14,116 research outputs found
The kinematic Sunyaev Zeldovich effect and transverse cluster velocities
The polarization of the CMBR scattered by galaxy clusters in the kinematic
Sunyaev Zeldovich effect depends on the transverse velocity of the cluster.
This polarizing effect is proportional to the transverse velocity squared, and
so weaker that the change in intensity due to the radial motion in the
kinematic effect. The value given by Sunyaev and Zeldovich, and which is
frequently cited, underestimates the polarizing effect by a factor of ten. We
show furthermore that the polarization has a strong frequency dependence. This
means that the polarization should be detectable with the new generation of
CMBR probes, at least for some clusters. Thus this effect offers, almost
uniquely, a method of obtaining the vectorial velocity of clusters.Comment: Submitted to MNRAS letter. 5 pages using mnras file style. email:
[email protected]
The use of light polarization for weak-lensing inversions
The measurement of the integrated optical polarization of weakly
gravitationally lensed galaxies can provide considerable constraints on lens
models. The method outlined depends on fact that the orientation of the
direction of optical polarization is not affected by weak gravitational
lensing. The angle between the semi-major axis of the imaged galaxy and the
direction of integrated optical polarization thus informs one of the distortion
produced by the gravitational lensing. Although the method depends on the
polarimetric measurement of faint galaxies, large telescopes and improved
techniques should make such measurements possible in the near future.Comment: 13 pages, 11 figures, uses mnras style file. Accepted for publication
in MNRA
Optimal Galaxy Distance Estimators
The statistical properties of galaxy distance estimators are studied and a
rigorous framework is developed for identifying and removing the effects of
Malmquist bias due to obsevational selection. The prescription of Schechter
(1980) for defining unbiased distance estimators is extended to more general --
and more realistic -- cases. The derivation of `optimal' unbiased distance
estimators of minimum dispersion, by utilising information from additional --
suitably correlated -- observables, is discussed and the results applied to a
calibrating sample from the Fornax cluster, as used in the Mathewson spiral
galaxy redshift survey. The optimal distance estimator derived from I-band
magnitude, diameter and 21cm line width has an intrinsic scatter which is 25 \%
smaller than that of the Tully-Fisher relation quoted for this calibrating
sample. (Figures are available on request).Comment: Plain Latex, 19 pages, Sussex-AST-93/9-
The Need for Higher Minimum Staffing Standards in U.S. Nursing Homes.
Many U.S. nursing homes have serious quality problems, in part, because of inadequate levels of nurse staffing. This commentary focuses on two issues. First, there is a need for higher minimum nurse staffing standards for U.S. nursing homes based on multiple research studies showing a positive relationship between nursing home quality and staffing and the benefits of implementing higher minimum staffing standards. Studies have identified the minimum staffing levels necessary to provide care consistent with the federal regulations, but many U.S. facilities have dangerously low staffing. Second, the barriers to staffing reform are discussed. These include economic concerns about costs and a focus on financial incentives. The enforcement of existing staffing standards has been weak, and strong nursing home industry political opposition has limited efforts to establish higher standards. Researchers should study the ways to improve staffing standards and new payment, regulatory, and political strategies to improve nursing home staffing and quality
Entrainment characteristics of unsteady subsonic jets
The effectiveness of jet unsteadiness in enhancing flow entrainment was assessed. It was conducted that entrainment depends on the type and amount of jet unsteadiness. Apparently, the mere introduction of jet unsteadiness by small sinusoidal flow angle variations is insufficient to enhance entrainment but, it should be noted that the results were obtained at measuring stations which are all many nozzle widths downstream of the jet nozzle. Thus, no fully conclusive statement can be made at this time about the entrainment close to the nozzle. The high entrainment of the fluidically oscillated jet was caused by the high-frequency content of this square wave type of oscillation but more detailed measurements are clearly needed, in particular for the fluidically oscillated and the pulsed jets. Practical ejector application requires the proper trade-off between entrainment and primary nozzle thrust efficiency
Inversion of polarimetric data from eclipsing binaries
We describe a method for determining the limb polarization and limb darkening
of stars in eclipsing binary systems, by inverting photometric and polarimetric
light curves.
Because of the ill-conditioning of the problem, we use the Backus-Gilbert
method to control the resolution and stability of the recovered solution, and
to make quantitative estimates of the maximum accuracy possible. Using this
method we confirm that the limb polarization can indeed be recovered, and
demonstrate this with simulated data, thus determining the level of
observational accuracy required to achieve a given accuracy of reconstruction.
This allows us to set out an optimal observational strategy, and to critcally
assess the claimed detection of limb polarization in the Algol system.
The use of polarization in stars has been proposed as a diagnostic tool in
microlensing surveys by Simmons et al. (1995), and we discuss the extension of
this work to the case of microlensing of extended sources.Comment: 10pp, 5 figures. To appear in A&
Biology, Injury, and Control of the European Needle-bending Midge (Diptera: Cecidomyiidae) on Scotch Pine in Michigan
Contarinia baeri is univoltine in Michigan. Adults emerge in spring, and females deposit eggs in small clusters in the sheaths of new-growth pine needles. Larvae hatch shortly thereafter and there are three larval instars. Larval feeding causes the needles to at first droop, discolor, and eventually drop, reducing the quality of Christmas trees and occasionally killing shoots. Larvae overwinter on the ground in cocoons, and pupate in spring. Adults were suppressed (\u3e 75% control) with formulations of Pydrin® (fenvalerate) and Tempo® (cyfluthrin) applied within a week after adult emergence
Linear Stability Analysis of Symmetric Periodic Simultaneous Binary Collision Orbits in the Planar Pairwise Symmetric Four-Body Problem
We apply the symmetry reduction method of Roberts to numerically analyze the
linear stability of a one-parameter family of symmetric periodic orbits with
regularizable simultaneous binary collisions in the planar pairwise symmetric
four-body problem with a mass as the parameter. This reduces the
linear stability analysis to the computation of two eigenvalues of a matrix for each obtained from numerical integration of the
linearized regularized equations along only the first one-eighth of each
regularized periodic orbit. The results are that the family of symmetric
periodic orbits with regularizable simultaneous binary collisions changes its
linear stability type several times as varies over , with linear
instability for close or equal to 0.01, and linear stability for close
or equal to 1.Comment: 13 pages, 1 figur
Michigan\u27s Cooperative Forest Pest Management Program, A Team Approach to Improving Forest Management
A forest management team was organized in the late 1970\u27s by cooperative efforts of Michigan\u27s universities. the Michigan Department of Natural Resources, and the USDA Forest Service.The goals were to devise new technologies, transfer available technology, and service and management alternatives to forest land managers in Michigan. The program throughout has emphasized forest management rather than pest management for prevention and control of pests. Dissemination of pest management information has been of importance and new research results have gone directly to land managers for immediate use. The team participates in forest compartmental reviews and helps prescribe management plans for land parcels, thus providing for preventative pest management. Services and management recommendations are provided mostly through forest pest specialists located in the field. They feed back results and problems to researchers and extension specialists of the team for further input. Preventive management information used by by local managers in recent years has nearly paid the cost of the program. Plans are to broaden the team effort by cooperating with organizations and in adjacent states through a computer network system and by other means
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