Optical characteristics of porous silicon structures

Morphology, composition, and optical properties of porous silicon on single-crystal-silicon substrates and p-n junctions are studied. Substrate orientation, type of conduction, and composition of etching agent are varied to obtain nano-, meso-, and microporous silicon and multilayer porous structures. A correlation of the photoluminescence intensity and intensity of the IR absorption band peaking at 616 cm^?1 is related to the presence of Si-Si bonds.     

Crystal structure and composition of hydroxyapatite biocomposites prepared at excess of calcium ions

Formation of composites by calcium phosphates with chondroitin sulfate and gelatin obtained at excess content of calcium ion in solution is studied by the methods of X-ray phase analysis, IR spectroscopy and electron microscopy. Inclusion to the crystals of hydroxyapatite as the main phase and the absence of chemical interaction of biopolymers with calcium phosphate is proved and some features of the effect of reagents addition order to the studied system calcium-ammonium hydrogen phosphate-organic component are elucidated.     

Nonadditive Linearity in the Chemostimulating Effect of Activator Oxides + Dlient Compositions on GaAs Thermal Oxidation

The chemostimulation efficiency of the activators Sb₂O₃ and Bi₂O₃ in compositions with a diluent (Al₂O₃) is a linear function of activator percentage over a wide range of temperatures. This function is not, however, additive to the thicknesses achieved in the presence of individual components. The percentage of the activator elements in the resulting oxide layers coincides with that in the initial compositions in the linear region and differs from it in the nonadditivity region. Thermal analysis in combination with X-ray powder diffraction showed that Al₂O₃ alters the temperature range and character of the intrinsic transformations of activator oxides.     

Percolation effects with copper electrodeposition in ion-exchange material

The effect of preliminary doping of sulfo cation-exchange material KU-23 15/100S with a chemically deposited metal (Ag, Cu) on the rate of copper ion electroreduction is investigated. It is shown that the threshold dependence of the reaction current of copper electroreduction on the amount of doped metal is due to the formation of a single percolation cluster in an ion-exchange grain and, as a result, to the appearance of electron conductivity. It is established that preliminary doping changes the nucleation mechanism from a gradual to an instantaneous one. Results from a local X-ray spectral microanalysis provide the basis for concluding that copper electrodeposition is uniform throughout the volume of an ion-exchange grain. The average size of the copper particles formed is 100 nm.     

1,3,4-Oxadiazole-containing hybrids as potential anticancer agents: Recent developments,mechanism of action and structure-activity relationships

Chemotherapy is an important therapeutic approach for the treatment of cancer. Currently, many anticancer drugs are available in the market that plays an important role in cancer treatment, but concerns such as, drug resistance and side effects create an urgent need for the development of new anti-tumor drugs with high potency and less side effects. Heterocycles are of great interest due to their fascinating anticancer activity. Among them, 1,3,4-oxadiazoles showed attracting anti-tumor activity and its derivatives are under clinical trials for the treatment of cancer. Hybridization of 1,3,4-oxadiazole moiety with other heterocyclic pharmacophoresis a promising approach to overcome various disadvantages of current anticancer drugs such as drug resistance, toxicity, and other side effects. Thus, 1,3,4-oxadiazole-heterocycle hybrids occupy a significant position in the discovery of anti-tumor drugs. Among the reported oxadiazole-based hybrids reviewed here, compounds 45i, 59j, and 62x showed the highest anticancer activity with IC₅₀ values in the nanomolar range. This review summarizes the recent developments in the anticancer potential, structure–activity relationships, and mechanisms of actions of 1,3,4-oxadiazole-heterocycle hybrids.     

Superconducting synchrotron project for hadron therapy

The project of a superconducting medical synchrotron for carbon therapy in the ion energy range from 140 to 400 MeV/n is discussed in this paper. This project is aimed at developing and building a medical synchrotron on the basis of superconducting technologies at JINR under the construction of the Nuclotron accelerator complex. A linear accelerator with alternating phase focusing is proposed for injecting carbon ion into the synchrotron, while it is planned to use a superconducting gantry weighing about 150 t for delivering radiation treatment to patients from all directions.     

Role of solid- and gas-phase interactions in the coaction of the oxides in MnO2 + PbO and MnO2 + V2O5 compositions activating the thermal oxidation of GaAs

Spatial separation of the oxides in MnO₂ + PbO and MnO₂ + V₂O₅ binary compositions activating the thermal oxidation of GaAs has made it possible to locate the interactions between these oxides that are responsible for the nonlinear effects observed in their coaction. The solid-phase interactions enhance the chemostimulating activities of both oxides (a positive nonlinear effect takes place). The gas-phase interactions cause a marked negative deviation from the additive chemical stimulation effect.     

GaAs thermal oxidation with participation of spatially separated activator oxides (MnO + PbO and MnO + V2O5)

Spatial separation of activator oxides in MnO₂ + PbO and MnO₂ + V₂O₅ binary compositions helps to locate the interactions between the oxides that lead to nonlinear joint effects of the compositions on GaAs thermal oxidation. The mutual enhancement of the chemostimulating activity (a positive nonlinear effect) was discovered in the solid phase, whereas vapor-phase processes led to a considerable negative nonadditivity of the joint chemostimulating effect.