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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.
Doppler-effect laser equipment was successfully employed in Antarctica in 1969-70 to measure the rate of ice-sheet motion. The method is based on measuring differential beat frequency generated by the interaction of the direct pulse and its echo. A He-Ne laser with the wavelength of 6 328 Â was used in the 15th Soviet Antarctic Expedition. The paper gives detailed results of the measurements along with a description of the equipment used and of the observational procedures. A new modified version of the equipment was made ready for 1971-72 Antarctic season, and was used in the 18th Soviet Antarctic Expedition in the vicinity of Mirny station. New results are also discussed. Analysis of all available data makes it possible to believe that the movement of the ice sheet is irregular with occasional stops. The progressive motion of the ice sheet is accompanied by strain oscillations.
Die Gasentladung im Deuterium bei Stromstärken bis zu 700 tausend Ampere im magnetischen Längsfelde bis zu 12000 Oersted wurde untersucht. Die Einwirkung des Feldes auf den Verlauf der Entladung wurde festgestellt und eine Zunahme des Magnetfeldes im Innern der Entladungssäule entdeckt. Eine Bewertung der Plasmaleitfähigkeit und der Ionisierungszahl wird gegeben.
Studies of chemical composition of the atmospheres of F-K supergiants have revealed the existence of two specific peculiarities, deficit of carbon and excess of nitrogen. Anomalous abundances of C and N in yellow supergiants is explained by mixing of surface material with CNO-processed material of stellar interiors (the first dredge-up). Somewhat unexpectedly, F-K supergiants were found to show one more general chemical peculiarity: overabundance of sodium. Fig.1 shows the available values of [Na/H]=log[N(Na)/N(H)]*−log[N(Na)/N(H)]⊙ as summarized by Boyarchuk and Lyubimkov( 1983). Different symbols refer to data of various authors. Fig.1 shows that sodium overabundance increases with the decrease of surface gravity. For small log g it reaches [Na/H] ~ ~ 1. Recently Sasselov(1986) has suggested that this correlation is essentially a consequence of a relation between [Na/H] and a mass of supergiant.
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.
Geological disposal (GD) of radioactive waste is close to becoming a reality for Finland, Sweden and France. High-technology development and advanced knowledge has made it possible to defend the feasibility and the safety of such facilities, making the European Union a leader in the field. Other European countries are closely behind, developing high competence through advanced research programmes, research infrastructures and public engagement.
At the other extreme, there are countries whose GD programmes are at an early stage and no systematic research programmes exist. These include several new Member States but not the Czech Republic and Hungary, both of which have already initiated a siting process.
There are several common reasons for this delay in schedule: small and relatively younger nuclear energy programmes, return of the spent fuel (especially from research reactors) to the countries of origin, open fuel cycle concept (requiring at least 50 years of wet and dry storage). In this context, there has been little pressure on setting up an early GD programme. Currently their disposal concepts are only generic and in most of these countries need updating, taking into account the current socio-economic context.
However, some of these new Member States still aim to have a GD in operation within several decades, e.g. 2055 in Romania and 2067 in Slovenia. Strategic planning based on the experience of more advanced programmes shows the GD process should start immediately in order to be able to achieve these deadlines.
In this context, the implementation of the EC Directive 70/2011 gives the opportunity to progress the advancement of the GD process in these countries.
It is well known that the turbulent state of the atmosphere gives rise to fluctuations of the coefficient of light refraction. In astrometric observations these fluctuations produce the phenomenon of image motion which serves as the source of accidental errors of observations. The need for the study of the effect of atmospheric turbulence is documented in (G.Teleki, 1967) and others.
A plasma target for highly efficient neutralization of powerful negative ion beams is considered. The plasma is confined within a magnetic trap with multipole magnetic walls. It is proposed to use inverse magnetic mirrors to limit plasma outflow through the inlet and outlet holes in the trap. Using the particle-in-cell method, mathematical simulation of plasma dynamics in the trap has been performed. The estimates of plasma distribution and particle confinement efficiency in the region of the magnetic mirrors has been obtained. Simulation results were compared with experimental data.
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.
Optical properties of the GaNxAs1−x layers grown on (001) GaAs substrates by molecular beam epitaxy have been studied. The samples can be classified into three categories with respect to the concentration of N, as determined by x-ray diffraction and secondary-ion mass spectrometry: (i) with doping nitrogen concentration, (ii) with average content of N less than 30 %, and (iii) with x close to 100 %. From optical measurements of photoluminescence and Raman scattering, combined with analysis of x-ray diffraction spectra, different phases are observed in the GaNxAs1−x layers: GaAs, GaN and the solid ternary solution GaNxAs1−x. We have estimated the fundamental band-gap energy in the GaNxAs1−x alloy with low nitrogen concentration (up to x = 0.04) from absorption measurements, and in GaNxAs1−x with low arsenic concentration (up to 1−x = 0.04) - from photoluminescence spectra. An analysis of the dependence of the experimental values of the GaNxAs1−x band-gap energy on the nitrogen composition indicates a constant bowing parameter b as large as b = -18 eV.
The Magellanic System represents one of the best places to study the formation and evolution of galaxies. Photometric surveys of various depths, areas and wavelengths have had a significant impact on our understanding of the system; however, a complete picture is still lacking. VMC (the VISTA near-infrared YJKs survey of the Magellanic System) will provide new data to derive the spatially resolved star formation history and to construct a three-dimensional map of the system. These data combined with those from other ongoing and planned surveys will give us an absolutely unique view of the system opening up the doors to truly new science!
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.
Recent years have witnessed a remarkable progress in high-power short laser pulse generation. Modern conventional and free-electron laser (FEL) systems provide peak light intensities of the order of 1020 W cm−2 or above in pulses in femtosecond and sub-femtosecond regimes. The field strength at these intensities is a hundred times the Coulomb field, binding the ground-state electron in the hydrogen atom. These extreme photon densities allow highly non-linear multiphoton processes, such as above-threshold ionization (ATI), high harmonic generation (HHG), laser-induced tunneling, multiple ionization and others, where up to a few hundred photons can be absorbed from the laser field. In parallel with these experimental developments, massive efforts have been undertaken to unveil the precise physical mechanisms behind multiphoton ionization (MPI) and other strong-field ionization phenomena. It was shown convincingly that multiple ionization of atoms by an ultrashort intense laser pulse is a process in which the highly non-linear interaction between the electrons and the external field is closely interrelated with the fewbody correlated dynamics . A theoretical description of such processes requires development of new theoretical methods to simultaneously account for the field nonlinearity and the long-ranged Coulomb interaction between the particles.
In this chapter, we review our recent theoretical work in which we develop explicitly time-dependent, non-perturbative methods to treat MPI processes in many-electron atoms. These methods are based on numerical solution of the time-dependent Schrödinger equation (TDSE) for a target atom or molecule in the presence of an electromagnetic and/or static electric field. Projecting this solution onto final field-free target states gives us probabilities and cross sections for various ionization channels.
More than 20000 observations of Near Earth asteroids and comets are collected and reduced in Pulkovo Observatory during last 10 years. For observations of these objects two robotic telescopes are used – ZA-320M (Cassegrain system, D = 320 mm, F = 3200 mm) at Pulkovo and MTM-500M (Maksutov – Cassegrain system, D = 500 mm, F = 4100 mm) at Kislovodsk mountain station. These telescopes perform CCD observations of objects up to 18.0 and 20.5 magnitude, correspondingly. The results of observations are regularly submitted to Minor Planet Center.
Continuous decrease of the feature size of transistors in modern integrated circuits (ICs) constrains thickness of auxiliary dielectric layers in interconnects because of their relatively high dielectric constant, which reduces the efficiency of low-k material integration. Dielectric materials used today as barrier or etch-stop layers are usually SiN (k ∼ 7.0) and SiCN (k ∼ 4.8), which k-value significantly exceeds that of recent ultra low-k materials (k < 2.2). In our work we have investigated thin films of rigid-chain polyimide (PI) with a k-value of about 3.2-3.3. This film was deposited using a Langmuir-Blodgett (LB) technique and can be as thin as several monolayers. The intermolecular interaction of densely packed precursor macromolecules within a monolayer formed at the water-air interface makes it possible to avoid penetration of precursor material inside the pores. The latter peculiarity of the deposition process results in a pore sealing effect using a 4 nm PI film.
The well-known recurrent nova T Pyx has brightened by 7 magnitudes, starting on 2011 April 14, its first eruption since 1966. T Pyx is unique amongst recurrent novæ in being surrounded by a nebula formed of material ejected during previous eruptions. The latest eruption therefore offers the rare opportunity to observe a light echo sweeping through the existing shell, and a new one forming. The sudden exposure of the existing shell to high-energy light is expected to result in a change of the dust morphology as well as in the part destruction of molecules. We observe this process in the near- and mid-IR during several epochs using ESO's VLT instruments Sinfoni, Visir and Isaac. Unfortunately, in the data analysed so far we only have a tentative detection in Brα from the shell, so might in the end have to be content with upper limits for the emission from the various molecular bands and ionised lines.
The environmental effects on galaxy evolution have recently been disputed based on large SDSS galaxy samples but these effects are still expected to be strong for low-mass galaxies. We obtained deep near-infrared imaging of irregular dwarfs in Cen A, M 81 and Sculptor groups – spanning a range of galaxy density, – and we study the properties of these dwarfs, i.e. abundance, chemical evolution, and structural parameters. Here we give a preliminary assessment of the structural parameters for these galaxies.
We examine the association of a venture capital (VC) firm’s reputation with the post-initial public offering (IPO) long-run performance of its portfolio firms. We find that VC reputation, measured by the past market share of VC-backed IPOs, has significant positive associations with long-run firm performance measures. While more reputable VCs initially select better-quality firms, more reputable VCs continue to be associated with superior long-run performance, even after controlling for VC selectivity. We find that more reputable VCs exhibit more active post-IPO involvement in the corporate governance of their portfolio firms, and this continued VC involvement positively influences post-IPO firm performance.