13,054 research outputs found
The Construction of Spinor Fields on Manifolds with Smooth Degenerate Metrics
We examine some of the subtleties inherent in formulating a theory of spinors
on a manifold with a smooth degenerate metric. We concentrate on the case where
the metric is singular on a hypersurface that partitions the manifold into
Lorentzian and Euclidean domains. We introduce the notion of a complex spinor
fibration to make precise the meaning of continuity of a spinor field and give
an expression for the components of a local spinor connection that is valid in
the absence of a frame of local orthonormal vectors. These considerations
enable one to construct a Dirac equation for the discussion of the behavior of
spinors in the vicinity of the metric degeneracy. We conclude that the theory
contains more freedom than the spacetime Dirac theory and we discuss some of
the implications of this for the continuity of conserved currents.Comment: 24 pages, LaTeX (RevTeX 3.0, no figures), To appear in J. Math. Phy
Associations between EP-like lesions and pleuritis and post trimming carcass weights of finishing pigs in England
Herd health slaughter checks regularly identify enzootic pneumonia-like (EP-like) lesions and pleuritis. The aim of this paper is to determine the associations between these lesions and post-trimming carcass weight. Data were collected on the presence/absence and severity of EP-like lesions and presence/absence of pleuritis from pigs at the abattoir. Linear mixed models identified a significant association between an increase in EP-like lesion severity and a decrease in post-trimming carcass weight (P = 0.006) at the individual level. Each categorical increase in EP-like lesion severity (5 points step) was associated with a 0.37 kg reduction in post-trimming carcass weight. The presence of EP-like lesions in individual pigs, irrespective of severity (P = 0.034) and the presence of pleuritis (P = 0.038) were significantly associated with a reduction in post-trimming carcass weight of 1.26 kg and 1.25 kg respectively. The results confirm that the presence of these lesions at slaughter are associated with a significant decrease in production performance which can result in substantial economic implications for producers
The GSFC Mark-2 three band hand-held radiometer
A self-contained, portable, hand-radiometer designed for field usage was constructed and tested. The device, consisting of a hand-held probe containing three sensors and a strap supported electronic module, weighs 4 1/2 kilograms. It is powered by flashlight and transistor radio batteries, utilizes two silicon and one lead sulfide detectors, has three liquid crystal displays, sample and hold radiometric sampling, and its spectral configuration corresponds to LANDSAT-D's thematic mapper bands. The device was designed to support thematic mapper ground-truth data collection efforts and to facilitate 'in situ' ground-based remote sensing studies of natural materials. Prototype instruments were extensively tested under laboratory and field conditions with excellent results
Maxwell's Equations in a Uniformly Rotating Dielectric Medium and the Wilson-Wilson Experiment
This note offers a conceptually straightforward and efficient way to
formulate and solve problems in the electromagnetics of moving media based on a
representation of Maxwell's equations in terms of differential forms on
spacetime together with junction conditions at moving interfaces. This
framework is used to address a number of issues that have been discussed
recently in this journal about the theoretical description underlying the
interpretation of the Wilson-Wilson experiment.Comment: 16 pages, 2 figure
Liquor Referendum: Interest Group Activities and the Public Opinion Process: A Case Study of a Liquor Referendum
A computer operated mass spectrometer system
Digital computer system for processing mass spectrometer output dat
- …