8,869 research outputs found

    Lobster Eye X-ray optics for astrophysics: Recent status

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    X-ray optics in Lobster Eye arrangement represent promising complementary device to narrow field X-ray optics in common use. We present briefly recent status of design, developments, and tests of X-ray optics including Lobster Eye modules developed and tested within recent space project

    Hyperpolarized xenon nuclear spins detected by optical atomic magnetometry

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    We report the use of an atomic magnetometer based on nonlinear magneto-optical rotation with frequency modulated light (FM NMOR) to detect nuclear magnetization of xenon gas. The magnetization of a spin-exchange-polarized xenon sample (1.71.7 cm3^3 at a pressure of 55 bar, natural isotopic abundance, polarization 1%), prepared remotely to the detection apparatus, is measured with an atomic sensor (which is insensitive to the leading field of 0.45 G applied to the sample; an independent bias field at the sensor is 140μ140 \muG). An average magnetic field of 10\sim 10 nG induced by the xenon sample on the 10-cm diameter atomic sensor is detected with signal-to-noise ratio 10\sim 10, limited by residual noise in the magnetic environment. The possibility of using modern atomic magnetometers as detectors of nuclear magnetic resonance and in magnetic resonance imaging is discussed. Atomic magnetometers appear to be ideally suited for emerging low-field and remote-detection magnetic resonance applications.Comment: 4 pages, 4 figure

    Geometric phases of scattering states in a ring geometry: adiabatic pumping in mesoscopic devices

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    Geometric phases of scattering states in a ring geometry are studied based on a variant of the adiabatic theorem. Three time scales, i.e., the adiabatic period, the system time and the dwell time, associated with adiabatic scattering in a ring geometry plays a crucial role in determining geometric phases, in contrast to only two time scales, i.e., the adiabatic period and the dwell time, in an open system. We derive a formula connecting the gauge invariant geometric phases acquired by time-reversed scattering states and the circulating (pumping) current. A numerical calculation shows that the effect of the geometric phases is observable in a nanoscale electronic device.Comment: 9 pages, 3 figure

    High Energy Gamma--Radiation from the Galactic Center due to Neutralino Annihilation

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    We study the NGS (Non--dissipative Gravitational Singularity) model, which successfully describes the non--linear stage of evolution of perturbations (see [1], [2] and references therein). This model predicts DM density distribution ρ(r)rα\rho(r) \sim r^{-\alpha} with α1.8\alpha \simeq 1.8 which holds from very small distances rmin0.01 pcr_{\rm min} \simeq 0.01~{\rm pc} up to very large distances rmax5 Mpcr_{\rm max} \simeq 5~{\rm Mpc}. Assuming the neutralino to be a CDM particle, we calculate the annihilation of neutralinos in the vicinity of the singularity (Galactic Center). If neutralinos are the dominant component of DM in our Galaxy, the produced energy is enough to provide the whole observed activity of the GC. Neutralinos of the most general composition and of mass in the range 20~{\rm GeV} \leq m_\c \leq 1~{\rm TeV} are considered. We find the neutralino compositions which give the relic density needed for the Mixed Dark Matter (MDM) model and we evaluate for these compositions the high--energy (Eγ>100 MeVE_{\gamma} > 100 ~{\rm MeV}) gamma--ray flux under the constraint that the radio flux is lower than the observational limit. The compositions with the detectable gamma--ray flux which we found are provided by a set of almost pure gaugino states with the neutralino mass between 100100 and 500500 GeV. We demonstrate that a detectable high--energy gamma--ray flux is produced by the neutralino annihilation also in the case when neutralinos provide a small fraction (down to 0.1%0.1 \%) of the DM in our Galaxy. The predicted flux is Fγ107108 cm2 s1F_\gamma \sim 10^{-7}-10^{-8}~{\rm cm}^{-2}~{\rm s}^{-1} for E_\gamma \gsim 300~{\rm MeV}Comment: Plain TeX 11 pages 4 figures available on request. Preprint numbers LNGS 94/90 - DFTT 5/9

    Reconstruction of modified gravity with ghost dark energy models

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    In this work, we reconstruct the f(R)f(R) modified gravity for different ghost and generalized ghost dark energy models in FRW flat universe, which describe the accelerated expansion of the universe. The equation of state of reconstructed f(R)f(R) - gravity has been calculated. We show that the corresponding f(R)f(R) gravity of ghost dark energy model can behave like phantom or quintessence. We also show that the equation of state of reconstructed f(R)f(R) gravity for generalized ghost model can transit from quintessence regime to the phantom regime as indicated by recent observations.Comment: 13 pages, some references and one author are added. Accepted for publication by MPL

    Суспільне значення музеїв

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    Урбан В. А. Суспільне значення музеїв / В. А. Урбан // Сучасні проблеми правового, економічного та соціального розвитку держави : тези доп. Міжнар. наук.-практ. конф. (м. Харків, 27 листоп. 2020 р.). – Харків, 2020. – С. 298 - 299.Розкривається суспільне значення музеїв. Людство завжди ставило перед собою питання: «а що ж було раніше?», а музеї завжди знаходили відповідь на це запитання. За своїм профілем сучасні музеї поділяються на історичні, археологічні, краєзнавчі, природничі, мистецькі, літературні. Всі вони створені для збереження і демонстрації комплексів пам’яток, які відносяться до певного типу культурно-історичних надбань людства. Раскрывается публичное значение музеев. Человечество всегда задавало вопрос: «а что же было раньше?», а музеи всегда находили ответ на этот вопрос. По своему профилю современные музеи делятся на исторические, археологические, краеведческие, естественные, художественные, литературные. Все они созданы для сохранения и демонстрации комплексов памятников, относящихся к определенному типу культурно-исторического достояния человечества. The social significance of museums is revealed. Mankind has always asked the question: "What happened before?", And museums have always found the answer to this question. According to their profile, modern museums are divided into historical, archaeological, local lore, natural, artistic, literary. All of them are designed to preserve and demonstrate complexes of monuments that belong to a certain type of cultural and historical heritage of mankind

    A framework for community curation of interspecies interactions literature

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    The quantity and complexity of data being generated and published in biology has increased substantially, but few methods exist for capturing knowledge about phenotypes derived from molecular interactions between diverse groups of species, in such a way that is amenable to data-driven biology and research. To improve access to this knowledge, we have constructed a framework for the curation of the scientific literature studying interspecies interactions, using data curated for the Pathogen–Host Interactions database (PHI-base) as a case study. The framework provides a curation tool, phenotype ontology, and controlled vocabularies to curate pathogen–host interaction data, at the level of the host, pathogen, strain, gene, and genotype. The concept of a multispecies genotype, the ‘metagenotype,’ is introduced to facilitate capturing changes in the disease-causing abilities of pathogens, and host resistance or susceptibility, observed by gene alterations. We report on this framework and describe PHI-Canto, a community curation tool for use by publication authors
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