Theoretical Study of the Catalytic Cycle for Ethylene Hydrogenation on a Dipalladium Cluster

A theoretical study of the potential energy surface is carried out for the catalytic cycle of ethylene hydrogenation on a Pd₂cluster using the reaction-path Hamiltonian. The catalytic cycle consists of five related reactions involving ten stationary points. The isomerization of the bridged Pd₂H₂complex into the transcomplex with a maximal barrier of 21.5 kcal/mol rather than the activation of the H–H bond is the most important reaction step. A conclusion is drawn that catalysts based on dipalladium complexes in which the dihydride product readily forms a transform can be active in ethylene hydrogenation.     

Structure and Properties of Biopolymeric Fibrous Materials Based on Polyhydroxybutyrate–Metalloporphyrin Complexes

Russian Journal of General Chemistry - Ultrathin fibrous materials based on natural bacterial polymer polyhydroxybutyrate (PHB) were prepared by the electrospinning method. Using scanning electron...     

Instability of linearly polarized lasing modes of a single-mode VCSEL

Conditions of stability of linearly polarized lasing modes are analyzed within the framework of the spin-flip theory of VCSELs over a wide range of parameters in relation to the linear dichroism and linear birefringence introduced into the system by an optically anisotropic semiconductor crystal.     

Structure of products of H-H and C-H bond activation by Ni atom, Ni2 cluster, and Ni-porphyrin complex of Ni2 cluster

New catalytic systems based on porphyrin complexes of Ni₂ cluster and capable of activating C-H and H-H bonds are proposed. DFT calculations showed that a Ni₂ cluster can coordinate Ni-porphyrin with a considerable gain in energy. The structures of the products of methane and hydrogen activation were discussed.     

Experimental Study of the Polydispersity of Aqueous Colloid of Palygorskite and Suspensions of Escherichia Coli and Pseudomonas Fluorescens by an Electrooptical Method

The results of experimental study on the polydispersity of an aqueous colloid of palygorskite and aqueous suspensions of Escherichia coli (E. coli) and Pseudomonas fluorescens(Ps. fluorescens) are reported. The study is based on the use of a new method; i.e., on the investigation of an electrooptical effect appearing when a weak sinusoidal electric field with sinusoidal amplitude modulation is applied on the system. This method was developed for studying systems in which only slight particle orientation is possible under action of an external electric field. Disperse systems with a high conductivity, including cell suspensions and other biocolloids, colloids containing small particles, as well as solutions of macromolecules and polyelectrolytes, are among such systems. The experimental setup developed in this work is described. The results obtained are compared with data of microscopic measurements and the results of the study of polydispersity in strong fields based on the investigation of the relaxation of electrooptical effect.     

Electro-optical study of the correlation between dimensions and polarizability of particles in colloid systems

The applicability of methods of molecular electro-optics for the study of colloid systems is analyzed. It is shown that the basic formulas of molecular electro-optics can be applied for the calculation of electrical and geometric characteristics of particles of colloid size. The basic integral equations describing electro-optical effects in colloid systems are presented to find distributions of particles over their size and polarizability anisotropy. The accuracy of their solutions is evaluated by mathematical simulation. Studying the dichroism induced by an external electric field in aqueous colloids of anisylidenbenzidine and graphite, the polarizability and size distribution functions are found for particles with an “optical weight.” From the resulting distribution functions, the statistical dependences of the polarizability anisotropy of those particles on their size are found and analyzed.