Professor Daraio Wins Presidential Early Career Award
Chiara Daraio, Professor of Aeronautics and Applied Physics, has won a 2012 Presidential Early Career Award for Scientists and Engineers (PECASE). Daraio was recognized for her "pioneering contributions to nonlinear mechanical phenomena in acoustic crystals, granular material, and multifunctional nanostructures, and for mentoring women and providing research opportunities for high school and undergraduate students."
"The entire Caltech community is proud to see Professor Daraio recognized with this presidential honor, not only for her pioneering research accomplishments, but also for her commitment to students and diversity," says Chair Ares Rosakis. "Even though she is near the beginning of her career she already embodies the key attributes of the Division of Engineering and Applied Science at Caltech." [Caltech Release]
Material's Spacing is Key to Brittle-to-ductile Transition
Julia R. Greer, her postdoctoral scholar Dr.Dongchan Jang, and colleagues have used experiments and atomistic simulations of nano-twinned metals (which have the unique combined effect of being strong and ductile) to decipher the specific role of the twin boundaries. They have found that it is the spacing between the twin boundaries that determines whether a material is brittle or ductile as opposed to the sample size, as would be expected. Greer states "this is probably the first study that truly isolated the twin boundaries by making samples which contained only twin boundaries, periodically spaced throughout the sample, and then tested them in tension. This understanding will help in the design of better structural materials and provide a certain amount of predictability in doing so, which has not been possible to date." [Nature Nanotechnology Article and Movies]
The Physics of Going Viral
Rob Phillips, Fred and Nancy Morris Professor of Biophysics and Biology, and colleagues have measured the rate of DNA transfer from viruses to bacteria. They wanted to find out whether pressure plays a dominant role in transferring the DNA. Instead, he says, "What we discovered is that the thing that mattered most was not the pressure in the bacteriophage, but how much DNA was in the bacterial cell." When the bacteriophages try to inject their DNA into the cells, the factor that limits the rate of transfer is how jam-packed those cells are. "In this case," Phillips says, "it had more to do with the recipient, and less to do with the pressure that had built up inside the phage." [Caltech Press Release]