Pauli blocking effects on pair creation in strong electric field

The process of electron-positron pair creation and oscillation in uniform electric field is studied, taking into account Pauli exclusion principle. Generally, we find that pair creation is suppressed, hence coherent oscillations occur on longer time scales. Considering pair creation in already existing electron-positron plasma we find that the dynamics depends on pair distribution function. We considered Fermi-Dirac distribution of pairs and found that for small temperatures pair creation is suppressed, while for small chemical potentials it increases: heating leads to enhancement of pair creation.Comment: Accepted for publication in Physical Review

Pair creation in hot electrosphere of compact astrophysical objects

The mechanism of pair creation in electrosphere of compact astrophysical objects such as quark stars or neutron stars is revisited, paying attention to evaporation of electrons and acceleration of electrons and positrons, previously not addressed in the literature. We perform a series of numerical simulations using the Vlasov-Maxwell equations. The rate of pair creation strongly depends on electric field strength in the electrosphere. Despite Pauli blocking is explicitly taken into account, we find no exponential suppression of the pair creation rate at low temperatures. The luminosity in pairs increases with temperature and it may reach up to $L_\pm\sim 10^{52}$ erg/s, much larger than previously assumed

Advertising and Organizational Support for the Export of Educational Services

In this article the authors examine the experience in attracting foreign citizens. The article outlines the main principles, key directions and activities aimed at increasing the number of foreign student

Low Diagnostic Yield of Routine Cerebrospinal Fluid Analysis in Juvenile Stroke

Background: The diagnostic value of cerebrospinal fluid (CSF) analysis in juvenile stroke, i.e., stroke in young adult patients, is not well studied. We sought to determine the therapeutic impact of routine CSF-analysis in young adults with acute ischemic stroke or transient ischemic attack (TIA).Methods: We abstracted data from patients with acute cerebral ischemia aged 18–45 years who were consecutively admitted to our stroke center between 01/2008 and 12/2015. We routinely performed CSF-analysis in patients with hitherto unknown stroke etiology after complete diagnostic work up. We assessed the frequency and underlying causes of abnormal CSF-findings and their impact on secondary stroke prevention therapy.Results: Among 379 patients (median [IQR:IQR3-IQR1] age 39 [10:43-33] years, 48% female) with acute ischemic stroke (n = 306) or TIA (n = 73), CSF analysis was performed in 201 patients (53%). Of these, 25 patients (12.4 %) had CSF pleocytosis (leucocyte cell count ≥ 5 Mpt/L), that was rated as non-specific (e.g., traumatic lumbar puncture, reactive pleocytosis) in 22 patients. Only 3 patients (1.5% of all patients who underwent CSF-analysis) with CSF-pleocytosis had specific CSF-findings that were related to stroke etiology and affected secondary stroke prevention therapy. Imaging findings had already suggested cerebral vasculitis in two of these patients.Conclusions: The diagnostic yield of routine CSF-analysis in juvenile stroke was remarkably low in our study. Our data suggest that CSF-analysis should only be performed if further findings raise the suspicion of cerebral vasculitis