In Nature this week

May 3, 2007

  1. An editorial urges scientists to keep e-notebooks and share them;
  2. Joseph Mazur reviews Ian Stewart’s Why beauty is truth: the history of symmetry;
  3. Dirk M Guldi writes about the recent report by Simmons et al of controlling the electrical conductivity of single walled nanotubes using light; such light sensitivity is apparently achieved by filling the nano tubes with photosensitive dyes;
  4. Tim D White pays his tributes to a paleoanthropologist, F Clark Howell.

In Nature this week

April 27, 2007

  1. Of course the big story, as I blogged elsewhere, is the higher dimensional generalizations of the Neumann-Mullins rule of grain growth by MacPherson and Srolovitz:

    Cellular structures or tessellations are ubiquitous in nature. Metals and ceramics commonly consist of space-filling arrays of single-crystal grains separated by a network of grain boundaries, and foams (froths) are networks of gas-filled bubbles separated by liquid walls. Cellular structures also occur in biological tissue, and in magnetic, ferroelectric and complex fluid contexts. In many situations, the cell/grain/bubble walls move under the influence of their surface tension (capillarity), with a velocity proportional to their mean curvature. As a result, the cells evolve and the structure coarsens. Over 50 years ago, von Neumann derived an exact formula for the growth rate of a cell in a two-dimensional cellular structure (using the relation between wall velocity and mean curvature, the fact that three domain walls meet at 120° and basic topology). This forms the basis of modern grain growth theory. Here we present an exact and much-sought extension of this result into three (and higher) dimensions. The present results may lead to the development of predictive models for capillarity-driven microstructure evolution in a wide range of industrial and commercial processing scenarios—such as the heat treatment of metals, or even controlling the ‘head’ on a pint of beer.

  2. Henry Gee reviews The Discovery of the Hobbit: The scientific breakthrough that changed the faceof human history; and, John Hawks is not happy about the review (though he seems to have liked the book)–his review of the review is a must read, at least for sections like these:

    …Gee spends several paragraphs expositing on his own role in the publication of the Homo floresiensis announcement. We learn some interesting little facts, like how the authors wanted to name the species “Sundanthropus floresianus” until a reviewer pointed out that future students would confuse the name with a flowery butt.I kid you not. Nature has a layer of reviewers to take tushie references out of taxonomy. Somehow they can’t tell a left femur from a right, but they’re on the watch for sphincter-species!

  3. How does one weigh molecules, single cell virus, and bacteria whose weight are of the order of a few hundreds of femtograms (and, which are in a solution)? Liesbeth Venema describes a method that has been developed recently and reported in the same issue of Nature.
  4. Martin Campbell-Kelly pays his tributes to John Backus, the inventor of FORTRAN in an obituary piece.

In Nature this week

April 13, 2007

  1. Obituary to Knut Schmidt-Nielsen: McNeill Alexander recalls the man and his work; in the process he summarises the many important discoveries made by Schmidt-Nielsen:
    • Kangaroo rats minimise water loss by producing very concentrated urine, cooling the air that they exhale in the nasal cavity, which was cooled in the first place while inhaling, and living in burrows during day and venturing out only at night;
    • in contrast to kangaroo rats, dogs breathe in through the nose and breathe out through the mouth; thus, they let water vapour to evaporate helping them lose the extra heat generated by exercise;
    • camels avoid water loss by increasing their body temperature as the day progresses, and by drying the air that they exhale using the hygroscopic surfaces of their nasal cavities;
    • sea birds which drink sea water secrete droplets of concentrated salt solutions in their nostrils and shed them by the shake of their heads;
    • unlike mammalian lungs, in the lungs of birds the air-flow is one-way–it enters at one end and leaves another, and the counter current flow of blood and air helps in high rate of oxygen absorption in the blood to power their flight;
    • for a given body mass, swimming is cheaper than flight which is cheaper than running.
  2. Amazing indeed!

  3. Bending crystals by light: Michael McBride, in a news and views piece, writes about the recent experiments of Kobatake et al to use light induced chemical transformation to bend crystals–reversibly, so that they can be bent cyclically:

    The authors grew crystal needles (about 200 \mum long and 5 \mum in diameter) by sublimation so as to be attached at one end to a microscope slide. When illuminated from the side by an ultraviolet laser pulse, the needles bent within a millisecond, displacing the free end by 50 \mum. As a dramatic demonstration of this effect, the needles can launch a tiny gold sphere as if it were a tennis ball…The reversibility of this movement is particularly noteworthy — the needles can undergo 80 cycles of photochemical bending and straightening with no apparent damage to the crystal integrity, nor any diminution in displacement amplitude.

    You can see the movies of the crystal moving gold balls as well as other light induced mechanical movement at the supplementary information page. Wow! is all I can say.

  4. The quantum mechanical basis of photosynthesis: Roseanne Sension, in a News and Views piece, while commenting on the mapping of electronic states using two-dimensional Fourier transform spectroscopy in Fenna–Matthews–Olsen bacteriochlorophyll complex by Engel et al, indicates how energy transfer during photosynthesis is inherently quantum mechanical; she further feels that this discovery might be the key to designing artificial solar energy harvest systems. Considering the fact that

    In higher plants and certain bacterial systems, the initial steps of natural photosynthesis harness light energy with an efficiency of 95% or more,

    this certainly is a very important piece of information to have.

Have fun!