4,165 research outputs found
A review of studies mapping (or cross walking) from non-preference based measures of health to generic preference-based measures
This paper presents a systematic review of current practice in mapping between nonpreference based measures and generic preference-based measures. It reviews the studies identified by a systematic search of the published literature and the grey literature. This review seeks to address the feasibility and overall validity of this approach, the circumstances when it should be considered and to bring together any lessons for future mapping studies
A review of studies mapping (or cross walking) from non-preference based measures of health to generic preference-based measures
The use of algorithms to predict surface seawater dimethyl sulphide concentrations in the SE Pacific, a region of steep gradients in primary productivity, biomass and mixed layer depth
Dimethyl sulphide (DMS) is an important precursor of cloud condensation nuclei (CCN), particularly in the remote marine atmosphere. The SE Pacific is consistently covered with a persistent stratocumulus layer that increases the albedo over this large area. It is not certain whether the source of CCN to these clouds is natural and oceanic or anthropogenic and terrestrial. This unknown currently limits our ability to reliably model either the cloud behaviour or the oceanic heat budget of the region. In order to better constrain the marine source of CCN, it is necessary to have an improved understanding of the sea-air flux of DMS. Of the factors that govern the magnitude of this flux, the greatest unknown is the surface seawater DMS concentration. In the study area, there is a paucity of such data, although previous measurements suggest that the concentration can be substantially variable. In order to overcome such data scarcity, a number of climatologies and algorithms have been devised in the last decade to predict seawater DMS. Here we test some of these in the SE Pacific by comparing predictions with measurements of surface seawater made during the Vamos Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in October and November of 2008. We conclude that none of the existing algorithms reproduce local variability in seawater DMS in this region very well. From these findings, we recommend the best algorithm choice for the SE Pacific and suggest lines of investigation for future work
An analysis of the XOR dynamic problem generator based on the dynamical system
This is the post-print version of the article - Copyright @ 2010 Springer-VerlagIn this paper, we use the exact model (or dynamical system approach) to describe the standard evolutionary algorithm (EA) as a discrete dynamical system for dynamic optimization problems (DOPs). Based on this dynamical system model, we analyse the properties of the XOR DOP Generator, which has been widely used by researchers to create DOPs from any binary encoded problem. DOPs generated by this generator are described as DOPs with permutation, where the fitness vector is changed according to a permutation matrix. Some properties of DOPs with permutation are analyzed, which allows explaining some behaviors observed in experimental results. The analysis of the properties of problems created by the XOR DOP Generator is important to understand the results obtained in experiments with this generator and to analyze the similarity of such problems to real world DOPs.This work was supported by Brazil FAPESP under Grant 04/04289-6 and by UK EPSRC under Grant EP/E060722/2
Rigorous results on superconducting ground states for attractive extended Hubbard models
We show that the exact ground state for a class of extended Hubbard models
including bond-charge, exchange, and pair-hopping terms, is the Yang
"eta-paired" state for any non-vanishing value of the pair-hopping amplitude,
at least when the on-site Coulomb interaction is attractive enough and the
remaining physical parameters satisfy a single constraint. The ground state is
thus rigorously superconducting. Our result holds on a bipartite lattice in any
dimension, at any band filling, and for arbitrary electron hopping.Comment: 12 page
The expression and function of glutamate aspartate transporters in Bergmann glia are decreased in neuronal nitric oxide synthase-knockout mice during postnatal development
Bergmann glia (BG) predominantly use glutamate/aspartate transporters (GLAST) for glutamate uptake in the cerebellum. Recently, nitric oxide (NO) treatment has been shown to upregulate GLAST function and increase glutamate uptake in vitro. We previously discovered that neuronal nitric oxide synthase knockout (nNOSâ/â) mice displayed structural and functional neuronal abnormalities in the cerebellum during development, in addition to previously reported motor deficits. Although these developmental deficits have been identified in the nNOSâ/â cerebellum, it is unknown whether BG morphology and GLAST expression are also affected in the absence of nNOS in vivo. This study is the first to characterize BG morphology and GLAST expression during development in nNOSâ/â mice using immunohistochemistry and western blotting across postnatal development. Results showed that BG in nNOSâ/â mice exhibited abnormal morphology and decreased GLAST expression compared with wildtype (WT) mice across postnatal development. Treating ex vivo WT cerebellar slices with the NOS inhibitor L-NAME decreased GLAST expression while treating nNOSâ/â slices with the slow-release NO-donor NOC-18 increased GLAST expression when compared with their respective controls. In addition, treating primary BG isolated from WT mice with the selective nNOS inhibitor 7N decreased the membrane expression of GLAST and influx of Ca2+/Na+, while treating nNOSâ/â BG with SNAP increased the membrane expression of GLAST and Ca2+/Na+ influx. Moreover, the effects of SNAP on GLAST expression and Ca2+/Na+ influx in nNOSâ/â BG were significantly reduced by a PKG inhibitor. Together, these results reveal a novel role for nNOS/NO signaling in BG development, regulated by a PKG-mediated mechanism
Estimating a preference-based single index from the Asthma Quality of Life Questionnaire (AQLQ)
This paper presents a study to estimate a preference-based single index from the Asthma Quality of Life Questionnaire (AQLQ). Based on the AQL-5D which is a health classification system directly derived from AQLQ, 98 health states were valued by a sample of 307 members of the UK general population. Models were estimated to predict all possible 3125 health states defined by the AQL-5D and compared using a set of criteria. The mean model of main effects was recommended of preferable prediction ability and logically consistent and significant coefficients for levels of dimensions. However, there are concerns over condition-specific valuation issues, such as presenting asthma information to general public and the choice of condition specific full health as the upper anchor for TTO valuation
Thermodynamic properties and thermal correlation lengths of a Hubbard model with bond-charge interaction
We investigate the thermodynamics of a one-dimensional Hubbard model with
bond-charge interaction X using the transfer matrix renormalization group
method (TMRG). Numerical results for various quantities like spin and charge
susceptibilities, particle densities, specific heat and thermal correlation
lengths are presented and discussed. We compare our data also to results for
the exactly solvable case X/t=1 as well as to bosonisation results for weak
coupling X/t << 1, which shows excellent agreement. We confirm the existence of
a Tomonaga-Luttinger and a Luther-Emery liquid phase, in agreement with
previous studies at zero temperature. Thermal singlet-pair correlation lengths
are shown to dominate density and spin correlations for finite temperatures in
certain parameter regimes.Comment: 13 pages, revte
-pairing as a mechanism of superconductivity in models of strongly correlated electrons
We consider extended versions of the Hubbard model which contain additional
interactions between nearest neighbours. In this letter we show that a large
class of these models has a superconducting ground state in arbitrary
dimensions. In some special cases we are able to find the complete phase
diagram. The superconducting phase exist even for moderate repulsive values of
the Hubbard interaction .Comment: 9 pages, RevTex, ITP-SB-94-18, 1 PS figure appende
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