Monday, November 28, 2005

A bit of futurity!

Interested in nano-medicine, and knowing why it would be a blessing and a curse? Here is an article published in Salon titled Nanomedicine's brave new world which might interest you. The article has many rather fascinating passages like this one:
A machine that "shreds" a billion bases of DNA a day could burn through the human genome in 72 hours. Yet we fully expect that this phenomenal accomplishment will be eclipsed within a few years by nanoengineering. Around the world, research teams are closing in on single-molecule DNA sequencing technology. One group has published a design for an instrument that could place a million single-molecule sequencers on a device the size of a postage stamp. To accomplish this, each sequencer will have an operating volume of one zeptoliter -- much less than one billionth of one billionth of a liter! There can be no doubt that within a few years, most individuals will have their genome sequenced and encoded as part of their medical record. And this is just the beginning.
Happy reading!

Sunday, November 27, 2005

Another update: Melting mechanisms!

Do you rememeber the earlier post about melting mechanisms? Here is a very interesting letter by Wang et al published in the May 2005 issue of Philosophical Magazine Letters [vol. 85, no. 5, pp. 213-219(7)], in which they propose a vacancy decomposition induced lattice instability to explain melting. Here is the abstract:
Vacancy decomposition kinetics in crystals at elevated temperatures is analysed. It is found that lattice instability is induced by a significantly enhanced vacancy decomposition at a critical temperature ( T *). The critical temperature coincides with the kinetic instability limit (kinetic limit of superheating) of crystals in a variety of metals determined from the homogeneous nucleation catastrophe model.
While we are on the topic, there is also this paper by Mei et al published in the April 2005 issue of Philosophical Magazine Letters [vol. 85, no. 4, pp. 203-211(9)]; this one is about the kinetic limit of supercooling induced by semicoherent interfaces. Here is the abstract:
The superheating behaviour of embedded particles induced by semicoherent interfaces has been observed in many circumstances. In this paper, a phenomeno- logical model for melt nucleation on misfit dislocations at a semicoherent interface is proposed. A kinetic limit for semicoherent-interface-induced superheating, which is in good agreement with the results of experiments and computer simulations, is derived from this model. Calculations and analyses based on the model reveal that melting prefers to initiate at the semicoherent interface and that superheating of embedded particles is possible for a melt nucleation contact angle less than 90°. Among the matrix-dependent parameters, the contact angle and the shear modulus of the matrix are found to be dominant in determining the superheating of embedded particles.
Not surprisingly, both these papers originate from the same group in Shenyang, China, and both are worth taking a look at.

An update: vacancies and stress!

Svoboda et al have published a paper in the 1st September 2005 issue of Philosophical Magazine Letters [vol. 85, no. 9, pp. 473-479(7)] on the vacancy mediated stress relaxation in misftting precipitates. Here is the abstract, in case you might be interested.
Vacancy diffusion is investigated as a mechanism for relaxation of the elastic strain energy caused by a misfitting inclusion. The kinetics of reduction of the total eigenstrain by the deposition or removal of an atom layer along the interface is derived. The time evolution, as well as an estimate for the characteristic time of the relaxation process, is presented. The relaxation times are compared with recent in situ measurements of stress relaxation times in aluminum with small lead-alloy inclusions after their solidification. Experimentally observed relaxation times and those theoretically predicted agree very well.
The experiments that are being referred to are the same ones that we discussed earlier.

Young-Laplace or Gibbs-Thomson equation

"Every idea in the study of phase transformations can be traced to Gibbs" is a favourite quote of Abi. The latest American Journal of Physics carries an article about the Young-Laplace equation and its derivation, which, in metallurgical literature goes by the name of Gibbs-Thomson equation. I found the following paragraph about the merits of local derivation quite interesting.
A more important point is the character of Young's and Laplace's equations. Because they are local conditions that apply to any portion of the surfaces, a local derivation is more appropriate. From the global approach, one might think that the total energy of the system must be minimal for these equations to be valid, which is not true. The condition of minimum energy is restrictive. If the contact line moves slowly enough (see Sec. III E), Young's equation is obeyed even if the rest of the system (far from the contact line) is not in equilibrium. In contrast, a rigorous global derivation must minimize the energy at constant entropy or the Helmholtz free energy at constant total volume. These additional constraints to the minimization problem should be irrelevant for the derivation of a local equation. Although necessary in the global approach, they may be a source of confusion about whether sigmai is the surface Helmholtz or Gibbs' free energy. (In this respect, the paper by Tolman is enlightening.) In the local approach, the surfaces move without any constraint. In particular, the local derivations are valid even for a nonequilibrium state where the temperature is not homogeneous.
But the conclusion was far more interesting:
In spite of the merits of the local approach, Gibbs' derivation (global approach) seems aesthetically more appealing because all laws governing equilibrium (thermal, chemical, and mechanical equilibrium) are deduced at once. We conclude that the global approach is more suitable if one is interested in the equilibrium conditions of a fluid system, whereas a local approach is preferred for the derivation of Laplace's and Young's equations.
A pedagogical article; well worth the efforts of reading.

Mystique of physics

The latest issue of American Journal of Physics carries Millikan Award lecture of John S. Rigden. An extremely interesting essay - here are some sample quotes:
Against this rich background I ask: Could the people of the 21st century reverse the transformation that occurred 200 years ago by rejecting the methods of science in favor of the assertions by authority?

It is not my purpose to examine the challenges that now confront the science instructor and the science classroom. Today, a number of state legislatures, many state departments of education, and many, many local school boards are currently exerting their authorities as they consider actions that would mandate what is taught and how it is taught in the science classroom. Equally troubling, the very definition of science is being challenged with the goal of bringing into the science classroom material that lies outside the scope of the current definition. This could change science as we know it.

I believe these challenges are serious.

The crucial issue is not the belief in a Divine Designer; in fact, to examine the intricacies of Nature and to see evidence of design is thoroughly rational. The Divine Designer belief is, per se no threat to science. If, however, it is denied that physical laws drive natural processes, if it is denied that physical laws initiate chains of cause and effect that culminate in the beautiful world we observe, if it is denied that science is mechanistic and deterministic, and if these denials become part of the science classroom, then science as we know it is dead. Are the delicate filigrees of frost on a cold window pane caused by anything other than natural mechanism driven by physical law? Are the cosmic wonders revealed by the Hubble space telescope anything other than physical laws working over billions of years?
Debates pitting faith-based beliefs against empirical-based beliefs, have not worked and, in my judgment, will not work. They have not worked because, as always, debates degenerate into point-counterpoint exchanges that only embolden the debaters. Debates heat emotions, but freeze minds. In the context of passionate belief, debating is a negative strategy.
On July 7, 2005, the Roman Catholic cardinal archbishop of Vienna, Christoph Schönborn, laid out the position of the Catholic Church on the subject of evolution. However, the argument the cardinal developed was more general than evolution and implicitly, it embraced all science. In the New York Times the cardinal began by quoting the late John Paul II. "We believe," said the Pope, "that God created the world according to his wisdom. It is not the product of necessity whatever, not blind fate or chance." Cardinal Schönborn concluded: "Scientific theories that try to explain away the appearance of design as the result of `chance and necessity' are not scientific at all, abdication of human intelligence."

Both the Pope and the cardinal denied necessity. Both the Pope and the cardinal are mistaken. If you believe that the physical world is a consequence of physical law, then what we observe is the consequence of necessity. Masses attract out of necessity; energy is conserved out of necessity; the neutron decays out of necessity; and out of necessity, DNA in the gametes determines the characteristics of the resulting organism. There is no choice, there are no alternatives. The laws of physics undergird all science; if the laws of physics, operating out of necessity, are denied in any tributary of science, then the main stream of the entire scientific enterprise is dangerously compromised.

The Enlightenment showed that Reason and the reasoned approach to unlocking the secrets of Nature had enormous appeal to Homo Sapiens, the thinking animal. The physicists of the 19th century brought physics to the forefront of people's thinking and left them with the confidence that the claims of physics could be believed. I suggest we relumine the Enlightenment. I suggest we emulate 19th-century physicists. I suggest we capitalize on the mystique of physics. I suggest we provide students with positive examples that demonstrate what physicists believe and why they believe it.
A nice read; it also contains many ideas to think about and a bit of history, if you are so inclined.

Just can't wait...

This review is so tempting, I just can not wait to lay my hands on the book.

Saturday, November 26, 2005

Mechanical behaviour of metallic glasses

The latest Scripta Materialia carries a viewpoint set on the mechanical behaviour of metallic glasses. Probably, the preface by Prof. Hufnagel is a nice place to begin. To quote from this preface:
Thus, now seems to be an appropriate time to take stock of what we have learned, and to lay out visions for the future of metallic glasses, in terms of both practical applications and new research directions. These are the goals of this viewpoint set, and the papers have been selected with them in mind.

The general enthusiasm for any new class of materials sometimes leads to grandiose claims for the potential of the materials in question. By now, however, enough data has been gathered on a variety of amorphous alloys that we can attempt to replace the hyperbole with more reasoned speculation.
In summary, I believe that this viewpoint set provides a useful snapshot of the current state of knowledge of mechanical behavior of metallic glasses. I fully expect that the future will see continued advances both in our understanding of fundamental aspects of mechanical behavior, as well as new applications of metallic glasses and metallic-glass-matrix composites.
An issue worth taking a look at if your interests are mechanical behaviour and/or metallic glasses.

Pope and mathematician!

Here is a very interesting profile of a Pope who was also a mathematician. Reminded me of what Prof. N. Mukunda used to say about Riesz (I think); a fine mountaineer who also happended to be an analyst!

Return of the singing Neanderthal

Nature reviews The Singing Neanderthals; here is an earlier post about the book.

Wednesday, November 23, 2005

Institute colloquium of Prof. KC!

At the Institute, three to four faculty members are asked to give the Institute Colloquium every year; and, it is considered an honour to be asked. Today, Prof. Kamanio Chattopadhyay, Tata Chem Chair Professor and Chairman of the Department of Metallurgy gave the colloquium.

Prof. KC's talk was about forms, patterns, and crystal structures (or, in short, microstructures) as a result of ordering and repulsion at the atomic level. It was one of the nicest lectures that I have heard. The micrographs that were flashed were of very high quality. Prof. KC also brought out many of the issues and their resolution in microstructural evolution in a simple and easy-to-understand manner. Probably the overcast skies and the rainy weather was the reason for the relatively thin attendance; but, I would not have missed the lecture for anything.

Monday, November 21, 2005

One long argument...

Here is Prof. EO Wilson on Darwin's one long argument, namely, Intelligent Evolution. The essay is wonderful with some extrordinary drawings; a not-to-be-missed piece. You can also download the pdf version of the article, if you are so inclined. Not surprisingly, the essay discusses (and ends with a reference to) evolution and religion:
In any case, the dilemma to be solved is truly profound. On the one side the input of religion on human history has been beneficent in many ways. It has generated much of which is best in culture, including the ideals of altruism and public service. From the beginning of history it has inspired the arts. Creation myths were in a sense the beginning of science itself. Fabricating them was the best the early scribes could do to explain the universe and human existence.

Yet the high risk is the ease with which alliances between religions and tribalism are made. Then comes bigotry and the dehumanization of infidels. Our gods, the true believer asserts, stand against your false idols, our spiritual purity against your corruption, our divinely sanctioned knowledge against your errancy. In past ages the posture provided an advantage. It united each tribe during life-and-death struggles with other tribes. It buoyed the devotees with a sense of superiority. It sacralized tribal laws and mores, and encouraged altruistic behaviors. Through sacred rites it lent solemnity to the passages of life. And it comforted the anxious and afflicted. For all this and more it gave people an identity and purpose, and vouchsafed tribal fitness — yet, unfortunately, at the expense of less united or otherwise less fortunate tribes.

Religions continue both to render their special services and to exact their heavy costs. Can scientific humanism do as well or better, at a lower cost? Surely that ranks as one of the great unanswered questions of philosophy. It is the noble yet troubling legacy that Charles Darwin left us.
Link via PTDR.

I got into computers...

because I was forced to; and, here are some geeks telling how they got into computers. At least one of the stories (by Karl Fogel) is really cool; link via BoingBoing.

Saturday, November 19, 2005

Physics Nobel 2005 controversy

I did not know about this Physics Nobel prize 2005 controversy; Frontline discusses the contributions of Prof. ECG Sudarshan, and Prof. Sudarshan's response.

Friday, November 18, 2005

Bed-time (technical) reading

Your interests might be in knowing the mathematics behind voting models; Einstein's theory of Brownian motion; materials, spintronics and smart structures; the contributions of Hans Bethe to solid state theory; ancient Indian mathematics and astronomy; biology, John Maynard Smith, and evolution. Whatever it be, this is the place to go! And, do not miss this gem of a review by Prof. R. Gadagkar.

Such pleasures, sister... only Resonance can offer!

Thoughts from NMD-ATM

I spent the beginning of this week in Madras attending NMD-ATM. I made a presentation titled Rafting; are elastic stresses alone sufficient to explain it? in the conference. I attended several interesting talks. Among them, the talk of GF Vander Voort on ASTM E1245 standards and Balamuralikrishnan (of DMRL) on AFM deserve a special mention.

I also liked a talk on by Swe-Kai Chen on, hold your breath, Cu-Ni-Al-Co-Cr-Fe-Ti-Mo alloy series, the so-called high entropy alloys (HEA). Apparently, the elemental alloying sequence in such alloys depends primarily on the melting point and the effects of atomic size and crystal structure are secondary. That makes sense since mechanical alloying was used to produce these alloys, and, we know that mechanical alloying is a result of chemical mixing. The bond strength and hence the melting point thus would play a role in deciding the alloying sequence. That gave rise to the question, namely, whether the alloying sequence would depend on the mechanism used to produce the alloys. In other words, are there methods of preparation where the alloying sequence would be determined by atomic size or crystal structure? For example, would radiation induced alloying produce a different sequence?

At the end of Chen's talk, Prof. BS Murty also indicated that the mechanism behind the alloying sequence selection could be the particle size induced reduction in the melting temperature (which is in turn related to the chemical bonding).

Tuesday, November 08, 2005

Tim O'Reilly on open source!

An interview with Tim O'Reilly from BBC about open source - as a podcast or transcript; link via boing boing.

Monday, November 07, 2005

May be I was sleeping!

I did not notice that last week's issue of Nature ran a special edition on sleep; some of the articles were also titled neat; Sleep is of the brain, by the brain and for the brain, one of them said, for example.

The same issue of nature also carries an article by Lindsay Greer and Neil Mathur on the need for an unified approach to the study of chalcogenides, which the materials scientists among you might be interested in taking a look at.

Finally, the essay on this acerbic aphorist is an interesting (and light) read.

Wednesday, November 02, 2005

A bit of romance in a star' s life!

I saw a bright star proposing to another
He was a red giant and she a white dwarf
A million years passed in a while
She still cold at ten thousand degrees Celsius
Not a single kiss in a million years,
And that does not speak well of a star dear
He grew more and more red
She was not willing to go to bed
Then he used his final trick
And exploded as a supernova
And now he and she are together,
And will remain so forever.
-- The proposing star, Dr. V.S.Venkatavardan
Apparently, massive star has a hot partner (at least, according to Science blog); that news brought the above poem to my mind.

Science of water management!