2,110 research outputs found
Why Full Open Access Matters
This perspective explains the mechanics of copyright and scholarly publishing and warns authors who support open-access publishing about a new pseudo open-access publishing model in which authors pay but publishers still retain commercial reuse rights
Assessment of the visibility impairment caused by the emissions from the proposed power plant at Boron, California
The current atmospheric conditions and visibility were modeled, and the effect of the power plant effluent was then added to determine its influence upon the prevailing visibility; the actual reduction in visibility being a function of meteorological conditions and observer-plume-target geometry. In the cases investigated, the perceptibility of a target was reduced by a minimum of 10 percent and a maximum of 100 percent. This significant visual impact would occur 40 days per year in the Edwards area with meteorological conditions such as to cause some visual impact 80 days per year
Kinetic decoupling of neutralino dark matter
After neutralinos cease annihilating in the early Universe, they may still
scatter elastically from other particles in the primordial plasma. At some
point in time, however, they will eventually stop scattering. We calculate the
cross sections for neutralino elastic scattering from standard-model particles
to determine the time at which this kinetic decoupling occurs. We show that
kinetic decoupling occurs above a temperature MeV. Thereafter,
neutralinos act as collisionless cold dark matter.Comment: Replaced with revised version, new references adde
Modeling the effect of plume-rise on the transport of carbon monoxide over Africa and its exports with NCAR CAM
International audienceWe investigated the effects of fire-induced plume-rise on the predicted export of carbon monoxide (CO) over Africa during SAFARI 2000 using the NCAR Community Atmosphere Model (CAM) with a CO tracer and plume-rise parameterization scheme. The plume-rise parameterization scheme simulates the consequences of strong buoyancy of hot gases emitted from biomass burning, including both dry and cloud-associated (pyrocumulus) lofting. The scheme was first adapted from a regional model. The current implementation of the plume-rise parameterization scheme into the global model provides an opportunity to examine the effect of plume-rise on long-range transport. The CAM simulation with the plume-rise parameterization scheme shows a substantial improvement of the agreements between the modeled and aircraft-measured vertical distribution of CO over southern Africa biomass burning area. The plume-rise mechanism plays a crucial role in lofting biomass burning pollutants to the middle troposphere. In the presence of deep convection we found that the plume-rise mechanism results in a decrease of CO concentration in the upper troposphere. The plume rise depletes the boundary layer, and thus leaves lower concentrations of CO to be lofted by the deep convection process. The effect of the plume-rise on free troposphere CO concentration is more important for the source area (short-distance transport) than for remote areas (long-distance transport). The plume-rise scheme also increases the CO export fluxes from Africa to the Atlantic and Indian Oceans. These results further confirm and extend previous findings in a regional model study. Effective lofting of large concentration of CO by the plume-rise mechanism also has implication for local air quality forecast in areas affected by other fire-related pollutants
Microscopic calculation of 6Li elastic and transition form factors
Variational Monte Carlo wave functions, obtained from a realistic Hamiltonian
consisting of the Argonne v18 two-nucleon and Urbana-IX three-nucleon
interactions, are used to calculate the 6Li ground-state longitudinal and
transverse form factors as well as transition form factors to the first four
excited states. The charge and current operators include one- and two-body
components, leading terms of which are constructed consistently with the
two-nucleon interaction. The calculated form factors and radiative widths are
in good agreement with available experimental data.Comment: 9 pages, 2 figures, REVTeX, submitted to Physical Review Letters,
with updated introduction and reference
Probing Neutralino Resonance Annihilation via Indirect Detection of Dark Matter
The lightest neutralino of R-parity conserving supersymmetric models serves
as a compelling candidate to account for the presence of cold dark matter in
the universe. In the minimal supergravity (mSUGRA) model, a relic density can
be found in accord with recent WMAP data for large values of the parameter
, where neutralino annihilation in the early universe occurs via the
broad s-channel resonance of the pseudoscalar Higgs boson . We map out rates
for indirect detection of neutralinos via 1. detection of neutrinos arising
from neutralino annihilation in the core of the earth or sun and 2. detection
of gamma rays, antiprotons and positrons arising from neutralino annihilation
in the galactic halo. If indeed -resonance annihilation is the main sink for
neutralinos in the early universe, then signals may occur in the gamma ray,
antiproton and positron channels, while a signal in the neutrino channel would
likely be absent. This is in contrast to the hyperbolic branch/focus point
(HB/FP) region where {\it all} indirect detection signals are likely to occur,
and also in contrast to the stau co-annihilation region, where {\it none} of
the indirect signals are likely to occur.Comment: 12 pages including 4 eps figure
Tax evasion and exchange equity: a reference-dependent approach
The standard portfolio model of tax evasion with a public good produces the perverse conclusion that when taxpayers perceive the public good to be under-/overprovided, an increase in the tax rate increases/decreases evasion. The author treats taxpayers as thinking in terms of gains and losses relative to an endogenous reference level, which reflects perceived exchange equity between the value of taxes paid and the value of public goods supplied. With these alternative behavioral assumptions, the author overturns the aforementioned result in a direction consistent with the empirical evidence. The author also finds a role for relative income in determining individual responses to a change in the marginal rate of tax
Transplant Co-ordination Services in Europe 1989: A Survey by the EDTA Registry
This report contains EDTA Registry data concerning transplant co-ordination services. It is a summary of the results of a special questionnaire mailed in 1989 to all renal transplant centres known to the EDTA Registry in Europe and Mediterranean countries. The response rate to the questionnaire was 86%. A transplant co-ordination service was available in more than 70% of the centres. The larger the transplant activity of a centre, the greater was the likelihood of a co-ordinator service being available. The educational background of the transplant co-ordinator was most commonly that of nurse. More than 70% of the centres had one or two transplant co-ordirtators. A service shared by several centres was fairly common in the United Kingdom and France. The most important duties and activities appeared to be the organisation of transportation of donor teams and organs, giving feedback to the donor hospital's staff, and providing information to the public regarding organ donatio
Neutral pion photoproduction off 3H and 3He in chiral perturbation theory
We calculate electromagnetic neutral pion production off three-nucleon bound
states (3H, 3He) at threshold to leading one-loop order in the framework of
chiral nuclear effective field theory. In addition, we analyze the dependence
of the nuclear S-wave amplitude E_{0+} on the elementary neutron amplitude
E_{0+}^{pi0 n} which in the case of 3He provides a stringent test of the
prediction based on chiral perturbation theory. Uncertainties from higher order
corrections are estimated.Comment: 6 pages, 3 figures, version accepted for publication in Phys. Lett.
B, improved discussion of higher-order corrections, results unchange
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