Tracking lubricants during single screw extrusion of uPVC

CITATION: Barnard, J. L., Robertson, D. D. & Van Reenen, A. J. 2020. Tracking lubricants during single screw extrusion of uPVC. Polymer Testing, 87:106523, doi:10.1016/j.polymertesting.2020.106523.The original publication is available at https://www.sciencedirect.comLubrication is one of the most important parameters in unplasticized polyvinyl chloride (uPVC) processing apart from the PVC resin and processing equipment. Lubricants are used in specific ratios to ensure effective fusion of PVC particles. The exact mechanism on how these lubricants interact is not yet fully understood. A widely accepted theory is the interaction mechanism proposed by Rabinovic et al. where lubricants are said to act as surfactants and slip agents. In this study a method for tracking lubricants, by simulating the extrusion process within a single screw extruder, was proposed. A three stage fusion simulation consisted of the feeding zone (stage 1), the compression zone (stage 2) and the metering zone (stage 3). The association interactions between the individual components of a typical uPVC formulation were followed throughout the three stages. External polar and nonpolar lubricants in combination with an internal lubricant was studied. Lubricants were successfully tracked using scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS). In conclusion it was found that the use of an internal lubricant promotes dispersion of external lubrication towards PVC. It was also found that there is a competition between the internal lubricant and polar external lubricant.Publisher's versio

Optimized production of bacteriocin ST11BR, generated by Lactobacillus paracasei subsp. paracasei ST11BR isolated from traditional South African beer

CITATION: Todorov, S. D., Van Reenen, C. A. & Dicks, L. M. T. 2005. Optimized production of bacteriocin ST11BR, generated by Lactobacillus paracasei subsp. paracasei ST11BR isolated from traditional South African beer. South African Journal of Science, 101(3-4):182-186 .The original publication is available at https://journals.co.zaLittle is known about the production of antimicrobial peptides (bacteriocins) by lactic acid bacteria in traditional South African beer and their inhibition of food spoilage or pathogenic bacteria. In this paper, we report on bacteriocin ST11BR, produced by Lactobacillus paracasei subsp. paracasei ST11BR isolated from beer made with maize, barley, soy flour and sugar (sucrose). Bacteriocin ST11BR is a 3.2-kDa peptide with activity against Lactobacillus casei, L. sakei, Pseudomonas aeruginosa and Escherichia coli. The peptide is sensitive to proteinase K and pronase, but not to α-amylase. Glycerol in the growth medium repressed bacteriocin production. Tween 80 suppressed production by more than 50%, irrespective of the initial pH of the medium. MRS broth adjusted to pH 4.50 yielded 3200 AU/ml bacteriocin. The corresponding value at pH 5.0, 5.5, 6.0 and 6.5 was 12 800 AU/ml. The highest yield (25 600 AU/ml) was recorded in MRS broth without Tween 80, and with meat extract as the only nitrogen source, or a combination of meat extract and tryptone, or yeast extract and tryptone. Growth in the presence of tryptone as sole nitrogen source achieved only 12 800 AU/ml bacteriocin. Yeast extract, or a combination of yeast extract and meat extract, yielded 6400 AU/ml. A growth medium comprising 20.0 g/l maltose, sucrose or mannose yielded bacteriocin levels of 25 600 AU/ml, whereas the corresponding values for the same concentration of glucose or fructose were 12 800 AU/ml and 1 600 AU/ml, respectively. Lactose did not stimulate bacteriocin production - the highest yield (6 400 AU/ml) was generated in the presence of 10.0 g/l. No difference in bacteriocin activity was recorded when strain ST11BR was grown in the presence of 2.0 g/l KH2PO4 and 2.0-10.0 g/l K2HPO 4. However, cyanocobalamin, thiamine and DL-6,8-thioctic acid (1.0 ppm), but not L-ascorbic acid, stimulated peptide production. This study provided valuable information on the optimal production of bacteriocin by a strain of L. paracasei naturally present in a traditional beer.https://journals.co.za/content/sajsci/101/3-4/EJC96371Publisher's versio

Phenotypic and genetic heterogeneity of lactic acid bacteria isolated from “Alheira”, a traditional fermented sausage produced in Portugal

The aim of this study was to evaluate the phenotypic and genetic heterogeneity of lactic acid bacteria (LAB) isolated from ‘‘alheira”, a fermented sausage produced in Portugal. LAB were identified to genus and species level by phenotypic characteristics, using genus or speciesspecific primers and sequencing of the gene encoding 16S rRNA. Two-hundred and eighty-three isolates were grouped into 14 species. Lactobacillus plantarum was isolated from all sausages and Enterococcus faecalis from most of the samples. Low numbers of Lactobacillus paraplantarum, Lactobacillus brevis, Lactobacillus rhamnosus, Lactobacillus sakei, Lactobacillus zeae, Lactobacillus paracasei, Leuconostoc mesenteroides, Pediococcus pentosaceus, Pediococcus acidilactici, Weissella cibaria, Weissella viridescens and Enterococcus faecium were recorded. The genetic heterogeneity of L. plantarum and E. faecalis strains were determined by numerical analysis of DNA banding patterns obtained by RAPD–PCR. Strains of L. plantarum and E. faecalis were different from different producers. This study forms the basis from which starter cultures could be selected for production of ‘‘Alheira”.info:eu-repo/semantics/acceptedVersio

Maintaining the Strength of American Capitalism

The American economic system has always been the foundation of our national strength. But this foundation is showing cracks—from high levels of income inequality, declining economic mobility, and persistent economic insecurity among low- and middle-income Americans.Many now conclude that our economic system is broken. Recent polling data show that trust in capitalism is declining, especially among younger people. A 2018 Gallup poll found that less than half of respondents (45%) ages 18-29 held positive views of capitalism. This shift represents a 20-point decline since 2010 in the share of young adults' who held positive views of capitalism.The upshot is clear: American capitalism is in trouble. We need to strengthen our system to ensure that more people participate in our economic success. This means updating and adjusting our policies to ensure the outcomes of our market-based economy are consistent with fundamental American values of freedom, opportunity, and equality.Doing so isn't just an imperative for economic reasons. We believe that strengthening capitalism is as important for the health of the American economy as it is for the strength of our democracy. High levels of economic inequality will only contribute to increasing political dysfunction.The essays contained in this volume seek to clarify the lines of debate on some of the greatest economic policy challenges of our time and present evidence- based analysis on how to address them. It examines the hypothesis that growing market concentration is inhibiting a dynamic and competitive economy. Next, it examines the health of America's fiscal situation and what it implies about the continued strength of our market-based economy. Finally, it takes a hard look at recent policy proposals that would dramatically raise taxes on the rich and expand access to public benefit programs in response to high levels of income inequality and declining economic mobility.The perspectives presented in this volume are not intended to represent the consensus view of Aspen Economic Strategy Group members. Our goal is to equip policymakers with the best analysis available to better inform decision making and to help Americans better understand the difficult trade-offs our leaders face in making such decisions.There is no single solution to the challenges facing the American economy. The important role of evidence-based policies with bipartisan appeal, however, is difficult to overstate. This volume cannot claim to represent the end of thinking on ways to strengthen American capitalism, but we believe it provides a useful start

A model for the dynamics and internal structure of planar doping fronts in organic semiconductors

The dynamics and internal structure of doping fronts in organic semiconductors are investigated theoretically using an extended drift-diffusion model for ions, electrons and holes. The model also involves the injection barriers for electrons and holes in the partially doped regions in the form of the Nernst equation, together with a strong dependence of the electron and hole mobility on concentrations. Closed expressions for the front velocities and the ion concentrations in the doped regions are obtained. The analytical theory is employed to describe the acceleration of the p- and n-fronts towards each other. The analytical results show very good agreement with the experimental data. Furthermore, it is shown that the internal structure of the doping fronts is determined by the diffusion and mobility processes. The asymptotic behavior of the concentrations and the electric field is studied analytically inside the doping fronts. The numerical solution for the front structure confirms the most important predictions of the analytical theory: a sharp head of the front in the undoped region, a smooth relaxation tail in the doped region, and a plateau at the critical point of transition from doped to undoped regions.Comment: 13 pages, 11 figure

Dairy calves' personality traits predict social proximity and response to an emotional challenge

Abstract The assessment of individual traits requires that tests are reliable (i.e. consistency over time) and externally valid, meaning that they predict future responses in similar contexts (i.e. convergent validity) but do not predict responses to unrelated situations (i.e. discriminant validity). The aim of this study was to determine if dairy calf personality traits (Fearfulness, Sociability and Pessimism), derived from behaviours expressed in standardized tests, predict individuals’ responses in related situations. The first experiment tested if the trait ‘Sociability’ was related to the expression of social behaviour in the home-pen, with calves assigned individual proximity scores (based on proximity to other calves) while they were in their home-pen at approximately 113 and 118 d of age. The second experiment aimed at exploring whether traits ‘Fearfulness’ and ‘Pessimism’ were related to the calves’ emotional response to transportation. All calves were subjected to two 10-min transportation challenges done on two consecutive days. Emotional response was assessed using the maximum eye temperature (measured using infrared thermography) and the number of vocalizations emitted. Social proximity scores (Experiment 1), vocalizations emitted and maximum eye temperature after loading (Experiment 2) were consistent over time. In addition, the results showed good convergent validity with calves scoring higher in Sociability also having higher proximity scores in the home-pen, and animals scoring higher in Fearfulness and Pessimism showing a more intense emotional response to transportation. The results also showed good discriminant validity, as neither Fearfulness nor Pessimism were associated with the expression of social behaviours (Experiment 1) and Sociability was not associated with the animal’s emotional response to transportation (Experiment 2). We conclude that the methodology used to measure personality traits shows good reliability and external validity

Protein kinase C-delta (PKC delta), a marker of inflammation and tuberculosis disease progression in humans, is important for optimal macrophage killing effector functions and survival in mice (vol 11, pg 496, 2018)

We previously demonstrated that protein kinase C-δ (PKCδ) is critical for immunity against Listeria monocytogenes, Leishmania major, and Candida albicans infection in mice. However, the functional relevance of PKCδ during Mycobacterium tuberculosis (Mtb) infection is unknown. PKCδ was significantly upregulated in whole blood of patients with active tuberculosis (TB) disease. Lung proteomics further revealed that PKCδ was highly abundant in the necrotic and cavitory regions of TB granulomas in multidrug-resistant human participants. In murine Mtb infection studies, PKCδ−/− mice were highly susceptible to tuberculosis with increased mortality, weight loss, exacerbated lung pathology, uncontrolled proinflammatory cytokine responses, and increased mycobacterial burdens. Moreover, these mice displayed a significant reduction in alveolar macrophages, dendritic cells, and decreased accumulation of lipid bodies (lungs and macrophages) and serum fatty acids. Furthermore, a peptide inhibitor of PKCδ in wild-type mice mirrored lung inflammation identical to infected PKCδ−/− mice. Mechanistically, increased bacterial growth in macrophages from PKCδ−/− mice was associated with a decline in killing effector functions independent of phagosome maturation and autophagy. Taken together, these data suggest that PKCδ is a marker of inflammation during active TB disease in humans and required for optimal macrophage killing effector functions and host protection during Mtb infection in mice