Diffuse Gamma-ray Emission from the Galactic Center - A Multiple Energy Injection Model

We suggest that the energy source of the observed diffuse gamma-ray emission from the direction of the Galactic center is the Galactic black hole Sgr A*, which becomes active when a star is captured at a rate of $\sim 10^{-5}$ yr^{-1}. Subsequently the star is tidally disrupted and its matter is accreted into the black hole. During the active phase relativistic protons with a characteristic energy $\sim 6\times 10^{52}$ erg per capture are ejected. Over 90% of these relativistic protons disappear due to proton-proton collisions on a timescale $\tau_{pp} \sim 10^4$ years in the small central bulge region with radius $\sim 50$ pc within Sgr A*, where the density is $\ge 10^3$ cm^{-3}. The gamma-ray intensity, which results from the decay of neutral pions produced by proton-proton collisions, decreases according to $e^{-t/\tau_{pp}}$, where t is the time after last stellar capture. Less than 5% of relativistic protons escaped from the central bulge region can survive and maintain their energy for >10^7 years due to much lower gas density outside, where the gas density can drop to $\sim 1$ cm$^{-3}$. They can diffuse to a $\sim 500$ pc region before disappearing due to proton-proton collisions. The observed diffuse GeV gamma-rays resulting from the decay of neutral pions produced via collision between these escaped protons and the gas in this region is expected to be insensitive to time in the multi-injection model with the characteristic injection rate of 10^{-5} yr^{-1}. Our model calculated GeV and 511 keV gamma-ray intensities are consistent with the observed results of EGRET and INTEGRAL, however, our calculated inflight annihilation rate cannot produce sufficient intensity to explain the COMPTEL data.Comment: 8 pages, 3 figures, accepted by A&

Nuclear Interaction Gamma-Ray Lines from the Galactic Center Region

Aims. The accretion of stars onto the central supermassive black hole at the center of the Milky Way is predicted to generate large fluxes of subrelativistic ions in the Galactic center region. We analyze the intensity, shape and spatial distribution of de-excitation gamma-ray lines produced by nuclear interactions of these energetic particles with the ambient medium. Methods. We first estimate the amount and mean kinetic energy of particles released from the central black hole during star disruption. We then calculate from a kinetic equation the energy and spatial distributions of these particles in the Galactic center region. These particle distributions are then used to derive the characteristics of the main nuclear interaction gamma-ray lines. Results. Because the time period of star capture by the supermassive black hole is expected to be shorter than the lifetime of the ejected fast particles against Coulomb losses, the gamma-ray emission is predicted to be stationary. We find that the nuclear de-excitation lines should be emitted from a region of maximum 5$^\circ$ angular radius. The total gamma-ray line flux below 8 MeV is calculated to be $\approx10^{-4}$ photons cm$^{-2}$ s$^{-1}$. The most promising lines for detection are those at 4.44 and $\sim$6.2 MeV, with a predicted flux in each line of $\approx$$10^{-5}$ photons cm$^{-2}$ s$^{-1}$. Unfortunately, it is unlikely that this emission can be detected with the INTEGRAL observatory. But the predicted line intensities appear to be within reach of future gamma-ray space instruments. A future detection of de-excitation gamma-ray lines from the Galactic center region would provide unique information on the high-energy processes induced by the central supermassive black hole and the physical conditions of the emitting region.Comment: 7 pages, 5 figures, accepted for publication in A&

Minimal information for studies of extracellular vesicles 2018 (MISEV2018):a position statement of the International Society for Extracellular Vesicles and update of the MISEV2014 guidelines

The last decade has seen a sharp increase in the number of scientific publications describing physiological and pathological functions of extracellular vesicles (EVs), a collective term covering various subtypes of cell-released, membranous structures, called exosomes, microvesicles, microparticles, ectosomes, oncosomes, apoptotic bodies, and many other names. However, specific issues arise when working with these entities, whose size and amount often make them difficult to obtain as relatively pure preparations, and to characterize properly. The International Society for Extracellular Vesicles (ISEV) proposed Minimal Information for Studies of Extracellular Vesicles (“MISEV”) guidelines for the field in 2014. We now update these “MISEV2014” guidelines based on evolution of the collective knowledge in the last four years. An important point to consider is that ascribing a specific function to EVs in general, or to subtypes of EVs, requires reporting of specific information beyond mere description of function in a crude, potentially contaminated, and heterogeneous preparation. For example, claims that exosomes are endowed with exquisite and specific activities remain difficult to support experimentally, given our still limited knowledge of their specific molecular machineries of biogenesis and release, as compared with other biophysically similar EVs. The MISEV2018 guidelines include tables and outlines of suggested protocols and steps to follow to document specific EV-associated functional activities. Finally, a checklist is provided with summaries of key points

Immigrant youth. Acculturation, identity and adaptation

Der Aufsatz ... berichtet über einige der Hauptergebnisse einer grossen internationalen Studie (ICSEY) zur Akkulturation und Adaption von zugewanderten Jugendlichen im Alter von 13 bis 18 Jahren, die in 13 verschiedenen Aufnahmeländern (einschließlich Deutschland) leben (n = 5.366). Weiterhin wurde eine Stichprobe von einheimischen (im Original: national) Jugendlichen (n = 2.631) untersucht. Die Analyse geht drei Kernfragen nach: Wie gehen die Jugendlichen mit Migrationshintergrund mit dem Akkulturationsprozess um? Wie gut passen sich die Jugendlichen mit Migrationshintergrund an die Gesellschaft und Schule des Aufnahmelandes an? Bestehen bedeutsame Beziehungen zwischen ihrer Akkulturationseinstellung und ihrer sozialen und schulischen Anpassung? Eine Clusteranalyse förderte vier unterschiedliche Profile von Akkulturationseinstellungen der Jugendlichen mit Migrationshintergrund zutage: integrativ, ethnisch, national und diffus. Eine Faktorenanalyse von fünf Adaptionsvariablen ließ auf zwei verschiedene Formen der Adaption schliessen: psychisch und soziokulturell. Es zeigten sich substantielle Beziehungen zwischen den Akkulturationseinstellungen der Jugendlichen und ihrer Anpassung. Die Jugendlichen mit einem Integrationsprofil weisen die besten Ergebnisse in Bezug auf psychische (Wohlbefinden) und soziokulturelle (schulische und soziale) Adaption auf, während diejenigen mit einem diffusen Akkulturationseinstellungsprofil die ungünstigsten Ergebnisse erreichen. Dazwischen liegen die Jugendlichen mit einem ethnischen Profil, deren Anpassung in Bezug auf ihr Wohlbefinden recht gut, ihre soziale und schulische Anpassung jedoch schlechter ist. Ebenfalls dazwischen liegen die Jugendlichen mit einem nationalen Profil, deren Adaption in psychischer Hinsicht eher ungünstig ist und in soziokultureller Hinsicht eine leicht negative Tendenz aufweist. Dieses Ergebnismuster konnte durch Strukturgleichungsmodelle weitgehend bestätigt werden. Weiterhin zeigen die Analysen dieser Studie, dass wahrgenommene Diskriminierung sowohl mit psychischer als auch mit sozialer Anpassung negativ zusammen hängt und einen stark segregierenden Effekt auf Migranten hat. Die Schlussfolgerungen der Untersuchung für das Leben der Jugendlichen in einer Einwanderungsgesellschaft sind klar: Jugendliche mit Migrationshintergrund sollten ermutigt werden, einen Bezug zu ihrer Herkunftskultur zu erhalten und gleichzeitig enge Verbindungen zur Aufnahmegesellschaft aufzubauen. (DIPF/Orig.)