126 research outputs found
Spatially Varying X-ray Synchrotron Emission in SN 1006
A growing number of both galactic and extragalactic supernova remnants show
non-thermal (non-plerionic) emission in the X-ray band. New synchrotron models,
realized as SRESC and SRCUT in XSPEC 11, which use the radio spectral index and
flux as inputs and include the full single-particle emissivity, have
demonstrated that synchrotron emission is capable of producing the spectra of
dominantly non-thermal supernova remnants with interesting consequences for
residual thermal abundances and acceleration of particles. In addition, these
models deliver a much better-constrained separation between the thermal and
non-thermal components, whereas combining an unconstrained powerlaw with modern
thermal models can produce a range of acceptable fits. While synchrotron
emission can be approximated by a powerlaw over small ranges of energy, the
synchrotron spectrum is in fact steepening over the X-ray band. Having
demonstrated that the integrated spectrum of SN 1006, a remnant dominated by
non-thermal emission, is well described by synchrotron models I now turn to
spatially resolved observations of this well studied remnant. The synchrotron
models make both spectral and spatial predictions, describing how the
non-thermal emission varies across the remnant. Armed with spatially resolved
non-thermal models and new thermal models such as VPSHOCK we can now dissect
the inner workings of SN 1006.Comment: 4 pages, 4 figures. To appear in "Young Supernova Remnants" the 11th
Annual October Maryland Astrophysics Conference AIP eds. Steve Holt and Una
Hwan
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Communication Climate in a Health Care Setting : A Case Study
The climate in which communication occurs is a result of
how employees in an organization perceive and react to such
factors as rewards, support, trust, openness, decision making,
and leadership. The purpose of this case study is to identify
and describe communication climate factors in a health care
organization which are negatively influencing employee
productivity and morale.
A literature review provides information which describes
research in areas of health care communication,
communication climate, and leadership. A multi-method
approach is used to gather information from the twelve
employees and the manager of this organization
Spatial Attention Modulates Center-Surround Interactions in Macaque Visual Area V4
SummaryIn natural viewing, a visual stimulus that is the target of attention is generally surrounded by many irrelevant distracters. Stimuli falling in the receptive field surround can influence the neuronal response evoked by a stimulus appearing within the classical receptive field. Such modulation by task-irrelevant distracters may degrade the target-related neuronal signal. We therefore examined whether directing attention to a target stimulus can reduce the influence of task-irrelevant distracters on neuronal response. We find that in area V4 attention to a stimulus within a neuron's receptive field filters out a large fraction of the suppression induced by distracters appearing in the surround. When attention is instead directed to the surround stimulus, suppression is increased, thereby filtering out part of the neuronal response to the irrelevant distracter positioned within the receptive field. These findings demonstrate that attention modulates the neural mechanisms that give rise to center-surround interactions
On the Deployment of DHCP
Constant-time symmetries and e-business have garnered great interest from both researchers and developers in the last several years. In this paper, authors confirm the analysis of interrupts. We describe a heuristic for stable models, which we call ViagePadge
Hedonic shopping motivations in collectivistic and individualistic consumer cultures
We reinvestigate what constitutes hedonic customer experiences in collectivistic versus individualistic cultures using four country samples (N=2,336) in Germany and the U.S. as well as Oman and India. Across country samples, intrinsically enjoyable customer experiences are associated with the same underlying hedonic shopping motivations as shown in the original U.S. context. In comparison with individualistic cultures, we find that a hedonic shopping experience in collectivistic cultures is less strongly associated with selforiented gratification shopping, yet more strongly associated with others-oriented role shopping
Understanding the customer base of service providers: An examination of the differences between switchers and stayers
Creating and maintaining customer loyalty has become a strategic mandate in today\u27s service markets. Recent research suggests that customers differ in their value to a firm, and therefore customer retention and loyalty-building efforts should not necessarily be targeted to all customers of a firm. Given these sentiments, it is becoming increasingly necessary for firms to have a thorough understanding of their customer base. Yet current knowledge is limited in providing insights to firms regarding the differences within their customer base. This research comprises two studies in which the authors examine the differences among internal customer groups in a service industry. As theory suggests and as is empirically validated here, customers who have switched service providers because of dissatisfaction seem to differ significantly from other customer groups in their satisfaction and loyalty behaviors, The findings offer some interesting implications for both marketing theory and practice
X-Ray Synchrotron Emitting Fe-Rich Ejecta in SNR RCW 86
Supernova remnants may exhibit both thermal and nonthermal X-ray emission. We
present Chandra observations of RCW 86. Striking differences in the morphology
of X-rays below 1 keV and above 2 keV point to a different physical origin.
Hard X-ray emission is correlated fairly well with the edges of regions of
radio emission, suggesting that these are the locations of shock waves at which
both short-lived X-ray emitting electrons, and longer-lived radio-emitting
electrons, are accelerated. Soft X-rays are spatially well-correlated with
optical emission from nonradiative shocks, which are almost certainly portions
of the outer blast wave. These soft X-rays are well fit with simple thermal
plane-shock models. Harder X-rays show Fe K alpha emission and are well
described with a similar soft thermal component, but a much stronger
synchrotron continuum dominating above 2 keV, and a strong Fe K alpha line.
Quantitative analysis of this line and the surrounding continuum shows that it
cannot be produced by thermal emission from a cosmic-abundance plasma; the
ionization time is too short, as shown both by the low centroid energy (6.4
keV) and the absence of oxygen lines below 1 keV. Instead, a model of a plane
shock into Fe-rich ejecta, with a synchrotron continuum, provides a natural
explanation. This requires that reverse shocks into ejecta be accelerating
electrons to energies of order 50 TeV. We show that maximum energies of this
order can be produced by radiation-limited diffusive shock acceleration at the
reverse shocks.Comment: ApJ, accepted; full resolution images in
http://spider.ipac.caltech.edu/staff/rho/rcw86chandra.p
Thermal and Nonthermal X-Ray Emission in SNR RCW 86
Supernova remnants may exhibit both thermal and nonthermal X-ray emission.
Such remnants can be distinguished by the weakness of their X-ray lines,
because of the presence of a strong nonthermal X-ray continuum. RCW 86 is a
remnant with weak lines, resulting in low and peculiar abundances when thermal
models alone are used to interpret its X-ray spectrum. This indicates the
presence of a strong nonthermal synchrotron continuum. We analyze ASCA X-ray
spectra of RCW 86 with the help of both nonequilibrium ionization thermal
models and nonthermal synchrotron models. A two-temperature thermal model and a
simple nonthermal model with an exponential cutoff (plus interstellar
absorption) give reasonable results. We obtain blast wave velocity of 800 km/s,
the shock ionization age of 1-3x10^11 s/cm^3, and the break in nonthermal
spectra at 2-4x10^16 Hz. The strength of nonthermal continuum correlates well
with the radio brightness in the bright SW section of the remnant. This is
convincing evidence for X-ray synchrotron emission in RCW 86.Comment: 14 pages, 11 figures, submitted to Astrophysical Journa
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