147 research outputs found
Half-space general multigroup transport theory
A method for solving various half-space multigroup transport problems for the case of a general transfer matrix is explained. A non-linear integral equation for the emergent distribution of the albedo problem is derived. Then, by using the full-range completeness of the infinite medium eigenfunctions, the distribution inside the half-space is obtained from the emergent distribution. Finally, the Milne problem and the half-space Green's function problem are solved in terms of the emergent distribution of the albedo problem and the infinite medium eigenfunctions.One advantage of this method is that it readily yields numerical results for emergent distributions of half-space problems. Even for the numerical evaluation of a particular solution inside the half-space, this technique is felt to be superior to other exact half-space methods since only full-range eigenfunction expansions are employed rather than the more difficult half-range expansion used in other techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32922/1/0000304.pd
The Maximal Runaway Temperature of Earth-like Planets
We generalize the problem of the semi-gray model to cases in which a
non-negligible fraction of the stellar radiation falls on the long-wavelength
range, and/or that the planetary long-wavelength emission penetrates into the
transparent short wavelength domain of the absorption.
Second, applying the most general assumptions and independently of any
particular properties of an absorber, we show that the greenhouse effect
saturates and any Earth-like planet has a maximal temperature which depends on
the type of and distance to its main-sequence star, its albedo and the primary
atmospheric components which determine the cutoff frequency below which the
atmosphere is optically thick. For example, a hypothetical convection-less
planet similar to Venus, that is optically thin in the visible, could have at
most a surface temperature of 1200-1300K irrespective of the nature of the
greenhouse gas.
We show that two primary mechanisms are responsible for the saturation of the
runaway greenhouse effect, depending on the value of the wavelength above which
the atmosphere becomes optically thick. Unless this wavelength is small and
resides in the optical region, saturation is achieved by radiating the thermal
flux of the planet through the short wavelength tail of the thermal
distribution. This has the observational implication, the radiation from such a
planet should be skewed towards the NIR. Otherwise, saturation takes place by
radiating through windows in the FIR.Comment: 13 pages 14 figure
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Application of discrete ordinates and Monte Carlo methods to transport of photons from environmental sources
Federal Guidance Report No. 12 tabulates dose coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, water, and soil. Although the dose coefficients of this report are based on previously developed dosimetric methodologies, they are derived from new, detailed calculations of energy and angular distributions of the radiations incident on the body and the transport of these radiations within the body. Effort was devoted to expanding the information available for assessment of radiation dose from radionuclides distributed on or below the surface of the ground. A companion paper (External Exposure to Radionuclides in Air, Water, and Soil) discusses the significance of the new tabulations of coefficients and provides detiled comparisons to previously published values. This paper discusses details of the photon transport calculations
Exact results in modeling planetary atmospheres--I. Gray atmospheres
An exact model is proposed for a gray, isotropically scattering planetary
atmosphere in radiative equilibrium. The slab is illuminated on one side by a
collimated beam and is bounded on the other side by an emitting and partially
reflecting ground. We provide expressions for the incident and reflected fluxes
on both boundary surfaces, as well as the temperature of the ground and the
temperature distribution in the atmosphere, assuming the latter to be in local
thermodynamic equilibrium. Tables and curves of the temperature distribution
are included for various values of the optical thickness. Finally,
semi-infinite atmospheres illuminated from the outside or by sources at
infinity will be dealt with.Comment: 29 pages, 1 figure, Journal of Quantitative Spectroscopy and
Radiative Transfer (www.elsevier.com/locate/jqsrt), accepted 11 September
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A Systematic Review of Music Therapy Practice and Outcomes with Acute Adult Psychiatric In-Patients
PMCID: PMC3732280This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Force-induced remodelling of proteins and their complexes
Force can drive conformational changes in proteins, as well as modulate their stability and the affinity of their complexes, allowing a mechanical input to be converted into a biochemical output. These properties have been utilised by nature and force is now recognised to be widely used at the cellular level. The effects of force on the biophysical properties of biological systems can be large and varied. As these effects are only apparent in the presence of force, studies on the same proteins using traditional ensemble biophysical methods can yield apparently conflicting results. Where appropriate, therefore, force measurements should be integrated with other experimental approaches to understand the physiological context of the system under study
Uncertainties in the Anti-neutrino Production at Nuclear Reactors
Anti-neutrino emission rates from nuclear reactors are determined from
thermal power measurements and fission rate calculations. The uncertainties in
these quantities for commercial power plants and their impact on the calculated
interaction rates in electron anti-neutrino detectors is examined. We discuss
reactor-to-reactor correlations between the leading uncertainties and their
relevance to reactor anti-neutrino experiments.Comment: Submitted to Phys Rev
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