Current-phase relation in Josephson junction coupled with a magnetic dot

The current-phase relation (CPR) for a short Josephson junction placed in the nonuniform field of a small ferromagnetic particle is studied. The effect of the particle produced on the junction appears to be strong due to the formation of the pair of oppositely directed Abrikosov vortices which pierce the thin film superconducting electrode and cause a small--scale inhomogeneity of Josephson phase difference. The induced phase difference inhomogeneity is shown to result in the nonzero fixed phase drop $\phi_0$ across the junction. The equilibrium value $\phi_0$ corresponding to the ground state of the junction depends the configuration of the vortex--antivortex pair. The possibility to tune the ground state phase difference $\phi_0$ is discussed.Comment: 6 pages, 5 figure

Epitaxy, stoichiometry, and magnetic properties of Gd-doped EuO films on YSZ (001)

We have succeeded in preparing high-quality Gd-doped single-crystalline EuO films. Using Eu-distillation-assisted molecular beam epitaxy and a systematic variation in the Gd and oxygen deposition rates, we have been able to observe sustained layer-by-layer epitaxial growth on yttria-stabilized cubic zirconia (001). The presence of Gd helps to stabilize the layer-by-layer growth mode. We used soft x-ray absorption spectroscopy at the Eu and Gd M4,5 edges to confirm the absence of Eu3+ contaminants and to determine the actual Gd concentration. The distillation process ensures the absence of oxygen vacancies in the films. From magnetization measurements we found the Curie temperature to increase smoothly as a function of doping from 70 K up to a maximum of 125 K. A threshold behavior was not observed for concentrations as low as 0.2%.Comment: 8 pages, 9 figure

Frequency of vitreoretinal adhesion in retinal vessels in patients with axial myopia of different age groups

Purpose. Finding out the frequency and structures posterior vitreous detachment (PVD), the proportion of local vitreoretinal adhesion in topographical zones of large retinal vessels of posterior pole of the eye in patients of different age groups with axial myopia.Material and methods. Clinical material was 82 eyes (41 patients). The age of patients ranged from 18 to 70 years. According to the age category, which is determined by the WHO classification, all patients were divided into 3 groups. The 1st group (18-44 years old) included 12 people (24 eyes); the 2nd group (45–59 years old) included 14 people (28 eyes); the 3rd group (60–74 years old) included 15 people (30 eyes).Results. In the 1st group PVD was not detected in 11 eyes (45.8%); in 13 eyes there were various variants of PVD (54.2%). In the 2nd group PVD was not detected in 9 eyes (32.1%); in 19 eyes there were various variants of PVD (67.9%). In the 3rd group PVD was not detected in 5 eyes (16.7%); in 25 eyes (83.3%) there were various variants of PVD. In this group, there was statistically significant predominance of partial PVD with fixation of the posterior hyaloid membrane to inner limiting membrane (PHM to ILM).Conclusion. In the group of elderly patients with axial myopia (60– 75 years), statistically significant increase in incidence of local adhesion of PHM to ILM in the projection of large retinal vessels was revealed in comparison with young and middle-aged groups (10 cases versus 1 and 2, respectively, p<0.05). This feature must be taken in examination and subsequent management of these patients

Abrikosov vortex escape from a columnar defect as a topological electronic transition in vortex core

We study microscopic scenario of vortex escape from a columnar defect under the influence of a transport current. For defect radii smaller than the superconducting coherence length the depinning process is shown to be a consequence of two subsequent topological electronic transitions in a trapped vortex core. The first transition at a critical current $j_L$ is associated with the opening of Fermi surface segments corresponding to the creation of a vortex--antivortex pair bound to the defect. The second transition at a certain current $j_d > j_L$ is caused by merging of different Fermi surface segments, which accompanies the formation of a freely moving vortex.Comment: 5 pages, 4 figure

Fine-tuning of Silica Coating Procedure for Preparation of Biocompatible and Bright Pbs/Sio2 Qds

Near-infrared semiconductor PbS quantum dots (QDs) with emission in biological transparency window are promising material for in vivo biolabelling and deep-tissue imaging of biological specimen. Among various approaches that render initially hydrophobic and toxic QDs biocompatible, the growth of a silica shell on the QD surface represents an efficient method to minimize QD toxicity. Nevertheless, it is important to preserve QDs emission properties after the silica coating procedure. Here we report on the optimal parameters of this procedure which allow to obtain a stable silica shell and maintain the optical properties of initial PbS QDs. Furthermore, we show that PbS QDs with the optimal SiO2 shell retain their luminescence quantum yield even after condensation into a solid film. Thus, our procedure can become a basis in development of bright, receptor-targeted NIR fluorescent probes for in vivo tumor imaging. Keywords: quantum dot, SiO2 shell, bioimagin

Little-Parks Oscillations in Hybrid Ferromagnet-Superconductor Systems

On the basis of of linearized Usadel equations we consider superconductivity nucleation in multiply connected mesoscopic superconductor/ferromagnet hybrids such as thin-walled superconducting cylinders placed in electrical contact with a ferromagnetic metal. We study the interplay between the oscillations of $T_c$ due to the Little--Parks effect and the oscillations due to the exchange field. We demonstrate that the exchange field provokes the switching between the superconducting states with different vorticities and this may result in the increase the critical temperature of the superconducting transition in the magnetic field. Moreover we analyse the influence of the S/F transparency on the realisation of the states with higher vorticities.Comment: 7 pages, 4 figure

Armenia and Belarus: caught between the EU's and Russia's conditionalities?

This article looks into Armenia's and Belarus’ engagement with the European Union's (EU) and Russia's conditionalities, the two EU Eastern Partnership (EaP) countries that are also members of the Russia-led Eurasian Economic Union (EAEU). While paying attention to political, economic (including energy and technical) as well as security dimensions of the EU's and Russia's approaches, as proposed in the present special section, the article demonstrates that the conditionalities extended by the EU and Russia to the two countries in question have differed. In their turn, Armenia and Belarus have reacted differently to Russia's and the EU's conditionalities. Against the backdrop of the changing significance ascribed to both the EU's and Russia's policies towards their common neighbourhood since the 1990s, the present contribution identifies and analyses factors that account for the diverging positions of Armenia and Belarus, including the type of regime, the geopolitical considerations, the stakes in the economic and energy spheres and the predisposition to integration. The article shows that in the resulting complex context, Armenia and Belarus have been able to influence the shape and content of the EU's and Russia's conditionalities, although in a different way and to a different extent.Ministry of Education and Science (UID/CPO/ 00758/2013

Биометрические факторы риска возникновения острого приступа глаукомы

PURPOSE. To assess the prognostic significance of the LAF coefficient (Lens thickness/Axial length factor) as a risk factor for acute glaucoma attack in anatomically short eyes of Europeans.METHODS. Group 1 consisted of 24 patients (48 eyes) with axial hyperopia. Group 2 included 24 patients (48 eyes) with primary closure of the anterior chamber angle. Group 3 — 17 patients (34 eyes) with initial stage of primary angleclosure glaucoma. Group 4 — 35 patients (35 eyes) with an acute attack of glaucoma. The studied groups did not differ in age (p=0.97) and gender (p=0.28). Lens thickness and axial length (AL) were measured by A-scan with calculation of the LAF coefficient.RESULTS. The LAF coefficient in group 4 (acute attack) was statistically significantly higher than in the other three groups. The best separation of groups 1 and 4 was seen in LAF coefficient compared to lens thickness and AL with sensitivity, specificity and the area under the curve (AUC) of 89%, 83% and 0.9, respectively. LAF coefficient values greater than 2.332 in patients with short AL are objectively associated with high risk of acute attack of glaucoma. The average value of the LAF coefficient (2.528) observed in group 4 (acute attack of glaucoma) significantly exceeds these parameters in works of other authors, which may be associated with morphometric structural features of the eyes of Europeans compared to the eyes of Asians.CONCLUSION. The LAF coefficient provides better separation of group 1 and 4 in comparison with lens thickness and, especially, axial length. LAF coefficient values greater than 2.332 in eyes with short AL objectively indicate high risk of acute attack of glaucoma, as evidenced by high sensitivity, specificity, and AUC.ЦЕЛЬ. Оценить прогностическую значимость коэффициента LAF (Lens thickness/Axial length factor; фактор толщины хрусталика/осевой длины) в качестве фактора риска возникновения острого приступа глаукомы в анатомически коротких глазах европейцев.МЕТОДЫ. В группу 1 вошли 24 пациента (48 глаз) с осевой гиперметропией. В группу 2 — 24 пациента (48 глаз) с первичным закрытием угла передней камеры. В группу 3 — 17 пациентов (34 глаза) с начальной стадией первичной закрытоугольной глаукомы. В группу 4 — 35 пациентов (35 глаз) с острым приступом глаукомы. Исследуемые группы не отличались по возрасту (p=0,97) и полу (p=0,28). Толщина хрусталика (ТХ) и переднезадняя ось (ПЗО) измерялись с помощью А-сканирования с расчетом коэффициента LAF.РЕЗУЛЬТАТЫ. Коэффициент LAF в группе с острым приступом глаукомы был статистически значимо выше, чем в первых 3-х группах. Наилучшее разделение 1-й и 4-й групп обеспечивает показатель LAF по сравнению с показателями ТХ и ПЗО с чувствительностью, специфичностью и площадью под ROC-кривыми 89%, 83% и 90%, соответственно. Значения коэффициента LAF более 2,332 у пациентов с короткой ПЗО объективно ассоциировано с высоким риском возникновения острого приступа глаукомы. Полученное нами среднее значение коэффициента LAF в группе с острым приступом глаукомы (2,528) значительно превышает данные показатели в работах других авторов, что может быть обусловлено морфометрическими особенностями строения глаз европейцев по сравнению с глазами азиатов.ЗАКЛЮЧЕНИЕ. Коэффициент LAF обеспечивает лучшее разделение 1-й и 4-й групп по сравнению с показателями ТХ и, особенно, ПЗО. Значения коэффициента LAF более 2,332 в глазах с короткой ПЗО объективно свидетельствуют о высоком риске возникновения острого приступа глаукомы, что подтверждается высокой чувствительностью, специфичностью и данными ROC-анализа