5,660 research outputs found
Lumbar puncture for the generalist
The safe and successful performance of a lumbar puncture demands a working and yet specific knowledge as well as competency in performance. This review aims to aid understanding of the knowledge framework, the pitfalls and complications of lumbar puncture. It includes special reference to three dimensional relationships, functional anatomy, imaging anatomy, normal variation and living anatomy. A lumbar puncture is a commonly performed procedure for diagnostic and therapeutic purposes. Epidural and spinal anaesthesia, for example, are common in obstetric practice and involve the same technique as a lumbar puncture except for the endpoint of the needle being in the epidural space and subarachnoid space respectively. The procedure is by no means innocuous and some anatomical pitfalls include inability to find the correct entry site for placement of the lumbar puncture needle and lack of awareness of structures in relation to the advancing needle. Headache is the most common complication and it is important to avoid traumatic and dry taps, herniation syndromes and injury to the terminal end of the spinal cord. With a thorough knowledge of the contraindications, the regional anatomy and rationale of the technique and adequate prior skills practice, a lumbar puncture can be performed safely and successfully
Plasmonic Scaling of Superconducting Metamaterials
Superconducting metamaterials are utilized to study the approach to the
plasmonic limit simply by tuning temperature to modify the superfluid density,
and thus the superfluid plasma frequency. We examine the persistence of
artificial magnetism in a metamaterial made with superconductors in the
plasmonic limit, and compare to the electromagnetic behavior of normal metals
as a function of frequency as the plasma frequency is approached from below.
Spiral-shaped Nb thin film meta-atoms of scaled dimensions are employed to
explore the plasmonic behavior in these superconducting metamaterials, and the
scaling condition allows extraction of the temperature dependent superfluid
density, which is found to be in good agreement with expectations.Comment: 5 pages, 3 figure
On nonlinear viscoelastic deformations - a reappraisal of Fung's quasilinear viscoelastic model
This article offers a reappraisal of Fung's method for quasilinear
viscoelasticity. It is shown that a number of negative features exhibited in
other works, commonly attributed to the Fung approach, are merely a consequence
of the way it has been applied. The approach outlined herein is shown to yield
improved behaviour, and offers a straightforward scheme for solving a wide
range of models. Results from the new model are contrasted with those in the
literature for the case of uniaxial elongation of a bar: for an imposed stretch
of an incompressible bar, and for an imposed load. In the last case, a
numerical solution to a Volterra integral equation is required to obtain the
results. This is achieved by a high order discretisation scheme. Finally, the
stretch of a compressible viscoelastic bar is determined for two distinct
materials: Horgan-Murphy and Gent
Cauchy-perturbative matching and outer boundary conditions I: Methods and tests
We present a new method of extracting gravitational radiation from
three-dimensional numerical relativity codes and providing outer boundary
conditions. Our approach matches the solution of a Cauchy evolution of
Einstein's equations to a set of one-dimensional linear wave equations on a
curved background. We illustrate the mathematical properties of our approach
and discuss a numerical module we have constructed for this purpose. This
module implements the perturbative matching approach in connection with a
generic three-dimensional numerical relativity simulation. Tests of its
accuracy and second-order convergence are presented with analytic linear wave
data.Comment: 13 pages, 6 figures, RevTe
Sustainable Soesterkwartier
The municipality of Amersfoort wants to construct an endurable and sustainable eco-town in the Soesterkwartier neighbourhood, by taking future climate change into account. The impact of climate change at the location of the proposed eco-town was studied by a literature review
Cauchy-perturbative matching and outer boundary conditions: computational studies
We present results from a new technique which allows extraction of
gravitational radiation information from a generic three-dimensional numerical
relativity code and provides stable outer boundary conditions. In our approach
we match the solution of a Cauchy evolution of the nonlinear Einstein field
equations to a set of one-dimensional linear equations obtained through
perturbation techniques over a curved background. We discuss the validity of
this approach in the case of linear and mildly nonlinear gravitational waves
and show how a numerical module developed for this purpose is able to provide
an accurate and numerically convergent description of the gravitational wave
propagation and a stable numerical evolution.Comment: 20 pages, RevTe
Waveform propagation in black hole spacetimes: evaluating the quality of numerical solutions
We compute the propagation and scattering of linear gravitational waves off a
Schwarzschild black hole using a numerical code which solves a generalization
of the Zerilli equation to a three dimensional cartesian coordinate system.
Since the solution to this problem is well understood it represents a very good
testbed for evaluating our ability to perform three dimensional computations of
gravitational waves in spacetimes in which a black hole event horizon is
present.Comment: 13 pages, RevTeX, to appear in Phys. Rev.
The distribution of the maximum of particular random fields
AbstractWe obtain explicit expressions for the distribution of the maximum of particular two-parameter random fields related to the one-parameter Wiener and Slepian processes. The latter expression provides a lower bound to the probability that the maximum exceeds a level for the standard two-parameter Slepian field
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