8,489 research outputs found
End-to-End QoS Support for a Medical Grid Service Infrastructure
Quality of Service support is an important prerequisite for the adoption of Grid technologies for medical applications. The GEMSS Grid infrastructure addressed this issue by offering end-to-end QoS in the form of explicit timeliness guarantees for compute-intensive medical simulation services. Within GEMSS, parallel applications installed on clusters or other HPC hardware may be exposed as QoS-aware Grid services for which clients may dynamically negotiate QoS constraints with respect to response time and price using Service Level Agreements. The GEMSS infrastructure and middleware is based on standard Web services technology and relies on a reservation based approach to QoS coupled with application specific performance models. In this paper we present an overview of the GEMSS infrastructure, describe the available QoS and security mechanisms, and demonstrate the effectiveness of our methods with a Grid-enabled medical imaging service
A floor sensor system for gait recognition
This paper describes the development of a prototype floor sensor as a gait recognition system. This could eventually find deployment as a standalone system (eg. a burglar alarm system) or as part of a multimodal biometric system. The new sensor consists of 1536 individual sensors arranged in a 3 m by 0.5 m rectangular strip with an individual sensor area of 3 cm2. The sensor floor operates at a sample rate of 22 Hz. The sensor itself uses a simple design inspired by computer keyboards and is made from low cost, off the shelf materials. Application of the sensor floor to a small database of 15 individuals was performed. Three features were extracted : stride length, stride cadence, and time on toe to time on heel ratio. Two of these measures have been used in video based gait recognition while the third is new to this analysis. These features proved sufficient to achieve an 80 % recognition rate
A smart environment for biometric capture
The development of large scale biometric systems require experiments to be performed on large amounts of data. Existing capture systems are designed for fixed experiments and are not easily scalable. In this scenario even the addition of extra data is difficult. We developed a prototype biometric tunnel for the capture of non-contact biometrics. It is self contained and autonomous. Such a configuration is ideal for building access or deployment in secure environments. The tunnel captures cropped images of the subject's face and performs a 3D reconstruction of the person's motion which is used to extract gait information. Interaction between the various parts of the system is performed via the use of an agent framework. The design of this system is a trade-off between parallel and serial processing due to various hardware bottlenecks. When tested on a small population the extracted features have been shown to be potent for recognition. We currently achieve a moderate throughput of approximate 15 subjects an hour and hope to improve this in the future as the prototype becomes more complete
Timing properties of ULX pulsars: optically thick envelopes and outflows
It has recently been discovered that a fraction of ultra-luminous X-ray
sources (ULXs) exhibit X-ray pulsations, and are therefore powered by
super-Eddington accretion onto magnetized neutron stars (NSs). For typical ULX
mass accretion rates (), the inner parts of
the accretion disc are expected to be in the supercritical regime, meaning that
some material is lost in a wind launched from the disc surface, while the rest
forms an optically thick envelope around the NS as it follows magnetic field
lines from the inner disc radius to the magnetic poles of the star. The
envelope hides the central object from a distant observer and defines key
observational properties of ULX pulsars: their energy spectrum, polarization,
and timing features. The optical thickness of the envelope is affected by the
mass losses from the disc. We calculate the mass loss rate due to the wind in
ULX pulsars, accounting for the NS magnetic field strength and advection
processes in the disc. We argue that the detection of strong outflows from ULX
pulsars can be considered evidence of a relatively weak dipole component of the
NS magnetic field. We estimate the influence of mass losses on the optical
thickness of the envelope and analyze how the envelope affects broadband
aperiodic variability in ULXs. We show that brightness fluctuations at high
Fourier frequencies can be strongly suppressed by multiple scatterings in the
envelope and that the strength of suppression is determined by the mass
accretion rate and geometrical size of the magnetosphere.Comment: 12 pages, 11 figures, accepted for publication in MNRA
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An on-going investigation into the ecological determinants of Lyme disease in the South Downs National Park, South East England: the potential for 'One Health' based interventions
Lyme borreliosis (LB) is a tick-borne infectious disease, with UK annual diagnoses trebling over the last two decades. The widening UK distribution of the main LB tick vector (Ixodes ricinus) has been linked to deer population expansion. However, the wider ecological determinants that affect the density of infected ticks are poorly understood. Deer have key roles in most, but not all, UK LB disease systems, but they are non-competent hosts for the pathogen itself, and small mammals or birds are usually obligatory disease reservoirs. In addition, the relapsing fever spirochete Borrelia miyomotoi was detected in the UK in 2014, but the spread and extent of this emerging human pathogen is still unknown. To date, five sites have been drag-sampled across the South Downs National Park (SDNP); with ticks being successfully obtained from all sites. In addition, ticks have been collected from a further sixteen sites where individual or multiple deer were sampled. Currently, ticks are undergoing genetic analysis to determine the host animals involved in the disease cycle, and the presence of Borrelia sp. The study aims to provide a mapped assessment of LB risk across the South Downs National Park, and identify the disease reservoir community composition. The results will help elucidate the causal factors in the SDNP, and support development of policies that avoid or minimise conflicts between public and ecosystem health
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Ecological determinants of Lyme borreliosis hazard in the South Downs National Park and the potential for One Health based interventions (work in progress)
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Avalanches and the Renormalization Group for Pinned Charge-Density Waves
The critical behavior of charge-density waves (CDWs) in the pinned phase is
studied for applied fields increasing toward the threshold field, using
recently developed renormalization group techniques and simulations of
automaton models. Despite the existence of many metastable states in the pinned
state of the CDW, the renormalization group treatment can be used successfully
to find the divergences in the polarization and the correlation length, and, to
first order in an expansion, the diverging time scale. The
automaton models studied are a charge-density wave model and a ``sandpile''
model with periodic boundary conditions; these models are found to have the
same critical behavior, associated with diverging avalanche sizes. The
numerical results for the polarization and the diverging length and time scales
in dimensions are in agreement with the analytical treatment. These
results clarify the connections between the behaviour above and below
threshold: the characteristic correlation lengths on both sides of the
transition diverge with different exponents. The scaling of the distribution of
avalanches on the approach to threshold is found to be different for automaton
and continuous-variable models.Comment: 29 pages, 11 postscript figures included, REVTEX v3.0 (dvi and PS
files also available by anonymous ftp from external.nj.nec.com in directory
/pub/alan/cdwfigs
Anisotropic evolution of 5D Friedmann-Robertson-Walker spacetime
We examine the time evolution of the five-dimensional Einstein field
equations subjected to a flat, anisotropic Robertson-Walker metric, where the
3D and higher-dimensional scale factors are allowed to dynamically evolve at
different rates. By adopting equations of state relating the 3D and
higher-dimensional pressures to the density, we obtain an exact expression
relating the higher-dimensional scale factor to a function of the 3D scale
factor. This relation allows us to write the Friedmann-Robertson-Walker field
equations exclusively in terms of the 3D scale factor, thus yielding a set of
4D effective Friedmann-Robertson-Walker field equations. We examine the
effective field equations in the general case and obtain an exact expression
relating a function of the 3D scale factor to the time. This expression
involves a hypergeometric function and cannot, in general, be inverted to yield
an analytical expression for the 3D scale factor as a function of time. When
the hypergeometric function is expanded for small and large arguments, we
obtain a generalized treatment of the dynamical compactification scenario of
Mohammedi [Phys.Rev.D 65, 104018 (2002)] and the 5D vacuum solution of Chodos
and Detweiler [Phys.Rev.D 21, 2167 (1980)], respectively. By expanding the
hypergeometric function near a branch point, we obtain the perturbative
solution for the 3D scale factor in the small time regime. This solution
exhibits accelerated expansion, which, remarkably, is independent of the value
of the 4D equation of state parameter w. This early-time epoch of accelerated
expansion arises naturally out of the anisotropic evolution of 5D spacetime
when the pressure in the extra dimension is negative and offers a possible
alternative to scalar field inflationary theory.Comment: 20 pages, 4 figures, paper format streamlined with main results
emphasized and details pushed to appendixes, current version matches that of
published versio
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