Electron-phonon interaction via Pekar mechanism in nanostructures

We consider an electron-acoustic phonon coupling mechanism associated with the dependence of crystal dielectric permittivity on the strain (the so-called Pekar mechanism) in nanostructures characterized by strong confining electric fields. The efficiency of Pekar coupling is a function of both the absolute value and the spatial distribution of the electric field. It is demonstrated that this mechanism exhibits a phonon wavevector dependence similar to that of piezoelectricity and must be taken into account for electron transport calculations in an extended field distribution. In particular, we analyze the role of Pekar coupling in energy relaxation in silicon inversion layers. Comparison with the recent experimental results is provided to illustrate its potential significance

Data provenance and management in radio astronomy: a stream computing approach

New approaches for data provenance and data management (DPDM) are required for mega science projects like the Square Kilometer Array, characterized by extremely large data volume and intense data rates, therefore demanding innovative and highly efficient computational paradigms. In this context, we explore a stream-computing approach with the emphasis on the use of accelerators. In particular, we make use of a new generation of high performance stream-based parallelization middleware known as InfoSphere Streams. Its viability for managing and ensuring interoperability and integrity of signal processing data pipelines is demonstrated in radio astronomy. IBM InfoSphere Streams embraces the stream-computing paradigm. It is a shift from conventional data mining techniques (involving analysis of existing data from databases) towards real-time analytic processing. We discuss using InfoSphere Streams for effective DPDM in radio astronomy and propose a way in which InfoSphere Streams can be utilized for large antennae arrays. We present a case-study: the InfoSphere Streams implementation of an autocorrelating spectrometer, and using this example we discuss the advantages of the stream-computing approach and the utilization of hardware accelerators

The Early Evolution of Massive Stars: Radio Recombination Line Spectra

Velocity shifts and differential broadening of radio recombination lines are used to estimate the densities and velocities of the ionized gas in several hypercompact and ultracompact HII regions. These small HII regions are thought to be at their earliest evolutionary phase and associated with the youngest massive stars. The observations suggest that these HII regions are characterized by high densities, supersonic flows and steep density gradients, consistent with accretion and outflows that would be associated with the formation of massive stars.Comment: ApJ in pres

Holographic Structure Transfer from Dichromated Gelatin Layers to a Polymethylmethacrylate Substrate

It is shown that the formation of a holographic structure on the polymethylmethacrylate (PMMA) surface is based on the use of the destructive effect of short-wave UV radiation with a wavelength less than 270 nm through windows previously formed in a thin layer of dichromated gelatin (DCG) covering the substrate. The optimization of the PMMA surface treatment by isopropanol and methylisobutyl ketone (MIBK) developers was made, which allowed creating on the PMMA substrates relief-phase holographic gratings with the high diffraction efficiency (DE) of about 25% and maximum depth of the surface relief of the order of 1 μm. Keywords: holographic gratings, surface relief, UV radiation, dichromated gelatin, polymethylmethacrylate, methylisobutyl ketone (MIBK)

Virality of medical content in Russian social media

The work objective is to conduct a sociological study aimed at assessing validity (appropriateness) of the traditional characteristics and formation of a pool of specialized characteristics of the viral content, used in the promotion of health services by means of social media marketin

Estimation of Innovative Activity of the University

On the basis of Belgorod region innovation activity analysis, positive relationship between shipped innovation items and domestic research and development costs was found. Semantic differential was used for multiple estimation of BelSU innovation activity and competiveness. BelSU integrated index showed high-enough innovation activity of this universityyesBelgorod State Universit

Negative high-frequency differential conductivity in semiconductor superlattices

We examine the high-frequency differential conductivity response properties of semiconductor superlattices having various miniband dispersion laws. Our analysis shows that the anharmonicity of Bloch oscillations (beyond tight-binding approximation) leads to the occurrence of negative high-frequency differential conductivity at frequency multiples of the Bloch frequency. This effect can arise even in regions of positive static differential conductivity. The influence of strong electron scattering by optic phonons is analyzed. We propose an optimal superlattice miniband dispersion law to achieve high-frequency field amplification