INFLUENCE OF THE OHMIC POLARIZATION EFFECT ON THIN-LAYER SPECTROELECTROCHEMISTRY

The influence of thin-layer resistance in cyclic voltammetry was studied in detail. Under the experimental conditions, a linear relationship between the peak-peak potential difference and the product of the peak current and the resistance was obtained and

Direct observation of Schottky to Ohmic transition in Al-diamond contacts using real-time photoelectron spectroscopy

Evans D A, Roberts O R, Vearey-Roberts A R, Langstaff D P, Twitchen D J and Schwitters M 2007 Direct observation of Schottky to ohmic transition in Al-diamond contacts using realtime photoelectron spectroscopy Appl. Phys. Lett. 91 132114 doi:10.1063/1.2790779

Heat Dissipation And Energetic Efficiency In Animal Anoxibiosis - Economy Contra Power

This survey on calorimetry and thermodynamics of anoxibiosis applies classical and irreversible thermodynamics to interpret experimental, direct calorimetric results in order to elucidate the sequential activation of various biochemical pathways. First, the concept of direct and indirect calorimetry is expanded to incorporate the thermochemistry of aerobic and anoxic metabolism in living cells and organisms. Calorimetric studies done under normoxia as well as under physiological and environmental anoxia are presented and assessed in terms of ATP turnover rate. Present evidence suggests that unknown sources of energy in freshwater and marine invertebrates under long-term anoxia may be important. During physiological hypoxia, thermodynamically grossly inefficient pathways sustain high metabolic rates for brief periods. On the contrary, under long-term environmental anoxia, low steady-state heat dissipation is linked to the more efficient succinate, propionate, and acetate pathways. In the second part of this paper these relationships are discussed in the context of linear, irreversible thermodynamics. The calorimetric and biochemical trends during aerobic-anoxic transitions are consistent with thermodynamic optimum functions of catabolic pathways. The theory predicts a decrease of rate with an increase of thermodynamic efficiency; therefore maximum rate and maximum efficiency are mutually exclusive. Cellular changes of pH and adenylate phosphorylation potential are recognized as regulatory mechanisms in the energetic switching to propionate production. While enzyme kinetics provides one key for understanding metabolic regulation, our insight remains incomplete without a complementary thermodynamic analysis of kinetic control in energetically coupled pathways.

Power dissipation in nanoscale conductors: classical, semi-classical and quantum dynamics

Modelling Joule heating is a difficult problem because of the need to introduce correct correlations between the motions of the ions and the electrons. In this paper we analyse three different models of current induced heating (a purely classical model, a fully quantum model and a hybrid model in which the electrons are treated quantum mechanically and the atoms are treated classically). We find that all three models allow for both heating and cooling processes in the presence of a current, and furthermore the purely classical and purely quantum models show remarkable agreement in the limit of high biases. However, the hybrid model in the Ehrenfest approximation tends to suppress heating. Analysis of the equations of motion reveals that this is a consequence of two things: the electrons are being treated as a continuous fluid and the atoms cannot undergo quantum fluctuations. A means for correcting this is suggested.

Power dissipation in nanoscale conductors

A previous tight-binding model of power dissipation in a nanoscale conductor under an applied bias is extended to take account of the local atomic topology and the local electronic structure. The method is used to calculate the power dissipated at every atom in model nanoconductor geometries: a nanoscale constriction, a one-dimensional atomic chain between two electrodes with a resonant double barrier, and an irregular nanowire with sharp corners. The local power is compared with the local current density and the local density of states. A simple relation is found between the local power and the current density in quasiballistic geometries. A large enhancement in the power at special atoms is found in cases of resonant and anti-resonant transmission. Such systems may be expected to be particularly unstable against current-induced modifications.

Dissipation and vortex creation in Bose-Einstein condensed gases

We solve the Gross-Pitaevskii equation to study energy transfer from an oscillating

Theory of phonon dissipation in the conduction of stressed Au nanowires

Recent experiments on Au break junctions [Phys. Rev. Lett. 88 (2002) 216803] have characterized the nonlinear conductance of stretched short Au nanowires. They reveal in the voltage range 10-20 meV the signatures of dissipation effects, likely due to phonons in the nanowire, reducing the conductance below the quantized value of 2e(2)/h. We present here a theory, based on a model tight-binding Hamiltonian and on non-equilibrium Green's function techniques, which accounts for the main features of the experiment. The theory helps in revealing details of the experiment which need to be addressed with a more realistic, less idealized, theoretical framework. (C) 2004 Elsevier B.V. All rights reserved.

Dynamical symmetries and crossovers in a three-spin system with collective dissipation

We consider the non-equilibrium dynamics of a simple system consisting of interacting spin-1/2 particles subjected to a collective damping. The model is close to situations that can be engineered in hybrid electro/opto-mechanical settings. Making use of large-deviation theory, we find a Gallavotti-Cohen symmetry in the dynamics of the system as well as evidence for the coexistence of two dynamical phases with different activity levels. We show that additional damping processes smooth out this behavior. Our analytical results are backed up by Monte Carlo simulations that reveal the nature of the trajectories contributing to the different dynamical phases.

Jacinthe ou Les effets de la dissipation

Collection : Bibliothèque chrétienne et morale