Structure and Rheology of the Defect-gel States of Pure and Particle-dispersed Lyotropic Lamellar Phases

We present important new results from light-microscopy and rheometry on a moderately concentrated lyotropic smectic, with and without particulate additives. Shear-treatment aligns the phase rapidly, except for a striking network of oily-streak defects, which anneals out much more slowly. If spherical particles several microns in diameter are dispersed in the lamellar medium, part of the defect network persists under shear-treatment, its nodes anchored on the particles. The sample as prepared has substantial storage and loss moduli, both of which decrease steadily under shear-treatment. Adding particles enhances the moduli and retards their decay under shear. The data for the frequency-dependent storage modulus after various durations of shear-treatment can be scaled to collapse onto a single curve. The elasticity and dissipation in these samples thus arises mainly from the defect network, not directly from the smectic elasticity and hydrodynamics.Comment: 19 pages inclusive of 12 PostScript figures, uses revtex, psfrag and epsfig. Revised version, accepted for publication in Euro. Phys. J. B, with improved images of defect structure and theoretical estimates of network elasticity and scalin

Theory of Suspension Segregation in Partially Filled Horizontal Rotating Cylinders

It is shown that a suspension of particles in a partially-filled, horizontal, rotating cylinder is linearly unstable towards axial segregation and an undulation of the free surface at large enough particle concentrations. Relying on the shear-induced diffusion of particles, concentration-dependent viscosity, and the existence of a free surface, our theory provides an explanation of the experiments of Tirumkudulu et al., Phys. Fluids 11, 507-509 (1999); ibid. 12, 1615 (2000).Comment: Accepted for publication in Phys Fluids (Lett) 10 pages, two eps figure

Variable Selection and Model Averaging in Semiparametric Overdispersed Generalized Linear Models

We express the mean and variance terms in a double exponential regression model as additive functions of the predictors and use Bayesian variable selection to determine which predictors enter the model, and whether they enter linearly or flexibly. When the variance term is null we obtain a generalized additive model, which becomes a generalized linear model if the predictors enter the mean linearly. The model is estimated using Markov chain Monte Carlo simulation and the methodology is illustrated using real and simulated data sets.Comment: 8 graphs 35 page

Pregnancy outcomes in asylum seekers in the North of the Netherlands:a retrospective documentary analysis

BACKGROUND: With more than 20,000 asylum seekers arriving every year, healthcare for this population has become an important issue. Pregnant asylum seekers seem to be at risk of poor pregnancy outcomes. This study aimed to assess the difference in pregnancy outcomes between asylum seekers and the local Dutch population and to identify potential substandard factors of care. METHODS: Using a retrospective study design we compared pregnancy outcomes of asylum-seeking and Dutch women who gave birth in a northern region of the Netherlands between January 2012 and December 2016. The following data were compared: perinatal mortality, maternal mortality, gestational age at delivery, preterm delivery, birth weight, small for gestational age children, APGAR score, intrauterine foetal death, mode of delivery and the need for pain medication. Cases of perinatal mortality in asylum seekers were reviewed for potential substandard factors. RESULTS: A total of 344 Asylum-seeking women and 2323 Dutch women were included. Asylum seekers had a higher rate of perinatal mortality (3.2% vs. 0.6%, p = 0.000) including a higher rate of intrauterine foetal death (2.3% vs. 0.2%, p = 0.000), higher gestational age at birth (39 + 4 vs. 38 + 6 weeks, p = 0.000), labour was less often induced (36.9 vs. 43.8, p = 0.016), postnatal hospitalization was longer (2.24 vs. 1.72 days p = 0.006) and they received more opioid analgesics (27.3% vs. 22%, p = 0.029). Babies born from asylum-seeking women had lower birth weights (3265 vs. 3385 g, p = 0.000) and were more often small for gestational age (13.9% vs. 8.4%, p = 0.002). Multivariate analysis showed that the increased risk of perinatal mortality in asylum-seeking women was independent of parity, birth weight and gestational age at birth. Review of the perinatal mortality cases in asylum seekers revealed possible substandard factors, such as late initiation of antenatal care, missed appointments because of transportation problems, not recognising alarm symptoms, not knowing who to contact and transfer to other locations during pregnancy. CONCLUSION: Pregnant asylum seekers have an increased risk of adverse pregnancy outcomes. More research is needed to identify which specific risk factors are involved in poor perinatal outcomes in asylum seekers and to identify strategies to improve perinatal care for this group of vulnerable women

A Novel Method of Determining Portal Systemic Shunting using Biodegradable 99TCm Labelled Albumin Microspheres

Portal systemic shunting (PSS) and portal pressure were measured in control rats and in animals with portal hypertension induced by partial portal vein ligation (PPVL). The portal pressure in rats with partial portal vein ligation (13.4 ± 0.5 mm.Hg.) was significantly higher (p < 0.005) than in the control group (9.6 ± 0.6 mm.Hg.). Portal systemic shunting measured by consecutive injections of radiolabelled methylene diphosphonate (MDP), a non-diffusable marker and albumin microspheres directly into the splenic pulp was significantly increased (P < 0.005) in the portal hypertensive animals (30.8 ± 2.5%) compared to sham operated rats (2.6 ± 1.5%). Similarly, in portal hypertensive rats portal systemic shunting measured by intrasplenic injections of radiolabelled cobalt microspheres (37.1 ± 3.9%) was significantly greater (p < 0.005) than in control animals. There was a good correlation and agreement (r = 00.97) between the two methods of measuring portal systemic shunting. However because the 99Tcm-albumin microspheres are biodegradable the method allows portal systemic shunting to be measured in man. Furthermore since the computer adjusts the baseline to zero after each determination of portal systemic shunting the methodology allows repeated measurements to be made

First normal stress difference and crystallization in a dense sheared granular fluid

The first normal stress difference (${\mathcal N}_1$) and the microstructure in a dense sheared granular fluid of smooth inelastic hard-disks are probed using event-driven simulations. While the anisotropy in the second moment of fluctuation velocity, which is a Burnett-order effect, is known to be the progenitor of normal stress differences in {\it dilute} granular fluids, we show here that the collisional anisotropies are responsible for the normal stress behaviour in the {\it dense} limit. As in the elastic hard-sphere fluids, ${\mathcal N}_1$ remains {\it positive} (if the stress is defined in the {\it compressive} sense) for dilute and moderately dense flows, but becomes {\it negative} above a critical density, depending on the restitution coefficient. This sign-reversal of ${\mathcal N}_1$ occurs due to the {\it microstructural} reorganization of the particles, which can be correlated with a preferred value of the {\it average} collision angle $\theta_{av}=\pi/4 \pm \pi/2$ in the direction opposing the shear. We also report on the shear-induced {\it crystal}-formation, signalling the onset of fluid-solid coexistence in dense granular fluids. Different approaches to take into account the normal stress differences are discussed in the framework of the relaxation-type rheological models.Comment: 21 pages, 13 figure

Intra- and inter-individual genetic differences in gene expression

Genetic variation is known to influence the amount of mRNA produced by a gene. Given that the molecular machines control mRNA levels of multiple genes, we expect genetic variation in the components of these machines would influence multiple genes in a similar fashion. In this study we show that this assumption is correct by using correlation of mRNA levels measured independently in the brain, kidney or liver of multiple, genetically typed, mice strains to detect shared genetic influences. These correlating groups of genes (CGG) have collective properties that account for 40-90% of the variability of their constituent genes and in some cases, but not all, contain genes encoding functionally related proteins. Critically, we show that the genetic influences are essentially tissue specific and consequently the same genetic variations in the one animal may up-regulate a CGG in one tissue but down-regulate the same CGG in a second tissue. We further show similarly paradoxical behaviour of CGGs within the same tissues of different individuals. The implication of this study is that this class of genetic variation can result in complex inter- and intra-individual and tissue differences and that this will create substantial challenges to the investigation of phenotypic outcomes, particularly in humans where multiple tissues are not readily available.&#xd;&#xa;&#xd;&#xa