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High-pressure heaters with stainless tubes were developed on the basis of previously tested technical solutions. These heaters replaced high-pressure heaters PV-150-3M with brass heat exchanger tubes in the regeneration system of the PR-12.9-2.8 (AP-25-2) turbine unit. Disadvantages of the replaced heaters, which caused their unsatisfactory thermal efficiency, thus complicating the operation of the regeneration system, are considered. The observed operational disadvantages are eliminated in the new heaters, which resulted in their higher thermal efficiency than that of the replaced ones, as confirmed by test and operation data. The example of heaters PV-150-3M demonstrates that high-pressure chamber heaters of low-power turbine units kept in operation for normal initial steam parameters can be successfully replaced with more advanced units. [ABSTRACT FROM AUTHOR]

An experimental study has been carried out to model and to measure the resonance frequency shift introduced by inserting a small microwire segment in an open resonator. A hybrid frequency synthesizer based on a Gunn diode was used to perform measurements. The open resonator was excited using this hybrid frequency synthesizer together with a Schottky diode detector used to measure a resonance curve. The results have shown a small difference between the model and the measured frequency shifts of the small microwire segment using the hybrid frequency synthesizer and the open resonator in the 3 mm wavelength band. [ABSTRACT FROM AUTHOR]

A linear operator in a locally solid vector lattice is a Lebesgue operator, if for every net in satisfying ; a -operator, if for every -bounded increasing net in there exists with ; a quasi -operator, if takes -bounded increasing nets in to -Cauchy nets; a Levi operator, if for every -bounded increasing net in there exists such that ; and a quasi Levi operator, if takes -bounded increasing nets in to -Cauchy ones. We address the domination problem for the quasi -operators and quasi Levi operators in locally solid vector lattices. Moreover, under study are some properties of Lebesgue, Levi, and -operators. In particular, we prove that the vector space of regularly Lebesgue operators is a subalgebra of the algebra of all regular operators. [ABSTRACT FROM AUTHOR]

We report eight new exoplanet candidates discovered at the Special Astrophysical Observatory of the Russian Academy of Sciences using the transit technique. Photometric observations were performed with a 50-cm robotic telescope during the second half of 2020. Transits with depths of and periods were detected in – stars. All the stars considered are dwarfs with radii (with an uncertainty of up to for a single star). We use simulations to estimate the candidate radii (all are greater than 1.4 times the Jovian radius), semi-major axes of their orbits (0.012–0.035 AU), and other orbital parameters. We report the transit light curves for two stars obtained in 2022 based on individual observations. [ABSTRACT FROM AUTHOR]

We present the results of observations within the program for the search for new highly magnetized white dwarfs among evolutionary old stars of this class. The program was carried out for two years at the 1-m telescope of the SAO RAS. As a result, new white dwarf candidates of different ages with super-strong (several megagauss, tens, hundreds of megagauss) magnetic fields were discovered. These observations, along with the observations of other authors made it possible to make a new estimate of the frequency of occurrence of magnetic white dwarfs among old stars. Our results confirm our earlier assumptions that the frequency of occurrence of far-evolved magnetic white dwarfs with magnetic fields of several megagauss or higher and with the temperatures of less than 10 000 K is at the level of 15% or higher, while the frequency of occurrence of such stars among young white dwarfs does not exceed 4–6%. This fact means that the thermal evolution of the physical properties of magnetic white dwarfs differs from the thermal evolution of their weakly magnetic counterparts. [ABSTRACT FROM AUTHOR]

We present a study of the influence of magnetically induced control of external convection in stars of different types, in particular white dwarfs, on their thermal evolution. In the work preceding this study, we argued that for the cooling down white dwarf stars that have exhausted the sources of thermonuclear combustion, cessation of convection by a magnetic field significantly slows down their cooling. To test this asertion, we performed an observational program to search for new highly magnetized white dwarfs. The program is described in detail in the same issue of the journal. Our observations, together with the observations of other researchers, allowed us to construct the observed luminosity function of strongly magnetized white dwarfs with stopped convection and compare it with the well-known similar luminosity function of white dwarfs with weak fields that allow effective convective heat removal from their insides. As a result of the model analysis of these functions, the hypothesis that strongly magnetized white dwarfs cool down slower than weakly magnetic ones is confirmed. The article also qualitatively examines the effect of magnetic braking of convection in solar-type stars and cool M-dwarf stars of the Main Sequence on the periodicity of their radiation activity. The geophysical aspect of the problem and the practical application of magnetic field control of the heat removal in electrically conductive media are discussed. [ABSTRACT FROM AUTHOR]

The design and fabrication of a single photon detector based on InP/InGaAs/InP single-photon avalanche diodes (SPADs) operating in Geiger mode at a telecommunication wavelength of 1550 nm are discussed. The SPAD design, the method for obtaining InP/InGaAs/InP heterostructures by molecular beam epitaxy, fabrication of SPAD chips using planar technology, and specific features of selective zinc doping of -regions in the InP layer of the developed electronic circuits for measuring main SPAD parameters are described. Preliminary results of measurements of the parameters of the fabricated SPADs are presented. [ABSTRACT FROM AUTHOR]

Abstract—We briefly present the history of technical solutions aimed at improving the efficiency of spectroscopy on small- and moderate-diameter telescopes. We assess the current state of spectroscopy techniques and some of the perspectives. [ABSTRACT FROM AUTHOR]

The possibility of forming a strained pseudomorphous quantum well (QW) consisting of a InxGa1 –xAsyP1 –y quaternary alloy upon the deposition of InAs onto the surface of an epitaxial GaP/Si layer with a developed relief is demonstrated. The QW is studied by means of transmission electron microscopy and steady-state photoluminescence spectroscopy. The formation of two QW segments different in width and composition of the InxGa1 –xAsyP1 –y alloy is observed; in this case, an increase in the QW width is accompanied by a decrease in the content of In and As atoms. The lateral dimensions of the QW segments are no smaller than 20 nm. The QW segments correspond to two different low-temperature photoluminescence bands. The experimentally observed phenomena are interpreted on the assumption of transformation of the surface under the action of elastic strains during heteroepitaxy of InAs on the terraced GaP surface. [ABSTRACT FROM AUTHOR]

During the self-catalyzed GaAs nanowire growth formation of parasitic GaAs crystallites is observed. The reasons for crystallite formation are explained on the base of Monte Carlo simulation results. During simultaneous deposition of gallium and arsenic on the GaAs(111)B substrate coated by a silicon oxide film, liquid gallium droplets nucleate on the oxide surface. After nucleation, droplets enlarge in size with time and etch the oxide layer. Formation of GaAs crystal structures becomes possible only after the Ga droplet contacts underlying crystal substrate. It is shown that excessively high arsenic and gallium deposition rates lead to the crystallite formation at the initial growth stage. The GaAs crystallites collect part of the deposited gallium and arsenic decreasing their surface concentration, thereby, adjusting the growth conditions for the nanowire growth. Therefore, during the self-catalyzed GaAs nanowire growth the self-regulation of growth conditions takes place. [ABSTRACT FROM AUTHOR]

GaSb films are grown by molecular-beam epitaxy using AlSb/As/Si transition layers on vicinal Si(001) substrates miscuted by 6° in (111) plane direction. The effect of GaSb films crystallographic orientation on their structural properties and surface morphology is investigated. It is found that the GaSb(00 )/Si films are characterized by better structural perfection, a lower concentration of point defects, as well as a more planar and isotropic surface morphology as compared with the GaSb(001) films. The possible cause for the observed othernesses between the GaSb films with different orientations is an increased density of antiphase domains in GaSb(001) films. The morphological features of the grown films are caused mainly by the edges of terraces and, to a lesser extent, by anisotropy of the incorporation of Ga adatoms into the edges of the terraces. [ABSTRACT FROM AUTHOR]

Abstract—The paper describes Zeiss-1000, the one meter telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS), the history of the development of its observation methods and potential areas of astrophysical research. Detailed attention is paid to instruments and methods of observation which are in service nowadays. [ABSTRACT FROM AUTHOR]

The photoluminescence spectra of waveguide AlSb/InAs/GaInSb/InAs/AlSb quantum-well heterostructures designed for the generation of radiation at interband transitions in the mid-infrared region have been studied. The experimentally detected spectral lines are correlated with calculations of the band structure. [ABSTRACT FROM AUTHOR]

In order to find an extension of Brezis–Lieb's lemma to the case of nets, we replace the almost everywhere convergence by the unbounded order convergence and introduce the pre-Brezis–Lieb property in normed lattices. Then we identify a wide class of Banach lattices in which the Brezis–Lieb lemma holds true. Among other things, it gives an extension of the Brezis–Lieb lemma for nets in L p for p ∈ [ 1 , ∞) . [ABSTRACT FROM AUTHOR]

Abstract—We report the results of laboratory tests of the first version of the high-resolution fiber-fed spectrograph designed for the Special Astrophysical Observatory of the Russian Academy of Sciences (SAO RAS). During laboratory tests a spectral resolution of about 70 000 was achieved. The peak efficiency of the entire optical path of the spectrograph (without light losses at the CCD, primary mirror of the 6-m telescope, and in the atmosphere) at 620 nm and with the equivalent slit widths of the 1″.5 and 0″.75 are equal to 8% and 4%, respectively. The resolving power R = 70 000 and 100 000 can be reached with the sky aperture 0″.75 and 0″.4 respectively. In the current version of the spectrograph these regimes of operation are implemented by mechanic aperturing of the slit. A dedicated projecting camera has been developed and is currently manufactured to operate with a collimated 200-mm diameter beam, which will make it possible to increase the spectral resolution up to 100 000. A two-beam image slicer will be used to maintain the luminous efficiency of the instrument at least at the 6% level. [ABSTRACT FROM AUTHOR]

GaAs nanowires (NWs) were generated on the surface of GaAs(111)B and GaAs(100) substrates from molecular fluxes by the self-catalytic growth method. A mask for NW growth was fabricated by oxidizing the epitaxial silicon layer that was grown on a substrate surface by the molecular beam epitaxy (MBE) method. Silicon was oxidized in purified air without moving the structures out of the vacuum system of the MBE apparatus. The process of Si/GaAs heterostructure oxidation was investigated using single-wave and spectral ellipsometry. The oxidized silicon surface morphology was studied by the atomic force microscopy methods. The scanning electronic microscopy method was used to examine the samples with NWs. The NW density was about 2.6 × 107 and 3 × 107 cm–2 for (111)B and (100), respectively. [ABSTRACT FROM AUTHOR]

Molecular-beam epitaxy is used to produce GaP/Si hybrid substrates that allow the growth of highly efficient light-emitting heterostructures with GaAs/GaP quantum wells. Despite the relatively high concentration of nonradiative-recombination centers in GaP/Si layers, GaAs/GaP quantum-well heterostructures grown on GaP/Si hybrid substrates are highly competitive in terms of efficiency and temperature stability of luminescence to similar heterostructures grown on lattice-matched GaP substrates. [ABSTRACT FROM AUTHOR]

A net xα in a lattice-normed vector lattice (X, p, E) is unbounded p-convergent to x ∈ X if p (| x α − x | ∧ u) → o 0 for every u ∈ X+. This convergence has been investigated recently for (X, p, E) = (X, |·|, X) under the name of uo-convergence, for (X, p, E) = (X, ‖·‖, ℝ) under the name of un-convergence, and also for (X , p , ℝ X ′ ) , where p(x)[f]:= |f|(|x|), under the name uaw-convergence. In this paper we study general properties of the unbounded p-convergence. [ABSTRACT FROM AUTHOR]

The effect of a substrate misorientation degree from a singular face on the composition and morphology of layers of InAsxSb1 –x solid solutions obtained by molecular-beam epitaxy on a GaAs surface has been investigated. The substrates of GaAs wafers with the orientation (100) misoriented in the direction [110] by 0°, 1°, 2°, and 5° are used. The heterostructures are grown at temperatures of 310°C and 380°C (respectively, the lower and upper boundaries of the temperature range in which structurally perfect InAsxSb1 –x films form). The effect of the molecular form of arsenic (As2 or As4) on the composition of the layers is studied. The composition and structural properties are investigated using high-resolution X-ray diffractometry (HRXRD) and atomic-force microscopy (AFM). It is established that, in the series of misorientation angles 0° → 5°, the arsenic fraction x increases consecutively when using fluxes of both As2 and As4 molecules. With the As2 molecular flux, the fraction x increases only a little (1.05 times) with increasing degree of misorientation, while, when using the As4 flux, the increase in x is 1.75 times. An increase in the growth temperature leads to growth in the arsenic fraction in the solid solution. The surface morphology improves with an increasing degree of misorientation at a low growth temperature and degrades at a high temperature. [ABSTRACT FROM AUTHOR]

Let (xα) be a net in a locally solid vector lattice (X,τ); we say that (xα) is unbounded τ-convergent to a vector x∈X if |xα-x|∧w→τ0 for all w∈X+. In this paper, we study general properties of unbounded τ-convergence (shortly uτ-convergence). uτ-convergence generalizes unbounded norm convergence and unbounded absolute weak convergence in normed lattices that have been investigated recently. We introduce uτ-topology and briefly study metrizability and completeness of this topology. [ABSTRACT FROM AUTHOR]

Several Komlós like properties in Banach lattices are investigated. We prove that C(K) fails the oo-pre-Komlós property, assuming that the compact Hausdorff space K has a nonempty separable open subset U without isolated points such that every u∈U has countable neighborhood base. We prove also that, for any infinite dimension al Banach lattice E, there is an unbounded convex uo-pre-Komlós set C⊆E+ which is not uo-Komlós. [ABSTRACT FROM AUTHOR]

Let M={mλ}λ∈Λ be a separating family of lattice seminorms on a vector lattice X, then (X,M) is called a multi-normed vector lattice (or MNVL). We write xα→mx if mλ(xα-x)→0 for all λ∈Λ. A net xα in an MNVL X=(X,M) is said to be unbounded m-convergent (or um-convergent) to x if |xα-x|∧u→m0 for all u∈X+. um-Convergence generalizes un-convergence (Deng et al. in Positivity 21:963-974, 2017; Kandić et al. in J Math Anal Appl 451:259-279, 2017) and uaw-convergence (Zabeti in Positivity, 2017. doi:10.1007/s11117-017-0524-7), and specializes up-convergence (Aydın et al. in Unbounded p-convergence in lattice-normed vector lattices. arXiv:1609.05301) and uτ-convergence (Dabboorasad et al. in uτ-Convergence in locally solid vector lattices. arXiv:1706.02006v3). um-Convergence is always topological, whose corresponding topology is called unbounded m-topology (or um-topology). We show that, for an m-complete metrizable MNVL (X,M), the um-topology is metrizable iff X has a countable topological orthogonal system. In terms of um-completeness, we present a characterization of MNVLs possessing both Lebesgue’s and Levi’s properties. Then, we characterize MNVLs possessing simultaneously the σ-Lebesgue and σ-Levi properties in terms of sequential um-completeness. Finally, we prove that every m-bounded and um-closed set is um-compact iff the space is atomic and has Lebesgue’s and Levi’s properties. [ABSTRACT FROM AUTHOR]

Low-dimensional quantum-well and nanoisland heterostructures formed in the InSb/AlAs system by molecular-beam epitaxy are studied by transmission electron microscopy and steady-state photoluminescence spectroscopy. The structures are grown under conditions of alternate In and Sb deposition (the socalled atomic-layer epitaxy mode) and the simultaneous deposition of materials (the traditional molecularbeam epitaxy mode). In both modes of growth, at a nominal amount of the deposited material in a single layer, large-sized (200 nm-1 μm) imperfect islands arranged on the InAlSbAs quantum-well layer are formed. In the heterostructures grown under conditions of atomic layer epitaxy, the islands are surrounded by ring-shaped arrays of much smaller (~10 nm), coherently strained islands consisting of the InAlSbAs alloy as well. The composition of the alloy is defined by the intermixing of Group-V materials in the stage of InSb deposition and by the intermixing of materials because of the segregation of In and Sb atoms during overgrowth of the InSb layer by an AlAs layer. [ABSTRACT FROM AUTHOR]

We investigate charge transport through the junction between a niobium superconductor and the edge of a two-dimensional electron-hole bilayer, realized in an InAs/GaSb double quantum well. For the transparent interface with a superconductor, we demonstrate that the junction resistance is determined by the interlayer charge transfer near the interface. From an analysis of experimental I−V curves, we conclude that the proximity-induced superconductivity efficiently couples electron and hole layers at low currents. The critical current demonstrates periodic dependence on the in-plane magnetic field, while it is monotonic for the field that is normal to the bilayer plane. [ABSTRACT FROM AUTHOR]

The band structure of three-layer symmetric InAs/GaSb/InAs quantum wells confined between AlSb barriers is analyzed theoretically. It is shown that, depending on the thicknesses of the InAs and GaSb layers, a normal band structure, a gapless state with a Dirac cone at the center of the Brillouin zone, or inverted band structure (two-dimensional topological insulator) can be realized in this system. Measurements of the cyclotron resonance in structures with gapless band spectra carried out for different electron concentrations confirm the existence of massless Dirac fermions in InAs/GaSb/InAs quantum wells. [ABSTRACT FROM AUTHOR]

We experimentally investigate transport through the side junction between a niobium superconductor and the mesa edge of a two-dimensional system, realized in an InAs/GaSb double quantum well with band inversion. We demonstrate, that different transport regimes can be achieved by variation of the mesa step. We observe anomalous behavior of Andreev reflection within a finite low-bias interval, which is invariant for both transport regimes. We connect this behavior with the transition from retro-(at low biases) to specular (at high ones) Andreev reflection channels in an InAs/GaSb double quantum well with band inversion. [ABSTRACT FROM AUTHOR]

The concentration distribution was studied for dissolved oxygen, phosphorus forms, and particulate matter in Curonian Bay of the Baltic Sea in poorly known consolidated ice cover conditions during the winter seasons of 2010, 2011, and 2013. The surface and near-bottom waters were sampled at 51 stations. The ice cover exerts no significant effect on the typical seasonal variation of all considered parameters in the basin. The concentrations of mineral and organic phosphorus in the bay appeared to be lower by factors of 2-4 compared to summer values. A two- to threefold decrease in the concentrations of organic phosphorus since 2010 to 2011 and then to 2013 was recorded in the bay, which resulted from a decrease in phosphorus production by phytoplankton. Despite water being isolated from air by ice, the absence of wave mixing, and the decrease in oxygen production owing to the seasonal winter decrease in the intensity photosynthetic processes, no oxygen deficiency was found in the basin. This is because oxygen supplied to the bay by river runoff and production by photosynthesis in the bay exceed the utilization for oxidation of organic matter resulting from low bioproductivity of the waters during winter. The winter decrease in the fraction of biogenic particulate matter is seen as a four- to sevenfold drop in its total concentration in the waters compared to summer seasons. The absence of wave roiling of bottom sediments also caused a decrease in the secondary supply of biogenic particulate matter from sediments into near-bottom waters. No negative trends of geoecological conditions in the bay were revealed by the studied parameters under consolidated ice cover conditions. [ABSTRACT FROM AUTHOR]

Numerical simulation based on the Princeton Ocean Model (POM) was performed for a region of the Southeast Baltic in order to compare data on the spatial distribution of velocity and bottom sediments. Special attention was focused on the influence of western and northeastern winds, which generate intense quasi-geostrophic currents can may cause very high velocities in the near bottom layer, which results in the elution of bottom sediments and transport of their fine fractions. An abrupt change in wind velocity intensifies the effect of elution due to generation of inertial internal waves that penetrate into the bottom layer. The spatial distributions of the velocity in the surface and near bottom layers are compared with data on bottom sediments. It turned out that areas with the highest velocities that formed under the effect of western and northeastern winds in most cases coincide with areas where bottom sediments are represented by coarse-grain fractions of gravel and sands. [ABSTRACT FROM AUTHOR]

This paper presents reconstructions of ice sheet boundaries, lacustrine and marine paleobasins, as well as the connections of the Barents and Baltic seas with the North Atlantic from the Last Glacial Maximum to the Holocene. The reconstructions are based on original and published data obtained from the northern and western parts of the Barents Sea and Baltic depressions with account for the available regional schematic maps of deglaciation. The early deglaciation of the Scandinavian-Barents ice sheet culminated with the Bølling-Allerød interstadial (14.5-12.9 cal ka BP), which was characterized by a more vigorous Atlantic meridional overturning circulation (AMOC) and a corresponding increase in surface Atlantic water inflow into the Barents Sea through deep troughs. The Baltic Ice Lake (BIL) remained a dammed-up isolated basin during deglaciation from 16.0 to 11.7 cal ka BP. In the Younger Dryas (YD), the lake drained into the North Sea and was replaced by a brackish Yoldia Sea (YS) at the beginning of the Holocene (Preboreal, 11.7-10.7 cal ka BP), due to a limited connection between two basins through the Närke Strait. In the Barents Sea, the next increase in the Atlantic water influx into the deep basins corresponded to terminal YD and Preboreal events with a culmination in the Early Holocene. The Yoldia Sea became a lake again during the next stage, the Ancylus (~10.7-8.8 cal ka BP). Atlantic water inflow both into the Barents and Baltic seas varied during the Holocene, with a maximum contribution in the Early Holocene, when the Littorina Sea (LS, 8-4 cal ka BP) connection with the North Sea via the Danish Straits was formed to replace the Ancylus Lake. The recent, post-Littorina stage (PS, the last 4 cal ka) of the Baltic Sea evolution began in the Late Holocene. [ABSTRACT FROM AUTHOR]

The atomic structure of GaSb/GaP quantum dots grown via molecular beam epitaxy on a (100) GaP surface at epitaxy temperatures of 420-470°C is investigated. It is established that, depending on morphology of the GaP growth surface, the deposition of 1 ML of GaSb leads to the formation of strained Ga(Sb, P)/GaP or fully relaxed GaSb/GaP quantum dots. The obtained heterostructures exhibit high photoluminescence efficiency. [ABSTRACT FROM AUTHOR]

The effect of substrate temperature, As and P molecular flux densities, and growth rate on the composition of III-PAs solid solution layers prepared by molecular beam epitaxy is experimentally investigated. Experimental data in a wide range of growth conditions are analyzed. The results obtained are presented in the form of a kinetic model for describing the process of formation of the composition in the Group V sublattice of the III-PAs solid solution upon molecular beam epitaxy. The model can be used for choosing the growth conditions of the III-PAs (001) solid-solution layers of a specified composition. [ABSTRACT FROM AUTHOR]

GaAs films on Si substrates miscut from the (001) plane by 6° in the [110] direction are grown by molecular beam epitaxy (MBE). GaAs films are grown both on the Si surface terminated by arsenic atoms and on thin pseudomorphic GaP/Si layers. The condition of formation of the As sublayer and the first monolayer of GaP on the Si surface is defined as the GaAs film orientation (001) or $(00\bar 1)$. The processes of Si surface preparation and formation of the As sublayer and GaAs and GaP epitaxial layers are monitored by means of high-energy electron diffraction reflection (RHEED). The grown structures are investigated by methods of X-ray diffraction, atomic force microscopy (ATM), high-resolution transmission electron microscopy (HRTEM), and low-temperature luminescences. It is shown that the epitaxial film orientation affects both the surface morphology and its crystalline properties. Intense photoluminescence is obtained from the InGaAs quantum well structure grown on the GaAs/Si buffer layer. [ABSTRACT FROM AUTHOR]

Monitoring studies in the area of Kravtsovskoe oil field in the southeastern Baltic Sea have been carried out since 2003. Terrigenous bottom sediments (0-5 cm layer) in the area (23 stations) are represented by all grain size types. Down to the depth of 30-50 m, these are mostly quartz sands; at depths of 60-110 m, these are terrigenous mud with C content of 1-3%. The concentration and distribution of toxic elements (Cu, Co, Cd, Pb, Ba, and Hg) over sediment types and bed area are the same as in the Baltic Sea as a whole: Cu, Co, Cd, Pb, and, partially, Hg are distributed in accordance with the 'fraction rules' (with minimums in sands and coarse aleurites and maximums in mud); Ba distribution is independent of the sediment type. The concentrations of toxic elements tend to increase with time: the concentrations of such elements in samples (at the same stations) somewhat increase compared with their concentrations before the construction of D-6 oil platform, during its construction, and during oil production. This trend in the concentrations of toxic elements in sediments can be due to the steelwork of D-6 platform. The increase in Ba concentration is likely due to drill mud spills during exploration drilling. None of the elements shows sediment pollution in excess of MAC anywhere in the area. [ABSTRACT FROM AUTHOR]

Using the method of molecular-beam epitaxy, GaAs films are grown on Si substrates tilted from the (001) plane by 6° to the [110] direction. The GaAs films are grown both on Si surfaces terminated by arsenic atoms and on pseudo-morphic GaP/Si layers. The layers of GaAs are nucleated by the method of atomic-layer epitaxy at low temperatures. The resulting structures are found to differ in crystallographic orientation of the GaAs film with respect to the film tilt direction. The structures thus grown are examined by the methods of x-ray diffraction analysis and atomic force microscopy. [ABSTRACT FROM AUTHOR]

Core Psd-590 (length 947 cm, water depth 124 m) penetrated the entire sequence of marine (Littorina) mud (730 cm) and stopped in gray lacustrine (Ancylus) clays with hydrotroilitic films. The Littorina mud is gray-colored, microlaminated in the interval of 730 to 700 cm, and dark gray with hydrotoilitic films and obscure microlamination higher in the section. According to the diatom data, typical marine sediments begin at the level of 620 cm, while the lithological-geochemical data indicate this change at the level of 730 cm. This level is marked by a considerable increase in the concentrations of SiO, CO, C, and Mn in the sediments. In the interval of 730 to 620 cm, diatoms are represented by both freshwater and brackish-water species. The Littorina transgression began in the form of individual flows of saline North Sea waters into the Baltic Sea, which is evident from the microlamination and sharp peaks in the concentrations of the chemical elements. The transgression exhibits two weakening and one strengthening (core interval of 380 to 220 cm) stages; the latter was marked by the maximal water salinity. The post-Littorina mud contains molluscan shells and fish bones and is enriched in the fraction of 0.05-0.01 mm. The microlaminated Littorina mud was deposited during periods with stagnant conditions in the bottom water layer, while the homogenous sediments accumulated during periods of its aeration. [ABSTRACT FROM AUTHOR]

In depressions of the Baltic Sea, where the bottom is periodically marked by stagnation, silt contains as much as 5% Mn (up to 17% in some layers) and 9-10% C. Silt in such depressions is laminated. The marine sediment sequence is stratified due to the influx of oceanic water into sea: the upper layers are oxic, while the lower (near-bottom) layers are hydrosulfuric. Boundary between them is represented by the transitional O-HS layer. This zone (redox barrier) is marked by drastic variation in Eh. Zone below this barrier is characterized by the accumulation of huge amounts of the dissolved manganese (Mn) and iron (Fe), which diffuse from the hydrosulfuric layer into the oxic layer under the influence of gradient and precipitated as suspeusion with as much as 15% Fe and 45% Mn. When fresh oxygenated saline water is transported to depressions, the hydrosulfuric setting gives way to oxic one and the dissolved elements are transformed into the particulate phases as hydroxides and geologically instantly precipitated at the bottom. After 5-10 yr, the setting changes; hydrogen sulfide is again delivered to water column from the bottom. This is accompanied by supply of the dissolved Mn and Fe previously accumulated as gel-type sediment at the bottom. Thus, the cycle of elements is repeated. The latter, however, is not completely dissolved. Some portion remains at the bottom as black rhodochrosite microlayers (laminas) that contain as much as 29% Mn. The black laminas accumulated during aeration include remains of bottom foraminifers. In addition, the bottom comprises pale diatom laminas and brownish gray varieties composed of clayey and organic substances. Bulk samples of the laminated silt contain as much as 12.9% Mn or 26.9% MnCO. Depressions in the Baltic Sea represent a unique site of the Earth marked by accumulation of the carbonate-manganiferous sediments at present. We believe that Oligocene manganese carbonate-oxide ores described by N.M. Strakhov and coauthors were accumulated in the same manner. Compositions of manganiferous sediments in the Baltic region and some ancient ores in Europe are compared. The author studied five stages of Mn accumulation and sediment transformation into ores. [ABSTRACT FROM AUTHOR]

Core MD02-2508 retrieved from the plateau of the continental slope off Baja California recovered a 40-m-thick section of sapropel (up to 15% Corg), calcareous clay, and diatom ooze with the age of 120 ka at the core bottom. The section is subdivided into three units: Unit I (Holocene) consists of the laminated sapropel; Unit II comprising oxygen isotope stages (MIS) 2, 3, and 4 is represented by homogeneous calcareous clay with interbeds of slightly siliceous sapropelic mud; and Unit III (MIS-5) is composed of laminated sapropelic diatom ooze. Laminated intervals are characterized by the intercalation of two lamina types: (1) dark-colored organic-rich laminae containing multi-species “oceanic” diatom assemblages, as well as radiolarians, coccoliths, planktonic and benthic foraminifera; (2) lighter-colored laminae consisting of diatom ooze with the neritic colonial diatom assemblages commonly composed of one to three species of a single genera. The dark laminae are assumed to be generated within a high productivity zone over the slope, whereas light ones likely represent diatom mats produced by short-term boisterous phytoplankton blooms, possibly in the coastal upwelling. [ABSTRACT FROM AUTHOR]

The grain-size and chemical composition of the bottom sediments and their diatom assemblages from the northern Baltic Sea is discussed. Characteristic layers are distinguished based on the lithostratgraphy and sediment core correlation, which reflect the transition from the lacustrine to marine sedimentation settings during the initial Holocene. Sediment cores demonstrate lateral variations in the sedimentation patterns during the marine (Yoldia Sea), the lacustrine (Ancylus Lake), and the subsequent marine (Littorina Sea) stages: first two stages were characterized by the clay deposition, while the latter one featured accumulation of silty-clayey and clayey muds in bottom depressions. Sea-level fluctuations and corresponding environmental changes are recorded in microlaminated sequences, in particular, sapropelic muds. [ABSTRACT FROM AUTHOR]

As is less toxic than Hg, Cd, Pb, Se, Zn, and Cu. The As clarke for clays and shales is 10 ppm. Our samples of bottom sediments from Kurshskii Bay were determined to contain from 15 to 26 ppm As and up to 34 ppm As in the vicinity of the Neman River mouth. Elevated As concentrations (50–114 ppm) were detected in four columns of subsurface bottom sediments (at depths of 10–65 cm) from the Vistula Lagoon. Elevated As concentrations (50–180 ppm) were also found in a few surface samples of sand from the Gdansk Deep near oil platform D-6. These sediments are either partly contaminated with anthropogenic As or contain Fe sulfides and glauconite, which can concentrate As and contain its elevated concentrations. The As concentration in columns of bottom sediments from the Gulf of Finland were at the natural background level (throughout the columns) typical of the area (9–34 ppm). We repeatedly detected very high As concentrations (up to 227 ppm As) in pelitic ooze from Bornholm Deep, in the vicinity of the sunken vessel with chemical weapons. The sources of elevated As concentrations in the Baltic Sea are the following: (1) chemical weapon (CW) material buried in the floor of the Baltic Sea; (2) As-bearing pesticides, agricultural mineral fertilizers, and burned coal and other fuels; (3) kerogen-bearing Ordovician rocks exposed on the bottom; and (4) As-rich Fe sulfides brought to the area together with construction sand and gravel. This mixture was used in paper production and for the construction of hydraulic engineering facilities in the Vistula Lagoon in the early 20th century and later caused the so-called lagoon disease. [ABSTRACT FROM AUTHOR]

A sharp estimate of the product ... Rαk² (Dk, bk) (as usual, R(D, b) denotes the conformal radius of a domain D with respect to a point b ∈ D) in the family of all quadruples of nonoverlapping simply connected domains {Dk}, bk ∈ Dk, k = 1,...,4, is obtained. Here, {b1,...,b4} are four arbitrary distinct points on &Cmacr;, α1 α2 = 1, α3 = α4 = α and α is an arbitrary positive number. The proof involves the solution of the problem on maximizing a certain conformal invariant, which is related to the problem under consideration. Bibliography: 5 titles. [ABSTRACT FROM AUTHOR]

Let ℜ be a finite Riemann surface. For a quadratic differential on ℜ associated with a certain problem on extremal decomposition of ℜ into n domains, a parametric family of quasiconformal mappings fΚ : ℜ → ℜΚ K = (k1,...,ks), ki ∈ C. is defined. These mappings map the domains of the extremal decomposition of ℜ onto the domains of the extremal decomposition of ℜΚ. This allows one to study the functional dependence of the problem on the parameters. Bibliography: 6 titles. [ABSTRACT FROM AUTHOR]

Geological and seismic profiling data (more than 25000 km of seismic profiles and about 1000 sediment sampling stations) collected during the last 30 yr by research vessels of the Shirshov Institute of Oceanology, Russian Academy of Sciences are summarized. Seismic records are directly correlated with sediment cores. The distribution map (scale 1 : 500000) of Quaternary lithofacial complexes corresponding to certain stages of the Baltic Sea evolution is compiled. The following four complexes are distinguished (from the base to the top): (I) moraine, with maximum thicknesses 60 and 170 m in valleys and ridges respectively: (II) varved clay of periglacial basins and from the Baltic Ice Lake (BIL), up to 25 m thick in depressions; (III) lacustrinemarine homogeneous clay with a thickness up to 4–8 m in depressions; (IV) marine sediments (mud, aleurite, coarse-grained deposits) accumulated in environments with intense bottom currents activity (thickness 2–4 m in the Gotland Basin, 4–6 m in the Gdansk Basin, and 10–20 m in fans and prodeltas). The Quaternary sequence is cut through by inherited valleys, where the thickest Holocene sediments are noted. Today, these valleys serve as routes of sediment transport to slope bases and central parts of basins. Outblows of deep gas (through faults and fractures) and diagenetic gas (from sediments) to the bottom surface also occur in the valleys. Sedimentation rates are higher in the Gdansk Basin (up to 100–120 cm/ka). Thick sand, aleurite, and mud bodies are accumulated here (about 15–20 m in the Visla River prodelta). The sedimentation rate is slower in the Gotland Basin (up to 50–60 cm/ka), where thin (2–4 m) sections of more fine-grained mud occur [ABSTRACT FROM AUTHOR]