Combining The Best Of Both Worlds

This is a fascinating and important advancement in the physics of light sources. It seems that it has been shown experimentally how one can get the short, intense light pulses that one gets from a FEL source, and combine it with the repetition that one gets from a synchrotron light source.

Now a Sino-German team has shown that a pattern of pulses can be generated in a synchrotron radiation source that combines the advantages of both systems. The synchrotron source delivers short, intense microbunches of electrons that produce radiation pulses having a laser-like character (as with FELs), but which can also follow each other closely in sequence (as with synchrotron light sources). 

Another review of this work, from Nature where it was published, can be found here.

While this is an important step, it really is a proof-of-principle experiment, and it requires a bit more experimental work to show that this can be viable.

Although this paper represents a crucial step towards generating high-power, small-bandwidth light pulses in a particle accelerator, steady-state microbunching has not yet been demonstrated. Deng et al. have shown that, after one turn in the synchrotron, the microbunched beam can produce coherent radiation. The next challenge is to prove that this scheme can achieve such a feat over many turns. This will be difficult to accomplish experimentally for at least three reasons.

But if this can be demonstrated, a lot of things that are done at a FEL can be performed even more at an "ordinary" synchrotron light source, a facility that is a lot more plentiful.

An important point that I want to point out here is that, these are all "tools" that allow us to study things. Without these tools, we have no ability to experimentally detect, see, or measure things. It enables us to do things that we could not do before. So the advancement in science, technology, medicine, etc, depend on not only having these tools, but also the continual improvement of these tools. Advancement in science requires all of these things to occur to able to explore more difficult and complex ideas and scenarios.

This advancement in accelerator-based light source has nothing to do with high-energy physics. In fact, if you look at the type of applications that are being mentioned, there's nothing about particle physics at all!

.....on an accelerator that could extend the capabilities of these machines even further, potentially yielding applications in a next-generation chip-etching technology called extreme-ultraviolet lithography and an advanced imaging method known as angle-resolved photoemission spectroscopy.

So once again, this is my continuing attempt at trying to make people aware that "accelerators" do not automatically mean "particle collider" or "high energy physics". In fact, the majority of particle accelerators in this world are not involved in high energy physics experiments.

Zz.

Wonders of Physics Competition

I mentioned about this more than 10 years ago in this thread. I went to UW-Madison and attended the early incarnation of this lecture-room demonstration that became a huge hit with the public. I also had Clint Sprott as an instructor in one of my courses.

Due to COVID-19, the Wonders of Physics show couldn't be held, and probably not in the near future either. To their credit, they are creating a contest instead, where you can submit a 2-minute video of an original demonstration of a physics concept.

So maybe one of you are creative enough to enter this contest. :)

Zz.

When Flipped Classroom Flopped?

I've mentioned about flipped classroom before, and that I use this format in a couple of my classes during the remote environment. This article goes the other way and pointed out when and why flipped classroom can flop and be rather ineffective.

I must say that the way this was described, it doesn't quite match what I am doing. While the students do have to watch videos and/or read something before they come to the first class of the week, they have pre-lecture quizzes that tests on whether they did watch the videos or read the material, and had a general understanding of the important ideas. These are graded and become part of their overall course grades. So there is incentive for them to go over the pre-lecture stuff.

Secondly, I don't just quickly dump them into breakout room right at the beginning. We meet twice a week and these are very long class sessions (3 hours) that often comprise of the subject matter and hands-on demos or labs (virtual labs). So I get to go over the important highlights of the subject, do a few examples, shoot off a few polls, give them a few online apps or simulations, and only then do I send them to breakout rooms to work on solving problems. In fact, in many instances, their breakout session is where they get to do their online virtual experiments and get to discuss what they are doing with one another.

I may have mentioned this before, but I did my own end-of-semester survey, and the overwhelming majority of my students liked the pre-lecture material and found them useful. So for me, the version of flipped classroom that I run appears to not be a flop.

Zz.

Physics Labs At Home

I've made several posts on various virtual experiments that may be done in conjunction with the standard physics courses. While many of these are adequate, nothing beats an actual, physical experiment that requires actual observation and measurement in person.

This paper lists a few experiments that a student may be able to do at home using items that a student may find at home. Since almost everyone having smart phones, there are certainly many activities that can be done using such devices. I've asked my students to use their smartphones to install sky-viewing app to be able to track planets, stars, and other celestial bodies. We have also used various apps that made used of the accelerometer in the phone to measure acceleration. I also have an app called "Gauges" (iOS) that allows you to use your smartphone to be an altimeter, speedometer, barometer, accelerometer (of course), magnometer, and to measure sound level and luminance. I am in the middle of designing a few "in class" (and now, it is "at home") activities using these capabilities.

While virtual experiment is fine for the present unusual situation, I still believe that this is not the same as actually doing the measurement itself and physically performing the experiment. So I'm trying to find activities that a student may be able to do him/herself, or in collaboration with another student if he/she does not have all the necessary equipment. I want to incorporate this as part of the lesson rather than an actual "experiment", so that the student can see the phenomenon that they are studying or about to study.

Have you designed simple at-home physics experiments for your students?

Zz.

General Physics Experiments Done Remotely

Oooh, yes please!

The problem that I have with online/remote physics courses is that we had to resort to a lot of "simulations" applications to do our "experiments". This is not what an experiment is supposed to be, because there has to be a components of errors and equipment issues that are involved in doing any physical measurement. So these simulations do not reflect reality.

The closest that I've seen so far is the one offered by Pivot Interactives, where you see a series of videos of actual experiments being done, and you get to measure what the person doing the experiment actually measure. It includes all the experimental uncertainties, quirkiness, etc. that the students have to also consider.

But here's another step further that gets the students even closer to being there and doing the actual experiment. I came across this article on UC Santa Barbara's effort to put their Sophomore-level quantum physics course online whereby the students can operate the equipment remotely and perform the actual experiments without being in the lab.

The automization of the quantum mechanical labs allows for students in the Physics 5L class to interact remotely with equipment using an online portal connected to the apparati set up in the lab, according to Fygenson. 

The online portal models the equipment setup, with buttons and knobs in the same order as where they would be on the actual equipment. Students can observe what happens in the lab using cameras aimed at the machines, Fygenson said. So far, the automated lab has been used in Summer 2020 and Fall 2020 and will be used again in Spring 2021.

That's brilliant! But that also involves a lot of money and effort to connect all of those equipment so that they can be operated remotely. Not many schools have that kind of resources and expertise.

I did a quick search and found an earlier report on this with an accompanying video. This gives you a better idea of how this is all done. It looks like from the video, the experiment being demonstrated as an example is the diffraction grating spectroscope looking at emission lines from various sources. This would be a very nice experiment to be done remotely.

Both articles indicated that they are sharing access with other schools, but did not indicate what one should do to get such access. I suppose I will have to contact one of the people listed at the end and see if I can have my students do at least that spectroscope experiment.

Anyone else have done something similar, or have used this?

Zz.

E&M Lab Manual for Virtual Classes

This appeared on arXiv on Christmas day. It is a series of lab manual for intro E&M virtual experiment suitable for online courses.

The pdf document itself contains the just the lab instruction. Most of the virtual experiments made use of the applications found in PhET. It is in the abstract that we get a bit of an explanation. The authors claim that:

Student learning outcomes (understand, apply, analyze and evaluate) were studied with detailed lab reports and end of the semester lab-based written exam which confirmed the virtual lab class was as effective as the in-person physical lab class. 

Unfortunately, they provided no evidence or data to support this, at least not in the document.

In my lessons, I try to incorporate the "experiment" as part of the lecture itself. So I had students perform one part of the virtual experiment, and then we discuss the outcome before they write down their observations. Then we move on to the next topic or examples before we come back to doing more of the simulation or measurement. So in many cases, the students encounter both the theory and the observation at almost the same time. The exception being when we did Lenz's and Faraday's law, where I actually gave the students the equipment and instruction, and let them discover for themselves the induced current and how the induced current behave with changing magnetic fields. So they observed the phenomenon first before they learned about the theory.

In any case, this set of lab instruction might be useful to be adapted to my remote classes. We'll see how that goes this coming Spring.

Zz.

Happy Holidays and a Better 2021

It has been a crazy year! I think I've posted the least amount of posts in this blog this year than any other year since I started this eons ago. There have been just way too much distraction and pressure coming from all the workload and learning new stuff that I had to just to be an effective instructor. It doesn't help that I think my teaching workload felt like it doubled for remote classes. I'm doing almost twice as much for remote courses than I do for in-person classes. It's crazy!

And I'm sure that students similarly felt a different set of burden and pressure with remote courses. The course feedback that I've received, even though overall they were positive, clearly reflected the frustrations the students have with remote learning and the way different remote courses were ran.

Looking into 2021, I know that we will be totally remote once again for Spring 2021. While I was more prepared to face Fall 2020, I am even more well-prepared for Spring 2021. I know the adjustments that I need to make, and I know things that I need to change. I will also be trying new stuff. Remote labs are something that I continue to struggle with. Honestly, I prefer the official online courses' approach to labs where they send kits to students, and we designed experiments for the students to do at home. However, these courses that I've been teaching are not online courses, but rather face-to-face (f2f) courses that had been forced to be delivered remotely due to the pandemic. So we have no kits. We rely on online simulation as "labs".

But in Spring 2021, I am going to adopt the lab environment of Pivot Interactives. A couple of our faculty members used it extensively this past semester, and they had good things to say about it. I've given it a test drive, and I can see how this may be as close to an actual experiment as it can get without actually physically doing it. Any of you out there use Pivot Interactives? What do you think of it?

Anyhow, with the possibility of the vaccine looming on the horizon for everyone sometime in 2021, there is a glimmer of hope that things will start moving back to "normal", whatever that may look like. So if you are celebrating the holidays at this time of the year, I wish you a wonderful holiday season and a significantly better 20201. Thank you for reading this blog and letting me indulge in spewing my thoughts into the ethereal world of the internet.

Zz.

Flipping Your Remote Classroom

I wrote just a few days ago about my effort in continuing my flipped classroom when we went into the remote mode (as opposed to being in an online class mode which is totally run asynchronously). I then ran across this article out of UC-Berkeley about doing the exact same thing.

It definitely seems consistent that for a flipped classroom, there should be a synchronous part, otherwise it doesn't make any sense. And it is nice to see the different variations of a remote flipped classroom, which gives me more ideas on how I can further tweak my own classes.

Do you run a remote flipped classroom? How do you do it?

Zz.

Intro Physics for Life Sciences

I came across this article out of Michigan State University, about the issue of teaching intro physics to life science majors. I find it rather interesting (amusing?) that this is still an issue being discussed at many large universities when smaller universities and community colleges have long focused on designing such courses for these life sciences/pre-med majors.

Without naming names, I know of 3 major universities in the Chicago area that do NOT have special intro physics courses for such majors. They lump them with the same group of students majoring in physics, chemistry and engineering. So not only are they required to know calculus in those calculus-based intro physics courses, but also they are competing with students whose major are more closely aligned with physics. It is why many of these life-science majors often opted to pay for these courses at city colleges and community colleges and get their transfer credits.

I had written something on this two years ago about teaching physics to life-science/pre-med majors. I am more convinced than ever, just as stated in the article, that you cannot teach this as you normally would to physical science/engineering students. It helps that the course was designed for life-science majors (we used text that are full of examples out of biology, medicine, etc.), but the course objectives and learning outcomes are generic and not specific to these majors. At the curriculum level, there is still a disconnect between the students' need and the official objectives of the course. As an instructor, I am bound by the course objectives and learning outcomes, but of course, I have leeway in implementing those. That means that I try to emphasize more on the topics that are more relevant to their needs and more applicable to life sciences than others. As the article pointed out, while planetary motion and central force problems are part of physics (and part of the course objectives), I do not emphasize it as much as I would in a calc-based physics class.

There can be more refinement and improvement in the design of courses for these students, making them even more relevant to their area of studies. This can only lead to a win-win situation, where the students will actually see the value and connection between physics and biology/medicine, and we can motivate the students more easily on the importance of physics in their fields. I see nothing wrong with that at all.

Zz.

Flipped Classroom Under Remote Learning

In my normal face-to-face (f2f) classes, I ran them as flipped classroom. I had the students watch videos and/or read short items related to the material for that week and have them do a short quiz on what they had viewed or read. All these before they attend the first class for that week. By they time they got to class, they should have a good idea of what the material is about.

In class, I went over the salient point of the material, and did a few examples. I also did polls on the topic to gauge how much they had understood the material. When those are done, I gave them a list of problems where they will work in groups to solve them.

Fast forward to the present day, where we have gone online with our classes. The school where I'm at tried to distinguish courses that were already designed to be online courses, versus courses that were f2f classes, but were forced to go online due to COVID. The school called those latter courses as "remote", to distinguish them from "online". While there was no mandate to do so, they recommend that remote courses be taught with large synchronous component, preferably live during the published class time. In other words, try to make it as close to f2f session as possible via the synchronous sessions.

All of my classes so far have been "remote" classes, although I have signed up to teach an online course next semester since I am now qualified to teach online classes after all that training that I went through during the summer. And for all of them, I have kept the flipped classroom model. The students had to watch videos or read the material, and did the short quiz, all before our first synchronous session of the week. During our synchronous session, I covered the major points of the material, did a few examples, did polls, and then I assigned then to breakout rooms to work on various problems.

It worked similar to the f2f format except that I couldn't see what they were working on. In a regular f2f class, I could see their work since they use a whiteboard slate to do their work, and I could hear them discussing the problem with one another. In the remote format, I could only jump from one breakout room to the next, but I couldn't see what they had done. They would tell me if they had problems, but other than that, I could only rely on what they tell me. It was not as informative as I wanted to.

But the students seemed to think that this was effective. I had my own survey at the end of the semester, and a few of the questions were directly related to the flipped format, especially on what I called the "prelecture" items (videos/reading material, and the quick quiz). An overwhelming majority of students from this past semester (Fall 2020) seemed to like having the prelectures and found them to be useful! A smaller majority of students (but still a majority) found the polls and the breakout room exercises to be useful.

I think that this is one of those pre-COVID teaching methodology that may work rather well in the remote setting IF there is a regular synchronous component that resembles a class session. It makes no sense if the class is purely asynchronous, since most of the material are online already and there are no "lectures" for there to be "prelectures". But for the "remote" modality that the school has defined, the prelectures work in almost the same way as in a f2f class, and from the feedback that I received, the students seem to find them useful. I may have to work some more on making the polls and breakout room activities more beneficial to them, but in some respect, parts of it may be out of my control since those also depend on the participation of the members of their group.

In the end, I'm pretty happy to know that some resemblance of the flipped classroom model appears to be effective in the remote classes with regularly-scheduled synchronous sessions. Since Spring 2021 promises to be more of the same, it is something that I'm going to keep on doing, with a few refinements here and there.

Zz.

Forcing A Square Peg Through A Round Hole

 Many of us survived another semester of remote or online learning. Phew!

Unlike Spring 2020, Fall 2020 remote learning wasn't as problematic and disastrous, mainly because many of us were expecting it, and knew what to expect. In my case, I mentioned earlier that I spent the entire summer getting trained as an online instructor, mainly because I want to learn about some of the best-practice method of teaching online. I honestly do not want to be an online instructor because I much prefer the standard face-to-face (f2f) instruction modality. But the reality right now is that many classes are being taught remotely, and I need to have the knowledge and skill to deliver lessons that way.

Having chatted (via Zoom) with a few colleagues from my dept. during a number of online meeting, I was shocked (or maybe I shouldn't have) at how many of my fellow faculty members think that remote lessons are simply the same as f2f lessons, but delivered remotely or online. I've even had one instructor telling me that he was trying to make his remote classes to mimic his f2f classes as closely as he can!

Regardless of how logical or effective that is, let's look at what are the facts here. Remote classes are already significantly DIFFERENT than f2f classes in a number of elements: locations, in-person contacts, immediate and direct response, and on-site actions. In other words, remote/online lessons are a completely different beast than f2f lessons. So what is the rational for treating them to be the same thing?

The one very clear message that I received during the several workshops and training I did over the summer is that if you treat remote lessons the same way as f2f lessons, your classes will SUCK! Even the layout of the learning management system (LMS) page has to be redesigned to make it more obvious and easier to navigate, because this is where the students will have to go to to find stuff. Items need to be there at their fingertips because no one is around for them to ask to get immediate feedback.

One issue that was brought up during my conversation with my colleagues is the issue of student engagement. Instructors were lamenting that their students often do not turn on their cameras during their synchronous sessions, often do not actively participate during those sessions, etc. They consider this as lack of engagements and want to know how to increase the sense of "community" and participation.

I told them that maybe what they are using to gauge student engagement is rather limited to what they are familiar with in f2f classes. For online/remote learning, student involvement includes more than just participation during synchronous session. It can also mean participation in asynchronous activities. This is where group projects, discussion forums, etc.. count as student engagement. In the effort to make their remote classes as close to f2f classes, many instructors forego other viable means of online student engagement activities, simply because they were either not aware of such means, or they do not see the importance or significance of such means. But these other means have been shown in many studies to be effective, if done properly, to engage students and keep them interested in the subject matter. These other means may not have been necessary in f2f environment, but we are not there now. It is now a different beast, and it requires different means to achieve the same goal.

For many of us who did have the online instruction training, we learned quite a few valuable lessons and philosophy in using online and remote tools in delivering instructions. In fact, most of us think that we will continue using many of these online tools even when we go back to fully f2f classes. I would certainly like to continue having Zoom office hours, because it gives quite a flexibility in scheduling meetings with students at various times even when I'm not on campus. I also now have sufficient tools to be able to show a "pen and paper" solution online when students need help. And I know that my LMS page is significantly improved compared to when I had it for my f2f classes. There are a lot of things that I will continue to do even when we go back to "normal".

But the moral of the story here is that instructors need to be aware that remote classes is NOT the same as f2f classes delivered remotely. They can't be the same. Forcing it to be is trying to force a square peg into a round hole, and then wondering why it doesn't go through.

Zz.

The Sad Ending of Aricebo Observatory

It was less than a month ago, on a Nov. 19, 2020 report, that the National Science Foundation announced the closure of the famed Aricebo Observatory in Puerto Rico due to structural and safety problems. Unfortunately, on Dec. 1, 2020, the collapse of the central structure happened, with dramatic footage released by the observatory.

While the famed telescope is gone, it will live forever in many footage from movies and tv shows. This is in addition to the numerous scientific discoveries that it has made throughout its operation.

Zz.

Students Experiences with Emergency Remote Teaching

With COVID cases going back up in many places, including here in the US, many schools are still sticking to remote and online classes. Even those that opened their campuses are now starting to fall back to such modality of learning.

At some point, there needs to be an assessment on how students are dealing with all of this, and the degree that it has impacted their learning process. The migration from regular face-to-face (f2f) classes to emergency remote classes due to the pandemic is a highly unusual case and requires quite a bit of investigation.

This is one such study, conducted on physics students at the University of Colorado-Boulder. It surveyed the students perception of how the lesson was delivered during this past Spring 2020 when all schools in the US shut down in March and changed to online learning.

Having gone through it as an instructor, I know that it wasn't easy for everyone involved. In many cases, a lot of the quality of instruction certainly suffered to a certain extent. So it should be informative to learn the students' perspective on this, and it may be useful as a guide, considering that there is a strong possibility that many of us will continue with remote learning this coming Spring 2021.

As for me, I feel significantly better prepared. I spent the past Summer 2020 getting trained as an online instructor, even though I intend to stick to just f2f courses if and when we do get back to "normal". But learning the "best practice" method in online lesson delivery was extremely helpful. But the best part was that these training courses and workshops are themselves online courses, done asynchronously like most online courses. So I got to experience first-hand what it feels like to be an online student, to feel sometime the confusion on where to find things and what to do next. The fact that you are on your own means that even the design of the learning management page can be a factor, that things need to be arranged in such a manner that things that are important need to be front and center, and easy to find. So I think that I learned almost as much about teaching online from just being an online student myself as from the course's material and lesson.

Spring 2021 will continue to be in the remote-learning format. But I think I'm getting the hang of this. I know that I no longer feel that I'm bumbling in the dark. I still need to refine many of the stuff that I do and execute, but things no longer feel daunting. I know that I'm working almost twice as hard preparing for these online lessons (we have synchronous sessions during the scheduled class time) when compared to the old f2f classes. But now, I feel that I know what to expect and I'm well-prepared for it.

Zz.

Mask Physics

There is no controversy about the need to wear a mask to reduce the possibility of COVID-19 transmission. Every scientific research that I've read supports that.

Here are some more from the physics side of it. This is approaching it from purely the point of view of physics of fluids.

Visualizing droplet dispersal for face shields and masks with exhalation valves

Visualizing the effectiveness of face masks in obstructing respiratory jets

On respiratory droplets and face masks

Zz.

Roger Penrose - Is Mathematics Invented or Discovered?

 Now that he has just be awarded the 2020 Nobel Prize in Physics .... :)

This is a video of a conversation with Roger Penrose on his opinion of mathematics and its ability to describe our world.

 

Eugene Wigner also had written a rather popular essay on what mathematics is and its "unreasonable effectiveness" in describing our world.

Zz.

Death by Spaghettification

This is probably a rather unpleasant way to die, but it may also be the most spectacular way.

Astronomers have observed for the first time the ripping apart of a star as it got too close to a massive blackhole.

“When an unlucky star wanders too close to a supermassive black hole in the centre of a galaxy, the extreme gravitational pull of the black hole shreds the star into thin streams of material,” explains study author Thomas Wevers, an ESO Fellow in Santiago, Chile, who was at the Institute of Astronomy, University of Cambridge, UK, when he conducted the work. As some of the thin strands of stellar material fall into the black hole during this spaghettification process, a bright flare of energy is released, which astronomers can detect.

What is even interesting is that the unfortunate star is about the same size as our sun. So you kinda feel a bit for the poor thing.

But of course, all of these happened quite some time ago. It is probably quiet now in that part of the universe.😁

Zz.

Total Amount of Matter in the Universe

We now have the most accurate measurement to date of the total amount of matter in our universe. A new paper published in The Astrophysical Journal[1] seems to indicate that our universe is composed of 31% matter, with the rest being dark energy.

And of that 31% of matter, 80% of that is dark matter, which we are still searching for. This means that the "ordinary matter" that is known within the Standard Model of elementary particle and that makes up you and I is only about 6.2% of the entire matter+energy of our universe. The remaining 93.8% are made up of "dark" stuff, i.e. dark energy and dark matter.

This means that we still do not know the nature of a huge portion of what makes up our universe. Would it be nice to be alive 50 or 100 years from now when we know more about these things then (hopefully!).

Z.

[1] https://iopscience.iop.org/article/10.3847/1538-4357/aba619

Teaching In Fall 2020

 At the start of a new semester, I'm amazed at how much I've learned over the summer about online and remote learning. Taking the workshops on learning about how to deliver such classes was definitely worthwhile. My perspective on such modality has expanded and I think I am significantly better equipped than when this whole mess has started.

The biggest takeaway from everything that I've learned is that taking what you do in a face-to-face (f2f) classroom and importing it wholesale into a remote or online class does not work very well, even when delivered synchronously. f2f and online are two completely different beasts, and the mechanics, pedagogy, and "psychology" are very different. Based on what I have learned about some of the best practices method, student engagements and interaction are significantly more important in online courses for their success. So there has to be a conscious effort to design the course so that the students have to engage with the material, with the instructor, and with other students. This seems to be a very common and central pedagogy in almost everything that I've read about online learning.

Luckily, the tools that we use for that can promote such engagements. It appears that many Learning Management Systems (LMS) have upgraded and add features to their software over the summer. I know that the one that I'm using seems to have been loaded with a lot more capabilities than what I remembered earlier in the year. I've employed a bunch of tools in the LMS system for the asynchronous part of my class, and I've planned many activities during our synchronous sessions via Zoom (breakout rooms, polls, etc.). This includes a few "live lab sessions" in my physics class where the emphasis will be more on simple observation, extensive analysis, qualitative explanations, and a few quantitative  calculations. We'll see how that will work.

I think that taking the workshops over the summer and being an online learner myself with those two workshops gave me a more accurate perspective from the point of view of an online student. Just finding things itself can be an issue, and you have no one to ask immediately. I used to arrange my LMS page in terms of modules. There's a module for quizzes, there's a module for homework, there's a module for exams, there's a module for labs, there's a module for lecture notes, etc. So if you want to find the document for Lab 5, you go to the lab module and search for Lab 5 document. If you want to take a quiz, you go to the quiz module and take the quiz that's relevant for that week.

While on paper this all looks fine, when you actually go through something like this, you realize that you have to jump to several different modules for find all the tasks that you need to do for that week. I noticed that this is not what they did and how they presented it in all the online workshops that I took. Instead, they organized everything weekly. In Week 1 of the course, these are all the stuff you need to do. Then we go to Week 2 and these are all the stuff you need to do, etc. Each week, the lecture notes, the quiz, the homework, etc.. are all there, in the same folder or module. You don't have to go jumping around to different module to find all the things you need to do. This is such a simple thing to do and yet, it made for a more intuitive approach once you go through it as an online student.

In the end, I'm not as stressed out about my classes being completely online this semester as I was in Spring. I think I'm better prepared for it, and more well-equipped. And boy, I hope it shows in the students' performance this semester. Stay tune....

Zz.

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.

Zz.

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.

Zz.