Comparing tube models for predicting the linear rheology of branched polymer melts

The hierarchical and "bob" (or branch-on-branch) models are tube-based computational models recently developed for predicting the linear rheology of general mixtures of polydisperse branched polymers. These two models are based on a similar tube-theory framework but differ in their numerical implementation and details of relaxation mechanisms. We present a detailed overview of the similarities and differences of these models and examine the effects of these differences on the predictions of the linear viscoelastic properties of a set of representative branched polymer samples in order to give a general picture of the performance of these models. Our analysis confirms that the hierarchical and bob models quantitatively predict the linear rheology of a wide range of branched polymer melts but also indicate that there is still no unique solution to cover all types of branched polymers without case-by-case adjustment of parameters such as the dilution exponent alpha and the factor p(2) which defines the hopping distance of a branch point relative to the tube diameter. An updated version of the hierarchical model, which shows improved computational efficiency and refined relaxation mechanisms, is introduced and used in these analyses.

Data management for the ocean sciences - perspectives for the next decade

There is remarkable agreement in expectations today for vastly improved ocean data management a decade from now -- capabilities that will help to bring significant benefits to ocean research and to society. Advancing data management to such a degree, however, will require cultural and policy changes that are slow to effect. The technological foundations upon which data management systems are built are certain to continue advancing rapidly in parallel. These considerations argue for adopting attitudes of pragmatism and realism when planning data management strategies. In this paper we adopt those attitudes as we outline opportunities for progress in ocean data management. We begin with a synopsis of expectations for integrated ocean data management a decade from now. We discuss factors that should be considered by those evaluating candidate “standards”. We highlight challenges and opportunities in a number of technical areas, including “Web 2.0” applications, data modeling, data discovery and metadata, real-time operational data, archival of data, biological data management and satellite data management. We discuss the importance of investments in the development of software toolkits to accelerate progress. We conclude the paper by recommending a few specific, short term targets for implementation, that we believe to be both significant and achievable, and calling for action by community leadership to effect these advancements.

Ashanti

This was a theatre performance of the first English translation of Aszantka (Ashanti), written by Polish playwright Wlodzimierz Perzynski in 1906. Dr Teresa Murjas is the translator, designer and director. The performance took place in Bob Kayley Studio, University of Reading and at the Polish Theatre in Hammersmith, London.

Vermillion Vortex

An animated film commissioned and screened by Art Review Magazine on their website (Oct-Dec 2010), and a double page comic strip (Art Review, Oct 2010. The project addresses a key problem with contemporary debates regarding ideas of ‘performativity’ and ‘fictioning’ (Foucault/Deleuze/Butler) whereby the structural requirement for an ‘End’ pre-determines or back-codes the ‘story’ or progression of events leading up to this ‘End’ and therefore cuts against the potentials claimed for ‘performance’ and ‘performativity’. Film credits Primary soundtrack: Music: Rose Kallal. Spoken word: Mark Beasley Voices: Katie Barrington, Marnie Watts, Maria Deegan & John Russell Sound engineer: Bob Geal PLUS Special bonus track: (after 'The End'): 'Strychnine Motive' (2011) by Gum Takes Tooth

Evidence that ice forms primarily in supercooled liquid clouds at temperatures > -27C

Using 4 years of radar and lidar observations of layer clouds from the Chilbolton Observatory in the UK, we show that almost all (95%) ice particles formed at temperatures >-20°C appear to originate from supercooled liquid clouds. At colder temperatures, there is a monotonic decline in the fraction of liquid-topped ice clouds: 50% at -27°C, falling to zero at -37°C (where homogeneous freezing of water droplets occurs). This strongly suggests that deposition nucleation plays a relatively minor role in the initiation of ice in mid-level clouds. It also means that the initial growth of the ice particles occurs predominantly within a liquid cloud, a situation which promotes rapid production of precipitation via the Bergeron-Findeison mechanism.

Like the living end

Seven-part elegy for David Mather (1954-2010)

In vitro fermentation by human gut bacteria of proteolytically digested caseinomacropeptide nonenzymatically glycosylated with prebiotic carbohydrates

The in vitro fermentation selectivity of hydrolyzed caseinomacropeptide (CMP) glycosylated, via Maillard reaction (MR), with lactulose, galacto-oligosaccharides from lactose (GOSLa), and galacto-oligosaccharides from lactulose (GOSLu) was evaluated, using pH-controlled small-scale batch cultures at 37 °C under anaerobic conditions with human feces. After 10 and 24 h of fermentation, neoglyconjugates exerted a bifidogenic activity, similar to those of the corresponding prebiotic carbohydrates. No significant differences were found in Bacteroides, Lactobacillus�Enterococcus, Clostridium histolyticum subgroup, Atopobium and Clostridium coccoides�Eubacterium rectale populations. Concentrations of lactic acid and short-chain fatty acids (SCFA) produced during the fermentation of prebiotic carbohydrates were similar to those produced for their respective neoglycoconjugates at both fermentation times. These findings, joined with the functional properties attributed to CMP, could open up new applications of MR products involving prebiotics as novel multiple-functional ingredients with potential beneficial effects on human health.

In vitro fermentation of alternansucrase raffinose-derived oligosaccharides by human gut bacteria

In this work, in vitro fermentation of alternansucrase raffinose-derived oligosaccharides, previously fractionated according to their degree of polymerization (DP; from DP4 to DP10), was carried out using small-scale pH-controlled batch cultures at 37 °C under anaerobic conditions with human feces. Bifidogenic activity of oligosaccharides with DP4�6 similar to that of lactulose was observed; however, in general, a significant growth of lactic acid bacteria Bacteroides, Atopobium cluster, and Clostridium histolyticum group was not shown during incubation. Acetic acid was the main short chain fatty acid (SCFA) produced during the fermentation process; the highest levels of this acid were shown by alternansucrase raffinose acceptor pentasaccharides at 10 h (63.11 mM) and heptasaccharides at 24 h (54.71 mM). No significant differences between the gas volume produced by the mixture of raffinose-based oligosaccharides (DP5�DP10) and inulin after 24 h of incubation were detected, whereas lower gas volume was generated by DP4 oligosaccharides. These findings indicate that novel raffinose-derived oligosaccharides (DP4�DP10) could be a new source of prebiotic carbohydrates.

Microbial utilization and selectivity of pectin fractions with various structures

To evaluate the fermentation properties of oligosaccharides derived from pectins and their parent polysaccharides, a 5-ml-working-volume, pH- and temperature-controlled fermentor was tested. Six pectic oligosaccharides representing specific substructures found within pectins were prepared. These consisted of oligogalacturonides (average degrees of polymerization [DP] of 5 and 9), methylated oligogalacturonides (average DP of 5), oligorhamnogalacturonides (average DP of 10 as a disaccharide unit of galacturonic acid and rhamnose), oligogalactosides (average DP of 5), and oligoarabinosides (average DP of 6). The influence of these carbohydrates on the human fecal microbiota was evaluated. Use of neutral sugar fractions resulted in an increase in Bifidobacterium populations and gave higher organic acid yields. The Bacteroides-Prevotella group significantly increased on all oligosaccharides except oligogalacturonides with an average DP of 5. The most selective substrates for bifidobacteria were arabinan, galactan, oligoarabinosides, and oligogalactosides.

Effect of dextransucrase cellobiose acceptor products on the growth of human gut bacteria

The selective fermentation by human gut bacteria of gluco-oligosaccharides obtained from the reaction between the glucosyl group of sucrose and cellobiose, catalyzed by dextransucrases (DSR) from Leuconostoc mesenteroides, has been evaluated. Oligosaccharides were fractionated according to their molecular weight, and their effect on the growth of different bacterial groups was studied. To determine the structure (position and configuration of glycosidic linkages)�function relationship, their properties were compared to those of DSR maltose acceptor products (DSRMal) and of recognized prebiotic carbohydrates (fructo-oligosaccharides, FOS). Cellobiose acceptor products (DSRCel) showed bifidogenic properties similar to those of FOS. However, no significant differences related to molecular weight or isomeric configurations were found for DSRCel and DSRMal products.

Functional oligosaccharides: application and manufacture.

Oligosaccharides are attracting increasing interest as prebiotic functional food ingredients. They can be extracted or obtained by enzymatic hydrolysis from a variety of biomass sources or synthesized from simple oligosaccharides by enzymatic transfer reactions. The major prebiotic oligosaccharides on the market are inulin, fructo-oligosaccharides, and galacto-oligosaccharides. They have been evaluated using a range of in vitro and in vivo methods, although there is a need for more large-scale human trials using modern microbiological methods. Prebiotics are being studied for their effects on gut health and well being and specific clinical conditions, including colon cancer, inflammatory bowel disease (IBD), acute infections, and mineral absorption. Developing understanding of the functional ecology of the human gut is influencing current thinking on what a prebiotic might achieve and is providing new targets for prebiotic intervention.

Oligosaccharides of pitaya (dragon fruit) flesh and their prebiotic properties

The major carbohydrates of white and red-flesh pitayas (dragon fruit) were glucose, fructose and some oligosaccharides (total concentrations of 86.2 and 89.6 g/kg, respectively). The molecular weight distribution of the extract was affected by the extraction solvent. The maximum oligosaccharides content (27.40%), which included fractions with molecular weights of 273–275, 448–500 and 787–911 Da, were obtained using 80% ethanol extraction at room temperature (28 ± 2 °C). The low molecular weight fraction, including glucose and fructose, was successfully removed by yeast cultivation. The molecular weights of mixed oligosaccharides (716, 700, 490 and 474 Da) were confirmed by mass spectrometry. The mixed oligosaccharides showed that they were resistant to hydrolysis by artificial human gastric juice and human α-amylase, giving maximum hydrolysis of 4.04% and 34.88%, respectively. The mixed oligosaccharides were also found capable of stimulating the growth of lactobacilli and bifidobacteria.

Working Group 1: Future developments in deterministic and stochastic parametrizations

Our group considered the desirability of including representations of uncertainty in the development of parameterizations. (By ‘uncertainty’ here we mean the deviation of sub-grid scale fluxes or tendencies in any given model grid box from truth.) We unanimously agreed that the ECWMF should attempt to provide a more physical basis for uncertainty estimates than the very effective but ad hoc methods being used at present. Our discussions identified several issues that will arise.