The average X-ray/gamma-ray spectrum of radio-quiet Seyfert 1s

We have obtained the average 1--500 keV spectrum of radio-quiet Seyfert 1s using data from EXOSAT, Ginga, HEAO, and GRO/OSSE. The spectral fit to the combined average EXOSAT and OSSE data is fully consistent with that for Ginga and OSSE, confirming results from an earlier Ginga/OSSE sample. The average spectrum is well-fitted by a power-law X-ray continuum with an energy spectral index of $\alpha \simeq 0.9$ moderately absorbed by an ionized medium and with a Compton reflection component. A high-energy cutoff (or a break) in the the power-law component at a few hundred keV or more is required by the data. We also show that the corresponding average spectrum from HEAO A1 and A4 is fully compatible with that obtained from EXOSAT, Ginga and OSSE. These results confirm that the apparent discrepancy between the results of Ginga (with $\alpha \simeq 0.9$) and the previous results of EXOSAT and HEAO (with $\alpha \simeq 0.7$) is indeed due to ionized absorption and Compton reflection first taken into account for Ginga but not for the previous missions. Also, our results confirm that the Seyfert-1 spectra are on average cut off in gamma-rays at energies of at least a few hundred keV, not at $\sim 40$ keV (as suggested earlier by OSSE data alone). The average spectrum is compatible with emission from either an optically-thin relativistic thermal plasma in a disk corona, or with a nonthermal plasma with a power-law injection of relativistic electrons.Comment: 7 pages, 3 Postscript figures, MNRAS accepte

A Team-Based Practicum Bringing Together Students Across Educational Institutions and Health Professions

Objective. To assess student perceptions of teamwork during an interprofessional exercise and to evaluate if students could identify domestic violence through a standardized patient interview. Design. Medical, pharmacy, nursing, physical therapy, and social work students were assigned to teams to interview and examine a patient with a “cut on the hand” later revealed a result of domestic violence. They also practiced suturing technique and developed a patient care plan. A postexercise survey was administered. Assessment. From 70% to 94% of students surveyed agreed or strongly agreed, respectively, that their responsibilities were clear. All (100%) recognized the benefits of team-based care. Only 38% of the medical students reported team members providing insight into domestic violence, and 52% did not recognize team members as resources for these cases. Conclusion. Students gained perspective of knowledge and responsibilities of each team member. However, the results suggest further enhancements of curriculum related to domestic violence are needed

Edge enhancement improves disruptive camouflage by emphasising false edges and creating pictorial relief

Disruptive colouration is a visual camouflage composed of false edges and boundaries. Many disruptively camouflaged animals feature enhanced edges; light patches are surrounded by a lighter outline and/or a dark patches are surrounded by a darker outline. This camouflage is particularly common in amphibians, reptiles and lepidopterans. We explored the role that this pattern has in creating effective camouflage. In a visual search task utilising an ultra-large display area mimicking search tasks that might be found in nature, edge enhanced disruptive camouflage increases crypsis, even on substrates that do not provide an obvious visual match. Specifically, edge enhanced camouflage is effective on backgrounds both with and without shadows; i.e. this is not solely due to background matching of the dark edge enhancement element with the shadows. Furthermore, when the dark component of the edge enhancement is omitted the camouflage still provided better crypsis than control patterns without edge enhancement. This kind of edge enhancement improved camouflage on all background types. Lastly, we show that edge enhancement can create a perception of multiple surfaces. We conclude that edge enhancement increases the effectiveness of disruptive camouflage through mechanisms that may include the improved disruption of the object outline by implying pictorial relief

Extracting particle freeze-out phase-space densities and entropies from sources imaged in heavy-ion reactions

The space-averaged phase-space density and entropy per particle are both fundamental observables which can be extracted from the two-particle correlation functions measured in heavy-ion collisions. Two techniques have been proposed to extract the densities from correlation data: either by using the radius parameters from Gaussian fits to meson correlations or by using source imaging, which may be applied to any like pair correlation. We show that the imaging and Gaussian fits give the same result in the case of meson interferometry. We discuss the concept of an equivalent instantaneous source on which both techniques rely. We also discuss the phase-space occupancy and entropy per particle. Finally, we propose an improved formula for the phase-space occupancy that has a more controlled dependence on the uncertainty of the experimentally measured source functions.Comment: 14 pages, final version, to appear PRC. Fixed typos, added refs. for last section, added discussions of imaging and d/p ratio

Portrait of Abraham Lincoln, President 1861-1865

A black and white portrait illustration of Abraham Lincoln from Brown\u27s Famous Pictures collection. The print was found behind another print (inventory # 6981) in a frame, but was removed for preservation.https://scholarsjunction.msstate.edu/fvw-prints/1190/thumbnail.jp

Dark cloud cores and gravitational decoupling from turbulent flows

We test the hypothesis that the starless cores may be gravitationally bound clouds supported largely by thermal pressure by comparing observed molecular line spectra to theoretical spectra produced by a simulation that includes hydrodynamics, radiative cooling, variable molecular abundance, and radiative transfer in a simple one-dimensional model. The results suggest that the starless cores can be divided into two categories: stable starless cores that are in approximate equilibrium and will not evolve to form protostars, and unstable pre-stellar cores that are proceeding toward gravitational collapse and the formation of protostars. The starless cores might be formed from the interstellar medium as objects at the lower end of the inertial cascade of interstellar turbulence. Additionally, we identify a thermal instability in the starless cores. Under par ticular conditions of density and mass, a core may be unstable to expansion if the density is just above the critical density for the collisional coupling of the gas and dust so that as the core expands the gas-dust coupling that cools the gas is reduced and the gas warms, further driving the expansion.Comment: Submitted to Ap

Virtual reality:a tool for investigating camouflage

Disruptive camouflage utilises high-contrast patches, typically positioned at the margins of an object to impede the detection and/or recognition of a perceiver. To date, the predominant methods for examining camouflage strategies are computer-based (i.e., detection experiments), field-based (e.g., survival analyses) and camouflage choice experiments using dynamically coloured organisms (e.g., cephalopods). Recent advances in virtual reality (VR) technology present the opportunity to create novel environments for testing camouflage theory. VR can combine the control of lab-based research with the ecological validity of field-based studies. Here, we develop an experimental paradigm that enables camouflage testing within a virtual reality environment. The environment comprised a spherical target that can be wrapped with different camouflage patterns and a domed background, upon which a natural image can be projected. Participants were positioned within the centre of the dome and were tasked with finding and shooting at targets randomly positioned across a bounded range within the environment. We manipulated the luminance contrast (0–2 steps of 2.5 L *) of disruptive and edge-enhancement (EE) components of the camouflage patterning to examine their impact on participant response time. Having high, but not extreme, contrast resulted in increased camouflage effectiveness. The EE component had no effect independently but interacted with the DC component. Specifically, when using EE alongside DC, a lower contrast EE component is more effective than a higher contrast EE component. Our results demonstrate that VR is a viable research tool for testing camouflage theory

Quiescent Thermal Emission from the Neutron Star in Aql X-1

We report on the quiescent spectrum measured with Chandra/ACIS-S of the transient, type-I X-ray bursting neutron star Aql X-1, immediately following an accretion outburst. The neutron star radius, assuming a pure hydrogen atmosphere and hard power-law spectrum, is $R_\infty$=13.4{+5}{-4} (d/5 \kpc) km. Based on the historical outburst record of RXTE/ASM, the quiescent luminosity is consistent with that predicted by Brown, Bildsten and Rutledge from deep crustal heating, lending support to this theory for providing a minimum quiescent luminosity of transient neutron stars. While not required by the data, the hard power-law component can account for 18+/-8% of the 0.5-10 keV thermal flux. Short-timescale intensity variability during this observation is less than 15% rms (3 sigma; 0.0001-1 Hz, 0.2-8 keV). Comparison between the Chandra spectrum and three X-ray spectral observations made between Oct 1992 and Oct 1996 find all spectra consistent with a pure H atmosphere, but with temperatures ranging from 145--168 eV, spanning a factor of 1.87+/-0.21 in observed flux. The source of variability in the quiescent luminosity on long timescales (greater than years) remains a puzzle. If from accretion, then it remains to be explained why the quiescent accretion rate provides a luminosity so nearly equal to that from deep crustal heating.Comment: 15 pages, 1 figure, 2 tables; ApJ, accepte

Plasma Physics

Contains research objectives and reports on two research projects.U.S. Atomic Energy Commission (Contract AT(30-1)-1842)U.S. Air Force (Electronic Systems Division) under Contract AF19(604)-5992National Science Foundation (Grant G-24073