Centaurus A at Hard X-rays and Soft Gamma-rays

Centaurus A, at a distance of less than 4 Mpc, is the nearest radio-loud AGN. Its emission is detected from radio to very-high energy gamma-rays. Despite the fact that Cen A is one of the best studied extragalactic objects the origin of its hard X-ray and soft gamma-ray emission (100 keV < E < 50 MeV) is still uncertain. Observations with high spatial resolution in the adjacent soft X-ray and hard gamma-ray regimes suggest that several distinct components such as a Seyfert-like nucleus, relativistic jets, and even luminous X-ray binaries within Cen A may contribute to the total emission in the MeV regime that has been detected with low spatial resolution. As the Spectral Energy Distribution of Cen A has its second maximum around 1 MeV, this energy range plays an important role in modeling the emission of (this) AGN. As there will be no satellite mission in the near future that will cover this energies with higher spatial resolution and better sensitivity, an overview of all existing hard X-ray and soft gamma-ray measurements of Cen A is presented here defining the present knowledge on Centaurus A in the MeV energy range.Comment: 8 pages, 5 figures, article for conference proceedings "The Many Faces of Centaurus A"; accepted for publication in PAS

Breaking barriers & building communities

Communities & Banking taps the wisdom of Rev. Steinle, the executive director of Hartford’s Christian Activities Council, a faith-based, nonsectarian organization focused on affordable housing and empowering the poor.Housing - Connecticut ; Poverty - Connecticut ; Community development - Connecticut

Development of buried wire gages for measurement of wall shear stress in Blastane experiments

Buried Wire Gages operated from a Constant Temperature Anemometer System are among the special types of instrumentation to be used in the Boundary Layer Apparatus for Subsonic and Transonic flow Affected by Noise Environment (BLASTANE). These Gages are of a new type and need to be adapted for specific applications. Methods were developed to fabricate Gage inserts and mount those in the BLASTANE Instrumentation Plugs. A large number of Gages were prepared and operated from a Constant Temperature Anemometer System to derive some of the calibration constants for application to fluid-flow wall shear-stress measurements. The final stage of the calibration was defined, but could not be accomplished because of non-availability of a suitable flow simulating apparatus. This report provides a description of the Buried Wire Gage technique, an explanation of the method evolved for making proper Gages and the calibration constants, namely Temperature Coefficient of Resistance and Conduction Loss Factor

Effect of Al on the sharpness of the MgSiO_3 perovskite to post-perovskite phase transition

By means of static ab-initio computations we investigate the influence of Al on the recently discovered perovskite to post-perovskite phase transition in MgSiO_3. We examine three substitution mechanisms for Al in the two structures: MgSi → AlAl; SiSiO → AlAl□; and Si → AlH. The substitutions introducing oxygen vacancies (highly unfavorable, energetically) and water (favorable) both lower the 0 Kelvin transition pressure, whereas charge coupled substitution increases it relative to 105 GPa for pure MgSiO_3. From the transition pressures for 0, 6.25, and 100 mol% charge coupled Al_2O_3 incorporation and simple solution theories, we estimate the phase diagram of Al-bearing MgSiO_3 at low Al concentrations. Assuming the Clapeyron slope is independent of Al concentration, we find the perovskite-to-post-perovskite transition region to span 127–140 GPa, at 6.25 mol% Al_2O_3. When the upper pressure limit is bounded by the core-mantle boundary, the phase coexistence region has width 150 km

Computer studies of hybrid-slotted working sections with minimum interference at subsonic speeds

A series of computations on tunnel boundary-interference effects for hybrid-slotted working sections was performed using the WALINT code. The slots were modeled as lines of porosity with linear crossflow characteristics. The basic shape evaluated was for a rectangular section with height-to-width ratio = 0.835 and its companion in the duplex mode (half model testing) with height-to-width ratio = 0.6. A best overall basic configuration was determined with seven slots on each wall with open area ratio on each wall of 17.5%. For both full-span and half-model testing, the optimum solution required closing all but two slots on each of the half-walls parallel to the plane of the wing (equivalent to four slots on the full floor and ceiling). The results are presented here for the best configurations and are shown to be within the figure-of-merit range of + or - 0.04 in upwash, and + or - 0.1 in curvature for the Mach number range 0.6 to 0.85. Blockage effects are shown to be small