Quantum transport in a curved one-dimensional quantum wire with spin-orbit interactions

The one-dimensional effective Hamiltonian for a planar curvilinear quantum wire with arbitrary shape is proposed in the presence of the Rashba spin-orbit interaction. Single electron propagation through a device of two straight lines conjugated with an arc has been investigated and the analytic expressions of the reflection and transmission probabilities have been derived. The effects of the device geometry and the spin-orbit coupling strength $\alpha$ on the reflection and transmission probabilities and the conductance are investigated in the case of spin polarized electron incidence. We find that no spin-flip exists in the reflection of the first junction. The reflection probabilities are mainly influenced by the arc angle and the radius, while the transmission probabilities are affected by both spin-orbit coupling and the device geometry. The probabilities and the conductance take the general behavior of oscillation versus the device geometry parameters and $\alpha$. Especially the electron transportation varies periodically versus the arc angle $\theta_{w}$. We also investigate the relationship between the conductance and the electron energy, and find that electron resonant transmission occurs for certain energy. Finally, the electron transmission for the incoming electron with arbitrary state is considered. For the outgoing electron, the polarization ratio is obtained and the effects of the incoming electron state are discussed. We find that the outgoing electron state can be spin polarization and reveal the polarized conditions.Comment: 7 pages, 8 figure

Quantum corrections in the Boltzmann conductivity of graphene and their sensitivity to the choice of formalism

Semiclassical spin-coherent kinetic equations can be derived from quantum theory with many different approaches (Liouville equation based approaches, nonequilibrium Green's functions techniques, etc.). The collision integrals turn out to be formally different, but coincide in textbook examples as well as for systems where the spin-orbit coupling is only a small part of the kinetic energy like in related studies on the spin Hall effect. In Dirac cone physics (graphene, surface states of topological insulators like Bi_{1-x}Sb_x, Bi_2Te_3 etc.), where this coupling constitutes the entire kinetic energy, the difference manifests itself in the precise value of the electron-hole coherence originated quantum correction to the Drude conductivity $\sim e^2/h * \ell k_F$. The leading correction is derived analytically for single and multilayer graphene with general scalar impurities. The often neglected principal value terms in the collision integral are important. Neglecting them yields a leading correction of order $(\ell k_F)^{-1}$, whereas including them can give a correction of order $(\ell k_F)^0$. The latter opens up a counterintuitive scenario with finite electron-hole coherent effects at Fermi energies arbitrarily far above the neutrality point regime, for example in the form of a shift $\sim e^2/h$ that only depends on the dielectric constant. This residual conductivity, possibly related to the one observed in recent experiments, depends crucially on the approach and could offer a setting for experimentally singling out one of the candidates. Concerning the different formalisms we notice that the discrepancy between a density matrix approach and a Green's function approach is removed if the Generalized Kadanoff-Baym Ansatz in the latter is replaced by an anti-ordered version.Comment: 31 pages, 1 figure. An important sign error has been rectified in the principal value terms in equation (52) in the vN & NSO expression. It has no implications for the results on the leading quantum correction studied in this paper. However, for the higher quantum corrections studied in arXiv:1304.3929 (see comment in the latter) the implications are crucia

Curved One-Dimensional Wire as a Spin Rotator

We propose a semiconductor structure that can rotate the electron spin without using ferromagnetic contacts, tunneling barriers, external radiation etc. The structure consists of a strongly curved one-dimensional ballistic wire with intrinsic spin-orbit interactions of Rashba type. Our calculations and analytical formulae show that the proposed device can redistribute the current densities between the two spin-split modes without backscattering and, thus, serve as a reflectionless and high-speed spin switcher. Using parameters relevant for InAs we investigate the projection of current density spin polarization on the spin-quantization axis as a function of the Rashba constant, external magnetic field, and radius of the wire's curvature.Comment: 10 pages, 6 figures; replaced with considerably extended versio

Желчнокаменная болезнь среди медицинского персонала поликлиники: факторы риска ее развития в разных профессиональных группах

The aim. Identification of risk factors for gallstone disease (GDS) development between different professional groups of polyclinic medical staff. Material and methods. 75 medical staff members were divided into two groups (1st group: 30 doctors; 2nd group: 45 nurses). All of them were interviewed fo r information about profession, gender, age, waist circumference (WC), body mass index (BMI), smoking, arterial hypertension (AH), diabetes mellitus (DM) and hypercholesterolemia. In addition, women were interviewed about the number of pregnancies, ostmenopause and taking oral contraceptive pills (OCPs). To assess physical activity, a short international questionnaire on physical activity (IPAQ) was used. To identify the presence of professional burnout (PB) syndrome we applied the Maslach Burnout Inventory (MBI) questionnaire, adapted by N.Е. Vodopianova for medical staff. At the final stage, the data of abdominal organs ultrasound examination were analyzed based on the materials of medical staff outpatient records. Results. The GSD prevalence among doctors was 33.3%, and 24.4% among nurses. In both groups age, AH, weight, WC and BMI contribute to GSD formation. In the first group of individuals with GSD, the level of total cholesterol (TC) was significantly higher. In the same group extremely high PB, postmenopause (p <0.05) and hypodynamia (p <0.1) were much more common. In the second group, there were more DM cases and pregnancies (p <0.05). Conclusion. The medical staff of the clinic has a high GSD incidence, whose frequency depends not only on classical risk factors prevalence, but is also determined by profession peculiarities, characterized by high psychological stress and lower physical activity of physicians, compared to nurses.Цель исследования. Выявить факторы риска развития желчнокаменной болезни (ЖКБ) среди медицинского персонала поликлиники в разных профессиональных группах. Материалы и методы. В поликлинике было осмотрено и анкетировано 75 медицинских сотрудников поликлиники, которые были разделены на две группы. В 1-ю были включены 30 врачей; во 2-ю - 45 медицинских сестер. Анализу подвергались такие показатели, как профессия, пол, возраст, объем талии (ОТ), индекс массы тела (ИМТ), курение, наличие артериальной гипертензии (АГ), сахарного диабета (СД), гиперхолестеринемии, постменопаузы; у женщин – количество беременностей и прием оральных контрацептивов (ОК). Для оценки физической активности применяли краткий международный опросник по физической активности (IPAQ). Для выявления симптомов профессионального выгорания (ПВ) использовали опросник Maslach Burnout Inventory (MBI), адаптированный Н.Е. Водопьяновой для медицинских сотрудников. На конечном этапе анализировались данные ультразвукового исследования органов брюшной полости по амбулаторным картам медицинских работников. Результаты. Распространенность ЖКБ среди врачей составила 33,3%, и 24,4% среди медицинских сестер. В обеих группах на формирование ЖКБ влияют возраст, наличие АГ, вес, ОТ, ИМТ. В первой группе лиц с ЖКБ уровень общего холестерина был достоверно выше (ОХ). В этой же группе ПВ крайне высокой степени, постменопауза (p<0,05) и гиподинамия (p<0,1) встречались значительно чаще. В группе медицинских сестер с ЖКБ отмечалось преобладание лиц с СД и большее число беременностей (p<0,05). Заключение. У медицинского персонала поликлиники имеет место высокая распространенность ЖКБ, частота которой зависит не только от распространенности классических факторов риска, но и определяется особенностями профессиональной деятельности, характеризующейся высокой психологической нагрузкой и более низкой физической активностью врачебного персонала, по сравнению с медицинскими сестрами

Energetics and atomic mechanisms of dislocation nucleation in strained epitaxial layers

We study numerically the energetics and atomic mechanisms of misfit dislocation nucleation and stress relaxation in a two-dimensional atomistic model of strained epitaxial layers on a substrate with lattice misfit. Relaxation processes from coherent to incoherent states for different transition paths are studied using interatomic potentials of Lennard-Jones type and a systematic saddle point and transition path search method. The method is based on a combination of repulsive potential minimization and the Nudged Elastic Band method. For a final state with a single misfit dislocation, the minimum energy path and the corresponding activation barrier are obtained for different misfits and interatomic potentials. We find that the energy barrier decreases strongly with misfit. In contrast to continuous elastic theory, a strong tensile-compressive asymmetry is observed. This asymmetry can be understood as manifestation of asymmetry between repulsive and attractive branches of pair potential and it is found to depend sensitively on the form of the potential.Comment: 11 pages, 9 figures, to appear in Phys. Rev.

Anisotropic photoconductivity in graphene

We investigate the photoconductivity of graphene within the relaxation time approximation. In presence of the inter-band transitions induced by the linearly polarized light the photoconductivity turns out to be highly anisotropic due to the pseudospin selection rule for Dirac-like carriers. The effect can be observed in clean undoped graphene samples and be utilized for light polarization detection.Comment: 4 pages, 2 figure

Circulating markers of vascular damage as predictors of cardiovascular events in atherosclerosis and metabolic disorders

The article presents the results of cluster analysis of the contribution of immune inflammation and endothelial dysfunction (ED) markers to the frequency and severity of cardiovascular events (CVE) in cohorts of patients with asymptomatic atherosclerosis (AAS), coronary artery disease (CAD), type 2 diabetes mellitus (T2DM) and metabolic syndrome (MS) during a 3-year prospective observation. Results Circulating markers of ED and immune inflammation, such as ET-1, IL-1β, TNF-α, antibodies to collagen type I and III, and antibodies to chondroitine sulfate (CS) contribute to cardiovascular (CV) manifestation in AAS. In CAD patients ET-1, eNOs, antibodies to collagen, as well as IL-6 and vWf  are the main contributors. In T2DM without clinical manifestation of CAD, the set of markers associated with the adverse events includes ET-1, eNOs, IL-6, anti-C, and anti-HA. In CAD combined with T2DM, the cluster of markers associated with the adverse events includes vWf, TNF-α, eNOs, IL-6, anti-C, anti-HA and CRP. In AAS without MS, the key contributors are ET-1 and vWf, and the presence of anti-C and anti-ChS; in AAS/MS patients, the key markers are IL-1β, TNF-α, anti-C, anti-ChS, anti-HA, and CRP. In CAD without MS, the cluster of markers associated with adverse events includes ET-1, eNOs and anti-HA; in CAD/MS it includes anti-C, ET-1, and IL-6. Conclusion. The obtained results confirm the role of systemic inflammation in the development of atherosclerosis-associated angiopathy in coronary pathology and disorders of carbohydrate metabolism, and also suggest a set of circulating markers as predictors of adverse CVE

Competing mechanisms for step meandering in unstable growth

The meander instability of a vicinal surface growing under step flow conditions is studied within a solid-on-solid model. In the absence of edge diffusion the selected meander wavelength agrees quantitatively with the continuum linear stability analysis of Bales and Zangwill [Phys. Rev. B {\bf 41}, 4400 (1990)]. In the presence of edge diffusion a local instability mechanism related to kink rounding barriers dominates, and the meander wavelength is set by one-dimensional nucleation. The long-time behavior of the meander amplitude differs in the two cases, and disagrees with the predictions of a nonlinear step evolution equation [O. Pierre-Louis et al., Phys. Rev. Lett. {\bf 80}, 4221 (1998)]. The variation of the meander wavelength with the deposition flux and with the activation barriers for step adatom detachment and step crossing (the Ehrlich-Schwoebel barrier) is studied in detail. The interpretation of recent experiments on surfaces vicinal to Cu(100) [T. Maroutian et al., Phys. Rev. B {\bf 64}, 165401 (2001)] in the light of our results yields an estimate for the kink barrier at the close packed steps.Comment: 8 pages, 7 .eps figures. Final version. Some errors in chapter V correcte

Conductivity of graphene: How to distinguish between samples with short and long range scatterers

Applying a quasiclassical equation to carriers in graphene we found a way how to distinguish between samples with the domination of short and long range scatterers from the conductivity measurements. The model proposed explains recent transport experiments with chemically doped as well as suspended graphene.Comment: 6 pages, 3 figures, some references have been corrected and revise