21,890 research outputs found
Mojave Applied Ecology Notes Summer 2010
Survey of monitoring and management for conservation of rare plants, Roadside restoration techniques in Joshua Tree NP, and an update on renewable energy developments in the Southwestern desert
Intrinsic-Density Functionals
The Hohenberg-Kohn theorem and Kohn-Sham procedure are extended to
functionals of the localized intrinsic density of a self-bound system such as a
nucleus. After defining the intrinsic-density functional, we modify the usual
Kohn-Sham procedure slightly to evaluate the mean-field approximation to the
functional, and carefully describe the construction of the leading corrections
for a system of fermions in one dimension with a spin-degeneracy equal to the
number of particles N. Despite the fact that the corrections are complicated
and nonlocal, we are able to construct a local Skyrme-like intrinsic-density
functional that, while different from the exact functional, shares with it a
minimum value equal to the exact ground-state energy at the exact ground-state
intrinsic density, to next-to-leading order in 1/N. We briefly discuss
implications for real Skyrme functionals.Comment: 15 page
Quasielastic neutrino scattering from oxygen and the atmospheric neutrino problem
We examine several phenomena beyond the scope of Fermi-gas models that affect
the quasielastic scattering (from oxygen) of neutrinos in the 0.1 -- 3.0 GeV
range. These include Coulomb interactions of outgoing protons and leptons, a
realistic finite-volume mean field, and the residual nucleon-nucleon
interaction. None of these effects are accurately represented in the Monte
Carlo simulations used to predict event rates due to and neutrinos
from cosmic-ray collisions in the atmosphere. We nevertheless conclude that the
neglected physics cannot account for the anomalous to ratio observed
at Kamiokande and IMB, and is unlikely to change absolute event rates by more
than 10--15\%. We briefly mention other phenomena, still to be investigated in
detail, that may produce larger changes.Comment: In Revtex version 2. 14 pages, 3 figures (available on request from
J. Engel, tel. 302-831-4354, [email protected]
Model-independent assessment of current direct searches for spin-dependent dark matter
I evaluate the current results of spin-dependent weakly interacting massive
particle (WIMP) searches within a model-independent framework, showing the most
restrictive limits to date derive from the combination of xenon and sodium
iodide experiments. The extension of this analysis to the case of positive
signal experiments is elaborated.Comment: 4 pages, 4 figures, revised and accepted for publication on Phys.
Rev. Let
Local correlation functional for electrons in two dimensions
We derive a local approximation for the correlation energy in two-dimensional
electronic systems. In the derivation we follow the scheme originally developed
by Colle and Salvetti for three dimensions, and consider a Gaussian
approximation for the pair density. Then, we introduce an ad-hoc modification
which better accounts for both the long-range correlation, and the
kinetic-energy contribution to the correlation energy. The resulting functional
is local, and depends parametrically on the number of electrons in the system.
We apply this functional to the homogeneous electron gas and to a set of
two-dimensional quantum dots covering a wide range of electron densities and
thus various amounts of correlation. In all test cases we find an excellent
agreement between our results and the exact correlation energies. Our
correlation functional has a form that is simple and straightforward to
implement, but broadly outperforms the commonly used local-density
approximation
Uniparental Disomy and Genome Imprinting: an Overview
The following paper is concerned with potential changes in the normal epigenetic process in a diploid individual, when a chromosome pair or segment is inherited from one parent only, instead of the expected biparental contribution. This aberrant mode of transmission arises from the high rate of gamete aneuploidy in humans. It has received the name uniparental disomy (UPD), and has emerged as an important factor in the new field of nontraditional inheritance, depicted in Table 1. The following definitions may foster a better understanding of this discussion. UPD is the inheritance of both copies of a chromosome [or chromosomal segment(s)] from a single parent, instead of the normal biparental transmission of the pair. In isodisomy, the two uniparental copies are identical, being derived from the same parental chromosome. In heterodisomy, the two uniparental chromosomes are different, being derived from the homologues of a pai
Correlations between hidden units in multilayer neural networks and replica symmetry breaking
We consider feed-forward neural networks with one hidden layer, tree
architecture and a fixed hidden-to-output Boolean function. Focusing on the
saturation limit of the storage problem the influence of replica symmetry
breaking on the distribution of local fields at the hidden units is
investigated. These field distributions determine the probability for finding a
specific activation pattern of the hidden units as well as the corresponding
correlation coefficients and therefore quantify the division of labor among the
hidden units. We find that although modifying the storage capacity and the
distribution of local fields markedly replica symmetry breaking has only a
minor effect on the correlation coefficients. Detailed numerical results are
provided for the PARITY, COMMITTEE and AND machines with K=3 hidden units and
nonoverlapping receptive fields.Comment: 9 pages, 3 figures, RevTex, accepted for publication in Phys. Rev.
Endogenous Exchange Rate Pass-through when Nominal Prices are Set in Advance
This paper develops a model of endogenous exchange rate pass through within an open economy macroeconomic framework, where both pass-through and the exchange rate are simultaneously determined, and interact with one another. Pass-through is endogenous because firms choose the currency in which they set their export prices. There is a unique equilibrium rate of pass-through under the condition that exchange rate volatility rises as the degree of pass-through falls. We show that the relationship between exchange rate volatility and economic structure may be substantially affected by the presence of endogenous pass-through. Our key results show that pass-through is related to the relative stability of monetary policy. Countries with relatively low volatility of money growth will have relatively low rates of exchange rate pass-through, while countries with relatively high volatility of money growth will have relatively high pass-through rates.
Endogenous Exchange Rate Pass-through when Nominal Prices are Set in Advance
This paper develops a model of endogenous exchange rate pass-through within an open economy macroeconomic framework, where both passthrough and the exchange rate are simultaneously determined, and interact with one another. Pass-through is endogenous because firms choose the currency in which they set their export prices. There is a unique equilibrium rate of pass-through under the condition that exchange rate volatility rises as the degree of pass-through falls. We show that the relationship between exchange rate volatility and economic structure may be substantially affected by the presence of endogenous pass-through. Our key results show that pass-through is related to the relative stability of monetary policy. Countries with relatively low volatility of money growth will have relatively low rates of exchange rate pass-through, while countries with relatively high volatility of money growth will have relatively high pass-through rates.
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