The functional structure and the design of a CVD reactor for the synthesis of vertically oriented carbon nanotube (VOCNT) arrays on silicon substrates are described. To synthesize VOCNTs, various organic compounds, viz., toluene, cyclohexane, and acetonitrile, and their mixtures in the liquid state were tested under normal conditions.

The gas-discharge detector is designed for the neutron lifetime spectrometer. The detector is intended for ultracold neutron flux monitoring in measurement cycles at the specrtometer (ILL, Grenoble, France). The detector has been successively tested with a Pu–Be neutron source under laboratory conditions and as a part of the spectrometer.

The technical requirements of a system that continually monitors the condition of the safety barriers of nuclear power plants are substantiated. It is shown for the example of the Rostov NPP that power units with VVER which are operating, under construction, or in the design stage can be equipped with a measuring system for monitoring radiation leaks from the steam generators. This improves safety (by not allowing emergency situations) and increases the installed capacity utilization factor (by eliminating unjustified shutdowns of power units) of operating power plants.

Multi-wire proportional chambers filled with the He + CF4 gas mixture with a delay line readout are widely used for thermal neutron detection, especially in Small-Angle Neutron Scattering (SANS) instruments [1–3]. The purpose of the discussed work was to find a set of strongly interrelated detector design parameters with the aim to improve the detector performance. After careful consideration of important detector parameters, such as the space resolution, the efficiency and differential and integral nonlinearity, a satisfactory solution was found. In order to guarantee a reliable and optimal operation of the neutron detector, a wide range of scientific and technological investigations was carried out to: • improve and optimize the detector mechanical characteristics, simulations of the detector pressure behavior up to 10 bar were performed; • minimize the detector outgassing, a new technology for fabrication of the detector electrodes was successfully developed. It has opened a way to improve the gas purity by a few orders of magnitude; • minimize the gas leakage to a level smaller than 0.03 % per day, the detector gas sealing technology was improved. This paper describes general approaches and technological solutions that have allowed us to develop thermal neutron detectors for the SANS diffractometers “Vector” and “Membrana-2” at the VVR-M reactor of PNPI. The required parameters of the detector are listed in Table 1.

The aim of investigation was to develop a system for protein sustained release based on the use of poly(3-hydroxybutyrate) (PHB) microcapsules loaded with bovine serum albumin (BSA).Materials and Methods. To develop microcapsule we used PHB obtained microbiologically by a strain-producer Azotobacter chroococcum 7B. Microcapsules loaded with model protein BSA were produced by double emulsion technique "water/oil/water". Morphology of microcapsules was investigated by methods of confocal and scanning electron microscopy, when the loading and release of BSA was examined spectrophotometrically. In vivo biocompatibility of microcapsules was studied in accordance with intramuscular implantation and histology findings.Results. The study of BSA incorporation and its sustained release from microcapsules for more than 190 h demonstrated the efficacy of proposed system. The mechanism of protein release was found to occur due to the rupture of polymer walls. Moderate tissue response to the implantation of obtained microcapsules was demonstrated.Conclusion. Developed PHB microcapsules loaded with BSA are good model of long acting protein drugs.

Hydrolytic degradations of biodegradable poly(3-hydroxybutyrate) (PHB), polylactide (PLA) and their derivatives were explored by kinetic and structure methods at 37 and 70°C in phosphate buffer. It was revealed the kinetic profiles for copolymer PHBV (20% of 3-hydroxyvalerate) and the blend PHB-PLA (1:1 wt. ratio). The intensity of biopolymer hydrolysis depending on temperature is characterized by total weight loss and the viscosity-averaged molecular weight decrement (ΔMW) as well as by WAXS and AMF techniques. Characterization of PHB and PHBV includes both ΔMW and crystallinity evolution (x-ray diffraction) as well as the AFM analysis of PHB film surfaces before and after aggressive medium exposition. The degradation is enhanced in the series PHBV < PHB < PHB-PLA blend < PLA. The impact of MW on the biopolymer hydrolysis is shown.

We focused on hydrolytic degradation kinetics at 310 and 343 K in phosphate buffer to compare PLA and PHB kinetic profiles. Besides, we revealed the kinetic behavior for copolymer PHBV (20 % of 3-hydroxyvalerate) and the blend PHB-PLA (1:1). The intensity of biopolymer hydrolysis is characterized by total weight lost and the viscosity-averaged molecular weight (MW) decrement. The degradation is enhanced in the series PHBV < PHB < PHB-PLA blend < PLA. Characterization of PHB and PHBV includes MW and crystallinity evolution (X-ray diffraction) as well as AFM analysis of PHB film surfaces before and after aggressive medium exposition. The important impact of MW on the biopolymer hydrolysis is shown.

A biodegradable polymer of bacterial origin, poly(3-hydroxybutyrate) (PHB), is intensively studied as biomaterial for tissue engineering. However, factors determining its biocompatibility still require better understanding. To analyze the PHB films biocompatibility, the polymer material was modified by hydrophilic polymer, poly(ethylene glycol) 300 (PEG). The blends PHB/PEG with different PEG content (10, 20, 30 and 50%) were produced by subsequent incubation in water resulted in removal of 95% PEG. The surface roughness and hydrophilicity were studied by atomic force microscopy (AFM) and contact angle "water-polymer" measurement, respectively. The film biocompatibility on cell culture of COS-1 fibroblasts was studied in vitro. It was shown that both roughness and hydrophobicity are directly proportional to initial PEG content in the PHB/PEG blends. The growth rate of COS-1 fibroblasts on polymer films is determined by combination of two basic physicochemical properties of the polymer surface: the roughness and hydrophilicity. The optimal roughness requred for COS-1 cells growth is the average roughness more than 25 nm, whereas the limit values of the contact angle "water-polymer" that was responsible for relatively high cell viability were not found. These data indicate that the film surface roughness had the greatest effect on the cell growth, whereas the increase in the polymer surface hydrophilicity caused the additional positive effect on viability of attached cells. Thus, the modification of PHB polymer material by PEG resulted in the improved viability of cells cultivated on the polymer films in vitro. The obtained data can be used for development of such medical devices as surgeon patches and periodontal membranes.

The present paper deals with investigation of the possibilities for reducing the risk of proliferation of fissionable materials by means of increasing the degree of protection of fresh fuel intended for light-water reactors against unsanctioned use in the case of withdrawal of a recipient country of deliveries from IAEA safeguards. It is shown that the use of recycled uranium for manufacturing export nuclear fuel makes transfer of nuclear material removed from the fuel assemblies for weapons purposes difficult because of the presence of isotope 232 U, whose content increases when one attempts to enrich uranium extracted from fresh fuel. In combination with restricted access to technologies for isotope separation by means of establishing international centers for uranium enrichment, this technical measure can significantly reduce the risk of proliferation associated with export deliveries of fuel made of low-enriched uranium. The assessment of a maximum level of contamination of nuclear material being transferred by isotope 232 U for the given isotope composition of the initial fuel is obtained. The concept of further investigations of the degree of security of export deliveries of fuel assemblies with recycled uranium intended for light-water reactors is suggested.

The ability of Azotobacter chroococcum strain 7B, producer of poly(3-hydroxybutyrate) (PHB), to synthesize its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)) was studied. It was demonstrated, for the first time, that A. chroococcum strain 7B was able to synthesize P(3HB-co-3HV) with various molar rates of HV in the polymer chain when cultivated on medium with sucrose and carboxylic acids as precursors of HV elements in the PHB chain, namely, valeric (13.1–21.6 mol %), propanoic (3.1 mol %), and hexanoic (2.1 mol %) acids. Qualitative and functional differences between PHB and P(3HB-co-3HV) were demonstrated by example of the release kinetic of methyl red from films made of synthesized polymers. Maximal HV incorporation into the polymer chain (28.8mol %) was recorded when the nutrient medium was supplemented with 0.1% peptone on the background of 20 mM valerate. These results suggest that that the studied strain can be regarded as a potential producer of not only PHB but also P(3HB-co-3HV).

The manufacturing line for the development and fabrication of position-sensitive detectors of thermal neutrons has been organized at the Petersburg Nuclear Physics Institute of the Russian Academy of Sciences. Three detectors with sensitive regions 300 × 170 (prototype), 200 × 200, and 300 × 300 mm in size have been constructed to date. The detectors represent multiwire proportional chambers with cathode data readout to a delay line. The devices are filled with the 3He/CF4 gas mixture. These detectors are intended for modernizing the detector systems of the Vector and Membrana-2 diffractometers (VVR-M reactor, Konstantinov Petersburg Nuclear Physics Institute of the Russian Academy of Sciences, Gatchina, Russia).

The aim of this study was to evaluate and to compare the long-term kinetics curves of biodegradation of poly(3-hydroxybutyrate) (PHB), its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and a PHB/polylactic acid composite. The total weight loss and the change of average viscosity molecular weight were used as the parameters reflecting the biodegradation degree. The rate of biodegradation was analyzed in vitro in the presence of lipase and in vivo after film implantation in animal tissues. The morphology of the PHB film surface was studied by the atomic force microscopy technique. It was shown that PHB biodegradation involves both polymer hydrolysis and its enzymatic biodegradation. The results obtained in this study can be used for the development of various PHB-based medical devices.

The kinetics of the controlled release of the antiproliferative drug dipyridamole from microspheres based on the biocompatible and biodegradable polymer poly(3-hydroxy)butyrate is studied. As carriers for dipyridamole, microspheres prepared from a solution of poly(3-hydroxy)butyrate by single emulsion method are used. Under in vitro conditions, the kinetic curves describing the release of dipyridamole from microspheres with diameters of 19, 63, and 92 μm show two characteristic regions: the region of fast drug release within a short time period and a well-pronounced continuous linear region. For microspheres with a diameter of 4 μm, the linear region is missing. Analysis of the kinetic curves illustrating controlled drug release together with the measurements on polymer degradation shows that their kinetic profiles depend on the diffusion-controlled process and hydrolytic degradation of poly(3-hydroxy)butyrate. The diffusion kinetic equation describing both linear and nonlinear regions of dipyridamole released from the microspheres involves the sum of two terms: desorption from the sphere via the diffusion-controlled mechanism and drug release via the zero-order reaction. The linear region of the drug release curve is explained by the zero-order hydrolysis of poly(3-hydroxy)butyrate. The diffusion coefficients and kinetic constants are calculated. For bigger microspheres, the existence of the continuous linear region in the corresponding kinetic curves makes it possible to use microsystems based on poly(3-hydroxy)butyrate and dipyridamole as novel systems for local prolonged drug delivery.

The Green-Schwarz covariant N=2 superstring action can be consistently deduced as the action of the Wess-Zumino-Witten (WZW) sigma model defined on the direct product of two N=1, D=10 Poincar\'e supertranslation groups. Generalizing this result, we construct new WZW sigma models on the supergroups with a nonabelian even part and interpret them as models of superstrings moving on the supergroup manifolds. We show that these models are completely integrable and in some special cases possess fermionic kappa-symmetry.

The oxidation of ortho-xylene to phthalic anhydride in a catalytic fluidized-bed reactor was simulated. The mathematical model implied that the reactor was separated into two temperature zones throughout the height of the bed and the catalyst circulated between these zones. The parameters responsible for the regulation of the catalyst state and, correspondingly, the process selectivity, were analyzed. It was found that the temperatures in the zones and the rate of catalyst circulation between them affected the selectivity of the reaction.

The aim of this study was to evaluate and to compare of long-term kinetics curves of biodegradation of poly(3-hydroxybutyrate) (PHB), its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and PHB/polylactic acid blend. The total weight loss and the change of average viscosity molecular weight were used as an index of biodegradation degree. The rate of biodegradation was analyzed in vitro in presence oflipase and in vivo when the films were implanted in animal tissues. The morphology of PHB films surface was studied by atomic force microscopy technique. It was shown that biodegradation of PHB is occurred by means of as polymer hydrolysis, and as its enzymatic biodegradation. The obtained data can be used for development of medical devices on the base of PHB.