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Observations of the masers in the course of RadioAstron mission yielded detections of fringes for a number of sources in both water and hydroxyl maser transitions. Several sources display numerous ultra-compact details. This proves that implementation of the space VLBI technique for maser studies is possible technically and is not always prevented by the interstellar scattering, maser beaming and other effects related to formation, transfer, and detection of the cosmic maser emission. For the first time, cosmic water maser emission was detected with projected baselines exceeding Earth Diameter. It was detected in a number of star-forming regions in the Galaxy and two megamaser galaxies NGC 4258 and NGC 3079. RadioAstron observations provided the absolute record of the angular resolution in astronomy. Fringes from the NGC 4258 megamaser were detected on baseline exceeding 25 Earth Diameters. This means that the angular resolution sufficient to measure the parallax of the water maser source in the nearby galaxy LMC was directly achieved in the cosmic maser observations. Very compact features with angular sizes about 20\muas\, have been detected in star-forming regions of our Galaxy. Corresponding linear sizes are about 5-10 million kilometers. So, the major step from milli- to micro-arcsecond resolution in maser studies is achieved by the RadioAstron mission. The existence of the features with extremely small angular sizes is established. Further implementations of the space–VLBI maser instrument for studies of the nature of cosmic objects, studies of the interaction of extremely high radiation field with molecular material and studies of the matter on the line of sight are planned.
We present estimates of brightness temperature for 5 galactic masers in star-forming regions detected at space baselines. Very compact features with angular sizes of ~23-60 μas were detected in these regions with corresponding linear sizes of ~4-10×106 km. Brightness temperatures range from 1014 up to 1016 K.
Low temperature (400°C) deposition of ferromagnetic Ni-Mn-Ga thin films is successfully performed via rf magnetron sputtering technique using co-deposition of two targets Ni50Mn50 and Ni50Ga50 on sapphire (0001) and Si (100) substrates. The films are in part amorphous with significant degree of crystallinity. The obtained crystallographic structure is shown to be substrate-dependent. Films on both substrates are ferromagnetic at room temperature (Curie temperature ∼ 332.5K) with well-defined hysteresis loops, low coercivity (∼ 100 Oe) and a saturation magnetization of ∼ 200 emu/cc. At low temperature (5 K), both films show increased magnetization value with wider hysteresis loops having higher coercivity and remanent magnetization. The process is therefore effective in achieving the appropriate thermodynamic conditions to deposit thin films of the Ni-Mn-Ga austenitic phase (highly magnetic at room temperature) at relatively low substrate temperature without the need for post-deposition annealing or further thermal treatment, which is prerequisite for the device fabrication.
General characteristics of methanol (CH3OH) maser emission are summarized. It is shown that methanol maser sources are concentrated in the spiral arms. Most of the methanol maser sources from the Perseus arm are associated with embedded stellar clusters and a considerable portion is situated close to compact HII regions. Almost 1/3 of the Perseus Arm sources lie at the edges of optically identified HII regions which means that massive star formation in the Perseus Arm is to a great extent triggered by local phenomena. A multiline analysis of the methanol masers allows us to determine the physical parameters in the regions of maser formation. Maser modelling shows that class II methanol masers can be pumped by the radiation of the warm dust as well as by free-free emission of a hypercompact region (hcHII) with a turnover frequency exceeding 100 GHz. Methanol masers of both classes can reside in the vicinity of hcHIIs. Modelling shows that periodic changes of maser fluxes can be reproduced by variations of the dust temperature by a few percent which may be caused by variations in the brightness of the central young stellar object reflecting the character of the accretion process. Sensitive observations have shown that the masers with low flux densities can still have considerable amplification factors. The analysis of class I maser surveys allows us to identify four distinct regimes that differ by the series of their brightest lines.
Methanol masers which are traditionally divided into two classes provide possibility to study important parts of the star forming regions: Class II masers trace vicinities of the massive YSOs while class I masers are likely to trace more distant parts of the outflows where newer stars can form.
There are many methanol transitions which produce observed masers. This allows to use pumping analysis for estimation of the physical parameters in the maser formation regions and its environment, for the study of their evolution. Extensive surveys in different masing transitions allow to conclude on the values of the temperatures, densities, dust properties, etc. in the bulk of masing regions. Variability of the brightest masers is monitored during several years. In some cases it is probably caused by the changes of the dust temperature which follow variations in the brightness of the central YSO reflecting the character of the accretion process.
A unified catalogue of the class II methanol masers consisting of more than 500 objects is compiled. Analysis of the data shows that: physical conditions within the usual maser source vary considerably; maser brightness is determined by parameters of some distinguished part of the object–maser formation region; class II methanol masers are formed not within the outflows but in the regions affected by their propagation.
It is shown that the “near” solutions for the kinematic distances to the sources can be used for statistical analysis. The luminosity function of the 6.7 GHz methanol masers is constructed. It is shown that improvement of the sensitivity of surveys can increase number of detected maser sources considerably.
The distribution of class II methanol masers in the Galaxy is constructed on the basis of estimated kinematic distances. It is shown that most of the sources are located in the Molecular Ring and that the dependence of the number of sources on the distance from the Galactic Center has significant peaks at the positions corresponding to the spiral arms.
A survey of CS(2-1) line emission tracing dense gas is performed at Mopra toward the positions of the brightest class II methanol masers. Velocity correlations between the maser and CS lines are analyzed. It is shown that the sources with l from 320 to 350 deg in which the masers are relatively blue-shifted, form a group which is located in the region of the Scutum-Centaurus spiral arm. This can reflect existence of a grand design, i.e., grouping of the sources with similar peculiarity of morphology or evolutionary stage of the massive star forming regions.
Let N(ρ; ω) be the number of points of a d-dimensional lattice Γ. where d≥2, inside a ball of radius ρ centred at the point ω. Denote by (ρ) the number N(ρ; ω) averaged over ω in the elementary cell Ω of the lattice Γ. The main result is the following lower bound for for dimensions d ≅ l(mod 4):
Current models of class II methanol masers are able to describe the brightnesses of the strongest masers and provide a basis for explaining observed line ratios. Determination of the physical parameters in the source requires observational data in many maser transitions. In order to provide observational constraints for models we searched for and detected 7 new methanol masers. This allowed us to constrain the physical parameters of the 3 sources with the greatest number of detected methanol maser lines: W3(OH), NGC6334F, and G345.01 + 1.79. The models accurately account for the fluxes of the bulk of the detected maser lines. Remaining discrepancies most probably reflect the fact that the most prominent components of the different maser lines are formed under different conditions. This is supported by comparison of the line profiles. We outline directions for future studies in the field.
Electroluminescence (EL) characteristics of avalanching diodes fabricated by Er and O co-implantation and subsequent annealing have been studied. Distribution of Er3+-related EL at 1.538 μm was found to be uniform over the device area at 300 K. Saturation of the Er-related EL intensity is achieved under the avalanche regime at current density one order of magnitude lower than that under the tunnel regime. An EL decay is less than 10 μs (being time response of our detector) after the diode turned off the avalanche regime.
The behaviour of waste glass was investigated under open site disposal
conditions. This glass was produced by vitrification of intermediate level
radioactive waste from nuclear power plants. Two types of borosilicate
glasses were obtained for two different reactor wastes, WWER and RBM.K.
Leaching and alteration mechanisms are discussed as well as the data
processing technique used for these long term tests. The decay of
radionuclides was accounted for in order to obtain correct results. The
leaching factors obtained can be used for the assesment of radionuclide
retention. Discontinuous leaching of Cs-137 has been observed during more
than 8 years testing time. The fluctuating leaching rate depends on glass
composition. The average leaching rate remains within (0.4 – 4) μg/sq.
Alteration of waste glass includes the formation of surface layers and
cracks on the glass surface. SEM analysis of glass was used to show these
surface layers. The thickness of the layers was determined to be within 2–6
μm. The structure of these layers depends on glass composition and the
Induction melting by using a cold crucible is a suitable technology for the
immobilisation of ash residues after incineration of solid radioactive
waste. We investigated the possibility of using glass composites produced by
stirring the ash into meltedglass. Glass composites containing 15 -40 wt. %
of ash were obtained in both laboratory and bench scale units. Infrared
spectroscopy, electronic paramagnetic resonance, X-ray diffractometry, TEM
and SEM analyses were applied in order to characterise the structure of the
glass composites obtained. The glass composites consisted of a relatively
homogeneous glass matrix with embedded polycrystalline aggregates. The
fraction of aggregates increases when the fraction of ash rises. The
isothermal curing of composites at 1100 °C leads to dissolution of the ash
components into the melt as well as to their inclusion into the glass
structure, according to the analysis of the spectra obtained.
Recent results contributing to our understanding of mechanisms of defect formation and excitation of Er luminescence in Si:Er system are presented. An essential role of non-equilibrium intrinsic point defects in Er-related defects formation for both implanted and in-diffused Si:Er structures is demonstrated.
The data of electroluminescence (EL) measurements evidence that the Er3+ excitation occurs via capture of free excitons on neutral Er-related donor centers with subsequent Augerrecombination of bound excitons.
Primary mineral assemblages preserved mostly as inclusions in garnets and zircons have been found as a result of detailed investigations of diamondiferous metamorphic rocks of the Kokchetav massif, Northern Kazakhstan. Garnet and clinopyroxene are the principal minerals of these assemblages along with mica, kyanite, rutile, sphene, coesite and diamond. Estimation of the equilibration conditions using the mineral compositions shows that diamondieferous rocks were metamorphosed at temperatures not lower than 900°C. In establishing independent indicators of very high pressures (K in cpx, Al2O3 in sphene, diopside-magnesite assemblage, coesite inclusion in zircon, presence of diamond itself), all testify to the crystallization conditions of diamond in its stability field.
The Kokchetav massif is the first locality where microdiamonds were found within metamorphic rocks of the Earth's crust (Sobolev and Shatsky, 1987, 1990). Information on alluvial diamonds in Northern Kazakhstan was known long ago (Esenov et al., 1968). Two hundred fifty microdiamond grains were found during the investigation of the titanium-zircon placer samples from the northern part of the Kokchetav massif. Kashkharov and Polkanov (1972) assumed the relative closeness of the native sources, based on the preservation of very delicate, fine-grained aggregates. Rozen et al. (1972) published the data on the diamond found in the weathered crust of eclogites at the Kumdy-Kol site. Later, eclogites were considered to be the native source of alluvial diamonds for this area (Rozen et al., 1979).
The influence of the rapid thermal annealing (RTA) in comparison with that of the standard furnace annealing (FA) on the electrical parameters and photoluminescence (PL) of Czochralski silicon (Cz Si) subjected to neutron irradiation at various temperatures has been studied. The role of the irradiation temperature on the annealing behaviour of electrical parameters in Cz Si has been established. The possibility of getting neutron transmutation doped (NTD) Cz Si having the calculated resistivity by means of the RTA is shown.