41,077 research outputs found
Designing marine fishery reserves using passive acoustic telemetry
Marine Fishery Reserves (MFRs) are being adopted, in part, as a strategy to replenish depleted fish stocks and serve as a source for recruits to adjacent fisheries. By necessity, their design must consider the biological parameters of the species under consideration to ensure that the spawning stock is conserved while simultaneously providing propagules for dispersal. We describe how acoustic telemetry can be employed to design effective MFRs by elucidating important life-history parameters of the species under consideration, including home range, and ecological preferences, including habitat utilization. We then designed a reserve based on these parameters using
data from two acoustic telemetry studies that examined two closely-linked subpopulations of queen conch (Strombus
gigas) at Conch Reef in the Florida Keys. The union of the home ranges of the individual conch (aggregation home range:
AgHR) within each subpopulation was used to construct a shape delineating the area within which a conch would be located with a high probability. Together with habitat utilization information acquired during both the spawning and non-spawning seasons, as well as landscape features
(i.e., corridors), we designed a 66.5 ha MFR to conserve the conch population. Consideration was also given for further expansion of the population into suitable habitats
Crises in the thrift industry and the cost of mortgage credit
Savings and loan associations ; Mortgages ; Interest rates
Quantum Monte Carlo study of dilute neutron matter at finite temperatures
We report results of fully non-perturbative, Path Integral Monte Carlo (PIMC)
calculations for dilute neutron matter. The neutron-neutron interaction in the
s channel is parameterized by the scattering length and the effective range. We
calculate the energy and the chemical potential as a function of temperature at
the density \dens=0.003\fm^{-3}. The critical temperature \Tc for the
superfluid-normal phase transition is estimated from the finite size scaling of
the condensate fraction. At low temperatures we extract the spectral weight
function from the imaginary time propagator using the methods of
maximum entropy and singular value decomposition. We determine the
quasiparticle spectrum, which can be accurately parameterized by three
parameters: an effective mass , a mean-field potential , and a gap
. Large value of \Delta/\Tc indicates that the system is not a
BCS-type superfluid at low temperatures.Comment: 4 pages, 3 figure
Fermi arcs and the hidden zeros of the Green's function in the pseudogap state
We investigate the low energy properties of a correlated metal in the
proximity of a Mott insulator within the Hubbard model in two dimensions. We
introduce a new version of the Cellular Dynamical Mean Field Theory using
cumulants as the basic irreducible objects. These are used for re-constructing
the lattice quantities from their cluster counterparts. The zero temperature
one particle Green's function is characterized by the appearance of lines of
zeros, in addition to a Fermi surface which changes topology as a function of
doping. We show that these features are intimately connected to the opening of
a pseudogap in the one particle spectrum and provide a simple picture for the
appearance of Fermi arcs.Comment: revised version; 5 pages, 3 figure
Natural Supergravity Inflation
We show that a single uncharged chiral superfield, canonically coupled to
\mbox{} supergravity with vanishing superpotential, naturally drives
inflation in the early universe for a class of simple Kahler potentials.
Inflation occurs due to the one-loop generation of a Kahler anomaly
proportional to . The coefficient of this term is of the correct
magnitude to describe all aspects of an inflationary cosmology, including
sufficient amplitude perturbations and reheating. Higher order terms
proportional to for are naturally suppressed relative to the
term and, hence, do not destabilize the theory.Comment: 13 pages, CERN-TH.6685/92, UPR-0526
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