Saturday, December 27, 2008

Why does gargling with salt-water help relieve a sore throat?

In all parts of the world, colds and sore throats occur with predictable periodicity. Their relative harmlessness ensures that the lustful commercial gaze of Big Pharma stays focussed on solving life-threatening problems like erectile dysfunction.

Thus, the task of relieving sore throats falls squarely upon the time-tested shoulders of household remedies. In my family, like many others, the standard chemotherapeutic cocktail is salt water - plain and simple. My mom, a medical doctor, swears by gargling salt-water. If you eavesdrop what many people will only whisper, it is more than just a quick fix for a bad throat. It is elixir.

So why does it work? Is there is physico-chemical explanation?

There seem to be several explanations on the web, including many (such as a change in pH) which I cannot buy. The key concept here is osmosis. I try to describe that process next.

Normally, when you have an uneven concentration of something (solute, like ink) dissolved in water, the process off diffusion (which is the merely an avataar of the Second Law) drives the transport of the solute (in reality the solvent is also diffusing simultaneously) from regions of high concentration to regions of low concentration. It tries to even things out, spread stuff around, like Vladimir Lenin. Think about blood dropped into water, or the spreading of Lenin's fart.

When there are semipermeable walls separating the regions of high and low solute concentration, well, things change. Our friend Mr. Osmosis makes his theatrical debut. The big difference is the semipermeable membrane - it is impermeable to the solute, and permeable to the solvent. Now, nature is a socialist and likes evenness. Since the solute is jailed by the membrane, transport of the solvent will have to do.

Sounds complex. A practical demonstration is in order. When you drop a grape into a glass of water for sufficient time, you see osmosis at work. The grape swells up, because water flows across the grape skin (membrane) into the grape (crudely high concentration sugar solution).

The following diagram, which I stole from Wikipedia, demonstrates the same idea, only here I am changing the makeup of the neighborhood of the cell. Hypertonic means, the environment has high solute concentration compared to the cell. The rest of the picture is self-explanatory and I won't hurt your intelligence by spelling it out.

So now that we have learned some of the science behind the phenomenon, we can get back to the question of gargling. When you have a sore throat, often bacteria and swollen inflamed cells are the culprit. So when you gargle and create a hypertonic environment, the bacteria shrivel up, become emaciated, beg for mercy, and die.

At the same time, your swollen inflamed cells also lose water. But this is a good thing. Why? Because once you've eliminated the metabolites in the inflamed cells, your vasculature brings in fresh supplies and helps with the process of healing.

Thursday, November 27, 2008

I, me, myself. An Enigma.

Many many years ago there was nothing. Then there was me. I fiddled with a few stray molecules and compressed them to infinite density. It went bang. Then, for some unfathomable reason, I couldn't suppress an irresistible urge to fart. "BANG!", it violently echoed down the crisp new corridors of Time. This one was Big. Many years later scientists proposed a theory about it...

I am all powerful. When the Gods feel helpless they pray to me. I can collapse parallel multidimensional probabilities to singularities, and tear through the fabric of space-time. I can outrun a photon, and travel at the speed of thought. The arrow of time means nothing to me, I can twist, and turn, and reverse and transform it into a toothpick.

When I am in a particularly good mood I like to resurrect the dead. When my medications wear off, I usually liquidate them again. My unpredictability makes my followers exclaim, "Mysterious are His ways!"

I love food. I consume pesticide for mega-vitamin supplements. I created Monsanto to compete with Centrum. My brain, consequently, has a hyper-intelligence drive. Once I took an IQ test. The test failed, saying it couldn't handle four digit IQs. I can solve hyperbolic partial differential equations with mixed Dirichlet and Neuman boundary conditions, orally. I can recite the value of "pi" backwards. With a pencil and paper I can do 36 billion floating point operations per second. In double precision. Armed with a cup of Dunkin' Donuts coffee, I can double that performance.

I am adventurous. I have been through eight hijacks. I supervised half of them. I got the license to kill before I got my driver's license. I've been hunted by the Mossad since more than a quarter of a century. They don't know why and my friends neither do I. I foiled seven assassination attempts on me before I had the right to vote. I haven't voted even once.

I am unpredictable. If someone draws three aces from a pack of cards, I go ahead and calmly draw three more. I have rejected three Nobel Prizes, and one Miss Universe crown on principle.

I am ruthless. When someone makes a wise-crack at me, I put it up on his epitaph an average of 1 minute 22 seconds thence. Treachery and betrayal by the closest of friends has rendered me a rock. And an island. And I love Paul Simon. And the Beatles.

I have been there. I have done that. I have commanded a troop of men in a famous covert operation for the FBI, danced around in careless glee as a shepherd in the mountain valleys of Kashmir, worked in the rain clogged sewers of Bombay, served as President for consecutive terms, written astrology columns for several newspapers, struck Olympic Golds in sumo-wrestling and figure skating in Seoul '88, built my own house on the banks of the Amazon, recovered from an ugly bout of drug-addiction, launched a geo-synchronous satellite and developed several constitutive equations for entangled polymer melts. I built my first grenade when I was five. By the time I was in high school I had an entire arsenal of nuclear tipped, laser-guided, heat-seeking, precision missiles in my backyard with the Middle East eagerly coveting them. I was knighted for life-time achievement as a teenager.

I am a defender of liberty and champion of free-will. I wish I could be as free as a majestic eagle in flight ... Or a nocturnal cold-blooded slimy amphibian with two heads and bloodshot, probe-like eyes which feasts on human blood and reproduces asexually. I am electrically positive, chemically alkaline and physically volatile.

When I'm bored I make accurate meterological predictions for the upcoming week. I play with the dangerous. Chance, fire, evil spirits .... I use asbestos underwear and strongly recommend them. My resume' is more impressive than God's, and if the Universe were a meritocracy, I would be running it. I am a part of the collective conciousness, thought and matter-energy continuum. I love Linux, Pink Floyd and my family. I really do!

I wish the day had one extra hour - so I could sleep some more.

PS: I found this writeup from my grad-school webpage archived on some hard-disk somewhere. It was heavily inspired(!) at that time by a statement-of-purpose by a college applicant to NYU. I thought I'll regurgitate some of my older material, since parts of it still tickle my fancy.

Monday, October 20, 2008


Priya is due in a couple of months, and like most women in this media-saturated-world, she is over-exposed to pregnancy-related information.

Being a scientist, I tried googling "pregnancy" and it gave me a 110 million hits (on 10/21/2008). For comparison, I also googled "porn" and it gave me 190 million hits (again, on same day). Not bad, huh. If one extrapolates this information with audacity, it could mean that the amount of pregnancy related information is about 1/2 the amount of porn on the internet.


When somebody said, "you can find anything on the internet," God, they weren't kidding!

Especially expert opinion on health-related issues. It is funny how every few years, important sounding voices, in important looking attires boldly proclaim that everything we believed in because other important sounding voices in important looking suits told so, is all wrong.

All freakin' wrong!

Eat papaya. Don't eat papaya. Eat eggs. Don't eat eggs. Do something. Wait six months. Don't do something!

PS: (11/27) I realized that I made an error in my informal Google test. Didn't turn SafeSearch off. Turns out, it does not affect my numbers.

Sunday, September 21, 2008

Wild Encounters I: Snakes of Tallahassee

After seven years in Ann Arbor, Michigan, one gets used to skunks, racoons, deer and the like. So when we moved to Tallahassee, a couple of years ago, and people told us that there is a lot of wildlife there, we weren't particularly alarmed. There is a certain glamor in living in wild parts.

A key difference between Tallahassee and Ann Arbor is the relative numbers in which the insect and reptile kingdoms are represented. The insects actually bother me more, because more insects means more lizards and frogs, and this entire ecosystem wants to sublet your house without paying rent.

I like to run, and prefer running outdoors, generally on trails. Tallahassee is great because, you can run year round unless the heavens are leaking or a Hurricane stops by to say hello. What amazes me however is the amount of "wild" stuff you encounter. On two occasions (in spring) I've had snakes lazily stretching out on the trail, perhaps hoping somebody will give them a massage or something. A couple of other times we've seen snakes in close to the edge of water bodies. Since we like camping and running in the woods, I decided to do a little researching and am presenting part I here. Part I, is all about the "water moccasin" which sounds like comfy shoe you'd wear to the beach, but in reality is a poisonous reptile with a reputation for meanness.

I started my research at the fountain of all knowledge.


I found the picture below here (by Andy Wraithmell). A water moccasin is also called a cottonmouth (another soft name, these herpetologists need to get real!) because when it opens its mouth (as a defensive power play) all you see is white like cotton.

However, it belongs to the viper family (I've also learned that rattlesnakes are pit-vipers not found in the Old World.) Cottonmouths are found all over Florida, so I have to run really far to get away from their territory. From an hour long of googling it seems to me that the degree of their aggressiveness seems to vary. Anecdotal blogs, opinions seem to reiterate that these snakes are highly aggressive, while others trying to back up these characteristics with quantitative studies seem to suggest otherwise. But I guess one shouldn't take chances. Which means one has to be able to tell a water moccasin when one sees it.

Things to look for.

1. about 3 feet long
2. in water swims with most of its body above/on water surface
3. head cocked at 45 degrees (see pic above)
4. near water (likes to laze around branches etc.)
5. if mouth open, you see lots of "cotton"
6. like all vipers has a well defined triangular head.

Sunday, September 14, 2008

Everyday Thermodynamics I: Why does warm air rise?

A new Fall semester started at Florida State University. In other parts of the world, a riot of colors slowly descends with
beauty, grace and briskness. The air has a newfound cold bite, and is filled with the anticipation of Saturdays and college football. Not so, in Tallahassee.

In Tallahassee, we sweat.

And for the first 10 days in the Engineering Building we steamed as the AC broke yet again. And I noticed something interesting. It is funny, how what we notice depends on what we think. I am teaching thermodynamics for the third straight year (which is great in terms of the time such a luxury affords me), and I noticed right away that my office which is on the third floor was much warmer than the ground floor although the air-conditioning for the entire building had failed.

What had happened was obvious. "Warm air rises, cold air sinks!". Unfortunately for the kids taking ECH 3101, I have this section called "bonus surprise tests" (whose popularity is variable, but usually negative) and I decided that this was, what people who sound like experts call a "teaching moment". Pronto, I put this on their first surprise test, and asked them to explain why warm air rises, assuming that air is an ideal gas (which in this case is not a bad approximation)!

The answer is fairly trivial. To aid thinking it is useful to ask why water sinks and oil rises. It is immediately clear that the quantity to go after is density. The rest, however important, is ironing out the details.

The ideal gas law says PV=NRT, where symbols have their usual meaning. Therefore, N/V=P/RT. N/V is the molar density. The pressure doesn't change too much over 20 m (air pressure drops with altitude, by about 0.01 bar per 100 m.). Therefore density is inversely proportional to temperature. Thus cold air is more dense. QED.

The same effect, of-course, underlies the rising of hot air balloons like the one pictured left.

Just to dispel any lingering suspicion that you may have figured everything out here is an interesting question as an epilogue. If warm air rises, why is it cold in the mountains? Think about it for a while and then click here (pdf) for the answer.

Saturday, August 30, 2008

Computing and Me

My first brush with a computer was in the summer of 1986, when my dad bought me a ZX Spectrum with 48Kb RAM (wikipedia). The first six months or so, I spent endless afternoons being wowed by games such as Dynamite Dan and Commando, until I realized that more could be done.

The computer had a primitive BASIC language compiler, and slowly at first, and later with great enthusiasm (like the one that characterizes kids who've just learnt to bicycle), I began writing programs, and that was when I essentially fell in love with the machine. My grades at school suffered initially, but if I can make any claims to being somewhat logical, then that slice of history ('86-'92) had a lot to do with it. It was a great time.

Later at IIT Bombay (95-99) I was introduced to this thing called Unix (which atleast then was the dominant if not only OS on campus), and later during my senior undergrad thesis to Linux. I remember the fun and suffering as the gurus (more "keedas", really) unleashed "write"s to remote machines with ominous messages, popping up "xeyes" on unsuspecting classmates surfing the web for naughty stuff on lynx :). It was my introduction to the networked environment, and I loved it.

During graduate school at Michigan, we were forced in large part to use Apples, which were the only computers with departmental support. Although things did get better after OS X, it wasn't until in 2004, that I switched back to Linux, pretty much full time. Now about 5 years thence, all my machines run some kind of Linux, including the Ubuntu laptop on which I am doing my writing right now.

I am immensely impressed with what I can do, both personally and professionally using extremely high quality and free software (programs on my University webpage). I routinely use Gnuplot, Octave, OpenOffice, GIMP, Maxima (occasionally), awk, JabRef, LaTeX , which run gracefully under Linux. Other things that I like are the (i) ability to automate routine tasks with shell scripts (ii) the ability to schedule jobs and control their priority from anywhere, and (iii) multiple Desktops, which I cannot live without anymore.

There is much more I have to say about this topic, but I'll come back to it later.

Friday, August 22, 2008

Biking to Work

I like to bicycle. It is fun. I do not like red lights during the evening commute. Not fun. I like the idea of going green. I do not like paying $4.00 a gallon of gasoline. I like the idea getting more exercise, in addition to all the furious typing I do during the day. I could go on and fill a library with other stuff I like and do not like, but there is an advantage to stopping right here... because "biking to work" addresses all of them at once. Ever since I moved to Tallahassee in 2006, I've been trying to do that 2-3 times a week, all year around.

And I'm loving it.

It actually started inauspiciously. The very first day I got a flat tire at almost exactly the geometrical mid-point between my source and destination. Compounded by the fact that my wife was still in Ann Arbor, and all the people on my cell-phone still had a (734) area code, I was left with no alternative besides dragging my bike four miles. Luckily, I met a good Samaritan, on the way, who put me and my bike in his truck and gave me a ride home.

The best part of the whole exercise (no pun intended. Don't you absolutely hate it when people pun, and then say no pun intended?) is that after I come back home I feel amazing. All the tightness accumulated by sitting on a chair in front of a computer (as much as I love my job - and I do) for hours untangled, released and transformed to suppleness. It is exactly the opposite of what I feel when I drive to work. For a small town, Tallahassee has terrible traffic, and very few things make me as mad as having to stop at the same traffic signal two times.