Friday, September 30, 2005

Tool use and gender!

Here is an update on tool use, this time around in chimpanzees.The article also has a comment on my observation about gender differences:

...and that young males are relatively delayed in the social learning of termite fishing, our results show that both sexes can show strong social learning and continue to do so into adulthood.

Long back, I read about Betty and her (lazy and exploitative) partner Abel. Now, from here, I learn about two female gorillas who are adept at tool use. Makes me wonder if females are better innovators; or, is it too stereotypical (and sexist) a comment to make?

Tuesday, September 27, 2005

Mechanisms of melting!

Melting and solidification are probably the most ubiquitous temperature driven phase transformations. As we increase the temperature of a solid, at a particular temperature known as the melting temperature, the solid becomes a liquid. On the other hand, if we keep decreasing the temperature of a liquid, at a particular temperature known as the freezing temperature, the liquid becomes a solid. However, under some circumstances, it is possible to keep a solid above its melting temperature in the solid state: this is known as superheating. Similarly, keeping a liquid below its freezing temperature in the liquid state is known as supercooling.

The assumption that melting starts at the interior amounts to assuming homogeneous nucleation of melting; surfaces, or grain boundaries, if present will be spots of easy melting, and in such cases the melting is said to nucleate heterogeneously. In fact, the fact that the surface melts easily is what leads to a size dependence of the melting temperature, which is being widely studied by the nanomaterials community these days.

Thanks to Deep for pointing out that (a) what Born and Lindemann proposed are criteria; and, (b) unless extreme care is taked to avoid it, melting nucleates, almost always, heterogeneously.

The mechanism of melting, however, is yet to be clearly understood. Consider a crystalline solid and assume that the melting starts in its interior. As temperature of the crystal increases, its shear modulus (and hence its ability to withstand non-hydrostatic stresses) decreases. Melting could then be that point where the shear modulus becomes zero. This shear-induced melting criterion was proposed by Born. As the temperature increases, the atoms in their lattice positions start vibrating more and more violently. Finally, at the melting temperature the vibrations are so violent that the crystalline lattice structure breaks down leading to melting; this criterion was proposed by Lindemann. The third criterion involves the production of defects in a solid with increasing temperatures. At the melting point, the defect concentration is so large that it leads to the destruction of the crystalline lattice, and hence to melting. Over the years, there had been several studies which discuss these different mechanisms. Deep referred me to this recent article in the May, 2005 issue of Nature Materials on some molecular dynamics studies of melting in superheated crystals. Here are some pointers to some of the earlier literature on these different mechanisms of melting. Finally, here is a nice post by Santonu on defects in solids, albeit with an emphasis on segregation.

Friday, September 23, 2005

Junta like nano and nanoparticles jump (with joy?)!

So, here is the good news: junta do not perceive nano-technology as a threat, though there are concerens about lack of information and regulation. This reminded me of this article in the August 2004 issue of PhysicsWeb. But, how does the scientific community itself perceive nano? Take a look at this editorial in the February 2005 issue of Materials Today. And, go here to learn about jumping gold nanoparticles!

Wednesday, September 21, 2005

A quick Resonance update!

The fluid dynamics feast continues: the second part of Prof. Roddam Narasimha's fluid dynamics article - subtitled 'what one can and can not do' is out in the latest issue of Resonance. Did I tell you about a bit of geometry in everybody's life?. The September 2005 issue of Resonance also carries an article by Kamala Datta on 'The early life of Albert Einstein' where we read:
When Einstein was twelve he got hold of a 'small book on geometry' at the beginning of the school year which he studied on his own and which, in Einstein's own words"made an indescribable impression" on him.
I got my print copy of resonance this morning by snail mail - hope the online version will soon be uploaded here. But why wait? Why not grab a print copy for yourself? Better still, why not subscribe?

A birds, bees, wasps, and ants talk!

Apparently, eusocial means 'truly social'; and, it is not a classification of political leanings but that of the behaviour of insect communities. There are a few short articles here by Prof. Raghavendra Gadagkar about eusociology (and many other things besides - when fathers harass their sons is my particular favourite). In fact, his book Survival strategies is a must read for anybody interested in biology (in general, and, animal behaviour, in particular. Here is a very accesible summary of the book). A more technical article on eusociality by Prof. E.O. Wilson and Hoelldobler, is published in the latest PNAS.

Tuesday, September 20, 2005

Googling as research!

More things are wrought by Google than the academe dreams of!
-With due apologies to Tennyson

I understand that a computer programmer, with the help of Google Maps and Google Earth 'has stumbled upon the remains of an ancient villa': for the complete story, go here. Gone are the days of serendipity favouring the prepared mind, my boy - nowadays, it favours just the googling mind;-)

Monday, September 19, 2005

A bit of geometry in everybody's life!

Euclid is credited with the famous remark, namely, that there is no royal road to geometry. Royal road or common road, geometry has played a crucial role in the development of twentieth century physics; the role of geometry in the theory of relativity is well known (See this wonderful article in Resonance, for example). Apparently, PAM Dirac, who believed in a deeper connection between mathematics and nature, insisted that his approach to quantum mechanics was geometric and not algebraic: take a look at this essay. While we are on the topic of geometry, here is a delightful essay on the evolution of Riemann's geometric ideas published in the January, 2005 issue of American Mathematical Monthly. The final geometry link (I just couldn't resist it): here is a song about that other geometry guy, Lobachevsky by Tom Lehrer. And, hey, have you visited this page anytime?!

Wednesday, September 14, 2005

India, genomically speaking!

We have heard time and again about the diversity that is India, and the unity that makes us Indians. Here is a review of a project called Indian Genome Variation database from the IGV Consortium. From their review article, I understand that the four major morphological types of the Indian population is Caucasoid, Mongoloid, Australoid, and Negrito; and, linguistically, the four major language families are, apparently Indo-European, Dravidian, Tibeto-Burman, and Astro-Asiatic. The two maps of India delineating the regions of these different morphological and linguistic types are worth taking a look at. The ultimate aim of this project is
'to create a DNA variation database of the people of India and make it available to researchers for understanding human biology with respect to disease predisposition, adverse drug reaction, population migration etc'.
The review also discusses some of the ethical issued involved and the data release policy. An article worth taking a look at.

Tuesday, September 13, 2005

Medium, message, and meaning!

Friends, after the previous post about nano-bio, it is time to talk about info, isn't it? I found this paper in the Journal of the American Society for Information sciences, thanks to CiteULike. The paper, enigmatically titled 'What is a "document"?', discusses several descriptions, and the 'confusions between medium, message, and meaning'. Apparently,
The Indian theorist S.R. Ranganathan, usually so metaphysical, took a curiously narrow and pragmatic position on the definition of the "document",...
A good read on the whole, which tells you, why it is no longer 'documentation' but 'information management'!

Crooks fluctuation theorem?

There are several reasons why you should read this article about the experimental verification of Crooks fluctuation theorem. For starters, the article begins with stirring a cup of coffee - though I do not agree with the conclusion, viz, 'Stir a cup of coffee with a small enough spoon, and the coffee might just stir you' - A cup of coffee always stirs me, irrespective of whether I stir it or not (By the way, that link to Wiki-coffee is just for the photograph and entry of the Madras filter coffee on that page). Second, it is about a nano-bio - as hot (and I hope, as wonderful) as coffee these days. Finally, it is about that classic science of thermodynamics, and the verification of a fluctuation theorem called Crooks fluctuation theorem - The experiments are sort of cute, and I understand that the technique that is used in the experiment might be valid for most biological molecules.

So, what is it all about? WP Wong and E Evans write about the experiments of Collin et al with RNA molecules using atomic force microscopes and optical tweezers. The aim: to verify the Crooks fluctuation theorem, which, I understand, posits the likelihood of 'dissipation-free' processes in small enough systems. The verdict: Crooks fluctuation theorem does hold in the case of unfolding and refolding of single RNA molecules.

One of the authors, Carlos Bustamante is interviewed by Nature, and he says that they did 35 drafts before submitting the paper. 35 drafts... for Chrissake. That killed me. I only hope Abi is not listening!

Tuesday, September 06, 2005

A Gardner update!

The second part of the interview with Gardner is out in the September 2005 issue of College Mathematics Journal . Don't miss the photograph of Martin with Alice in the Central Park (And, what do you think Gardner's Erdos number is? - All I can tell you is that it is a prime!!)

An update on the update: meta-update if you will

Here is a link to GK Chesterton 's The Man who was Thursday that Gardner strongly recommends. Margaret Mead believed in UFOs! Truth is stranger than fiction. Or, is it yet another Mead hoax ?

Blogging as a scientific activity!

Blogging is known to be a social activity. But is it also a scientific activity? I today saw this site, meant specifically for blogging science oriented stuff: the topics include geoscience, nano science, physics, space, computer science, and, anthropology among others!

Monday, September 05, 2005

Woodpeckers, civilization, and programming!

According to Eric Raymond , Gerald Weinberg , is the one who made the observation (in 1971 - Boy! Were I born then?) that "If architects built houses the way programmers built programmers, the first woodpecker to come along would destroy civilization". So, bugs, reproducibility, and reliability are issues, probably, as old as programming itself.

The January, 2005 issue of Physics Today carries an article (by Post and Votta) on the need of verifying and validating complex codes. After noting that
The existing peer review process for computational science is not effective. Seldom can a referee reproduce a paper's result.
Post and Votta go on to say
One has to validate the entire calculational system-- including user, computer system, problem setup, running, and results analysis.
As we noted earlier , the measures suggested here would help in making sure that not just the referee but every reader can reproduce the computations. Not surprisingly, the article of Post and Votta received lots of feedback, which are published in the August, 2005 issue of Physics Today : however, I have to wait at least for three months before they would be available online. Till then, you can take a look at the September/October, 2004 issue (Volume 6, Issue 5) of IEEE Computing in Science and Engineering which is a special issue on validation and verification (and also has a provocative editorial about the predictive powers of computers).

Saturday, September 03, 2005

Noble aspirations!

Frankly, which one of us have not dreamt of it? Here is how to win a Nobel prize : a link that I got from here .

Thursday, September 01, 2005

Movie of a "super"b material!

Helium-4 becomes a superfluid at temperatures below 2 K or so; it is also possible to prepare a Helium-4 crystals by the application of pressure to a cell that contains liquid Helium-4 (which, apparently, is done using piezo-electric cells). I am reading at present about some experiments on the Helium-4 crystals: here is a review by Prof. Balibar and his co-workers (You can also get the review from Prof. Baliabar's personal page). Do not miss the superb movie on the roughening transition and crystallization waves in Helium-4. Till now I only knew about the flow properties of Helium-4. After this movie (and the review), I feel, if liquid Helium-4 is "super", the solid form of Helium-4 is "superb": wouldn't you agree?