A first-principles pseudopotential study of neutral self-interstitial defects in silicon is reported, together with calculations for Pandey’s concerted exchange mechanism for selfdiffusion. The energies and structures of the fully relaxed hexagonal, tetrahedral, split-〈110〉, ‘caged’ (Clark S J and Ackland G J 1997 Phys. Rev. B 56 47), split-〈100〉, and bond-centred interstitials are calculated u...

The study of the diffusive behavior of glioma tumor growth is an active field of biomedical research with considerable therapeutic implications. An important aspect of the corresponding computational problem is the mathematical handling of boundary conditions. This paper aims at providing an explicit and thorough numerical formulation of the adiabatic Neumann boundary conditions imposed by the ...

We consider transport of a passive scalar by an isotropic turbulent velocity field in the presence of a mean scalar gradient. The velocity–scalar cospectrum measures the distribution of the mean scalar flux across scales. An inequality is shown to bound the magnitude of the cospectrum in terms of the shell-summed energy and scalar spectra. At high Schmidt number, this bound limits the possible ...

P. H. Diamond University of California, San Diego, La Jolla, CA 92093, USA Abstract This paper reports on a recent advance in developing physical understanding and a firstprinciples-based model for predicting intrinsic rotation profiles in magnetic fusion experiments. It is shown for the first time that turbulent fluctuation-driven residual stress (a non-diffusive component of momentum flux) al...

In the Ocean, thermohaline intrusions and interleaving layers occur within water mass fronts with horizontal temperature salinity gradients, which provide an important mixing mechanism. Here we report a new type of intrusion is driven by gradients in fluid at adjacent depths due to different double diffusive rates vertical direction. Once established, share similar behaviors as those found grad...

In their role as second messengers, cyclic nucleotides such as cAMP have a variety of intracellular effects. These complex tasks demand a highly organized orchestration of spatially and temporally confined cAMP action which should be best achieved by compartmentalization of the latter. A great body of evidence suggests that cAMP compartments may be established and maintained by cAMP degrading e...

A rhombic planform nonlinear cross-diffusive instability analysis is applied to a particular interaction-diffusion plant-ground water model system in an arid flat environment. This model contains a plant root suction effect as a cross-diffusion term in the ground water equation. In addition a threshold-dependent paradigm that differs from the usually employed implicit zero-threshold methodology...