Magnetic-field-induced supercurrent enhancement in hybrid superconductor/magnetic metal structures

The dc transport properties of the (S/M)I(M/S) tunnel structure - proximity coupled superconductor (S) and magnetic (M) layers separated by an insulator (I) - in a parallel magnetic field have been investigated. We choose for the M metal the one in which the effective magnetic interaction, whether it arises from direct exchange interaction or due to configuration mixing, aligns spins of the conducting electrons antiparallel to the localized spins of magnetic ions. For tunnel structures under consideration, we predict that there are the conditions when the destructive action of the internal and applied magnetic fields on Cooper pairs is weakened and the increase of the applied magnetic field causes the field-induced enhancement of the tunnel critical current. The experimental realization of the novel interesting effect of the interplay between superconducting and magnetic orders is also discussed.Comment: 6 pages 2 figure

Antiferromagnetic order and dielectric gap within the vortex core of antiferromagnetic superconductor

The structure of a superconducting vortex has been studied theoretically for a dirty antiferromagnetic superconductor (AFSC), modelling an AFSC as a doped semi-metal with s-wave superconducting pairing and antiferromagnetic (dielectric) interaction between electrons (holes). It is also supposed that the quasiparticles dispersion law possesses the property of nesting. The distribution of the superconducting and magnetic order parameters near the vortex core is calculated. It is shown that the antiferromagnetic order, been suppressed at large distances, is restored around the superconducting flux and the vortex core is in fact insulating and antiferromagnetic, in stark contrast to the normal metal cores of traditional superconductors. Moreover, our model calculations predict that as the temperature decreases the flux region of the superconductivity and antiferromagnetism coexistence increases.Comment: 9 pages, 3 Postscript figures,NATO Advanced Research Workshop on "Vortex dynamics in superconductors and other complex systems" Yalta, Crimea, Ukraine, 13-17 September 200

Oil spill problems and sustainable response strategies through new technologies

Crude oil and petroleum products are widespread water and soil pollutants resulting from marine and terrestrial spillages. International statistics of oil spill sizes for all incidents indicate that the majority of oil spills are small (less than 7 tonnes). The major accidents that happen in the oil industry contribute only a small fraction of the total oil which enters the environment. However, the nature of accidental releases is that they highly pollute small areas and have the potential to devastate the biota locally. There are several routes by which oil can get back to humans from accidental spills, e.g. through accumulation in fish and shellfish, through consumption of contaminated groundwater. Although advances have been made in the prevention of accidents, this does not apply in all countries, and by the random nature of oil spill events, total prevention is not feasible. Therefore, considerable world-wide effort has gone into strategies for minimising accidental spills and the design of new remedial technologies. This paper summarizes new knowledge as well as research and technology gaps essential for developing appropriate decision-making tools in actual spill scenarios. Since oil exploration is being driven into deeper waters and more remote, fragile environments, the risk of future accidents becomes much higher. The innovative safety and accident prevention approaches summarized in this paper are currently important for a range of stakeholders, including the oil industry, the scientific community and the public. Ultimately an integrated approach to prevention and remediation that accelerates an early warning protocol in the event of a spill would get the most appropriate technology selected and implemented as early as possible-the first few hours after a spill are crucial to the outcome of the remedial effort. A particular focus is made on bioremediation as environmentally harmless, cost-effective and relatively inexpensive technology. Greater penetration into the remedial technologies market depends on the harmonization of environment legislation and the application of modern laboratory techniques, e.g. ecogenomics, to improve the predictability of bioremediation

Layered ferromagnet-superconductor structures: the π\pi state and proximity effects

We investigate clean mutilayered structures of the SFS and SFSFS type, (where the S layer is intrinsically superconducting and the F layer is ferromagnetic) through numerical solution of the self-consistent Bogoliubov-de Gennes equations for these systems. We obtain results for the pair amplitude, the local density of states, and the local magnetic moment. We find that as a function of the thickness $d_F$ of the magnetic layers separating adjacent superconductors, the ground state energy varies periodically between two stable states. The first state is an ordinary "0-state", in which the order parameter has a phase difference of zero between consecutive S layers, and the second is a "$\pi$-state", where the sign alternates, corresponding to a phase difference of $\pi$ between adjacent S layers. This behavior can be understood from simple arguments. The density of states and the local magnetic moment reflect also this periodicity.Comment: 12 pages, 10 Figure

Alternating-Spin Ladders in a Magnetic Field: New Magnetization Plateaux

We study numerically the formation of magnetization plateaux with the Lanczos method in 2-leg ladders with mixed spins of magnitudes $(S_1,S_2)=(1,1/2)$ located at alternating positions along the ladder and with dimerization $\gamma$. For interchain coupling $J'>0$ and $\gamma=0$, we find normalized plateaux at $m=1/3$ starting at zero field and $m=1$ (saturation), while when $\gamma \ne 0$ is columnar, another extra plateau at $m=2/3$ shows up. For $J'<0$, when $\gamma<\gamma_c(J')$ we find no plateau while for $\gamma>\gamma_c(J')$ we find four plateaux at $m=0,1/3,2/3,1$. We also apply several approximate analytical methods (Spin Wave Theory, Low-Energy Effective Hamiltonians and Bosonization) to understand these findings and to conjeture the behaviour of ferrimagnetic ladders with a bigger number of legs.Comment: REVTEX file, 7 pages, 6 eps Figure

Effectiveness of immunobloting method in syphilis differential diagnostics in pregnancy

168 pregnant women suspected to be infected with syphilis were observed within this research. To prove the presence of antibody in whey blood to antigenes Treponema pallidum we used sets recomBlot Treponema IgM and recomBlot Treponema IgG («Microgen», Germany). In immunological observations the following indexes were included defining number of lymphocyte subpopulations (CD3+ -, CD4+ -, CD8+ -, CD16+ – , CD19+ и CD25+ – lymphocyte) and level in blood serum Interleukin-1β, Interleukin-2, Interleukin-4, Interleukin-8 и INF-γ. Treponema tests in 100% of cases showed positive results, regardless of patients’ category. An examination of pregnant women with serum resistance the immunobloting sensitivity for detecting IgG-antibodies was 61,6%. In 38,4% of cases bloting showed uncertain results, because it detected antibodies to only one or two out of 5 treponemnyh antigens. Level of INF-γ for pregnant women with serum resistance increases, this reflects predominance of immune regulation of Th-1 type. Based on the results we offer general scheme of dealing with pregnant patients with suspected syphilis. These results can be used for differential diagnosis of latent syphilis, and serum resistance

Josephson effect in double-barrier superconductor-ferromagnet junctions

We study the Josephson effect in ballistic double-barrier SIFIS planar junctions, consisting of bulk superconductors (S), a clean metallic ferromagnet (F), and insulating interfaces (I). We solve the scattering problem based on the Bogoliubov--de Gennes equations and derive a general expression for the dc Josephson current, valid for arbitrary interfacial transparency and Fermi wave vectors mismatch (FWVM). We consider the coherent regime in which quasiparticle transmission resonances contribute significantly to the Andreev process. The Josephson current is calculated for various parameters of the junction, and the influence of both interfacial transparency and FWVM is analyzed. For thin layers of strong ferromagnet and finite interfacial transparency, we find that coherent (geometrical) oscillations of the maximum Josephson current are superimposed on the oscillations related to the crossover between 0 and $\pi$ states. For the same case we find that the temperature-induced $0-\pi$ transition occurs if the junction is very close to the crossovers at zero temperature.Comment: 13 pages, 6 figure

Manifestation of triplet superconductivity in superconductor-ferromagnet structures

We study proximity effects in a multilayered superconductor/ferromagnet (S/F) structure with arbitrary relative directions of the magnetization ${\bf M}$. If the magnetizations of different layers are collinear the superconducting condensate function induced in the F layers has only a singlet component and a triplet one with a zero projection of the total magnetic moment of the Cooper pairs on the ${\bf M}$ direction. In this case the condensate penetrates the F layers over a short length $\xi_J$ determined by the exchange energy $J$. If the magnetizations ${\bf M}$ are not collinear the triplet component has, in addition to the zero projection, the projections $\pm1$. The latter component is even in the momentum, odd in the Matsubara frequency and penetrates the F layers over a long distance that increases with decreasing temperature and does not depend on $J$ (spin-orbit interaction limits this length). If the thickness of the F layers is much larger than $\xi_J$, the Josephson coupling between neighboring S layers is provided only by the triplet component, so that a new type of superconductivity arises in the transverse direction of the structure. The Josephson critical current is positive (negative) for the case of a positive (negative) chirality of the vector ${\bf M}$. We demonstrate that this type of the triplet condensate can be detected also by measuring the density of states in F/S/F structures.Comment: 14 pages; 9 figures. Final version, to be published in Phys. Rev.

Interrelations between viral load and cellular immunity in patients with COVID-19 of varying severity

Assessment of viral load levels in various biological samples taken from the respiratory tract can be an indicator of an ongoing process of active viral replication and may be used to monitor severe respiratory viral infections. The study of the relationship between SARS-CoV-2 viral load and immunological laboratory parameters is an important step in the search for clinical markers of COVID-19.The aim of this research was to quantify viral load in patients with COVID-19 and to identify the relation-ship between viral load and changes in the parameters of the cellular component of the immune system.A laboratory examination was carried out on 74 patients diagnosed with COVID-19, they were divided into 3 groups based on the severity of the disease: mild, moderate, severe. Total viral load in clinical samples was determined by the number of SARS-CoV-2 RNA copies per 100 copies of the reference RNaseP gene.     A comprehensive assessment of the cellular component of the immune system was performed using flow cytometry and direct monoclonal antibodies, and the IL-6, and C-reactive protein concentrations were determined.We revealed a relationship between the development of serious clinical conditions in the patients with COVID-19, and the levels of viral load. High levels of viral RNA in biological samples correlate with main indicators of the T cell component of the immune system associated with disease severity. In a subgroup of patients with an extremely high viral load, strong positive correlations were found between the relative numbers of cytotoxic lymphocytes (CD3+CD8+), activated T lymphocytes (CD3+HLA-DR+), as well as absolute and relative numbers of activated B lymphocytes and NK cells (CD3-CD25+).Laboratory monitoring of the cellular component of the immune system, along with the assessment of viral loads, should improve  early assessment of clinical condition in the patients with COVID-19. Changes   in expression levels of activation markers on immune cells can be potentially viewed as indicators of recovery during COVID-19

ЭФФЕКТИВНОСТЬ ИММУНОБЛОТИНГА ПРИ ДИФФЕРЕНЦИАЛЬНОЙ ДИАГНОСТИКЕ СИФИЛИСА У БЕРЕМЕННЫХ

168 pregnant women suspected to be infected with syphilis were observed within this research. To prove the presence of antibody in whey blood to antigenes Treponema pallidum we used sets recomBlot Treponema IgM and recomBlot Treponema IgG («Microgen», Germany). In immunological observations the following indexes were included defining number of lymphocyte subpopulations (CD3+ -, CD4+ -, CD8+ -, CD16+ – , CD19+ и CD25+ – lymphocyte) and level in blood serum Interleukin-1β, Interleukin-2, Interleukin-4, Interleukin-8 и INF-γ. Treponema tests in 100% of cases showed positive results, regardless of patients’ category. An examination of pregnant women with serum resistance the immunobloting sensitivity for detecting IgG-antibodies was 61,6%. In 38,4% of cases bloting showed uncertain results, because it detected antibodies to only one or two out of 5 treponemnyh antigens. Level of INF-γ for pregnant women with serum resistance increases, this reflects predominance of immune regulation of Th-1 type. Based on the results we offer general scheme of dealing with pregnant patients with suspected syphilis. These results can be used for differential diagnosis of latent syphilis, and serum resistance.Обследованы 168 беременных с подозрением на сифилис. Для подтверждения наличия антител в сыворотке крови к антигенам Treponema pallidum в работе использовались наборы recomBlot Treponema IgM и recomBlot Treponema IgG («Microgen», Германия). В иммунологический комплекс обследования также входили следующие показатели: количества субпопуляций лимфоцитов (CD3+ -, CD4+ -, CD8+ -, CD16+ – , CD19+ и CD25+ – лимфоциты), а также определение уровней сывороточных интерлейкина-1β (ИЛ-1β), интерлейкина-2 (ИЛ-2), интерлейкина-4 (ИЛ-4), интерлейкина-8 (ИЛ-8) и ИНФ-γ. Трепонемные серологические тесты в 100% случаев демонстрировали положительный результат, независимо от категории обследуемых. При обследовании беременных с серорезистентностью чувствительность иммуноблотинга при выявлении IgG-антител составила 61,6%. В 38,4% случаев метод иммуноблотинга продемонстрировал сомнительные результаты, так как выявлял антитела только к одному или двум из 5 трепонемных антигенов. У беременных с диагнозом «серорезистентность» выявлено повышение уровня ИНФ-γ, что может отражать преобладание иммунорегуляции по Th-1 типу. Предлагается общая схема ведения беременных пациенток с подозрением на сифилис. Полученные результаты можно использовать в дифференциальной диагностике скрытого сифилиса и серологической резистентности