1,916 research outputs found
Reducing Urban Pollution Exposure from Road Transport(RUPERT)
This paper presents the preliminary results of a two-year study on reducing urban pollution exposure from road transport (RUPERT). The main aim of this project
is to develop a new modelling framework for nitrogen dioxide, carbon monoxide and particulate matter to simulate exposures of different population groups
across a city, and to assess the impact of roadside concentrations on these exposures. This will be achieved by modelling the frequency distribution of
personal exposures (PEFDs) as a function of urban background and roadside concentrations, under different traffic conditions. The modelling approach combines new and existing models relating traffic and air pollution data, with particular emphasis of the impact of congestion, and the probabilistic modelling framework of personal exposure. Modelling of roadside concentrations consists of two main elements, namely the analysis of concentrations patterns at different roadside sites and of the relationship between traffic conditions and added
roadside pollution. Roadside concentrations are predicted using empirically derived relationships; statistical models, novel statistics and artificial neural
networks namely feed forward neural network and radial basis neural network. The exposure modelling is carried out by linking two models: the INDAIR model, which is designed to simulate probabilistically diurnal profiles of air pollutant concentrations in a range of microenvironments, and the EXPAIR model, which is designed to simulate population exposure patterns based on
population time-activity patterns and a library of micro-environmental concentrations derived from the INDAIR model
Cause of death and predictors of mortality in a community-based cohort of people with epilepsy.
OBJECTIVE: The risk of premature mortality is increased in people with epilepsy. The reasons for this and how it may relate to epilepsy etiology remain unclear.
METHODS: The National General Practice Study of Epilepsy is a prospective, community-based cohort that includes 558 people with recurrent unprovoked seizures of whom 34% died during almost 25 years of follow-up. We assessed the underlying and immediate causes of death and their relationship to epilepsy etiology. Psychiatric and somatic comorbidities of epilepsy as predictors of mortality were scrutinized using adjusted Cox proportional hazards models.
RESULTS: The 3 most common underlying causes of death were noncerebral neoplasm, cardiovascular, and cerebrovascular disease, accounting for 59% (111/189) of deaths, while epilepsy-related causes (e.g., sudden unexplained death in epilepsy) accounted for 3% (6/189) of deaths. In 23% (43/189) of individuals, the underlying cause of death was directly related to the epilepsy etiology; this was significantly more likely if death occurred within 2 years of the index seizure (percent ratio 4.28 [95% confidence interval 2.63-6.97]). Specific comorbidities independently associated with increased risk of mortality were neoplasms (primary cerebral and noncerebral neoplasm), certain neurologic diseases, and substance abuse.
CONCLUSIONS: Comorbid diseases are important causes of death, as well as predictors of premature mortality in epilepsy. There is an especially strong relationship between cause of death and epilepsy etiology in the first 2 years after the index seizure. Addressing these issues may help stem the tide of premature mortality in epilepsy
Body Composition Profiling in the UK Biobank Imaging Study
Objective
To investigate the value of imaging-based multivariable body composition profiling by describing its association with coronary heart disease (CHD), type 2 diabetes (T2D), and metabolic health on individual and population levels.
Methods
The first 6,021 participants scanned by UK Biobank were included. Body composition profiles (BCPs) were calculated including abdominal subcutaneous adipose tissue, visceral adipose tissue (VAT), thigh muscle volume, liver fat, and muscle fat infiltration (MFI), determined using magnetic resonance imaging. Associations between BCP and metabolic status were investigated using matching procedures and multivariable statistical modelling.
Results
Matched control analysis showed higher VAT and MFI was associated with CHD and T2D (p<0.001). Higher liver fat was associated with T2D (p<0.001) and lower liver fat with CHD (p<0.05), matching on VAT. Multivariable modelling showed lower VAT and MFI was associated with metabolic health (p<0.001), liver fat was non-significant. Associations remained significant adjusting for sex, age, BMI, alcohol, smoking, and physical activity.
Conclusions
Body composition profiling enabled an intuitive visualization of body composition and showed the complexity of associations between fat distribution and metabolic status, stressing the importance of a multivariable approach. Different diseases were linked to different BCPs, which could not be described by a single fat compartment alone
Representation theory of super Yang-Mills algebras
We study in this article the representation theory of a family of super
algebras, called the \emph{super Yang-Mills algebras}, by exploiting the
Kirillov orbit method \textit{\`a la Dixmier} for nilpotent super Lie algebras.
These super algebras are a generalization of the so-called \emph{Yang-Mills
algebras}, introduced by A. Connes and M. Dubois-Violette in \cite{CD02}, but
in fact they appear as a "background independent" formulation of supersymmetric
gauge theory considered in physics, in a similar way as Yang-Mills algebras do
the same for the usual gauge theory. Our main result states that, under certain
hypotheses, all Clifford-Weyl super algebras \Cliff_{q}(k) \otimes A_{p}(k),
for , or and , appear as a quotient of all super
Yang-Mills algebras, for and . This provides thus a family
of representations of the super Yang-Mills algebras
Superconductor coupled to two Luttinger liquids as an entangler for electron spins
We consider an s-wave superconductor (SC) which is tunnel-coupled to two
spatially separated Luttinger liquid (LL) leads. We demonstrate that such a
setup acts as an entangler, i.e. it creates spin-singlets of two electrons
which are spatially separated, thereby providing a source of electronic
Einstein-Podolsky-Rosen pairs. We show that in the presence of a bias voltage,
which is smaller than the energy gap in the SC, a stationary current of
spin-entangled electrons can flow from the SC to the LL leads due to Andreev
tunneling events. We discuss two competing transport channels for Cooper pairs
to tunnel from the SC into the LL leads. On the one hand, the coherent
tunneling of two electrons into the same LL lead is shown to be suppressed by
strong LL correlations compared to single-electron tunneling into a LL. On the
other hand, the tunneling of two spin-entangled electrons into different leads
is suppressed by the initial spatial separation of the two electrons coming
from the same Cooper pair. We show that the latter suppression depends
crucially on the effective dimensionality of the SC. We identify a regime of
experimental interest in which the separation of two spin-entangled electrons
is favored. We determine the decay of the singlet state of two electrons
injected into different leads caused by the LL correlations. Although the
electron is not a proper quasiparticle of the LL, the spin information can
still be transported via the spin density fluctuations produced by the injected
spin-entangled electrons.Comment: 15 pages, 2 figure
A New Neutrino Cross Section Database
We describe a new web based data resource being developed to provide access
to accurate and validated cross sections of low energy neutrino and
antineutrino interactions. The proposed content of this database are outlined
which cover total and differential cross from inclusive, quasi-elastic and
exclusive pion production processes from charged and neutral current
interactions. Efforts to obtain these data, which come mainly from old bubble
chamber experiments, are described as well as the implementation of an
embryonic web site to make the resource generally accessible.Comment: 6 pages, 3 figures, To appear in the proceedings of the 3rd
International Workshop on Neutrino Nucleus Interactions in the few GeV region
(NuInt04), Gran Sasso, Assergi, Italy, 17-21 Mar 200
Efficient Algorithm on a Non-staggered Mesh for Simulating Rayleigh-Benard Convection in a Box
An efficient semi-implicit second-order-accurate finite-difference method is
described for studying incompressible Rayleigh-Benard convection in a box, with
sidewalls that are periodic, thermally insulated, or thermally conducting.
Operator-splitting and a projection method reduce the algorithm at each time
step to the solution of four Helmholtz equations and one Poisson equation, and
these are are solved by fast direct methods. The method is numerically stable
even though all field values are placed on a single non-staggered mesh
commensurate with the boundaries. The efficiency and accuracy of the method are
characterized for several representative convection problems.Comment: REVTeX, 30 pages, 5 figure
Magnetic Fields, Relativistic Particles, and Shock Waves in Cluster Outskirts
It is only now, with low-frequency radio telescopes, long exposures with
high-resolution X-ray satellites and gamma-ray telescopes, that we are
beginning to learn about the physics in the periphery of galaxy clusters. In
the coming years, Sunyaev-Zeldovich telescopes are going to deliver further
great insights into the plasma physics of these special regions in the
Universe. The last years have already shown tremendous progress with detections
of shocks, estimates of magnetic field strengths and constraints on the
particle acceleration efficiency. X-ray observations have revealed shock fronts
in cluster outskirts which have allowed inferences about the microphysical
structure of shocks fronts in such extreme environments. The best indications
for magnetic fields and relativistic particles in cluster outskirts come from
observations of so-called radio relics, which are megaparsec-sized regions of
radio emission from the edges of galaxy clusters. As these are difficult to
detect due to their low surface brightness, only few of these objects are
known. But they have provided unprecedented evidence for the acceleration of
relativistic particles at shock fronts and the existence of muG strength fields
as far out as the virial radius of clusters. In this review we summarise the
observational and theoretical state of our knowledge of magnetic fields,
relativistic particles and shocks in cluster outskirts.Comment: 34 pages, to be published in Space Science Review
Water-like anomalies for core-softened models of fluids: One dimension
We use a one-dimensional (1d) core-softened potential to develop a physical
picture for some of the anomalies present in liquid water. The core-softened
potential mimics the effect of hydrogen bonding. The interest in the 1d system
stems from the facts that closed-form results are possible and that the
qualitative behavior in 1d is reproduced in the liquid phase for higher
dimensions. We discuss the relation between the shape of the potential and the
density anomaly, and we study the entropy anomaly resulting from the density
anomaly. We find that certain forms of the two-step square well potential lead
to the existence at T=0 of a low-density phase favored at low pressures and of
a high-density phase favored at high pressures, and to the appearance of a
point at a positive pressure, which is the analog of the T=0 ``critical
point'' in the Ising model. The existence of point leads to anomalous
behavior of the isothermal compressibility and the isobaric specific heat
.Comment: 22 pages, 7 figure
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