Stress-strain behavior and geometrical properties of packings of elongated particles

We present a numerical analysis of the effect of particle elongation on the quasistatic behavior of sheared granular media by means of the Contact Dynamics method. The particle shapes are rounded-cap rectangles characterized by their elongation. The macroscopic and microstructural properties of several packings subjected to biaxial compression are analyzed as a function of particle elongation. We find that the shear strength is an increasing linear function of elongation. Performing an additive decomposition of the stress tensor based on a harmonic approximation of the angular dependence of branch vectors, contact normals and forces, we show that the increasing mobilization of friction force and the associated anisotropy are key effects of particle elongation. These effects are correlated with partial nematic ordering of the particles which tend to be oriented perpendicular to the major principal stress direction and form side-to-side contacts. However, the force transmission is found to be mainly guided by cap-to-side contacts, which represent the largest fraction of contacts for the most elongated particles. Another interesting finding is that, in contrast to shear strength, the solid fraction first increases with particle elongation, but declines as the particles become more elongated. It is also remarkable that the coordination number does not follow this trend so that the packings of more elongated particles are looser but more strongly connected.Comment: Submited to Physical Review

Thrombolysis in acute myocardial infarction

The purpose of this study was to analyse the effects of thrombolytic therapy with intracoronary streptokinase in patients with acute myocardial infarction. Five centres participated in the study, the Thorax center in Rotterdam (237 patients), the Academic Hospital of the Free University of Amsterdam (93 patients), the Zuiderziekenhuis in Rotterdam (61 patients), the Academic Hospital of the University of Limburg in Maastricht (123 patients) and the Academic Hospital of Leiden (19 patients). The study was conducted by the Interuniversity Cardiology Institute the Netherlands. A strategy aimed at early reperfusion, including acute coronary angiography and intracoronary administration of streptokinase, was compared to conventional therapy of myocardial infarction without acute angiography and without administration of fibrinolytic therapy. Patients were eligible for the study if admitted to the hospital within four hours after onset of symptoms and with electrocardiographic signs typical for acute myocardial infarction. Patients over 70 years of age and patients with enhanced risks of bleeding were excluded. A total of 533 patients were included in the study of which 264 were randomly allocated to conventional treatment and 269 to thrombolytic therapy. Informed consent was sought from patients allocated to thrombolytic therapy only. Final patency of the infarct related artery was achieved with intracoronary streptokinase (usually 250,000 U) in 198 out of 234 patients (85% ). In 98 patients angiography was preceded by intravenous infusion of strep

Apparatus and method for reactive ion etching

The invention relates to an apparatus for reactive ion etching of a substrate, comprising: a plasma etch zone including an etch gas supply and arranged with a plasma generating structure for igniting a plasma and comprising an electrode structure arranged to accelerate the etch plasma toward a substrate portion to have ions impinge on the surface of the substrate; a passivation zone including a cavity provided with a passivation gas supply; said supply arranged for providing a passivation gas flow from the supply to the cavity; the cavity in use being bounded by the injector head and the substrate surface; and a gas purge structure comprising a gas exhaust arranged between said etch zone and passivation zone; the gas purge structure thus forming a spatial division of the etch and passivation zones

Automated detection of wedge-shaped defects in polarimetric images of the retinal nerve fibre layer

Purpose: Automated glaucoma detection in images obtained by scanning laser polarimetry is currently insensitive to local abnormalities, impairing its performance. The purpose of this investigation was to tes

The anisotropy of granular materials

The effect of the anisotropy on the elastoplastic response of two dimensional packed samples of polygons is investigated here, using molecular dynamics simulation. We show a correlation between fabric coefficients, characterizing the anisotropy of the granular skeleton, and the anisotropy of the elastic response. We also study the anisotropy induced by shearing on the subnetwork of the sliding contacts. This anisotropy provides an explanation to some features of the plastic deformation of granular media.Comment: Submitted to PR

Small portion sizes in worksite cafeterias: do they help consumers to reduce their food intake?

Background:Environmental interventions directed at portion size might help consumers to reduce their food intake.Objective:To assess whether offering a smaller hot meal, in addition to the existing size, stimulates people to replace their large meal with a smaller meal.Design:Longitudinal randomized controlled trial assessing the impact of introducing small portion sizes and pricing strategies on consumer choices.Setting/participants:In all, 25 worksite cafeterias and a panel consisting of 308 consumers (mean age39.18 years, 50% women).Intervention:A small portion size of hot meals was offered in addition to the existing size. The meals were either proportionally priced (that is, the price per gram was comparable regardless of the size) or value size pricing was employed.Main outcome measures:Daily sales of small and the total number of meals, consumers self-reported compensation behavior and frequency of purchasing small meals.Results:The ratio of small meals sales in relation to large meals sales was 10.2%. No effect of proportional pricing was found B0.11 (0.33), P0.74, confidence interval (CI): 0.76 to 0.54). The consumer data indicated that 19.5% of the participants who had selected a small meal often-to-always purchased more products than usual in the worksite cafeteria. Small meal purchases were negatively related to being male (B0.85 (0.20), P0.00, CI: 1.24 to 0.46, n178).Conclusion:When offering a small meal in addition to the existing size, a percentage of consumers that is considered reasonable were inclined to replace the large meal with the small meal. Proportional prices did not have an additional effect. The possible occurrence of compensation behavior is an issue that merits further attention. © 2011 Macmillan Publishers Limited All rights reserved

Klauwgezondheid bij varkens

Kreupelheid is één van de belangrijkste gezondheidsproblemen bij de huisvesting van zeugen in Nederland. Met name in groepshuisvesting komt dit tot uiting. Hierbij blijkt het vooral om klauwkreupelheden te gaan

Zeugen gezond houden in groepshuisvesting

Uit onderzoek naar gezondheidsproblemen bij zeugen die tijdens de dracht in groepshuisvesting worden gehouden, kwam als voornaamste probleem kreupelheid naar voren. Daarnaast komen ook huid- en vulvabeschadigingen regelmatig voor