A Picture speaks a thousand etc.

Is it all men or is it just all the men I know? They scrub dishes like they are rubbing their girlfriends' backs! If there are any men out there that want to rise up in defense of your kind either with a counter punch or with a refutation, now is the time...

Abandonment, letters and other things

This is really one of those “Random thoughts” posts that seem to show up on this blog with alarming frequency, but I am kind of tired of that title, hence the change. First up, abandonment. That is the sensation that my blog and feed reader would be feeling if they could. As the screenshot along side shows, I have been rather disconnected from my “cyberlife”. But that is because I have been reading! Not Attention-Deficit-Disorder-inducing blogs, but books and papers! It has been almost a year since I last read and I am having so much fun! First, I reread “Guns Germs and Steel”. Then, I read 15 papers that I had put together as essential reading for a new project that I have been meaning to get started for almost a year now. Now, I am reading “A Suitable Boy”, a book that has been on my reading list for a number of years now. This is fun!

And that leads me to the second random thought about letters. In the book, Mrs. Rupa Mehra is writing long letters on Inland letter sheets. I barely remember those now, though I recall that I used to write letters when I was in high school and the first couple of years in college. It used to be at that time that you opened your mailbox, or whatever was its equivalent (like the table on which all the residents’ letters were dumped on in the hostel), with anticipation of personal communication. Now I open my mailbox, with no feeling as I only get junk mail and a few bills that have not gone paperless yet. I personally do not feel any nostalgia for the written letter and am just as happy to receive long emails from long lost friends. But my thesis advisor, an old man that must have had more letter writing years than I have been alive, used to say that there is nothing like the written word on paper and he is never as happy with an email and he necessarily feels they are less meaningful. I put it down to conditioning. We are always reluctant to accept any change are n’t we? Times have changed. In my parents’ time, calligraphy and penmanship were considered invaluable skills and the ability to spell was important. But now, who cares as long as you know how to use the spell checker in your favorite word processing software?

Well, on that note I shall sign off with promise to return with more meaningful posts in the near future. Hope you are all having fun too!

Technology spoils us so!

I am not a hi-tech gadgets person by any stretch of anybody’s imagination. My laptop my baby is a doddering old man of 4 years. I have a cell phone that Cingular gave me free when I lost my phone last year, in spite of the fact that I was not eligible for an upgrade (and just in case you have not had experience dealing with Cingular this can only mean that they wanted to throw the phone away but gave it to me instead to save disposal costs). I just bought my first digital camera, the cheapest Nikon cool pix on the market, and that too largely because we had a gift card (from redeemed credit card points, not generous friends) that was about to expire and we just absolutely had to spend it. In spite of all of this, I had occasion recently to reflect on how my life has changed in the last 8 or 10 years when for the first time in a long time, I was at home but did not have internet access for a whole day. I felt like a hand and a leg had been cut off! So, I record here some tangential thoughts I had during my time of “extreme and unnatural duress”.

1. Phone numbers : When I was in college I knew something like 25 phone numbers of the top of my head. Now, I hardly know my own, thanks to the fact that I have had a cell phone for a few years now and everyone I call is in my address book. My addiction to my address book and my speed dial has gotten to such an extent that I am consciously avoiding buying a Reliance phone card of my own and am using my brother’s so that at least I am guaranteed to remember his phone number! (if you did not know, the reliance phone card has the telephone number followed by a four digit pin as the access code. So every time I call my mother I necessarily dial my brother’s phone number. But fear not, the reliance access number is on speed dial and I sure as hell don’t know what that number is).
2. Instant email replies : My laptop or my desk top is within sight from about 6 in the morning to about 8 at night and I check my email every hour or so when I take a break from whatever it is I am doing. At that time, all professional emails are replied to immediately, even if only as a placeholder to say a more detailed response follows in n hours or n days as the case may be. So on the rare occasion that I am actually too engrossed in reading something or in a calculation, to remember to check mail, people assume (depending on whether they like me or not, and I work with both categories of people) that I am either on the verge of death (giving rise to “Is everything ok?” emails) or that I am goofing off (leading to “Where the heck are you?” emails). When did it become that 24 hours as a turn around time for an email is considered as too much time?
3. The Google addiction : This is the last but by no means the least on my list of technology induced changes in life. First, I stopped trying to remember or record in a bookmark web page URLs. You can always google them right? Then I stopped trying to use my library catalog to find papers or online resources, I always try google scholar first. Then I stopped going to online listings of restaurants or shops, Maps has it right? And the last straw in this sequence happened a few days ago. I wanted to know the definition of “nematic penetration depth”. So I asked google. And google books told me that it is on page 179 of a book that was sitting right there on my desk. Goes to show that if something happened to google I will have to spend a fair amount of time learning to live again!

Back at my desk

After a week in the Big Easy. Decent conference as far as content goes. If I could broadly group my research interests into four categories, I learnt quite a bit on two of them and next to nothing on the other two. But as always, plenty of professional smooching with collaborators current and potential, prospective future bosses and of course getting caught up with tons of friends. But if you ask what the most abiding memory of the trip is going to be, it is in the following picture.
Long Islands to go!

More substantial posts later in the week.

Random thoughts on leap day

I just had to have a post dated February 29^th, for who knows what would happen four years from now right? So, here are a few random thoughts in my head at this time.

1. I recently yielded to temptation and bought my first camera. Nothing fancy, just a point and shoot Nikon coolpix. The other day I took the following picture.

What a geek I have become! Multicolored pens arranged in a row at the edge of my desk. Not only that, I have become an organization freak, obsessively cross-referencing and filing my notes away for I am tired of reinventing the wheel every few days, just because I am not able to find notes or references.

2. I went to look at the site stats for this blog yesterday and found this.

An anomalous peak that screws the scale so much that it renders the rest of the landscape totally flat. The reason is that DP linked to my “Experimenting with Box.net” post. I write all these beautiful (even if I do say so myself) science posts that almost nobody reads and they link to the “freak of nature” ARR post :)). [*]

3. Speaking of science posts, a blogger that DP likes a lot has this cool post on caricatures of seminar speakers, do read if you have not already.

4. Also, blogging break coming up. I start traveling next week. Seminar in Boston, then onto New Orleans. None of the talks are written so I guess I will be married to win edt and powerpoint for the next few days.

[*] Aside for A, all other readers ignore: I know you did this. But why is there no hat tip acknowledgement? Feeling cowardly are we?:)

From birds and fish to cells

A physicist’s view of collective transport in biological systems

Let me motivate what I want to say today with a couple of videos. First up, an amateur video of a flock of starlings in Scotland.

Or see this one, where the flock cohesively responds to a predator. A Starling is a small bird, shown in the picture alongside, about the size and shape of a “myna” if you are familiar with it. They fly in flocks that do amazing things as a collective entity as you just saw in the above example. Understanding how they do this is field of active research as indicated by this cover of the October issue of Physics Today. I will tell you a little bit about how they do that subsequently. But you might say to me, “They are birds, and they have brains, albeit “bird brains”, so they see, process that information somehow and do stuff. Why would a physicist concern herself with that?” So, to make my point even more clear, let me show you one more video.

This one is a microscopic movie of a bacterial swarm (obtained from here). Do you see the complex flow patterns they exhibit? These guys clearly do not have brains. It might be that this rich collective behavior originates in more chemistry than physics, but clearly not biology. And to make my point that it is indeed just physics, I ask you to look at this other video (obtained from here)

Do you see the similarity in the flow pattern to that seen in the bacteria? Can you guess what you are looking at? It is just a vibrated monolayer of some centimeter long metal rods! Whatever is going on here is clearly just physics. Moreover, one can mathematically represent the motion of the bacteria/birds and those of the rods by the same set of equations! What I want to do in the rest of this post is to give you a flavor of some of the physics behind these and other collective phenomena in biological systems.

When looking at fish schools or bird flocks, the first postulate that comes to mind is that the phenomenon is “follow the leader”, with one bird/fish doing its own thing, and the others following. But as stated above, the things that birds/fish do is “mathematically similar” to what the bacteria do. So “follow the leader” seems an unlikely scenario. The logical next question to ask would be, “What are the minimal rules that can give rise to this kind of behavior?” We have known the answer to this question for a while now [1]. The rules are the following – Each member of the flock does each of three things a) Alignment : Adjust my direction of motion so that I am going in the same direction as my neighbors, b) Velocity matching : I adjust my speed so that I am going with the same speed as my neighbors c) Cohesion : I try to keep the distance from my neighbors the same at all times. With these basic rules and simple boundary conditions for entities at the edge of the flock, like “If there is food, turn towards it” and “If there is danger, turn away from it”, most of the complex patterns exhibited by these groups of organisms can be reproduced!

But these are just rules. So, the next question to ask would be, “Can these rules come about from just physical interactions?” Let us ignore the boundary conditions associated with food/predator for the moment, they clearly are chemistry and other higher processes and focus on the bulk flocking rules. What is a unifying thing between the birds, the fish the bacteria and so on? What they are, are objects that have a non-spherical shape that actively move through a medium (air/water etc.). Now what does that mean? They exert a force on the medium [2]. The medium responds, i.e., the fact that my bird/fish/bacterium is pushing on the fluid induces a flow in the fluid itself. This response now propagates through the fluid. So, a bird/fish/bacterium that is elsewhere will feel this change in the fluid, in terms of the local flow field and pressure gradients. And it will adjust its own force on the fluid accordingly, and this whole things feeds back to the other entities in the flock. This phenomenon is called hydrodynamic interaction. And this is the dominant interaction that produces the three aspects of flocks that is listed in the previous paragraph!

Further, I want to make the case that this quest for minimal mechanisms for collective behavior is not just restricted to animal group behavior on the different scales encompassed from birds to bacteria. For this, see the famous video below.

This is a video of a neutrophil chasing a bacterium and then gobbling it, the immune system of your body at work. I know what you are thinking, “This is one cell chasing one bacterium and the primary thing at play here is chemotaxis, so what is collective about this?” The collective aspect lies in how the cell crawls, i.e., at the sub-cellular scale. The interplay between membrane fluctuations, the stresses in the actin-microtubule network that makes up the cytoskeleton of the cell, the interaction of this network stress with the medium that the cell is in and many other things go into understanding how the cell crawls. The mathematical paradigm and the physics aspects of this question are not so different from those one uses to address animal group behavior we considered earlier! But for now, this is just a teaser. A separate post on this to follow later.

[1] Actually the first instance in literature was in the context of an algorithm for computer graphics, available here.

[2] If we want to be careful, then clearly third law tells us that the swimmer must at least be a force dipole. Since there is no mathematics displayed here, I fudge this point.

Are you a Rahmaniac?

As regular readers of this blog would know, I am crazy about the music of A R Rahman [1]. A random phone conversation with a friend a few days ago revealed to me that I actually know too much trivia about the guy and his music. So, find below a few random facts from the early years of this musical superstar (early years being pre Rangeela and Bombay, after which he stopped being the exclusive property of us Tamil folks). Interspersed with these random facts are a few questions for you. If you can answer all of them, then you must be a fellow Rahmaniac as well! [2]

Let us start with a classic:

While you listen to it, let me tell you something about it. Legend has it that when Mani Ratnam first talked to Rahman about the possibility of them working together on Roja, this was the music that Rahman played for him, having composed this some time earlier.

Now to Question 1: Do you know the first movie that Rahman committed to as a music director?

Next, we all know that Rahman was doing ad jingles before he started his movie career. Here is an ad from his early days.

This was the first time Arvind Swamy was featured in a work that had music by ARR. Now Question 2: Can you name three other instances? Everybody can name two for sure. A not so helpful hint: The following song is one of the lesser known ones in a candidate for the third album, but I like it a lot. Do you?

Moving on, after very urban scores in Roja, his second tamil release Pudhiya Mugham, ARR came up with this album that was so ethnic Tamil that it surprised everyone. Here is one of the lesser known songs from this album. Question 3 : Can you name the album?

He has subsequently come up with a whole bunch of such songs of course; Karuthamma and Sangamam come to mind when thinking along these lines.

Next, here is one more lesser known song by my man. It is still on my all time favorite list after all these years.

Question 4 for you: Can you name the movie? Hint : The movie had Ajith in it and if I remember correctly, the thalai actually dies in the movie!

Finally, deviating from my early Rahman theme, this song, composed slightly later in his career is one of my really really favorite songs that somehow many people do not remember.

Do you think it is good? Question 5 for you: Can you name the movie? Hint : This album features one song in which Apache Indian is credited as co-composer, the video of which is below:

[1] Those reading by feed : a) This post is an anomaly. So feel free to ignore it. Also, there are music pieces embedded in the post that might not show up in your reader.

[1] Without the aid of google of course. With google, we are all experts in everything, are n’t we?