Procedure for Measuring Low Concentrations of H2 and H2S Above a Water Surface

A simple measuring procedure for low concentrations of H₂ and H₂S (at the level of ppm fractions) above the surface of water by using sensitive gas analyzers is suggested. The procedure is easily accomplished in conditions outside the laboratory (under field conditions).     

Highly Cooperative Tetrametallic Ruthenium-mu-Oxo-mu-Hydroxo Catalyst for the Alcohol Oxidation Reaction

The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy(3))(CO)RuH](4)(mu(4)-O)(mu(3)-OH)(mu(2)-OH)} (1) was synthesized in two steps from the monomeric complex (PCy(3))(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern towards primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C(6)H(4)CH(2)OH (rho = -0.45) and p-X-C(6)H(4)CH(OH)CH(3) (rho = +0.22) (X = OMe, CH(3), H, Cl, CF(3)). Both a sigmoidal curve from the plot of initial rate vs [PhCH(OH)CH(3)] (K(0.5) = 0.34 M; Hill coefficient, n = 4.2+/-0.1) and the phosphine inhibition kinetics revealed the highly cooperative nature of the complex for the oxidation of secondary alcohols.     

Dynamic Compressibility of Carbamide at Low Pressures

The shock adiabats of pressed carbamide samples with a density of 1.29 g/cm³ and carbamide samples with a bulk density of 0.78 g/cm³ were studied at pressures of 1–14 GPa using an electromagnetic method. In the coordinates D and U, the shock adiabat of pressed carbamide is linear and the shock adiabat of carbamide of bulk density at a pressure of 2.4 GPa is represented as two linear segments: D = 2U at 0.6 < U <1.3 km/sec and D = 0.6 + 1.55U at 1.3 <U < 2.8 km/sec. The possibility of a phase transition in carbamide under shock compression is discussed.     

New Concepts Accounting for Variations in the Formation of Multilayer Fiber Composite Materials

Fibre Chemistry - Changes in the mechanical properties of fibrous composite materials can be largely explained by quantitatively evaluating variations in the formation of their macro- and...     

Systematic Analysis of Viscoelastic-Plastic Properties of Marine Polymer Ropes

Fibre Chemistry - Methods of systematic analysis of the viscoelastic-plastic properties of marine polymer ropes are considered, which make it possible to qualitatively assess the operational and...     

Universal algorithms for solving the matrix Bellman equations over semirings

This paper is a survey on universal algorithms for solving the matrix Bellman equations over semirings and especially tropical and idempotent semirings. However, original algorithms are also presented. Some applications and software implementations are discussed.     

Three-dimensionally confined excitons and biexcitons in submonolayer-CdSe/ZnSe superlattices

We report on structural and optical investigations of submonolayer-CdSe/ZnSe superlattices with varying thicknesses of the ZnSe spacer layers. High-resolution electron microscopy images demonstrate the formation of two-dimensional nanoscale CdSe islands for submonolayer-CdSe depositions. The vertical island arrangement is anti-correlated for spacer layer thicknesses exceeding 30Å, while predominantly vertically correlated growth occurs for thinner spacers. The different vertical ordering of the CdSe islands results in two clearly distinguishable lines in photoluminescence and optical reflectance spectra, which are attributed to excitons localized in quantum dots (QDs) formed by vertically coupled and uncoupled (Cd,Zn)Se islands, respectively. δ-like emission of single QDs is demonstrated and the different carrier localization in uncoupled and coupled QDs is reflected in the polarization of the edge emission. Stimulated emission and resonant waveguiding effects are observed for both states. At the highest excitation densities, we observe saturation of the stimulated emission in edge geometry attributed to saturation of localized states.