Mesostructure of xerogels of hydrated zirconium dioxide

The fractal properties of xerogels of hydrated zirconium dioxide ZrO₂, which are synthesized by precipitation from a zirconyl nitrate solution at various pH values, are studied. Small-angle neutron scattering data and low-temperature nitrogen adsorption data indicate the strong effect of the acidity of the medium on the fractal dimension of xerogels and the size of constituent monomer particles. It is shown that this effect is also characteristic of xerogels of hydrated hafnium dioxide HfO₂, which is a chemical analogue of hydrated zirconium dioxide.     

Tokamak DEMO-FNS: Concept of magnet system and vacuum chamber

The level of knowledge accumulated to date in the physics and technologies of controlled thermonuclear fusion (CTF) makes it possible to begin designing fusion—fission hybrid systems that would involve a fusion neutron source (FNS) and which would admit employment for the production of fissile materials and for the transmutation of spent nuclear fuel. Modern Russian strategies for CTF development plan the construction to 2023 of tokamak-based demonstration hybrid FNS for implementing steady-state plasma burning, testing hybrid blankets, and evolving nuclear technologies. Work on designing the DEMO-FNS facility is still in its infancy. The Efremov Institute began designing its magnet system and vacuum chamber, while the Kurchatov Institute developed plasma-physics design aspects and determined basic parameters of the facility. The major radius of the plasma in the DEMO-FNS facility is R = 2.75 m, while its minor radius is a = 1 m; the plasma elongation is k ₉₅ = 2. The fusion power is P _FUS = 40 MW. The toroidal magnetic field on the plasma-filament axis is B _t0 = 5 T. The plasma current is I _p = 5 MA. The application of superconductors in the magnet system permits drastically reducing the power consumed by its magnets but requires arranging a thick radiation shield between the plasma and magnet system. The central solenoid, toroidal-field coils, and poloidal-field coils are manufactured from, respectively, Nb₃Sn, NbTi and Nb₃Sn, and NbTi. The vacuum chamber is a double-wall vessel. The space between the walls manufactured from 316L austenitic steel is filled with an iron—water radiation shield (70% of stainless steel and 30% of water).     

Thermophysical properties of aluminum nitride ceramic

The paper reports an experimental low-temperature study of the temperature-dependent behavior of the lattice constants, heat capacity, and thermal conductivity of the AlN ceramic. The results obtained are compared with the data available for the high-temperature region. The thermal expansion coefficient is found to be negative. Fiz. Tverd. Tela (St. Petersburg) 39, 93–96 (January 1997)     

Strain mapping analysis of textile composites

The focus of the work is meso-scale analysis (scale level of the fabric unit cell) of textile composite deformation and failure. The surface strain measurement is used for: (1) experimental investigation, which includes study of strain distribution at various stages of deformation, plasticity detection, damage initiation; (2) numerical validation of the correspondent finite element (FE) models. Two examples are considered: carbon-epoxy triaxial-braided and glass polypropylene-woven composite. The surface strain measurement (by digital image correlation technique) accompanies the tensile tests, aiming at: (1) elastic anisotropic constants characterisation, (2) study of non-linear material behaviour (for the thermoplastic composite), (3) control of homogeneity of the macro-strain distribution, and (4) analysis of damage initiation in brittle composites. Validation of meso-FE models by strain measurements encounters difficulties arising from (1) resolution of the strain measurements, (2) irregularities of the initial structure such as random layer nesting, ply interaction, and deviation of yarns from their theoretical position, which affects the measured strain fields. The paper discusses these difficulties and demonstrates a qualitative agreement with the FE analysis of idealised composite configurations.     

Combined laser and photodynamic treatment in extensive purulent wounds

Recently, photodynamic therapy (PDT) has been used for the treatment of festering wounds and trophic ulcers. An important advantage of PDT is its ability to affect bacterial cultures that are resistant to antibiotics. However the use of PDT alone does not usually guarantee a stable antiseptic effect and cannot prevent an external infection of wounds and burns. In this work attention is focused on the healing of the extensive soft tissues wounds with combined laser therapy (LT) and PDT treatment. At the first stage of this process festering tissues (for example spacious purulent wounds with area more than 100 cm²) were illuminated with high-energy laser beam (with power 20 W) in continues routine. The second stage involves “softer” PDT affect, which along with the completion stages of destruction pathological cells, stimulating the process of wound granulation and epithelization. Also, according to our previous results, photosensitizer (photoditazin) is introduced inside the wound with different amphiphilic polymers for increasing the PDT efficacy.     

Low-energy thermal excitations in the V-O system

The thermal excitations of the atoms of the V-O solid solution have been investigated by the slow-neutron scattering method for low-energy transfers. The features of the low-frequency excitations of a light impurity in the metal lattice for energy transfers ? ≈ 1.3 and 2.4 meV have been revealed. It is assumed that the observed low-energy excitations appear in V-O due to strong local distortions around an impurity atom, which are responsible for the formation of the effective potential of a complex shape with the almost flat bottom. Analysis of the interaction of oxygen with the nearest matrix atoms shows that the low-energy excitations of oxygen atoms can be attributed to the splitting of the ground state in the complex potential. The level scheme of the split state can be obtained in the representation of decelerated circular quantum rotation about the axis passing through the two nearest metal atoms or the motion in a two-dimensional potential well. The results indicate that rotational low-energy excitations can exist in (metal-interstitial impurity) solid solutions.     

Radio-frequency ion source generating beams with an increased proton content

The results of experiments with an rf ion source generating a beam with an improved mass composition are reported. The proton content in the beam is increased by raising the rf power density in the discharge under the antenna and installing a magnetic filter near the plasma grid. Additional steps are taken to prevent the earlier observed degradation of the beam composition because of aluminum reduction on the inner surface of the ceramic discharge chamber and water release. Specifically, the chamber is lined with pyrolytic boron nitride sheets.     

How to measure the pomeron phasein diffractive dipion photoproduction

The study of charge asymmetry of pions in the high-energy process ep → eπ⁺π^-p (γp → π⁺π^-p) at very small dipion momenta offers a method to measure the phase of the forward hadronic (quasi-) elastic amplitude γp → ρp. We estimate the potential of such measurements at HERA. Received: 19 February 2004, Revised: 1 August 2005, Published online: 3 November 2005     

QCD analysis of experimental polarized deep-inelastic-scattering data

A detailed review of the current state of investigations into polarized deep inelastic scattering (DIS) is presented. Special attention is given to the methods of the QCD analysis of experimental data on these processes and to the methods of extrapolation of polarized structure functions and polarized quark distributions in the regions inaccessible to current experiments. In the case of pure inclusive processes, the QCD analysis of all worldwide data, including the latest COMPASS data, is presented in detail. Special attention is given to such important components of the nucleon-spin problem as the polarized strangeness and polarized gluon distribution. The features of SIDIS processes are considered; in particular, the role of fragmentation functions in the analysis of the semi-inclusive data is discussed. The methods of extracting the fragmentation functions from experimental data are considered in detail, and the corresponding results are presented. The results of analysis of the existing semi-inclusive polarized data both in the QCD leading order and in the next-to-leading order are considered. Special attention is given to non-standard, so-called difference asymmetries, which make it possible to minimize the dependence of results of analysis on the fragmentation functions. The current methods of QCD analysis of semi-inclusive polarized data are critically reviewed. An alternative method of QCD analysis of semi-inclusive data is presented for next-to-leading order QCD. Advantages of the method in practical applications are illustrated by the example of analysis of the HERMES data.