293 research outputs found
Astigmatic correction: A clinical comparison of two types of hydrophilic toric lenses
Two brands of soft toric lenses utilizing similar designs were studied. Each lens type was compared as to (1) its success in correcting the refractive astigmatism, (2) accuracy in the manufacture of the parameters ordered and time required for the delivery of\u27 those orders, and ( 3) the appropriateness of the lens when ordered according to the fitting guide\u27s instructions. At first glance, the Hydro-Marc lens appeared to be better suited to most patients\u27 needs when considering the range of parameters available. However, due to problems encountered in delivery time, reliability in the fabrication of the lens, and variability in fit between ordered lenses and those used in diagnostic fitting, the chances for achieving successful :fits do not appear good at this time. Given that the patient approximated those parameters available, the Hydrocurve II toric lens was found to have a high level of success
Dark Matter Search Using Chandra Observations of Willman 1, and a Spectral Feature Consistent with a Decay Line of a 5 keV Sterile Neutrino
We report the results of a search for an emission line from radiatively
decaying dark matter in the Chandra X-ray Observatory spectrum of the
ultra-faint dwarf spheroidal galaxy Willman 1. 99% confidence line flux upper
limits over the 0.4-7 keV Chandra bandpass are derived and mapped to an allowed
region in the sterile neutrino mass-mixing angle plane that is consistent with
recent constraints from Suzaku X-ray Observatory and Chandra observations of
the Ursa Minor and Draco dwarf spheroidals. A significant excess to the
continuum, detected by fitting the particle-background-subtracted source
spectrum, indicates the presence of a narrow emission feature with energy 2.51
+/- 0.07 (0.11) keV and flux [3.53 +/- 1.95 (2.77)] X 10^(-6) photons/cm^2/s at
68% (90%) confidence. Interpreting this as an emission line from sterile
neutrino radiative decay, we derive the corresponding allowed range of sterile
neutrino mass and mixing angle using two approaches. The first assumes that
dark matter is solely composed of sterile neutrinos, and the second relaxes
that requirement. The feature is consistent with the sterile neutrino mass of
5.0 +/- 0.2 keV and a mixing angle in a narrow range for which neutrino
oscillations can produce all of the dark matter and for which sterile neutrino
emission from the cooling neutron stars can explain pulsar kicks, thus
bolstering both the statistical and physical significance of our measurement.Comment: 34 pages, including 20 figures; accepted for publication in ApJ;
substantially expanded discussion session, results unchange
Impact of modulation on CMB B-mode polarization experiments
We investigate the impact of both slow and fast polarization modulation
strategies on the science return of upcoming ground-based experiments aimed at
measuring the B-mode polarization of the CMB. Using simulations of the Clover
experiment, we compare the ability of modulated and un-modulated observations
to recover the signature of gravitational waves in the polarized CMB sky in the
presence of a number of anticipated systematic effects. The general
expectations that fast modulation is helpful in mitigating low-frequency
detector noise, and that the additional redundancy in the projection of the
instrument's polarization sensitivity directions onto the sky when modulating
reduces the impact of instrumental polarization, are borne out by our
simulations. Neither low-frequency polarized atmospheric fluctuations nor
systematic errors in the polarization sensitivity directions are mitigated by
modulation. Additionally, we find no significant reduction in the effect of
pointing errors by modulation. For a Clover-like experiment, pointing jitter
should be negligible but any systematic mis-calibration of the polarization
coordinate reference system results in significant E-B mixing on all angular
scales and will require careful control. We also stress the importance of
combining data from multiple detectors in order to remove the effects of
common-mode systematics (such as 1/f atmospheric noise) on the measured
polarization signal. Finally we compare the performance of our simulated
experiment with the predicted performance from a Fisher analysis. We find good
agreement between the Fisher predictions and the simulations except for the
very largest scales where the power spectrum estimator we have used introduces
additional variance to the B-mode signal recovered from our simulations.Comment: Replaced with version accepted by MNRAS. Analysis of half-wave plate
systematic (differential transmittance) adde
Comment on Higgs Inflation and Naturalness
We rebut the recent claim (arXiv:0912.5463) that Einstein-frame scattering in
the Higgs inflation model is unitary above the cut-off energy Lambda ~ Mp/xi.
We show explicitly how unitarity problems arise in both the Einstein and Jordan
frames of the theory. In a covariant gauge they arise from non-minimal Higgs
self-couplings, which cannot be removed by field redefinitions because the
target space is not flat. In unitary gauge, where there is only a single scalar
which can be redefined to achieve canonical kinetic terms, the unitarity
problems arise through non-minimal Higgs-gauge couplings.Comment: 5 pages, 1 figure V3: Journal Versio
A theoretical framework for combining techniques that probe the link between galaxies and dark matter
We develop a theoretical framework that combines measurements of
galaxy-galaxy lensing, galaxy clustering, and the galaxy stellar mass function
in a self-consistent manner. While considerable effort has been invested in
exploring each of these probes individually, attempts to combine them are still
in their infancy despite the potential of such combinations to elucidate the
galaxy-dark matter connection, to constrain cosmological parameters, and to
test the nature of gravity. In this paper, we focus on a theoretical model that
describes the galaxy-dark matter connection based on standard halo occupation
distribution techniques. Several key modifications enable us to extract
additional parameters that determine the stellar-to-halo mass relation and to
simultaneously fit data from multiple probes while allowing for independent
binning schemes for each probe. In a companion paper, we demonstrate that the
model presented here provides an excellent fit to galaxy-galaxy lensing, galaxy
clustering, and stellar mass functions measured in the COSMOS survey from z=0.2
to z=1.0. We construct mock catalogs from numerical simulations to investigate
the effects of sample variance and covariance on each of the three probes.
Finally, we analyze and discuss how trends in each of the three observables
impact the derived parameters of the model. In particular, we investigate the
various features of the observed galaxy stellar mass function (low-mass slope,
plateau, knee, and high-mass cut-off) and show how each feature is related to
the underlying relationship between stellar and halo mass. We demonstrate that
the observed plateau feature in the stellar mass function at Mstellar~2x10^10
Msun is due to the transition that occurs in the stellar-to-halo mass relation
at Mhalo ~ 10^12 Msun from a low-mass power-law regime to a sub-exponential
function at higher stellar mass.Comment: 21 pages. Accepted to Ap
Weak Lensing of the CMB: Cumulants of the Probability Distribution Function
We discuss the real-space moments of temperature anisotropies in the cosmic
microwave background (CMB) due to weak gravitational lensing by intervening
large-scale structure. We show that if the probability distribution function of
primordial temperature anisotropies is Gaussian, then it remains unchanged
after gravitational lensing. With finite resolution, however, non-zero
higher-order cumulants are generated both by lensing autocorrelations and by
cross-correlations between the lensing potential and secondary anisotropies in
the CMB such as the Sunayev-Zel'dovich (SZ) effect. Skewness is produced by
these lensing-SZ correlations, while kurtosis receives contributions from both
lensing alone and lensing-SZ correlations. We show that if the projected
lensing potential is Gaussian, all cumulants of higher-order than the kurtosis
vanish. While recent results raise the possibility of detection of the skewness
in upcoming data, the kurtosis will likely remain undetected.Comment: 11 pages, 4 figures, submitted to PR
Influenza-A Viruses in Ducks in Northwestern Minnesota: Fine Scale Spatial and Temporal Variation in Prevalence and Subtype Diversity
Waterfowl from northwestern Minnesota were sampled by cloacal swabbing for Avian Influenza Virus (AIV) from July – October in 2007 and 2008. AIV was detected in 222 (9.1%) of 2,441 ducks in 2007 and in 438 (17.9%) of 2,452 ducks in 2008. Prevalence of AIV peaked in late summer. We detected 27 AIV subtypes during 2007 and 31 during 2008. Ten hemagglutinin (HA) subtypes were detected each year (i.e., H1, 3–8, and 10–12 during 2007; H1-8, 10 and 11 during 2008). All neuraminidase (NA) subtypes were detected during each year of the study. Subtype diversity varied between years and increased with prevalence into September. Predominant subtypes during 2007 (comprising ≥5% of subtype diversity) included H1N1, H3N6, H3N8, H4N6, H7N3, H10N7, and H11N9. Predominant subtypes during 2008 included H3N6, H3N8, H4N6, H4N8, H6N1, and H10N7. Additionally, within each HA subtype, the same predominant HA/NA subtype combinations were detected each year and included H1N1, H3N8, H4N6, H5N2, H6N1, H7N3, H8N4, H10N7, and H11N9. The H2N3 and H12N5 viruses also predominated within the H2 and H12 subtypes, respectively, but only were detected during a single year (H2 and H12 viruses were not detected during 2007 and 2008, respectively). Mallards were the predominant species sampled (63.7% of the total), and 531 AIV were isolated from this species (80.5% of the total isolates). Mallard data collected during both years adequately described the observed temporal and spatial prevalence from the total sample and also adequately represented subtype diversity. Juvenile mallards also were adequate in describing the temporal and spatial prevalence of AIV as well as subtype diversity
Working with bipolar disorder during the covid-19 pandemic: Both crisis and opportunity
© 2020, WikiJournal User Group. All rights reserved. Beyond public health and economic costs, the COVID-19 pandemic adds strain, disrupts daily routines, and com-plicates mental health and medical service delivery for those with mental health and medical conditions. Bipolar disorder can increase vulnerability to infection; it can also enhance stress, complicate treatment, and heighten interpersonal stigma. Yet there are successes when people proactively improve social connections, prioritize self-care, and learn to use mobile and telehealth effectively
Spatial variation in the fine-structure constant -- new results from VLT/UVES
(abridged) We present a new analysis of a large sample of quasar
absorption-line spectra obtained using UVES (the Ultraviolet and Visual Echelle
Spectrograph) on the VLT (Very Large Telescope) in Chile. In the VLT sample
(154 absorbers), we find evidence that alpha increases with increasing
cosmological distance from Earth. However, as previously shown, the Keck sample
(141 absorbers) provided evidence for a smaller alpha in the distant absorption
clouds. Upon combining the samples an apparent variation of alpha across the
sky emerges which is well represented by an angular dipole model pointing in
the direction RA=(17.3 +/- 1.0) hr, dec. = (-61 +/- 10) deg, with amplitude
(0.97 +0.22/-0.20) x 10^(-5). The dipole model is required at the 4.1 sigma
statistical significance level over a simple monopole model where alpha is the
same across the sky (but possibly different to the current laboratory value).
The data sets reveal a number of remarkable consistencies: various data cuts
are consistent and there is consistency in the overlap region of the Keck and
VLT samples. Assuming a dipole-only (i.e. no-monopole) model whose amplitude
grows proportionally with `lookback-time distance' (r=ct, where t is the
lookback time), the amplitude is (1.1 +/- 0.2) x 10^(-6) GLyr^(-1) and the
model is significant at the 4.2 sigma confidence level over the null model
[Delta alpha]/alpha = 0). We apply robustness checks and demonstrate that the
dipole effect does not originate from a small subset of the absorbers or
spectra. We present an analysis of systematic effects, and are unable to
identify any single systematic effect which can emulate the observed variation
in alpha.Comment: 47 pages, 35 figures. Accepted for publication by Monthly Notices of
the Royal Astronomical Society. Please see
http://astronomy.swin.edu.au/~mmurphy/pub.html for an ASCII version of table
A1 and the full set of Voigt profile fits for appendix
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