Anisotropic exchange interaction of localized conduction-band electrons in semiconductor structures

The spin-orbit interaction in semiconductors is shown to result in an anisotropic contribution into the exchange Hamiltonian of a pair of localized conduction-band electrons. The anisotropic exchange interaction exists in semiconductor structures which are not symmetric with respect to spatial inversion, for instance in bulk zinc-blend semiconductors. The interaction has both symmetric and antisymmetric parts with respect to permutation of spin components. The antisymmetric (Dzyaloshinskii-Moriya) interaction is the strongest one. It contributes significantly into spin relaxation of localized electrons; in particular, it governs low-temperature spin relaxation in n-GaAs with the donor concentration near 10^16cm-3. The interaction must be allowed for in designing spintronic devices, especially spin-based quantum computers, where it may be a major source of decoherence and errors

Shake-up Processes in a Low-Density Two-Dimensional Electron Gas: Spin-Dependent Transitions to Higher Hole Landau Levels

A theory of shake-up processes in photoabsorption of an interacting low-density two-dimensional electron gas (2DEG) in strong magnetic fields is presented. In these processes, an incident photon creates an electron-hole pair and, because of Coulomb interactions, simultaneously excites one particle to higher Landau levels (LL's). In this work, the spectra of correlated charged spin-singlet and spin-triplet electron-hole states in the first hole LL and optical transitions to these states (i.e., shake-ups to the first hole LL) are studied. Our results indicate, in particular, the presence of optically-active three-particle quasi-discrete states in the exciton continuum that may give rise to surprisingly sharp Fano resonances in strong magnetic fields. The relation between shake-ups in photoabsorption of the 2DEG and in the 2D hole gas (2DHG), and shake-ups of isolated negative X^- and positive X^+ trions are discussed.Comment: 8 pages, 8 figures. References updated, one figure added (Fig. 6). Accepted in Phys. Rev.

Symmetry of anisotropic exchange interactions in semiconductor nanostructures

The symmetry of exchange interaction of charge carriers in semiconductor nanostructures (quantum wells and quantum dots) is analysed. It is shown that the exchange Hamiltonian of two particles belonging to the same energy band can be universally expressed via pseudospin operators of the particles. The relative strength of the anisotropic exchange interaction is shown to be independent of the binding energy and the isotropic exchange constant

Radiative power of wildfires in Siberia on the basis of TERRA/Modis imagery processing

Variety of radiation power of wildfire was investigated by processing TERRA/Modis imagery in 4 μm spectral band. Fire radiative power (FRP) was used for calibrating high-temperature event database obtained by the satellite technique. An analysis was performed on the database of Siberian wildfires for 2010– 2012. Dynamics of FRP was investigated for a number of wildfires including some cases of crown fire. FRP variation was evaluated for various forest zones of Siberia. Classification of wildfires was elaborated in terms of FRP value as a GIS-layer over the territory of Siberia

IMPACT OF BETALACTOGLOBULIN HYDROLYSATE ON STRUCTURAL AND MECHANICAL PROPERTIES OF ALLERGENIC POTENCY-RESTRICTED YOGURT

Creation and development of low-allergenic food products in sour-milk drink groups is the urgent trend in dairy industry development. By the results of patent search, one of challenging methods to reduce the dairy product allergenicity has been identified. To produce such products, the method involves using whey protein hydrolysates, in particular, β-lactoglobulin hydrolysate obtained by using enzyme preparations Flavorpro 750MDP and Promod 439L. The research aimed to study normalized milk mixtures fermented with β-lactoglobulin hydrolysate with the resulting changes in the chemical composition, as well as to select starter microorganisms that provide the required stability and structure of the milk coagulum by producing exopolysaccharides. The researches were carried out at the base of several laboratories as follow: The Federal Research Centre «Fundamentals of Biotechnology» of the Russian Academy of Sciences, Christian Hansen LLC, the Voronezh State University of Engineering Technologies and the Federal Research Centre of Nutrition and Biotechnology. This work is based on standard and conventional research methods. Advanced tools and information technologies were used to assess the properties of raw materials, semi-finished products and food products. By the results of studies completed, it was found unreasonable to replace over 20% of whole milk with β-lactoglobulin hydrolysate during normalization, since such replacement resulted in an increase in the mixture acidity and prevented the normal growth and development of Streptococcus thermophilus, the basic exopolysaccharide producer. At the same time, the length of fermentation increased up to 5-6 h as the mass fraction of β-lactoglobulin hydrolysate increased. The viscosity of the resulting coagulum increased due to the reaction of exopolysaccharides with the protein gel mesh and fixation thereof on the surface of protein matrix. The residual antigenicity of the finished product decreased to 48.5% relative to that of sour-milk drinks produced as per traditional technology