Mapping the regional transition to cyclicity inClethrionomys rufocanus: Spectral densities and functional data analysis

We study the regional transitions in dynamics of the gray-sided vole,Clethrionomys rufocanus, within Hokkaido, Japan. The data-set consists of 225 time series of varying length (most from 23 to 31 years long) collected between 1962 and 1992 by the Forestry Agency of the Japanese Government. To see clearly how the periodic behavior changes geographically, we estimate the spectral density functions of the growth rates of all populations using a log-spline method. We subsequently apply functional data analysis to the estimated densities. The functional data analysis is, in this context, analogous to a principal component analysis applied to curves. We plot the results of the analysis on the map of Hokkaido, to reveal a clear transition from relatively stable populations in the southwest and west to populations undergoing 3–4 year cycles in the northeast and east. The degree of seasonality in the vegetation and the rodent demography appear to be strongest in the cyclic area. We briefly speculate that the destabilization of the rodent dynamics is linked to increased seasonalforcing on the trophic interactions in which the gray-sided voles are involved.     

Physician-led: good idea or not?

Whether physicians or not, leaders must possess certain skills and qualities to achieve success. Take a look at what's required to be an effective leader.     

‘We are not as alike,as you think’ sense of individuality within the co-twin relationship along the life course

We have explored how older twins experience and describe themselves in relation to their co-twin. The life stories of 20 older twins were analyzed with narrative analysis.Results showed that the twins described themselves from the point of differences in relation to the co-twin. This was based on experiences of how other people viewed them as alike, as well as on life events along the life course, which contributed to the perception of oneself as an individual in relation to the co-twin. The emphasis on unlikeness was therefore interpreted as a way of trying to establish a position as an individual within the co-twin relationship and to assert ones individuality to the rest of the social environment. To claim oneself as an individual was an ongoing identity work along the life course.     

A pilot study of CBT versus escitalopram combined with CBT in the treatment of pathological gamblers

We conducted a randomised controlled trial pilot study (N = 30) with two treatment groups: (1) Manualised cognitive behavioural therapy (CBT) (n = 15) and (2) escitalopram combined with CBT (n = 15). Treatment was administered individually and the CBT included weekly sessions for eight consecutive weeks. The treatment with escitalopram lasted for a minimum of 16 weeks (20 mg/day), with an optional continuation for a 6-month follow-up period. Repeated measures ANOVA with modified intent-to-treat analyses were conducted. Results showed significant time effects on all measures for both treatment conditions, although no significant group or time × group effects. The results indicated that both treatments were effective in the short term (effect sizes (ES) ranging from 0.45 to 0.91 for the CBT group and 0.27 to 0.72 for the escitalopram+CBT group), and that adding CBT to escitalopram had no additional statistically significant effect (between-group ES of 0.11 and 0.29 for primary outcome measures at 16-weeks post-treatment).     

Brother correlations in earnings in Denmark, Finland, Norway and Sweden compared to the United States

The correlation in economic status among siblings is a useful “omnibus measure” of the overall impact of family and community factors on adult economic status. In this study we compare brother correlations in long-run (permanent) earnings between the United States, on one hand, and the Nordic countries (Denmark, Finland, Norway and Sweden) on the other. Our base case results, based on very similar sample criteria and definitions for all countries, show that this correlation is above 0.40 in the United States and in the range 0.14–0.26 in the Nordic countries. Even though these results turn out to be somewhat sensitive to some assumptions that have to be made, we conclude that the family and community factors are more important determinants of long-run earnings in the United States than in the Nordic countries. Received: 27 July 2000/Accepted: 7 March 2001 All correspondence to: Anders Bj?rklund. Comments from two referees, conference participants at ESPE2000 and the Canadian Employment Research Forum, seminar participants in Aarhus, Uppsala, Bonn, and Stockholm are gratefully acknowledged. We thank NOS-S for financial support. The Swedish data collection was also supported by HSFR and SFR. The Finnish data were obtained with support from the Yrj? Jahnsson Foundation. We thank Tom Erik Aab? for preparing the Norwegian data, and Esben Agerbo for computational assistance with the Danish data. Responsible editor: John F. Ermisch.     

Is Social Capital a Good Concept?

This paper explores whether the concept of social capital as popularized by Robert Putnam is a good social science concept. Taking Gerring’s work on concept evaluation as the starting point, the paper first presents a set of criteria for conceptual ‘goodness’ and discusses how social capital performs on these criteria. It is argued that social capital eventually may be a good concept if it can be shown empirically to be a unidimensional concept. An empirical section therefore explores the validity of the unidimensionality assumption and rejects it in four separate tests at both the individual and aggregate level. We conclude that even if social capital has been a remarkably productive idea, it is not a good concept as most popular conceptualizations define social capital as several distinct phenomena or as phenomena that already have been conceptualized under other labels.     

Content validity and utility of the Assessment of Work Performance (AWP)

In the area of work rehabilitation, many decisions about future interventions for the client are based on the results of various kinds of assessments. Therefore, it is important that the assessment instruments used are adequate, useful, and reliable. The purpose of this study was to investigate the content validity and utility of the instrument Assessment of Work Performance (AWP) which is used to assess an individual's observable (working) skills during work performance, i.e. how efficient and appropriate a client performs a work activity. A questionnaire was answered by 67 respondents who used the AWP in various work rehabilitation settings in Sweden. The result indicates content validity and utility for the AWP that supports further testing of the instrument.     

Sensitivity analyses for the principal ignorability assumption using multiple imputation

In the context of clinical trials, there is interest in the treatment effect for subpopulations of patients defined by intercurrent events, namely disease-related events occurring after treatment initiation that affect either the interpretation or the existence of endpoints. With the principal stratum strategy, the ICH E9(R1) guideline introduces a formal framework in drug development for defining treatment effects in such subpopulations. Statistical estimation of the treatment effect can be performed based on the principal ignorability assumption using multiple imputation approaches. Principal ignorability is a conditional independence assumption that cannot be directly verified; therefore, it is crucial to evaluate the robustness of results to deviations from this assumption. As a sensitivity analysis, we propose a joint model that multiply imputes the principal stratum membership and the outcome variable while allowing different levels of violation of the principal ignorability assumption. We illustrate with a simulation study that the joint imputation model-based approaches are superior to naive subpopulation analyses. Motivated by an oncology clinical trial, we implement the sensitivity analysis on a time-to-event outcome to assess the treatment effect in the subpopulation of patients who discontinued due to adverse events using a synthetic dataset. Finally, we explore the potential usage and provide interpretation of such analyses in clinical settings, as well as possible extension of such models in more general cases.