Friday, July 17, 2020

Followup On Far-UVC Light Kills Airborne Coronavirus

This is a follow-up on the topic that I posted last time regarding evidence that far-UVC light can effectively reduce airborne virus transmission.

I read more about it, and found this extensive Physics World article that highlights the current development of the application of far-UVC light in virus sterilization. So obviously, this is a very active area of research right now. There are compelling evidence that far-UVC may be safe to human beings under limited exposure while still be effective in eliminating airborne viruses such as COVID-19.

But another issue that I've been trying to dig through is that, while far-UVC may be safer in terms of very short penetration depth into the skin and cornea, I haven't read much on possible ozone generation. One of the nasty effects of UVC light is that it can create ozone gas.

I sent to the International Ultraviolet Association webpage (didn't know one existed till recently), and went through their FAQs. One of them addresses the specific issue of ozone creation:
Does far UV (200 – 225 nm) generate ozone?

From a photochemical perspective, yes.

The Chapman cycle (Chapman, 1930) describes the counteractive processes of ozone formation and degradation from the interaction of light with molecular oxygen (O2) and ozone(O3). The rate of generation of ozone by far UV-C (known as the Herzberg continuum in atmospheric science) outweighs the rate of its degradation; the tipping point at which this generation/degradation balance flips is ~242 – 243 nm. (Andrew et al., 2003; Santos, Burini, and Wang, 2012), Far UVC (200-225 nm) only generates ozone in the upper atmosphere, where path lengths are very long. In a normal laboratory setting, ozone would not be generated because oxygen (O2) is a very weak absorber in the far UVC region.

As with any process, the risk of such hazards should be assessed on an application-by-application basis. A low power lamp operated in a well-ventilated area may not generate a measurable ozone concentration; a high-power system in an enclosed space may constitute a substantial risk.

Now, I don't quite understand why the "path lengths" have anything to do with ozone generation in the upper atmosphere, but it seems to imply that in a lab setting, far-UVC is not an effective ozone producer because it is a weakly absorbed by oxygen molecules. I can't get access to those articles while I'm at home, and I'm not even sure if my institution subscribes to any of those sources. So if anyone has more info on this, let's hear it.

This will be a tremendous way to reduce airborne transmission if it can be show to be effective and safe. But as with many things, it needs to be investigated carefully.


Monday, July 13, 2020

Far-UVC Light Kills Airborne Viruses, And Safe To Humans Too?

First, let me give you the link to the paper that was published in Nature recently.

I actually have 3 separate topics to discuss here all based on this single paper.

The first is the science. UVC is used to kill viruses and sterilized stuff. We know that already. But it is also unsafe to human and we do not want to be exposed to it. But it turns out that far-UVC, having wavelengths in the range of 207-222 nm, is not totally harmful to human. In fact, ...
a regulatory limit as to the amount of 222 nm light to which the public can be exposed, which is 23 mJ/cm^2 per 8-hour exposure
means that humans can be exposed to this range of UVC for a limited amount of time. This is the basis of that research, i.e. using that wavelength and intensity of far-UVC, and see whether it can greatly "inactivate" the amount of viruses carried in airborne aerosols. They found that an exposure of just 25 minutes, very much below the regulatory limit. So there is a way to kill off viruses in airborne aerosols in the same space that human beings are around!

Certainly the implication of this research can be quite important, considering that airborne transmission of the COVID-19 virus is a strong possibility, which is why we are all wearing masks in public. There is now a way to greatly reduce such mode of transmission if this research is verified. The only thing I'm a bit weary about is the health and safety aspect. I know that they cited several sources that seems to show that the far-UVC is harmless to human, and the regulatory limits that have been imposed. Still, I'd like to have this one to be more well-established before I get really excited about it. For example, although the exposure limit is given in per 8-hour doses, how often can someone be exposed to that limit, say, in a month? Is that 8-hour dose limit per day? And certainly, long-term effect needs to be considered in anything of this sort.

But still, I find this result to be very promising, and it certainly is a new piece of information to me that far-UVC is actually not that harmful to humans.

The second aspect of this paper that I want to highlight is to the general public who often do not quite understand the nature of scientific publication. The main reason for scientists to properly publish their work is so that the rest of the community, especially those experts within the same field of study as the work, can scrutinize the work and evaluate its validity. So having something published does not automatically makes it valid. This is important to remember and understand. It requires scrutiny and verification by other experts in the field, and can sometime takes years. Think of how long of a time period from the moment the Higgs mechanism was proposed till its experimental verification at the LHC.

Therefore, it is imperative that a paper contains all the relevant information used to arrive at its conclusion or result. In this case, it is an experimental paper that produces a result. For it to be evaluated by other experts, it must contain all the necessary information. If you look closely at the end, the authors included their methodology, the exact equipment that they used, the experimental setup, the nature of the data analysis used, etc... etc. In other words, everything is as transparent as possible. It allows for someone else to repeat the experiment, and that is a crucial aspect of experimental science - REPRODUCIBILITY. It is something pseudoscience cannot do!

The third and final aspect of this paper is educational. I'm excited at the various values that they used in this paper, because I can already see myself using them in my general physics lessons. I'm already planning on using many of these numbers and asking my students to calculate (i) the amount of power per unit area based on the exposure time, (ii) the energy per photon of 222 nm light, (iii) the number of photons that impinges on a unit area during the exposure time, etc... etc. This will be perfect especially for the general physics course that I have taught that is aimed at life-science/pre-med majors. I always like taking something current, and very relevant to our times, to use as a material in our lessons. The students can immediately see first-hand that what they are learning is, in fact, very useful and has a direct effect on them beyond just wanting a good grade at the end of the semester.

So yes, I'll be holding on to this paper for quite some time.


Friday, July 10, 2020

Simple Way To Help Your Instructor During Remote/Online Learning

Dear Student,

Many of you may continue having some form of online or remote learning this coming Fall 2020 and maybe even for the next few semesters. Even if you get back to face-to-face instruction, you may still need to communicate with your instructor electronically. So this advice that I'm going to give you will be applicable especially if you require remote assistance from your instructor.

In STEM subjects, specially math, physics, engineering, etc., face-to-face instruction has the imminent advantage over remote learning because of the simple ability to write and sketch. In physics especially, when we approach or discuss a concept or a problem, a sketch is often required to set up the situation. This is then usually followed by the writing down of mathematical equations, and then the grinding out of the math to solve the problem. In a typical class situation, these are done on paper, and it is the simplest and quickest form to do such a task.

Doing this during remote learning can be challenging. Most of you may be require to show your work, or to show what you have attempted if you need help from your instructor on a homework problem, or even during quizzes and exams. What most students end up doing is to pull out their smartphones, snap a photo of the page with their work, and then e-mailing the image file to their instructors.

I have been on the receiving end of such submission, and in at least half of the cases, it was very difficult to read and decipher the image that I received. Most students do not inspect the images for legibility. I often receive images that are dark, with poor contrast, and often having shadows that made some parts easier to read than others. In addition, the angle that the images were captured may also be rather odd, because most of these were not captured straight on.

Here, I'd like to make a suggestion on how you, as a student, can help your instructor by submitted a clearer and more legible image, using the same equipment that you already have. This is also to your advantage because in the case of a quiz or an exam, if your instructor does not understand or can't read what you wrote, you probably will not be given credit for such work if it is required.

OK, so here is what you should do. Install a scanner app on your smartphone or mobile devices that you frequently use. There are many scanner apps available on iOS and Android platform. Many of these are free or with minimal cost. Next time you need to send a snapshot of your work, use the scanner app instead or using the standard camera app. It makes a tremendous difference, and I'll prove it to you here.

I have an iPhone, and the scanner app that I have is called ClearScanner. The free version of this app has limited capability (no OCR), but it is still sufficient for what you will need it for (I have the full, paid version).

In the first image, it is a page filled with handwritten work. I took this using the iPhone standard camera app. I did not make any edits on the image quality, didn't do any cropping, etc, other than change the image file size. This is what I get.

Now, I hate to say this, but I will. Most of the submission that I received from my students were not even half as good as this. But let's go with this in any case. Now, already you can see that, as someone who has to figure out what has been written, this may not be impossible to do, but you are asking that person to do quite a bit more work here. The low lighting and the crazy angle that the image was taken present a challenge to read this accurately.

Compare this to the image of the same page but taken by the scanner app. I took it from the same angle, and under the same lighting condition. The only difference being that the scanner app asked me to confirm that correct boundary of my document in the image. In this case, the boundary is the edge of the paper. Once I confirmed that, the app took over and produced this image:

The difference is night and day. Not only is the writing clearer here, but the crazy angle is also gone. The app corrects for the angle and presents it as if you scanned it on a flat-bed scanner. And all this with hardly any more effort than taking a regular photo.

I will show another example. In the photo below, another common "feature" of images that I receive can be seen, i.e. shadowing.

Once again, it doesn't look bad in this image, but the ones that I have received were a lot worse than this. I had to do my own image editing to be able to see clearly the writing that was in the shadow.

So how does it look using the scanner app? Again, I didn't do anything to the image other than confirm the boundary of the document. This is what I get:

It looks almost identical to the previously scanned page, with the shadow removed. I assure you that this is a different image than the first scanned image above.

This is such a simple thing to do, with hardly no additional steps and effort, and yet, it produces such a remarkable difference in clarity. Which one, do you think, will your instructor prefer to receive?

Students in my class during the previous semester were told to install such apps if they have the capability. It made a tremendous difference in the quality of the document that they submitted. Many of them also told me that the app was useful to capture even written notes on whiteboard in class. So you  may find that it is one of those handy and useful app that you didn't realize you need till you have it.


Thursday, July 09, 2020

Possible Discovery Of A New Type of Tetraquark, And Possibly Misleading Reporting Article

We have had reports of the discovery of possible tetraquarks and pentaquarks before (i.e. particles with 4 quarks and particles with 5 quarks, respectively). There is an extensive overview of the experiment and theory in this article. So the announcement out of LHCb is not that new. What is new is that this could possibly be a new type of tetraquark made up of 4 heavy quarks.

“Particles made up of four quarks are already exotic, and the one we have just discovered is the first to be made up of four heavy quarks of the same type, specifically two charm quarks and two charm antiquarks,” says the outgoing spokesperson of the LHCb collaboration, Giovanni Passaleva. “Up until now, LHCb and other experiments had only observed tetraquarks with two heavy quarks at most and none with more than two quarks of the same type.”
You may read the preprint here.

That should clear up very much of what the brouhaha is. I probably would have glanced over this had it not be the fact that I stumbled onto another news reports of this discovery, but with a different tone that could be misleading.

First of all, let's look at how CERN produced its news release. The first paragraph read like this:

The LHCb collaboration has observed a type of four-quark particle never seen before. The discovery, presented at a recent seminar at CERN and described in a paper posted today on the arXiv preprint server, is likely to be the first of a previously undiscovered class of particles.
Notice that it says "... a type of four-quark particle ...". This means that there are already other four-quark particles, and that this discover is for a new type that has not been observed before.

Now, compare that to the reporting done by two (count 'em) particle physicists on The Conversation (a place that I go to regularly) on the same discovery. Here is what they wrote:

The LHCb collaboration at CERN has announced the discovery of a new exotic particle: a so-called “tetraquark”. The paper by more than 800 authors is yet to be evaluated by other scientists in a process called “peer review”, but has been presented at a seminar. It also meets the usual statistical threshold for claiming the discovery of a new particle.

If you don't know any better, by reading the first sentence alone, you'd think that this is the first ever discovery of a tetraquark, which would be false.

Certainly, if you read the article further, you'd come across the passage that clarifies what this discovery is:

All tetraquarks and pentaquarks that have been discovered so far contain two charm quarks, which are relatively heavy, and two or three light quarks – up, down or strange. This particular configuration is indeed the easiest to discover in experiments.

But the latest tetraquark discovered by LHCb, which has been dubbed X(6900), is composed of four charm quarks. Produced in high-energy proton collisions at the Large Hadron Collider, the new tetraquark was observed via its decay into pairs of well-known particles called J/psi mesons, each made of a charm quark and a charm antiquark. This makes it particularly interesting as it is not only composed entirely of heavy quarks, but also four quarks of the same kind – making it a unique specimen to test our understanding on how quarks bind together.

So this is not the first discovery of a tetraquark, but rather a discovery of a type of tetraquark, which is what the CERN article implied.

I know I'm being picky, but I've always said that communication between scientists and the general public is extremely tedious. Often times, what you wrote is not what they understood! And once something or some impression has stuck into their heads, it is very difficult to change that. Having a misleading idea immediately imprinted at the very beginning of an article is a horrible thing to do, even if the rest of the article is accurate. At worse, the reader holds on to the original misleading idea, and at best, the reader becomes confused with conflicting understanding. In the world where a lot of people have attention deficit and all they care about are quick bites of news, the message conveyed in the very first paragraph, or even the very first line, is all that they read and get.


Friday, July 03, 2020

Simple, Basic, COVID-19 Math

This is highly elementary for most of you. But I've learned a long time ago that what I consider to be obvious and trivial, is not the case for many members of the public. This is one such case because I've heard this uttered in the media, in print, and among some people.

There is a large increase in the number of positive COVID-19 cases being reported in many states in the US. A lot of people, who shall remain nameless, make the excuse that this is due to the increase in testing, and that it shouldn't be alarming. The more you test, the more you find, they argued.

So I'll illustrate this with simple, basic math.

Let's say you have a population of 1000 people. And let's say that 200 of them has COVID-19. This means that 20% of the population has the virus.

If you randomly test 100 people, you'll get 20 people who is positive.
If you randomly test 200 people, you'll get 40 people who is positive.
If you randomly test 300 people, you'll get 60 people who is positive.

So yes, in terms of absolute numbers, the more people you test, the more number of positive results that you will get. HOWEVER, look at the percentage of positive test. No matter how many people you test, the percentage will still be 20%. The absolute number will increase with increasing number of tests, but the percentage (some people call it positive rate) does not change considerably. This is what a lot of people appear to not fully comprehend.

Of course, in real life, the percentage won't be exact, but if we keep having these tests, it will hover around some value and not change systematically or monotonically over time if there is no change in the number of people infected. So what you need is not the absolute number but also the overall percentage of positive result per day, let's say. That is of more importance if you are trying to see if things are getting better, or worse.

The situation, of course, is more complex than this. But the point in all of this is that you simply can't dismiss the increase in numbers by claiming that it is due to an increase in the number of testing. That is not the whole picture. What if you do the above exercise again and instead, you get 50 out of 200 being positive one week, and 90 out of 300 being positive the week after that? Can you still attribute that to increase in testing only?