3,313 research outputs found
Soft-bottom benthic assemblages and levels of contaminants in sediments and biota at Gray's Reef National Marine Sanctuary and nearby shelf waters off the coast of Georgia (2000 and 2001)
A series of studies was initiated to assess the condition of benthic macroinfauna and chemical contaminant levels in sediments and biota of the Grayâs Reef National Marine Sanctuary (GRNMS) and nearby shelf waters off the coast of Georgia. Four key objectives of the research are (1) to
document existing environmental conditions within the sanctuary in order to provide a quantitative benchmark for tracking any future changes due to either natural or human disturbances; (2) to examine broader cross-shelf spatial patterns in benthic fauna and sediment contaminant
concentrations and to identify potential controlling factors associated with the observed patterns; (3) to assess any between-year temporal variability in benthic fauna; and (4) to evaluate the importance of benthic fauna as prey for higher trophic levels. Such questions are being addressed to help fulfill long-term science and management goals of the GRNMS. However, it is anticipated that the
information will be of additional value in broadening our understanding of the surrounding South Atlantic Bight (SAB) ecosystem and in bringing the knowledge to bear on related resourcemanagement issues of the region.
We have begun to address the first three of these objectives with data from samples collected in spring 2000 at stations within GRNMS, and in spring 2001 at stations within the sanctuary and along three cross-shelf transects extending from the mouths of Sapelo, Doboy, and Altamaha Sounds out to sanctuary depths (about 17-20 m). This report provides a description of baseline conditions within
the sanctuary, based on results of the spring 2000 survey (Section II), and uses data from both 2000 and 2001 to examine overall spatial and temporal patterns in biological and chemical variables within the sanctuary and surrounding inner-shelf environment (Section III). (PDF contains 65 pages
Freeze-Out Time in Ultrarelativistic Heavy Ion Collisions from Coulomb Effects in Transverse Pion Spectra
The influence of the nuclear Coulomb field on transverse spectra of
and measured in reactions at 158 A GeV has been investigated.
Pion trajectories are calculated in the field of an expanding fireball. The
observed enhancement of the ratio at small momenta depends on the
temperature and transverse expansion velocity of the source, the rapidity
distribution of the net positive charge, and mainly the time of the freeze-out.Comment: 11 pages including 2 figure
Numerical solution of the Navier-Stokes equations for arbitrary two-dimensional multi-element airfoils
The development of a numerical simulation of time dependent, turbulent, compressible flow about two dimensional multi-element airfoils of arbitrary shape is described. The basis of this simulation is a technique of automatic numerical generation of coordinate systems fitted to the multiple bodies regardless of their number or shape. Procedures developed whereby the coordinate lines are automatically concentrated in the boundary layer at any Reynolds number are discussed. The compressible turbulent solution involves an algebraic eddy viscosity turbulence model. The laminar version was run for transonic flow at free stream Mach numbers up to 0.9
Direct Emission of multiple strange baryons in ultrarelativistic heavy-ion collisions from the phase boundary
We discuss a model for the space-time evolution of ultrarelativistic
heavy-ion collisions which employs relativistic hydrodynamics within one region
of the forward light-cone, and microscopic transport theory (i.e. UrQMD) in the
complement. Our initial condition consists of a quark-gluon plasma which
expands hydrodynamically and hadronizes. After hadronization the solution
eventually changes from expansion in local equilibrium to free streaming, as
determined selfconsistently by the interaction rates between the hadrons and
the local expansion rate. We show that in such a scenario the inverse slopes of
the -spectra of multiple strange baryons (, ) are practically
unaffected by the purely hadronic stage of the reaction, while the flow of
's and 's increases. Moreover, we find that the rather ``soft''
transverse expansion at RHIC energies (due to a first-order phase transition)
is not washed out by strong rescattering in the hadronic stage. The earlier
kinetic freeze-out as compared to SPS-energies results in similar inverse
slopes (of the -spectra of the hadrons in the final state) at RHIC and SPS
energies.Comment: 4 pages, 3 figures, statistics for Omegas improved, slight revision
of the manuscript (expansion of hadronization volume more emphasized,
pi-Omega scattering is discussed very briefly
The Origin of Transverse Flow at the SPS
We study the transverse expansion in central Pb+Pb collisions at the CERN
SPS. Strong collective motion of hadrons can be created. This flow is mainly
due to meson baryon rescattering. It allows to study the angular distribution
of intermediate mass meson baryon interactions.Comment: submitted to Phys. Lett.
(Anti)Proton and Pion Source Sizes and Phase Space Densities in Heavy Ion Collisions
NA44 has measured mid-rapidity deuteron spectra from AA collisions at
sqrt{s}=18GeV/A at the CERN SPS. Combining these spectra with published proton,
antiproton and antideuteron data allows us to calculate, within a coalescence
framework, proton and antiproton source sizes and phase space densities. These
results are compared to pion source sizes and densities, pA results and to
lower energy (AGS) data. The antiproton source is larger than the proton source
at sqrt{s}=18GeV/A. The phase space densities of pions and protons are not
constant but grow with system size. Both pi+ and proton radii decrease with
transverse mass and increase with sqrt{s}. Pions and protons do not freeze-out
independently. The nature of their interaction changes as sqrt{s}, and the
pion/proton ratio increases.Comment: 4 pages, Latex 2.09, 3 eps figures. Changes for January 2001. The
proton source size is now calculated assuming a more realistic Hulthen,
rather than Gaussian, wavefunction. A new figure shows the effect of this
change which is important for small radii. A second new figure shows the
results of RQMD calculations of the proton source size and phase density.
Because of correlations between position and momentum coalesence does not
show the full proton source size. The paper has been streamlined and
readability improve
A Treatise on Diversity in a Dominant Culture University
The authors examine progress in strengthening the Diversity agenda in a school of education within a private Christian university. This agenda is informed by external academic accrediting organizations and principles of social justice congruent with the historical roots of the university. Special emphasis is placed on the unique challenges of confronting how privilege manifests itself in seemingly homogeneous environments. The ultimate goal of the authors is to promote moving beyond cosmetic compliance with accreditation obligations towards a metabolized second order change reflecting internal paradigm shifts in which social justice is a central motivating factor in oneâs vocation
Quasi-Elastic Scattering Studies of Water Diffusion
Quasi-elastic neutron scattering is a powerful method to study the dynamics of protons in biological systems. The technique has been used both for the study of water diffusion and protein motion. The neutron scattering measurements on water show that the translational and rotational diffusion coefficients in biological systems are reduced from bulk values. We review the measurements on water in frog muscle, cysts of artemia, and phycocyanin. Measurements on dry trypsin and trypsin-D2O solutions over the temperature range 75-300K show that there is proton motion at the one angstrom level even in the dry or frozen state
Two-kaon correlations in central Pb + Pb collisions at 158 A GeV/c
Two-particle interferometry of positive kaons is studied in Pb + Pb
collisions at mean transverse momenta and 0.91 GeV/c. A
three-dimensional analysis was applied to the lower data, while a
two-dimensional analysis was used for the higher data. We find that the
source size parameters are consistent with the scaling curve observed in
pion correlation measurements in the same collisions, and that the duration
time of kaon emission is consistent with zero within the experimental
sensitivity.Comment: 4 pages incl. 1 table and 3 fig's; RevTeX; accepted for publication
in PR
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