Possibilities for hypervelocity impact experiments in frames of demonstration project “Space Patrol”

It is proposed to reach impact velocity of macrobodies up to 90 km/s by collision of space probe with celestial bodies in meteor flux. Results of the approach dynamics and targeting simulation shows feasibility of this idea. Science experiments and registration method, based on measuring electromagnetic fields, inducing during the impact, are proposed. It is shown, on the basis of an impact experiment of the small mass body, that it is possible to determine parameters of asteroids such as dynamic strength, crack resistance etc.     

The informative-capacity phenomenon of drying drops.

This investigation shows fundamentally good prospects for the information phenomenon of drying drops in medical diagnostics. The advantages of this method include the high information capacity, the rapid result obtainment, the small invasivity, the possibility of use by individuals without special qualification, and the low cost of the device in mass production. These properties create hope that this technology, after widescale clinical tests and the development of a prototype device, can be useful for making a preliminary diagnosis and extracting a risk group for both screening examinations and home use.     

Effect of filler concentration on the phase separation in poly(vinyl acetate)-poly(methyl methacrylate) mixtures

The temperatures and kinetics of phase separation have been studied as a function of filler concentration in a polymer mixture of poly(vinyl acetate)-poly(methyl methacrylate). The filler was shown to have a marked effect on the cloud point position and the phase separation kinetics at various temperatures. The effects observed are dependent upon the component ratio.     

Transformer ratio and pulse shaping in laser wakefield accelerator

We show that, in complete analogy to the electron-beam driven Plasma Wakefield Accelerator (PWFA), an optimal transformer ratio can be attained in the laser driven Laser Wakefield Accelerator (LWFA), by properly shaping the longitudinal profile of the driving laser pulse. The concept of transformer ratio in LWFA is introduced and the optimal laser pulse shape is derived in the linear regime of laser-plasma interaction. We show that in the linear regime of plasma perturbation the requirement for the laser pulse shape and the resultant optimal transformer ratio are identical for LWFA and PWFA concepts.     

AC long-range phase-coherent effects of S-N-S junctions in the dirty limit

The conductance of a normal metal film (N) in contact with two superconductors (S) is calculated in the presence of a constant and oscillating V_ωcosωt bias voltage between N and S. It is shown that the conductance as a function of has a Shapiro-like step at = ħω/2e. This exists in the case when the spacing between two superconductors largely exceeds the coherence length. It is also shown that the Shapiro step height decreases rapidly when the junction size exceeds the phase breaking length.     

Reduction of CuO in H2: In Situ Time-Resolved XRD Studies

CuO is used as a catalyst or catalyst precursor in many chemical reactions that involve hydrogen as a reactant or product. A systematic study of the reaction of H₂ with pure powders and films of CuO was carried out using in situ time-resolved X-ray diffraction (XRD) and surface science techniques. Oxide reduction was observed at atmospheric H₂ pressures and elevated temperatures (150-300 °C), but only after an induction period. High temperature or H₂ pressure and a large concentration of defects in the oxide substrate lead to a decrease in the magnitude of the induction time. Under normal process conditions, in situ time-resolved XRD shows that Cu¹⁺ is not a stable intermediate in the reduction of CuO. Instead of a sequential reduction (CuO Cu₄O₃ Cu₂O Cu), a direct CuO Cu transformation occurs. To facilitate the generation of Cu¹⁺ in a catalytic process one can limit the supply of H₂ or mix this molecule with molecules that can act as oxidant agents (O₂, H₂O). The behavior of CuO-based catalysts in the synthesis of methanol and methanol steam reforming is discussed in the light of these results.     

Chemisorption of C3 hydrocarbons on cobalt silica supported Fischer–Tropsch catalysts

Chemisorption of propene and propane was studied in a pulse reactor over a series of cobalt silica-supported Fischer–Tropsch catalysts. It was shown that interaction of propene with cobalt metal particles resulted in its rapid autohydrogenation. The reaction consists in a part of the propene being dehydrogenated to surface carbon and CH_x chemisorbed species; hydrogen atoms released in the course of propene dehydrogenation are then involved in hydrogenation of remaining propene molecules to propane at 323–423 K or in propene hydrogenolysis to methane and ethane at temperatures higher than 423 K. The catalyst characterization suggests that propene chemisorption over cobalt catalysts is primarily a function of the density of cobalt surface metal sites. A correlation between propene chemisorption and Fischer–Tropsch reaction rate was observed over a series of cobalt silica-supported catalysts. No propane chemisorption was observed at 323–373 K over cobalt silica-supported catalysts. Propane autohydrogenolysis was found to proceed at higher temperatures, with methane being the major product of this reaction over cobalt catalysts. Hydrogen for propane autohydrogenolysis is probably provided by adsorbed CH_x species formed via propane dehydrogenation. Propene and propane chemisorption is dramatically reduced upon the catalyst exposure to synthesis gas (H₂/CO = 2) at 323–473 K. Our results suggest that cobalt metal particles are probably completely covered by carbon monoxide molecules under the conditions similar to Fischer–Tropsch synthesis and thus, most of cobalt surface sites are not available for propene and propane chemisorption.     

Polymerized high internal‐phase emulsions: Properties and interaction with water

The synthesis and characterization of novel polymerized high internal‐phase emulsions (polyHIPE) materials are described. Homogeneous, highly porous, low‐density, open‐cell crosslinked copolymers were prepared by polymerizing the continuous phase of HIPE containing styrene and varying amounts of 2‐ethylhexyl methacrylate. The glass transition temperatures (T_gs) of the homopolymers were similar to the literature values, but the copolymer T_gs were lower than expected. These results indicate that the copolymer composition is richer in 2‐ethylhexyl methacrylate than the feed composition. The homopolymer moduli, calculated from the foam moduli, were similar to the literature values. The influence of composition and surface treatment on the water absorbed by the foams was investigated. For example, washing a polyHIPE based on poly(ethylhexyl acrylate) in water at 70°C increased water absorption because of the removal of the residual salt. Adding a fluorinated comonomer to the HIPE reduced hydrophilicity and, thus, water absorption. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2018–2027, 2002; DOI 10.1002/app.10555     

Comparative stability of dihydrofolate reductase mutants in vitro and in vivo

Dihydrofolate reductase mutants with amino acid replacementsin the active center (Thr35 Asp mutant, Arg57 His mutant andthe mutant with triple replacement Thr35 Asp, Asn37 Ser, Arg57 His) were obtained by site-directed mutagenesis. The stabilizationeffect of trimethoprim and NADP·H on the protein tertiarystructure in vitro has been investigated. In the case of mutantswith a ‘weak’ tertiary structure (Thr35 Asp35 andthe triple mutant) the separate addition of ligands does notaffect their stability. The simultaneous addition of these ligandsto Thr35 Asp35 and the triple mutant leads to the large increasein their stability. A distinct correlation was found betweenthe in vitro studied stability of the mutant proteins to theurea- or heat-induced denaturation and the level of proteolyticdegradation of these mutants previously observed in vivo.     

Catalytic Oxidation of Thiol Compounds by Novel Fuel Cell-inspired Co-Porphyrin and Co-Imidazole Catalysts

The catalytic performance of pyrolyzed carbon-supported cobalt-nitrogen donor (CoN₄) catalysts for the oxidation of thiol compounds by dioxygen in aqueous solution was studied. This paper continues our previous line of research, which was inspired by the electrocatalytic reduction of oxygen on pyrolyzed carbon-supported cobalt-porphyrins and related tetra-coordinated nitrogen donor-transition metal complexes (MeN₄, where Me stands for a transition metal atom). Both pyrolyzed carbon-supported Co-imidazole and Co-porphyrin exhibited fast catalytic oxidation of the different thiols. The rate of oxidation of different thiols on the pyrolyzed CoN₄ catalysts was compared to the homogeneous rate of oxidation using 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin Co(II) tetrasodium salt as catalyst. Based on the cobalt content, the heterogeneous catalysts always outperformed the homogeneous one, and at times even exhibited 4,100-fold better catalysis. The dependence of the catalytic rate of oxidation on the preparation temperature was investigated, showing an optimal catalysis at ˜650 °C for the cobalt-imidazole catalyst. The decrease in catalytic performance after heat treatment at elevated temperature was attributed to the formation of cobalt metal acting as a generator of carbon nanotubes.