124 research outputs found
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 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 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 "-state", where the sign alternates, corresponding to a phase difference
of 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
located at alternating positions along the ladder and with dimerization
. For interchain coupling and , we find normalized
plateaux at starting at zero field and (saturation), while when
is columnar, another extra plateau at shows up. For
, when we find no plateau while for
we find four plateaux at . 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
states. For the same case we find that the temperature-induced
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 . 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 direction. In this case the condensate penetrates the F
layers over a short length determined by the exchange energy . If
the magnetizations are not collinear the triplet component has, in
addition to the zero projection, the projections . 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 (spin-orbit interaction limits this length). If the thickness
of the F layers is much larger than , 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 . 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
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