3,787 research outputs found
Medical education on fitness to drive : a survey of all UK medical schools
Aim: To identify the extent to which medical aspects of fitness to drive (FTD) are taught within UK medical schools.
Methods: A survey of all 32 UK medical schools. In-depth interviews with a range of staff at two medical schools; telephone survey of 30 schools.
Results: Two thirds of schools reported specific teaching on medical aspects of FTD but few covered it in any depth or in relation to specific medical conditions. Only one school taught FTD in relation to elderly medicine. FTD was an examination topic at only 12 schools.
Conclusion: Teaching on FTD is inconsistent across UK medical schools. Many new doctors will graduate with limited knowledge of medical aspects of FTD
Tight focal spots using azimuthally polarised light from a Fresnel cone
When focusing a light beam at high numerical aperture, the resulting electric
field profile in the focal plane depends on the transverse polarisation
profile, as interference between different parts of the beam needs to be taken
into account. It is well known that radial polarised light produces a
longitudinal polarisation component and can be focused below the conventional
diffraction limit for homogeneously polarised light, and azimuthally polarised
light that carries one unit of angular momentum can achieve even tighter focal
spots. This is of interest for example for enhancing resolution in scanning
microscopy. There are numerous ways to generate such polarisation structures,
however, setups can be expensive and usually rely on birefringent components,
hence prohibiting broadband operation. We have recently demonstrated a passive,
low-cost technique using a simple glass cone (Fresnel cone) to generate beams
with structured polarisation. We show here that the polarisation structure
generated by Fresnel cones focuses better than radial polarised light at all
numerical apertures. Furthermore, we investigate in detail the application of
polarised light structures for two-photon microscopy. Specifically we
demonstrate a method that allows us to generate the desired polarisation
structure at the back aperture of the microscope by pre-compensating any
detrimental phase shifts using a combination of waveplates
The \chi Factor: Determining the Strength of Activity in Low Mass Dwarfs
We describe a new, distance-independent method for calculating the magnetic
activity strength in low mass dwarfs, L_{H\alpha}/L_{bol}. Using a
well-observed sample of nearby stars and cool standards spanning spectral type
M0.5 to L0, we compute ``\chi'', the ratio between the continuum flux near
H-alpha and the bolometric flux, f_{\lambda6560}/f_{bol}. This ratio may be
multiplied by the measured equivalent width of the H-alpha emission line to
yield L_{H\alpha}/L_{bol}. We provide \chi values for all objects in our
sample, as well as fits to \chi as a function of color and average values by
spectral type. This method was used by West et al.(2004) to examine trends in
magnetic activity strength in low mass stars.Comment: 11 pages, 5 figures. Accepted for publication in PAS
A Numerical Method for General Relativistic Magnetohydrodynamics
This paper describes the development and testing of a general relativistic
magnetohydrodynamic (GRMHD) code to study ideal MHD in the fixed background of
a Kerr black hole. The code is a direct extension of the hydrodynamic code of
Hawley, Smarr, and Wilson, and uses Evans and Hawley constrained transport (CT)
to evolve the magnetic fields. Two categories of test cases were undertaken. A
one dimensional version of the code (Minkowski metric) was used to verify code
performance in the special relativistic limit. The tests include Alfv\'en wave
propagation, fast and slow magnetosonic shocks, rarefaction waves, and both
relativistic and non-relativistic shock tubes. A series of one- and
two-dimensional tests were also carried out in the Kerr metric: magnetized
Bondi inflow, a magnetized inflow test due to Gammie, and two-dimensional
magnetized constant- tori that are subject to the magnetorotational
instability.Comment: 37 pages, 14 figures, submitted to ApJ. Animations can be viewed at
http://www.astro.virginia.edu/~jd5v/grmhd/grmhd.htm
A high-order Godunov scheme for global 3D MHD accretion disks simulations. I. The linear growth regime of the magneto-rotational instability
We employ the PLUTO code for computational astrophysics to assess and compare
the validity of different numerical algorithms on simulations of the
magneto-rotational instability in 3D accretion disks. In particular we stress
on the importance of using a consistent upwind reconstruction of the
electro-motive force (EMF) when using the constrained transport (CT) method to
avoid the onset of numerical instabilities. We show that the electro-motive
force (EMF) reconstruction in the classical constrained transport (CT) method
for Godunov schemes drives a numerical instability. The well-studied linear
growth of magneto-rotational instability (MRI) is used as a benchmark for an
inter-code comparison of PLUTO and ZeusMP. We reproduce the analytical results
for linear MRI growth in 3D global MHD simulations and present a robust and
accurate Godunov code which can be used for 3D accretion disk simulations in
curvilinear coordinate systems
A User-Centred Approach Exploring the Potential of a Novel EMG Switch for Control of Assistive Technology
This study examines the potential application of an EMG technology as an assistive control method for individuals with severe physical disabilities. The usability and acceptability of a prototype EMG switch was evaluated with health care professionals, researchers and end users using participatory approaches
High Resolution Simulations of the Plunging Region in a Pseudo-Newtonian Potential: Dependence on Numerical Resolution and Field Topology
New three dimensional magnetohydrodynamic simulations of accretion disk
dynamics in a pseudo-Newtonian Paczynski-Wiita potential are presented. These
have finer resolution in the inner disk than any previously reported. Finer
resolution leads to increased magnetic field strength, greater accretion rate,
and greater fluctuations in the accretion rate. One simulation begins with a
purely poloidal magnetic field, the other with a purely toroidal field.
Compared to the poloidal initial field simulation, a purely toroidal initial
field takes longer to reach saturation of the magnetorotational instability and
produces less turbulence and weaker magnetic field energies. For both initial
field configurations, magnetic stresses continue across the marginally stable
orbit; measured in units corresponding to the Shakura-Sunyaev alpha parameter,
the stress grows from ~0.1 in the disk body to as much as ~10 deep in the
plunging region. Matter passing the inner boundary of the simulation has ~10%
greater binding energy and ~10% smaller angular momentum than it did at the
marginally stable orbit. Both the mass accretion rate and the integrated stress
fluctuate widely on a broad range of timescales.Comment: Accepted for publication in the Astrophysical Journal. For Web
version with mpeg animations see
http://www.astro.virginia.edu/VITA/papers/plunge
MRI channel flows and their parasites
Local simulations of the magnetorotational instability (MRI) in accretion
disks can exhibit recurrent coherent structures called channel flows. The
formation and destruction of these structures may play a role in the
development and saturation of MRI-induced turbulence, and consequently help us
understand the time-dependent accretion behaviour of certain astrophysical
objects. Previous investigations have revealed that channel solutions are
attacked by various parasitic modes, foremost of which is an analogue of the
Kelvin-Helmholtz instability. We revisit these instabilities and show how they
relate to the classical instabilities of plasma physics, the kink and pinch
modes. However, we argue that in most cases channels emerge from developed
turbulence and are eventually destroyed by turbulent mixing, not by the
parasites. The exceptions are the clean isolated channels which appear in
systems near criticality or which emerge from low amplitude initial conditions.
These structures inevitably achieve large amplitudes and are only then
destroyed, giving rise to eruptive behaviour.Comment: 17 pages, 17 figures, accepted by MNRA
Return to driving after traumatic brain injury : a British perspective
Primary Objective: to identify current legal situation, and professional practice in assisting persons with traumatic brain injury (TBI) to return to safe driving after injury.
Methods and Procedures
A brief review of relevant literature, a description of the current statutory and quasi-statutory authorities regulating return to driving after TBI in the UK, and a description of the nature and resolution of clinical and practical dilemmas facing professionals helping return to safe driving after TBI. Each of the 15 UK mobility centres was contacted and literature requested; in addition a representative of each centre responded to a structured telephone survey.
Main Outcome and Results: The current situation in Great Britain is described, with a brief analysis of the strengths and weaknesses both of the current statutory situation, and also the practical situation (driving centres), with suggestions for improvements in practice.
Conclusion
Although brain injury may cause serious limitations in driving ability, previous drivers are not routinely assessed or advised regarding return to driving after TBI
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