40,280 research outputs found
Do Two Temperature Debris Disks Have Multiple Belts?
We present a study of debris disks whose spectra are well modelled by dust
emission at two different temperatures. These disks are typically assumed to be
a sign of multiple belts, which in only a few cases have been confirmed via
high resolution observations. We first compile a sample of two-temperature
disks to derive their properties, summarised by the ratios of the warm and cool
component temperatures and fractional luminosities. The ratio of warm to cool
temperatures is constant in the range 2-4, and the temperatures of both warm
and cool components increases with stellar mass. We then explore whether this
emission can arise from dust in a single narrow belt, with the range of
temperatures arising from the size variation of grain temperatures. This model
can produce two-temperature spectra for Sun-like stars, but is not supported
where it can be tested by observed disk sizes and far-IR/mm spectral slopes.
Therefore, while some two-temperature disks arise from single belts, it is
probable that most have multiple spatial components. These disks are plausibly
similar to the outer Solar System's configuration of Asteroid and
Edgeworth-Kuiper belts separated by giant planets. Alternatively, the inner
component could arise from inward scattering of material from the outer belt,
again due to intervening planets. In either case, we suggest that the ratio of
warm/cool component temperatures is indicative of the scale of outer planetary
systems, which typically span a factor of about ten in radius.Comment: accepted to MNRA
Making the small oblique parameters large
We compute the oblique parameters, including the three new parameters ,
and introduced recently by the Montreal group, for the case of one
scalar multiplet of arbitrary weak isospin and weak hypercharge . We
show that, when the masses of the heaviest and lightest components of the
multiplet remain constant, but increases, the oblique parameter and
the three new oblique parameters increase like , while only
increases like . For large multiplets with masses not much higher than , the oblique parameters and may become much larger than
and .Comment: 9 pages, standard LATEX, 3 figures available from the authors, report
CMU-HEP93-17 and DOE-ER/40682-4
Immunoreactivity for a calmodulin-dependent protein kinase is selectively increased in macaque striate cortex after monocular deprivation
Immunocytochemical methods were used to localize type II Ca2+/calmodulin-dependent protein kinase in the macaque primary visual cortex. Neurons that stain for the kinase include both pyramidal and nonpyramidal cells and they appear to form a subset of cortical neurons. They are densely packed in layers II and IVB, somewhat more sparse in layers III, IVCĂź, and VI, and nearly absent in layer V. In normal animals the distribution of kinase-positive cells within each layer is relatively uniform. However, in animals in which one eye is removed 7-14 days before sacrifice or sutured shut for 9 or 11 weeks, the cells in layer IVCĂź are divided into alternating lightly and darkly stained bands. Comparison of immunocytochemically stained sections with adjacent sections stained for the mitochondrial enzyme, cytochrome oxidase, reveals that the kinase staining increases in ocular dominance columns originally driven by the removed or closed eye. These findings suggest that either the concentration of type II Ca2+/calmodulin-dependent protein kinase or its accessibility to the antibody probe increases dramatically and selectively in neurons of macaque primary visual cortex that have been deprived of their normal visual input. This may indicate that changing levels of activity in cortical neurons can alter their regulatory machinery
The Sure Start Mellow Valley area Through the lens of a camera
This report gives an account of a participatory evaluation conducted using photography within the Sure Start Mellow Valley area. Information about the current status of the Sure Start programme and the plans for the future are first provided. The report then describes the research that was undertaken and presents and discusses the findings
Emulation of multivariate simulators using thin-plate splines with application to atmospheric dispersion
It is often desirable to build a statistical emulator of a complex computer simulator in order to perform analysis which would otherwise be computationally infeasible. We propose methodology to model multivariate output from a computer simulator taking into account output structure in the responses. The utility of this approach is demonstrated by applying it to a chemical and biological hazard prediction model. Predicting the hazard area which results from an accidental or deliberate chemical or biological release is imperative in civil and military planning and also in emergency response. The hazard area resulting from such a release is highly structured in space and we therefore propose the use of a thin-plate spline to capture the spatial structure and fit a Gaussian process emulator to the coefficients of the resultant basis functions. We compare and contrast four different techniques for emulating multivariate output: dimension-reduction using (i) a fully Bayesian approach with a principal component basis, (ii) a fully Bayesian approach with a thin-plate spline basis, assuming that the basis coefficients are independent, and (iii) a “plug-in” Bayesian approach with a thin-plate spline basis and a separable covariance structure; and (iv) a functional data modeling approach using a tensor-product (separable) Gaussian process. We develop methodology for the two thin-plate spline emulators and demonstrate that these emulators significantly outperform the principal component emulator. Further, the separable thin-plate spline emulator, which accounts for the dependence between basis coefficients, provides substantially more realistic quantification of uncertainty, and is also computationally more tractable, allowing fast emulation. For high resolution output data, it also offers substantial predictive and computational ad- vantages over the tensor-product Gaussian process emulator
Development of the health and economic consequences of smoking interactive model
Objective-To describe the health and economic consequences of smoking model, a user friendly, web based tool, designed to estimate the health and economic outcomes associated with smoking and the benefits of smoking cessation. Results-An overview of the development of the model equations and user interface is given, and data from the UK are presented as an example of the model outputs. These results show that a typical smoking cessation strategy costs approximately pound 1200 per life year saved and pound 22 000 per death averted. Conclusions-The model successfully captures the complexity required to model smoking behaviour and associated mortality, morbidity, and health care costs. Furthermore, the interface provides the results in a simple and flexible way so as to be useful to a variety of audiences and to simulate a variety of smoking cessation methods
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