Two-dimensional magnetoexcitons in the presence of spin-orbit coupling

We study theoretically the effect of spin-orbit coupling on quantum well excitons in a strong magnetic field. We show that, in the presence of an in-plane field component, the excitonic absorption spectrum develops a double-peak structure due to hybridization of bright and dark magnetoexcitons. If the Rashba and Dresselhaus spin-orbit constants are comparable, the magnitude of splitting can be tuned in a wide interval by varying the azimuthal angle of the in-plane field. We also show that the interplay between spin-orbit and Coulomb interactions leads to an anisotropy of exciton energy dispersion in the momentum plane. The results suggest a way for direct optical measurements of spin-orbit parameters.Comment: 9 pages, 6 figure

ИССЛЕДОВАНИЕ ЭКСПЛУАТАЦИОННЫХ СВОЙСТВ ПОЛИМЕРНЫХ ПЕРЕВЯЗОЧНЫХ СРЕДСТВ

Nowadays there are a lot of contemporary wound dressings in theforms like foams and films made on the basis of different polymers. It’s necessary to know optimal particular numeric values of wound dressings’ key operational properties, which determine comfort and easy to use. As the basic operational characteristics we have chosen for investigation such parameters as: swelling behavior, which indicates amount of liquid, swollen by the unit weight of the material; elastic modulus as a measure of material’s elasticity; surface and apparent density of the material; relations among these characteristics. We’ve offered to differentiate materials in accordance with particular values of swelling behavior, because manufactures range wound dressings for wounds with different amount of secreted exudate without specifying exact values. Also physical and mechanical properties of multilayer wound dressings were investigated, paying attention to the elasticity of the material. So, the target of the investigation as a whole was thecomparison of wound dressings’ operational properties from different manufactures to investigate swelling behavior, physical and mechanical properties. В настоящее время существует большое количество современных перевязочных средств в виде губок и пленок, изготовленных на основе различных полимеров. В практической работе врачам важно знать оптимальные конкретные значения ключевых эксплуатационных характеристик перевязочных средств, которые определяют комфорт и простоту в эксплуатации. В качестве основных эксплуатационных характеристик нами были выбраны: сорбционная способность, которая определяет количество жидкости, поглощаемой единицей массы материала; модуль упругости, который является показателем эластичности материала; поверхностная и кажущаяся плотности материала; а также исследованы зависимости между данными эксплуатационными характеристиками. Мы предложили дифференцировать материалы в соответствии с конкретными значениями степеней набухания, поскольку производители делят перевязочные средства для ран с различным количеством выделяемого экссудата без указания точных значений. Также мы изучили физико-механические свойства многослойных перевязочных средств, обращая внимание на параметры, определяющие эластичность материала. Поэтому целью данной работы в целом является проведение сравнительных испытаний эксплуатационных свойств повязок отечественных и зарубежных производителей в целях оценки сорбционных и физико-механических свойств

Magnetic Resonance of the Intrinsic Defects of the Spin-Peierls Magnet CuGeO3

ESR of the pure monocrystals of CuGeO3 is studied in the frequency range 9-75 GHz and in the temperature interval 1.2-25 K. The splitting of the ESR line into several spectral components is observed below 5 K, in the temperature range where the magnetic susceptibility is suppressed by the spin-Peierls dimerization. The analysis of the magnetic resonance signals allows one to separate the signals of the S=1/2- and S=1 defects of the spin-Peierls phase. The value of g-factor of these signals is close to that of the Cu-ion. The additional line of the magnetic resonance is characterized by an anomalous value of the g-factor and by the threshold-like increase of the microwave susceptibility when the microwave power is increasing. The ESR signals are supposingly attributed to two types of the planar magnetic defects, arising at the boundaries of the domains of the spin-Peierls state with the different values of the phase of the dimerization.Comment: LATEX-text, 12 PS-figures, typos corrected, LATEX-style change

Anomalous exponents in the rapid-change model of the passive scalar advection in the order ϵ3\epsilon^{3}

Field theoretic renormalization group is applied to the Kraichnan model of a passive scalar advected by the Gaussian velocity field with the covariance $- <{\bf v}(t,{\bf x}){\bf v}(t',{\bf x'})> \propto\delta(t-t')|{\bf x}-{\bf x'} |^{\epsilon}$. Inertial-range anomalous exponents, related to the scaling dimensions of tensor composite operators built of the scalar gradients, are calculated to the order $\epsilon^{3}$ of the $\epsilon$ expansion. The nature and the convergence of the $\epsilon$ expansion in the models of turbulence is are briefly discussed.Comment: 4 pages; REVTeX source with 3 postscript figure

The Minimum Stellar Mass in Early Galaxies

The conditions for the fragmentation of the baryonic component during merging of dark matter halos in the early Universe are studied. We assume that the baryonic component undergoes a shock compression. The characteristic masses of protostellar molecular clouds and the minimum masses of protostars formed in these clouds decrease with increasing halo mass. This may indicate that the initial stellar mass function in more massive galaxies was shifted towards lower masses during the initial stages of their formation. This would result in an increase of the number of stars per unit halo mass, i.e., the efficiency of star formation.Comment: 18 pages, 7 figure

Calculation of the anomalous exponents in the rapid-change model of passive scalar advection to order ε3\varepsilon^{3}

The field theoretic renormalization group and operator product expansion are applied to the model of a passive scalar advected by the Gaussian velocity field with zero mean and correlation function \propto\delta(t-t')/k^{d+\eps}. Inertial-range anomalous exponents, identified with the critical dimensions of various scalar and tensor composite operators constructed of the scalar gradients, are calculated within the $\varepsilon$ expansion to order $\varepsilon^{3}$ (three-loop approximation), including the exponents in anisotropic sectors. The main goal of the paper is to give the complete derivation of this third-order result, and to present and explain in detail the corresponding calculational techniques. The character and convergence properties of the $\varepsilon$ expansion are discussed; the improved ``inverse'' $\varepsilon$ expansion is proposed and the comparison with the existing nonperturbative results is given.Comment: 34 pages, 5 figures, REVTe

Антимикробная и антимикотическая фотодинамическая терапия (обзор литературы)

This review highlights the possibilities of photodynamic therapy (PDT) using drugs based on chlorin e6, aluminum phthalocyanine, methylene blue as photosensitizers for bacterial and fungal pathologies. This method was developed initially to treat tumor diseases, where it had shown its high efficiency and safety. Now photodynamic therapy is actively used in the treatment of cancers of the skin, bronchi, stomach, cervix, larynx, or other regions. However, numerous studies have been carried out for the entire existence of the method, demonstrating new possibilities of its application. This review highlights a number of studies in which the efficacy and safety of antimicrobial and antimycotic PDT were studied in vivo and in vitro. It has been proven to have a positive effect on the reparative processes in the wound. An experimental study was carried out to study the effectiveness of photodynamic therapy in the treatment of peritonitis in mice. Demonstrated anti-inflammatory potential in the treatment of autoimmune diseases.В обзоре литературы освещены возможности фотодинамической терапии (ФДТ) с использованием в качестве фотосенсибилизатора (ФС) ряда препаратов, в том числе на основе хлорина е6, фталоцианина алюминия, метиленового синего, при бактериальных и грибковых патологиях. Метод ФДТ изначально был разработан для лечения опухолевых заболеваний, в борьбе с которыми показал свою высокую эффективность и безопасность. В настоящее время ФДТ активно применяется при лечении пациентов с раком кожи, бронхов, желудка, шейки матки, гортани и других локализаций. Однако за все время существования метода были проведены многочисленные исследования, демонстрирующие новые возможности его применения. В настоящем обзоре освещен ряд научно-исследовательских работ, в которых была изучена эффективность и безопасность антимикробной и антимикотической ФДТ в экспериментах in vivo и in vitro. Выполнен обзор публикаций, посвященных изучению механизмов антимикробного действия ФДТ, а также изучающих влияние ФДТ на репаративные процессы в ране. В исследованиях, включенных в настоящий обзор, доказана высокая эффективность антимикробной и антимикотической ФДТ. Продемонстрирован противовоспалительный потенциал метода при лечении аутоиммунных заболеваний у людей

Observational Manifestations of the First Protogalaxies in the 21 cm Line

The absorption properties of the first low-mass protogalaxies (mini-halos) forming at high redshifts in the 21-cm line of atomic hydrogen are considered. The absorption properties of these protogalaxies are shown to depend strongly on both their mass and evolutionary status. The optical depths in the line reach $\sim$0.1-0.2 for small impact parameters of the line of sight. When a protogalaxy being compressed, the influence of gas accretion can be seen manifested in a non-monotonic frequency dependence of the optical depth. The absorption characteristics in the 21-cm line are determined by the thermal and dynamical evolution of the gas in protogalaxies. Since the theoretical line width in the observer's reference frame is 1-6 kHz and the expected separation between lines 8.4 kHz, the lines from low mass protogalaxies can be resolved using ongoing and future low frequency interferometers.Comment: 12 pages, 5 figure

Finite temperature nonlocal effective action for quantum fields in curved space

Massless and massive scalar fields and massless spinor fields are considered at arbitrary temperatures in four dimensional ultrastatic curved spacetime. Scalar models under consideration can be either conformal or nonconformal and include selfinteraction. The one-loop nonlocal effective action at finite temperature and free energy for these quantum fields are found up to the second order in background field strengths using the covariant perturbation theory. The resulting expressions are free of infrared divergences. Spectral representations for nonlocal terms of high temperature expansions are obtained.Comment: 32 pages, LaTe

Modeling of the Magnetic Susceptibilities of the Ambient- and High-Pressure Phases of (VO)_{2}P_{2}O_{7}

The magnetic susceptibilities chi versus temperature T of powders and single crystals of the ambient-pressure (AP) and high-pressure (HP) phases of (VO)_{2}P_{2}O_{7} are analyzed using an accurate theoretical prediction of chi(T, J1, J2) for the spin-1/2 antiferromagnetic alternating-exchange (J1, J2) Heisenberg chain. The results are consistent with recent models with two distinct types of alternating-exchange chains in the AP phase and a single type in the HP phase. The spin gap for each type of chain is derived from the respective set of two fitted alternating exchange constants and the one-magnon dispersion relation for each of the two types of chains in the AP phase is predicted. The influences of interchain coupling on the derived intrachain exchange constants, spin gaps, and dispersion relations are estimated using a mean-field approximation for the interchain coupling. The accuracies of the spin gaps obtained using fits to the low-T chi(T) data by theoretical low-T approximations are determined. The results of these studies are compared with previously reported estimates of the exchange couplings and spin gaps in the AP and HP phases and with the magnon dispersion relations in the AP phase measured previously using inelastic neutron scattering.Comment: 25 two-column REVTeX pages, 16 embedded figures, 6 tables. Figures 9 and 10 and Sec. IIIC revised due to errors in Eq. (1) of Ref. 24 which gives the theoretical one-magnon dispersion relation for coupled alternating-exchange chains. Minor revisions also made in other section