Fascinating paper. Congrats to Wei, Xuanhe, and Zhigang. Nice to see a simple and an elegant model together with an intuitively appealing physical interpretation of the bifurcation phenomenon in gels. It woud be interesting to see the time evolution of the drying process and the orientation (theta) of the nano wires.
A polymer network can imbibe water from environment and swell to an equilibrium state. If the equilibrium is reached when the network is subject to external mechanical constraint, the deformation of the network is typically anisotropic, and the concentration of water inhomogeneous. Such an equilibrium state in a network constrained by a hard core is modeled here with a nonlinear differential equation. The presence of the hard core markedly reduces the concentration of water near the interface and causes high stresses.
Hydrogels have enormous potential for making adaptive structures in response to diverse stimuli. In a structure demonstrated recently, for example, nanoscale rods of silicon were embedded vertically in a swollen hydrogel, and the rods tilted by a large angle in response to a drying environment (Sidorenko, et al., Science 315, 487, 2007). Here we describe a model to show that this behavior corresponds to a bifurcation at a critical humidity, analogous to a phase transition of the second kind.
At 71, Physics Professor Is a Web Star
Most frequently e-mailed by NYTimes.com readers in the past 30 days, the above article features MIT physics professor, Walter H. G. Lewin, on how his free physics lecture videos online have won him devotees all over the world.
EPFL continues to strengthen its School of Architecture, Civil and Environmental Engineering (ENAC). We are recruiting an assistant professor (tenure track) in structural engineering. In special cases, a senior faculty appointment could be considered. We are seeking exceptional candidates with a strong interest in teaching and an outstanding record of scientific accomplishments.
I had promised to talk about subversion in my post on digitizing and editing figures but never quite got around to it. A recent spate of requests about downloading Uintah reminded me of my promise. So here's the story.
Dear Colleagues:
We invite you to submit an abstract in our mini-symposium titled
Length Scale Effects in Dynamic Failure of Materials
at
8th. World Congress on Computational Mechanics (WCCM8)
5th. European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008)
June 30 - July 4, 2008
A new type of elasticity of random (multifractal) structures is suggested. A closed system of constitutive equations is obtained on the basis of two proposed phenomenological laws of reversible deformations of multifractal structures. The results may be used for predictions of the mechanical behavior of materials with multifractal microstructure, as well as for the estimation of the metric, information, and correlation dimensions using experimental data on the elastic behavior of materials with random microstructure.
Professor Y. C. Fung, Professor Emeritus of Bioengineering at UC San Diego's Jacobs School of Engineering, is the recipient of the Fritz J. and Dolores H. Russ Prize of 2007.
The Russ Prize is presented biannually to an outstanding candidate in the field of bioengineering who has made significant contributions to improving the human condition through research, development, teaching, or management. The recipient receives a $500,000 cash award and an engraved gold medallion.
