159 research outputs found
Overview remarks on homogeneous, N = 1, d = 11 supergravity cosmologies
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
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
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
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
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
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
International audienc
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