Synthesis of 5H-[1,3]thiazolo[3,2-a]pyrimidin-5-one derivatives

The reaction of 2-aminothiazoles with ethyl acetoacetate in acetic or polyphosphoric acid gave a series of 5H-[1,3]thiazolo[3,2-a]pyrimidin-5-one derivatives which were nitrated with a mixture of nitric and sulfuric acid to 6-nitro-5H-[1,3]thiazolo[3,2-a]pyrimidin-5-ones, and the latter were reduced to the corresponding amines.     

Experimental study of cyclic action of plasma on tungsten

We report on experimental results on multiple action of hydrogen, deuterium, and helium plasmas produced by a plasma gun and the Globus-M tokamak on tungsten. The surface temperature in the course of irradiation is measured with a bichromatic pyrometer with a time resolution of ?1 μs. The morphology of the surface layer is investigated and X-ray structure analysis of tungsten exposed to multiple radiations by the plasma under various conditions is carried out. A slight decrease in the lattice parameter in the sample subjected to the maximal number of irradiation cycles is detected. It is shown that the morphology of the tungsten surface irradiated by the hydrogen plasma from the gun and by the deuterium plasma from the Globus-M tokamak changes (the structure becomes smoother). The characteristic depth of the layer in which impurities have been accumulated exceeds 0.5 μm. This depth was the largest for the sample exposed to 1000 shots from the gun and 2370 shots from the tokamak. It is shown that the helium jet from the plasma gun makes it possible to simulate the action of helium ions on the International Thermonuclear Experimental Reactor (ITER) diverter, producing a layer of submicrometer particles (bubbles).     

Formation of the single-phase ferromagnetic semiconductor (Ga,Mn)As by pulsed laser annealing

It is shown that (Ga,Mn)As layers formed by Mn⁺ ion implantation into GaAs and subsequent annealing by an excimer laser pulse with an energy density to 200–300 mJ/cm² feature the properties of the p-type semiconductor and ferromagnetic properties. The threshold dose of implanted ions (~10¹⁵ cm^–2) for activating Mn acceptors is determined. The sheet hole concentration and the Curie temperature increase with further increasing Mn⁺ ion dose. Hysteresis loops in the magnetic field dependences of the Hall effect, the negative magnetoresistance, and magnetic and structural studies suggest that the layers are analogues of single-phase ferromagnetic compounds (Ga,Mn)As formed by low-temperature molecular beam epitaxy.     

Measurement and simulation of the rates of threshold reactions in a W—Na target bombarded with 0.8-GeV protons

The results of experimental measurement and numerical simulation of 979 rates of threshold reactions in 142 samples of ²⁰⁹Bi, ¹⁹⁷Au, ¹⁸¹Ta, ¹⁶⁹Tm, ¹¹⁵In, ⁹³Nb, ⁶⁵Cu, ⁶⁴Zn, ⁶³Cu, ⁵⁹Co, ²⁷Al, ¹⁹F, and ¹²C placed inside and outside of a “thick” W-Na target irradiated with 0.8-GeV protons are reported. The reaction rates are measured by the method of γ spectrometry using Ge and GeLi semiconductor detectors. The numerical calculations were performed using the LAHET code package together with the EXFOR database and the evaluated data libraries MENDL2N, MENDL2P, and IEAF2001. The experimental and calculated results are compared and the most significant discrepancies are analyzed.     

Thin films of YBaCuO high-temperature superconductor grown in a simplified magnetron sputterer and their microwave application

The physicochemical properties of YBa₂Cu₃O_7?δ high-temperature superconductor exclude designing standard magnetron sputterers and adopting standard film growth conditions that would ensure good and highly reproducible results. A simple and flexible magnetron sputterer making it possible to grow high-quality films (with a critical temperature of 90 K, a critical current density of 4 MA/cm², and a surface resistance of ≤0.5 mΘ at a frequency of 10 GHz and 77 K) is described. The high quality of the films is proved by successfully applying them in a microwave circuit demonstrating an intrinsic Q factor of 58 000 at a frequency of 70 MHz and 77 K, which is higher than the results obtained by other teams of researchers.     

A feasibility study of X‐ray phase‐contrast mammographic tomography at the Imaging and Medical beamline of the Australian Synchrotron

Results are presented of a recent experiment at the Imaging and Medical beamline of the Australian Synchrotron intended to contribute to the implementation of low‐dose high‐sensitivity three‐dimensional mammographic phase‐contrast imaging, initially at synchrotrons and subsequently in hospitals and medical imaging clinics. The effect of such imaging parameters as X‐ray energy, source size, detector resolution, sample‐to‐detector distance, scanning and data processing strategies in the case of propagation‐based phase‐contrast computed tomography (CT) have been tested, quantified, evaluated and optimized using a plastic phantom simulating relevant breast‐tissue characteristics. Analysis of the data collected using a Hamamatsu CMOS Flat Panel Sensor, with a pixel size of 100 µm, revealed the presence of propagation‐based phase contrast and demonstrated significant improvement of the quality of phase‐contrast CT imaging compared with conventional (absorption‐based) CT, at medically acceptable radiation doses.     

The procedure and results of calculations of the equilibrium isotopic composition of a demonstration subcritical molten salt reactor

A subcritical molten salt reactor with an external neutron source is studied computationally as a facility for incineration and transmutation of minor actinides from spent nuclear fuel of reactors of VVER-1000 type and for producing ²³³U from ²³²Th. The reactor configuration is chosen, the requirements to be imposed on the external neutron source are formulated, and the equilibrium isotopic composition of heavy nuclides and the key parameters of the fuel cycle are calculated.     

Catalytically active platinum blacks prepared by magnetron sputtering in vacuum and their using in fuel cells with solid polymer electrolyte

Highly disperse platinum film were vacuum-plasma-deposited onto titanium foil and gas-diffusion layers. The platinum deposits have complicated structure. By measuring hydrogen desorption peaks, the catalysts’ active specific surface area was determined and the roughness factor calculated. The electrochemical activity of the electrodes on gas-diffusion layers in the oxygen reduction and hydrogen oxidation reactions was determined. It was shown that the catalysts’ specific activity depends on the platinum content and the Nafion-ionomer additive. The high-activity electrodes were tested in Membrane Electrode Assemblies of low-temperature fuel cells.     

Effect of Liquid-Phase Oxidative Treatments on the Purity,Hydrophilicity, and Structure of Single-Wall Carbon Nanotubes and on the Electrical Conductivity of Their Arrays

Russian Journal of Applied Chemistry - A study using a set of physicochemical methods has shown that treatment of single-wall carbon nanotubes synthesized by the electric arc method with an aqueous...     

Effect of a solvent on self-organization in nanofilms: Modeling by the dissipative particle dynamics method

Mesoscopic simulation of processes of drying and swelling of thin copolymer films on a solid substrate is performed. Structural rearrangements in films of symmetric and asymmetric diblock copolymers are studied by the dissipative particle dynamics method in the presence of both nonselective and selective solvents. The plasticizing effect of a solvent is favorable for formation of lamellar and hexagonal mesophases. Owing to evaporation of the solvent from a film or its absorption from the external volume, flows along the normal to the film surface arise. These flows exert an orienting effect on the microdomain structure.