Characteristic features of reduction with i-Bu2AlH of products of ring opening with (?)-α-methylbenzylamine of (3aS,4R,7R,7aS)-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1,3-dione

A special procedure of synthesis was developed for amidoaminals of atypical topology through a reduction with i-Bu₂AlH of primary products of thermodynamical opening of (3aS,4R,7R,7aS)-3a,4,7,7a-tetrahydro-4,7-epoxy-2-benzofuran-1,3-dione at treating with (−)-α-methylbenzylamine. Characteristic spectral criteria are described for assignment of diastereomeric compounds; possible routes of reaction stages are considered.     

Elimination of emission quenching of plasma relativistic microwave generator

The mechanism of the development of the effect of microwave pulse shortening in a plasma relativistic microwave generator with a power of 10⁸ W is determined using numerical simulation. Methods for eliminating the causes of microwave generation quenching are proposed. It is shown that the emission time can be significantly increased.     

Sulfur dioxide Plasma Treatment of the Clay (Laponite) Particles

Low temperature plasma treatment of the inorganic clay (Laponite) using sulfur dioxide (SO₂) as a process gas was carried out in order to graft the functional groups containing sulfur and oxygen (sulfonic acid groups) onto the inert clay surface. Conditions for SO₂ plasma modification were optimized by the measurement of the sulfur content as a function of the plasma power, gas flow rate and treatment time. It was found that the sulfur content increased with the increasing of the plasma power as well as the treatment time. Optical emission spectroscopy was presented in order to control the plasma phase and to characterize the different excitation processes of atomic species in SO₂ plasma under different discharge conditions. X-ray diffraction spectrometry, X-ray photoelectron spectroscopy, FTIR and thermal analysis measurements of grafted Laponite powder completed the characterization.     

CO disrupts the reduced H-cluster of FeFe hydrogenase. A combined DFT and protein film voltammetry study

Carbon monoxide is often described as a competitive inhibitor of FeFe hydrogenases, and it is used for probing H(2) binding to synthetic or in silico models of the active site H-cluster. Yet it does not always behave as a simple inhibitor. Using an original approach which combines accurate electrochemical measurements and theoretical calculations, we elucidate the mechanism by which, under certain conditions, CO binding can cause permanent damage to the H-cluster. Like in the case of oxygen inhibition, the reaction with CO engages the entire H-cluster, rather than only the Fe(2) subsite.     

Variation in the radiation frequency of a plasma relativistic microwave oscillator within its nanosecond pulse

The radiation spectrum of a plasma relativistic microwave oscillator with a pulse power of 50 MW operating in the 10-GHz frequency range is studied experimentally. During a 60-ns-long microwave pulse, the radiation frequency may both remain constant and change by more than 1.5 GHz. The pressure of a gas that ionizes in the microwave field has a significant effect on the radiation frequency and thereby changes the concentration of a pregenerated plasma.     

Periodic boundary value problems for higher‐order fractional differential systems

Approximation of solutions of fractional differential systems (FDS) of higher orders is studied for periodic boundary value problem (PBVP). We propose a numerical‐analytic technique to construct a sequence of functions convergent to the limit function, which is a solution of the given PBVP, if the corresponding determined equation has a root. We also study scalar fractional differential equations (FDE) with asymptotically constant nonlinearities leading to Landesman‐Lazer–type conditions.     

Synthesis of New Hyperbranched Dendrimers with Terminal Cationic Groups Based on Boltorn H20 Polyester Polyol

Terminal polychlorides of hyperbranched polyester polyol Boltorn H20 were synthesized. Subsequent treatment of the resultant polychlorides with absolute pyridine or triphenylphosphine led to the formation of products of varying degrees of functionalization, containing pyridinium or triphenylphosphonium moieties in terminal positions.     

Synthesis of (+)-didesmethylmethylenomycin A methyl ester

A concise and efficient synthesis of the new compound—(+)-didesmethylmethylenomycin A methyl ester from chiral building block 4 has been achieved.     

Photodegradation of Luminescence in SiO2 : Rh B Gels Exposed to YAG : Nd Laser Pulses

Silicate gels doped with organic dyes have been proposed as solid-state tunable lasers. Photobleaching of the dye under laser excitation is an important phenomenon in this application. The optical absorption and luminescence of SiO2 silica gels doped with Rhodamine B exposed to the second harmonic pulses of a YAG : Nd laser have been studied. In addition to the characteristic exponential decay with the number of pulses, overlapping oscillations in the intensity were observed. This behavior is explained in terms of a long lived metastable electronic excited state of the dye molecules.