Effect of Composition of Mg-Al-Oxide Systems on their Catalytic Properties in the Production of 2-Ethyl-1-Hexanol in Vapor-Phase Condensation of 1-Butanol in a Flow System

Theoretical and Experimental Chemistry - It is shown that Mg-Al-oxide catalysts in the vapor-phase condensation of 1-butanol to 2-ethyl-1-hexanol in a flow-type reactor are superior in performance...     

Causality,localizability, and holomorphically convex hulls

A generalization of local commutativity to the fields with an exponential momentum-space growth e ^lp is considered. To study the local properties of such fields we associate to each space-time region a topology ( ) on the test function space. It is shown that under any choice of the topology the fields of exponential growth are localizable only in space-time regions large in comparison withl. This happens because not any domain in the space of several complex variables is a domain of holomorphy. However, by specifying the topology through the use of holomorphically convex domains in ⁴, one can attach certain meaning to local commutativity for arbitrarily close spacelike separated regions of ⁴.     

Highly transparent sol-gel derived ureasilicate monoliths exhibiting long-term optical stability

Optically clear and elastic organic-inorganic hybrid materials were synthesized by hydrolysis and condensation of ureasilicate precursors. Ammonia or citric acid was used as a catalyst for hydrolysis and condensation reactions. The influence of the catalyst nature and the precursor content on the optical, mechanical and thermal properties of samples was investigated. It was shown that it is possible to significantly change the elastic properties of the ureasilicates keeping their good optical transparency in the visible range. The preparation conditions assuring long-term optical and mechanical stability of the samples were determined.     

Depolarization of the electromagnetic field scattered by a three-dimensional large-scale irregularity of the lower ionosphere

This paper develops analytical and numerical methods for the solution of three-dimensional problems of radio wave propagation. We consider a three-dimensional vector problem for the electromagnetic field of a vertical electric dipole in a planar Earth-ionosphere waveguide with a largescale local irregularity of negative characteristics at the anisotropic ionospheric boundary. The field components at the boundary surfaces obey the Leontovich boundary conditions. The problem is reduced to a system of two-dimensional integral equations taking into account the overexcitation and depolarization of the field scattered by the irregularity. Using asymptotic (with respect to the parameter kr≫1, where r is the distance from the source or receiver to the nearest point of the irregularity, k=2π/λ, and λ is the radio wavelength) integration over the direction perpendicular to the ray path, we transform this system to one-dimensional integral equations where integration contours represent the geometric contour of the irregularity. The system is numerically solved in the diagonal approximation, combining direct inversion of the Volterra integral operator and subsequent iterations. The proposed numerical algorithm reduces the computer time required for the solution of this problem and is applicable for studying both small-scale and large-scale irregularities. We obtained novel estimates for the field components that are not excited by the source but result entirely from scattering by the sample three-dimensional ionospheric irregularity.     

Kinetic processes of muonic atom and ion formation in rare gases (spur model)

The possibility of_µF^– formation due to electron attachment to a Xe_µF molecule in_µSR-experiments with a gaseous Ne/Xe mixture is considered. This model explains the results of experiments in Ar and Ne with and without an external electric field.     

On collective two-phonon states in deformed nuclei

The centroid energies of the two-phonon states in doubly even deformed nuclei are calculated within the quasiparticle-phonon nuclear model taking into account the Pauli principle in the two-phonon components of the wave functions. It is shown that the collective two-phonon energies are shifted by 1–2 MeV to higher energies due to the Pauli principle. A strong fragmentation of the two-phonon collective states over many nuclear levels occurs at the excitation energies of 3–4 MeV. It is concluded that the two-phonon states cannot exist in deformed nuclei. The analysis of the available experimental data on the two-phonon states shows that the experimental data do not contradict the results of these calculations.     

Glueballs in the string quark model

We show that the eigenstates of the quantized simplest closed (elliptic) Nambu—Goto string interpreted as glueballs have the quantum numbers I ^G j ^PC=0⁺ j ⁺⁺. The lightest glueballs have the spins j=0,1,2 and the same mass 1500±20 MeV, which corresponds to the f ₀(1500), f ₁(1510), and f ₂(1565) mesons. Excitation of higher Fourier modes leads to the glueball with j=0 and the mass 2200±30 MeV corresponding to the f ₀(2200) meson. The next glueballs have j=0,1,2,3,4 with the masses 2610±20 MeV. The slope of the glueball Regge trajectories is half the slope for the quark—antiquark mesons. The leading (Pomeron) glueball trajectory has the value 1.07±0.03 at zero transferred momentum.