A copolymer analysis approach to estimate the neutral sugar distribution of sugar beet pectin using size exclusion chromatography

Partially degraded sugar beet (Beta vulgaris) pectins were characterised in terms of galacturonic acid, neutral sugar and ferulic acids contents. It was shown that the total neutral sugar content is correlated with the ferulic acid content. One pectin (C) was further characterised by size exclusion chromatography coupled to refractive index and UV detectors (SEC-RI-UV). This gave the opportunity to estimate how the ferulic acid and neutral sugar contents changed with hydrodynamic radius. Pectin C was found to be heterogeneous in composition with neutral sugar-rich fractions of both high and low hydrodynamic radii. A neutral sugar-poor fraction was found at intermediate hydrodynamic radii

Mean flow and spiral defect chaos in Rayleigh-Benard convection

We describe a numerical procedure to construct a modified velocity field that does not have any mean flow. Using this procedure, we present two results. Firstly, we show that, in the absence of mean flow, spiral defect chaos collapses to a stationary pattern comprising textures of stripes with angular bends. The quenched patterns are characterized by mean wavenumbers that approach those uniquely selected by focus-type singularities, which, in the absence of mean flow, lie at the zig-zag instability boundary. The quenched patterns also have larger correlation lengths and are comprised of rolls with less curvature. Secondly, we describe how mean flow can contribute to the commonly observed phenomenon of rolls terminating perpendicularly into lateral walls. We show that, in the absence of mean flow, rolls begin to terminate into lateral walls at an oblique angle. This obliqueness increases with Rayleigh number.Comment: 14 pages, 19 figure

A single model of traversable wormholes supported by generalized phantom energy or Chaplygin gas

This paper discusses a new variable equation of state parameter leading to exact solutions of the Einstein field equations describing traversable wormholes. In addition to generalizing the notion of phantom energy, the equation of state generates a mathematical model that combines the generalized phantom energy and the generalized Chaplygin gas models.Comment: 6 pages, no figure

Cross-Newell equations for hexagons and triangles

The Cross-Newell equations for hexagons and triangles are derived for general real gradient systems, and are found to be in flux-divergence form. Specific examples of complex governing equations that give rise to hexagons and triangles and which have Lyapunov functionals are also considered, and explicit forms of the Cross-Newell equations are found in these cases. The general nongradient case is also discussed; in contrast with the gradient case, the equations are not flux-divergent. In all cases, the phase stability boundaries and modes of instability for general distorted hexagons and triangles can be recovered from the Cross-Newell equations.Comment: 24 pages, 1 figur

Pattern Formation and Dynamics in Rayleigh-B\'{e}nard Convection: Numerical Simulations of Experimentally Realistic Geometries

Rayleigh-B\'{e}nard convection is studied and quantitative comparisons are made, where possible, between theory and experiment by performing numerical simulations of the Boussinesq equations for a variety of experimentally realistic situations. Rectangular and cylindrical geometries of varying aspect ratios for experimental boundary conditions, including fins and spatial ramps in plate separation, are examined with particular attention paid to the role of the mean flow. A small cylindrical convection layer bounded laterally either by a rigid wall, fin, or a ramp is investigated and our results suggest that the mean flow plays an important role in the observed wavenumber. Analytical results are developed quantifying the mean flow sources, generated by amplitude gradients, and its effect on the pattern wavenumber for a large-aspect-ratio cylinder with a ramped boundary. Numerical results are found to agree well with these analytical predictions. We gain further insight into the role of mean flow in pattern dynamics by employing a novel method of quenching the mean flow numerically. Simulations of a spiral defect chaos state where the mean flow is suddenly quenched is found to remove the time dependence, increase the wavenumber and make the pattern more angular in nature.Comment: 9 pages, 10 figure

Time of admission to the PICU and mortality

Objectives: To evaluate for any association between time of admission to the PICU and mortality. Design: Retrospective cohort study of admissions to PICUs in the Virtual Pediatric Systems (VPS, LLC, Los Angeles, CA) database from 2009 to 2014. Setting: One hundred and twenty-nine PICUs in the United States. Patients: Patients less than 18 years old admitted to participating PICUs; excluding those post cardiac bypass. Interventions: None. Measurements and Main Results: A total of 391,779 admissions were included with an observed PICU mortality of 2.31%. Overall mortality was highest for patients admitted from 07:00 to 07:59 (3.32%) and lowest for patients admitted from 14:00 to 14:59 (1.99%). The highest mortality on weekdays occurred for admissions from 08:00 to 08:59 (3.30%) and on weekends for admissions from 09:00 to 09:59 (4.66%). In multivariable regression, admission during the morning 06:00-09:59 and midday 10:00-13:59 were independently associated with PICU death when compared with the afternoon time period 14:00-17:59 (morning odds ratio, 1.15; 95% CI, 1.04-1.26; p = 0.006 and midday odds ratio, 1.09; 95% CI; 1.01-1.18; p = 0.03). When separated into weekday versus weekend admissions, only morning admissions were associated with increased odds of death on weekdays (odds ratio, 1.13; 95% CI, 1.01-1.27; p = 0.03), whereas weekend admissions during the morning (odds ratio, 1.33; 95% CI, 1.14-1.55; p = 0.004), midday (odds ratio, 1.27; 95% CI, 1.11-1.45; p = 0.0006), and afternoon (odds ratio, 1.17; 95% CI, 1.03-1.32; p = 0.01) were associated with increased risk of death when compared with weekday afternoons. Conclusions: Admission to the PICU during the morning period from 06:00 to 09:59 on weekdays and admission throughout the day on weekends (06:00-17:59) were independently associated with PICU death as compared to admission during weekday afternoons. Potential contributing factors deserving further study include handoffs of care, rounds, delays related to resource availability, or unrecognized patient deterioration prior to transfer

Efficient Algorithm on a Non-staggered Mesh for Simulating Rayleigh-Benard Convection in a Box

An efficient semi-implicit second-order-accurate finite-difference method is described for studying incompressible Rayleigh-Benard convection in a box, with sidewalls that are periodic, thermally insulated, or thermally conducting. Operator-splitting and a projection method reduce the algorithm at each time step to the solution of four Helmholtz equations and one Poisson equation, and these are are solved by fast direct methods. The method is numerically stable even though all field values are placed on a single non-staggered mesh commensurate with the boundaries. The efficiency and accuracy of the method are characterized for several representative convection problems.Comment: REVTeX, 30 pages, 5 figure

Global modeling of the nitrate radical (NO3) for present and pre-industrial scenarios

AbstractIncreasing the complexity of the chemistry scheme in the global chemistry transport model STOCHEM to STOCHEM-CRI (Utembe et al., 2010) leads to an increase in NOx as well as ozone resulting in higher NO3 production over forested regions and regions impacted by anthropogenic emission. Peak NO3 is located over the continents near NOx emission sources. NO3 is formed in the main by the reaction of NO2 with O3, and the significant losses of NO3 are due to the photolysis and the reactions with NO and VOCs. Isoprene is an important biogenic VOC, and the possibility of HOx recycling via isoprene chemistry and other mechanisms such as the reaction of RO2 with HO2 has been investigated previously (Archibald et al., 2010a). The importance of including HOx recycling processes on the global budget of NO3 for present and pre-industrial scenarios has been studied using STOCHEM-CRI, and the results are compared. The large increase (up to 60% for present and up to 80% for pre-industrial) in NO3 is driven by the reduced lifetime of emitted VOCs because of the increase in the HOx concentration. The maximum concentration changes (up to 15ppt) for NO3 from pre-industrial to present day are found at the surface between 30oN and 60oN because of the increase in NOx concentrations in the present day integrations

Amphipathic polymer-mediated uptake of trehalose for dimethyl sulfoxide-free human cell cryopreservation

For stem cell therapy to become a routine reality, one of the major challenges to overcome is their storage and transportation. Currently this is achieved by cryopreserving cells utilising the cryoprotectant dimethyl sulfoxide (MeSO). MeSO is toxic to cells, leads to loss of cell functionality, and can produce severe side effects in patients. Potentially, cells could be frozen using the cryoprotectant trehalose if it could be delivered into the cells at a sufficient concentration. The novel amphipathic membrane permeabilising agent PP-50 has previously been shown to enhance trehalose uptake by erythrocytes, resulting in increased cryosurvival. Here, this work was extended to the nucleated human cell line SAOS-2. Using the optimum PP-50 concentration and media osmolarity, cell viability post-thaw was 60±2%. In addition, the number of metabolically active cells 24h post-thaw, normalised to that before freezing, was found to be between 103±4% and 91±5%. This was found to be comparable to cells frozen using MeSO. Although reduced (by 22±2%, p=0.09), the doubling time was found not to be statistically different to the non-frozen control. This was in contrast to cells frozen using MeSO, where the doubling time was significantly reduced (by 41±4%, p=0.004). PP-50 mediated trehalose delivery into cells could represent an alternative cryopreservation protocol, suitable for research and therapeutic applications. © 2013 The Authors