6,618 research outputs found
The Optical - Infrared Colors of CORALS QSOs: Searching for Dust Reddening Associated With High Redshift Damped Lyman Alpha Systems
The presence of dust in quasar absorbers, such as damped Lyman alpha (DLA)
systems, may cause the background QSO to appear reddened. We investigate the
extent of this potential reddening by comparing the optical-to-infrared (IR)
colors of QSOs with and without intervening absorbers. Our QSO sample is based
on the Complete Optical and Radio Absorption Line System (CORALS) survey of
Ellison et al (2001). We have obtained near-simultaneous B and K band
magnitudes for subset of the CORALS sample and supplemented our observations
with further measurements published in the literature. To account for
redshift-related color changes, the B-K colors are normalized using the Sloan
Digital Sky Survey (SDSS) QSO composite. The mean normalized B-K color of the
DLA sub-sample is +0.12, whereas the mean for the no-DLA sample is -0.10; both
distributions have RMS scatters ~0.5. Neither a student's T-test nor a KS test
indicate that there is any significant difference between the two color
distributions. Based on simulations which redden the colors of QSOs with
intervening DLAs, we determine a reddening limit which corresponds to E(B-V) <
0.04 (SMC-like extinction) at 99% confidence (3 sigma), assuming that E(B-V) is
the same for all DLAs. Finally, we do not find any general correlation between
absorber properties (such as [Fe/Zn] or neutral hydrogen column density) and
B-K color. One of these two QSOs shows evidence for strong associated
absorption from X-ray observations, an alternative explanation for its very red
color. We conclude that the presence of intervening galaxies causes a minimal
reddening of the background QSO.Comment: Accepted for publication in A
Quantum Spin Lenses in Atomic Arrays
We propose and discuss `quantum spin lenses', where quantum states of
delocalized spin excitations in an atomic medium are `focused' in space in a
coherent quantum process down to (essentially) single atoms. These can be
employed to create controlled interactions in a quantum light-matter interface,
where photonic qubits stored in an atomic ensemble are mapped to a quantum
register represented by single atoms. We propose Hamiltonians for quantum spin
lenses as inhomogeneous spin models on lattices, which can be realized with
Rydberg atoms in 1D, 2D and 3D, and with strings of trapped ions. We discuss
both linear and non-linear quantum spin lenses: in a non-linear lens, repulsive
spin-spin interactions lead to focusing dynamics conditional to the number of
spin excitations. This allows the mapping of quantum superpositions of
delocalized spin excitations to superpositions of spatial spin patterns, which
can be addressed by light fields and manipulated. Finally, we propose
multifocal quantum spin lenses as a way to generate and distribute entanglement
between distant atoms in an atomic lattice array.Comment: 13 pages, 9 figure
Eating Habits of Professional Firefighters: Comparison With National Guidelines and Impact Healthy Eating Promotion Program.
Firefighters' eating habits may be an additional risk factor for metabolic diseases. We assessed eating habits of firefighters, compared them with national guidelines, and evaluated the impact of a prevention program.
Twenty-eight professional firefighters from a Swiss airport benefited from a healthy-eating program. Food intake, eating behavior, and anthropometric data were collected at baseline and 1-year follow-up using an electronic food record, questionnaires, and bio-impedance.
Participants had unbalanced diets with low-quality food choices associated with low intakes of fibers and micronutrients compared with national guidelines. Intervention did not impact eating habits or anthropometrics data at the group level, but changes were measured in sub-groups. Main reported barriers for healthy eating were lack of motivation, prioritization, or time.
Intensive and culturally tailored prevention interventions targeting nutritional behaviors are needed at the individual, group, and organizational levels
Non-locality of non-Abelian anyons
Topological systems, such as fractional quantum Hall liquids, promise to
successfully combat environmental decoherence while performing quantum
computation. These highly correlated systems can support non-Abelian anyonic
quasiparticles that can encode exotic entangled states. To reveal the non-local
character of these encoded states we demonstrate the violation of suitable Bell
inequalities. We provide an explicit recipe for the preparation, manipulation
and measurement of the desired correlations for a large class of topological
models. This proposal gives an operational measure of non-locality for anyonic
states and it opens up the possibility to violate the Bell inequalities in
quantum Hall liquids or spin lattices.Comment: 7 pages, 3 figure
Comparison of radiative energy flows in observational datasets and climate modeling
This study examines radiative flux distributions and local spread of values from three major observational datasets (CERES, ISCCP, and SRB) and compares them with results from climate modeling (CMIP3). Examinations of the spread and differences also differentiate among contributions from cloudy and clear-sky conditions. The spread among observational datasets is in large part caused by noncloud ancillary data. Average differences of at least 10 W m-2 each for clear-sky downward solar, upward solar, and upward infrared fluxes at the surface demonstrate via spatial difference patterns major differences in assumptions for atmospheric aerosol, solar surface albedo and surface temperature, and/or emittance in observational datasets. At the top of the atmosphere (TOA), observational datasets are less influenced by the ancillary data errors than at the surface. Comparisons of spatial radiative flux distributions at the TOA between observations and climate modeling indicate large deficiencies in the strength and distribution of model-simulated cloud radiative effects. Differences are largest for lower-altitude clouds over low-latitude oceans. Global modeling simulates stronger cloud radiative effects (CRE) by +30 W m-2 over trade wind cumulus regions, yet smaller CRE by about -30 W m-2 over (smaller in area) stratocumulus regions. At the surface, climate modeling simulates on average about 15 W m-2 smaller radiative net flux imbalances, as if climate modeling underestimates latent heat release (and precipitation). Relative to observational datasets, simulated surface net fluxes are particularly lower over oceanic trade wind regions (where global modeling tends to overestimate the radiative impact of clouds). Still, with the uncertainty in noncloud ancillary data, observational data do not establish a reliable reference. © 2016 American Meteorological Society
Multi-model simulations of the impact of international shipping on Atmospheric Chemistry and Climate in 2000 and 2030
The global impact of shipping on atmospheric chemistry and radiative forcing, as well as the associated uncertainties, have been quantified using an ensemble of ten state-of-the-art atmospheric chemistry models and a predefined set of emission data. The analysis is performed for present-day conditions ( year 2000) and for two future ship emission scenarios. In one scenario ship emissions stabilize at 2000 levels; in the other ship emissions increase with a constant annual growth rate of 2.2% up to 2030 ( termed the "Constant Growth Scenario" (CGS)). Most other anthropogenic emissions follow the IPCC ( Intergovernmental Panel on Climate Change) SRES ( Special Report on Emission Scenarios) A2 scenario, while biomass burning and natural emissions remain at year 2000 levels. An intercomparison of the model results with observations over the Northern Hemisphere (25 degrees - 60 degrees N) oceanic regions in the lower troposphere showed that the models are capable to reproduce ozone (O-3) and nitrogen oxides (NOx= NO+ NO2) reasonably well, whereas sulphur dioxide (SO2) in the marine boundary layer is significantly underestimated. The most pronounced changes in annual mean tropospheric NO2 and sulphate columns are simulated over the Baltic and North Seas. Other significant changes occur over the North Atlantic, the Gulf of Mexico and along the main shipping lane from Europe to Asia, across the Red and Arabian Seas. Maximum contributions from shipping to annual mean near-surface O-3 are found over the North Atlantic ( 5 - 6 ppbv in 2000; up to 8 ppbv in 2030). Ship contributions to tropospheric O3 columns over the North Atlantic and Indian Oceans reach 1 DU in 2000 and up to 1.8 DU in 2030. Tropospheric O-3 forcings due to shipping are 9.8 +/- 2.0 mW/m(2) in 2000 and 13.6 +/- 2.3 mW/m(2) in 2030. Whilst increasing O-3, ship NOx simultaneously enhances hydroxyl radicals over the remote ocean, reducing the global methane lifetime by 0.13 yr in 2000, and by up to 0.17 yr in 2030, introducing a negative radiative forcing. The models show future increases in NOx and O-3 burden which scale almost linearly with increases in NOx emission totals. Increasing emissions from shipping would significantly counteract the benefits derived from reducing SO2 emissions from all other anthropogenic sources under the A2 scenario over the continents, for example in Europe. Globally, shipping contributes 3% to increases in O-3 burden between 2000 and 2030, and 4.5% to increases in sulphate under A2/CGS. However, if future ground based emissions follow a more stringent scenario, the relative importance of ship emissions will increase. Inter-model differences in the simulated O-3 contributions from ships are significantly smaller than estimated uncertainties stemming from the ship emission inventory, mainly the ship emission totals, the distribution of the emissions over the globe, and the neglect of ship plume dispersion
Measurement of the Temperature Dependence of the Casimir-Polder Force
We report on the first measurement of a temperature dependence of the
Casimir-Polder force. This measurement was obtained by positioning a nearly
pure 87-Rb Bose-Einstein condensate a few microns from a dielectric substrate
and exciting its dipole oscillation. Changes in the collective oscillation
frequency of the magnetically trapped atoms result from spatial variations in
the surface-atom force. In our experiment, the dielectric substrate is heated
up to 605 K, while the surrounding environment is kept near room temperature
(310 K). The effect of the Casimir-Polder force is measured to be nearly 3
times larger for a 605 K substrate than for a room-temperature substrate,
showing a clear temperature dependence in agreement with theory.Comment: 4 pages, 4 figures, published in Physical Review Letter
Nuclear energy density optimization: Large deformations
A new Skyrme-like energy density suitable for studies of strongly elongated
nuclei has been determined in the framework of the Hartree-Fock-Bogoliubov
theory using the recently developed model-based, derivative-free optimization
algorithm POUNDerS. A sensitivity analysis at the optimal solution has revealed
the importance of states at large deformations in driving the parameterization
of the functional. The good agreement with experimental data on masses and
separation energies, achieved with the previous parameterization UNEDF0, is
largely preserved. In addition, the new energy density UNEDF1 gives a much
improved description of the fission barriers in 240Pu and neighboring nuclei.Comment: 16 pages, 11 figures, accepted for publication in Phys. Rev.
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