966 resultados para quick-EXAFS


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Mode of access: Internet.

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The three-dimensional branched nature of dendritic macromolecules provides many potential sites per molecule for the complexation of metal ions. Therefore, dendrimers may act as hosts for metals with coordination potentially occurring at the periphery, the interior, or both. To understand further the complexation of dendrimers with metal ions EXAFS experiments were carried out. In this work, the interaction of amine-terminated polyamido(amine), PAMAM, dendrimer with copper(II) ions determined by EXAFS is reported. It was found that a model consisting of the copper(II) ion forming five- and six-membered rings by chelating with the primary amine, amide, and tertiary amine nitrogen donors of the PAMAM dendrimer could describe the experimental EXAFS data well. Corroborative evidence for binding to amide nitrogen donors comes from the broadening of NMR resonances of a copper(Il)-PAMAM mixture revealing the presence of paramagnetic copper(II) ions at these sites. The significance of the results presented in this paper is that copper(II) ions form complexes within the dendrimer structure and not just at the periphery. The current study may have implications for the use of PAMAM dendrimers as effective ligands in sensing systems.

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Local structures around host Ce and dopant Y cations in 10 mol% Y2O3 doped ceria solid solutions have been investigated by room and high temperature EXAFS spectroscopy. The results show that the local structures around the Cc cation in doped ceria samples are similar to that in the fluorite CeO2 structure though the coordination numbers of Ce-O tend to be smaller than 8. The local structures around Y cation, however, are significantly different from those around Ce cation, and show more resemblance to that around Y cation in the C-type Y2O3 Structure. A more accurate description of the local structures around Y cation in doped ceria was given by analyzing Y-K edge EXAFS spectra based on the C-type Y2O3 structure. (c) 2006 Elsevier B.V. All rights reserved.

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A robust vaginal immune response is considered essential for an effective prophylactic vaccine that prevents transmission of HIV and other sexually acquired diseases. Considerable attention has recently focused on the potential of vaginally administered vaccines as a means to induce such local immunity. However, the potential for vaccination at this site remains in doubt as the vaginal mucosa is generally considered to have low immune inductive potential. In the current study, we explored for the first time the use of a quick release, freeze-dried, solid dosage system for practical vaginal administration of a protein antigen. These solid dosage forms overcome the common problem associated with leakage and poor retention of vaginally administered antigen solutions. Mice were immunized vaginally with H4A, an HIV gp41 envelope based recombinant protein, using quick release, freeze-dried solid rods, and the immune responses compared to a control group immunized via subcutaneous H4A injection. Vaginally immunized mice failed to elicit robust immune responses. Our detailed investigations, involving cytokine analysis, the stability of H4A in mouse cervicovaginal lavage, and elucidation of the state of H4A protein in the immediate-release dosage form, revealed that antigen instability in vaginal fluid, the state of the antigen in the dosage form, and the cytokine profile induced are all likely to have contributed to the observed lack of immunogenicity. These are important factors affecting vaginal immunization and provide a rational basis for explaining the typically poor and variable elicitation of immunity at this site, despite the presence of immune responsive cells within the vaginal mucosae. In future mucosal vaccine studies, a more explicit focus on antigen stability in the dosage form and the immune potential of available antigen-responsive cells is recommended.

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Strontium has been substituted for calcium in the glass series (SiO2)49.46(Na2O)26.38(P2O5)1.07(CaO)23.08x(SrO)x (where x = 0, 11.54, 23.08) to elucidate their underlying atomic-scale structural characteristics as a basis for understanding features related to the bioactivity. These bioactive glasses have been investigated using isomorphic neutron and X-ray diffraction, Sr K-edge EXAFS and solid state 17O, 23Na, 29Si, 31P and 43Ca magic-angle-spinning (MAS) NMR. An effective isomorphic substitution first-order difference function has been applied to the neutron diffraction data, confirming that Ca and Sr behave in a similar manner within the glass network, with residual differences attributed to solely the variation in ionic radius between the two species. The diffraction data provides the first direct experimental evidence of split Ca–O nearest-neighbour correlations in these melt quench bioactive glasses, together with an analogous splitting of the Sr–O correlations; the correlations are attributed to the metal ions correlated either to bridging or to non-bridging oxygen atoms. Triple quantum (3Q) 43Ca MAS NMR corroborates the split Ca–O correlations. Successful simplification of the 2 < r (A) < 3 region via the difference method has also revealed two distinct Na environments. These environments are attributed to sodium correlated either to bridging or to nonbridging oxygen atoms. Complementary multinuclear MAS NMR, Sr K-edge EXAFS and X-ray diffraction data supports the structural model presented. The structural sites present will be intimately related to their release properties in physiological fluids such as plasma and saliva, and hence the bioactivity of the material. Detailed structural knowledge is therefore a prerequisite for optimising material design.

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What do you do if your boss calls you in to talk about job cuts? What are your rights? What are his or her rights? Do you know the procedures that should be followed? If redundancy looms, or you just want to be prepared for the worst,you need to know where you stand.Author Kathy Daniels is well placed to help. She writes and lectures extensively on human resources and employee rights, and as a member of the Employment Tribunal she regularly comes face-to-face with redundancy claims. In this easy-to-understand guide she answers all the important questions on redundancy and its aftermath, including: How are staff selected for redundancy? What is voluntary redundancy? Are full-time,part-time and agency staff treated differently? What is the consultation process bosses must adhere to? How much redundancy pay can you expect? How do you take a claim to the Employment Tribunal? As well as covering all the legal dos and don'ts, helpful guidance is provided on: Budgets and personal finances after redundancy Benefits you may be able to claim Coping with stress and strain Finding a new job or changing career The Quick Guide to Surviving Redundancy is full of real-life case studies and top tips on your employment rights. It also includes template letters for a range of redundancy situations.

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By 1990 the quick sevice restaurant industry(QSR) achieved 54 percent of commercial food service market share. QSR has a significant role to play in the rapidly-growing global hospitality industry and is expanding into institutional food service to increase its market share. It is expected to be the dominant player in the U.S. food service industry. The authors include an analysis of current and emerging trends in this industry.

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The purpose of this paper is to compare prices for a popular quick-service restaurant chain (i.e. McDonalds’) across countries throughout the world using the “Big Mac Index” published by “The Economist.” The index was originally developed to measure the valuation of international currencies against the U.S. dollar. The analysis in this study examines the relationship between the price of a Big Mac and other variables such as the cost of beef, price elasticity, and income. Finally, these relationships are reviewed to draw inferences concerning the use of demand, costs, and competition in setting prices.

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Social responsibility (SR) is becoming an increasingly significant component of many firms’ strategic planning decisions. Research has shown that consumers tend to reward socially responsible behavior. However, there has been little testing of the construct in the hospitality industry. Additionally, when other important variables that influence consumer brand loyalty are considered, will brand social responsibility image (BSRI) still play a significant role? This study investigates the importance of SR and its impact on brand loyalty, relative to product quality and service quality in the quick-service restaurant industry. The authors were also interested to learn whether BSRI impacted consumers' image of product and service quality. It was found that BSRI had a positive impact on brand loyalty, product quality, and service quality. However, product quality was a significantly stronger predictor of brand loyalty than BSRI. Where the vast majority of studies of SR have utilized scenario analysis of hypothetical firms, this study utilizes consumers' perceptions of a real-world firm.