9,432 research outputs found
Measuring the Regional Economic Response to Hurricane Katrina
Naturkatastrophe; Sturm; Makroökonomischer Einfluss; USA
Expert system-based mineral mapping using AVIRIS
Integrated analysis of imaging spectrometer data and field spectral measurements were used in conjunction with conventional geologic field mapping to characterize bedrock and surficial geology at the northern end of Death Valley, California and Nevada. A knowledge-based expert system was used to automatically produce image maps from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data showing the principal surface mineralogy. The imaging spectrometer data show the spatial distribution of spectrally distinct minerals occurring both as primary rock-forming minerals and as alteration and weathering products. Field spectral measurements were used to verify the mineral maps and field mapping was used to extend the remote sensing results. Geographically referenced image-maps produced from these data form new base maps from which to develop improved understanding of the processes of deposition and erosion affecting the present land surface. The 'northern Grapevine Mountains' (NGM) study area was reported on in numerous papers. This area is an unnamed northwestward extension of the range. Most of the research here has concentrated on mapping of Jurassic-age plutons and associated hydrothermal alteration, however, the nature and scope of these studies is much broader, pertaining to the geologic history and development of the entire Death Valley region. AVIRIS data for the NGM site were obtained during May 1989. Additional AVIRIS data were acquired during September 1989 as part of the Geologic Remote Sensing Field Experiment (GRSFE). The area covered by these data overlaps slightly with the May 1989 data. Three and one-half AVIRIS scenes total were analyzed
Vaccination against Actinobacillus pleuropneumoniae as an alternative strategy to antimicrobial use in Danish pig herds
In this study the objective was to determine whether use of vaccination against Actinobacillus pleuropneumoniae (APP) had an effect on the antimicrobial consumption in finisher pigs, when compared to herds without vaccination. Based on observational data, we found that the change in antimicrobial consumption after vaccination was initiated was significant associated with the baseline antimicrobial use before vaccination. The decrease in antimicrobial used was more pronounced in vaccinated herds (N=101) when compared to herds without vaccination (N=320), indicating an effect of vaccination against APP on the antimicrobial consumption level
Ab-initio shell model with a core
We construct effective 2- and 3-body Hamiltonians for the p-shell by
performing 12\hbar\Omega ab initio no-core shell model (NCSM) calculations for
A=6 and 7 nuclei and explicitly projecting the many-body Hamiltonians onto the
0\hbar\Omega space. We then separate these effective Hamiltonians into 0-, 1-
and 2-body contributions (also 3-body for A=7) and analyze the systematic
behavior of these different parts as a function of the mass number A and size
of the NCSM basis space. The role of effective 3- and higher-body interactions
for A>6 is investigated and discussed
Morphogen Transport in Epithelia
We present a general theoretical framework to discuss mechanisms of morphogen
transport and gradient formation in a cell layer. Trafficking events on the
cellular scale lead to transport on larger scales. We discuss in particular the
case of transcytosis where morphogens undergo repeated rounds of
internalization into cells and recycling. Based on a description on the
cellular scale, we derive effective nonlinear transport equations in one and
two dimensions which are valid on larger scales. We derive analytic expressions
for the concentration dependence of the effective diffusion coefficient and the
effective degradation rate. We discuss the effects of a directional bias on
morphogen transport and those of the coupling of the morphogen and receptor
kinetics. Furthermore, we discuss general properties of cellular transport
processes such as the robustness of gradients and relate our results to recent
experiments on the morphogen Decapentaplegic (Dpp) that acts in the fruit fly
Drosophila
Requirements for contractility in disordered cytoskeletal bundles
Actomyosin contractility is essential for biological force generation, and is
well understood in highly organized structures such as striated muscle.
Additionally, actomyosin bundles devoid of this organization are known to
contract both in vivo and in vitro, which cannot be described by standard
muscle models. To narrow down the search for possible contraction mechanisms in
these systems, we investigate their microscopic symmetries. We show that
contractile behavior requires non-identical motors that generate large enough
forces to probe the nonlinear elastic behavior of F-actin. This suggests a role
for filament buckling in the contraction of these bundles, consistent with
recent experimental results on reconstituted actomyosin bundles.Comment: 10 pages, 6 figures; text shortene
Satisfying the Einstein-Podolsky-Rosen criterion with massive particles
In 1935, Einstein, Podolsky and Rosen (EPR) questioned the completeness of
quantum mechanics by devising a quantum state of two massive particles with
maximally correlated space and momentum coordinates. The EPR criterion
qualifies such continuous-variable entangled states, where a measurement of one
subsystem seemingly allows for a prediction of the second subsystem beyond the
Heisenberg uncertainty relation. Up to now, continuous-variable EPR
correlations have only been created with photons, while the demonstration of
such strongly correlated states with massive particles is still outstanding.
Here, we report on the creation of an EPR-correlated two-mode squeezed state in
an ultracold atomic ensemble. The state shows an EPR entanglement parameter of
0.18(3), which is 2.4 standard deviations below the threshold 1/4 of the EPR
criterion. We also present a full tomographic reconstruction of the underlying
many-particle quantum state. The state presents a resource for tests of quantum
nonlocality and a wide variety of applications in the field of
continuous-variable quantum information and metrology.Comment: 8 pages, 7 figure
Effective operators from exact many-body renormalization
We construct effective two-body Hamiltonians and E2 operators for the p-shell
by performing ab initio no-core shell model (NCSM) calculations
for A=5 and A=6 nuclei and explicitly projecting the many-body Hamiltonians and
E2 operator onto the space. We then separate the effective E2
operator into one-body and two-body contributions employing the two-body
valence cluster approximation. We analyze the convergence of proton and neutron
valence one-body contributions with increasing model space size and explore the
role of valence two-body contributions. We show that the constructed effective
E2 operator can be parametrized in terms of one-body effective charges giving a
good estimate of the NCSM result for heavier p-shell nuclei.Comment: 9 pages, 8 figure
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