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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 11021-11030 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Using molecular-dynamics studies and static potential-energy minimization, we have resolved the mechanisms by which n-alkanes (ethane through n-decane) diffuse on a model Pt(111) surface in the low-coverage limit of a single adsorbed molecule. Our simulations reproduce all of the experimental trends seen for the adsorption and diffusion of C3–C6 on Pt(111) and Ru(001). The short alkanes (C2–C8) behave as rigid rods and their motion involves coupled translation and rotation in the surface plane. For this series, there is a linear increase of the diffusion barrier with the molecular chain length. We have analyzed the compliance of the motion of the assumptions of a nearest-neighbor hopping model. Although hopping motion can be observed for all of the molecules at sufficiently low temperatures, the hopping involves a significant fraction of long jumps. As the temperature increases, the adsorption becomes virtually delocalized. Despite the extensive deviations of the motion from the assumptions of a nearest-neighbor hopping model, the static diffusion-energy barriers, arising from the minimum-energy path for hops between nearest-neighbor binding sites, agree well with those obtained from the tracer-diffusion coefficients for butane, hexane, and octane. For these molecules, multiple-site hops and long flights appear to influence the values of the preexponential factors, which are too large. Neither the diffusion barrier nor the preexponential factor for ethane agrees well with theoretical estimates. We attribute these discrepancies to the smallness of the static diffusion barrier and/or the existence of unique dynamical behavior for this molecule. Due to the increased difficulty of in-plane rotation and increased mismatch between the geometries of the molecule and the surface, the diffusion barrier for n-decane drops below that for n-hexane. The characteristic mechanism of motion for n-decane involves significant C–C–C bond-angle bending. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 63 (1998), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study's objectives were to investigate the effects of buffer type and concentration on the kinetics of the Maillard reaction in low-moisture solids. Glucose loss and brown pigment formation were evaluated in low-moisture glassy systems obtained by lyophilizing solutions containing various concentrations of phosphate or citrate buffer at pH 7 and 25°C. Rate constants for glucose loss decreased as buffer concentration increased, suggesting that a change in the system pH had occurred. Rate constants for browning increased with increasing phosphate buffer concentration and decreased with increasing citrate concentration. Phosphate buffer appeared to catalyze later pathways of the Maillard reaction.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of food science 63 (1998), S. 0 
    ISSN: 1750-3841
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of water activity and the glass transition on the rate constants for glycine loss and brown pigment formation due to the Maillard reaction were evaluated in a model food system. Equimolar glucose and glycine were incorporated into amorphous polyvinylpyrrolidones of various molecular weights and moisture contents. Glycine loss and brown pigment formation were quantified during storage at 25°C. At constant water activity, rate constants were higher in systems with lower glass transition temperatures. Glycine rate constants decreased upon matrix collapse, but browning rate constants were not affected by collapse. Changes associated with the glass transition influence bimolecular reactions and should be considered during product formulation and shelf-life testing.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Environmental science & technology 26 (1992), S. 2534-2536 
    ISSN: 1520-5851
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 27 (1988), S. 7189-7196 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of clinical periodontology 24 (1997), S. 0 
    ISSN: 1600-051X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Access surgery may be recommended to about 80% of patients who present with advanced forms of periodontal disease. In this report, a multivariate logistic regression analysis which incorporated several clinical parameters for each tooth examined, i.e., tooth type, furcation involvement, bleeding on probing, attachment level, probing depth, mobility and BANA test score, was conducted using generalized estimating equations (GEE). This approach identified parameters that were significantly associated at p 〈 0.05 level with the need for access surgery or extraction for periodontal purposes. The estimated probabilities derived from the GEE model were plotted over the complete spectrum of operating conditions to obtain a receiver-operator characteristic (ROC) curve. At a probability cutpoint of 0.8, the decision threshold for surgery/extraction at the pre-treatment examination would have a sensitivity of 76.1% and a specificity of 75.3%. We have taken this 0.8 cut point to look at specific clinical decisions made by our examiners after the patients had received scaling and root planing plus 2 weeks unsupervised usage of systemic antimicrobials. The clinicians' decision was taken as the primary reference standard. The model's estimated decision agreed with the clinicians' decision in 226 of the 284 teeth, for an accuracy of 80%. The specificity was 90% and the sensitivity was 43%.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-0972
    Keywords: Alcaligenes eutrophus ; cell growth ; environmental conditions ; poly-β-hydroxybutyrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Influences of the control of glucose and oxygen concentrations on cell growth and poly-β-hydroxybutyrate (PHB) accumulation in Alcaligenes eutrophus were studied. Glucose affects both biosynthesis and glycolysis directly and the other pathways indirectly. PHB accumulation could also be stimulated under oxygen limitation conditions, but the final PHB content within the cells was less than in the case of nitrogen limitation. When the culture was shifted from the PHB accumulation state to balanced growth conditions, PHB degradation occurred in the cells. The cell growth was inhibited by high PHB content within the cells.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Chemical Technology AND Biotechnology 66 (1996), S. 227-232 
    ISSN: 0268-2575
    Keywords: coagulation ; flocculation ; chitosan ; bentonite ; kaolinite ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: The feasibility of applying chitosan, as prepared from the crab chitin, was assessed in this study for the coagulation of colloidal particles. A series of batch flocculation tests with chitosan under different conditions was also conducted. The results indicate that chitosan is a potent coagulant for bentonite suspension. The relationship between the optimum chitosan dosage and the turbidity of the bentonite suspension is presented as a linear correlation. The evidence infers that an adequate range of the coagulant dosage is the primary consideration in determining the removal efficiency for the turbidity of the source water. It also indicates that the coagulation behavior for kaolinite by chitosan is different from that of bentonite, i.e., chitosan fails to form a good aggregate with kaolinite. Turbid water containing particles which show behavior similar to kaolinite apparently need to have some bentonite particles added as coagulant aid, thereby improving the aggregation of the colloid particles with chitosan. Moreover, the effect of pH on the coagulation efficiency of chitosan is insignificant. The evidence infers that charge neutralization is not a major mechanism controlling the formation of floc for chitosan coagulation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Publication Date: 2022-05-26
    Description: © The International Society for Microbial Ecology, 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in ISME Journal 10 (2016): 968–978, doi:10.1038/ismej.2015.172.
    Description: Upon phosphorus (P) deficiency, marine phytoplankton reduce their requirements for P by replacing membrane phospholipids with alternative non-phosphorus lipids. It was very recently demonstrated that a SAR11 isolate also shares this capability when phosphate starved in culture. Yet, the extent to which this process occurs in other marine heterotrophic bacteria and in the natural environment is unknown. Here, we demonstrate that the substitution of membrane phospholipids for a variety of non-phosphorus lipids is a conserved response to P deficiency among phylogenetically diverse marine heterotrophic bacteria, including members of the Alphaproteobacteria and Flavobacteria. By deletion mutagenesis and complementation in the model marine bacterium Phaeobacter sp. MED193 and heterologous expression in recombinant Escherichia coli, we confirm the roles of a phospholipase C (PlcP) and a glycosyltransferase in lipid remodelling. Analyses of the Global Ocean Sampling and Tara Oceans metagenome data sets demonstrate that PlcP is particularly abundant in areas characterized by low phosphate concentrations. Furthermore, we show that lipid remodelling occurs seasonally and responds to changing nutrient conditions in natural microbial communities from the Mediterranean Sea. Together, our results point to the key role of lipid substitution as an adaptive strategy enabling heterotrophic bacteria to thrive in the vast P-depleted areas of the ocean.
    Description: This work was partially supported by grants STORM (CTM2009-09352/MAR), MALASPINA (CSD2008-00077), HOTMIX (CTM2011-30010/MAR), DOREMI (CTM2012-34294) and EcoBGM (CTM2013-48292-C3-3-R) funded by the Spanish Government, GAČR project GA13-11281S and MESOAQUA (228224) funded by the European Union Seventh Framework Program (FP7/2007-2013) and by the Natural Environment Research Council (NERC), UK (NE/M002233/1).
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2013-07-02
    Description: Background: Microglial activations have been described in different subtypes of human prion diseases such as sporadic Creutzfeldt-Jakob disease (CJD), variant CJD, Kuru and Gerstmann-Straussler-Scheinker disease (GSS). However, the situation of microglia in other genetic prion diseases such as fatal familial insomnia (FFI) and familial CJD remains less understood. The brain microglia was evaluated comparatively between the FFI, G114V and sCJD cases in the study. Methods: Specific Western blots, immunohistochemical and immunofluorescent assays were used to detect the changes of microglia and ELISA tests were used for levels of inflammatory cytokines. Results: Western blots, immunohistochemical and immunofluorescent assays illustrated almost unchanged microglia in the temporal lobes of FFI and G114V gCJD, but obviously increased in those of sCJD. The Iba1-levels maintained comparable in six different brain regions of FFI and G114V cases, including thalamus, cingulate gyrus, frontal cortex, parietal cortex, occipital cortex and temporal cortex. ELISA tests for inflammatory cytokines revealed significantly up-regulated IL-1beta, IL-6 and TNF-alpha in the brain homogenates from sCJD, but not in those from FFI and G114V gCJD. Conclusion: Data here demonstrates silent brain microglia in FFI and G114V gCJD but obviously increased in sCJD, which reflects various pathogenesis of different human prion diseases subtypes.
    Electronic ISSN: 1743-422X
    Topics: Medicine
    Published by BioMed Central
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