Characteristics of fourier phase holograms recorded on photopolymers

The results of the investigation of recording Fourier phase holograms on a self-developing photopolymer photosensitive in the range λ=400–515 nm are presented. It has been found that, due to the transient energy transfer between the beams, noise gratings are recorded, and a corresponding sharp reduction in the signal-to-noise ratio occurs, while the diffraction efficiency of the hologram as a whole remains relatively high (above 50%). It has been found that the noise-grating recording can be substantially suppressed by increasing the intensity of the reference beam relative to the intensity of the object beam. In this way, the signal-to-noise ratio has been considerably improved for Fourier holograms of binary phase masks: at a reference to object beam intensity ratio R=26, Fourier phase holograms are recorded with a diffraction efficiency η=15% and signal-to-noise ratio N=20 dB.     

Impurity–defect emission from undoped Cd<Subscript>1–<Emphasis Type="Italic">x</Emphasis> </Subscript>Zn<Subscript> <Emphasis Type="Italic">x</Emphasis> </Subscript>Te single crystals near the fundamental absorption edge

Shallow impurity–defect states in undoped Cd_1–xZn_xTe (x ～ 3–6%) single crystals have been studied using low-temperature photoluminescence measurements. It has been found that the effect exerted by zinc is mainly reduced to a rigid shift of all the specific features associated with the exciton radiation, which made it possible, with a high (～0.3 meV) accuracy, to measure the band gap and the zinc concentration in solid solutions. Hydrogen-like donors with the ground-state energy of ～14 meV and four types of acceptors with average activation energies of 59.3 ± 0.6 meV, 69.6 ± 1.5 meV, 155.8 ± 2.0 meV, and 52.3 ± 0.6 meV have been identified in all the crystals studied. Based on a comparison with the results of the analysis of the impurity background and the data available in the literature on impurity–defect emission in undoped CdTe, the first three acceptors can be assigned to the substitutional impurities Na_Cd, P_Te, and Cu_Cd, respectively. The most shallow acceptor (52.3 ± 0.6 meV) is a complex defect in which there is a nonstandard excited level separated by only 7 meV from the ground level. This level is formed apparently due to the removal of degeneracy, which is characteristic of T_D acceptors, by the low-symmetry potential of the complex defect.     

Using a plane wave approximation in simulation of radiation distribution in an X-ray Talbot interferometer

This study is devoted to the analysis of the plane-wave approximation applicability to X-ray radiation incident on an object. Based on simple calculations, it is shown that an X-ray tube focal spot 0.4 × 0.8 mm in size at distances of ~1 m can be considered as a point source; however, the plane-wave approximation for such X-ray radiation with energy E = 22keV is valid for radiation source–object distances much longer than 10 m.     

High-Selective Catalyst Based on Intermetallic Rh1In1 Particles for Nitrobenzene Hydrogenation

Kinetics and Catalysis - The catalytic performance of a bimetallic RhIn/SiO2 catalyst was studied in the liquid-phase hydrogenation of nitrobenzene. The formation of intermetallic Rh1In1...     

Selective Synthesis of 2,5‐Diformylfuran by Sustainable 4‐acetamido‐TEMPO/Halogen‐Mediated Electrooxidation of 5‐Hydroxymethylfurfural

A new method was developed for the selective gram‐scale synthesis of 2,5‐diformylfuran (DFF), which is an important chemical with a high application potential, via oxidation of biomass‐derived 5‐hydroxylmethylfurfural (HMF) catalyzed by 4‐acetylamino‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl (4‐AcNH‐TEMPO) in a two‐phase system consisting of a methylene chloride and aqueous solution containing sodium hydrogen carbonate and potassium iodide. The key feature of this method is the generation of the I₂ (co‐)oxidant by anodic oxidation of iodide anions during pulse electrolysis. In addition, the electrolyte can be successfully recycled five times while maintaining a 62–65 % yield of DFF. This novel method provides a sustainable pathway for waste‐free production of DFF without the use of metal catalysts and expensive oxidants. An advantage of electrooxidation is utilized in the preparation of demanding chemical.     

The Polymorphism of 5-n-Hexyl-2-[4-n-pentyloxyphenyl]-pyridine

The phase transitions of 5-n-hexyl-2-[4-n-pentyloxyphenyl]-pyridine were determined by miroscopic and calorimetric investigations. The classification of the smectic modifications was done by investigation of the miscibility relations. Besides the nematic phase smectic phases C, F, G and H were identified.     

Binding of MRI contrast agents to albumin: a high-field EPR study

High-field electron paramagnetic resonance (EPR) experiments to monitor binding of lipophilic Gd(III) complexes to human serum albumin (HSA) are described. It was observed that magnetic interactions between the nitroxide moiety ofn-doxyl-stearic acids bound to HSA and Gd(III) complexes resulted in broadening of nitroxide continuous-wave EPR spectra. The broadening effect can be well described by a one-parameter model of additional Lorentzian broadening At 95 GHz, continuous-wave EPR spectra from Gd(III) complexes are fully resolved from the nitroxide signal allowing for simultaneous and independent line shape analysis. Analysis of the line width broadening effects for spectra from a series ofn-doxyl-stearic acids bound to HSA indicated a progressive decrease of spin label-Gd(III) magnetic interactions along the fatty acid (FA) binding channel, consistent with binding of Gd-DOTAP complex in the vicinity of the main FA binding site. The substantial difference in spin label-metal interactions along the FA binding channel for lipophilic Gd(III) complexes with different chelates is indicative of binding to different sites. We also report measurements of dissociation constant for noncovalent binding of Gd(III) complexes to HSA on the basis of analyses of 95 GHz Gd(III) EPR line shapes.     

Sorption of Metal Ions by Chitosan Copolymers with Vinyl Monomers

Russian Journal of Applied Chemistry - Chitosan copolymers with vinyl monomers: 4-N-vinylpyridine, acrylamide, and acrylic acid, were synthesized and these sorption properties were investigated....     

Base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over Pt/C catalysts synthesized by pulse alternating current technique

The Pt/C catalysts with various Pt content (5-30 wt%) synthesized via electrochemical pulse alternating current technique have been evaluated for the base-free aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. The higher Pt content in the catalyst (30 wt%) provides the product yield up to 65% upon performing the process in concentrated (～0.1 M) aqueous solutions of the substrate.     

Following screened perturbations in an elastic medium with a thin layer

The result of the calculation of the field of a longitudinal wave which has passed through an elastic layer is studied and the character of the propagation of different phases of this wave is determined.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im V. A. Steklova AN SSSR, Vol. 165, pp. 159–165, 1987.