Simulation from quasi-stationary distributions on reducible state spaces

Quasi-stationary distributions (QSDs) arise from stochastic processes that exhibit transient equilibrium behaviour on the way to absorption. QSDs are often mathematically intractable and even drawing samples from them is not straightforward. In this paper the framework of Sequential Monte Carlo samplers is utilized to simulate QSDs and several novel resampling techniques are proposed to accommodate models with reducible state spaces, with particular focus on preserving particle diversity on discrete spaces. Finally an approach is considered to estimate eigenvalues associated with QSDs, such as the decay parameter

Propensity score regression analysis of oesophageal cancer treatment with surgery alone or neoadjuvant chemotherapy

Background: Propensity score (PS) regression analysis can be used to minimize differences between cohorts in order to perform comparisons The aim of this study was to use PS analysis to examine the outcomes of oesophageal adenocarcinoma (OAC) treatment with surgery alone or neoadjuvant chemotherapy (NAC) followed by surgery (NACS), to see whether the benefits seen in a randomized trial (MRC OE02) were reproducible in a UK cancer network clinical practice. Methods: Consecutive patients undergoing potentially curative treatment for OAC in a regional cancer network were studied. Multiple regression models, including PS analysis, were developed to account for confounding factors. Primary outcome measures were disease‐free (DFS) and overall (OS) survival. Results: A cohort of 440 patients was included in a regression analysis controlling for confounders (176 surgery alone, 264 NACS). NACS was associated with a higher positive margin status rate compared with surgery alone (42·4 versus 26·7 per cent respectively; P < 0·001), an inferior 5‐year DFS rate (32·1 versus 56·9 per cent; P < 0·001) and a worse 5‐year OS rate (27·5 versus 47·3 per cent; P < 0·001). On regression adjustment based on propensity scores, NACS was not associated with DFS (P = 0·220) or OS (P = 0·431). The Mandard tumour regression grade (TRG) score was significantly associated with DFS (hazard ratio (HR) 0·21, 95 per cent c.i. 0·07 to 0·70) and OS (HR 0·27, 0·13 to 0·59). Five‐year DFS and OS rates related to TRG were 64 and 62 per cent respectively for 25 good responders versus 8·0 and 8·6 per cent for 127 poor responders (P < 0·001). Conclusion: The prescription of NAC to all patients with OAC risks delay in effective treatment of patients who are relatively chemoresistant, given the variability in pathological response. Identification of patients with OAC who may derive the most benefit from NAC should be the focus

Electrocardiographic changes during haemodialysis and the potential impact on subcutaneous implantable cardioverter defibrillator eligibility

Acknowledgments The authors would like to acknowledge the kindness and support that they received from all of the patients and staff at the Chandler's Ford Dialysis Unit. Funding This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.Peer reviewedPublisher PD

Quasi-stationary Monte Carlo and the ScaLE Algorithm

This paper introduces a class of Monte Carlo algorithms which are based upon simulating a Markov process whose quasi-stationary distribution coincides with a distribution of interest. This differs fundamentally from, say, current Markov chain Monte Carlo methods which simulate a Markov chain whose stationary distribution is the target. We show how to approximate distributions of interest by carefully combining sequential Monte Carlo methods with methodology for the exact simulation of diffusions. The methodology introduced here is particularly promising in that it is applicable to the same class of problems as gradient based Markov chain Monte Carlo algorithms but entirely circumvents the need to conduct Metropolis-Hastings type accept/reject steps whilst retaining exactness: the paper gives theoretical guarantees ensuring the algorithm has the correct limiting target distribution. Furthermore, this methodology is highly amenable to big data problems. By employing a modification to existing naıve sub-sampling and control variate techniques it is possible to obtain an algorithm which is still exact but has sub-linear iterative cost as a function of data size

'Supra is not for women' : hospitality practices as a lens on gender and social change in Georgia

Peer reviewe

Exploring Patients' Experiences of Internet-Based Self-Management Support for Low Back Pain in Primary Care

OBJECTIVE: We explored patients' experiences of using Internet-based self-management support for low back pain (LBP) in primary care, with and without physiotherapist telephone guidance. DESIGN: Exploratory descriptive qualitative study using thematic analysis, nested within a randomized feasibility trial. METHODS: Patients with LBP who participated in a feasibility trial of the SupportBack Internet intervention (ISRCTN: 31034004) were invited to take part in semistructured telephone interviews after the three-month intervention period (a convenience sample from within the trial population). Fifteen participants took part (age range = 36-87 years, 66.7% female, characteristics representative of the trial population). Data were analyzed thematically. RESULTS: Analysis resulted in the development of six themes (subthemes in parentheses): Perceptions of SupportBack's design (Clarity and ease of use, Variety and range of information provided, Need for specificity and flexibility), Engaging with the SupportBack intervention, Promoting positive thought processes (Reassurance, Awareness of self-management), Managing behavior with SupportBack (Motivation and goal setting, Using activity as a pain management strategy, Preferences for walking or gentle back exercises), Feeling supported by telephone physiotherapists (Provision of reassurances and clarity, Physiotherapists are motivating), Severity and comorbidity as barriers (Preexisting condition or severity acting as a barrier, Less useful for mild low back pain). CONCLUSIONS: The Internet intervention SupportBack appeared to feasibly support self-management of LBP. Reassurance and ongoing support to implement behavioral changes were central to reported benefits. The addition of physiotherapist telephone support further enhanced the patient experience and the potential utility of the intervention

Complete Genome Sequence and Comparative Metabolic Profiling of the Prototypical Enteroaggregative Escherichia coli Strain 042

Background \ud Escherichia coli can experience a multifaceted life, in some cases acting as a commensal while in other cases causing intestinal and/or extraintestinal disease. Several studies suggest enteroaggregative E. coli are the predominant cause of E. coli-mediated diarrhea in the developed world and are second only to Campylobacter sp. as a cause of bacterial-mediated diarrhea. Furthermore, enteroaggregative E. coli are a predominant cause of persistent diarrhea in the developing world where infection has been associated with malnourishment and growth retardation. \ud \ud Methods \ud In this study we determined the complete genomic sequence of E. coli 042, the prototypical member of the enteroaggregative E. coli, which has been shown to cause disease in volunteer studies. We performed genomic and phylogenetic comparisons with other E. coli strains revealing previously uncharacterised virulence factors including a variety of secreted proteins and a capsular polysaccharide biosynthetic locus. In addition, by using Biolog™ Phenotype Microarrays we have provided a full metabolic profiling of E. coli 042 and the non-pathogenic lab strain E. coli K-12. We have highlighted the genetic basis for many of the metabolic differences between E. coli 042 and E. coli K-12. \ud \ud Conclusion \ud This study provides a genetic context for the vast amount of experimental and epidemiological data published thus far and provides a template for future diagnostic and intervention strategies