3a,6a-Diaza-1,4-Diphosphapentalene Complexes with Lewis Acids InI3 and SbCl3

Russian Journal of Coordination Chemistry - 3a,6a-Diaza-1,4-diphosphapentalene (DDP) with indium triiodide forms the [In(DDP)I3] complex (I) with the ratio In : DDP = 1 : 1. The DDP ligand reacts...     

Synthetic realization approach to fuzzy global optimization via gamma algorithm

A new approach is proposed for global optimization problems with fuzzy cost functions and fuzzy box and equality constraints. It allows one to avoid complex operations with fuzzy sets and the use of various subjective indices of choice. To resolve the contradiction between economically better solutions with low possibility of realization and a little poorer solution with higher possibility of realization, the synthetic realization is defined as certain fixed -level cut for all membership functions. Consideration of such realizations guarantees a level of credibility not less than given (0, 1] for all globally optimal solutions. Then, so defined -cuts are rectified to cut off realizations with possibility less than and to retain higher possibility realizations which are assigned credibility μ = 1 for the whole interval of possible realizations. This construction results in a set-valued band of credibility not less than for a given fuzzy cost function f̃(x) which band has crisp Lipschitz continuous lower- and upper-value functions f_*(x), f*(x) such that f_*(x) ≤ f̃(x) ≤ f*(x) for all x X̃ Rⁿ. Then, the gamma algorithm is applied to obtain the interval global optimal solution f̄₀(x) = [f⁰_*(x), f*₀(x)]. To further simplify the computations, the fuzziness in the feasible set X̃ is transferred to the function value space transforming X̃ into the crisp unit cube in Rⁿ₊ common for all fuzzy optimization problems in Rⁿ with box and equality constraints.     

Charge transfer between a superconductor and a hopping insulator

We develop a theory of the low-temperature charge transfer between a superconductor and a hopping insulator. We show that the charge transfer is governed by the coherent two-electron-Cooper pair conversion process time-reversal reflection, where electrons tunnel into a superconductor from the localized states in the hopping insulator located near the interface, and calculate the corresponding interface resistance. A specific feature of this problem is the interplay between the time-reversal reflection at the interface and transport through the percolation cluster. To allow for this interplay, we have generalized the connectivity criterion of the percolation theory to include surface effects. We show that the time-reversal interface resistance is accessible experimentally, and that in mesoscopic structures it can exceed the bulk hopping resistance.     

Mechanical Cooper pair transportation as a source of long-distance superconducting phase coherence

Transportation of Cooper pairs by a movable single Cooper-pair box placed between two remote superconductors is shown to establish coherent coupling between them. This coupling is due to entanglement of the movable box with the leads and is manifested in the suppression of quantum fluctuations of the relative phase of the order parameters of the leads. It can be probed by attaching a high resistance Josephson junction between the leads and measuring the current through this junction. The current is suppressed with increasing temperature.     

Statistics of deep energy states in Coulomb glasses

We study the statistics of local energy minima in the configuration space and the energy relaxation due to activated hopping in a system of interacting electrons in a random environment. The distribution of the local minima is exponential, which is in agreement with extreme value statistics considerations. The relaxation of the system energy shows logarithmic time dependence reflecting the ultrametric structure of the system.     

Reaction of 3a,6a-Diaza-1,4-diphosphapentalene with Substituted Acetylenes

Russian Journal of General Chemistry - The reaction of 3a,6a-diaza-1,4-diphosphapentalene with 1-bromo-2-phenylacetylene has led to the formation of 1,1-bis(phenylethynyl)- and...     

Silver nanoparticles electrooxidation: theory and experiment

This article presents the findings of microscopic and electrochemical studies of electrooxidation of silver nanoparticles of varying sizes in comparison with “bulk” silver. Silver particles were immobilized on the surface of indifferent carbon-containing screen-printed electrodes. Vacuum-deposited silver represented the “bulk” electrode. The calculations and experimental studies demonstrated that the transition from macro- to nanostructural electrodes is followed by a shift of the maximum current potential of metal oxidation into the area with more negative potentials. A positive correlation between experimental and calculated data confirms once again a relevant application of the earlier proposed mathematical model and the possible use of the shift of the maximum current potential of electrooxidation to describe the electrochemical activity and surface energy properties of metal nanoparticles.     

Molecular transport junctions: current from electronic excitations in the leads

Using a model comprising a two-level bridge connecting free electron reservoirs we show that coupling of a molecular bridge to electron-hole excitations in the leads can markedly effect the source-drain current through a molecular junction. In some cases, e.g., molecules that exhibit strong charge transfer transitions, the contribution from electron-hole excitations can exceed the Landauer elastic current and dominate the observed conduction.