3,294 research outputs found
Spectrophotometry with a transmission grating for detecting faint occultations
High-precision spectrophotometry is highly desirable in detecting and
characterizing close-in extrasolar planets to learn about their makeup and
temperature. For such a goal, a modest-size telescope with a simple
low-resolution spectroscopic instrument is potentially as good or better than a
complex general purpose spectrograph since calibration and removal of
systematic errors is expected to dominate. We use a transmission grating placed
in front of an imaging CCD camera on Steward Observatory's Kuiper 1.5 m
telescope to provide a high signal-to-noise, low dispersion visible spectrum of
the star HD 209458. We attempt to detect the reflected light signal from the
extra-solar planet HD 209458b by differencing the signal just before and after
secondary occultation. We present a simple data reduction method and explore
the limits of ground based low-dispersion spectrophotometry with a diffraction
grating. Reflected light detection levels of 0.1% are achievable for
5000-7000A, too coarse for useful limits on ESPs but potentially useful for
determining spectra of short-period binary systems with large (Delta m_vis=6)
brightness ratios. Limits on the precison are set by variations in atmospheric
seeing in the low-resolution spectrum. Calibration of this effect can be
carried out by measurement of atmospheric parameters from the observations
themselves, which may allow the precision to be limited by the noise due to
photon statistics and atmospheric scintillation effects.Comment: 34 pages and 17 figures. Accepted for publication in PAS
Pension supervision : understanding international practice and country context
This paper proposes an approach to classifying and measuring the primary elements of private pension supervision, and undertakes an evaluation using a representative set of countries. The analysis considers how supervision methods and style relate to the basic design of pension systems, and the broader environment in which they operate. Supervisory systems are shown to include six main elements, with considerable variation among systems in the scope, and intensity of activities within each element. The analysis concludes that there are discernible relationships between supervisory methods, and the context in which they are applied. The level of economic development, depth of capital markets, underlying legal framework presence of mandates, and number of funds supervised are found to be associated with depth, and intensity of supervision activities. These findings support the principle that the organization, and management of private pension supervision is significantly derived from the context, and environment in which these systems operate.
Quantum Corrections to Thermopower and Conductivity in Graphene
The quantum corrections to the conductivity and the thermopower in monolayer
graphene are studied. We use the recursive Green's function method to calculate
numerically the conductivity and the thermopower of graphene. We then analyze
these weak localization corrections by fitting with the analytical theory as
function of the impurity parameters and the gate potential. As a result of the
quantum corrections to the thermopower, we find large magnetothermopower which
is shown to provide a very sensitive measure of the size and strength of the
impurities. We compare these analytical and numerical results with existing
experimental measurements of magnetoconductance of single layer graphene and
find that the average size and strength of the impurities in these samples can
thereby be determined. We suggest favorable parameter ranges for future
measurements of the magnetothermopower
The new pensions in Kazakhstan : challenges in making the transition
In June of 1997 Kazakhstan embarked on a dramatic reform of its pension system, replacing the inherited pay as you go regime with one based entirely on fully funded individual accounts. This paper provides projections of the effects of this reform on income replacement rates and considers some possible adjustments to the system design, including those enacted in early 2005, that could address the projected outcomes of the reform. The initial reform which did not include any minimum pension guarantee is projected to result in a significant reduction in the individual income replacement rates derived from the pension system, especially for women. When the reform was mature and the old system fully phased out, women are projected to have received pensions at level of less than 15 percent of their pre-retirement earnings. Various potential adjustments to the reform, including the recent introduction of a citizens pension or"demogrant", are found to have the capacity to significantly raise these income replacement rates. The fiscal costs of alternatives are found to vary considerably due significantly to the degree to which they would target expenditures to lower income groups. The analysis of the original reform design and possible adjustments provides some useful lessons about the design of individual account systems in transition economies.Pensions&Retirement Systems,State Owned Enterprise Reform,Economic Theory&Research,Gender and Law,Youth and Governance
From non-symmetric particle systems to non-linear PDEs on fractals
We present new results and challenges in obtaining hydrodynamic limits for
non-symmetric (weakly asymmetric) particle systems (exclusion processes on
pre-fractal graphs) converging to a non-linear heat equation. We discuss a
joint density-current law of large numbers and a corresponding large deviations
principle.Comment: v2: 10 pages, 1 figure. To appear in the proceedings for the 2016
conference "Stochastic Partial Differential Equations & Related Fields" in
honor of Michael R\"ockner's 60th birthday, Bielefel
Dynamical Masses in Luminous Infrared Galaxies
We have studied the dynamics and masses of a sample of ten nearby luminous
and ultraluminous infrared galaxies (LIRGS and ULIRGs), using 2.3 micron CO
absorption line spectroscopy and near-infrared H- and Ks-band imaging. By
combining velocity dispersions derived from the spectroscopy, disk
scale-lengths obtained from the imaging, and a set of likely model density
profiles, we calculate dynamical masses for each LIRG. For the majority of the
sample, it is difficult to reconcile our mass estimates with the large amounts
of gas derived from millimeter observations and from a standard conversion
between CO emission and H_2 mass. Our results imply that LIRGs do not have huge
amounts of molecular gas (10^10-10^11 Msolar) at their centers, and support
previous indications that the standard conversion of CO to H_2 probably
overestimates the gas masses and cannot be used in these environments. This in
turn suggests much more modest levels of extinction in the near-infrared for
LIRGs than previously predicted (A_V~10-20 versus A_V~100-1000). The lower gas
mass estimates indicated by our observations imply that the star formation
efficiency in these systems is very high and is triggered by cloud-cloud
collisions, shocks, and winds rather than by gravitational instabilities in
circumnuclear gas disks.Comment: 14 pages, 2 figures, accepted to Ap
Attempted reduction of a carbazolyl-diiodoalane
We report details of our attempts to reduce the bulky carbazolyl diiodoalane [R–AlI]. The reducing agents employed include KC, CpCo and the Mg(I) compound [(BDI)Mg]. The use of KC allowed the spectroscopic observation of the alanediyl [R–Al]. With CpCo as the reducing agent, the alanediyl [R–Al] was obtained as a crystalline material in low yield, but paramagnetic impurities remained. When diiodoalane [R–AlI] was treated with [(BDI)Mg], no reduction but a 2 : 1 addition was observed
University of Utah visual, information and technology literacy task force report and recommendations
Repor
- …