255 research outputs found
Non-communicating syringomyelia: a feature of spinal cord involvement in multiple sclerosis
In patients with multiple sclerosis (MS) non-communicating syringomyelia (NCS) has been described as an incidental finding in case studies and small case series. NCS in MS patients commonly leads to uncertainty particularly as the clinical picture of NCS is variable and surgical therapy may be considered. Up to date little is known about the prevalence and clinical importance of NCS in MS. We report the imaging and clinical characteristics of NCS formations in nine MS patients from a 1 year follow-up study in a representative group of 202 MS (4.5%) patients. Brain and spinal cord MRI was performed as part of a genetic study. NCS did commonly extend the central canal and the cord was slightly distended at the level of the syrinx. The cord and syrinx showed no tendency to change in size or shape over 1 year. Despite thorough search into the clinical history and current clinical status no definite but only minimal indications of symptoms potentially related to the NCS were found. We confirm that NCS may occur in MS patients with spinal cord pathology. It can be a subtle finding without clinical correlates. Syrinx formations are more likely to be a consequence of MS cord pathology than a coincidental findin
Magnetic and pair correlations of the Hubbard model with next-nearest-neighbor hopping
A combination of analytical approaches and quantum Monte Carlo simulations is
used to study both magnetic and pairing correlations for a version of the
Hubbard model that includes second-neighbor hopping as a
model for high-temperature superconductors. Magnetic properties are analyzed
using the Two-Particle Self-Consistent approach. The maximum in magnetic
susceptibility as a function of doping appears both at finite
and at but for two totally different physical reasons. When
, it is induced by antiferromagnetic correlations while at
it is a band structure effect amplified by interactions.
Finally, pairing fluctuations are compared with -matrix results to
disentangle the effects of van Hove singularity and of nesting on
superconducting correlations. The addition of antiferromagnetic fluctuations
increases slightly the -wave superconducting correlations despite the
presence of a van Hove singularity which tends to decrease them in the
repulsive model. Some aspects of the phase diagram and some subtleties of
finite-size scaling in Monte Carlo simulations, such as inverted finite-size
dependence, are also discussed.Comment: Revtex, 8 pages + 15 uuencoded postcript figure
Quantum Monte Carlo study of the 3D attractive Hubbard model
We study the three-dimensional (3D) attractive Hubbard model by means of the
Determinant Quantum Monte Carlo method. This model is a prototype for the
description of the smooth crossover between BCS superconductivity and
Bose-Einstein condensation. By detailed finite-size scaling we extract the
finite-temperature phase diagram of the model. In particular, we interpret the
observed behavior according to a scenario of two fundamental temperature
scales; T* associated with Cooper pair formation and Tc with condensation
(giving rise to long-range superconducting order). Our results also indicate
the presence of a recently conjectured phase transition hidden by the
superconducting state. A comparison with the 2D case is briefly discussed,
given its relevance for the physics of high-Tc cuprate superconductors.Comment: 4 pages, 4 Postscript figure
History, trauma and remembering in Kivu Ruhorahoza’s Grey Matter (2011)
In 1994, the genocide in Rwanda claimed at least 800,000 lives in just 100 days. More than 20 years on, the memory and trauma of the atrocities still permeate the Rwandan society. This article explores how some of these different manifestations of trauma (individual and collective, actual and inherited, real and imagined, that of survivors and perpetrators), and especially their relationship to the genocide as a historical event, shape the internationally recognized Rwandan feature film, Kivu Ruhorahoza’s Grey Matter (2011). Drawing on the scholarship on trauma, the article examines Grey Matter’s uniqueness within feature films on the topic and its ambition to tackle the impossibility of memory and objectivity vis-à-vis varied experiences of the genocide. It traces the connection between trauma and Grey Matter’s structure, which refuses to offer events a firm chronological placement, both within and beyond the narrative
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