5,133 research outputs found
Presenting features of primary angle-closure glaucoma in patients of mixed ethnic background
The relative frequency with which patients present with acute or chronic angle-closure glaucoma depends on their ethnic background. In order to examine the presenting features and effects of primary angle-closure glaucoma in people of mixed ethnicity, we reviewed all 'coloured' patients who presented to Groote Schuur Hospital with this diagnosis during a 5-year period. Of the 92 patients, 33 (36%) presented with acute angle-closure glaucoma and 59 (64%) with chronic angleclosure glaucoma. The level of intra-ocular pressure on presentation correlated well with the number of quadrants of angle closure (correlation coefficient: r =0,73, P < 0,001). When individual eyes were assessed, a mean cup/disc ratio of ≥ 0,8 was present in 350 /0 (65/184) and glaucomatous visual field loss was present in 56,5% (104/184). Total uni-ocular blindness secondary to chronic angle-closure glaucoma, was found in 16 (17%) patients. This study indicates that 'coloured' patients with primary angle-closure glaucoma are more likely to present with chronic symptoms and signs, and that the disease may result in devastating ocular damage and visual loss. In patients of mixed ethnic background with signs of primary glaucoma, chronic angle-closure should be excluded by careful gonioscopic evaluation of the drainage structures of the eye
Malignant Glaucoma: A Review of the Modern Literature
Malignant glaucoma is a rare form of glaucoma that typically follows surgery in patients with primary angle closure and primary angle-closure glaucoma. In this paper, the clinical features, classification, pathogenesis, and principles of management are discussed. Despite a high prevalence of primary angle closure glaucoma in South-East Asia, the vast majority of cases of malignant glaucoma are reported in White populations. This may reflect differing mechanisms of angle closure in White and Asian patients, which somehow reduces the likelihood of an aberrant relationship developing between the lens, ciliary body, anterior hyaloid, and vitreous structures within the eye. Although the exact underlying pathogenic mechanism remains unclear, the prognosis is good with modern medical, laser, and surgical treatment modalities
Shear-banding in a lyotropic lamellar phase, Part 2: Temporal fluctuations
We analyze the temporal fluctuations of the flow field associated to a
shear-induced transition in a lyotropic lamellar phase: the layering transition
of the onion texture. In the first part of this work [Salmon et al., submitted
to Phys. Rev. E], we have evidenced banded flows at the onset of this
shear-induced transition which are well accounted for by the classical picture
of shear-banding. In the present paper, we focus on the temporal fluctuations
of the flow field recorded in the coexistence domain. These striking dynamics
are very slow (100--1000s) and cannot be due to external mechanical noise.
Using velocimetry coupled to structural measurements, we show that these
fluctuations are due to a motion of the interface separating the two
differently sheared bands. Such a motion seems to be governed by the
fluctuations of , the local stress at the interface between the
two bands. Our results thus provide more evidence for the relevance of the
classical mechanical approach of shear-banding even if the mechanism leading to
the fluctuations of remains unclear
Velocity profiles in shear-banding wormlike micelles
Using Dynamic Light Scattering in heterodyne mode, we measure velocity
profiles in a much studied system of wormlike micelles (CPCl/NaSal) known to
exhibit both shear-banding and stress plateau behavior. Our data provide
evidence for the simplest shear-banding scenario, according to which the
effective viscosity drop in the system is due to the nucleation and growth of a
highly sheared band in the gap, whose thickness linearly increases with the
imposed shear rate. We discuss various details of the velocity profiles in all
the regions of the flow curve and emphasize on the complex, non-Newtonian
nature of the flow in the highly sheared band.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Let
Energetics, skeletal dynamics and long-term predictions in Kolmogorov-Lorenz systems
We study a particular return map for a class of low dimensional chaotic
models called Kolmogorov Lorenz systems, which received an elegant general
Hamiltonian description and includes also the famous Lorenz63 case, from the
viewpoint of energy and Casimir balance. In particular it is considered in
detail a subclass of these models, precisely those obtained from the Lorenz63
by a small perturbation on the standard parameters, which includes for example
the forced Lorenz case in Ref.[6]. The paper is divided into two parts. In the
first part the extremes of the mentioned state functions are considered, which
define an invariant manifold, used to construct an appropriate Poincare surface
for our return map. From the experimental observation of the simple orbital
motion around the two unstable fixed points, together with the circumstance
that these orbits are classified by their energy or Casimir maximum, we
construct a conceptually simple skeletal dynamics valid within our sub class,
reproducing quite well the Lorenz map for Casimir. This energetic approach
sheds some light on the physical mechanism underlying regime transitions. The
second part of the paper is devoted to the investigation of a new type of
maximum energy based long term predictions, by which the knowledge of a
particular maximum energy shell amounts to the knowledge of the future
(qualitative) behaviour of the system. It is shown that, in this respect, a
local analysis of predictability is not appropriate for a complete
characterization of this behaviour. A perspective on the possible extensions of
this type of predictability analysis to more realistic cases in (geo)fluid
dynamics is discussed at the end of the paper.Comment: 21 pages, 14 figure
Simulation of Pasture Phase Options for Mixed Livestock and Cropping Enterprises
In southern Australia, 50% of grain-producing farms also run beef and/or sheep enterprises. Legume pasture leys are used to replace soil nitrogen and manage crop disease risks. Deep-rooted perennials, predominantly lucerne (Medicago sativa), are replacing annual Trifolium subterraneum-based leys to increase pasture production. They also have the environmental benefits of limiting soil acidity, rising water tables and dryland salinity. After recent droughts depletion of soil water by lucerne has penalised wheat yields. Decision support tools can help farmers evaluate the long-term effects of grazed annual and perennial leys on animal and crop production at the whole farm level
Shear-banding in a lyotropic lamellar phase, Part 1: Time-averaged velocity profiles
Using velocity profile measurements based on dynamic light scattering and
coupled to structural and rheological measurements in a Couette cell, we
present evidences for a shear-banding scenario in the shear flow of the onion
texture of a lyotropic lamellar phase. Time-averaged measurements clearly show
the presence of structural shear-banding in the vicinity of a shear-induced
transition, associated to the nucleation and growth of a highly sheared band in
the flow. Our experiments also reveal the presence of slip at the walls of the
Couette cell. Using a simple mechanical approach, we demonstrate that our data
confirms the classical assumption of the shear-banding picture, in which the
interface between bands lies at a given stress . We also outline
the presence of large temporal fluctuations of the flow field, which are the
subject of the second part of this paper [Salmon {\it et al.}, submitted to
Phys. Rev. E]
Trisomy 19 ependymoma, a newly recognized genetico-histological association, including clear cell ependymoma
Ependymal tumors constitute a clinicopathologically heterogeneous group of brain tumors. They vary in regard to their age at first symptom, localization, morphology and prognosis. Genetic data also suggests heterogeneity. We define a newly recognized subset of ependymal tumors, the trisomy 19 ependymoma. Histologically, they are compact lesions characterized by a rich branched capillary network amongst which tumoral cells are regularly distributed. When containing clear cells they are called clear cell ependymoma. Most trisomy 19 ependymomas are supratentorial WHO grade III tumors of the young. Genetically, they are associated with trisomy 19, and frequently with a deletion of 13q21.31-31.2, three copies of 11q13.3-13.4, and/or deletions on chromosome 9. These altered chromosomal regions are indicative of genes and pathways involved in trisomy 19 ependymoma tumorigenesis. Recognition of this genetico-histological entity allows better understanding and dissection of ependymal tumors
Socioeconomic position and children\u27s physical activity and sedentary behaviors : longitudinal findings from the CLAN study
Background: This study aimed to examine cross-sectional and longitudinal associations between socioeconomic position (SEP) and physical activity and sedentary behaviors amongst children and adolescents. Methods: Maternal education was reported by parents of 184 5-6 year-old and 358 10-12 year-old children in 2001. In 2001 and 2004, physical activity was assessed by accelerometry. Older children self-reported and parents of younger children proxy-reported physical activity and television (TV) viewing behaviors. Linear regression was used to predict physical activity and sedentary behaviors, and changes in these behaviors, from maternal education. Results: Among all children, accelerometer-determined and self/parent-reported moderate and vigorous physical activity declined over three years. Girls of higher SEP demonstrated greater decreases in TV viewing behaviours than those of low SEP. In general, no prospective associations were evident between SEP and objectively-assessed physical activity. A small number of prospective associations were noted between SEP and self-reported physical activity, but these were generally weak and inconsistent in direction. Conclusions: This study did not find strong evidence that maternal education was cross-sectionally or longitudinally predictive of children’s physical activity or sedentary behaviors. Given the well-documented inverse relationship of SEP with physical activity levels in adult samples, findings suggest that such disparities may emerge after adolescence.<br /
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