Magnetic properties of Sn/1-x/Cr/x/Te diluted magnetic semiconductors

We present the studies of Sn/1-x/Cr/x/Te semimagnetic semiconductors with chemical composition x ranging from 0.004 to 0.012. The structural characterization indicates that even at low average Cr-content x < ?0.012, the aggregation into micrometer size clusters appears in our samples. The magnetic properties are affected by the presence of clusters. In all our samples we observe the transition into the ordered state at temperatures between 130 and 140 K. The analysis of both static and dynamic magnetic susceptibility data indicates that the spin-glass-like state is observed in our samples. The addition of Cr to the alloy seems to shift the spin-glass-like transition from 130 K for x = 0.004 to 140 K for x = 0.012.Comment: 4 pages, 4 figure

Morphology of PbTe crystal surface sputtered by argon plasma under Secondary Neutral Mass Spectrometry conditions

We have investigated morphology of the lateral surfaces of PbTe crystal samples grown from melt by the Bridgman method sputtered by Ar+ plasma with ion energy of 50-550 eV for 5-50 minutes under Secondary Neutral Mass Spectrometry (SNMS) conditions. The sputtered PbTe crystal surface was found to be simultaneously both the source of sputtered material and the efficient substrate for re-deposition of the sputtered material during the depth profiling. During sputtering PbTe crystal surface is forming the dimple relief. To be redeposited the sputtered Pb and Te form arrays of the microscopic surface structures in the shapes of hillocks, pyramids, cones and others on the PbTe crystal sputtered surface. Correlation between the density of re-deposited microscopic surface structures, their shape, and average size, on the one hand, and the energy and duration of sputtering, on the other, is revealed

The magnetic interactions in spin-glasslike Ge/1-x-y/Sn/x/Mn/y/Te diluted magnetic semiconductor

We investigated the nature of the magnetic phase transition in the Ge/1-x-y/Sn/x/Mn/y/Te mixed crystals with chemical composition changing in the range of 0.083 < x < 0.142 and 0.012 < y < 0.119. The DC magnetization measurements performed in the magnetic field up to 90 kOe and temperature range 2-200 K showed that the magnetic ordering at temperatures below T = 50 K exhibits features characteristic for both spin-glass and ferromagnetic phases. The modified Sherrington - Southern model was applied to explain the observed transition temperatures. The calculations showed that the spin-glass state is preferred in the range of the experimental carrier concentrations and Mn content. The value of the Mn hole exchange integral was estimated to be J/pd/ = 0.45+/-0.05 eV. The experimental magnetization vs temperature curves were reproduced satisfactory using the non-interacting spin-wave theory with the exchange constant J/pd/ values consistent with those calculated using modified Sherrington - Southern model. The magnetization vs magnetic field curves showed nonsaturating behavior at magnetic fields B < 90 kOe indicating the presence of strong magnetic frustration in the system. The experimental results were reproduced theoretically with good accuracy using the molecular field approximation-based model of a disordered ferromagnet with long-range RKKY interaction.Comment: 9 pages, 6 figure

Collection of microorganisms of ICG SB RAS as a genetic resource for biotechnology

Genetic knowledge of microorganisms plays a critical role in the creation of new biotechnologies, since the effectiveness of any biotechnology is determined by the particular qualities of the structurally functional organization of molecular-genetic systems and their components used for the production of targeted products. Collections of microbial cultures play a decisive role in mobilizing biological resources and make it possible to form a solid base for genetic, molecular biological and biotechnological research. The aim of this work was to assess the key molecular-genetic and phenotypic characteristics of strains of the collection of microorganisms created in the “FRC Institute of Cytology and Genetics of the Siberian Branch of the Russian Academy of Sciences” as a genetic resource for biotechnology. Thirty strains of microorganisms of the collection were isolated by employees of the FRC ICG SB RAS from extreme natural ecosystems, the key molecular-genetic and phenotypic characteristics were described using modern methods of molecular biology and mass-spectrometry. DNA isolation and the sequencing of 16S rRNA gene sequences were performed. The strains of the collection were characterized by morphological, physiological, moleculargenetic and mass-spectrometric characteristics. The particular qualities of growing of strains on different substrates have been established, the study of cell morphology has been carried out. The physiological characteristics of the strains of the collection have been established: the attitude to oxygen, the type of nutrition, the range of temperature and pH, the attitude to NaCl and others. Different resistance of strains to antibiotics has been established. The creation of personal mass spectra of protein profiles of the studied strains of the collection was carried out. The resulting DNA sequences of the strains are deposited in the GenBank. The chemotaxonomic characteristics of strains have been determined. The biotechnological properties of the strains were assessed, the amount of metabolites (ethanol, lactic and acetic acids) in the culture liquid was determined. The value of the collection of microorganisms of the FRC ICG SB RAS as a genetic resource for biotechnology and bioengineering is determined not only by the species diversity of its strains, but also by a wide range of their area isolation and by the depth of their characterization using the widest arsenal of both classical and modern methods (including methods of genomics, proteomics, transcriptomics and bioinformatics)

An integrated method for taxonomic identif ication of microorganisms

For accurate species-level identification of microorganisms, researchers today increasingly use a combination of standard microbiological cultivation and visual observation methods with molecular biological and genetic techniques that help distinguish between species and strains of microorganisms at the level of DNA or RNA molecules. The aim of this work was to identify microorganisms from the ICG SB RAS Collection using an integrated approach that involves a combination of various phenotypic and genotypic characteristics. Key molecular-genetic and phenotypic characteristics were determined for 93 microbial strains from the ICG SB RAS Collection. The strains were characterized by means of morphological, physiological, moleculargenetic, and mass-spectrometric parameters. Specific features of the growth of the strains on different media were determined, and cell morphology was evaluated. The strains were tested for the ability to utilize various substrates. The strains studied were found to significantly differ in their biochemical characteristics. Physiological characteristics of the strains from the collection were identified too, e. g., the relationship with oxygen, type of nutrition, suitable temperature and pH ranges, and NaCl tolerance. In this work, the microorganisms analyzed were combined into separate groups based on the similarities of their phenotypic characteristics. This categorization, after further refinement and expansion of the spectrum of taxa and their metabolic maps, may serve as the basis for the creation of an “artificial” classification that can be used as a key for simplified and quicker identification and recognition of microorganisms within both the ICG SB RAS Collection and other collections

GC-based chemoprofile of lipophilic compounds in Altaian Ganoderma lucidum sample

The presented data contains information about component composition of lipophilic compounds in Ganoderma lucidum fungal body sample obtained using gas chromatography and subsequent mass spectrometry