1,246 research outputs found

    Is our Sun a Singleton?

    Full text link
    Most stars are formed in a cluster or association, where the number density of stars can be high. This means that a large fraction of initially-single stars will undergo close encounters with other stars and/or exchange into binaries. We describe how such close encounters and exchange encounters can affect the properties of a planetary system around a single star. We define a singleton as a single star which has never suffered close encounters with other stars or spent time within a binary system. It may be that planetary systems similar to our own solar system can only survive around singletons. Close encounters or the presence of a stellar companion will perturb the planetary system, often leaving planets on tighter and more eccentric orbits. Thus planetary systems which initially resembled our own solar system may later more closely resemble some of the observed exoplanet systems.Comment: 2 pages, 1 figure. To be published in the proceedings of IAUS246 "Dynamical Evolution of Dense Stellar Systems". Editors: E. Vesperini (Chief Editor), M. Giersz, A. Sill

    A Method to Polarize Stored Antiprotons to a High Degree

    Get PDF
    Polarized antiprotons can be produced in a storage ring by spin--dependent interaction in a purely electron--polarized hydrogen gas target. The polarizing process is based on spin transfer from the polarized electrons of the target atoms to the orbiting antiprotons. After spin filtering for about two beam lifetimes at energies T40170T\approx 40-170 MeV using a dedicated large acceptance ring, the antiproton beam polarization would reach P=0.20.4P=0.2-0.4. Polarized antiprotons would open new and unique research opportunities for spin--physics experiments in pˉp\bar{p}p interactions

    Information Capacity as a Decision Factor in Information Confrontation of States

    Get PDF
    The article is devoted to the information confrontation of states in modern conditions. The approaches of various countries to the information impact on the internal political situation of other states and measures taken at the technical and legislative level in order to counter this threat are described. The concept of «information capacity of the state» is introduced and its components are described. It is concluded that the scale of the information confrontation of states depends on factors that correlate with the components of the information capacity of the state. The use of the introduced conceptual apparatus «information capacity of the state» is a necessary condition for the success of the state policy in matters of information confrontation

    State Information Capacity as Information Sovereignty Basis

    Get PDF
    This article examines the confrontation of states in the information space and aspects of the state information policy in terms of protecting information sovereignty. The purpose of this study is to introduce the concept of “information capacity of the state” and justify the need for its use in planning and organizing internal and external policy management activities to protect the information sovereignty of the state. On the basis of research, using the methods of comparative and situational analyzes, a common factor has been identified. This factor determines capabilities of states in the information space, it is “information capacity of the state”. The essence of the concept of “information capacity of the state” is defined and it was demonstrated that the information capacity of the state is the basis of information sovereignty. The analysis of domestic and foreign experience of applying the information capac ity of the state in the conduct of information policy in order to protect information sovereignty was done. The steps to ensure compliance with the legislation of the Russian Federation on the example of blocking access to the Telegram messenger from the territory of the Russian Federation were analyzed. As a result of this analysis, it was concluded that it is impossible to ensure the legislation of the Russian Federation in the information space using the current information capacity of the state. To solve this problem, the article proposes to use not only technical, but also organizational measures. To prevent this situation from recurring in future, it is proposed to introduce the concept of “information capacity of the state”, defined in this article, into the regulatory acts governing the state information policy (National Security Strategy of the Russian Federation, Doctrine of Information Security of the Russian Federation, Federal Law № 149-ФЗ)

    pfmdr1 amplification is related to increased Plasmodium falciparum In Vitro sensitivity to the Bisquinoline Piperaquine

    Get PDF
    The 4-aminoquinoline bisquinoline piperaquine is an important partner drug in one of the presently recommended artemisinin combination therapies. Recent clinical trials have confirmed its high efficacy in combination with dihydroartemisinin. Resistance to piperaquine alone has, however, been documented. Amplification in copy number of the Plasmodium falciparum multidrug resistance locus on chromosome 5, containing the pfmdr1 gene, has been shown to confer resistance to structurally unrelated antimalarials. Through the determination of the 50% inhibitory concentrations (IC(50)s) and IC(90)s for piperaquine and chloroquine in a set of 46 adapted P. falciparum cultures originating from the Thai-Burmese border, we have characterized the regions around the pfmdr1 gene and identified a significant association between the presence of pfmdr1 duplications and enhanced sensitivity to piperaquine (P = 0.005 for IC50 and P = 0.002 for IC90) and chloroquine, reaching statistical significance at IC(90)s (P = 0.026). These results substantiate the potential importance of pfmdr1 copy number amplifications in the efficacy of the combination therapy piperaquine-dihydroartemisinin. It supports the rational use of 4-aminoquinolines and artemisinin-based compounds, as they independently select for mutually incompatible combinations of mutations.Swedish Development Cooperation Agency-Department for Research Cooperation [SWE 2005-0017, SWE 2005-4596, SWE-2007-174, SWE-2005-4027]; Fundacao para a Ciencia e Tecnologia (FCT)/Ministerio da Ciencia e Ensino Superior, Portugal-MCES [SFRH/BPD/76614/2011]; Wellcome Trust of Great Britaininfo:eu-repo/semantics/publishedVersio

    Validity of the Central Sensitization Inventory to Address Human Assumed Central Sensitization:Newly Proposed Clinically Relevant Values and Associations

    Get PDF
    Central sensitization cannot be directly demonstrated in humans and thus a gold standard is missing. Therefore, we used human assumed central sensitization (HACS) when associated with humans. The central sensitization inventory (CSI) is a screening questionnaire for addressing symptoms that are associated with HACS. This cross-sectional study compared patients with chronic pain and at least one central sensitivity syndrome with healthy, pain-free controls via ROC analyses. Analyses were performed for all participants together and for each sex separately. Regression analyses were performed on patients with chronic pain with and without central sensitivity syndromes. Based on 1730 patients and 250 healthy controls, cutoff values for the CSI for the total group were established at 30 points: women: 33 points; men: 25 points. Univariate and multivariate regression analyses were used to identify possible predictors for the CSI score in 2890 patients with chronic pain. The CSI score is associated with all independent factors and has a low association with pain severity in women and a low association with pain severity, age, and body mass index in men. The newly established CSI cutoff values are lower than in previous studies and different per sex, which might be of clinical relevance in daily practice and importance in research.</p

    Comparing HARPS and Kepler surveys: The alignment of multiple-planet systems

    Full text link
    Aims. We study a subset of the planetary population characterized both by HARPS and Kepler surveys. We compare the statistical properties of planets in systems with m.sin i >5-10 M_Earth and R>2 R_Earth. If we assume that the underlying population has the same characteristics, the different detection sensitivity to the orbital inclination relative to the line of sight allows us to probe the planets' mutual inclination. Methods. We considered the frequency of systems with one, two and three planets as dictated by HARPS data. We used Kepler's planetary period and host mass and radii distributions (corrected from detection bias) to model planetary systems in a simple yet physically plausible way. We then varied the mutual inclination between planets in a system according to different prescriptions (completely aligned, Rayleigh distributions and isotropic) and compared the transit frequencies with one, two or three planets with those measured by Kepler. Results. The results show that the two datasets are compatible, a remarkable result especially because there are no tunable knobs other than the assumed inclination distribution. For m.sin i cutoffs of 7-10 M_Earth, which are those expected to correspond to the radius cutoff of 2 R_Earth, we conclude that the results are better described by a Rayleigh distribution with mode of 1 deg or smaller. We show that the best-fit scenario only becomes a Rayleigh distribution with mode of 5 deg if we assume a rather extreme mass-radius relationship for the planetary population. Conclusions. These results have important consequences for our understanding of the role of several proposed formation and evolution mechanisms. They confirm that planets are likely to have been formed in a disk and show that most planetary systems evolve quietly without strong angular momentum exchanges (abridged).Comment: 10 pages, 6 figures, 4 tables, accepted for publication in Astronomy & Astrophysic

    Debris discs in binaries: a numerical study

    Full text link
    Debris disc analysis and modelling provide crucial information about the structure and the processes at play in extrasolar planetary systems. In binary systems, this issue is more complex because the disc should in addition respond to the companion star's perturbations. We explore the dynamical evolution of a collisionally active debris disc for different initial parent body populations, diverse binary configurations and optical depths. We focus on the radial extent and size distribution of the disc at a stationary state. We numerically follow the evolution of 10510^{5} massless small grains, initially produced from a circumprimary disc of parent bodies following a size distribution in dNs3.5dN \propto s^{-3.5}ds . Grains are submitted to both stars' gravity as well as radiation pressure. In addition, particles are assigned an empirically derived collisional lifetime. For all the binary configurations the disc extends far beyond the critical semimajor axis acrita_crit for orbital stability. This is due to the steady production of small grains, placed on eccentric orbits reaching beyond acrita_crit by radiation pressure. The amount of matter beyond acrit depends on the balance between collisional production and dynamical removal rates: it increases for more massive discs as well as for eccentric binaries. Another important effect is that, in the dynamically stable region, the disc is depleted from its smallest grains. Both results could lead to observable signatures. We have shown that a companion star can never fully truncate a collisionally active disc. For eccentric companions, grains in the unstable regions can significantly contribute to the thermal emission in the mid-IR. Discs with sharp outer edges, especially bright ones such as HR4796A, are probably shaped by other mechanisms.Comment: accepted for publication in A&
    corecore