Radiative signature of magnetic fields in internal shocks

Common models of blazars and gamma-ray bursts assume that the plasma underlying the ob- served phenomenology is magnetized to some extent. Within this context, radiative signatures of dissipation of kinetic and conversion of magnetic energy in internal shocks of relativistic magnetized outflows are studied. We model internal shocks as being caused by collisions of homogeneous plasma shells. We compute the flow state after the shell interaction by solving Riemann problems at the contact surface between the colliding shells, and then compute the emission from the resulting shocks. Under the assumption of a constant flow luminosity we find that there is a clear difference between the models where both shells are weakly magne- tized ({\sigma}<\sim0.01) and those where, at least, one shell has a {\sigma}>\sim0.01. We obtain that the radiative efficiency is largest for models in which, regardless of the ordering, one shell is weakly and the other strongly magnetized. Substantial differences between weakly and strongly magne- tized shell collisions are observed in the inverse-Compton part of the spectrum, as well as in the optical, X-ray and 1GeV light curves. We propose a way to distinguish observationally between weakly magnetized from magnetized internal shocks by comparing the maximum frequency of the inverse-Compton and synchrotron part of the spectrum to the ratio of the inverse-Compton and synchrotron fluence. Finally, our results suggest that LBL blazars may correspond to barely magnetized flows, while HBL blazars could correspond to moderately magnetized ones. Indeed, by comparing with actual blazar observations we conclude that the magnetization of typical blazars is {\sigma} <\sim 0.01 for the internal shock model to be valid in these sources.Comment: 15 pages, 11 figures, accepted for publication in MNRA

Choice of Age Cut-off for Endoscopy in Dyspepsia in Developing Countries According to Incidence of Gastric Cancer

Endoscopic examination of all patients with dyspepsia is hard to perform, because of high annual prevalence of dyspepsia and limited resource availability, especially in developing countries. Aim was to establish age cut off for upper endoscopy in dyspeptic patients without alarming features according on incidence of gastric cancer in western Herzegovina in Bosnia and Herzegovina. Group of 2697 (1536 males, 1161 females) patients over 15 with chronic dyspepsia without alarming features and symptoms of gastroesophageal reflux disease, had been referred for a diagnostic upper endoscopy during 4 years. Study was prospective. All 34 gastric cancers were diagnosed in male patients above 55 years, and in female ones above 60. In the same age groups two thirds of gastric ulcers were found out. If the age cut off for dyspeptic patients had been 55 years for male and 60 for female gender, the workload could be decreased by 50%. The choice of alternative approaches is possible, depending on the level of diagnostic uncertainty, the patient and his physician are prepared to accept. Age cut off determines diagnostic approach in chronic dyspepsia, and greatly decreases the endoscopy workload

Green function estimates for subordinate Brownian motions : stable and beyond

A subordinate Brownian motion $X$ is a L\'evy process which can be obtained by replacing the time of the Brownian motion by an independent subordinator. In this paper, when the Laplace exponent $\phi$ of the corresponding subordinator satisfies some mild conditions, we first prove the scale invariant boundary Harnack inequality for $X$ on arbitrary open sets. Then we give an explicit form of sharp two-sided estimates on the Green functions of these subordinate Brownian motions in any bounded $C^{1,1}$ open set. As a consequence, we prove the boundary Harnack inequality for $X$ on any $C^{1,1}$ open set with explicit decay rate. Unlike {KSV2, KSV4}, our results cover geometric stable processes and relativistic geometric stable process, i.e. the cases when the subordinator has the Laplace exponent $$\phi(\lambda)=\log(1+\lambda^{\alpha/2}) (0 \alpha)$$ and $$\phi(\lambda)=\log(1+(\lambda+m^{\alpha/2})^{2/\alpha}-m) (00, d >2) .$$Comment: We have weaken the condition (A5). References are update