29,649 research outputs found
Anomalous enhancement of a penguin hadronic matrix element in B->K eta'
We estimate the density matrix element for the pi^0, eta and eta' production
from the vacuum in the large-N_c limit. As a consequence, we find that the QCD
axial anomaly leads to highly non-trivial corrections to the usual flavour
SU(3) relations between B^0-> K^0 pi^0, B^0-> K^0 eta and B^0-> K^0 eta' decay
amplitudes. These corrections may explain why the B-> K eta' branching ratio is
about six times larger than the B-> K pi one.Comment: 5 pages, 1 figur
Shifts in hexapod diversification and what Haldane could have said
Data on species richness and taxon age are assembled for the extant hexapod orders (insects and their six-legged relatives). Coupled with estimates of phylogenetic relatedness, and simple statistical null models, these data are used to locate where, on the hexapod tree, significant changes in the rate of cladogenesis (speciation-minus-extinction rate) have occurred. Significant differences are found between many successive pairs of sister taxa near the base of the hexapod tree, all of which are attributable to a shift in diversification rate after the origin of the Neoptera (insects with wing flexion) and before the origin of the Holometabola (insects with complete metamorphosis). No other shifts are identifiable amongst supraordinal taxa. Whilst the Coleoptera have probably diversified faster than either of their putative sister lineages, they do not stand out relative to other closely related clades. These results suggest that any Creator had a fondness for a much more inclusive clade than the Coleoptera, definitely as large as the Eumetabola (Holometabola plus bugs and their relatives), and possibly as large as the entire Neoptera. Simultaneous, hence probable causative events are discussed, of which the origin of wing flexion has been the focus of much attention
Structuring Exotic Options Contracts on Water to Improve the Efficiency of Resource Allocation in the Water Spot Market
With the current drought in South-Eastern Australia highlighting the scarcity and value of inland Australia’s water resources, focus turns to how these resources can be allocated more efficiently. The first major step was taken almost a decade ago with the separation of land and water property rights allowing openly traded water markets. This study assesses the potential economic benefits that options contracts bring to the water market in the Murray Valley water market. Exotic call options are estimated using both Black-Scholes and skewness-and-kurtosis-amended Black-Scholes financial option pricing methods that are based on three years of data on water prices. While the presence of options would result in significant economic benefits in the more efficient trade of water on the open market for lower-value crops, there were mixed results from the attempt to price such options.options, skewness-and-kurtosis-amended Black-Scholes model, water, Environmental Economics and Policy, Financial Economics, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,
Interface design in the process industries
Every operator runs his plant in accord with his own mental model of the process. In this sense, one characteristic of an ideal man-machine interface is that it be in harmony with that model. With this theme in mind, the paper first reviews the functions of the process operator and compares them with human operators involved in control situations previously studied outside the industrial environment (pilots, air traffic controllers, helmsmen, etc.). A brief history of the operator interface in the process industry and the traditional methodology employed in its design is then presented. Finally, a much more fundamental approach utilizing a model definition of the human operator's behavior is presented
Cardiovascular consequences of cortisol excess
Cushing's syndrome is a consequence of primary or, more commonly, secondary oversecretion of cortisol. Cardiovascular disease is the major cause of morbidity and mortality in Cushing's syndrome, and excess risk remains even in effectively treated patients. The cardiovascular consequences of cortisol excess are protean and include, inter alia, elevation of blood pressure, truncal obesity, hyperinsulinemia, hyperglycemia, insulin resistance, and dyslipidemia. This review analyses the relationship of cortisol excess, both locally and at tissue level, to these cardiovascular risk factors, and to putative mechanisms for hypertension. Previous studies have examined correlations between cortisol, blood pressure, and other parameters in the general population and in Cushing's syndrome. This review also details changes induced by short-term cortisol administration in normotensive healthy men
Composite Geometric Phase for Multipartite Entangled States
When an entangled state evolves under local unitaries, the entanglement in
the state remains fixed. Here we show the dynamical phase acquired by an
entangled state in such a scenario can always be understood as the sum of the
dynamical phases of its subsystems. In contrast, the equivalent statement for
the geometric phase is not generally true unless the state is separable. For an
entangled state an additional term is present, the mutual geometric phase, that
measures the change the additional correlations present in the entangled state
make to the geometry of the state space. For qubit states we find this
change can be explained solely by classical correlations for states with a
Schmidt decomposition and solely by quantum correlations for W states.Comment: 4 pages, 1 figure, improved presentation, results and conclusions
unchanged from v1. Accepted for publication in PR
New Zealand Guidelines for cyanobacteria in recreational fresh waters: Interim Guidelines
This document is divided into four main sections, plus 14 appendices.
Section 1. Introduction provides an overview of the purpose and status of the document as well as advice on who should use it.
Section 2. Framework provides a background to the overall guidelines approach, recommendations on agency roles and responsibilities, and information on the condition of use of this document.
Section 3. Guidelines describes the recommended three-tier monitoring and action sequence for planktonic and benthic cyanobacteria.
Section 4. Sampling provides advice on sampling planktonic and benthic cyanobacteria.
The appendices give further background information and include templates for data collection and reporting, including:
• background information on known cyanotoxins and their distribution in New Zealand
• information on the derivation of guideline values
• photographs of typical bloom events
• a list of biovolumes for common New Zealand cyanobacteria
• templates for field assessments
• suggested media releases and warning sign templates.
A glossary provides definitions for abbreviations and terms used in these guidelines
Effect of wetting layers on the strain and electronic structure of InAs self-assembled quantum dots
The effect of wetting layers on the strain and electronic structure of InAs
self-assembled quantum dots grown on GaAs is investigated with an atomistic
valence-force-field model and an empirical tight-binding model. By comparing a
dot with and without a wetting layer, we find that the inclusion of the wetting
layer weakens the strain inside the dot by only 1% relative change, while it
reduces the energy gap between a confined electron and hole level by as much as
10%. The small change in the strain distribution indicates that strain relaxes
only little through the thin wetting layer. The large reduction of the energy
gap is attributed to the increase of the confining-potential width rather than
the change of the potential height. First-order perturbation calculations or,
alternatively, the addition of an InAs disk below the quantum dot confirm this
conclusion. The effect of the wetting layer on the wave function is
qualitatively different for the weakly confined electron state and the strongly
confined hole state. The electron wave function shifts from the buffer to the
wetting layer, while the hole shifts from the dot to the wetting layer.Comment: 14 pages, 3 figures, and 3 table
A CLEAN-based Method for Deconvolving Interstellar Pulse Broadening from Radio Pulses
Multipath propagation in the interstellar medium distorts radio pulses, an
effect predominant for distant pulsars observed at low frequencies. Typically,
broadened pulses are analyzed to determine the amount of propagation-induced
pulse broadening, but with little interest in determining the undistorted pulse
shapes. In this paper we develop and apply a method that recovers both the
intrinsic pulse shape and the pulse broadening function that describes the
scattering of an impulse. The method resembles the CLEAN algorithm used in
synthesis imaging applications, although we search for the best pulse
broadening function, and perform a true deconvolution to recover intrinsic
pulse structre. As figures of merit to optimize the deconvolution, we use the
positivity and symmetry of the deconvolved result along with the mean square
residual and the number of points below a given threshold. Our method makes no
prior assumptions about the intrinsic pulse shape and can be used for a range
of scattering functions for the interstellar medium. It can therefore be
applied to a wider variety of measured pulse shapes and degrees of scattering
than the previous approaches. We apply the technique to both simulated data and
data from Arecibo observations.Comment: 9 pages, 6 figures, Accepted for publication in the Astrophysical
Journa
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