2,674 research outputs found
Investigation of effects of varying model inputs on mercury deposition estimates in the Southwest US
The Community Multiscale Air Quality (CMAQ) model version 4.7.1 was used to simulate mercury wet and dry deposition for a domain covering the continental United States (US). The simulations used MM5-derived meteorological input fields and the US Environmental Protection Agency (EPA) Clear Air Mercury Rule (CAMR) emissions inventory. Using sensitivity simulations with different boundary conditions and tracer simulations, this investigation focuses on the contributions of boundary concentrations to deposited mercury in the Southwest (SW) US. Concentrations of oxidized mercury species along the boundaries of the domain, in particular the upper layers of the domain, can make significant contributions to the simulated wet and dry deposition of mercury in the SW US. In order to better understand the contributions of boundary conditions to deposition, inert tracer simulations were conducted to quantify the relative amount of an atmospheric constituent transported across the boundaries of the domain at various altitudes and to quantify the amount that reaches and potentially deposits to the land surface in the SW US. Simulations using alternate sets of boundary concentrations, including estimates from global models (Goddard Earth Observing System-Chem (GEOS-Chem) and the Global/Regional Atmospheric Heavy Metals (GRAHM) model), and alternate meteorological input fields (for different years) are analyzed in this paper. CMAQ dry deposition in the SW US is sensitive to differences in the atmospheric dynamics and atmospheric mercury chemistry parameterizations between the global models used for boundary conditions
Hybrid Reactions to Phytotoxic Effects of The Corn Herbicide, Eradicane Extra
Although corn hybrids are primarily evaluated only for yield performance in the Kentucky Hybrid Corn Performance Test, the 1984 test (Poneleit and Evans, 1985) provided a unique opportunity to evaluate hybrid reactions to an unusual hybrid-herbicide interacting Of seven non-virus test locations, four were treated with Eradicane Extra or Eradicane for weed control. At the Princeton location Eradicane Extra, at 8 pints/acre, was used for johnsongrass rhizome suppression and seedling control. In late July, a routine check revealed that numerous plants had unusual appearances that were similar to abnormalities reported earlier as caused by Eptam and Eradicane (Poneleit et aI, 1975). Subsequent observations confirmed the severity of damage at the Princeton test site and reports of similar hybrid reactions from farmer fields prompted the collection of apparent herbicide damage data from the replicated Princeton test. The other performance test sites where Eradicane Extra or Eradicane was applied did not show significant plant abnormalities. Apparently the appearance of phytotoxic effects owing to Eradicane Extra are sporadic and strongly influenced by specific interaction of environmental factors. It was postulated that this injury occurrence in 1984 was the result of excessive rainfall four to six weeks after planting. Dichlormid (safener) is very water soluble and could have been leached away from the corn roots, and thus not available to protect the corn from EPTC
Constraints on the Charged Higgs Sector from the Tevatron Collider Data on Top Quark Decay
The top quark data in the lepton plus channel offers a viable probe
for the charged Higgs boson signal. We analyse the recent Tevatron collider
data in this channel to obtain a significant limit on the mass in the
large region.Comment: 8 pages, LaTeX file; 2 figures included (PS files
The Velocity Function of Galaxies
We present a galaxy circular velocity function, Psi(log v), derived from
existing luminosity functions and luminosity-velocity relations. Such a
velocity function is desirable for several reasons. First, it enables an
objective comparison of luminosity functions obtained in different bands and
for different galaxy morphologies, with a statistical correction for dust
extinction. In addition, the velocity function simplifies comparison of
observations with predictions from high-resolution cosmological N-body
simulations.
We derive velocity functions from five different data sets and find rough
agreement among them, but about a factor of 2 variation in amplitude. These
velocity functions are then compared with N-body simulations of a LCDM model
(corrected for baryonic infall) in order to demonstrate both the utility and
current limitations of this approach. The number density of dark matter halos
and the slope of the velocity function near v_*, the circular velocity
corresponding to an ~L_* spiral galaxy, are found to be comparable to that of
observed galaxies. The primary sources of uncertainty in construction of
Psi(log v) from observations and N-body simulations are discussed and
explanations are suggected to account for these discrepancies.Comment: Latex. 28 pages, 4 figures. Accepted by Ap
Attentive Learning of Sequential Handwriting Movements: A Neural Network Model
Defense Advanced research Projects Agency and the Office of Naval Research (N00014-95-1-0409, N00014-92-J-1309); National Science Foundation (IRI-97-20333); National Institutes of Health (I-R29-DC02952-01)
Halo Substructure and the Power Spectrum
In this proceeding, we present the results of a semi-analytic study of CDM
substructure as a function of the primordial power spectrum. We apply our
method to several tilted models in the LCDM framework with n=0.85-1.1,
sigma_8=0.65-1.2 when COBE normalized. We also study a more extreme, warm dark
matter-like spectrum that is sharply truncated below a scale of 10^10 h^-1
Msun. We show that the mass fraction of halo substructure is not a strong
function of spectral slope, so it likely will be difficult to constrain tilt
using flux ratios of gravitationally lensed quasars. On the positive side, all
of our CDM-type models yield projected mass fractions in good agreement with
strong lensing estimates: f \sim 1.5% at M \sim 10^8 Msun. The truncated model
produces a significantly smaller fraction, f \lsim 0.3%, suggesting that warm
dark matter-like spectra may be distinguished from CDM spectra using lensing.
We also discuss the issue of dwarf satellite abundances, with emphasis on the
cosmological dependence of the map between the observed central velocity
dispersion of Milky Way satellites and the maximum circular velocities of their
host halos. In agreement with earlier work, we find that standard LCDM
over-predicts the estimated count of Milky Way satellites at fixed Vmax by an
order of magnitude, but tilted models do better because subhalos are less
concentrated. Interestingly, under the assumption that dwarfs have isotropic
velocity dispersion tensors, models with significantly tilted spectra (n \lsim
0.85, sigma_8 \lsim 0.7) may under-predict the number of large Milky Way
satellites with Vmax \gsim 40 km/s.Comment: 5 pages, 2 figures. Poster contribution to the 13th Annual
Astrophysics Conference in Maryland, The Emergence of Cosmic Structur
Adding four-dimensional data assimilation by analysis nudging to the Model for Prediction Across Scales â Atmosphere (version 4.0)
The Model for Prediction Across Scales â Atmosphere (MPAS-A) has been
modified to allow four-dimensional data assimilation (FDDA) by the nudging of
temperature, humidity, and wind toward target values predefined on the MPAS-A
computational mesh. The addition of nudging allows MPAS-A to be used as a
global-scale meteorological driver for retrospective air quality modeling.
The technique of analysis nudging developed for the Penn State/National
Center for Atmospheric Research (NCAR) Mesoscale Model, and later applied in
the Weather Research and Forecasting model, is implemented in MPAS-A with
adaptations for its polygonal Voronoi mesh. Reference fields generated from
1° âĂâ 1° National Centers for Environmental
Prediction (NCEP) FNL (Final) Operational Global Analysis data were used to
constrain MPAS-A simulations on a 92â25 km variable-resolution mesh with
refinement centered over the contiguous United States. Test simulations were
conducted for January and July 2013 with and without FDDA, and compared to
reference fields and near-surface meteorological observations. The results
demonstrate that MPAS-A with analysis nudging has high fidelity to the
reference data while still maintaining conservation of mass as in the
unmodified model. The results also show that application of FDDA constrains
model errors relative to 2 m temperature, 2 m water vapor mixing ratio, and
10 m wind speed such that they continue to be at or below the magnitudes
found at the start of each test period.</p
Rescaling multipartite entanglement measures for mixed states
A relevant problem regarding entanglement measures is the following: Given an
arbitrary mixed state, how does a measure for multipartite entanglement change
if general local operations are applied to the state? This question is
nontrivial as the normalization of the states has to be taken into account.
Here we answer it for pure-state entanglement measures which are invariant
under determinant 1 local operations and homogeneous in the state coefficients,
and their convex-roof extension which quantifies mixed-state entanglement. Our
analysis allows to enlarge the set of mixed states for which these important
measures can be calculated exactly. In particular, our results hint at a
distinguished role of entanglement measures which have homogeneous degree 2 in
the state coefficients.Comment: Published version plus one important reference (Ref. [39]
Type IIn supernovae at z ~ 2 from archival data
Supernovae have been confirmed to redshift z ~ 1.7 for type Ia (thermonuclear
detonation of a white dwarf) and to z ~ 0.7 for type II (collapse of the core
of the star). The subclass type IIn supernovae are luminous core-collapse
explosions of massive stars and, unlike other types, are very bright in the
ultraviolet, which should enable them to be found optically at redshifts z ~ 2
and higher. In addition, the interaction of the ejecta with circumstellar
material creates strong, long-lived emission lines that allow spectroscopic
confirmation of many events of this type at z ~ 2 for 3 - 5 years after
explosion. Here we report three spectroscopically confirmed type IIn
supernovae, at redshifts z = 0.808, 2.013 and 2.357, detected in archival data
using a method designed to exploit these properties at z ~ 2. Type IIn
supernovae directly probe the formation of massive stars at high redshift. The
number found to date is consistent with the expectations of a locally measured
stellar initial mass function, but not with an evolving initial mass function
proposed to explain independent observations at low and high redshift.Comment: 8 pages, 2 figures, includes supplementary informatio
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