Effects of neighborhood walkability on healthy weight: assessing selection and causal influences

Studies that examine the relationship between neighborhood characteristics and weight are limited because residents are not randomly distributed into neighborhoods. If associations are found between neighborhood characteristics and weight in observational studies, one cannot confidently draw conclusions about causality. We use data from the Utah Population Database (UPDB) that contain body mass index (BMI) information from all drivers holding a Utah driver license to undertake a cross-sectional analysis that compares the neighborhood determinants of BMI for youth and young adults. This analysis assumes that youth have little choice in their residential location while young adults have more choice. Our analysis makes use of data on 53,476 males and 47,069 females living in Salt Lake County in 2000. We find evidence of residential selection among both males and females when BMI is the outcome. The evidence is weaker when the outcomes are overweight or obesity. We conclude that studies that ignore the role of residential selection may be overstating the causal influence of neighborhood features in altering residents’ BMI.     

Post hoc false positive control for structured hypotheses

In a high-dimensional multiple testing framework, we present new confidence bounds on the false positives contained in subsets S of selected null hypotheses. These bounds are post hoc in the sense that the coverage probability holds simultaneously over all S, possibly chosen depending on the data. This article focuses on the common case of structured null hypotheses, for example, along a tree, a hierarchy, or geometrically (spatially or temporally). Following recent advances in post hoc inference, we build confidence bounds for some prespecified forest-structured subsets and deduce a bound for any subset S by interpolation. The proposed bounds are shown to improve substantially previous ones when the signal is locally structured. Our findings are supported both by theoretical results and numerical experiments. Moreover, our bounds can be obtained by an algorithm (with complexity bilinear in the sizes of the reference hierarchy and of the selected subset) that is implemented in the open-source R package sansSouci available from https://github.com/pneuvial/sanssouci , making our approach operational.     

Costing Mixed Coxian Phase-type Systems with Poisson Arrivals

Previously, we developed a modeling framework which classifies individuals with respect to their length of stay (LOS) in the transient states of a continuous-time Markov model with a single absorbing state; phase-type models are used for each class of the Markov model. We here add costs and obtain results for moments of total costs in (0, t], for an individual, a cohort arriving at time zero and when arrivals are Poisson. Based on stroke patient data from the Belfast City Hospital we use the overall modelling framework to obtain results for total cost in a given time interval.     

An Extended Mixture Distribution Survival Tree for Patient Pathway Prognostication

Mixture distribution survival trees are constructed by approximating different nodes in the tree by distinct types of mixture distributions to improve within node homogeneity. Previously, we proposed a mixture distribution survival tree-based method for determining clinically meaningful patient groups from a given dataset of patients’ length of stay. This article extends this approach to examine the interrelationship between length of stay in hospital, outcome measures, and other covariates. We describe an application of this approach to patient pathway and examine the relationship between length of stay in hospital and/or treatment outcome using five-years’ retrospective data of stroke patients.     

Serial Entrepreneurs

This study focuses on the dynamic nature of entrepreneurship through an analysis of serial entrepreneurs, those individuals who engage in multiple start-ups, management buyouts, management buy-ins and combinations of these activities. The paper develops a typology of habitual entrepreneurship and then examines serial entrepreneurs in detail as a subset of such entrepreneurs. The processes involved and the effects of individuals undertaking sequential ventures are analysed. The study identifies three types of serial entrepreneurial behaviour namely venture repeaters, organic serials and serial dealmakers, distinguished by the motivations and the methods used to develop their ventures. Case-study evidence from the study also indicates that the role of active investors varies according to the type of serial entrepreneur and venture.     

Solar energy: Where policy-makers and conservationists disagree

Solar energy policy-makers and solar energy advocates use significantly different scenarios upon which they perceive and evaluate the adoption of solar technologies. The differences between the two groups seem to be rooted in different hierarchies of values relating to solar energy policy. Policy-makers emphasize the economic and national security values of solar energy. On the other hand, solar energy advocates stress environmental, ethical and social values. Aside from understanding the different groups in the on-going energy debate better, the findings of the study have important implications for planners both in government and industry as they may help increase the effectiveness of their plans.     

Treatment issues pertaining to pathological gamblers with a comorbid disorder

Evidence of an increased risk for various psychiatric disorders among pathological gamblers far exceeds our understanding of the impact that this psychiatric comorbidity has on the outcome of treatment for pathological gambling. One major source of the problem is that treatment efficacy and effectiveness studies for pathological gambling typically have not addressed comorbidity's impact on outcome. This paper discusses epidemiological, clinical, health service delivery, and research issues pertaining to the intersection of pathological gambling treatment outcome and comorbid psychiatric disorders. It is argued that this topic suffers from major knowledge gaps in terms of the nature of comorbidity of pathological gambling and other psychiatric disorders and the role of client characteristics on treatment outcome for pathological gambling. Research priorities are identified.     

The Emergence of Flexible Networks in the UK Television Industry

‘Flexibility’ became a management buzz word in the mid-to-late 1980s. Environmental pressures drove firms in many industries towards more flexible structures – away from internal, classical hierarchies towards agent networks brought together on individual project-task grounds. The goal of many organizations, according to proponents of this trend, became that of seeking ‘flexible specialization’– integrating specialist resources in a dynamic, flexible fashion. Critics of the drive towards flexibility argue that the phenomenon has been overemphasized, and that large-scale bureaucracies geared for mass production are still the dominant structural form. This paper overviews the arguments concerning flexibility and related arguments concerning the emergence of networked forms of organization. Flexibility trends within the UK television industry are then explored to illustrate the emergence of ‘flexible specialization’ and a ‘dynamic network’ form of organization. Television thus serves as an important counter-factual to the dismissive claims of the critics of flexibility.