Effect of Temperature and Band Nonparabolicity on Density of States of Two Dimensional Electron Gas

The analysis of the density of states for electrons in single quantum well, the conduction band nonparabolicity take is account. It is shown that the degree of conduction band nonparabolicity pronounces depending on the energy density of states. With increasing temperature, a step change in the density of states smoothes and at high temperatures is completely blurred. Nonparabolicity dispersion law manifests itself in a wide range of temperatures. Calculations are carried out for the example of the quantum wells in InAs and InSb.

Broadening Thermal Energy Levels and Density States Quasi One-Dimensional Electron Gas

We have investigated the energy states of a one-dimensional electron gas and analyzed the temperature dependence of the density of states. It is shown that with increasing temperature due to thermal broadening of quantum, levels are blurred.

Analysis of the Distribution of Tulipa fosteriana and Tulipa ingens. The Importance of Protecting Wild Plants, in Particular Tulips All over the World

The assessment of the distribution and importance of the protection of tulip varieties around the world and separately rare, wild-growing ancestors of cultivated tulips, in particular Tulipa fosteriana and Tulipa ingens on the globe, including Central Asia, Uzbekistan and the Samarkand region, was described. A distribution map was introduced to visualize the data. Information about the morphological description of the studied species was also given.

Obtaining the Fluorescent Chitosan for Investigations in the Analytical Ultracentrifuge

1) In order to achieve the visibility of the chitosan macromolecule for the UV optical system of the analytical ultracentrifuge on investigation of the molecular characteristics and polymers interactions, the labeling of chitosan by a new fluorophore of fluorescein-5-isothiocyanat was carried out. 2) Samples of fluorescent chitosan with two different degrees of fluorophore substitution and various degrees of acetylation were obtained. 3) The labeled chitosans with the fluorescein-5-isothiocyanat allowed estimating the sedimentation coefficient and the molecular characteristic in the analytical ultracentrifuge. 4) The sensitivity of the UV-optical system of the analytical ultracentrifuge for the obtained fluorescent samples of chitosan relatively to the fixation of the meniscus and the influence of the wavelength and rotation speed were estimated.

Temperature Stimulation of Effective Value of Density of the Current of Semiconductor Solar Cells

Influence of temperature on effective value of a current density of a semiconductor solar cell is investigated. New equations for explanation of dependence of photovoltaic characteristics of solar cell from temperature are received.

The Nonideality Coefficient of Current-Voltage Characteristics for Asymmetric p-n-Junctions in a Microwave Field

It is shown that the nonideality coefficient m actually depends on the electron temperature Te, and the hole temperature Th. We get more general expression for the nonideality coefficient, taking into account the concentration of electrons and holes, as well as their temperature, coefficient and diffusion length, the temperature of the phonons, the applied voltage, and the height of the potential barrier.

Adsorption of Toluene on Film Membranes of Chitosan/Nа-CMC

The sorption properties of films on bases of chitosan and sodium carboxyl methylcellulose (Na-CMC) with toluene have been checked. The sorption rate, sorption thermodynamics and isothermal properties of toluene molecules in chitosan/Na-CMC films are analyzed by adsorption-calorimetric method. Thus, it was found that toluene is adsorbed on the chitosan/Na-CMC film by the same patterns of sorption of aromatic compounds, due to the process of penetration of toluene molecules into the network of chitosan macromolecules and this is preceded by the absorption process by the surface of the chitosan/Na-CMC film.

On the Thermodynamics of a Two-Dimensional Electron Gas with Non-Parabolic Dispersion

A thermodynamic density of states, electron density in the subband and the entropy of the gas as function of the temperature and the total two-dimensional electron density are studied. Semiconductor conduction band dispersion is described by the simplified Kane model. Numerical simulation shows that with an increase in the total electron concentration, thermodynamic density of states at low temperatures changes abruptly and smoothes jumps at high temperatures. This change manifests itself in the peculiar thermodynamic characteristics. The results are used to interpret existing experimental data.

The Use of Phase Portraits for the Study of the Generation-Recombination Processes in Semiconductor

Theoretical investigation of generation-recombination processes in silicon, which has a lifetime of charge carriers 10-3 s and capture cross sections of 10-16 sm2. For the study uses a method of phase portraits, which are widely used in the theory of vibrations. It is shown that the form of phase portraits strongly depends on the frequency of exposure to the external variable deformation.

New Method of Determining the Landau Levels in Narrow-Gap Semiconductors

With the help of mathematical models, the temperature dependence of the density of energy states was determined in a quantizing magnetic field. The influence of the effective mass at the temperature dependence of the density of the energy states in a strong quantizing magnetic field is investigated. The dependence temperature of density of energy states graph is obtained in a strong magnetic field for InSb.

Temperature Dependence of Urbach Energy in Non-Crystalline Semiconductors

Until now, no analytical relationships have been derived for the temperature dependence of the Urbach energy in non-crystalline semiconductors. Consequently, the problem associated with the theoretical study of the temperature dependence of this energy has not been solved. This paper presents the results of theoretical calculations and attempts to establish the temperature dependence of the Urbach energy in non-crystalline semiconductors. A linear increase in the Urbach energy with increasing temperature is shown.

Chemical composition and in vitro biological activities of essential oil from Allochrusa gypsophiloides

Background:Allochrusa gypsophiloides Rgl(Caryophyllaceae)is the best known endemic saponin-bearing plant of Central Asia,being widely used in traditional medicine and different branches of industry.In traditional medicine,the decoction of the roots of this plant has been used as an expectorant for bronchitis,similar to other drugs with saponins.Methods:For the first time,the chemical composition of the volatile secondary metabolites obtained from the aerial parts of A.gypsophiloides was evaluated using GC-MS method.In vitro antioxidant activity of the essential oil was evaluated using DPPH and ABTS assays.The cytotoxic activities were carried out by MTT assay.Results:A total of 59 components were identified in this species representing 89.8%of the whole oil.The A.gypsophiloides essential oil was rich in oxygenated monoterpenoids,whereas pulegone(32.9%),trans-p-menthan-3-one(6.2%),hexadecanoic acid(3.6%),trans-verbenol(3.2%),phytol(3.2%),2-isopropyl-5-methylcyclohexanone(2.7%),isopiperitenon(2.1%)were predominant in the oil.The weak activity was found for the oil with IC50 values 456.4±5.39μg/ml for DPPH and 745.0±6.87μg/ml for ABTS assay.The essential oil showed moderate cytotoxic effects against prostate cancer(PC-3)(IC50:89.9±2.01μg/ml)and colon adenocarcinoma(HT-29)cells(IC50:43.6±2.38μg/ml).Conclusion:The cytotoxic activity of A.gypsophiloides essential oil against HT-29(colon)cancer cells is consistent with antitumor effects of some species from Allochrusa genus and their traditional use to treat cancer diseases.

Effects of Band Nonparabolicity and Band Offset on the Electron Gas Properties in InAs/AlSb Quantum Well

One-band effective mass model is used to simulation of electron gas properties in quantum well. We calculate of dispersion curves for first three subbands. Calculation results of Fermi energy, effective mass at Fermi level as function of electron concentration are presented. The obtained results are good agreement with the experimental dates.

Influence of Recombination Centers on the Phase Portraits in Nanosized Semiconductor Films

Influence of recombination centers’ changes on the form of phase portraits has been studied. It has been shown that the shape of the phase portraits depends on the concentration of semiconductor materials’ recombination centers.

Test particles and quasiperiodic oscillations around Kiselev black hole with cloud of strings

In the present study,we investigate the dynamics of test particles around a Schwarzschild black hole surrounded by quintessence and immersed in a scalar string cloud field.We start our study by defining the possible values of the quintessence and cloud of string parameters corresponding to the existence of the black hole horizon for fixed values of the parameters of the equation of state for dark energy.We also study the effects of the effective potential on the circular motion,energy,and angular momentum of the test particles together with the innermost stable circular orbits(ISCOs).We investigate the fundamental frequencies in the particle oscillations along stable circular orbits.We relate the stability of the orbits to the Lyapunov exponent,and the chaotic behavior is studied graphically.Finally,we apply the fundamental frequencies to describe quasiperiodic oscillations(QPOs)and find that,in the presence of both fields,low-frequency twin-peak QPOs are not observed.In addition,we obtain the constraint values for the string cloud parameter and mass of the black hole candidates located in the center of the microquasars GRO J1655-40 and GRS 1915+105 as well as the Milky Way galaxy.