511 research outputs found
Angler Response to Success in the California Salmon Sportfishery: Evidence and Management Implications
This paper examines effort responsiveness to success in the California salmon partyboat sport fishery. The management process in this important fishery involves setting target harvest levels for both commercial and sportfishing groups and then using closed seasons, restricted gear, and possession limits to dampen effective effort. An important component of the management process involves forecasting sportfishing effort and its effect on catch in order to advance-plan management actions. For want of better information, simple proportionality rules-of-thumb are used currently and this paper examines the plausibility of these. Some simple models forecasting aggregate angler participation and aggregate partyboat catch on a weekly basis are estimated across several different ports. Our findings suggest that anglers are responsive to recent success in several sports (elasticities up to + .5) and that angler participation affects catch with an elasticity exceeding unity. These results indicate that the simple rules of thumb currently in use could be in substantial error.Environmental Economics and Policy, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,
Evolution of shear-induced melting in dusty plasma
The spatiotemporal development of melting is studied experimentally in a 2D
dusty plasma suspension. Starting with an ordered lattice, and then suddenly
applying localized shear, a pair of counter-propagating flow regions develop. A
transition between two melting stages is observed before a steady state is
reached. Melting spreads with a front that propagates at the transverse sound
speed. Unexpectedly, coherent longitudinal waves are excited in the flow
region.Comment: 5 pages text, 3 figures, in press Physical Review Letters 2010
Grain boundary melting in ice
We describe an optical scattering study of grain boundary premelting in water
ice. Ubiquitous long ranged attractive polarization forces act to suppress
grain boundary melting whereas repulsive forces originating in screened Coulomb
interactions and classical colligative effects enhance it. The liquid enhancing
effects can be manipulated by adding dopant ions to the system. For all
measured grain boundaries this leads to increasing premelted film thickness
with increasing electrolyte concentration. Although we understand that the
interfacial surface charge densities and solute concentrations can
potentially dominate the film thickness, we can not directly measure them
within a given grain boundary. Therefore, as a framework for interpreting the
data we consider two appropriate dependent limits; one is dominated by
the colligative effect and one is dominated by electrostatic interactions.Comment: 6 pages, 5 figure
A direct optical method for the study of grain boundary melting
The structure and evolution of grain boundaries underlies the nature of
polycrystalline materials. Here we describe an experimental apparatus and light
reflection technique for measuring disorder at grain boundaries in optically
clear material, in thermodynamic equilibrium. The approach is demonstrated on
ice bicrystals. Crystallographic orientation is measured for each ice sample.
The type and concentration of impurity in the liquid can be controlled and the
temperature can be continuously recorded and controlled over a range near the
melting point. The general methodology is appropriate for a wide variety of
materials.Comment: 8 pages, 8 figures, updated with minor changes made to published
versio
Metastatic Breast Cancer Presenting as Painless Jaundice
Breast cancer is the most commonly diagnosed cancer in women in the United States. Treatment options are wide-‐ ranging based on a multitude of factors, including extent of disease and receptor positivity. Following treatment, a relapse-‐free interval ≥ 2 years carries a more favorable prognosis.
We present a case involving a female with history of breast cancer and relapse-free interval of 15 years who unfortunately presented with metastatic disease involving the liver, bone, and lymph nodes
A low power photoemission source for electrons on liquid helium
Electrons on the surface of liquid helium are a widely studied system that
may also provide a promising method to implement a quantum computer. One
experimental challenge in these studies is to generate electrons on the helium
surface in a reliable manner without heating the cryo-system. An electron
source relying on photoemission from a zinc film has been previously described
using a high power continuous light source that heated the low temperature
system. This work has been reproduced more compactly by using a low power
pulsed lamp that avoids any heating. About 5e3 electrons are collected on 1
cm^2 of helium surface for every pulse of light. A time-resolved experiment
suggests that electrons are either emitted over or tunnel through the 1eV
barrier formed by the thin superfluid helium film on the zinc surface. No
evidence of trapping or bubble formation is seen.Comment: 9 pages, 3 figures, submitted to J. Low Temp. Phy
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