Evaluation of Contemporary Environmental Condition of River Basins in Southern Pre-Caspian Areas of Azerbaijan

Southern Pre-Caspian areas of the Republic of Azerbaijan have favorable geographical position as well as natural and climatic condition for dwelling, development of settlements, and industrial activity. Most areas have fertile soils and attractive landscapes. These factors facilitate human distribution in the researched area and therefore, the area is highly populated. Population are engaged mainly in areas such as farming, namely production of tea, vine, cereals, vegetable, different fruits, including citrus plants, production of foods, and also cattle- and sheep-breeding. As a result, the coastal zone and rivers experience high anthropogenic influence. This article deals with the study of anthropogenic pollution of highly-settled river basins and valleys as well as evaluation of changes going by quality of river waters in southern Pre-Caspian areas of Azerbaijan

Free Bicommutative Algebras

2000 Mathematics Subject Classification: Primary 17A50, Secondary 16R10, 17A30, 17D25, 17C50.Algebras with identities a(bc)=b(ac), (ab)c=(ac)b is called bicommutative. Bases and the cocharacter sequence for free bicommutative algebras are found. It is shown that the exponent of the variety of bicommutaive algebras is equal to 2

Biosensors Using Free and Immobilized Cells of Luminous Bacteria

The technologies of receiving free and immobilized photobacteria cells for biomonitoring of toxins are considered. The mechanisms of interaction of toxins with photobacteria are observed. The main attention is paid to the immobilized procedures and structures of carriers. Data on poly(vinyl)alcohol (PVA) cryogel immobilization of different strains of photobacteria are presented. It is established that intensity and stability of light emission of PVA cells is competently controlled by: (1) intensity and persistence of a luminescent cycle using bacterial strain; (2) type of the carrier and the composition of the gel-formation medium; (3) freeze-thawing procedures; and (4) physical and chemical conditions of storage and application. The developed technology of cryogenic gel formation has kept the survival of luminous bacteria in the carrier practically at 100% without the introduction of additional cryoprotecting agents and procedures of a light induction. With storage at −80°C, bioluminescent activity remained without changes about 2 years. Using the immobilized preparations of biosensor, the discrete and continuous analysis of heavy metals, chlorophenols, and pesticides is carried out. The sensitivity of free and immobilized cells to the chosen toxicants is approximately identical. The continuous monitoring of toxicant conditions is optimized

Long-Term Photometric and Spectral Variations of DI Cephei

We have analyzed the photometric and spectral variations of the classical T Tauri star DI Cep for the last 50 years. Currently the star is at its faintest state and possesses an emission spectrum in the visual range. Synchronous spectroscopy and UBV R photometry show that the higher the brightness, the stronger were the intensities of hydrogen Hα, Hβ emission lines and of FeII, HeI λ5876 ˚A emissions. For the first time, we detected, with a high probability, quasi-periodic variations of the star’s brightness and of its spectrum with the period P = 2020 ± 200 days

On a factorization of second order elliptic operators and applications

We show that given a nonvanishing particular solution of the equation (divpgrad+q)u=0 (1) the corresponding differential operator can be factorized into a product of two first order operators. The factorization allows us to reduce the equation (1) to a first order equation which in a two-dimensional case is the Vekua equation of a special form. Under quite general conditions on the coefficients p and q we obtain an algorithm which allows us to construct in explicit form the positive formal powers (solutions of the Vekua equation generalizing the usual powers of the variable z). This result means that under quite general conditions one can construct an infinite system of exact solutions of (1) explicitly, and moreover, at least when p and q are real valued this system will be complete in ker(divpgrad+q) in the sense that any solution of (1) in a simply connected domain can be represented as an infinite series of obtained exact solutions which converges uniformly on any compact subset of . Finally we give a similar factorization of the operator (divpgrad+q) in a multidimensional case and obtain a natural generalization of the Vekua equation which is related to second order operators in a similar way as its two-dimensional prototype does

DEFINITION of EXTENDED STRUCTURAL DEFECTS IN EPITAXIAL FILMS of ZnTeG‘GaAs GROWN by MBE

The last three decades of the development of solid state physics are characterized by the fact that the main objects of research are increasingly not massive crystals, but thin films, multilayer thin-film systems, conducting filaments and crystallites of small size. Epitaxial films are grown on a substrate of a single crystal of the same or another material. In the first case, the epitaxial layer with the correct technology becomes a natural extension of the substrate. Epitaxial film can be doped with various impurities. To introduce an alloying admixture into the epitaxial film, three methods are used. According to the first method, the necessary admixture is dissolved in the source of the semiconductor material. The second method involves the use of an alloying admixture in an elementary form and its placement in the pipe between the source of the semiconductor material and the substrate. Sometimes the alloying admixture is placed in a separate temperature zone of the working pipe. The third method is to add an alloying admixture to the volatile iodides. Interest in the study of quantum-dimensional structures based on A2B6 materials is due to the possibility of manufacturing on their basis of injection sources of coherent and incoherent radiation, as well as emitters with electronic pumping, covering almost the entire visible range. To clarify the nature of the luminescence centers responsible for the i1c band, we studied the effect on the FL spectra of the buffer ES ZnTe: (I)a thin (5-10 nm) intermediate recrystallized ZnTe layer located between the buffer layer and the substrate (100) GaAs; (ii)the thickness of the buffer layer, as well as (III) the build-up of quantum-dimensional layers CdxZn1-xTeG‘ZnTe (xq0.2-0.4). In addition, the spatial distribution (in buffer depth) of the intensity (I) and spectral position (m) of THE i1c band, as well as temperature dependences of I and m were investigated. At the same time, x-ray diffraction measurements of the swing curves were carried out to control the structural perfection of the ZnTe ES. In the exciton region of the spectrum, there are also intense band I1C hmq2.356 eV and located in close proximity to her far side strip with hmq2.352 eV (I2C) lower intensity. In the samples with quantum layers from the short-wave side of I1C, an additional band IX with hmq2.359 eV is observed. A number of characteristics of the bands in the group I1C different from the corresponding characteristics such as both free and associated excitons. Thus, the change in the technology of growing MBE epitaxial buffer layers ZnTeG‘GaAs: (1) the use of a thin, recrystallized layer ZnTe (d10 nm), as well as (2) an increase in the thickness of the buffer layer leads to an improvement in the structure of the ES, as well as an increase in the total intensity of the FL bands in the exciton spectrum and a decrease in the impurity. The paper also provides with additional information on the nature of the i1c band and the IX band found near it. The difference between the temperature and deformation dependences of the positions of these bands on the corresponding characteristics of the exciton radiation lines, as well as the increase in their intensity with a decrease in deformations made it possible to link these bands with extended defects. Based on these data, as well as the results of x-ray diffraction measurements, it is assumed that the centers responsible for the I1C band are associated with the boundaries of the subunits in the mosaic structure

Investigation of conduction band structure, electron scattering mechanisms and phase transitions in indium selenide by means of transport measurements under pressure

In this work we report on Hall effect, resistivity and thermopower measurements in n-type indium selenide at room temperature under either hydrostatic and quasi-hydrostatic pressure. Up to 40 kbar (= 4 GPa), the decrease of carrier concentration as the pressure increases is explained through the existence of a subsidiary minimum in the conduction band. This minimum shifts towards lower energies under pressure, with a pressure coefficient of about -105 meV/GPa, and its related impurity level traps electrons as it reaches the band gap and approaches the Fermi level. The pressure value at which the electron trapping starts is shown to depend on the electron concentration at ambient pressure and the dimensionality of the electron gas. At low pressures the electron mobility increases under pressure for both 3D and 2D electrons, the increase rate being higher for 2D electrons, which is shown to be coherent with previous scattering mechanisms models. The phase transition from the semiconductor layered phase to the metallic sodium cloride phase is observed as a drop in resistivity around 105 kbar, but above 40 kbar a sharp nonreversible increase of the carrier concentration is observed, which is attributed to the formation of donor defects as precursors of the phase transition.Comment: 18 pages, Latex, 10 postscript figure