Polarization-induced Rashba spin-orbit coupling in structurally symmetric III-Nitride quantum wells

The effective linear coupling coefficient and the total spin-splitting are calculated in Ga- and N- face InGaN quantum wells. Alloy content, geometry, and gate voltage affect an internal field and an electron density distribution in the growth direction that has direct effect on a spin-splitting. The sign of structural inversion asymmetry (SIA) spin-orbit coupling coefficient depends on an internal electric field in the well that results in different signs for Ga-face and N-face III-Nitride structures. The effective linear coupling coefficient is always positive because of the Dresselhaus-type contribution that is a major one in quantum wells under consideration. The magnitude of the spin-splitting is comparable with that experimentally observed in III-Nitrides and III-V zinc-blende structures.Comment: 17 pages, 8 figure

Spin current and electrical polarization in GaN double-barrier structures

Tunnel spin polarization in a piezoelectric AlGaN/GaN double barrier structure is calculated. It is shown that the piezoelectric field and the spontaneous electrical polarization increase an efficiency of the tunnel spin injection. The relation between the electrical polarization and the spin orientation allows engineering a zero magnetic field spin injection manipulating the lattice-mismatch strain with an Al-content in the barriers.Comment: 13 pages, 6 figure

Superlattice in an interminiband resonance ac field

We discuss the properties of miniband electrons in a superlattice illuminated by a strong electromagnetic field. If the ac field is in resonance with a two-miniband superlattice, gaps in the quasienergy spectrum appear. The gap is proportional to the Bessel function and oscillates with the ac electric field. The resonant ac driving force makes the quasienergy spectrum tunable and may decrease the critical dc field for electrical domains to form.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87344/2/043505_1.pd

Quantitative structural mechanobiology of platelet-driven blood clot contraction.

Blood clot contraction plays an important role in prevention of bleeding and in thrombotic disorders. Here, we unveil and quantify the structural mechanisms of clot contraction at the level of single platelets. A key elementary step of contraction is sequential extension-retraction of platelet filopodia attached to fibrin fibers. In contrast to other cell-matrix systems in which cells migrate along fibers, the "hand-over-hand" longitudinal pulling causes shortening and bending of platelet-attached fibers, resulting in formation of fiber kinks. When attached to multiple fibers, platelets densify the fibrin network by pulling on fibers transversely to their longitudinal axes. Single platelets and aggregates use actomyosin contractile machinery and integrin-mediated adhesion to remodel the extracellular matrix, inducing compaction of fibrin into bundled agglomerates tightly associated with activated platelets. The revealed platelet-driven mechanisms of blood clot contraction demonstrate an important new biological application of cell motility principles

Patients with pemphigus vulgaris under pathology and on the background of prolonged use of high doses of glucocorticosteroid therapy – the possibility of influencing the glutathione system

Introduction. Pemphigus vulgaris (PV) is a life-threatening disease of the skin and mucous membranes that is associated with IgG antibodies that target several types of keratinocyte antigens and cause epidermal lysis (acantholysis) via intracellular signaling that activates apoptotic enzymes (apoptolysis).The aim of the study was to increase the effectiveness of treatment of patients with PV with the substantiation and development of modern methods of corrective therapy based on the study of indicators of changes in the balance of the thiol-disulfide system in the body of patients under pathological conditions and with prolonged use of high doses of glucocorticosteroid hormones (GCS).Materials and research methods. There were examined 30 patients with PV (4 men and 26 women), who were hospitalized in KU «Zaporizhzhya Regional Skin and Venereal Clinical Dispensary» ZOR, Zaporizhzhia. At the time of observation, most of the patients were aged 61-70 years. As a comparison group, 20 practically healthy people were examined, constituting a control group.Our studies were four-phase: before treatment; 2-3 weeks of maximum doses of glucocorticosteroids (stage I); 1.5-2 months before discharge from the hospital, when the patient was gradually reduced dose of systemic glucocorticosteroids and the selection of the optimal daily dose (stage II); after 5-6 months, when doses of hormones were minimal (2-3 tablets) in the absence of clinical manifestations of vesicles (stage III).Results. Our pathogenetic therapy by GCS significantly led to an increase in the level of reduced glutathione (GSH), so in particular after the third treatment stage it was at 1.52 ± 0.13 mkm / mg protein, exceeding the same rate of the first and second stages of GCS administration by 87.65 and 61.70%, respectively (p <0.05). The course of GCS therapy in patients with PV contributed to the fact that the level of reduced thiols increased significantly during each stage of therapy of the examined patients, in particular in the third stage of maintenance GCS therapy reduced thiols were determined at 15.64 ±1.23 mM / mg protein, exceeding this marker of the second stage by 36.95%, and the value of reduced thiols of the first stage by 83.78% (p <0.05). The value of reduced thiols of the group of patients with PV in the second stage was 11.42 ±1.08 mM / mg protein, and in the first stage – 8.51 ±0.92 mM / mg protein, the percentage difference between these therapeutic stages was determined in 34.19% (p <0.05).Prescribing systemic GCS to patients with PV for three stages led to the restoration of the balance of the thiol-disulfide system in patients, which manifested itself in the form of a decrease in markers: oxidized glutathione and oxidized thiols; and also in the form of an increase in the level of markers of restorative processes – glutathione reductase, glutathione peroxidase, reduced glutathione, reduced thiols, exerting a systemic positive effect on the course of the pathological process, which was reflected both in the normalization of laboratory parameters in patients and clinically in the form of stable remission.Conclusion. GCS therapy helps to normalize the activity of the antioxidant system of the human body under conditions of PV pathology, which prevents deprivation of the glutathione chain of the thiol-disulfide system during activation of oxidative and nitrosative stress processes and prevents the development of decompensation of the antioxidant system as a whole with the development of damage to key cells and target organs

Weak antilocalization and zero-field electron spin splitting in AlGaN/AlN/GaN heterostructures with a polarization induced two-dimensional electron gas

Spin-orbit coupling is studied using the quantum interference corrections to conductance in AlGaN/AlN/GaN two-dimensional electron systems where the carrier density is controlled by the persistent photoconductivity effect. All the samples studied exhibit a weak antilocalization feature with a spin-orbit field of around 1.8 mT. The zero-field electron spin splitting energies extracted from the weak antilocalization measurements are found to scale linearly with the Fermi wavevector with an effective linear spin-orbit coupling parameter 5.5x10^{-13} eV m. The spin-orbit times extracted from our measurements varied from 0.74 to 8.24 ps within the carrier density range of this experiment.Comment: 16 pages, 4 figure