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GravityCam is a new concept of ground-based imaging instrument capable of delivering significantly sharper images from the ground than is normally possible without adaptive optics. Advances in optical and near-infrared imaging technologies allow images to be acquired at high speed without significant noise penalty. Aligning these images before they are combined can yield a 2.5–3-fold improvement in image resolution. By using arrays of such detectors, survey fields may be as wide as the telescope optics allows. Consequently, GravityCam enables both wide-field high-resolution imaging and high-speed photometry. We describe the instrument and detail its application to provide demographics of planets and satellites down to Lunar mass (or even below) across the Milky Way. GravityCam is also suited to improve the quality of weak shear studies of dark matter distribution in distant clusters of galaxies and multiwavelength follow-ups of background sources that are strongly lensed by galaxy clusters. The photometric data arising from an extensive microlensing survey will also be useful for asteroseismology studies, while GravityCam can be used to monitor fast multiwavelength flaring in accreting compact objects and promises to generate a unique data set on the population of the Kuiper belt and possibly the Oort cloud.
Short pulse laser irradiation has the ability to bring a material into a state of strong electronic, thermal, phase, and mechanical nonequilibrium and trigger a sequence of structural transformations leading to the generation of complex multiscale surface morphologies, unusual metastable phases, and microstructures that cannot be produced by any other means. In this article, we provide an overview of recent advancements and existing challenges in the understanding of the fundamental mechanisms of short pulse laser interaction with materials, including the material response to strong electronic excitation, ultrafast redistribution and partitioning of the deposited laser energy, the peculiarities of phase transformations occurring under conditions of strong superheating/undercooling, as well as laser-induced generation of crystal defects and modification of surface microstructure.
The Pirot sheep is a small Zackel that has been developed in the region of Pirot and the neighbouring municipalities in Serbia. Pirot sheep population has been reduced to only 60 animals in the Republic of Serbia. An overview of qualitative phenotypical and morphometrical characteristics of Pirot sheep from the Stara Planina is presented in this paper. The sheep included in this study belong to the last flock of the breed. The evaluation aims to obtain the phenotypical description of this indigenous breed as a phase of preservation strategy. Therefore, a total of 51 ewes and two rams were measured to obtain the detailed data concerning conformation. The phenotypical characteristics of animals included were also described. Based on the results, the Pirot sheep is a small breed with compact, slightly rectangular body frame (body length 115.40 percent of height at withers). The investigated sheep population was homogeneous, and morphological variations were limited to the data obtained in our research. The differences detected among different age groups were significant and reflected late maturing and slow growth of individuals. The comparison of the data determined by the evaluation of the modern population of Pirot sheep with the description from the older literature did not reveal that many significant changes of the morphological characteristics have occurred during the last 30 years. The small effective population and increasing inbreeding can threaten the efforts to preserve this sheep. The cultural heritage of the local community is also in danger due to the fact that the cornerstones of rural tradition in the area have been production of the three nationally important agricultural brands in Serbia – Pirot kilim (Pirot rug), Pirot/Stara Planina lamb and Pirot/Stara Planina Kachkaval cheese, all of which are depending on the Pirot sheep breeding. Additionally, some problems affecting the preservation of animal genetic resources in Serbia are reviewed with the focus on the Stara Planina. The research indicated that ex situ conservation should also be considered in the case of the Pirot sheep.
Here we report ongoing efforts for an untriggered search of rapid optical transients of various astrophysical and non-astrophysical origins on time scales down to fractions of a second with Mini-MegaTORTORA. Mini-MegaTORTORA is a novel 9-channel wide-field optical monitoring system in operation since 2014 at Special Astrophysical Observatory on Russian Caucasus.
This paper is devoted to an experimental investigation of receptivity of a laminar swept-wing boundary layer due to scattering of free-stream vortices on localized (in the streamwise direction) surface vibrations. The experiments were conducted under completely controlled disturbance conditions by means of a hot-wire anemometer on a model of a swept wing with a sweep angle of 25°. Both the free-stream vortices and the surface vibrations were generated by disturbance sources; their frequency–wavenumber spectra were measured thoroughly. The free-stream vorticity vectors were directed perpendicular to the incident-flow velocity vector and parallel to the swept-wing-model surface. The linearity of the receptivity mechanism under investigation (in a sense that the corresponding receptivity coefficients are independent of the disturbances amplitudes) has been checked carefully. The main goal of this experiment was to estimate the vibration-vortex receptivity coefficients as functions of the disturbance frequency, spanwise wavenumber and vortex offset parameter. This goal has been attained. Being defined in Fourier space, the obtained receptivity coefficients are independent of the specific surface vibration shape and can be used for verification of various receptivity theories.
AlGaN-based quantum well (QW) heterostructures grown by plasma-assisted molecular beam epitaxy on c-Al2O3 substrates have been studied. The high-temperature (785 °C) synthesis of AlN buffer layer nucleated by a migration-enhanced epitaxy and including several ultrathin GaN interlayers was the optimum approach for lowering the threading dislocations density down to 108–109 cm−2. High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) has revealed the step-like roughness of the AlN/Al2O3 interface. Also, the formation of Al-rich barriers induced by temperature-modulated epitaxy and the spontaneous compositional disordering have been found in the AlxGa1−xN (x > 0.6) barrier layers. The origin of these phenomena and their influence on parameters of the mid-UV stimulated emission observed in the QW heterostructures were discussed. The fine structure of the QWs formed by a submonolayer digital alloying technique has been displayed by HAADF STEM, and optical properties of the QW structures were studied by temperature- and time-dependent photoluminescence spectroscopy.
We conducted infrared spectroscopic observations of bright stars in the direction of the molecular clouds W33 and GMC G23.3 − 0.3. We compared stellar spectro-photometric distances with parallactic distances to these regions, and we were able to assess the association of the detected massive stars with these molecular complexes. The spatial and temporal distributions of the detected stars enabled us to locate sources of ionizing radiation and to gather precise information on the star formation history of these clouds. The studied clouds present different distributions of massive stars.
This report summarizes epidemiological data on nephropathia epidemica (NE) in the Republic of Tatarstan, Russia. NE cases identified in the period 1997–2013 were investigated in parallel with the hantavirus antigen prevalence in small rodents in the study area. A total of 13 930 NE cases were documented in all but one district of Tatarstan, with most cases located in the central and southeastern districts. The NE annual incidence rate exhibited a cyclical pattern, with the highest numbers of cases being registered once in every 3–5 years. The numbers of NE cases rose gradually from July to November, with the highest morbidity in adult males. The highest annual disease incidence rate, 64·4 cases/100 000 population, was observed in 1997, with a total of 2431 NE cases registered. NE cases were mostly associated with visiting forests and agricultural activities. The analysis revealed that the bank vole Myodes glareolus not only comprises the majority of the small rodent communities in the region, but also consistently displays the highest hantavirus prevalence compared to other small rodent species.
AlGaN-based SQW heterostructures grown by plasma-assisted molecular beam epitaxy on c-Al2O3 substrates have been studied with high resolution transmission electron microscopy (HR TEM), photoluminescence spectroscopy and x-ray diffraction. The high-temperature (780°C) synthesis of the AlN buffer layer nucleated on c-Al2O3 by a migration enhanced epitaxy and including several ultra-thin GaN interlayers grown under moderate N-rich conditions was shown to be the optimum approach for lowering the threading dislocations density down to 108-109 cm-2. HR TEM study has confirmed the fine structure of single quantum wells (SQW) formed by a sub-monolayer digital alloying technique and revealed different kinds of compositional inhomogeneities in the AlxGa1-xN barrier layers of the heterostructures, including the formation of Al-rich barriers induced by the temperature-modulated epitaxy and the spontaneous compositional disordering along the growth axis for x=0.6-0.7. The influence of these phenomena on the parameters of the mid-UV stimulated emission observed in the SQW structures has been studied as well.
Nontrivial pairs of zero-divisors in group rings are introduced and discussed. A problem on the existence of nontrivial pairs of zero-divisors in group rings of free Burnside groups of odd exponent
is solved in the affirmative. Nontrivial pairs of zero-divisors are also found in group rings of free products of groups with torsion.
In this work we propose a method for analysis of postsurgical haemodynamics after femoral
artery treatment of occlusive vascular disease. Patient specific reconstruction algorithm
of 1D core network based on MRI data is proposed as a tool for such analysis. Along with
presurgical ultrasound data fitting it provides effective personalizing predictive method
that is validated with clinical observations.
We prove the CR version of the Obata's result for the first eigenvalue of the sub-Laplacian in the setting of a compact strictly pseudoconvex pseudohermitian three-dimensional manifold with non-negative CR-Paneitz operator which satisfies a Lichnerowicz-type condition. We show that if the first positive eigenvalue of the sub-Laplacian takes the smallest possible value, then, up to a homothety of the pseudohermitian structure, the manifold is the standard Sasakian three-dimensional unit sphere.
The present experimental study is devoted to examination of the vortex receptivity mechanism associated with excitation of unsteady cross-flow (CF) waves due to scattering of unsteady free-stream vortices on localized steady surface non-uniformities (roughness). The measurements are carried out in a low-turbulence wind tunnel by means of a hot-wire anemometer in a boundary layer developing over a
swept-wing model. The harmonic-in-time free-stream vortices were excited by a thin vibrating wire located upstream of the experimental-model leading edge and represented a kind of small-amplitude von Kármán vortex street with spanwise orientation of the generated instantaneous vorticity vectors. The controlled roughness elements (the so-called ‘phased roughness’) were placed on the model surface. This roughness had a special shape, which provided excitation of CF-waves having basically some predetermined (required) spanwise wavenumbers. The linearity of the stability and receptivity mechanisms under study was checked accurately by means of variation of both the free-stream-vortex amplitude and the surface roughness height. These experiments were directed to obtaining the amplitudes and phases of the vortex-roughness receptivity coefficients for a number of vortex disturbance frequencies. The vortex street position with respect to the model surface (the vortex offset parameter) was also varied. The receptivity characteristics obtained experimentally in Fourier space are independent of the particular roughness shape, and can be used for validation of receptivity theories.
Synergistic compositions of detonation nanodiamond (ND) particles in the form of 100nm aggregates in combination with molybdenum dialkyldithiophosphate were used as additives to 10W40 oils. Ring-on-disk tribological tests were performed under high load conditions using friction pairs with different hardnesses, namely normalized-normalized (“soft/soft”) and normalized-quenched (“soft/hard”) steel samples. For the “soft/hard” steel friction pair NDs provide significant reduction in both the coefficient of friction and wear as well as demonstrate polishing. For the “soft/soft” steel friction pair, however, no difference in the coefficients of friction was observed when the base oil was used with or without ND. In the test with oil containing the ND additive, the wear scar in the disk was wider, but more shallow, than in the test with pure oil. Current tests indicate that the significance of the reduction of friction and wear of the sliding surfaces in the presence of the ND additive in oil strongly depends on the hardness of the friction surfaces and most probably is connected with ND polishing effect.
Here we briefly summarize our long period experience of constructing and operating
wide-field monitoring cameras with sub-second temporal resolution to look for optical
components of GRBs, fast-moving satellites and meteors. General requirements for hardware
for such systems are discussed along with algorithms of real-time detection and
classification of various kinds of short optical transients. We also give a status report
on the next generation, multi-objective and transforming monitoring system, the
MegaTORTORA, whose 6-channel (Mini-MegaTORTORA-Spain) and 9-channel
prototypes (Mini-MegaTORTORA-Kazan) we are building now at SAO RAS. This system combines a
wide field of view with subsecond temporal resolution in monitoring regime, and is able to
reconfigure itself, in a fractions of second, to follow-up mode which has better
sensitivity and provides us with multi-color and polarimetric information on detected
This paper is concerned with a non-homogeneous in space and non-local in time random walk
model for anomalous subdiffusive transport of cells. Starting with a Markov model
involving a structured probability density function, we derive the non-local in time
master equation and fractional equation for the probability of cell position. We derive
the fractional Fokker-Planck equation for the density of cells and apply this equation to
the anomalous chemotaxis problem. We show the structural instability of fractional
subdiffusive equation with respect to the partial variations of anomalous exponent. We
find the criteria under which the anomalous aggregation of cells takes place in the