Influence of spin filtering and spin mixing on the subgap structure of I-V characteristics in superconducting quantum point contact

The effect of spin filtering and spin mixing on the dc electric current for voltage biased magnetic quantum point contact with superconducting leads is theoretically studied. The I-V characteristics are calculated for the whole range of spin filtering and spin mixing parameters. It is found that with increasing of spin filtering the subharmonic step structure of the dc electric current, typical for low-transparency junction and junction without considerable spin filtering qualitatively changes. In the lower voltage region and for small enough spin mixing the peak structure arises. When spin mixing increases the peak subgap structure evolves to the step structure. The voltages where subharmonic gap features are located are found to be sensitive to the value of spin filtering. The positions of peaks and steps are calculated analytically and the evolution of the subgap structure from well-known tunnel limit to the large spin filtering case is explained in terms of multiple Andreev reflection (MAR) processes. In particular, it is found that for large spin filtering the subgap feature at $eV_k$ arises from $2k^{\rm th}$ and $(2k\pm 1)^{\rm th}$ order MAR processes, while in the tunnel limit the step at $eV_n$ is known to result from $n^{\rm th}$ order MAR process.Comment: 9 pages, 3 figure

Superconducting Junctions with Ferromagnetic, Antiferromagnetic or Charge-Density-Wave Interlayers

Spectra and spin structures of Andreev interface states and the Josephson current are investigated theoretically in junctions between clean superconductors (SC) with ordered interlayers. The Josephson current through the ferromagnet-insulator-ferromagnet interlayer can exhibit a nonmonotonic dependence on the misorientation angle. The characteristic behavior takes place if the pi state is the equilibrium state of the junction in the particular case of parallel magnetizations. We find a novel channel of quasiparticle reflection (Q reflection) from the simplest two-sublattice antiferromagnet (AF) on a bipartite lattice. As a combined effect of Andreev and Q reflections, Andreev states arise at the AF/SC interface. When the Q reflection dominates the specular one, Andreev bound states have almost zero energy on AF/ s-wave SC interfaces, whereas they lie near the edge of the continuous spectrum for AF/d-wave SC boundaries. For an s-wave SC/AF/s-wave SC junction, the bound states are found to split and carry the supercurrent. Our analytical results are based on a novel quasiclassical approach, which applies to interfaces involving itinerant antiferromagnets. Similar effects can take place on interfaces of superconductors with charge density wave materials (CDW), including the possible d-density wave state (DDW) of the cuprates.Comment: LT24 conference proceeding, 2 pages, 1 figur

Subharmonic Gap Structure in Superconductor/Ferromagnet/Superconductor Junctions

The behavior of dc subgap current in magnetic quantum point contact is discussed for the case of low-transparency junction with different tunnel probabilities for spin-up ($D_\uparrow$) and spin-down ($D_\downarrow$) electrons. Due to the presence of Andreev bound states $\pm \epsilon_0$ in the system the positions of subgap electric current steps $eV_n = (\Delta \pm \epsilon_0)/n$ are split at temperature $T \neq 0$ with respect to the nonmagnetic result $eV_n=2\Delta/n$. It is found that under the condition $D_\uparrow \neq D_\downarrow$ the spin current also manifests subgap structure, but only for odd values of $n$. The split steps corresponding to $n=1,2$ in subgap electric and spin currents are analytically calculated and the following steps are described qualitatively.Comment: 4 pages, 1 figure, minor stylistic changes, journal-ref adde

Nonequilibrium Transport in Superconductor/Ferromagnet/Superconductor Diffusive Junctions: Interplay between Proximity Effect and Ferromagnetism

The theory of the I-V characteristics in diffusive superconductor/weak ferromagnet/superconductor (SFS) junction is developed. We show that the exchange field $h$ of the ferromagnet manifests itself as an additional conductance peak at $eV \sim \Delta+h$ in the phase-coherent regime, when the Thouless energy is of the order of superconducting order parameter. The excess current exhibits non-monotonous dependence on the exchange field and non-trivial temperature behavior, which is strongly influenced by the temperature dependence of the exchange field.Comment: 5 pages, 2 figure

Phase diagrams of the diode effect in superconducting heterostructures

At present the superconducting diode effect (SDE) attracts a lot of attention due to new possibilities in the superconducting electronics. One of the possible realizations of the SDE is the implementation in superconducting hybrid structures. In this case the SDE is achieved by means of the proximity effect. However, the optimal conditions for the SDE quality factor in hybrid devices remain unclear. In this study we consider the Superconductor/Ferromagnet/Topological insulator (S/F/TI) hybrid device and investigate the diode quality factor at different parameters of the hybrid structure. Consequently, we reveal important parameters that have crucial impact on the magnitude of the SDE quality factor.</p

Josephson Current in S-FIF-S Junctions: Nonmonotonic Dependence on Misorientation Angle

Spectra and spin structures of Andreev interface states in S-FIF-S junctions are investigated with emphasis on finite transparency and misorientation angle between in-plane magnetizations of ferromagnetic layers in a three-layer interface. It is demonstrated that the Josephson current in S-FIF-S quantum point contacts can exhibit a nonmonotonic dependence on the misorientation angle. The characteristic behavior takes place, if the pi-state is the equilibrium state of the junction in the particular case of parallel magnetizations.Comment: 5 pages, 4 figure

Эффективность антисекреторных препаратов в раннем послеоперационном периоде у кардиохирургических больных

Objective. To compare the efficacy of antisecretory agents used to prevent early postoperative mucosal erosive and ulcerative lesions of the upper gastrointestinal tract (GIT) in patients undergone cardiac surgery under extracorporeal circulation (EC). The study was performed by stratification randomization. Sixty-three adult patients with acquired cardiac diseases who had undergone operations on the heart under EC were clinically and endoscopically examined. To prevent acute proximal GIT ulcerations in the early postoperative period, all the patients were given antisecretory agents: ^-histamine receptor blockers or proton pump inhibitors (PPI). A drug was chosen by the blind method (envelope one). One group (n=31) took ^-histamine receptor blockers, the other (n=32) received PPI (omeprazole). To examine the upper GIT mucosa and to determine gastric acid-producing function, esophagogastroduodenoscopy with parietal pH-metry and chromoscopy were performed on postoperative days 5 and 9. Analysis of the findings revealed acute erosive and ulcerative lesions in 12.7% of all the examinees only in the ^-blocker group. Suppressed hydrochloric acid was significantly pronounced in the PPI group, as evidenced by chromoscopy. In the H2-blocker and PPI groups, the mean gastric pH value was 2.4±1.0 and 5.5±06 (F=224 and 259, respectively; p=0.0001).Цель исследования — сравнение эффективности антисекреторных препаратов для профилактики эрозивно-яз-венных повреждений слизистой оболочки верхних отделов желудочно-кишечного тракта (ЖКТ) в раннем послеоперационном периоде у больных, перенесших операции на сердце в условиях искусственного кровообращения (ИК). Исследование выполнялось методом стратификационной рандомизации. Проведено клиническое и эндоскопическое обследование 63 взрослых пациентов с приобретенными пороками сердца, которые перенесли операции на сердце в условиях ИК. С целью профилактики острых изъязвлений слизистой оболочки проксимальных отделов ЖКТ в раннем послеоперационном периоде всем больным назначали антисекреторные препараты: блокаторы Н2-гистаминовых рецепторов или ингибиторы протонной помпы (ИПП). Выбор препарата проводился «слепым» методом (метод конвертов). В результате одна группа пациентов (31) получала ^-блокаторы (фамотидин), другая (32) — ИПП (омепразол). Для исследования состояния слизистой оболочки верхних отделов ЖКТ и определения кислотопродуцирующей функции желудка на 5-е и 9-е сутки послеоперационного периода проводили ЭГДС с пристеночной рН-метрией и хромоскопией. Анализ полученных данных выявил, что острые эрозивно-язвенные повреждения были выявлены у 12,7% от общего количества обследованных больных, причем только в группе больных, принимавших Н2-блокаторы. Подавление секреции соляной кислоты было достоверно выраженным в группе пациентов, принимавших ИПП, что подтверждалось результатами хромоскопии. Среднее значение внутрижелудочного pH в группе Н2-блокаторов на 9-е сутки составило 2,4±1,0, а в группе ИПП — 5,5±0,6 (F=224,259, p=0,0001)

Эффективность и безопасность применения цепэгинтерферона альфа-2b в составе двойной схемы (цепэгинтерферон альфа 2b и рибавирин) противовирусной терапии у пациентов с хроническим гепатитом С, генотипами 2 и 3. Опыт реальной клинической практики

The objective: to analyze the experience of use of cepeginterferonalfa-2b and ribavirin in patients with chronic hepatitis C genotypes 2 and 3 in clinical practice, to evaluate the efficacy, safety and tolerability of this treatment regimen.Materials and methods. From 2013 to 2016 a total of 73 patients with chronic hepatitis C (CHC) received antiviral therapy with cepeginterferon alfa 2b (cePEG-IFN alfa-2b) and ribavirin in the Center for Gastroenterology and Hepatology of FSBE «Vishnevsky Third Military Clinical Hospital» of Russian Ministry of Defence. Treatment efficacy was assessed by the rate of sustained virologic response (SVR) on 24 week after completion of antiviral therapy. All cases of deterioration of the patient’s condition and laboratory abnormalities were registered throughout the treatment period and follow up. Severity of adverse events was assessed in accordance with the classification of CTCAE (Common Terminology Criteria for Adverse Events).Results. 73 CHC patients genotype 2/3 received cePEGIFN alfa-2b 1.5 μg/kg/week and ribavirin 800-1400 mg/day based on body weight for 24 weeks. SVR 24 was registered in 94,7% (n=54) of patients with HCV genotype 3 and in 93,7% (n =15) patients with genotype 2. During the first 12 weeks of therapy the normalization of serum transaminase activities was registered. All adverse events were typical for interferon/ribavirin treatment regimen.Conclusion. According to our data the use of double treatment regimen (CePEG-IFN alfa-2b and ribavirin) is reasonable in patients who don’t have negative predictive factors of response to IFN-based therapy. The SVR rate in this group of patients was 94.5%.Цель: проанализировать опыт применения цепэгинтерферона альфа-2b в составе двойной схемы (цепэгинтерферон альфа-2b и рибавирин) противовирусной терапии у пациентов с хроническим гепатитом С, генотипами 2 и 3 в клинической практике; оценить эффективность, безопасность и переносимость лечения.Материалы и методы. С февраля 2013 г. по март 2016 г. в Центре гастроэнтерологии и гепатологии 3-го Центрального военного клинического госпиталя им. А.А. Вишневского 73 пациента с хроническим гепатитом С (ХГС) получали противовирусную терапию (ПВТ) с применением двойной схемы, включающей цепэгинтерферон альфа-2b (цеПЭГ-ИФН альфа-2b) и рибавирин. Эффективность лечения оценивалась по частоте достижения вирусологического ответа через 24 недели после окончания терапии – устойчивый вирусологический ответ (УВО24). В процессе лечения фиксировались все случаи нарушения самочувствия пациентов и отклонений от нормы в лабораторных тестах крови. Выраженность нежелательных явлений оценивалась в соответствии с классификацией СТСАЕ (Common Terminology Criteria for Adverse Events).Результаты. 73 пациента с ХГС, генотипом 2 и 3, получали цеПЭГ-ИФН альфа-2b 1,5 мкг/кг/нед. и рибавирин 800–1400 мг/сут в зависимости от массы тела в течение 24 недель. УВО 24 был зафиксирован у 94,7% (n=54) пациентов с 3 генотипом HCV и у 93,7% (n=15) пациентов с 2 генотипом. В течение первых 12 недель терапии у большинства пациентов отмечена нормализация активности сывороточных трансаминаз. Все наблюдавшиеся нежелательные явления были характерны для интерферона и рибавирина.Заключение. В работе представлен опыт применения комбинации цеПЭГ-ИФН альфа-2b и рибавирина у пациентов с 2 и 3 генотипом HCV. Согласно полученным нами данным, при применении цеПЭГ-ИФН альфа-2b и рибавирина у пациентов, не имеющих предикторов неблагоприятного исхода терапии, частота УВО составила 94,5%

The importance of the cellular stress response in the pathogenesis and treatment of type 2 diabetes

Organisms have evolved to survive rigorous environments and are not prepared to thrive in a world of caloric excess and sedentary behavior. A realization that physical exercise (or lack of it) plays a pivotal role in both the pathogenesis and therapy of type 2 diabetes mellitus (t2DM) has led to the provocative concept of therapeutic exercise mimetics. A decade ago, we attempted to simulate the beneficial effects of exercise by treating t2DM patients with 3 weeks of daily hyperthermia, induced by hot tub immersion. The short-term intervention had remarkable success, with a 1 % drop in HbA1, a trend toward weight loss, and improvement in diabetic neuropathic symptoms. An explanation for the beneficial effects of exercise and hyperthermia centers upon their ability to induce the cellular stress response (the heat shock response) and restore cellular homeostasis. Impaired stress response precedes major metabolic defects associated with t2DM and may be a near seminal event in the pathogenesis of the disease, tipping the balance from health into disease. Heat shock protein inducers share metabolic pathways associated with exercise with activation of AMPK, PGC1-a, and sirtuins. Diabetic therapies that induce the stress response, whether via heat, bioactive compounds, or genetic manipulation, improve or prevent all of the morbidities and comorbidities associated with the disease. The agents reduce insulin resistance, inflammatory cytokines, visceral adiposity, and body weight while increasing mitochondrial activity, normalizing membrane structure and lipid composition, and preserving organ function. Therapies restoring the stress response can re-tip the balance from disease into health and address the multifaceted defects associated with the disease