Archive for the ‘Science’ Category

Supersolid Helium and beating the diffraction limit

May 11, 2010

Two interesting pieces in Physics.

S Balibar writes about some new results in the study of supersolid phase transition in Helium:

Six years have passed since Kim and Chan [1,2] discovered supersolidity when they found that solid 4He does not rotate like a classical solid. Despite substantial effort, however, this phenomenon is not yet understood [3]. Some probably think that the research on this puzzling issue is too slow. Others, including myself, enjoy every new controversy and every new advance as if they were reading a detective story. In this tale, the latest twist is a study reported in Physical Review Letters by Oleksandr Syshchenko, James Day, and John Beamish at the University of Alberta, Canada [4], of the shear modulus of solid 4He in the temperature range where it becomes supersolid. They confirm that the observed change in stiffness is associated with a binding of dislocations to 3He impurities (Fig. 1) when the solid is cooled down (then unbinding when warming up, of course) and they show now that this binding is gradual because there is a rather wide distribution of binding energies. Why is this so important?

Blom and Widengren write about an optical microscope that beats the diffraction limit:

The classical view that lens-based optical microscopes cannot resolve details separated by less than half the wavelength of light is increasingly becoming a dated one. Several microscopy techniques, used either alone or in combination, can now beat the diffraction limit by at least a factor of 2. Now, in a paper appearing in Physical Review Letters, Claus Müller and Jörg Enderlein at Georg August University in Göttingen, Germany, add to this arsenal of techniques a method that essentially involves modifying an existing bench-top confocal-laser scanning microscope [1]. This type of microscope—called a CLSM for short—is already a fundamental tool for research, particularly in the biological sciences, and Müller and Enderlein’s proposal could influence a broad community.

Both the pieces are not only interesting but also written in a nice fashion; take a look!

Athletics and their brains

April 25, 2010

The brain begins by setting a goal—pick up the fork, say, or deliver the tennis serve—and calculates the best course of action to reach it. As the brain starts issuing commands, it also begins to make predictions about what sort of sensations should come back from the body if it achieves the goal. If those predictions don’t match the actual sensations, the brain then revises its plan to reduce error. Shadmehr and Krakauer’s work demonstrates that the brain does not merely issue rigid commands; it also continually updates its solution to the problem of how to move the body. Athletes may perform better than the rest of us because their brains can find better solutions than ours do.To understand how athletes arrive at these better solutions, other neuroscientists have run experiments in which athletes and nonathletes perform the same task. This past January Claudio Del Percio of Sapienza University in Rome and his colleagues reported the results of a study in which they measured the brain waves of karate champions and ordinary people, at rest with their eyes closed, and compared them. The athletes, it turned out, emitted stronger alpha waves, which indicate a restful state. This finding suggests that an athlete’s brain is like a race car idling in neutral, ready to spring into action.

Del Percio’s team has also measured brain waves of athletes and nonathletes in action. In one experiment the researchers observed pistol shooters as they fired 120 times. In another experiment Del Percio had fencers balance on one foot. In both cases the scientists arrived at the same surprising results: The athletes’ brains were quieter, which means they devoted less brain activity to these motor tasks than nonathletes did. The reason, Del Percio argues, is that the brains of athletes are more efficient, so they produce the desired result with the help of fewer neurons. Del Percio’s research suggests that the more efficient a brain, the better job it does in sports. The scientists also found that when the pistol shooters hit their target, their brains tended to be quieter than when they missed.

Good genes may account for some of the differences in ability, but even the most genetically well-endowed prodigy clearly needs practice—lots of it—to develop the brain of an athlete. As soon as someone starts to practice a new sport, his brain begins to change, and the changes continue for years. Scientists at the University of Regensburg in Germany documented the process by scanning people as they learned how to juggle. After a week, the jugglers were already developing extra gray matter in some brain areas. Their brains continued to change for months, the scientists found.

From this piece of Carl Zimmer. Link via Swarup.

Shape of a long leaf

December 30, 2009

An interesting one from H Liang and L Mahadeavan:

Long leaves in terrestrial plants and their submarine counterparts, algal blades, have a typical, saddle-like midsurface and rippled edges. To understand the origin of these morphologies, we dissect leaves and differentially stretch foam ribbons to show that these shapes arise from a simple cause, the elastic relaxation via bending that follows either differential growth (in leaves) or differential stretching past the yield point (in ribbons). We quantify these different modalities in terms of a mathematical model for the shape of an initially flat elastic sheet with lateral gradients in longitudinal growth. By using a combination of scaling concepts, stability analysis, and numerical simulations, we map out the shape space for these growing ribbons and find that as the relative growth strain is increased, a long flat lamina deforms to a saddle shape and/or develops undulations that may lead to strongly localized ripples as the growth strain is localized to the edge of the leaf. Our theory delineates the geometric and growth control parameters that determine the shape space of finite laminae and thus allows for a comparative study of elongated leaf morphology.

Take a look!

Science books for kids

November 27, 2009

Here is a list; via Swarup.

Science can, at times, feel like religion

November 10, 2009

Zuska explains how:

Wilson wasn’t saying science IS a religion in the sense that there’s no real underlying objective reality, everything’s all taken on faith, and we all get together and worship the Flying Spaghetti Monster at Friday seminar. But Jesus Christ, I was a grad student once, and I’ll be damned if there weren’t aspects of that experience that weren’t more than a little bit like being indoctrinated into some sort of crazy cult worship. There was a brilliant Chronicle piece some years ago by Thomas Benton analyzing the correspondence between grad school and religious cults. He was speaking about humanities students but, as I recall, it was all the rage with science and engineering students as well. Read it and see if you don’t find it chillingly applicable. My point is: what we do at the lab bench is Science. What we do socially, to each other, when we are not at the lab bench (and sometimes even when we are) can sometimes take on characteristics that very much feel like Science as a Form of Religion.

A thousand years ago, when I was a graduate student, we often used to grumble and joke amongst ourselves about the “sacred priesthood of science”. How you basically had to give up your whole life (including sex, because when did you have time for that?), and take a vow of poverty, to pursue your work. How you had to demonstrate your undying devotion to Science above all other things. And, of course, for us women, the sacred priesthood joke had special resonance, because damn, there were just so doggone many priests running the show and precious few priestesses to be found anywhere in the temples.

Imagine my surprise and amusement, some years later, to discover that our long-running joke had real roots in the way that Western science itself grew out of the ascetic tradition of the medieval Latin church – see: David Noble, A World Without Women: The Christian Clerical Culture of Western Science. There I was in grad school, joking about being inducted into the sacred priesthood of science – and here came David Noble to explain how Western science was shaped by and formed on a monastic model, designed in part specifically to exclude women.

Noble goes beyond this thesis of science as a religious calling in The Religion of Technology: The Divinity of Man and the Spirit of Invention.

For social historian Noble…Western culture’s persistent enchantment with technology finds its roots in religious imagination. Despite their varied guises and pursuits, science and technology suggest nothing more than our “enduring, other-worldly quest for transcendence and salvation.” The pearl of great value is Noble’s contention that science and technology aren’t guilty of amorality: that was never the intent. Rather, he claims, new technologies aren’t about meeting human need; they transcend it. Salvation through technology “has become the unspoken orthodoxy.” Such is the new Gnosticism. This is a dense, fascinating study of technology and Christianity. Not satisfied with easy equivalencies, Noble challenges the idea of post-Enlightenment science as a secular brave new world and quietly offers that what we’re really hoping for is our reentry into Eden.

Noble is hardly the first historian of science to delve into the ways in which science functions as a religion (though no in the way those crazy Intelligent Designers like to think). But I particularly love what he does in exploring how the ways in which Western science’s birth in the monastic tradition has had long-lasting effects for women’s participation in science.

There are many reasonable, sound, scholarly bases for examining the idea of how science might function as a religion functions, or how it might work to meet needs and fill roles that are in other cases met and filled by what we more normally think of as religions. It might seem scary to ask those sorts of questions in a time where people who have decidedly, virulently anti-science agendas (and deep pockets to help carry them out) wish to put forth their own poisonous notion that science is just another religion so that they can pour their religion into science classrooms and control the agenda of science. But I’d like to think that at least amongst scientists, we can have a conversation about science as science, as cultural practice, as an institution. That we can step back and critically examine what it is we do day in and day out.

If you think the concept of science as a religion is just sooooooo unbearably stupid, high school debate, not-worthy of ScienceBlogs, it may not be the concept that’s ignorant. Just possibly, there’s a whole wealth of information out there to ponder that you are completely unaware of.

Take a look!

The Copernicun grave mystery

July 29, 2009

A must-read piece from the latest PNAS:

When in 2005 Polish archaeologists led by Jerzy Gassowski found fragments of a skeleton tentatively identified as the remains of the 16th-century astronomer Nicolaus Copernicus, some doubts remained. Now, in this issue of PNAS (1), these issues are resolved with high confidence through DNA analysis.

Take a look!

Links: a movie, a reflection on careers, and “Software is dead: long live the software”

July 20, 2009

[1] Mark at Cosmic Variance recommends a movie:

Projects like this don’t change the world on their own, of course. But as part of a common goal of bringing a passion for science to the public, and allowing them to see that its practitioners and enthusiasts are drawn from all walks of life they play an important role; not only for science, but for our increasingly science-dependent society. It doesn’t hurt that Shaha is young and good-looking, but what shines through is his infectious energy and enthusiasm for science and the important role of skepticism. And that’s what I hope anyone watching this film takes away.

[2] The most recent, and must-read post of Bruce Eckel begins thus:

I’ve taken Robert McKee’s screenwriting workshop a couple of times (didn’t get it all the first time around). One of his maxims is “when you’re stuck, do research.” Mostly that’s meant reading books on management (primarily software management) but also general business books.

While at the library, a book practically fell off the shelves. Never one to ignore signs, I checked out Alan Webber’s Rules of Thumb. He was one of the founders of Fast Company, the only magazine I’m still (voluntarily) subscribed to (I keep meaning to resubscribe to Wired, though). The magazine stimulates my thinking and opens my horizons.

Rules of Thumb is subtitled “52 truths for winning at business without losing yourself.” It has that “bathroom reader” appeal, since each point/chapter can be absorbed in a short time and stands alone from the rest of the book.

I got stuck at point #6: If you want to see with fresh eyes, reframe the picture.

[3] Intimation of the death of software:

I was utterly floored when I read this new IEEE article by Tom DeMarco (pdf). See if you can tell why.

My early metrics book, Controlling Software Projects: Management, Measurement, and Estimates [1986], played a role in the way many budding software engineers quantified work and planned their projects. In my reflective mood, I’m wondering, was its advice correct at the time, is it still relevant, and do I still believe that metrics are a must for any successful software development effort? My answers are no, no, and no.I’m gradually coming to the conclusion that software engineering is an idea whose time has come and gone.

Software development is and always will be somewhat experimental. The actual software construction isn’t necessarily experimental, but its conception is. And this is where our focus ought to be. It’s where our focus always ought to have been.

If your head just exploded, don’t be alarmed. Mine did too. To somewhat reduce the migraine headache you might now be experiencing from reading the above summary, I highly recommend scanning the entire two page article pdf.

I guess it is a good reading list for a Monday morning. Have fun!

Some math-y links

July 7, 2009

All the following are from Notices of AMS (and, pdf):

  1. Solving Sudoku puzzles — paper and pencil algorithm
  2. TeX family in 2009
  3. LaTeX — breaking free!
  4. Mathematical models in science and engineering
  5. A special issue on formal proof
  6. Last poem of James Clark Maxwell (This one is a real gem!)

Have fun!

Issac Newton turns an investigator and sand turns into a liquid

July 6, 2009

Sean at Cosmic Variance strongly recommends Thomas Levonson’s book Newton and the counterfeiter:

The 1690’s was a transformative time for the English currency system, including the introduction of paper money, trade imbalances with the Continent, massive debts run up by William III’s wars in France, and an epidemic of counterfeiting and “coin-clipping,” by which people would shave off the edges of silver coins and melt them down to make new ones. In response, the Mint eventually gave in and undertook a comprehensive re-coinage — a program that was on track to become a complete fiasco until Newton stepped in. Remember that he was not simply an abstract theorist (although he was that); Newton was an extraordinarily careful experimenter, and he turned his practical side to the problem of re-coinage, with spectacular results.

But the real fun comes in when Newton takes on Chaloner, one of the most notorious counterfeiters of the day. I don’t want to give away too much, because you really should buy the book. Suffice it to say that where Newton was gifted with an extraordinary intellect and a relentless work ethic, Chaloner was gifted with what we would today call “balls.” No scheme was too audacious to be undertaken, no lie was too grandiose to be told, no collection of co-conspirators was too extensive to be betrayed or turned against each other. Chaloner was a colorful character, whose story would have made entertaining reading no matter what era he was born into. But he made one unforgivable mistake: he attracted the particular ire of Isaac Newton, who turned the full force of his powers to tracking this miscreant down and bringing him to justice. Chaloner’s own gifts notwithstanding, it was not a fair fight.

We tend to look at successful people and imagine that they are defined by their sphere of success. It’s hard for us today to think of Isaac Newton as anything other than a scientist. But he was good at what he did, whether it was piecing together the mysteries of classical mechanics or paying informers to spy on suspected criminals. Gil Grissom would approve — maybe not of all his methods, but certainly of his results.

In Cosmic Variance again, Mark writes about some cool properties of sand — like their turning into droplets while falling for example — with videos.

Have fun!

Creep in concrete, shear induced melting, and temporal lenses

July 2, 2009

Few papers from the latest PNAS:

[1] Nanogranular origin of concrete creep

M Vandamme and F-J Ulm

Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C–S–H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C–S–H forms: low density, high density, ultra-high density. We demonstrate that the creep rate (≈1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years.

[2] Melting and crystallization of colloidal hard-sphere suspensions under shear

Y L Wu et al

Shear-induced melting and crystallization were investigated by confocal microscopy in concentrated colloidal suspensions of hard-sphere-like particles. Both silica and polymethylmethacrylate suspensions were sheared with a constant rate in either a countertranslating parallel plate shear cell or a counterrotating cone-plate shear cell. These instruments make it possible to track particles undergoing shear for extended periods of time in a plane of zero velocity. Although on large scales, the flow profile deviated from linearity, the crystal flowed in an aligned sliding layer structure at low shear rates. Higher shear rates caused the crystal to shear melt, but, contrary to expectations, the transition was not sudden. Instead, although the overall order decreased with shear rate, this was due to an increase in the nucleation of localized domains that temporarily lost and regained their ordered structure. Even at shear rates that were considered to have melted the crystal as a whole, ordered regions kept showing up at times, giving rise to very large fluctuations in 2D bond-orientational order parameters. Low shear rates induced initially disordered suspensions to crystallize. This time, the order parameter increased gradually in time without large fluctuations, indicating that shear-induced crystallization of hard spheres does not proceed via a nucleation and growth mechanism. We conclude that the dynamics of melting and crystallization under shear differ dramatically from their counterparts in quiescent suspensions.

[3] Temporal lenses for attosecond and femtosecond electron pulses

S A Hilbert et al

Here, we describe the “temporal lens” concept that can be used for the focus and magnification of ultrashort electron packets in the time domain. The temporal lenses are created by appropriately synthesizing optical pulses that interact with electrons through the ponderomotive force. With such an arrangement, a temporal lens equation with a form identical to that of conventional light optics is derived. The analog of ray diagrams, but for electrons, are constructed to help the visualization of the process of compressing electron packets. It is shown that such temporal lenses not only compensate for electron pulse broadening due to velocity dispersion but also allow compression of the packets to durations much shorter than their initial widths. With these capabilities, ultrafast electron diffraction and microscopy can be extended to new domains,and, just as importantly, electron pulses can be delivered directly on an ultrafast techniques target specimen.