11,803 research outputs found
Modeling the near-UV band of GK stars, Paper II: NLTE models
We present a grid of atmospheric models and synthetic spectral energy
distributions (SEDs) for late-type dwarfs and giants of solar and 1/3 solar
metallicity with many opacity sources computed in self-consistent Non-Local
Thermodynamic Equilibrium (NLTE), and compare them to the LTE grid of Short &
Hauschildt (2010) (Paper I). We describe, for the first time, how the NLTE
treatment affects the thermal equilibrium of the atmospheric structure (T(tau)
relation) and the SED as a finely sampled function of Teff, log g, and [A/H]
among solar metallicity and mildly metal poor red giants. We compare the
computed SEDs to the library of observed spectrophotometry described in Paper I
across the entire visible band, and in the blue and red regions of the spectrum
separately. We find that for the giants of both metallicities, the NLTE models
yield best fit Teff values that are ~30 to 90 K lower than those provided by
LTE models, while providing greater consistency between \log g values, and, for
Arcturus, Teff values, fitted separately to the blue and red spectral regions.
There is marginal evidence that NLTE models give more consistent best fit Teff
values between the red and blue bands for earlier spectral classes among the
solar metallicity GK giants than they do for the later classes, but no model
fits the blue band spectrum well for any class. For the two dwarf spectral
classes that we are able to study, the effect of NLTE on derived parameters is
less significant.Comment: Submitted to The Astrophysical Journal. Observed spectrophotometric
library, and grids of NLTE and LTE) synthetic spectra for GK stars available
at http://www.ap.smu.ca/~ishort/PHOENI
Combining Semi-Analytic Models of Galaxy Formation with Simulations of Galaxy Clusters: the Need for AGN Heating
We present hydrodynamical N-body simulations of clusters of galaxies with
feedback taken from semi-analytic models of galaxy formation. The advantage of
this technique is that the source of feedback in our simulations is a
population of galaxies that closely resembles that found in the real universe.
We demonstrate that, to achieve the high entropy levels found in clusters,
active galactic nuclei must inject a large fraction of their energy into the
intergalactic/intracluster media throughout the growth period of the central
black hole. These simulations reinforce the argument of Bower et al. (2008),
who arrived at the same conclusion on the basis of purely semi-analytic
reasoning.Comment: 4 pages, 1 figure. To appear in the proceedings of "The Monster's
Fiery Breath", Eds. Sebastian Heinz and Eric Wilcots (AIP conference series
Research-Practice-Policy Partnerships for Implementation of Evidence-Based Practices in Child Welfare and Child Mental Health
Partnerships between researchers, practitioners, and policymakers represent a promising avenue for improving outcomes for young people and families.In a new report, Lawrence Palinkas, Cherry Short, and Marleen Wong of the University of Southern California's School of Social Work suggest that research-practice-policy partnerships may help narrow the gap between the development of evidence-based services for young people in the child welfare and mental health systems and the routine delivery of these services.Describing the structure and operations of partnerships, and the potential challenges to making them work, Palinkas and colleagues present three models of successful partnerships in the child welfare and mental health systems. Case studies for each model provide rich examples of the common elements and central themes that characterize the value of partnerships as a strategy for delivering high quality services in high demand settings
Occurrence of the Plains Harvest Mouse, Reithrondontomys montanus (Baird) in Arkansas
Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201
Quantum equilibration in finite time
It has recently been shown that small quantum subsystems generically
equilibrate, in the sense that they spend most of the time close to a fixed
equilibrium state. This relies on just two assumptions: that the state is
spread over many different energies, and that the Hamiltonian has
non-degenerate energy gaps. Given the same assumptions, it has also been shown
that closed systems equilibrate with respect to realistic measurements. We
extend these results in two important ways. First, we prove equilibration over
a finite (rather than infinite) time-interval, allowing us to bound the
equilibration time. Second, we weaken the non degenerate energy gaps condition,
showing that equilibration occurs provided that no energy gap is hugely
degenerate.Comment: 7 page
Evaluation of a Wake Vortex Upset Model Based on Simultaneous Measurements of Wake Velocities and Probe-Aircraft Accelerations
Simultaneous measurements were made of the upset responses experienced and the wake velocities encountered by an instrumented Learjet probe aircraft behind a Boeing 747 vortex-generating aircraft. The vortex-induced angular accelerations experienced could be predicted within 30% by a mathematical upset response model when the characteristics of the wake were well represented by the vortex model. The vortex model used in the present study adequately represented the wake flow field when the vortices dissipated symmetrically and only one vortex pair existed in the wake
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