Specific features of the structure and dielectric relaxation of PbWO<Subscript>4</Subscript> in the temperature range 20≤<Emphasis Type="Italic">T</Emphasis>≤550°C

An anomaly of the relaxor type is revealed in the permittivity of the PbWO₄ compound at a temperature of 370°C. This anomaly is associated with the local random displacements of lead and tungsten atoms in the nearest environment of oxygen atoms.     

The heat of wetting of aluminum hydroxyoxide obtained by the thermal activation of hydrargillite

Changes in the volume and surface properties of thermally activated hydrargillite, so-called centrifugal thermal activation (CTA) product (empirical formula Al₂O₃ · 0.85H₂O), during its calcining in air with gradually increasing temperature from 90 to 1100°C were studied. At each stage of calcining, weight loss, phase composition, texture characteristics, and the heat of wetting with water at 25°C were determined. Measurements of the heat of wetting showed that the energy and, therefore, chemical state of the surface changed during thermal treatment. The data obtained were used to calculate the heats of adsorption q _ads of water vapor by CTA samples with different water contents; the range of q _ads variations was 50–250 kJ/mol. The values obtained are compared with literature data.     

A controlled clinical study of product PINOROX® (Pinus roxburghii bark extract) (PINOROX®) as dietary supplement for enhanced physical performance

Pinorox® is a standardized composition obtained from pine bark extract of Pinus roxburghii, rich source of natural polyphenols - Oligomeric Proanthocyanidins (OPCs) compounds that act as an antioxidant. Pinorox® has been expected to serve as potential natural supplement consumed to enhance the physical endurance in normal healthy or a sport person. Hence, double-blind, randomized, placebo-controlled study was conducted for time period of 90 days to validate the effect of Pinorox® over physical and athletic performances in normal healthy as well as sports subjects. 50 eligible subjects were selected through screening and distributed into placebo and Pinorox® groups. The subjects utilized in the present study i.e., healthy individual and athletes received one of either 200 mg of Pinorox® or experimental control (placebo) for 90 days. Each subject was evaluated for increase in physical or athletic performances by observing changes from baseline in rate of oxygen consumption VO₂ max (endurance) compared to placebo at baseline, assessment of anaerobic power and rate of fatigue by using Wingate test at baseline, changes in assessment values using 1-RM test and muscle grip strength assessment using handheld dynamometer at baseline and during the interval of 90 days. The observations discussed in the present study shows that people consuming Pinorox® displayed significantly advanced performances during exercising or performing given sports activities. Improvement in the VO₂ max values, anaerobic power, rate of fatigue, muscular performance and muscle grip strength was observed in test results and the study did not report any adverse effect. Overall, the study demonstrates that Pinorox® is a safe, fast acting and effective natural dietary or sport supplement for enhancing physical and athletic performances.     

Investigation of the optical characteristics of composite materials based on cadmium sulfide nanoparticles stabilized in a high-pressure polyethylene matrix

Composite materials based on cadmium sulfide nanoparticles in an inert dielectric matrix of high-pressure (low-density) polyethylene are experimentally studied. It is shown how the size and weight concentration of nanoparticles in the bulk of the stabilizing matrix affect the nanocomposite absorption. The experimental results are interpreted based on the two-flux Kubelka-Munk model.     

Electrical transport and persistent photoconductivity in quantum dot layers in InAs/GaAs structures

The conductivity of quantum dot layers is studied in InAs/GaAs structures in the temperature range from 300 to 0.05 K in the dark and using two types of illumination in magnetic fields up to 6 T. Depending on the initial concentration of current carriers, the conductivity of the structures varied from metallic (the Shubnikov-de Haas effect was observed) to hopping conductivity. At low temperatures, the temperature dependence of the resistance changed from the Mott dependence to the dependence described by the Shklovskii-Efros law for hopping conductivity in the presence of the Coulomb gap in the density of states. The conductivity of samples was studied upon their illumination at λ = 791 nm and λ > 1120 nm. All the samples exhibited a positive persistent photoconductivity at T < 250 K. The structures were also studied using photoluminescence and an atomic force microscope.     

Volumetric and Acoustic Properties of Phenylboronic Acid in Water at Selected Temperatures

Journal of Solution Chemistry - Measurements of density and speed of sound are reported for phenylboronic acid–water solutions for molalities ranging from 0.0098 to...     

Studies of benzoxazines 16*. Synthesis and reactivity of 2,4-substituted 4H-3,1-benzoxazines

A novel method has been developed for preparation of substituted 4H-3,1-benzoxazines via formation of tetrafluoroborates. The substitution of halogen in 2-(α-haloalkyl)-4,4-diphenyl-4H-3,1-benzoxazines by NH and SH nucleophiles was performed. The effect of electrophilic substitution in the annelated aromatic ring in a series of 2,4-substituted 4H-3,1-benzoxazines has been studied.     

Structure of phase-inversion membranes from small-angle neutron scattering data

The structure of gradient-porous (asymmetric) membranes based on polyamide imide at different conditions of their formation has been investigated using small-angle neutron scattering. It has been shown that the membranes consist of rigid porous networks with well-defined interfaces between the polymer and the pores. It has been found that there are differences in the packings of structural elements of porous membranes-spherical pores with radii from 4 to 100 nm—depending on the membrane preformation time, drying regime, and the presence of fullerene C₆₀ for modifying the mechanical and selective properties of membranes. The membranes also contain larger pores of micrometer sizes. Differences in the rates of saturation of membranes with water and their limiting swelling ratios are found, which can be explained by the structure of the dense layers of membranes (skin layer) and their different hydrophilities (depending on the fullerene content).     

Electrical conductivity of Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Co<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O ferromagnetic films at low temperatures

The results of experiments on electrical conductivity and magnetic properties of thin cobalt-doped zinc oxide films are reported. The results indicate the predominance of the hoping conduction mechanism at low temperatures and the band mechanism at high temperatures. An increase in the cobalt concentration from 1.5 to 6.3 at % leads to the reduction of the electrical conductivity of the films. The contribution of hopping conduction to the conductivity increases due to a decrease in the crystallinity of the films and localization of a part of electron states upon an increase in the cobalt concentration. For cobalt-containing films, a hysteresis of the magnetic moment as a function of the magnetic field is observed. The dependence of the shape of the magnetization curves on the cobalt concentration is irregular. The paramagnetic contribution to the magnetic susceptibility increases with the cobalt concentration.