Direct and inverse pumping in flows with homogeneous and non-homogeneous swirl

The conditions in which meridional recirculations appear in swirling flows above a fixed wall are analysed. In the classical Bodew\"adt problem, where the swirl tends towards an aysmptotic value away from the wall, the well-known "tea-cup effect" drives a flow away from the plate at the centre of the vortex. Simple dimensional arguments applied to a single vortex show that if the intensity of the swirl decreases away from the wall, the sense of the recirculation can be inverted, and that the associated flow rate scales with the swirl gradient. Only if the flow is quasi-2D, does the classical tea-cup effect take place. This basic theory is confirmed by numerical simulations of a square array of steady, electrically driven vortices. Experiments in the turbulent regimes of the same configuration reveal that these mechanisms are active in the average flow and in its fluctuating part. The mechanisms singled out in this letter provide an explanation for previously observed phenomena in electrolyte flows. They also put forward a possible mechanism for the generation of helicity in flows close to two-dimensionality, which plays a key role in the transition between 2D and 3D turbulence

A vector-valued ground motion intensity measure incorporating normalized spectral area

A vector-valued intensity measure is presented, which incorporates a relative measure represented by the normalized spectral area. The proposed intensity measure is intended to have high correlation with specific relative engineering demand parameters, which collectively can provide information regarding the damage state and collapse potential of the structure. Extensive dynamic analyses are carried out on a single-degree-of-freedom system with a modified Clough–Johnston hysteresis model, using a dataset of 40 ground motions, in order to investigate the proposed intensity measure characteristics. Response is expressed using the displacement ductility, and the normalized hysteretic energy, both of which are relative engineering demand parameters. Through regression analysis the correlation between the proposed intensity measure and the engineering demand parameters is evaluated. Its domain of applicability is investigated through parametric analysis, by varying the period and the strain-hardening stiffness. Desirable characteristics such as efficiency, sufficiency, and statistical independence are examined. The proposed intensity measure is contrasted to another one, with respect to its correlation to the engineering demand parameters. An approximate procedure for estimating the optimum normalized spectral area is also presented. It is demonstrated that the proposed intensity measure can be used in intensity-based assessments, and, with proper selection of ground motions, in scenario-based assessments

Genetic variability in the absorption of dietary sterols affects the risk of coronary artery disease

AIMS: To explore whether variability in dietary cholesterol and phytosterol absorption impacts the risk of coronary artery disease (CAD) using as instruments sequence variants in the ABCG5/8 genes, key regulators of intestinal absorption of dietary sterols. METHODS AND RESULTS: We examined the effects of ABCG5/8 variants on non-high-density lipoprotein (non-HDL) cholesterol (N up to 610 532) and phytosterol levels (N = 3039) and the risk of CAD in Iceland, Denmark, and the UK Biobank (105 490 cases and 844 025 controls). We used genetic scores for non-HDL cholesterol to determine whether ABCG5/8 variants confer greater risk of CAD than predicted by their effect on non-HDL cholesterol. We identified nine rare ABCG5/8 coding variants with substantial impact on non-HDL cholesterol. Carriers have elevated phytosterol levels and are at increased risk of CAD. Consistent with impact on ABCG5/8 transporter function in hepatocytes, eight rare ABCG5/8 variants associate with gallstones. A genetic score of ABCG5/8 variants predicting 1 mmol/L increase in non-HDL cholesterol associates with two-fold increase in CAD risk [odds ratio (OR) = 2.01, 95% confidence interval (CI) 1.75-2.31, P = 9.8 × 10-23] compared with a 54% increase in CAD risk (OR = 1.54, 95% CI 1.49-1.59, P = 1.1 × 10-154) associated with a score of other non-HDL cholesterol variants predicting the same increase in non-HDL cholesterol (P for difference in effects = 2.4 × 10-4). CONCLUSIONS: Genetic variation in cholesterol absorption affects levels of circulating non-HDL cholesterol and risk of CAD. Our results indicate that both dietary cholesterol and phytosterols contribute directly to atherogenesis

Flux limits on ultra high energy neutrinos with AMANDA-B10

Abstract Data taken during 1997 with the AMANDA-B10 detector are searched for a diffuse flux of neutrinos of all flavors with energies above 10 16 eV. At these energies the Earth is opaque to neutrinos, and thus neutrino induced events are concentrated at the horizon. The background are large muon bundles from down-going atmospheric air shower events. No excess events above the background expectation are observed and a neutrino flux following E À2 , with an equal mix of all flavors, is limited to E 2 U(10 15 eV < E < 3 · 10 18 eV) 6 0.99 · 10 À6 GeV cm À2 s À1 sr À1 at 90% confidence level. This is the most restrictive experimental bound placed by any neutrino detector at these energies. Bounds to specific extraterrestrial neutrino flux predictions are also presented. Ó 2004 Elsevier B.V. All rights reserved. PACS: 95.55.Vj; 95.85.Ry; 96.40.T

Magnetic resonance imaging as a tool to examine the neuropathology of multiple sclerosis

Magnetic resonance imaging (MRI) has significantly extended the understanding of multiple sclerosis (MS), owing to its ability to sensitively depict the dynamics of the disease process in vivo. The subject of this review is the use of MRI in the post-mortem setting, with emphasis on how it may be used to improve the specimen selection process at autopsy. Lesions with active demyelination are highly interesting in the study of MS pathogenesis, but are rare in a typical autopsy material of chronic MS. The yield of MS lesions in autopsy specimen selection can be increased by the use of MRI-guided tissue sampling, as a significant proportion of abnormalities detected by post-mortem MRI are not macroscopically visible/palpable. The majority of these MRI abnormalities have been found to represent either discrete areas of microglial activation with no demyelination (so-called (p)reactive lesions), or active demyelinating MS lesions by further histopathological examination. The presence and extent of MS pathology outside of the focal demyelinated lesions is more readily appreciated by MRI-guided specimen sampling, as has been shown in the study of extensive areas of partial myelin loss in the spinal cord. A further advantage of MRI-guided specimen sampling is the ability to use three-dimensional and quantitative measures. The potential of correlating these with histopathological data may be further exploited in the future. The technical procedure for MRI-guided tissue sampling at autopsy is presented, and the limitations of the technique are discussed

Spinal cord gray matter demyelination in multiple sclerosis-a novel pattern of residual plaque morphology.

The extent and pattern of gray matter (GM) demyelination in the spinal cord in multiple sclerosis (MS) has not been examined in detail. Human autopsy material was obtained from 36 MS cases and 12 controls. Transverse sections were taken from five levels of the spinal cord (upper cervical, lower cervical, upper thoracic, lower thoracic and lumbar levels) and the extent of GM and white matter (WM) demyelination evaluated using proteolipid protein immunohistochemistry (IHC). The proportion of the GM that was demyelinated (33%) was significantly greater than the proportion of demyelinated WM (20%) (P < 0.0001). Similarly, demyelination was more extensive in the GM than in the WM at each of the five cord levels. The extent of GM demyelination was not significantly different between the five cord levels while WM demyelination was greatest at the upper cervical level. Morphologically, the borders of a proportion of the GM plaques show a strict respect for the GM/WM boundary. We demonstrate that extensive demyelination occurs in the GM of the spinal cord in MS. Myelin protein IHC reveals a novel pattern of residual plaque morphology challenging previous work suggesting that MS plaques display a total disregard for anatomical boundaries

Grey matter pathology in multiple sclerosis

Although multiple sclerosis (MS) has been considered a white matter disease, MS lesions are known to occur in grey matter. Recent immunohistochemical studies have demonstrated extensive grey matter demyelination in chronic MS. The most common lesion type consists of purely cortical lesions extending inward from the surface of the brain, this lesion subgroup is grossly underestimated by standard histochemical myelin staining methods. Some MS patients have subpial demyelination in all cortical areas of the brain; this pattern has been termed ''general cortical subpial demyelination''. Extensive cortical demyelination is associated with the progressive phases of disease, as less cortical demyelination has been detected in relapsing-remitting MS. The pathology of grey matter lesions differs from that of white matter lesions; grey matter lesions are less inflammatory, with less macrophage and lymphocyte infiltration. In purely cortical lesions there is no significant increase in lymphocytes compared with non-demyelinated adjacent cortical areas in MS patients or cerebral cortex in control patients. Significant axonal transection and neuronal loss have been demonstrated in grey matter MS lesions. Current magnetic resonance imaging (MRI) methods are not sensitive for purely cortical MS lesions. The clinical significance of cortical MS lesions may not be characterised until more sensitive MRI methods are developed. © 2006 The Authors

Spinal cord atrophy in multiple sclerosis caused by white matter volume loss.

OBJECTIVE: To assess the relative contributions of white matter (WM) and gray matter (GM) volume loss to spinal cord atrophy in multiple sclerosis (MS). DESIGN: Postmortem study of transverse sections obtained from 5 levels of the spinal cord, with measurement of the cross-sectional GM and WM areas. SETTING: Department of Neuropathology, University of Nottingham, Nottingham, England. PATIENTS: Fifty-five MS cases and 33 controls. MAIN OUTCOME MEASURES: Size of the WM and GM areas. RESULTS: The WM area was significantly reduced in MS cases in the upper but not the lower cord levels. The GM area was not significantly different between MS and control cases. CONCLUSION: Spinal cord atrophy in MS is due to WM rather than GM volume loss