Comprehensive mechanisms for combustion chemistry: An experimental and numerical study with emphasis on applied sensitivity analysis

Over the last three years, this program has made significant progress on a number of problems: development of a data base for oxidation of the CO/H[sub 2]/O[sub 2] system; development and refinement of a comprehensive kinetic mechanism for the CO/H[sub 2]/O[sub 2] system; additional experiments on formaldehyde oxidation in the, comprehensive mechanistic studies inclusive of flow reactor results and literature results from static reactors, shock tubes, and flames, and identification of elementary reactions needing further study; mechanistic study of previously acquired APFR flow reactor data on ethanol oxidation, including an estimation of the branching ratios for C[sub 2]H[sub 5]0H + X, X= OH,H and identification of elementary reactions needing additional study; completion and mechanistic evaluation of the first insitu optical diapostic measurements of OH in the APFR; determinations of uni-molecular decomposition rate for 1,3,5-Trioxane at 700 to 800 K; seeded perturbation experiments on moist CO oxidation in flow reactors as a means to determine elementary rate constants for specific reactions; determination of elementary rates for CH[sub 4] + OH [yields] CH[sub 3] + H[sub 2]0 at 1026 and 1140 K, and C[sub 3]H[sub 6] + OH [yields] products at 1020 K; First experimental studies of the H[sub 2]/O[sub 2] reaction system in the VPFR at conditions between the extended second and third explosion limits

Inhibition of moist carbon monoxide oxidation by trace amounts of hydrocarbons

The moist carbon monoxide oxidation reaction perturbed by small quantities of hydrocarbons is studied over the temperature range 1026--1140 K at 1 atm to yield information on the reactions of OH, H, and O radicals with hydrocarbons (RH) and on general mechanistic inhibition behavior. The inhibiting action of hydrocarbons below the second explosion limit of Co/H{sub 2}O/O{sub 2} mixtures is used for obtaining rate parameters for RH + OH in the case of methane and propene. Considering all the hydrocarbons studied, the general ranking of effectiveness as an inhibitor was found to follow the order: propene > propane > methane > ethane > ethene > acetylene. In fact, acetylene was observed to always promote the oxidation of moist CO, thus emphasizing the importance of O-atom radical attack rather than OH attack on acetylene. The kinetics of these mixtures are shown to complement mechanistic studies on RH/O{sub 2} mixtures for the development and validation of hierarchical hydrocarbon oxidation reaction mechanisms

The reinfection threshold regulates pathogen diversity: the case of influenza

The awareness that pathogens can adapt and evolve over relatively short time-scales is changing our view of infectious disease epidemiology and control. Research on the transmission dynamics of antigenically diverse pathogens is progressing and there is increasing recognition for the need of new concepts and theories. Mathematical models have been developed considering the modelling unit in two extreme scales: either diversity is not explicitly represented or diversity is represented at the finest scale of single variants. Here, we use an intermediate approach and construct a model at the scale of clusters of variants. The model captures essential properties of more detailed systems and is much more amenable to mathematical treatment. Specificities of pathogen clusters and the overall potential for transmission determine the reinfection rates. These are, in turn, important regulators of cluster dynamics. Ultimately, we detect a reinfection threshold (RT) that separates different behaviours along the transmissibility axis: below RT, levels of infection are low and cluster substitutions are probable; while above RT, levels of infection are high and multiple cluster coexistence is the most probable outcome

Communicating the effectiveness and ineffectiveness of government policies and their impact on public support: a systematic review with meta-analysis.

Low public support for government interventions in health, environment and other policy domains can be a barrier to implementation. Communicating evidence of policy effectiveness has been used to influence attitudes towards policies, with mixed results. This review provides the first systematic synthesis of such studies. Eligible studies were randomized controlled experiments that included an intervention group that provided evidence of a policy's effectiveness or ineffectiveness at achieving a salient outcome, and measured policy support. From 6498 abstracts examined, there were 45 effect sizes from 36 eligible studies. In total, 35 (N = 30 858) communicated evidence of effectiveness, and 10 (N = 5078) communicated evidence of ineffectiveness. Random effects meta-analysis revealed that communicating evidence of a policy's effectiveness increased support for the policy (SMD = 0.11, 95% CI [0.07, 0.15], p < 0.0001), equivalent to support increasing from 50% to 54% (95% CI [53%, 56%]). Communicating evidence of ineffectiveness decreased policy support (SMD = -0.14, 95% CI [-0.22, -0.06], p < 0.001), equivalent to support decreasing from 50% to 44% (95% CI [41%, 47%]). These findings suggest that public support for policies in a range of domains is sensitive to evidence of their effectiveness, as well as their ineffectiveness.This report is independent research commissioned and funded by the National Institute for Health Research Policy Research Programme (Policy Research Unit in Behaviour and Health [PR-UN-0409-10109]). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research, the Department of Health and Social Care or its arm's length bodies, and other Government Departments