you can see straightaway – while the simulation is running – if vortices are forming and being shed from the back of the cylinder*.
The case for induction hobs in kitchens
Just before lockdown I had a new kitchen installed, complete with a new oven and stovetop. A friend has also just had a new kitchen installed. Both lovely kitchens but I have a stove with traditional gas burners, while he went for induction hobs. To be honest I didn’t think about this much, my old stove had gas burners so I got new ones.
Viruses to the rescue?
Viruses have a bad press, and this is not surprising. COVID-19 is caused by the virus SARS-CoV-2 and the pandemic is estimated to have caused at least 15 million deaths. But our planet Earth hosts enormous numbers of viruses and not even one in a million infects us humans, it is just that these less than one in a million viruses are the ones we mostly care about. So 99.999% + of Earth’s viruses infect other organisms. When they infect us and make us sick that is bad but when they infect an organism we don’t like that could be good.
Viruses touching the water’s surface
I am interested in how viruses survive the drying of the droplet they are in. The surface of a droplet is a dangerous place for a virus, surfaces exert forces and these look large enough to tear a virus apart. So, how likely is it that a virus ends up at the surface? Early on in the evaporation the droplet’s mucus or saliva will be quite dilute and watery, so the virus will diffuse around in it, and due to evaporation the mucus/air interface will be moving, and so tend to sweep up any viruses in its path. So if there is no interaction between the surface of water and a virus, or any sort of attraction, it looks likely that the virus will contact and stick to the surface.
Tearing viruses apart with the coffee-ring effect
Most papers published in the fancy journals Nature or Science are not much different from papers in regular journals, but a few have real impact. One of these is a pioneering paper by Deegan and coworkers published in Nature in 1997 (pdf here). It has been cited almost 6000 times, which by coincidence is close to the total number of citations of everything I have published in a thirty-year scientific career. Bit of a shame I did not discover something that good in my PhD, I could have taken the other twenty-plus years off.
Teaching & assessing coding in the ChatGPT, Bard, etc era
I run second-year computing for physics undergraduates. The second semester part is taught as individual projects so is perhaps a little resistant to the problem of students just getting ChatGPT or Google’s Bard to do it. But the first semester includes very common basic problems like fitting to noisy data. The bad news here is that for standard simple tasks, ChatGPT and Bard will just give you answers, and so I can’t really have an assessment where students can just ask ChatGPT.
Airborne transmission of COVID and flu relies on the survival of DNA’s fragile cousin: RNA
Our genes and those of all organisms except some viruses, is encoded in long polymers of DNA. Even so, in organisms from bacteria to us, there are special enzymes ceaselessly working inside our cells to fix breaks that can occur in these long DNA polymers. These enzymes are keeping us alive. But not only are the genes of the viruses flu and SARS-CoV-2 made of fragile RNA not the tougher DNA, but as they are viruses they don’t have the metabolism to constantly fix any breaks in their RNA polymers. So how do these viruses with their fragile RNA genomes survive?
Chance & Necessity 