New Horizons

Beautiful movie of Venus passing in front of the Sun at various optical wavelengths. May be you know that observing at a given wavelength is like watching the Sun at a given depth. Not just optical depth, but it's really like seeing inside the Sun peeled.  A must watch ! I love gamma rays, uhhh. Source APOD

For our greatest delight (at least mine), Andrew Lipson is a crazy guy. He's building many funny things in Lego. Like topological surfaces, Klein bottle, from the in/out-side ! Escher pictures, waterfall Or scultpures, like Rodin's thinker However, lego construction may be a way to counter-act the financial crisis which has the inconvenient to cut funding in research laboratory. For instance, Daniel strange (I don't invent anything !) built and programmed a crane that moves in a set path, raising and lowering the sample between beakers containing solutions using a Lego Mindstorms NXT kit. Neat.

You can get very interesting result when plotting different linear combination of eigenfunctions of the Laplacian on a given (convex) shape. Here I use a square plate [0,1] by [0,1] and show the zero iso-value of the some of such linear combination. As time evolves, the linear combination changes. Since the Eigenfunctions are symmetric, I only plot them on the [0, 0.5] interval.  In that case, the eigenfunction are of the form With (n1,n2) such that The associated eigenvalue l= 340*pi^2 is of multiplicity 4 (12,14) (18,4) (14,12) (4,18). Below, same thing with l = 5525 which is of multiplicity 12. Those isocontours are called nodal lines. By the unique continuation property, those nodal lives consist of curves in the interior of the domain (her a square, but the result is valid for any convex shape) which are infinetly differentiable. You may also note, but that is a well known theorem, that when nodal lines interesect a boundary (except may be at corner points...

Yesterday evening, too bored by what TV was proposing to me, I decided to watch a conference of Mathias Fink , a french researcher working on multidisciplinary application of waves. Specially shear waves.  Here is a brief summary of his talk. In solids, waves have two principal components:  compression waves (P-waves for primary) moving in the direction of propagation, and shear waves (S-waves, for secondary) that make ripples in the plane orthogonal to that direction. Since compression waves propagate in the direction of propagation, they move faster than shear waves. Usually ultrasound equipment in medicine only use compressional waves. But since human tissues have a high bulk modulus, the P-wave speed is relatively constant (around 1580 m/s). Human tissues are very stiff if you apply isotropic constraints on them (like pressure of water). However M. Fink and his colleagues proposed a new way to investigate human tissues by first sending a strong compressional wave in ...

As usual, I started this morning by browsing arxiv, watching for article that would potentially have the ability to wake me up from my sleepiness. And I found 'Asymptotic rate of quantum ergodicity inchaotic Euclidean billiards'   with the following picture that shocked me. This image results from tracing cumulative plane wave with random orientation, but same wave-number on a square domain and I found strinking how similar to simulation s in cosmology it was. The second image result from simualtion and we see density fluctuation of a simulated universe. The filaments represent families of galaxies, and black zone, the emptiness of space.

For more than a year or so, I am completely amazed to realize that what I would call the random approach , both in terms of computational algorithm and hardware design, has unexpected but very encouraging properties. Microprocessor come up with a many error-correcting processes, using a large amount of overall CPU resources (energy, wall-clock time, etc). By allowing the hardware to make a few mistakes, managed to be under some probability law, scientists of the Rice-NTU Institute for Sustainable and Applied Info dynamics (ISAID) lead by Krishna Palem, showed that significant gain could be possible, both in term of energy demand and performance. Also by trimming away ( pruning in the jargon) some rarely used portions of the chip and confining locally voltage requirements researchers  have been able to take advantage in energy requirements. “In the latest tests, we showed that pruning could cut energy demands 3.5 times with chips that deviated from the correct valu...

As you probably may (or may not!) know, molecular biology often study biological functions from interaction network between molecules rather than studying each component one-by-one. It's the opposite of the universal divide-and-conquer strategy, I would call it the all-inclusive strategy. Those interactions networks involves myriads (10.000) of molecules that interacts by various chemical ways, which is generally represented as an oriented graph between each molecular compound. The transcriptional networks describe the relationship between genes and proteins, the protein-protein network s defines the cascades of interactions between some, ingenuously lumped, proteins, the metabolic networks attempt to mimic the flush of metabolic reactions inside living organisms.  So the idea is to understand how the  main 'thing' works from all those interactions linked together. Of course, other kind of networks are used in many different domain to study more-or-less linked ...