Modeling the fundamental characteristics and processes of the spacecraft functioning

The fundamental aspects of modeling of spacecraft characteristics by using computing means are considered. Particular attention is devoted to the design studies, the description of physical appearance of the spacecraft, and simulated modeling of spacecraft systems. The fundamental questions of organizing the on-the-ground spacecraft testing and the methods of mathematical modeling were presented

Compositional heterogeneity of picroilmenite from the Zarnitsa pipe according to the data of thermomagnetic analysis

Thirty-nine samples of picroilmenites from seven boreholes drilled along the submeridional profile in the Zarnitsa pipe of the Yakut diamondiferous province are examined. Individual microprobe determinations are conducted on two mutually perpendicular profiles of each sample in order to study compositional the heterogeneity of picroilmenite. Besides, the thermomagnetic curves are recorded for each sample. The model for processing the thermomagnetic curves based on the dependence of the parameters of the thermomagnetic curves (the Curie points and specific magnetic moment of picroilmenite) on hematite content in picroilmenite is suggested. The correct description of the experimental curve for each picroilmenite sample requires introducing two distributions of hematite concentration. The mean value of the first distribution coincides with the microprobe determinations, while the second distribution has a higher hematite content than the first one. It is shown that the areas with increased hematite content in the picroilmenite grains gravitate to the edges of the grains. It is hypothesized that the increase in hematite content is caused by epigenetic transformation of primary picroilmenite and it can probably serve as a proxy for the dynamics of picroilmenite formation. The applicability of the data of thermomagnetic analysis for the express determination of picroilmenite composition is assessed; the capabilities and limitations of the suggested procedure are demonstrated. © 2014 Pleiades Publishing, Ltd

Influence of carbon nanotubes on surfactants supramolecular structures

The surfactant-base membrane mimetic supramolecular structures and their reaction on the presence of carbon nanotubes were studied. On an example of cetyltrimethylammonium bromide (CTAB) it was shown that CTAB molecules can form structures which in texture, shape and sizes imitate the morphology of biological membranes, - the sheets with a typical size of several tens of micrometers. It has been established that the presence of carbon nanotubes leads both to the change in the characteristic size of the sheets in the direction of their increase, and the appearance of new structural state - the sheets which form the «flower structures» (nanoflowers). This means that the presence of the carbon nanoparticles may change the geometry of the membrane structure, thereby altering membrane properties and thus causing disturbances in the activity of biological organisms

P-tert-Butylthiacalix[4]arenes equipped with guanidinium fragments: Aggregation, cytotoxicity, and DNA binding abilities

© The Royal Society of Chemistry 2016.Mono-, di- and tetracationic thiacalix[4]arenes in a 1,3-alternate conformation functionalized with guanidinium groups showed a strong dependence of the aggregation properties with the ratio of guanidinium/n-decyl fragments attached to phenolic groups. Increasing the amount of guanidinium fragments improved the macrocycles solubility in water as well as the sorption capacity towards polynucleotide molecules. The synthesized thiacalixarenes showed relatively high toxicity comparable with that for similar receptors based on the classical calixarene

Dependence of the composition of the Zarnitsa pipe picroilmenites (Yakutia) on their formation conditions (from data of thermomagnetic studies)

A thermomagnetic analysis has been performed for 737 picroilmenite samples from the cores of eight boreholes in the N-S-striking drilling profile of the Zarnitsa kimberlite pipe in the Daldyn kimberlite field, Yakutia. Based on the shapes of thermomagnetic curves and the Curie points, 29 samples were chosen for detailed microprobe studies of chemical composition and elucidation of the dependence of their thermomagnetic parameters on the content of the hematite end-member in the picroilmenites. The thermomagnetic curves of most of the studied picroilmenite samples are approximated by a two-component model for the hematite end-member distribution: the main and supplementary distribution. The average hematite end-member content in the main distribution coincides with the probe microanalysis data and is always lower than the average content in the supplementary distribution. The relative hematite end-member contents in the main and supplementary distributions within the picroilmenite grains are indicators of the dynamics of mineral formation in different parts of the Zarnitsa pipe. The data obtained testify to the multistage formation of the pipe under unstable thermodynamic conditions, which explains the intricate distribution pattern of picroilmenite. © 2014

The nature of the high values of the anisotropy of magnetic susceptibility of rock samples with polydomain ferromagnetics

Samples of different rocks, which possess high values of the anisotropy of magnetic susceptibility, were studied by the magneto-mineralogical and optical methods and by microprobe analysis. It was established that for the samples, which contain the pseudo-single-domain ferromagnetite elongated particles, the source of the anisotropy of magnetic susceptibility is the distribution anisotropy of not only ferromagnetic grains themselves, but also ferromagnetic patterns in the heterogeneous accessory minerals. For samples with multidomain ferromagnetic materials, the nature of the anisotropy of magnetic susceptibility is caused by the orientation of the ilmenite lamellar phase in the structures of disintegration of titanomagnetites or by the orientation of the ferromagnetic structures of disintegration in iron sulfides. © Pleiades Publishing, Ltd. 2009

The percolation phenomenon and fractal dimension of natural silicates

© (2015) Trans Tech Publications, Switzerland. Many physical effects, such as dc conductivity and percolation, depend on the morphology of the silicate structure and its relationship to adsorbed water. These effects play an important role in numerous technological applications, in geology, oil-extracting industry, and other practical fields. In this study, all the samples: natural montmorillonite, kaolinite, and ?linoptilolite with different exchangeable cations in their structures, - were stored in ambient air humidity. The investigation was carried by using two separate techniques, namely Dielectric Spectroscopy and a fractal analysis of electron micrographs. The aims of this work were to analyze the complex relaxation behavior of the relaxation process in temperature range -70°C ÷ 70°C and to determine the fractal dimensions of silicates from the dielectric response at percolation. Dielectric measurements in the frequency range of 1 Hz ÷ 1 MHz were performed using a BDS 80 Dielectric Spectrometer based on an Alpha Impedance Analyzer (Novocontrol). The micrographs were analyzed using a special Matlab based program. The analysis of aspects of the dielectric relaxation spectra related to percolation was used for the determination of the numerical characteristics of geometric heterogeneity of natural silicates. The percolation temperatures of the studied samples were determined. The percolation phenomenon in the silicates is related to the transfer of the electric excitation within the developed network of open pores due to the migration of protons and ions along the surface of connected pores on the outer surfaces of the granules. The analysis of these processes allows one to extract the fractal dimensions associated with the migration of charge carriers within the porous medium. Fractal dimensions of the silicates calculated in two ways: from dielectric spectroscopy study and from fractal analysis of the micrographs, - are in good agreement with each other. It was demonstrated that conventional method of the spatial fractal dimension determination using fractal analysis of electron micrographs leads to overestimation in the case of spatial fractal bounded by a surface fractal. The dielectric spectroscopy method is free from such overestimation

Interfacing multicellular organisms with polyelectrolyte shells and nanoparticles: A caenorhabtidis elegans study

We report the surface modification of microscopic live multicellular nematodes Caenorhabtidis elegans with polyelectrolyte multilayers (pure and doped with 20 nm gold nanoparticles) and the direct magnetic functionalization of nematodes with biocompatible magnetic nanoparticles. Magnetically functionalized "ironoxideclad" nematodes can be effectively separated and moved using an external magnetic field. The surface-functionalized nematodes preserve their viability and reproduction. © 2011 American Chemical Society

EPR and SEM study of organo-mineral associations in lower permian evaporite dolomites

Lower Permian (280 to 300 Ma) evaporite dolomite rocks from the western part of the East European platform were studied by optical microscopy, scanning electron microscopy with microprobe analysis, and X-band electron paramagnetic resonance (EPR). Microscopic studies showed that many dolomite grains consist of an aggregation of submicron dolomite crystals (0.2-2 μm) as a spheroidal nucleus which is overgrown by a larger dolomite rhombohedron (5-20 μm). The EPR spectrum of a raw rock sample is mainly determined by thermally unstable radiation centers and Mn 2+ ions substituted at Ca and Mg sites in the dolomite crystal structure. The presence of dispersed organic matter at low concentrations was revealed from the backscattered electron images with a microprobe analysis of carbon-enriched areas on cleaved surfaces and the registration of the carbon-centered free organic radical signal in EPR spectra of heat-treated samples. A model of two successive growing stages for dolomite grains is suggested: the dolomite (or dolomite precursor) nucleation and aggregation in the colloidal stage to form suspended organo-mineral particles before the gravitational settling, and early diagenetic overgrowth at lower temperature and more stable environment of the marine bottom to form a dolomite rhombohedron. The observation of both growing stages for dolomite grains indicates that there was no recrystallization in the later stages of the rock history. © Springer-Verlag 2009

A review on the fabrication and properties of platinum nanoparticles

© 2014 Advanced Study Center Co. Ltd. A review on chemical and physical preparation of platinum nanoparticles and some applications with these nanoparticles is presented. Application perspectives such fields as nanocatalysts, electrical conductivity, optics and nonlinear optics are demonstrated. Different parameters and condition of various fabrication technologies are considered and realized specific physical properties of platinum nanoparticles are discussed