Water Content and Superconductivity in Na0.3CoO2*yH2O

We report here the correlation between the water content and superconductivity in Na0.3CoO2*yH2O under the influences of elevated temperature and cold compression. The x-ray diffraction of the sample annealed at elevated temperatures indicates that intergrowths exist in the compound at equilibrium when 0.6 < y < 1.4. Its low-temperature diamagnetization varies linearly with y, but is insensitive to the intergrowth, indicative of quasi-2D superconductivity. The Tc-onset, especially, shifts only slightly with y. Our data from cold compressed samples, on the other hand, show that the water-loss non-proportionally suppresses the diamagnetization, which is suggestive of weak links.Comment: 10 pages, 10 figures; submitted to Physica C (August 13, 2003

High Mass-Loading Sulfur-Composite Cathode for High Performance Lithium-Sulfur Batteries

Sulfur remains the focus of attention as a perspective candidate for the cathode material for lithium-ion batteries. First of all, sulfur is cheap and has abundant resources, and secondly, has a high theoretical discharge capacity (1675 mAh g-1). Lithium-sulfur batteries potentially can be applied in the market portable devices and for storage of electrical energy. Nevertheless, implementing Li-S batteries face several difficulties. The challenges are based on low electronic conductivity of sulfur, solubility of polysulfides in the electrolyte and low mass loading of sulfur. Conventional approaches are focused on the loading of sulfur into porous carbon hosts, coating with polymers and encapsulating into various types of carbon materials. This research is aimed to increase mass loading of sulfur in the composite, which in turn requires improvement in the electrical conductivity. The conductivity of sulfur is improved with the use of polyacrylonitrile (PAN) polymer and carbon nanotubes (CNT), while mass loading is increased with the use of carbon fiber paper as a current collector

System of Consumer Services for Population of Western Section of BAM Construction Areas (1974—1989)

The article is devoted to the history of the organization of consumer services for the population in the areas of construction of the BAM western section in 1974—1989. The features of the material and technical support of the household service, the problems of staffing, the structure and dynamics of services in cities and townships of builders are considered. It is noted that the network of consumer services enterprises was designed in a temporary version for the period of construction of the main railway. It is shown that the lag in the development of the public services system was caused by the sectoral mechanism of construction management, adjustments to design estimates, and a reduction in funding for civil construction. It is emphasized that, unlike other objects of the social sphere, which received the support of the all-Union ministries, the organization of the welfare service was under the territorial jurisdiction. In consumer services for the population of the construction site, such problems as a lack of production space, materials and components, an insignificant degree of mechanization and automation of labor, and a high staff turnover have been identified. Summing it up, the author comes to the conclusion that attempts to reform the industry in the second half of the 1980s could not significantly increase the efficiency of the household service in connection with the completion of the BAM construction and the simultaneous crisis of the Soviet system

Field-Induced Resistive Switching in Metal-Oxide Interfaces

We investigate the polarity-dependent field-induced resistive switching phenomenon driven by electric pulses in perovskite oxides. Our data show that the switching is a common occurrence restricted to an interfacial layer between a deposited metal electrode and the oxide. We determine through impedance spectroscopy that the interfacial layer is no thicker than 10 nm and that the switch is accompanied by a small capacitance increase associated with charge accumulation. Based on interfacial I-V characterization and measurement of the temperature dependence of the resistance, we propose that a field-created crystalline defect mechanism, which is controllable for devices, drives the switch.Comment: 4 pages, 3 figure

Enhanced critical current density of YBa2Cu3Ox films grown on Nd1/3Eu1/3Gd1/3Ba2Cu3Ox with nano-undulated surface morphology

We report a simple and easily controllable method where a nano-undulated surface morphology of Nd1/3Eu1/3Gd1/3Ba2Cu3Ox (NEG) films leads to a substantial increase in the critical current density in superconducting YBa2Cu3Ox (YBCO) films deposited by pulsed laser deposition on such NEG layers. The enhancement is observed over a wide range of fields and temperatures. Transmission electron microscopy shows that such YBCO films possess a high density of localized areas, typically 20 x 20 nm2 in size, where distortion of atomic planes give rotational (2 to 5 degrees) moire patterns. Their distribution is random and uniform, and expected to be the origin of the enhanced flux pinning. Magneto-optical imaging shows that these films have excellent macroscopic magnetic uniformity.Comment: 4 pages, 4 figure

Historical Experience in Development of Cultural and Educational Institutions in New Cities of Buryatia in 1950s—1980s

The features of the formation and development of cultural and educational institutions in the new urban settlements of Buryatia in the 1950s—1980s are discussed in the article. On the basis of previously unpublished archival documents, journalistic texts and private sources, the main activities of state and departmental clubs and houses of culture, theater associations, libraries, and museums have been reconstructed. The problems of material and technical support and staffing of cultural institutions are considered; the specifics of the formation of amateur creative teams in the conditions of areas of new economic development are revealed. It is noted that the main trends in the cultural development of Soviet cities were determined by the state, but it was looking for new ways to regulate cultural policy. The authors come to the conclusion that the concentration of young people from different parts of the country in new towns favorably influenced the formation of the cultural environment and contributed to the emergence of various forms and directions of cultural — educational and mass cultural work. It is shown that the cultural life of new cities was provided by amateur art groups. It is noted that the transition of local groups from the amateur to the professional level slowed down due to the material dependence of cultural institutions on the city-forming enterprises, whose departmental interests they were called upon to serve

Differential tissue sparing of FLASH ultra high dose rates: an {\it in-silico} study

Purpose: To propose a theory for the differential tissue sparing of FLASH ultra high dose rates (UHDR) through inter-track reaction-diffusion mechanism. Methods: We calculate the time-evolution of particle track-structures using a system of coupled reaction-diffusion equations on a random network designed for molecular transport in porous and disordered media. The network is representative of the intra- and inter-cellular diffusion channels in tissues. Spatial cellular heterogeneities over the scale of track spacing have been constructed by incorporating random fluctuations in the connectivity among network sites. Results: We demonstrate the occurrence of phase separation among the tracks as the complexity in intra- and inter-cellular structural increases. At the weak limit of disorder, such as in water and normal tissue, neighboring tracks melt into each other and form a percolated network of nonreactive species. In contrast, at the strong limit of disorder, tracks evolve individually like isolated islands with negligible inter-track overlap. Thus, the spatio-temporal correlation among the chemical domains decreases as the inter-cellular complexity of the tissue increases (e.g. from normal tissue to fractal-type malignant tissue). Conclusions: The differential sparing of FLASH UHDR in normal and tumor tissue may be explained by differences in inter- and intra-cellular structural complexities between the tissue types. The structural complexities of cancerous cells prevent clustering and chemical interaction of tracks, whereas this interaction prevails and thus leads to sparing in normal tissue

Field-Driven Hysteretic and Reversible Resistive Switch at the Ag-Pr0.7Ca0.3MnO3 Interface

The hysteretic and reversible polarity-dependent resistive switch driven by electric pulses is studied in both Ag/Pr0.7Ca0.3MnO3/YBa2Cu3O7 sandwiches and single-layer Pr0.7Ca0.3MnO3 strips. The data demonstrate that the switch takes place at the Ag-Pr0.7Ca0.3MnO3 interface. A model, which describes the data well, is proposed. We further suggest that electrochemical diffusion is the cause for the switch.Comment: 4 pages, 3 figures; submitted to Appl. Phys. Lett. (December 17, 2002

Imaging Oxygen Defects and their Motion at a Manganite Surface

Manganites are technologically important materials, used widely as solid oxide fuel cell cathodes: they have also been shown to exhibit electroresistance. Oxygen bulk diffusion and surface exchange processes are critical for catalytic action, and numerous studies of manganites have linked electroresistance to electrochemical oxygen migration. Direct imaging of individual oxygen defects is needed to underpin understanding of these important processes. It is not currently possible to collect the required images in the bulk, but scanning tunnelling microscopy could provide such data for surfaces. Here we show the first atomic resolution images of oxygen defects at a manganite surface. Our experiments also reveal defect dynamics, including oxygen adatom migration, vacancy-adatom recombination and adatom bistability. Beyond providing an experimental basis for testing models describing the microscopics of oxygen migration at transition metal oxide interfaces, our work resolves the long-standing puzzle of why scanning tunnelling microscopy is more challenging for layered manganites than for cuprates.Comment: 7 figure