2,461 research outputs found

    Analysis of Modified Starch Adsorption Kinetics on Cellulose Fibers via the Modified Langmuir Adsorption Theory

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    The kinetics of starch adsorption on cellulose fibers is one of the most important criteria regarding the efficient application of papermaking additives due to the continuous nature of paper production and the concomitant need to determine optimum residence times. This study presents an analysis of the kinetics of modified starch adsorption onto cellulose fibers via the application of the modified Langmuir adsorption theory (i.e. the collision theory). A model based on this theory was used to describe the kinetics of starch binding, and to obtain the adsorption rate constant under different process conditions, which closely correspond to the conditions commonly encountered in industrial production of paper and board. The model predictions were then correlated with the experimental data. The adsorption of modified starch was found to increase by increasing the fiber consistency, shear forces (via stirring frequency) and the refining degree of fibers. The results also demonstrate that, at least in the studied range of process variables, the modified Langmuir adsorption theory can be applied to describe the adsorption kinetics of modified starch on cellulose fibers

    Antimicrobial Resistance and Virulence Genes in Enterococcus faecium and Enterococcus faecalis from Humans and Retail Red Meat

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    The emergence of antimicrobial-resistant and virulent enterococci is a major public health concern. While enterococci are commonly found in food of animal origin, the knowledge on their zoonotic potential is limited. The aim of this study was to determine and compare the antimicrobial susceptibility and virulence traits of Enterococcus faecalis and Enterococcus faecium isolates from human clinical specimens and retail red meat in Slovenia. A total of 242 isolates were investigated: 101 from humans (71 E. faecalis, 30 E. faecium) and 141 from fresh beef and pork (120 E. faecalis, 21 E. faecium). The susceptibility to 12 antimicrobials was tested using a broth microdilution method, and the presence of seven common virulence genes was investigated using PCR. In both species, the distribution of several resistance phenotypes and virulence genes was disparate for isolates of different origin. All isolates were susceptible to daptomycin, linezolid, teicoplanin, and vancomycin. In both species, the susceptibility to antimicrobials was strongly associated with a food origin and the multidrug resistance, observed in 29.6% of E. faecalis and 73.3% E. faecium clinical isolates, with a clinical origin (Fisher's exact test). Among meat isolates, in total 66.0% of E. faecalis and E. faecium isolates were susceptible to all antimicrobials tested and 32.6% were resistant to either one or two antimicrobials. In E. faecalis, several virulence genes were significantly associated with a clinical origin; the most common (31.0%) gene pattern included all the tested genes except hyl. In meat isolates, the virulence genes were detected in E. faecalis only and the most common pattern included ace, efaA, and gelE (32.5%), of which gelE showed a statistically significant association with a clinical origin. These results emphasize the importance of E. faecalis in red meat as a reservoir of virulence genes involved in its persistence and human infections with reported severe outcomes

    Longitudinal study of the effects of teat condition on the risk of new intramammary infections in dairy cows

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    Machine milking–induced alterations of teat tissue may impair local defense mechanisms and increase the risk of new intramammary infections. The objective of the current study was to assess the influence of short-term and long-term alterations of teat tissue and infectious status of the udder quarter on the risk of naturally occurring new intramammary infections, inflammatory responses, and mastitis. Short-term and long-term changes in teat condition of right udder quarters of 135 cows of a commercial dairy farm in Saxony-Anhalt, Germany, were recorded monthly for 10 mo using simple classification schemes. Quarter milk samples were collected from all examined quarters at each farm visit. Bacteriological culture results and somatic cell counts of quarter milk samples were used to determine new inflammatory responses (increase from ≤100,000 cells/mL to >100,000 cells/mL between 2 samples), new infections (detection of a pathogen from a quarter that was free of the same pathogen at the preceding sampling), and new mastitis (combination of new inflammatory response and new infection). Separate Poisson mixed models for new inflammatory responses, new infections, and new mastitis caused by specific pathogens or groups of pathogens (contagious, environmental, major, minor, or any) were used to estimate risk ratios and 95% confidence intervals. Data preparation and parameter estimation were performed using the open source statistical analysis software R. We observed no effect of any variable describing teat condition on the risk of new intramammary infections, inflammatory responses, or mastitis. Intramammary infections of the same udder quarter in the preceding month did not affect risk either

    Studies on the Growth of Chlorella vulgaris in Culture Media with Different Carbon Sources

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    Diminishing oil reserves, rising oil prices and a significant increase in atmospheric carbon dioxide levels have led to an increasing demand for alternative fuels. Microalgae have been suggested as a suitable means for fuel production because of their advantages related to higher growth rates, higher photosynthetic efficiency and higher biomass production, compared to other terrestrial energy crops. During photosynthesis, microalgae can fix carbon dioxide from different sources, including the atmosphere, industrial exhaust gases and soluble carbonate salts. To determine the most optimal conditions for the growth of Chlorella vulgaris in order to produce lipids that can be transformed into biodiesel fuel, different nutritional conditions were investigated. For this purpose, three media, namely Jaworski’s medium, an enriched solution from modified Dual Solvay process and natural mineral water, were prepared and analyzed for biomass production, chlorophyll content and lipid content. The best growth resulted in an enriched solution from the modified Solvay process. This medium was diluted in different dilution ratios (1:100, 1:50, 1:10) and the best results were obtained in a medium diluted in a 1:10 ratio on the fifth day of culturing (3.72 · 106 cells mL–1; 4.98 μg mL–1 chlorophyll a)

    No interactions between heparin and atacicept, an antagonist of B cell survival cytokines.

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    The TNF family ligands, B cell activating factor of the TNF family (BAFF, also known as B lymphocyte stimulator, BLyS) and a proliferation-inducing ligand (APRIL), share the transmembrane activator and calcium-modulator and cyclophilin ligand (CAML)-interactor (TACI) as one of their common receptors. Atacicept, a chimeric recombinant TACI/IgG1-Fc fusion protein, inhibits both ligands. TACI and APRIL also bind to proteoglycans and to heparin that is structurally related to proteoglycans. It is unknown whether the portion of TACI contained in atacicept can bind directly to proteoglycans, or indirectly via APRIL, and whether this could interfere with the anti-coagulant properties of heparin. Binding of atacicept and APRIL to proteoglycan-positive cells was measured by FACS. Activities of heparin and atacicept were measured with activated factor Xa inhibition and cell-based assays. Effects of heparin on circulating atacicept was monitored in mice. Atacicept did not bind to proteoglycan-positive cells, but when complexed to APRIL could do so indirectly via APRIL. Multimers of atacicept obtained after exposure to cysteine or BAFF 60-mer bound directly to proteoglycans. Atacicept alone, or in complex with APRIL, or in a multimeric form did not interfere with heparin activity in vitro. Conversely, heparin did not influence inhibition of BAFF and APRIL by atacicept and did not change circulating levels of atacicept. Lack of detectable interference of APRIL-bound or free atacicept on heparin activity makes it unlikely that atacicept at therapeutic doses will interfere with the function of heparin in vivo
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