Non–Isothermal Shear Band Localization in Crystal Plasticity

We analyze the formation of shear bands in plastically deforming single crystals under non-isothermal quasi-static loading conditions. A key feature of the present work is to motivate the constitutive coupled thermomechanical equations for the slip resistance and the slip evolution by micromechanical investigations of defects in crystals. Here, we put particular emphasis on comparative investigations of hardening–softening effects of crystals under non-isothermal conditions, including a quantification of the latent energy storage. Furthermore, we analyze a numerical solution algorithm for the coupled thermomechanical problem and we test the performance on a typical benchmark example of finite-strain single-crystal thermoplasticity: the localization of deformation into a shear band for the case of a rectangular strip. Experimental evidence for this problem is well documented. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Turbulence and line shape formation in plasmas

We investigate the role of turbulent fluctuations on line shape formation in optically thin plasmas. A general expression, valid if the turbulent scales are much larger than the atomic scales, is obtained for the profile measured using a passive spectroscopy set up. Well-known limiting cases for Doppler and Stark broadening are identified. Then, the role of temperature fluctuations on Doppler line shapes, and the effect of density fluctuations on Stark broadened lines in the quasi-static regime are investigated.     

On the modeling of thermo-electro-magneto-mechanical solids at finite strains

A short overview of the mechanics of electromagnetic continua at finite strains is provided in this paper. In this framework objective thermodynamically-consistent constitutive relations are formulated for materials that exhibit thermo-electro-magnetomechanical coupling. In particular a model for an isotropic hyperelastic magnetic solid is considered, which finds application for magnetorheological elastomers (MRE). (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Atomistic simulation of the interaction of slow protons with an iron surface

Summary We have studied the dynamical behaviour of low-energy protons (1.0 eV≤E _in≤50 eV) interacting with a Fe {100} surface atT=300 K, by means of molecular-dynamics simulations. The inelastic energy losses have been taken into account by means of a friction term proportional to the projectile velocity and depending on the instantaneous local electronic density experienced by the projectile. For a given incident energy and irradiation geometry, we have estimated the particle and energy reflection coefficients and obtained a detailed evaluation of the different contributions (elastic and inelastic) to the energy loss of the reflected particles.     

Fluorescence lifetime distribution of folded and unfolded proteins

Time-resolved fluorescence of single tryptophan proteins have demonstrated the complexity of protein dynamic and protein structure. In particular, for some single tryptophan proteins, their fluorescence decay is best described by a distribution of fluorescence lifetimes rather than one or two lifetimes. Such results have provided further confirmation that the protein system is one which fluctuates between a hierarchy of many conformational substates. With this scenario as a theoretical framework, the correlations between protein dynamic and structure are investigated by studying the time-resolved fluorescence and anisotropy decay of holo and apo human superoxide dismutase (HSOD) at different denaturant concentrations. As a function of guanidine hydrochloride (GdHCl), the width of the fluorescence lifetime distribution of HSOD displays a maximum which is not coincident with the fully denatured form of HSOD at 6.5M GdHCl. Furthermore, the width of the fluorescence lifetime distribution for the fully denatured forms of holo and apo HSOD is greater than that of the native forms.     

Particle dynamics calculations of wall stresses and slip velocities for couette flow of smooth inelastic spheres

The objective of this work is to characterize the effects of boundary geometry on the flow of dry granular materials composed of smooth, inelastic spheres between parallel, bumpy walls in the absence of gravity. Particle dynamic simulations are done in which wall stresses and slip velocities are computed over a wide range of parameters, including shear gap height, geometry of the wall particles, wall to free particle diameter ratio, and normal restitution coefficient. Calculated wall stresses and slip velocities are found to be highly sensitive to boundary roughness, which is characterized in terms of the mean spacing value for the wall particles. Most noticeable is a pronounced stress drop for dense flows with an associated large slip velocity in a system having a narrow shear gap height.