159 research outputs found

    Overview remarks on homogeneous, N = 1, d = 11 supergravity cosmologies

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    The dynamics of the full class of homogeneous N = 1, d = 11 supergravity world models is investigated. By using the classification of Lie algebras of Lie groups which act simply transitively on 6- and 7-dimensional compact spaces some conclusions are drawn concerning the non-existence of the chaotic regime near the singularity. This is illustrated with some new solutions having a richer structure of the microspace. The significance of known solutions is briefly discussed

    Multiscaling of galactic cosmic ray flux

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    Multiscaling analysis of differential flux dissipation rate of galactic cosmic rays (Carbon nuclei) is performed in the energy ranges: 56.3-73.4 Mev/nucleon and 183.1-198.7 MeV/nucleon, using the data collected by ACE/CRIS spacecraft instrument for 2000 year. The analysis reveals strong (turbulence-like) intermittency of the flux dissipation rate for the short-term intervals: 1-30 hours. It is also found that type of the intermittency can be different in different energy ranges

    Septic Embolism: A Potentially Devastating Complication of Infective Endocarditis

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    Infective endocarditis is associated with significant cardiac and noncardiac morbidity. Among many complications, septic embolism has the potential of causing devastating sequelae and even life-threatening clinical situations. This dreaded clinico-pathologic entity is characterized by its heterogeneous presentation and the ability to affect various body systems and organs. Septic emboli to the brain, kidneys, spleen, and the pulmonary system constitute the vast majority of metastatic infections. However, other organ systems can also be affected. This chapter provides an overview of septic embolism associated with infective endocarditis, focusing on key diagnostic and therapeutic considerations in the most commonly seen and clinically relevant scenarios

    Foreign Intravascular Object Embolization and Migration: Bullets, Catheters, Wires, Stents, Filters, and More

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    Foreign intravascular object embolization (FIOE) is an important, yet underreported occurrence that has been described in a variety of settings, from penetrating trauma to intravascular procedures. In this chapter, the authors will review the most common types of FIOEs, including bullet or “projectile” embolism (BPE), followed by intravascular catheter or wire embolization (ICWE), and conclude with intravascular noncatheter object (e.g., coil, gelatin, stent, and venous filter) migration (INCOM). In addition to detailed topic-based summaries, tables highlighting selected references and case scenarios are also presented to provide the reader with a resource for future research in this clinical area

    Spectral Formation in X-Ray Pulsars: Bulk Comptonization in the Accretion Shock

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    Accretion-powered X-ray pulsars are among the most luminous X-ray sources in the Galaxy. However, despite decades of theoretical and observational work since their discovery, no satisfactory model for the formation of the observed X-ray spectra has emerged. In particular, the previously available theories are unable to reproduce the power-law variation observed at high energies in many sources. In this paper, we present the first self-consistent calculation of the spectrum emerging from a pulsar accretion column that includes an explicit treatment of the energization occurring in the shock. Using a rigorous eigenfunction expansion method based on the exact dynamical solution for the velocity profile in the column, we obtain a closed-form expression for the Green's function describing the upscattering of radiation injected into the column from a monochromatic source located at the top of the thermal mound, near the base of the flow. The Green's function is convolved with a Planck distribution to calculate the radiation spectrum resulting from the reprocessing of blackbody photons emitted by the thermal mound. We demonstrate that the energization of the photons in the shock naturally produces an X-ray spectrum with a power-law shape at high energies and a blackbody shape at low energies, in agreement with many observations of accreting X-ray pulsars.Comment: Accepted for publication in Ap

    Kinetic Turbulence

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    The weak collisionality typical of turbulence in many diffuse astrophysical plasmas invalidates an MHD description of the turbulent dynamics, motivating the development of a more comprehensive theory of kinetic turbulence. In particular, a kinetic approach is essential for the investigation of the physical mechanisms responsible for the dissipation of astrophysical turbulence and the resulting heating of the plasma. This chapter reviews the limitations of MHD turbulence theory and explains how kinetic considerations may be incorporated to obtain a kinetic theory for astrophysical plasma turbulence. Key questions about the nature of kinetic turbulence that drive current research efforts are identified. A comprehensive model of the kinetic turbulent cascade is presented, with a detailed discussion of each component of the model and a review of supporting and conflicting theoretical, numerical, and observational evidence.Comment: 31 pages, 3 figures, 99 references, Chapter 6 in A. Lazarian et al. (eds.), Magnetic Fields in Diffuse Media, Astrophysics and Space Science Library 407, Springer-Verlag Berlin Heidelberg (2015

    Solar Wind Turbulence and the Role of Ion Instabilities

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