1,403 research outputs found
Altered white matter connectivity associated with visual hallucinations following occipital stroke
Introduction
Visual hallucinations that arise following vision loss stem from aberrant functional activity in visual cortices and an imbalance of activity across associated cortical and subcortical networks subsequent to visual pathway damage. We sought to determine if structural changes in white matter connectivity play a role in cases of chronic visual hallucinations associated with visual cortical damage.
Methods
We performed diffusion tensor imaging (DTI) and probabilistic fiber tractography to assess white matter connectivity in a patient suffering from continuous and disruptive phosphene (simple) visual hallucinations for more than 2 years following right occipital stroke. We compared these data to that of healthy ageâmatched controls.
Results
Probabilistic tractography to reconstruct white matter tracts suggests regeneration of terminal fibers of the ipsilesional optic radiations in the patient. However, arrangement of the converse reconstruction of these tracts, which were seeded from the ipsilesional visual cortex to the intrahemispheric lateral geniculate body, remained disrupted. We further observed compromised structural characteristics, and changes in diffusion (measured using diffusion tensor indices) of white matter tracts in the patient connecting the visual cortex with frontal and temporal regions, and also in interhemispheric connectivity between visual cortices.
Conclusions
Cortical remapping and the disruption of communication between visual cortices and remote regions are consistent with our previous functional magnetic resonance imaging (fMRI) data showing imbalanced functional activity of the same regions in this patient (Rafique et al, 2016, Neurology, 87, 1493â1500). Longâterm adaptive and disruptive changes in white matter connectivity may account for the rare nature of cases presenting with chronic and continuous visual hallucinations
On the absence of appreciable half-life changes in alpha emitters cooled in metals to 1 Kelvin and below
The recent suggestion that dramatic changes may occur in the lifetime of
alpha and beta decay when the activity, in a pure metal host, is cooled to a
few Kelvin, is examined in the light of published low temperature nuclear
orientation (LTNO) experiments, with emphasis here on alpha decay. In LTNO
observations are made of the anisotropy of radioactive emissions with respect
to an axis of orientation. Correction of data for decay of metallic samples
held at temperatures at and below 1 Kelvin for periods of days and longer has
been a routine element of LTNO experiments for many years. No evidence for any
change of half life on cooling, with an upper level of less than 1%, has been
found, in striking contrast to the predicted changes, for alpha decay, of
several orders of magnitude. The proposal that such dramatic changes might
alleviate problems of disposal of long-lived radioactive waste is shown to be
unrealistic.Comment: 27 pages, 12 figures, accepted for publication in Nucl.Phys.A.
Revised version, including quantitative analysis of the sensitivity of
nuclear orientation experiments, discussed in this work, to changes of
alpha-decay lifetimes in metals at low temperatures. Conclusions remain
unchange
Thermal imaging metrology using high dynamic range near-infrared photovoltaic-mode camera
The measurement of a wide temperature range in a scene requires hardware capable of high dynamic range imaging. We describe a novel near-infrared thermal imaging system operating at a wavelength of 940 nm based on a commercial photovoltaic mode high dynamic range camera and analyse its measurement uncertainty. The system is capable of measuring over an unprecedently wide temperature range; however, this comes at the cost of a reduced temperature resolution and increased uncertainty compared to a conventional CMOS camera operating in photodetective mode. Despite this, the photovoltaic mode thermal camera has an acceptable level of uncertainty for most thermal imaging applications with an NETD of 4â12 °C and a combined measurement uncertainty of approximately 1% K if a low pixel clock is used. We discuss the various sources of uncertainty and how they might be minimised to further improve the performance of the thermal camera. The thermal camera is a good choice for imaging low frame rate applications that have a wide inter-scene temperature range
Torque-angle-velocity relationships and muscle performance of professional and youth soccer players
Soccer matches consist of a variety of different activities, including repeated sprints. Time to attain velocity (TTAV), load range (LR) and the torque-angle-velocity relationship (TAV3D) represent an important measurement of muscle performance however there are few studies related. The aim of this study was to compare these outcomes between soccer players of different age category. Seventeen professional (PRO) and seventeen under-17 (U17) soccer players were assessed for concentric knee flexion/extension at 60, 120 and 300 °/s. For the extensor muscles, differences were found in favor of the U17 group for TTAV and LR outcomes at 120 °/s, however, the PRO group maintained higher torques in both movement directions in comparison to the U17 in TAV3D evaluation. These results suggest that muscle performance of the PRO group is more efficient than the U17 group
Couplings of light I=0 scalar mesons to simple operators in the complex plane
The flavour and glue structure of the light scalar mesons in QCD are probed
by studying the couplings of the I=0 mesons and to the
operators , and to two photons. The Roy dispersive
representation for the amplitude is used to determine the
pole positions as well as the residues in the complex plane. On the real axis,
is constrained to solve the Roy equation together with elastic
unitarity up to the K\Kbar threshold leading to an improved description of
the . The problem of using a two-particle threshold as a matching
point is discussed. A simple relation is established between the coupling of a
scalar meson to an operator and the value of the related pion form-factor
computed at the resonance pole. Pion scalar form-factors as well as two-photon
partial-wave amplitudes are expressed as coupled-channel Omn\`es dispersive
representations. Subtraction constants are constrained by chiral symmetry and
experimental data. Comparison of our results for the couplings with
earlier determinations of the analogous couplings of the lightest I=1 and
scalar mesons are compatible with an assignment of the ,
, , into a nonet. Concerning the gluonic operator
we find a significant coupling to both the and the
.Comment: 31 pages, 5 figure
Changes in body composition after thermal injury in the rat.
1. The effects on body composition, measured by direct techniques, of a controlled 25% body-surfacearea thermal injury have been studied in two groups of forty male Wistar rats. 2. The extent of weight loss in the animals was directly related to their energy deficit resulting from a combination of injury, food intake and rate of wound healing. 3. Body fat proved the most labile source of tissue energy, decreasing to a minimum of approximately 30 g/kg body-weight. 4. Relationships between water and fat, and water and protein seen in control animals were not significantly different in the traumatized group
Linear stability analysis of transverse dunes
Sand-moving winds blowing from a constant direction in an area of high sand
availability form transverse dunes, which have a fixed profile in the direction
orthogonal to the wind. Here we show, by means of a linear stability analysis,
that transverse dunes are intrinsically unstable. Any along-axis perturbation
on a transverse dune amplify in the course of dune migration due to the
combined effect of two main factors, namely: the lateral transport through
avalanches along the dune's slip-face, and the scaling of dune migration
velocity with the inverse of the dune height. Our calculations provide a
quantitative explanation for recent observations from experiments and numerical
simulations, which showed that transverse dunes moving on the bedrock cannot
exist in a stable form and decay into a chain of crescent-shaped barchans.Comment: 8 pages, 4 figure
The new IOC and IAAF policies on female eligibility: old Emperor, new clothes?
The Caster Semenya debacle touched off by the 2009 Berlin World Athletics Championships resulted finally in IOC and IAAF abandonment of sex testing, which gave way to procedures that make female competition eligibility dependent upon the level of serum testosterone, which must be below the male range or instrumentally countered by androgen resistance. We argue that the new policy is unsustainable because (i) the testosterone-performance connection it posits is uncompelling; (ii) testosterone-induced female advantage is not ipso facto unfair advantage; (iii) the new policy reflects the gender policing impulses endemic to sport as well as the broader cultural impulses to monstrify women and to doctor women who have nothing wrong with them; (iv) femaleâmale performance disparities are not the only reason for sex-segregated sport, but co-exist with respectable cultural and practical reasons, which (v) provide a powerful case for allowing athletes to compete in the sex category congruent with their gender identity
alpha'-exact entropies for BPS and non-BPS extremal dyonic black holes in heterotic string theory from ten-dimensional supersymmetry
We calculate near-horizon solutions for four-dimensional 4-charge and
five-dimensional 3-charge black holes in heterotic string theory from the part
of the ten-dimensional tree-level effective action which is connected to
gravitational Chern-Simons term by supersymmetry. We obtain that the entropies
of large black holes exactly match the alpha'-exact statistical entropies
obtained from microstate counting (D=4) and AdS/CFT correspondence (D=5).
Especially interesting is that we obtain agreement for both BPS and non-BPS
black holes, contrary to the case of R^2-truncated (four-derivative) actions
(D-dimensional N=2 off-shell supersymmetric or Gauss-Bonnet) were used, which
give the entropies agreeing (at best) just for BPS black holes. The key
property of the solutions, which enabled us to tackle the action containing
infinite number of terms, is vanishing of the Riemann tensor \bar{R}_{MNPQ}
obtained from torsional connection defined with \bar{\Gamma} = \Gamma - H/2.
Morover, if every monomial of the remaining part of the effective action would
contain at least two Riemanns \bar{R}_{MNPQ}, it would trivially follow that
our solutions are exact solutions of the full heterotic effective action in
D=10. The above conjecture, which appeared (in this or stronger form) from time
to time in the literature, has controversial status, but is supported by the
most recent calculations of Richards (arXiv:0807.3453 [hep-th]). Agreement of
our results for the entropies with the microscopic ones supports the
conjecture. As for small black holes, our solutions in D=5 still have singular
horizons.Comment: 28 pages; v2: minor changes, references added; v3: extended
discussion on small black holes in sec. 5.4, more references added, accepted
in JHE
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