Coherent spin relaxation in molecular magnets

Numerical modelling of coherent spin relaxation in nanomagnets, formed by magnetic molecules of high spins, is accomplished. Such a coherent spin dynamics can be realized in the presence of a resonant electric circuit coupled to the magnet. Computer simulations for a system of a large number of interacting spins is an efficient tool for studying the microscopic properties of such systems. Coherent spin relaxation is an ultrafast process, with the relaxation time that can be an order shorter than the transverse spin dephasing time. The influence of different system parameters on the relaxation process is analysed. The role of the sample geometry on the spin relaxation is investigated.Comment: Latex file, 22 pages, 7 figure

Nonlinear spin relaxation in strongly nonequilibrium magnets

A general theory is developed for describing the nonlinear relaxation of spin systems from a strongly nonequilibrium initial state, when, in addition, the sample is coupled to a resonator. Such processes are characterized by nonlinear stochastic differential equations. This makes these strongly nonequilibrium processes principally different from the spin relaxation close to an equilibrium state, which is represented by linear differential equations. The consideration is based on a realistic microscopic Hamiltonian including the Zeeman terms, dipole interactions, exchange interactions, and a single-site anisotropy. The influence of cross correlations between several spin species is investigated. The critically important function of coupling between the spin system and a resonant electric circuit is emphasized. The role of all main relaxation rates is analyzed. The phenomenon of self-organization of transition coherence in spin motion, from the quantum chaotic stage of incoherent fluctuations, is thoroughly described. Local spin fluctuations are found to be the triggering cause for starting the spin relaxation from an incoherent nonequilibrium state. The basic regimes of collective coherent spin relaxation are studied.Comment: Latex file, 31 page

Origin of Pure Spin Superradiance

The question addressed in this paper is: What originates pure spin superradiance in a polarized spin system placed inside a resonator? The term "pure" means that no initial coherence is imposed on spins, and its appearance manifests a purely self-organized collective effect. The consideration is based on a microscopic model with dipole spin interactions. An accurate solution of evolution equations is given. The results show that the resonator Nyquist noise does not play, contrary to the common belief, any role in starting spin superradiance, but the emergence of the latter is initiated by local spin fluctuations. The decisive role of nonsecular dipole interactions is stressed.Comment: 1 file, 13 pages, RevTe

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented

Scattering of slow-light gap solitons with charges in a two-level medium

The Maxwell-Bloch system describes a quantum two-level medium interacting with a classical electromagnetic field by mediation of the the population density. This population density variation is a purely quantum effect which is actually at the very origin of nonlinearity. The resulting nonlinear coupling possesses particularly interesting consequences at the resonance (when the frequency of the excitation is close to the transition frequency of the two-level medium) as e.g. slow-light gap solitons that result from the nonlinear instability of the evanescent wave at the boundary. As nonlinearity couples the different polarizations of the electromagnetic field, the slow-light gap soliton is shown to experience effective scattering whith charges in the medium, allowing it for instance to be trapped or reflected. This scattering process is understood qualitatively as being governed by a nonlinear Schroedinger model in an external potential related to the charges (the electrostatic permanent background component of the field).Comment: RevTex, 14 pages with 5 figures, to appear in J. Phys. A: Math. Theo

Casimir-Polder forces: A non-perturbative approach

Within the frame of macroscopic QED in linear, causal media, we study the radiation force of Casimir-Polder type acting on an atom which is positioned near dispersing and absorbing magnetodielectric bodies and initially prepared in an arbitrary electronic state. It is shown that minimal and multipolar coupling lead to essentially the same lowest-order perturbative result for the force acting on an atom in an energy eigenstate. To go beyond perturbation theory, the calculations are based on the exact center-of-mass equation of motion. For a nondriven atom in the weak-coupling regime, the force as a function of time is a superposition of force components that are related to the electronic density-matrix elements at a chosen time. Even the force component associated with the ground state is not derivable from a potential in the ususal way, because of the position dependence of the atomic polarizability. Further, when the atom is initially prepared in a coherent superposition of energy eigenstates, then temporally oscillating force components are observed, which are due to the interaction of the atom with both electric and magnetic fields.Comment: 23 pages, 3 figures, additional misprints correcte

Неотложная травматология в НИИ скорой помощи им. Н.В. Склифосовского: история и современность

The purpose of this work was to study the history of the development of traumatology-orthopedics at the N.V. Sklifosovsky Research Institute for Emergency Medicine.Traumatology as an independent discipline began to form at the N.V. Sklifosovsky Research Institute for Emergency Medicine during the reign of Professor S.S. Yudin (chief surgeon since 1928), who invited the famous Argentinean traumatologist-orthopedist Professor Lelio Zeno to work at the institute.In 1932, the trauma department of the N.V. Sklifosovsky Research Institute for Emergency Medicine was headed by Professor V.V. Gorinevskaya. She organized a 100-bed trauma clinic for the treatment of injuries to the head, spine, limbs, chest and abdominal cavity. She is rightfully considered one of the founders of trauma science in the USSR.With the development of traumatology and orthopedics as an independent specialty in 1961, two clinics were formed at the institute. The first trauma clinic was run by Dr. med. sciences professor I.I. Sokolov. The second clinic was headed by Dr. med. Sci. P.N. Petrov.In 1971, Dr. med. Professor, Honored Scientist of the Russian Federation, Academician of the Russian Academy of Medical and Technical Sciences of the Russian Federation V.P. Okhotsky was appointed the head of the traumatological service of the institute and the chief traumatologist of Moscow (from 1971 to 2001). With his active participation in Moscow, the reorganization of outpatient care was completed, work was widely launched on the medical aspects of the prevention of road traffic injuries and the introduction into practice of the most rational methods of diagnosis and treatment of patients with injuries of the musculoskeletal system. In the N.V. Sklifosovsky Research Institute for Emergency Medicine A.G. Suvalyan introduced the method of intramedullary osteosynthesis of long tubular bones (humerus, femur and tibia). Under the guidance of prof. V.P. Okhotsky the dissertation researches of A.G. Suvalyan, M.A. Suvalyan and S.S. Myakota were carried out. The expediency of early surgical intervention on the extremities in case of combined traumatic brain injury and multiple trauma of the extremities has also been proven, new functional methods of treatment of diaphyseal fractures of the shoulder, lower leg, spine and intra-articular injuries have been developed.In close scientific cooperation with scientists from other clinics of the institute, a comprehensive method of treating open injuries of the limbs has been developed (dissertation researches of I.F. Byalik, I.Yu. Klyukvin, O.P. Filippov, M.V. Zvezdina, R.S. Titov). Much scientific work has been carried out to improve the diagnosis and treatment of intra-articular injuries of the knee joint (dissertation researches by M.A. Malygina, O.P. Filippov, A.Yu. Vasa).From 2001 to 2016 the head of the department of emergency traumatology of the musculoskeletal system was a student of prof. V.P. Okhotsky – Dr. med. sciences, Professor, Academician of the Academy of Medical and Technical Sciences of the Russian Federation I.Yu. Klyukvin. Since 2016 the department is headed by Dr. med. sciences Alexey M. Fine.The scientific developments of the employees of the Department of Emergency Traumatology have a practical orientation. Every year, the department’s employees successfully perform more than 2500 surgical interventions using advanced low-traumatic techniques, making extensive use of the achievements of biotechnology.Целью данной работы явилось изучение истории развития травматологии-ортопедии в институте скорой помощи им. Н.В. Склифосовского.Травматология как самостоятельная дисциплина начала формироваться в институте им. Н.В. Склифосовского еще при профессоре С.С. Юдине (главный хирург с 1928 г.), пригласившем на работу известного аргентинского травматолога-ортопеда профессора Лелио Зено.В 1932 году травматологическое отделение института им. Н.В. Склифосовского возглавила профессор В.В. Гориневская. Ею была организована травматологическая клиника на 100 коек для лечения повреждений головы, позвоночника, конечностей, грудной и брюшной полостей. Она по праву считается одним из основоположников травматологической науки в СССР.По мере развития травматологии и ортопедии как самостоятельной специальности в 1961 году в институте были сформированы две клиники. Первой травматологической клиникой много лет руководил доктор мед. наук профессор И.И. Соколов. Вторую клинику возглавлял доктор мед. наук П.Н. Петров.В 1971 году руководителем травматологической службы института и главным травматологом Москвы (с 1971 по 2001 г.) был назначен доктор мед. наук, профессор, заслуженный деятель науки РФ, академик Российской Академии медико-технических наук РФ В.П. Охотский. При его активном участии в Москве была завершена реорганизация амбулаторной помощи, широко развернута работа по медицинским аспектам профилактики дорожно-транспортного травматизма и внедрению в практику наиболее рациональных способов диагностики и лечения больных с повреждениями опорно-двигательного аппарата. В НИИ СП им. Н.В. Склифосовского А.Г. Суваляном был внедрен метод интрамедуллярного остеосинтеза длинных трубчатых костей (плечевой, бедренной и большеберцовой). Под руководством проф. В.П. Охотского проведены посвященные данному методу диссертационные исследования А.Г. Суваляна, М.А. Суваляна и С.С. Мякоты. Также доказана целесообразность раннего оперативного вмешательства на конечностях при сочетанной черепно-мозговой травме и множественной травме конечностей, созданы новые функциональные методы лечения диафизарных переломов плеча, голени, позвоночника и внутрисуставных повреждений.В тесном научном сотрудничестве с учеными других клиник института разработан комплексный метод лечения открытых повреждений конечностей (диссертационные исследования И.Ф. Бялика, И.Ю. Клюквина, О.П. Филиппова, М.В. Звездиной, Р.С. Титова). Большая научная работа проведена по совершенствованию диагностики и лечения внутрисуставных повреждений коленного сустава (диссертационные исследования М.А. Малыгиной, О.П. Филиппова, А.Ю. Ваза).С 2001 по 2016 г. руководителем отделения неотложной травматологии опорно-двигательного аппарата являлся ученик проф. В.П. Охотского — доктор медицинских наук, профессор, академик Академии медико-технических наук РФ И.Ю. Клюквин. С 2016 г. отделением руководит доктор мед. наук Алексей Максимович Файн.Научные разработки сотрудников отделения неотложной травматологии имеют практическую направленность. Ежегодно в отделении успешно выполняются более 2500 оперативных вмешательств с применением передовых малотравматичных методик и широким использованием достижений биотехнологии

Radiative energy transfer in disordered photonic crystals

The difficulty of description of the radiative transfer in disordered photonic crystals arises from the necessity to consider on the equal footing the wave scattering by periodic modulations of the dielectric function and by its random inhomogeneities. We resolve this difficulty by approaching this problem from the standpoint of the general multiple scattering theory in media with arbitrary regular profile of the dielectric function. We use the general asymptotic solution of the Bethe-Salpeter equation in order to show that for a sufficiently weak disorder the diffusion limit in disordered photonic crystals is presented by incoherent superpositions of the modes of the ideal structure with weights inversely proportional to the respective group velocities. The radiative transfer and the diffusion equations are derived as a relaxation of long-scale deviations from this limiting distribution. In particular, it is shown that in general the diffusion is anisotropic unless the crystal has sufficiently rich symmetry, say, the square lattice in 2D or the cubic lattice in 3D. In this case, the diffusion is isotropic and only in this case the effect of the disorder can be characterized by the single mean-free-path depending on frequency.Comment: 27 pages, 4 figure

Factors associated with diversity, quantity and zoonotic potential of ectoparasites on urban mice and voles

Wild rodents are important hosts for tick larvae but co-infestations with other mites and insects are largely neglected. Small rodents were trapped at four study sites in Berlin, Germany, to quantify their ectoparasite diversity. Host-specific, spatial and temporal occurrence of ectoparasites was determined to assess their influence on direct and indirect zoonotic risk due to mice and voles in an urban agglomeration. Rodent-associated arthropods were diverse, including 63 species observed on six host species with an overall prevalence of 99%. The tick Ixodes ricinus was the most prevalent species, found on 56% of the rodents. The trapping location clearly affected the presence of different rodent species and, therefore, the occurrence of particular host-specific parasites. In Berlin, fewer temporary and periodic parasite species as well as non-parasitic species (fleas, chiggers and nidicolous Gamasina) were detected than reported from rural areas. In addition, abundance of parasites with low host-specificity (ticks, fleas and chiggers) apparently decreased with increasing landscape fragmentation associated with a gradient of urbanisation. In contrast, stationary ectoparasites, closely adapted to the rodent host, such as the fur mites Myobiidae and Listrophoridae, were most abundant at the two urban sites. A direct zoonotic risk of infection for people may only be posed by Nosopsyllus fasciatus fleas, which were prevalent even in the city centre. More importantly, peridomestic rodents clearly supported the life cycle of ticks in the city as hosts for their subadult stages. In addition to trapping location, season, host species, body condition and host sex, infestation with fleas, gamasid Laelapidae mites and prostigmatic Myobiidae mites were associated with significantly altered abundance of I. ricinus larvae on mice and voles. Whether this is caused by predation, grooming behaviour or interaction with the host immune system is unclear. The present study constitutes a basis to identify interactions and vector function of rodent-associated arthropods and their potential impact on zoonotic diseases

Reviews and syntheses : Arctic fire regimes and emissions in the 21st century

In recent years, the pan-Arctic region has experienced increasingly extreme fire seasons. Fires in the northern high latitudes are driven by current and future climate change, lightning, fuel conditions, and human activity. In this context, conceptualizing and parameterizing current and future Arctic fire regimes will be important for fire and land management as well as understanding current and predicting future fire emissions. The objectives of this review were driven by policy questions identified by the Arctic Monitoring and Assessment Programme (AMAP) Working Group and posed to its Expert Group on Short-Lived Climate Forcers. This review synthesizes current understanding of the changing Arctic and boreal fire regimes, particularly as fire activity and its response to future climate change in the pan-Arctic have consequences for Arctic Council states aiming to mitigate and adapt to climate change in the north. The conclusions from our synthesis are the following. (1) Current and future Arctic fires, and the adjacent boreal region, are driven by natural (i.e. lightning) and human-caused ignition sources, including fires caused by timber and energy extraction, prescribed burning for landscape management, and tourism activities. Little is published in the scientific literature about cultural burning by Indigenous populations across the pan-Arctic, and questions remain on the source of ignitions above 70 degrees N in Arctic Russia. (2) Climate change is expected to make Arctic fires more likely by increasing the likelihood of extreme fire weather, increased lightning activity, and drier vegetative and ground fuel conditions. (3) To some extent, shifting agricultural land use and forest transitions from forest-steppe to steppe, tundra to taiga, and coniferous to deciduous in a warmer climate may increase and decrease open biomass burning, depending on land use in addition to climate-driven biome shifts. However, at the country and landscape scales, these relationships are not well established. (4) Current black carbon and PM2.5 emissions from wildfires above 50 and 65 degrees N are larger than emissions from the anthropogenic sectors of residential combustion, transportation, and flaring. Wildfire emissions have increased from 2010 to 2020, particularly above 60 degrees N, with 56% of black carbon emissions above 65 degrees N in 2020 attributed to open biomass burning - indicating how extreme the 2020 wildfire season was and how severe future Arctic wildfire seasons can potentially be. (5) What works in the boreal zones to prevent and fight wildfires may not work in the Arctic. Fire management will need to adapt to a changing climate, economic development, the Indigenous and local communities, and fragile northern ecosystems, including permafrost and peatlands. (6) Factors contributing to the uncertainty of predicting and quantifying future Arctic fire regimes include underestimation of Arctic fires by satellite systems, lack of agreement between Earth observations and official statistics, and still needed refinements of location, conditions, and previous fire return intervals on peat and permafrost landscapes. This review highlights that much research is needed in order to understand the local and regional impacts of the changing Arctic fire regime on emissions and the global climate, ecosystems, and pan-Arctic communities.peerReviewe