Megawatt-Level Repetitively Pulsed Erbium 3-µm Laser with Strong Thermal Lens Compensation

JETP Letters - We report on an increase in the average power of a repetitively pulsed (10 Hz) nanosecond 3-µm laser due to the compensation of a strong thermal lens in the Cr:Er:YSGG laser...     

Formation of Catalytically Active Nanoparticles under Thermolysis of Silver Chloroplatinate(II) and Chloroplatinate(IV)

The thermal behaviour of Ag₂[PtCl₄] and Ag₂[PtCl₆] complex salts in inert and reducing atmospheres has been studied. The thermolysis of compounds in a helium atmosphere is shown to occur in two stages. At the first stage, the complexes decompose in the temperature range of 350–500 °C with the formation of platinum and silver chloride and the release of chlorine gas. At the second stage, silver chloride is sublimated in the temperature range of 700–900 °C, while metallic platinum remains in the solid phase. In contrast to the thermolysis of Ag₂[PtCl₆], the thermal decomposition of Ag₂[PtCl₄] at 350 °C is accompanied by significant heat release, which is associated with disproportionation of the initial salt to Ag₂[PtCl₆], silver chloride, and platinum metal. It is confirmed by DSC measurements, DFT calculations of a suggested reaction, and XRD. The thermolysis of Ag₂[PtCl₄] and Ag₂[PtCl₆] compounds is shown to occur in a hydrogen atmosphere in two poorly separable steps. The compounds are decomposed within 170–350 °C, and silver and platinum are reduced to a metallic state, while a metastable single-phase solid solution of Ag_0.67Pt_0.33 is formed. The catalytic activity of the resulting nanoalloy Ag_0.67Pt_0.33 is studied in the reaction of CO total (TOX) and preferential (PROX) oxidation. Ag_0.67Pt_0.33 enhanced Pt nano-powder activity in CO TOX, but was not selective in CO PROX.     

On variations for mappings with restrictions on dilation in measure

We construct variations for classes of homeomorphisms with generalized derivatives in the case where restrictions in measure of general form are imposed on large values of dilation. We use the method for the construction of variations suggested by Gutlyanskii.     

Thermodynamic Aspects of the Increased Thermal Stability of Silicon by Doping with Transition or Rare-earth Metals

Summary. The main reason of the degradation of silicon monocrystals at heating is a structural transformation connected with a partial transition of the diamond-like structure into the structure of white tin. The reason for this transformation being observed under high pressures is the appearance of stress zones at the boundaries of variously oriented crystal microvolumes due to heat expansion anisotropy. The high stress concentration in the microvolumes provides sufficient pressure for the indicated phase transformation which results in the observed degradation of the electrophysical properties of silicon. The prevention of the structural transformation is considered to be possible by doping of Si by transition or rare-earth metals which increases the interatomic energy and decreases the thermal expansion coefficient. The choice of the doping additions is based on the bonding energy and the charge density calculated for a system of non-polarised ionic radii. The technology to increase the thermal stability of silicon has been patented^#. Patent of Russia, No 2094904, 13/10/1995     

Theoretical study of the conformational states of triosmium clusters with a chiral pinane ligand

A theoretical study of the conformational state of triosmium clusters with a chiral pinane ligand (μ-H)Os₃(CO)₁₀(μ-ONC₁₀H₁₄) has been performed. The potential curves of internal rotation of organic ligands around the N-C bond in cluster complexes in the crystalline state and in various solvents with continual consideration for the parameters of the latter have been determined. The structures of conceivable conformers and isomers are considered; the factors responsible for their formation and stability are examined. The relations between the conformational and crystalline structures of the cluster and the effect of intra-and intermolecular interactions on its structure are revealed.     

A new glimpse on the active site of SARS-CoV-2 3CLpro,coupled with drug repurposing study

Molecular Diversity - Coronavirus disease 2019 (COVID-19) is caused by novel severe acute respiratory syndrome coronavirus (SARS-CoV-2). Its main protease, 3C-like protease (3CLpro), is an...     

Copper-cerium oxide catalysts prepared by the Pechini method for CO removal from hydrogen-containing mixtures

A series of copper-cerium oxide catalysts was prepared by the Pechini method, and their physicochemical and catalytic properties in CO oxidation in hydrogen-containing gas mixtures were studied. The method chosen for catalyst preparation yields finely dispersed copper and cerium oxides in the catalyst.     

Stiffness and conformations of molecular bottle-brushes strongly adsorbed on a flat surface

A theory of the conformational behavior and analysis of the persistence length of molecular bottle-brushes strongly adsorbed on a flat surface in a good solvent is presented. For long enough side chains we have shown that the adsorption of a small fraction of side chains already leads to significant increase of the stiffness and drastic conformational changes of the brush in comparison with the 3D case. For a symmetrical distribution of the adsorbed side chains with respect to the backbone, the equilibrium conformation of the brush is close to a rod-like one due to the very large stiffness of the molecule. Under certain conditions the excluded-volume interactions of the side chains of an asymmetrical brush can lead to its bending or twisting in spiral. The obtained results are in good agreement with computer simulations. Received 13 April 2000 and Received in final form 18 August 2000     

Comblike macromolecules

The theoretical and experimental data on the physical properties of comblike macromolecules are surveyed. Stiffening of comblike macromolecules in solution and on the surface; spontaneous curvature of adsorbed macromolecules resulting from the jump of side chains; rod-globule transitions in adsorbed macromolecules induced by various physical factors; self-organization in the systems of amphiphilic macromolecules; and certain other effects are considered.     

Directions in structure formation of oxyhydrate gels of zirconium and rare earth elements

The formation of oxyhydrate gel systems occurs under conditions that are far from equilibrium. Classical methods of synthesis lead to low reproducibility of the properties of these gels, which is due to principal irreproducibility of colloid systems. When special conditions of the synthesis are used (slow precipitation and prolonged aging at room temperature), directed structure formation takes place: self-similar helical structures are formed, variations of physicochemical characteristics of air-dry samples being insignificant. The directions in structure formation of oxyhydrate gels that lead to self-similar helical structures are discussed. Oligomeric gel moieties, the ratio between which determines the properties of the sample as a whole, have been revealed. The results of computer simulation of gel agglomerates are briefly outlined.