1,219 research outputs found
Environmental Studies at Newton Lake, Illinois: Tasks 4, 5, and 7
ID: 8658; issued March 1, 1991INHS Technical Report prepared for Marathon Oil Compan
The rho meson decay constant using a tadpole-improved action
The rho meson decay constant and the associated renormalization factor are
computed in the quenched approximation on coarse lattices using a
tadpole-improved action which is corrected at the classical level to O(a^2).
The improvement is displayed by comparing to Wilson action calculations.Comment: Talk presented at LATTICE96(improvement), 3 pages, LaTeX, uses epsf
and espcrc2.st
BasinSim 1.0 A Windows-Based Watershed Modeling Package
BasinSim 1.0 for Windows is the product of a NOAA Coastal Zone Management grant (through the Virginia Coastal Resources Management Program) awarded to Drs. Ting Dai, R. L. Wetzel, I. C. Anderson, and L. W. Haas at the Virginia Institute of Marine Science, College of William and Mary in 1998. Additional support has been provided for the development and testing of this package and production of this userâs guide by grants from Virginiaâs Chesapeake Bay Local Assistance Department (CBLAD). BasinSim 1.0 is a desktop simulation system that predicts sediment and nutrient loads for small to mid-sized watersheds. The simulation system is based on the Generalized Watershed Loading Functions (GWLF), a tested watershed model developed by Dr. Douglas Haith and his colleagues at Cornell University, New York (Haith and Shoemaker 1987, Haith et al. 1992). BasinSim 1.0 integrates an easy-to-use graphic Windows interface, extensive databases (land uses, population, soils, water discharge, water quality, climate, point nutrient sources, etc.), and the GWLF model (with modifications) into a single software package. It was designed to enable resource managers to visualize watershed characteristics, retrieve historic data (at the county and sub-watershed levels), manipulate land use patterns, and simulate nutrient (N, P, and organic C) and sediment loadings under various scenarios. The software will assist resource managers in making sound management decisions using the latest technology, information, and scientific knowledge. The system can also be used to educate local organizations and the general public about linkages between basinwide resource management and water quality
The Birth and Growth of Neutralino Haloes
We use the Extended-Press-Schechter (EPS) formalism to study halo assembly
histories in a standard CDM cosmology. A large ensemble of Monte Carlo
random walks provides the {\it entire} halo membership histories of a
representative set of dark matter particles, which we assume to be neutralinos.
The first generation halos of most particles do not have a mass similar to the
free-streaming cut-off of the neutralino power spectrum, nor do they
form at high redshift. Median values are to and
to 8 depending on the form of the collapse barrier assumed in the
EPS model. For almost a third of all particles the first generation halo has
. At redshifts beyond 20, most neutralinos are not yet part
of any halo but are still diffuse. These numbers apply with little modification
to the neutralinos which are today part of halos similar to that of the Milky
Way. Up to 10% of the particles in such halos were never part of a smaller
object; the typical particle has undergone "accretion events' where
the halo it was part of falls into a more massive object. Available N-body
simulations agree well with the EPS predictions for an "ellipsoidal" collapse
barrier, so these may provide a reliable extension of simulation results to
smaller scales. The late formation times and large masses of the first
generation halos of most neutralinos imply that they will be disrupted with
high efficiency during halo assembly.Comment: 7 pages, 7 figure
Recent progress in computing four-loop massive correlators
We report about recent progress in computing four-loop massive correlators.
The expansion of these correlators in the external momentum leads to vacuum
integrals. The calculation of these vacuum integrals can be used to determine
Taylor expansion coefficients of the vacuum polarization function and
decoupling functions in perturbative Quantum chromodynamics. New results at
four-loop order for the lowest Taylor expansion coefficient of the vacuum
polarization function and for the decoupling relation are presented.Comment: 4 pages, talk given at the 12th International Conference on Quantum
Chromodynamics, Montpellier, 4-8th July 200
Recommended from our members
Global climatology of surface water temperatures of large lakes by remote sensing
Lake surface water temperatures (LSWTs) of 246 globally distributed large lakes were derived from Along-Track Scanning Radiometers (ATSR) for the period 1991â2011. The climatological cycles of mean LSWT derived from these data quantify on a global scale the responses of large lakes' surface temperatures to the annual cycle of forcing by solar radiation and the ambient meteorological conditions. LSWT cycles reflect the twice annual peak in net solar radiation for lakes between 1°S to 12°N. For lakes without a lake-mean seasonal ice cover, LSWT extremes exceed air temperatures by 0.5â1.7 °C for maximum and 0.7â1.9 °C for minimum temperature. The summer maximum LSWTs of lakes from 25°S to 35°N show a linear decrease with increasing altitude; â3.76 ± 0.17 °C kmâ1 (inline image = 0.95), marginally lower than the corresponding air temperature decrease with altitude â4.15 ± 0.24 °C kmâ1 (inline image = 0.95). Lake altitude of tropical lakes account for 0.78â0.83 (inline image) of the variation in the March to June LSWTâair temperature differences, with differences decreasing by 1.9 °C as the altitude increases from 500 to 1800 m above sea level (a.s.l.) We define an âopen water phaseâ as the length of time the lake-mean LSWT remains above 4 °C. There is a strong global correlation between the start and end of the lake-mean open water phase and the spring and fall 0 °C air temperature transition days, (inline image = 0.74 and 0.80, respectively), allowing for a good estimation of timing and length of the open water phase of lakes without LSWT observations. Lake depth, lake altitude and distance from coast further explain some of the inter-lake variation in the start and end of the open water phase
QCD Decoupling at Four Loops
We present the matching condition for the strong coupling contant alpha_s at
a heavy quark threshold to four loops in the modified minimal subtraction
scheme. Our results lead to further decrease of the theoretical uncertainty of
the evolution of the strong coupling constant through heavy quark thresholds.
Using a low energy theorem we furthermore derive the effective coupling of the
Higgs boson to gluons (induced by a virtual heavy quark) in four- and
(partially) through five-loop approximation.Comment: 21 pages, 2 figures, the complete paper is also available via the www
at http://www-ttp.physik.uni-karlsruhe.de/Preprints
The bearable lightness of being
How are philosophical questions about what kinds of things there are to be understood and how are they to be answered? This paper defends broadly Fregean answers to these questions. Ontological categories-such as object, property, and relation-are explained in terms of a prior logical categorization of expressions, as singular terms, predicates of varying degree and level, etc. Questions about what kinds of object, property, etc., there are are, on this approach, reduce to questions about truth and logical form: for example, the question whether there are numbers is the question whether there are true atomic statements in which expressions function as singular terms which, if they have reference at all, stand for numbers, and the question whether there are properties of a given type is a question about whether there are meaningful predicates of an appropriate degree and level. This approach is defended against the objection that it must be wrong because makes what there depend on us or our language. Some problems confronting the Fregean approach-including Frege's notorious paradox of the concept horse-are addressed. It is argued that the approach results in a modest and sober deflationary understanding of ontological commitments
CFHT Legacy Ultraviolet Extension (CLUE): Witnessing Galaxy Transformations up to 7 Mpc from Rich Cluster Cores
Using the optical data from the Wide component of the CFHT Legacy Survey, and
new ultraviolet data from GALEX, we study the colours and specific star
formation rates (SSFR) of ~100 galaxy clusters at 0.16<z<0.36, over areas
extending out to radii of r~7Mpc. We use a multicolour, statistical background
subtraction method to study the galaxy population at this radius; thus our
results pertain to those galaxies which constitute an excess over the average
field density. We find that the average SSFR, and its distribution, of the
star-forming galaxies (with SFR>0.7 M_sun/yr at z~0.2 and SFR>1.2 M_sun/yr at
z~0.3) have no measurable dependence on the cluster-centric radius, and are
consistent with the field values. However, the fraction of galaxies with SFR
above these thresholds, and the fraction of optically blue galaxies, are lower
for the overdense galaxy population in the cluster outskirts compared with the
average field value, at all stellar masses M*>10^{9.8} M_sun and at all radii
out to at least 7Mpc. Most interestingly, the fraction of blue galaxies that
are forming stars at a rate below our UV detection limit is much higher in all
radial bins around our cluster sample, compared with the general field value.
This is most noticeable for massive galaxies M*>10^{10.7} M_sun; while almost
all blue field galaxies of this mass have detectable star formation, this is
true for less than 20% of the blue cluster galaxies, even at 7Mpc from the
cluster centre. Our results support a scenario where galaxies are pre-processed
in locally overdense regions, in a way that reduces their SFR below our UV
detection limit, but not to zero.Comment: MNRAS accepte
Disentangling galaxy environment and host halo mass
[Abridged] The properties of observed galaxies and dark matter haloes in
simulations depend on their environment. The term environment has been used to
describe a wide variety of measures that may or may not correlate with each
other. Popular measures of environment include the distance to the N'th nearest
neighbour, the number density of objects within some distance, or the mass of
the host dark matter halo. We use results from the Millennium simulation and a
semi-analytic model for galaxy formation to quantify the relations between
environment and halo mass. We show that the environmental parameters used in
the observational literature are in effect measures of halo mass, even if they
are measured for a fixed stellar mass. The strongest correlation between
environment and halo mass arises when the number of objects is counted out to a
distance of 1.5-2 times the virial radius of the host halo and when the
galaxies/haloes are required to be relatively bright/massive. For observational
studies the virial radius is not easily determined, but the number of
neighbours out to 1-2 Mpc/h gives a similarly strong correlation. For the
distance to the N'th nearest neighbour the correlation with halo mass is nearly
as strong provided N>2. We demonstrate that this environmental parameter
becomes insensitive to halo mass if it is constructed from dimensionless
quantities. This can be achieved by scaling the minimum luminosity/mass of
neighbours to that of the object in question and by dividing the distance to a
length scale associated with either the neighbour or the galaxy under
consideration. We show how such a halo mass independent environmental parameter
can be defined for observational and numerical studies. The results presented
here will help future studies to disentangle the effects of halo mass and
external environment on the properties of galaxies and dark matter haloes.Comment: 15 pages, 9 figures, 2 tables. Accepted by MNRA
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