First Paper: "Nonadditivity of van der Waals forces on liquid surfaces"

My first paper has been published! It is in volume 94, issue 3 of Physical Review E, and an older preprint of it is available too for those who don't have access to academic journals (it has all of the same figures and ideas, though it is missing a few sentences of further explanation as well as a couple of new citations that were inserted for the final publication). In the interest of explaining these ideas in a way that is easy to understand, I am using the ten hundred most used words in English (except for the two lines that came before this one), as put together from the XKCD Simple Writer and the Wiktionary list of the 1000 most used words. I will use numbers sometimes without completely writing them out, use words for certain names of things without explaining further, and explain less used words when they come up. Keep reading to see what comes next.

Ramblings on Depth and Breadth in Introductory Science Teaching

About a week ago, I was having dinner with a friend, and the topic of teaching in various science disciplines came up; he got his degree in biology, while I got mine in physics. One of the things that we both noticed in our undergraduate careers was that introductory physics classes tend to go fairly deep right away, focusing only on a few broad topics, whereas introductory biology classes go much more for breadth, with the depth coming in specific topics in later classes. It took us a little time to think of why this might be. I think we came up with a reasonable explanation, so follow the jump to see what that explanation might be (along with extensions of it).

A few warnings are in order. One is that although I've gone through a full undergraduate course sequence in physics, I have only taken one introductory biology class in my undergraduate studies, so I'm essentially comparing an insider view of one subject to an outsider view of another; worse, my insider view of physics was built over 4 years so it is fairly fresh in my memory, whereas my outsider view of biology came in a single semester 4 years ago, so my memory of it is rather fading (though it is augmented by the problem sets and exams that I saved on my computer). Therefore, some things I say about biology might as well come from my posterior. Given all this, if you see that I say something horribly wrong about biology (or physics, for that matter), tell me in the comments! The other is that this post may seem rambling and incoherent at times; that's because this is more of a brainstorm than anything else.

A Month into Graduate School

I realized I haven't posted anything here for this month, so the least I could do would be to provide a quick update. I've settled into my apartment nicely. Classes are going decently: I'm taking ELE 511 — Quantum Mechanics with Applications, PHY 504/514 — Electromagnetism/Statistical Physics, respectively, and ELE 568 — Implementations of Quantum Information. More exciting though has been attending seminars that professors have given about their research, and being able to talk to those professors one-on-one as well. I even have a small side-project that could lead into full-time research with one of the professors with whom I'm interested in working! All in all, this is shaping up to be an exciting semester, and I can't wait to find out more about the research opportunities in the department and ultimately pick an advisor.

Reflection: 2014 Summer

This summer, by design, I was able to relax basically the whole time. I was able to attend graduation parties, visit relatives in India, attend a wedding in New York, spend time with family & friends, and not worry about work a whole lot. Of course I was able to get a bit of work for my old UROP done too, especially as I'd like to turn it into a paper, but I didn't really feel pressure to be working on it all the time. In fact, working on that and a few other projects was mainly how I filled my downtime, but I never let those things get in the way of relaxing and having fun. Anyway, this summer is about to end, and that would make it my last formal summer break ever. In two days, I will be moving to Princeton to start a PhD program in the Electrical Engineering department; it'll likely be about photonics, quantum optics, or Casimir physics, but I have a semester to figure out the details. I'm really excited to be starting that, and I hope the journey will be a good one overall (though I have no doubt that there will be both ups and downs). If you're starting school, college, graduate school, a new job, or any other sort of new venture, good luck!

Reflection: My Undergraduate Experiences at MIT

Commencement is a few days away, so I don't have too much more time on campus. I've finished all four years of my undergraduate education. It has been a really wild and amazing ride, and now that things are marginally quieter, I think I could use a little reflection on those 4 years (or, at least, the highlights, learning experiences, and more recent parts that I remember). I am no poet, so a lot of this may sound repetitive, awkward, or stilted; believe me when I say this is really how I feel. Follow the jump to read more.

Thesis and Papers and Projects, Oh My!

I realize I haven't been able to post anything in...a month, actually. That's because most of my time has recently been devoted to finishing my undergraduate thesis (due in 1.5 weeks), 2 final projects (due in 2.5 weeks), the work for a potential paper for my UROP (hopefully soon), problem sets (all the time), and exams (sporadically, though thankfully I have no final exams). I hope to have more posts (including a few reviews) out in the coming weeks when I'm a little more free. In the meantime, enjoy this nugget of crazy physics: apparently it's possible to derive asymptotic freedom in QCD from classical statistical field theory.

Reflection: 2014 IAP

This IAP was quite a bit more hectic near the end of it. I was starting to wrap up my current UROP project on photonic crystal enhancement of spontaneous emission and start learning about a new project on nanoparticle absorption & scattering of infrared radiation. Also, especially in the last week, I was doing a lot for making a video for the MIT-K12 project. Finally, there was organization to be done for the SPS Lightning Lectures on the last day of IAP. Overall, it was quite productive. At the moment, I am still awaiting graduate admission results (except for one positive one so far). And I await and anticipate one last semester of classes and research as an undergraduate at MIT!

Reflection: 2013 Summer UROP

Wow. This summer has been incredibly busy, productive, and fun all at once. I can't believe it's already over!

So what did I do this summer?
My primary concern this summer was my UROP. I have been able to bring it very close to an end point; I wasn't able to finish it up completely, but I guess that was an unrealistic expectation because that's just not how science works. It doesn't wrap up cleanly; it's an ongoing process. I learned a whole lot more about Scheme and MEEP in the process, though, which was great.
On a related note, another UROP project fell by the wayside (as I wrote about earlier this summer) once I realized it was based on flawed calculations. To be honest, I'm not really sure if I want to pick up that project again and try to bring it to some sort of conclusion or if that's really worth my time.
My secondary concern was preparing for graduate school. I took the GRE this past Tuesday, and I am happy to say that went quite well. I have also been studying for the Physics GRE, along with making my list of graduate schools/programs/professors that I want to further investigate and send applications.
My tertiary concern was making another video for the MIT-K12 project. That went off successfully as well.

Apart from that, not being around my usual set of friends for the summer had a silver lining. While I would have certainly liked to have been able to hang out with them more, I was able to become a lot closer to a few people who usually live on my floor during the semester and hang out with them a lot more. Compared to the end of last semester, where I would basically just say "hi" to them but not a whole lot more, I now intend to hang out with them significantly more during this coming semester.

What didn't I do? These things didn't happen because I didn't have the time or energy to carry them out.
I wasn't able to edit and publish all the videos I took of 8.033 lectures from 2 years ago. In fact, I couldn't really look at those at all.
I wasn't able to do much work for OCW as I had planned.
(Actually, that's mostly it.)

I'm excited for the coming semester. My classes all look quite exciting, and I'm still deciding what I want to do regarding my UROP once my current project can truly said to be concluded. That said, I feel a bit sad that this has been my last summer at MIT, and it is already over. After that, I only have 9 more months at this place. I hope I can make those 9 months really special. Before that, though, I'll be going on a vacation with my family for a few days and then spending the remaining 1.5 weeks of August at home. Yay!

Skepticism in My Photonics UROP

I've mentioned here on several occasions that I've been doing a UROP regarding nanophotonics/photonic crystals. Specifically, my first project was in determining whether particular types of photonic structures might enhance absorptivity of light, which would help solar cells that convert that light into electricity. The goal is that the absorptivity enhancement (versus no texturing over the solar cell) should be over as broad of a frequency band as possible, because it is difficult to manufacture many different kinds of photonic structures just to satisfy performance demands over many narrow frequency bands. I worked on this project for about 4 months, because that was the time that my postdoctoral UROP supervisor was around (he moved after that). I was able to get some really nice-looking results in that time, and I figured there wasn't much more I needed to do to wrap it up, so I felt comfortable generally moving on to a new project (which I have been working on since 2012 February or so). The enhancement results looked great compared to existing designs, so I thought we might be on to something here. Recently, things started gearing up for a publication submission.

Today, it all came crashing down. Why? Another postdoctoral UROP supervisor (who I have worked with since last year primarily on my more current project but recently joined in to help progress of the older project, which is the subject of this post) asked me some hard questions about what I was really doing. Because of this, I realized that one of the parameter choices in my calculations that were giving such nice results was fatally flawed. When I fixed that issue, the results I was getting suddenly looked significantly less compelling; with that, any dreams of publication were dashed.

Why did this happen? It boils down to me not being skeptical enough about what was going on. A large part of this has to do with the fact that because this was my first UROP, I didn't have a great idea of what was going on in terms of details. And because that time I spent was only about 4 months and was followed immediately by a new project, I didn't spend much more time on that project after that. Ultimately I got complacent in more ways than one. Because the code I was using was based on existing code for similar calculations, I figured it must have been written to work even with the modifications I was making. I also figured that because I had been getting consistently good results from what I had done over those 4 months, I just needed to worry about those results on the surface and not the fundamentals operation of the code. Those two assumptions combined such that even though I had seen the results of not being careful in my second UROP project and had become much more careful about checking that code as a result, I didn't think I needed to apply the same level of care in checking the code used for the first project.

After realizing the implications of this, I did a few more calculations in a significantly more mopey mood. But then I thought about this and I realize that I shouldn't feel so bad about this. Why is that? Here are a few reasons in no particular order.

1. I've made similar mistakes before, and I've really come to learn from them. One example of something that I thought was going great but turned out badly has to do with email. People who know me may have heard this story, and people who have known me for a while may have actually been there to see me do this, but I won't share the story now; I believe it is sufficient to say that I am now a lot more careful when sending emails especially to large groups of people. A reverse example actually comes from my second UROP project: for a while I was making a mistake in my code that was giving garbage, but after many months of trying various fixes, one particular fix solved all the other issues. Since then I have been a lot more careful about checking my code for that project (though I guess I was confident enough about the code used in the first project that I thought such a high level of care might be unnecessary).

2. I didn't think I would be in the position of having my work for both projects on paper until very recently. Now I can go back to thinking that in any case my second project work would be more likely to go on paper (especially as I know that I have taken a lot more care in checking my code for that project).

3. Several months ago, when my second project was stalling, I was asking myself why it wasn't going as smoothly or quickly as my first project. Now I know that the first project should have in fact gone as slowly as the second project for the work to become as solid and carefully checked. The other part of this issue is that I have been working on the second project continuously, so I have been able to make continuous adjustments to the code and work progressively higher levels of care in checking the code in a smooth manner. Because I essentially stopped working on the first project after those first four months, if I adopt more careful code-checking now, it'll feel more like I'm starting over from scratch, which makes the process feel a lot more frustrating.

4. With all this, I feel like I have already learned a lot more from this lesson than I would have if everything was fine and dandy and this work did get submitted for publication.

5. If nothing else, I hold out hope that I may be able to salvage some good results with the fixes I have made to the code of the first project.

There are two morals to this story. The first is that I shouldn't just check the code I run; I should check it in an actively skeptical manner, always questioning each and every line. The second is that C++ is way more painful to read and (to a lesser extent) write than Scheme is for the kinds of calculations I run.

More on My Photonic Crystal UROP

In my post at the end of the summer, I talked a bit about what I actually did in that UROP. Upon rereading it, I have come to realize that it is a little jumbled and technical. I'd like to basically rephrase it in less technical terms, along with providing more context on what I did in the 2011 fall semester. Follow the jump to see more.

Reflection: 2012 Summer UROP

The long-term reviews I have been doing this summer have been on the desktop that I have been using for my UROP work this summer. Most of my thoughts about that have basically been along the lines of "UROP work went fine today". But I've realized that I haven't properly discussed what I've done this summer, I figured that I should share a little bit about that today because tomorrow is my last day here for the summer before I go home for a few weeks' break.

Let us start with the basics. A dielectric is essentially any material medium that changes the average speed at which light propagates due to the interaction of the electromagnetic field with the atoms and molecules constituting the dielectric. A photonic crystal is a periodic array of dielectric, and this periodicity can be found in 1, 2, or 3 dimensions. The photonic crystals that I was modeling this summer are in 2 dimensions; specifically, they are rectangular slabs of dielectric material with cylindrical holes of air/vacuum punched through the center along one axis. These sorts of periodic structures are special because they have certain bands of natural resonant frequencies at which the electromagnetic field is very well supported and other bands of frequencies where the field basically can't exist in the structure at all. This allows for very efficient manipulation of light at various frequencies. For instance, last fall, I was looking at optimizing photonic crystals to absorb the most light at various angles of incidence given a range of frequencies. This summer, I have been characterizing the electromagnetic energy flux from the photonic crystal structure that I mentioned before as a function of frequency and wavevector; the energy flux comes from localized current sources embedded in the dielectric material, and this models spontaneous emission. Such spectra should and do show peaks near the resonant frequencies. I was working closely with a postdoctoral associate and graduate student who had previously determined the functional dependence of the flux spectrum analytically and verified it experimentally. I was essentially providing a third method of verification through numerical analysis in MEEP. I have also asked the graduate student with whom I work about the ultimate applications of these flux spectrum modeling techniques, and the closest thing I have gotten to a good answer is that many macromolecules look like photonic crystals locally, so knowing the resonant frequencies and wavevectors for the flux spectrum makes imaging said macromolecules much easier.

In the process, I've become much more accustomed to using MEEP. I'm no longer scared of Scheme despite my C++/JAVA programming background; in fact I'm almost used to using Scheme. I've gotten a better handle on the tricks of the Linux terminal. And this was the first time that I was able to have a good level of appreciation for what I was doing, because this was the first full term that I was able to UROP after the lecture in my 8.04 (Quantum Physics I) class in 2012 May about photonics. Overall, I would say that my UROP was a success in that I really enjoyed every bit of it!

Long-Term Review: Because Now I Can

I am doing a UROP on campus this summer (as opposed to last summer, when I interned at NIST), and it is a continuation of my UROP from the last two semesters concerning photonic crystals. This summer, my ultimate goal is to be able to use MEEP finite-difference method simulations to recreate the spontaneous emission spectrum of a particular photonic crystal structure of great interest to the research group in which I am working.

To do that, I create the simulations as programs written in the Scheme programming language (a derivative of Lisp) and executed through MEEP. These actual steps are done on a cluster of computers, so the laptop computer that I have been using at my office is merely a terminal for the cluster. Because that laptop runs Microsoft Windows XP, there is no built-in way to SSH into the cluster, so I have to use a UNIX-like terminal emulator for Microsoft Windows; in my case, I use SecureCRT combined with XWin32 for graphical programs like Gedit and Geeqie. Unfortunately, that laptop is at least 7 years old (judging from its hardware specifications and thickness), and with Microsoft Windows XP, it is certainly showing its age; last semester it worked just fine, but a few days ago, it started choking trying to run Mozilla Firefox/Adobe Reader, LibreOffice Calc, and SecureCRT simultaneously. I asked my UROP faculty advisor if I could use a much newer desktop in the office that I use that no one else seems to be using, and he was fine with that; I even asked him if I could run Linux on it, and given that my previous UROP postdoc advisor (in the same research group) ran Ubuntu and helped other people set up Linux for work computers, he was fine with that too.

This presents a unique opportunity for me this summer with regard to this blog, and that's where the title comes in. One of the most common complaints about the reviews I do here is that they use the live session without trying the installation on real hardware at all. Also, because I usually only test the live session, the actual amount of time I spend is not more than a few hours spread over two days or so. Now, I have finally secured the official go-ahead to do with the computer whatever I feel is useful, so I will attempt to take more time to test some distributions (now as an installed session on real hardware) that I have said before that I would have no problem installing, because I want to see just how true of a statement that is. The computer in question is probably not more than 3 years old; it is a Dell desktop with a 64-bit Intel Core i5 processor, 4 GB of RAM, a 320 GB hard drive, and an ATI graphics card (though I am not sure if the graphics card is integrated or dedicated).

Given the amount of time I have left this summer to work, I intend to test each distribution for between 7-10 days of work, though that may change depending on my schedule and if a given distribution really does not work out. I have already installed Chakra 2012.05 "Archimedes", so that will be the subject of the first real "Long-Term Review" post. Each of these posts will be updated with a daily label detailing any changes, bugs, or other things that I notice. Each post will also have a "Day 0" label at the top sort of revisiting the live session like I normally do to set up my ideal desktop once more. At the end of the testing session (again, 7-10 days), I will publish the full post. While the "Day 0" section will basically be like a full review all over again, the following days' sections will be shorter. It doesn't take a long time to see if my favorite applications work or not, but it does take longer to really feel comfortable with the desktop, look for bugs and quirks, and make sure that upgrades go smoothly. So in these posts, I will really be looking out for details like how well the file manager and panel do stuff that I want them to do on a daily basis, how stable the system is, et cetera, as opposed to simply seeing once if something like Skype works; at my UROP, I only really need a web browser to see some web pages and check email, a PDF viewer to read papers, and a terminal emulator to SSH into the cluster, so I could theoretically settle for something like Ubuntu, but I don't want to waste this opportunity.

Again, I have already started with Chakra. I've always been fond of #!, so I might give that a go too. I'll also give Sabayon a run given that version 9 seemed to work so incredibly well. All of these will be the 64-bit editions because the computer has a 64-bit processor and 4 GB of RAM, so I want to make use of that. That leaves room for a fourth distribution (but probably not more than that); I will have to think about what I want to save for last, and I certainly welcome any comments and suggestions on the matter. Do look out for these posts along with my usual reviews and other random posts.

(UPDATE: Duh. I just realized I could do a long-term test of a prerelease version of SolusOS at the end of summer, and that would be the fourth distribution to test. Hopefully by then a 64-bit beta edition will have been released. I haven't written about it formally, but I have checked out SolusOS 2 Alpha 4, and I'm quite pleased with what I see, especially for an alpha release. Now, I will be able to see if that is really true over a longer period of use on an installed system instead of just a shorter period of use on a live system.)