Kinetics in one-dimensional lattice gas and Ising models from time-dependent density functional theory

Time-dependent density functional theory, proposed recently in the context of atomic diffusion and non-equilibrium processes in solids, is tested against Monte Carlo simulation. In order to assess the basic approximation of that theory, the representation of non-equilibrium states by a local equilibrium distribution function, we focus on one-dimensional lattice models, where all equilibrium properties can be worked exactly from the known free energy as a functional of the density. This functional determines the thermodynamic driving forces away from equilibrium. In our studies of the interfacial kinetics of atomic hopping and spin relaxation, we find excellent agreement with simulations, suggesting that the method is useful also for treating more complex problems.Comment: 8 pages, 5 figures, submitted to Phys. Rev.

Dynamics of Viscoplastic Deformation in Amorphous Solids

We propose a dynamical theory of low-temperature shear deformation in amorphous solids. Our analysis is based on molecular-dynamics simulations of a two-dimensional, two-component noncrystalline system. These numerical simulations reveal behavior typical of metallic glasses and other viscoplastic materials, specifically, reversible elastic deformation at small applied stresses, irreversible plastic deformation at larger stresses, a stress threshold above which unbounded plastic flow occurs, and a strong dependence of the state of the system on the history of past deformations. Microscopic observations suggest that a dynamically complete description of the macroscopic state of this deforming body requires specifying, in addition to stress and strain, certain average features of a population of two-state shear transformation zones. Our introduction of these new state variables into the constitutive equations for this system is an extension of earlier models of creep in metallic glasses. In the treatment presented here, we specialize to temperatures far below the glass transition, and postulate that irreversible motions are governed by local entropic fluctuations in the volumes of the transformation zones. In most respects, our theory is in good quantitative agreement with the rich variety of phenomena seen in the simulations.Comment: 16 pages, 9 figure

Charge-density Waves Survive the Pauli Paramagnetic Limit

Measurements of the resistance of single crystals of (Per)$_2$Au(mnt)$_2$ have been made at magnetic fields $B$ of up to 45 T, exceeding the Pauli paramagnetic limit of $B_{\rm P}\approx 37$ T. The continued presence of non-linear charge-density wave electrodynamics at $B \geq 37$ T unambiguously establishes the survival of the charge-density wave state above the Pauli paramagnetic limit, and the likely emergence of an inhomogeneous phase analogous to that anticipated to occur in superconductors.Comment: 4 pages, three figure

Acoustic radiation controls friction: Evidence from a spring-block experiment

Brittle failures of materials and earthquakes generate acoustic/seismic waves which lead to radiation damping feedbacks that should be introduced in the dynamical equations of crack motion. We present direct experimental evidence of the importance of this feedback on the acoustic noise spectrum of well-controlled spring-block sliding experiments performed on a variety of smooth surfaces. The full noise spectrum is quantitatively explained by a simple noisy harmonic oscillator equation with a radiation damping force proportional to the derivative of the acceleration, added to a standard viscous term.Comment: 4 pages including 3 figures. Replaced with version accepted in PR

Teaching old NCATs new tricks: using non-canonical amino acid tagging to study neuronal plasticity

The non-canonical amino acid labeling techniques BONCAT (bioorthogonal non-canonical amino acid tagging) and FUNCAT (fluorescent non-canonical amino acid tagging) enable the specific identification and visualization of newly synthesized proteins. Recently, these techniques have been applied to neuronal systems to elucidate protein synthesis dynamics during plasticity, identify stimulation-induced proteomes and subproteomes and to investigate local protein synthesis in specific subcellular compartments. The next generation of tools and applications, reviewed here, includes the development of new tags, the quantitative identification of newly synthesized proteins, the application of NCAT to whole animals, and the ability to genetically restrict NCAT labeling. These techniques will enable not only improved detection but also allow new scientific questions to be tackled