A study of high-NA focusing process of ultrashort laser pulses in bulk of ZnSe has been carried out. It is shown that when focusing laser Gaussian beam with high-aperture lenses into a transparent ...medium aberration distortions occur leading to an increase in focal spot size. The results of experimental studies on ablation of front and back surfaces of a plane-parallel plate with 4 mm thickness made of ZnSe by laser pulses with a duration of 0.3, 1, 10 ps and a wavelength of 1030 nm focused by a micro lens (
NA
= 0.55) are presented. It is shown that at low pulse energies focusing can be considered in a linear mode in which focal spot size is due to aberration distortions.
The concept of a high aperture near-infrared cross-dispersion echelle-spectrometer is presented for greenhouse gases remote measurements from space. This task is of a global nature, industrial and ...household emissions are anthropogenic sources of greenhouse-gas emissions. In recent years, average levels of carbon (CO
2
) and methane (CH
4
) have continued to increase, reaching levels of 410 ppm and 1877 ppb, respectively, to date. Obtaining objective information about the state of the carbon balance in the atmosphere is possible only with the use of space-based instruments. The Driada instrument consists of three channels. The main one is a high-resolution spectrometer for the 1.4- to 1.67-μm wavelength range and is designed to measure CO
2
absorption lines at 1.58 and 1.6 μm, CH
4
lines at 1.65 μm, and a number of H
2
O lines. Two additional channels are designed to measure the O
2
band at 0.76 μm and aerosol characterization. The scientific tasks and key parameters of the main infrared channel are discussed.
Physicochemical properties of stable nanoscale Ge particles have been widely investigated by means of radiation-chemical and chemical-reduction reactions of germanium ions in inversely micellar ...solutions, as well as various methods for registering the resulting nanoparticles, such as UV–Vis spectrophotometry (measurement of optical absorption and luminescence spectra) and AFM measurements. Depending on the concentration of components, the size of a water pool of inverse micelles, the storage time of samples, and the dose of ionizing radiation, the conditions for the formation of Ge NPs have been determined. Significant differences in the initial events of ion-reduction reactions have been revealed. The obtained results have confirmed the unique properties of polarized water in inverse-micellar solutions and the important role of the reducing properties of polarized water in various methods of the formation of Ge nanoparticles, including the processes of self-assembly and “molecular assembly” of metal and bimetal nanoparticles in the postreaction periods.
The concept of plasma separation of spent nuclear fuel and radioactive waste is presented. An approach that is based on using an accelerating potential to overcome the energy and angular spread of ...plasma ions at the separation region inlet and utilizing a potential well to separate spatially the ions of different masses is proposed. It is demonstrated that such separation may be performed at distances of about 1 m with electrical potentials of about 1 kV and a magnetic field of about 1 kG. The estimates of energy consumption and performance of the plasma separation method are presented. These estimates illustrate its potential for technological application. The results of development and construction of an experimental setup for testing the method of plasma separation are presented.
The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory ...with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.
Atomic, electronic structure and composition of top-down metal-assisted wet-chemically etched silicon nanowires were studied by synchrotron radiation based X-ray absorption near edge structure ...technique. Local surrounding of the silicon and oxygen atoms in silicon nanowires array was studied on as-prepared nanostructured surfaces (atop part of nanowires) and their bulk part after, first time applied, in-situ mechanical removal atop part of the formed silicon nanowires. Silicon suboxides together with disturbed silicon dioxide were found in the composition of the formed arrays that affects the electronic structure of silicon nanowires. The results obtained by us convincingly testify to the homogeneity of the phase composition of the side walls of silicon nanowires and the electronic structure in the entire length of the nanowire. The controlled formation of the silicon nanowires array may lead to smart engineering of its atomic and electronic structure that influences the exploiting strategy of metal-assisted wet-chemically etched silicon nanowires as universal matrices for different applications.
Results of a coordinated computational and experimental study of time-averaged velocity and temperature fields in the vicinity of an adiabatic cube that is inserted into the turbulent free convection ...vertical-plate boundary layer are presented. The numerical simulation was based on the steady-state RANS approach using the k-ω SST turbulence model and a version of the differential Reynolds stress model (DRSM). The hot-wire technique was used for velocity measurements, simultaneously with temperature measurements by an accompanied "cold" wire. Two turbulence models produced similar vortex flow structures near the obstacle; however some important quantitative distinctions were observed. The velocity value profiles predicted for the middle vertical plane showed generally a good accordance with the hot-wire measurements carried out in this plane, especially in the DRSM case.
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