Influence of Strain on the Kinetics of Phase Transitions in Solids

We consider a sharp interface kinetic model of phase transitions accompanied by elastic strain, together with its phase-field realization. Quantitative results for the steady-state growth of a new phase in a strip geometry are obtained and different pattern formation processes in this system are investigated

Evaluation of vacuum bonded GaAs/Si spin-valve transistors

In this article a new type of spin-valve transistor, a hybrid GaAs/Si device, is presented. In this device the Si emitter is replaced by a GaAs emitter launcher structure. The integration of the GaAs with the Si was done by means of a room temperature vacuum bonding technique. By using a soft NiFe/Au/Co spin-valve structure as metal base, a 63% change in collector current is obtained at room temperature for a saturation field of 30 Oe. The corresponding in-plane magnetoresistance is only 1%

Stereo vision enhances the learning of a catching skill

The aim of this study was to investigate the contribution of stereo vision to the acquisition of a natural interception task. Poor catchers with good (N = 8; Stereo+) and weak (N = 6; Stereo-) stereo vision participated in an intensive training program spread over 2 weeks, during which they caught over 1,400 tennis balls in a pre-post-retention design. While the Stereo+ group improved from a catching percentage of 18% to 59%, catchers in the Stereo- group did not significantly improve (from 10 to 31%), this progress being indifferent from a control group (N = 9) that did not practice at all. These results indicate that the development and use of of compensatory cues for depth perception in people with weak stereopsis is insufficient to successfully deal with interceptions under high temporal constraints, and that this disadvantage cannot be fully attenuated by specific and intensive training. © 2007 Springer-Verlag

Droplet Fluctuations in the Morphology and Kinetics of Martensites

We derive a coarse grained, free-energy functional which describes droplet configurations arising on nucleation of a product crystal within a parent. This involves a new `slow' vacancy mode that lives at the parent-product interface. A mode-coupling theory suggests that a {\it slow} quench from the parent phase produces an equilibrium product, while a {\it fast} quench produces a metastable martensite. In two dimensions, the martensite nuclei grow as `lens-shaped' strips having alternating twin domains, with well-defined front velocities. Several empirically known structural and kinetic relations drop out naturally from our theory.Comment: 4 pages, REVTEX, and 3 .eps figures, compressed and uuencoded, Submitted to Phys. Rev. Let

Magnetic phase separation in ordered alloys

We present a lattice model to study the equilibrium phase diagram of ordered alloys with one magnetic component that exhibits a low temperature phase separation between paramagnetic and ferromagnetic phases. The model is constructed from the experimental facts observed in Cu$_{3-x}$AlMn$_{x}$ and it includes coupling between configurational and magnetic degrees of freedom which are appropriated for reproducing the low temperature miscibility gap. The essential ingredient for the occurrence of such a coexistence region is the development of ferromagnetic order induced by the long-range atomic order of the magnetic component. A comparative study of both mean-field and Monte Carlo solutions is presented. Moreover, the model may enable the study of the structure of the ferromagnetic domains embedded in the non-magnetic matrix. This is relevant in relation to phenomena such as magnetoresistance and paramagnetism.Comment: 12 pages, 11 figures, accepted in Phys. Rev.