10 research outputs found
A Coupled Equations Model for Epitaxial Growth on Textured Surfaces
We have developed a continuum model that explains the complex surface shapes
observed in epitaxial regrowth on micron scale gratings. This model describes
the dependence of the surface morphology on film thickness and growth
temperature in terms of a few simple atomic scale processes including adatom
diffusion, step-edge attachment and detachment, and a net downhill migration of
surface adatoms. The continuum model reduces to the linear part of the
Kardar-Parisi-Zhang equation with a flux dependent smoothing coefficient in the
long wavelength limit.Comment: 11 pages, 4 figures. Submitted to the Journal of Crystal Growt
Vortex dynamics and states of artificially layered superconducting films with correlated defects
Linear resistances and -characteristics have been measured over a wide
range in the parameter space of the mixed phase of multilayered a-TaGe/Ge
films. Three films with varying interlayer coupling and correlated defects
oriented at an angle from the film normal were investigated.
Experimental data were analyzed within vortex glass models and a second order
phase transition from a resistive vortex liquid to a pinned glass phase.
Various vortex phases including changes from three to two dimensional behavior
depending on anisotropy have been identified. Careful analysis of
-characteristics in the glass phases revealed a distinctive and
-dependence of the glass exponent . The vortex dynamics in the
Bose-glass phase does not follow the predicted behavior for excitations of
vortex kinks or loops.Comment: 16 pages, 10 figures, 3 table
Structural and photoluminescence properties of Gd implanted ZnO single crystals
10.1063/1.3619852Journal of Applied Physics1103-JAPI
Magnetic state of EuN: X-ray magnetic circular dichroism at the Eu M-4,M-5 and L-2,L-3 absorption edges
International audienc
Disorders of compulsivity: a common bias towards learning habits
Why do we repeat choices that we know are bad for us? Decision making is characterized by the parallel engagement of two distinct systems, goal-directed and habitual, thought to arise from two computational learning mechanisms, model-based and model-free. The habitual system is a candidate source of pathological fixedness. Using a decision task that measures the contribution to learning of either mechanism, we show a bias towards model-free (habit) acquisition in disorders involving both natural (binge eating) and artificial (methamphetamine) rewards, and obsessive-compulsive disorder. This favoring of model-free learning may underlie the repetitive behaviors that ultimately dominate in these disorders. Further, we show that the habit formation bias is associated with lower gray matter volumes in caudate and medial orbitofrontal cortex. Our findings suggest that the dysfunction in a common neurocomputational mechanism may underlie diverse disorders involving compulsion