214 resultados para relatividad General


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Timely and convenient access to primary healthcare is essential for the health of the population as delays can incur additional health and financial costs. Access to health care is under increasing scrutiny as part of the drive to contain escalating costs, while attempting to maintain equity in service provision. The objective was to compare primary care services in Republic of Ireland and Northern Ireland, and to report on perceived and reported access to GP services in universal access and mixed private/public systems. A questionnaire study was performed in Northern Ireland (NI) and the Republic of Ireland (ROI). Patients of 20 practices in the ROI and NI were contacted (n = 22,796). Main outcome measures were overall satisfaction and the access to GP services. Individual responses and scale scores were derived using the General Practice Assessment Questionnaire (G-PAQ). The response rate was 52% (n = 11,870). Overall satisfaction with GP practices was higher in ROI than in NI (84.2% and 80.9% respectively). Access scores were higher in ROI than in NI (69.2% and 57.0% respectively) Less than 1 in 10 patients in ROI waited two or more working days to see a doctor of choice (8.1%) compared to almost half (45.0%) in NI. In NI overall satisfaction decreased as practice size increased; 82.8%, 80.4%, and 75.8%. In both systems, in large practices, accessibility is reduced when compared to smaller practices. The faster access to GP services in ROI may be due to the deterrent effect of the consultation charge freeing up services although, as it is the poorest and sickest who are deterred by the charge this improved accessibility may come at a significant cost in terms of equity. The underlying concern for policy makers centres around provision of equitable services.

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CO oxidation on PtO2(110) has been studied using density functional theory calculations. Four possible reaction mechanisms were investigated and the most feasible one is the following: (i) the O at the bridge site of PtO2(110) reacts with CO on the coordinatively unsaturated site (CUS) with a negligible barrier; (ii) O-2 adsorbs on the bridge site and then interacts with CO on the CUS to form an OO-CO complex; (iii) the bond of O-OCO breaks to produce CO2 with a small barrier (0.01 eV). The CO oxidation mechanisms on metals and metal oxides are rationalized by a simple model: The O-surface bonding determines the reactivity on surfaces; it also determines whether the atomic or molecular mechanism is preferred. The reactivity on metal oxides is further found to be related to the 3rd ionization energy of the metal atom.

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A catalyst preparation by design is one of the ultimate goals in chemistry. The first step towards this goal is to understand the origin of reaction barriers. In this study, we have investigated several catalytic reactions on some transition metal surfaces, using density functional theory. All the reaction barriers have been determined. By detailed analyses we obtain some insight into the reaction barrier. Each barrier is related to (i) the potential energy surface of reactants on the surface, (ii) the total chemisorption energy of reactants, and (iii) the metal d orbital occupancy and the reactant valency. (C) 2001 American Institute of Physics.