749 research outputs found
Nonaxisymmetric, multi-region relaxed magnetohydrodynamic equilibrium solutions
We describe a magnetohydrodynamic (MHD) constrained energy functional for
equilibrium calculations that combines the topological constraints of ideal MHD
with elements of Taylor relaxation.
Extremizing states allow for partially chaotic magnetic fields and
non-trivial pressure profiles supported by a discrete set of ideal interfaces
with irrational rotational transforms.
Numerical solutions are computed using the Stepped Pressure Equilibrium Code,
SPEC, and benchmarks and convergence calculations are presented.Comment: Submitted to Plasma Physics and Controlled Fusion for publication
with a cluster of papers associated with workshop: Stability and Nonlinear
Dynamics of Plasmas, October 31, 2009 Atlanta, GA on occasion of 65th
birthday of R.L. Dewar. V2 is revised for referee
Hamilton--Jacobi theory for continuation of magnetic field across a toroidal surface supporting a plasma pressure discontinuity
The vanishing of the divergence of the total stress tensor (magnetic plus
kinetic) in a neighborhood of an equilibrium plasma containing a toroidal
surface of discontinuity gives boundary and jump conditions that strongly
constrain allowable continuations of the magnetic field across the surface. The
boundary conditions allow the magnetic fields on either side of the
discontinuity surface to be described by surface magnetic potentials, reducing
the continuation problem to that of solving a Hamilton--Jacobi equation. The
characteristics of this equation obey Hamiltonian equations of motion, and a
necessary condition for the existence of a continued field across a general
toroidal surface is that there exist invariant tori in the phase space of this
Hamiltonian system. It is argued from the Birkhoff theorem that existence of
such an invariant torus is also, in general, sufficient for continuation to be
possible. An important corollary is that the rotational transform of the
continued field on a surface of discontinuity must, generically, be irrational.Comment: Prepared for submission to Phys. Letts.
Architecture, physical activity and a capability evaluative framework: satisfaction is not enough
Despite recognition that building design can contribute to human health by facilitating increased incidental physical activity, knowledge of how building design can enable this is underdeveloped. Further, there is evidence that design features introduced to support routine physical activity and improve occupant satisfaction may not necessarily lead to increases in actual physical activity. Evaluative frameworks encompassing a range of individual, organisational and built environment factors that contribute to shaping occupant behaviour may provide insight into how buildings can support greater levels of routine physical activity. This paper argues that capability theory can inform our understandings of the dynamic interrelationship between building design and building use. In this paper we describe our approach to developing a framework for capabilities-based evaluation of buildings and building occupant physical activity. Based on a capability perspective we consider the intersection of building ‘domains’ and ‘functionings’ that influence occupant physical activity; and question how such evaluations could account for a range of occupants. The research is of relevance to those engaged in the production of architectural environments and evaluation tools that support physical activity—inclusive of building designers, procurers, managers and occupants
Vitrification of an intermediate level Magnox sludge waste
A novel iron containing alkali alkaline earth borosilicate glass has been developed that can vitrify up to 30 wt% (dry weight) of a Magnox sludge waste in a homogeneous wasteform at a melting temperature of 1200C. Ce was used as a simulant of the actinide content in the waste. The waste was spiked with 0.5wt% of Cs2O of which 90% was retained in the glass. 60% of the Cl was also retained. Mg content limited the waste loading as loadings in excess of 30wt% led to the formation of forsterite and in some cases CeO2 and MgFe2O4 based spinels. PCT leach testing of the glasses for periods up to 180 days indicated the formation of an amorphous magnesium (alumino-)silicate hydrated layer on the glass surface together with barium rich crystalline precipitates. No Ce was detected in the leachate
Computation of multi-region relaxed magnetohydrodynamic equilibria
We describe the construction of stepped-pressure equilibria as extrema of a
multi-region, relaxed magnetohydrodynamic (MHD) energy functional that combines
elements of ideal MHD and Taylor relaxation, and which we call MRXMHD.
The model is compatible with Hamiltonian chaos theory and allows the
three-dimensional MHD equilibrium problem to be formulated in a well-posed
manner suitable for computation.
The energy-functional is discretized using a mixed finite-element, Fourier
representation for the magnetic vector potential and the equilibrium geometry;
and numerical solutions are constructed using the stepped-pressure equilibrium
code, SPEC.
Convergence studies with respect to radial and Fourier resolution are
presented.The authors gratefully acknowledge support of the
U.S. Department of Energy and the Australian Research
Council, through Grants DP0452728, FT0991899, and
DP110102881
Effects of Preventative Ankle Taping on Planned Change-of-Direction and Reactive Agility Performance and Ankle Muscle Activity in Basketballers
This study investigated the effects of preventative ankle taping on planned change-of-direction and reactive agility performance and peak ankle muscle activity in basketballers. Twenty male basketballers (age = 22.30 ± 3.97 years; height = 1.84 ± 0.09 meters; body mass = 85.96 ± 11.88 kilograms) with no ankle pathologies attended two testing sessions. Within each session, subjects completed six planned and six reactive randomized trials (three to the left and three to the right for each condition) of the Y-shaped agility test, which was recorded by timing lights. In one session, subjects had both ankles un-taped. In the other, both ankles were taped using a modified subtalar sling. Peak tibialis anterior, peroneus longus (PL), peroneus brevis (PB), and soleus muscle activity was recorded for both the inside and outside legs across stance phase during the directional change, which was normalized against 10-meter sprint muscle activity (nEMG). Both the inside and outside cut legs during the change-of-direction step were investigated. Repeated measures ANOVA determined performance time and nEMG differences between un-taped and taped conditions. There were no differences in planned change-of-direction or reactive agility times between the conditions. Inside cut leg PL nEMG decreased when taped for the planned left, reactive left, and reactive right cuts (p = 0.01). Outside leg PB and soleus nEMG increased during the taped planned left cut (p = 0.02). There were no other nEMG changes during the cuts with taping. Taping did not affect change-of-direction or agility performance. Inside leg PL activity was decreased, possibly due to the tape following the line of muscle action. This may reduce the kinetic demand for the PL during cuts. In conclusion, ankle taping did not significantly affect planned change-of-direction or reactive agility performance, and did not demonstrate large changes in activity of the muscle complex in healthy basketballers
Accurate PCR detection of influenza A/B and respiratory syncytial viruses by use of Cepheid Xpert Flu+RSV Xpress Assay in point-of-care settings: Comparison to Prodesse ProFlu+
ABSTRACT
The Xpert Flu+RSV Xpress Assay is a fast, automated
in vitro
diagnostic test for qualitative detection and differentiation of influenza A and B viruses and respiratory syncytial virus (RSV) performed on the Cepheid GeneXpert Xpress System. The objective of this study was to establish performance characteristics of the Xpert Flu+RSV Xpress Assay compared to those of the Prodesse ProFlu+ real-time reverse transcription-PCR (RT-PCR) assay (ProFlu+) for the detection of influenza A and B viruses as well as RSV in a Clinical Laboratory Improvement Amendments (CLIA)-waived (CW) setting. Overall, the assay, using fresh and frozen nasopharyngeal (NP) swabs, demonstrated high concordance with results of the ProFlu+ assay in the combined CW and non-CW settings with positive percent agreements (PPA) (100%, 100%, and 97.1%) and negative percent agreements (NPA) (95.2%, 99.5%, and 99.6%) for influenza A and B viruses and RSV, respectively. In conclusion, this multicenter study using the Cepheid Xpert Flu+RSV Xpress Assay demonstrated high sensitivities and specificities for influenza A and B viruses and RSV in ∼60 min for use at the point-of-care in the CW setting.
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Reaction-diffusion and reaction-subdiffusion equations on arbitrarily evolving domains
Reaction-diffusion equations are widely used as the governing evolution
equations for modeling many physical, chemical, and biological processes. Here
we derive reaction-diffusion equations to model transport with reactions on a
one-dimensional domain that is evolving. The model equations, which have been
derived from generalized continuous time random walks, can incorporate
complexities such as subdiffusive transport and inhomogeneous domain stretching
and shrinking. A method for constructing analytic expressions for short time
moments of the position of the particles is developed and moments calculated
from this approach are shown to compare favourably with results from random
walk simulations and numerical integration of the reaction transport equation.
The results show the important role played by the initial condition. In
particular, it strongly affects the time dependence of the moments in the short
time regime by introducing additional drift and diffusion terms. We also
discuss how our reaction transport equation could be applied to study the
spreading of a population on an evolving interface.Comment: 38 pages, 10 figure
Left atrial late gadolinium enhancement following external beam radiation for lymphoma: a potential model for exploring radiation-related heart disease
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