University of Warwick

About: University of Warwick is a education organization based out in Coventry, Warwickshire, United Kingdom. It is known for research contribution in the topics: Population & White dwarf. The organization has 26212 authors who have published 77127 publications receiving 2666552 citations. The organization is also known as: Warwick University & The University of Warwick.

The stepped wedge cluster randomised trial: rationale, design, analysis, and reporting

Abstract: The stepped wedge cluster randomised trial is a novel research study design that is increasingly being used in the evaluation of service delivery type interventions. The design involves random and sequential crossover of clusters from control to intervention until all clusters are exposed. It is a pragmatic study design which can reconcile the need for robust evaluations with political or logistical constraints. While not exclusively for the evaluation of service delivery interventions, it is particularly suited to evaluations that do not rely on individual patient recruitment. As in all cluster trials, stepped wedge trials with individual recruitment and without concealment of allocation (or blinding of the intervention) are at risk of selection biases. In a stepped wedge design more clusters are exposed to the intervention towards the end of the study than in its early stages. This implies that the effect of the intervention might be confounded with any underlying temporal trend. A result that initially might seem suggestive of an effect of the intervention may therefore transpire to be the result of a positive underlying temporal trend. Sample size calculations and analysis must make allowance for both the clustered nature of the design and the confounding effect of time. The stepped wedge cluster randomised trial is an alternative to traditional parallel cluster studies, in which the intervention is delivered in only half the clusters with the remainder functioning as controls. When the clusters are relatively homogeneous (that is, the intra-cluster correlation is small), parallel studies tend to deliver better statistical performance than a stepped wedge trial. However, if substantial cluster-level effects are present (that is, larger intra-cluster correlations) or the clusters are large, the stepped wedge design will be more powerful than a parallel design, even one in which the intervention is preceded by a period of baseline control observations.

The purchasing power parity debate

Abstract: Originally propounded by the 16th-century scholars of the University of Salamanca, the concept of purchasing power parity (PPP) was revived in the interwar period in the context of the debate concerning the appropriate level at which to re-establish international exchange rate parities. Broadly accepted as a long-run equilibrium condition in the post-war period, it first was advocated as a short-run equilibrium by many international economists in the first few years following the breakdown of the Bretton Woods system in the early 1970s and then increasingly came under attack on both theoretical and empirical grounds from the late 1970s to the mid 1990s. Accordingly, over the last three decades, a large literature has built up that examines how much the data deviated from theory, and the fruits of this research have provided a deeper understanding of how well PPP applies in both the short run and the long run. Since the mid 1990s, larger datasets and nonlinear econometric methods, in particular, have improved estimation. As deviations narrowed between real exchange rates and PPP, so did the gap narrow between theory and data, and some degree of confidence in long-run PPP began to emerge again. In this respect, the idea of long-run PPP now enjoys perhaps its strongest support in more than 30 years, a distinct reversion in economic thought.

Evidence that participate methane monooxygenase and ammonia monooxygenase may be evolutionarily related

Abstract: Genes encoding paniculate methane monooxygenase and ammonia monooxygenase share high sequence identity. Degenerate oligonucleotide primers were designed, based on regions of shared amino acid sequence between the 27-kDa polypeptides, which are believed to contain the active sites, of particulate methane monooxygenase and ammonia monooxygenase. A 525-bp internal DNA fragment of the genes encoding these polypeptides ( pmoA and amoA ) from a variety of methanotrophic and nitrifying bacteria was amplified by PCR, cloned and sequenced. Representatives of each of the phylogenetic groups of both methanotrophs ( α- and γ-Proteobacteria) and ammonia-oxidizing nitrifying bacteria ( β-and y-Proteobacteria) were included. Analysis of the predicted amino acid sequences of these genes revealed strong conservation of both primary and secondary structure. Nitrosococcus oceanus AmoA showed higher identity to PmoA sequences from other members of the γ-Proteobacteria than to AmoA sequences. These results suggest that the particulate methane monooxygenase and ammonia monooxygenase are evolutionarily related enzymes despite their different physiological roles in these bacteria.