Use of Professional and Informal Support by Black Men with Mental Disorders

This study utilized data from the National Survey of American Life to investigate the use of professional services and informal support among African American and Caribbean black men with a lifetime mood, anxiety, or substance use disorder. Thirty-three percent used both professional services and informal support, 14% relied on professional services only, 24% used informal support only, and 29% did not seek help. African American men were more likely than to rely on informal support alone. Having co-occurring mental and substance disorders, experiencing an episode in the past 12 months, and having more people in the informal network increased the likelihood of using professional services and informal supports. Marital status, age, and socioeconomic status were also significantly related to help-seeking. The results suggests potential unmet need. However, the reliance on informal support also suggests a strong protective role that informal networks play in the lives of black men.     

A Simple Toxicokinetic Model Exhibiting Complex Dynamics and Nonlinear Exposure Response

Uncertainty in model predictions of exposure response at low exposures is a problem for risk assessment. A particular interest is the internal concentration of an agent in biological systems as a function of external exposure concentrations. Physiologically based pharmacokinetic (PBPK) models permit estimation of internal exposure concentrations in target tissues but most assume that model parameters are either fixed or instantaneously dose-dependent. Taking into account response times for biological regulatory mechanisms introduces new dynamic behaviors that have implications for low-dose exposure response in chronic exposure. A simple one-compartment simulation model is described in which internal concentrations summed over time exhibit significant nonlinearity and nonmonotonicity in relation to external concentrations due to delayed up- or downregulation of a metabolic pathway. These behaviors could be the mechanistic basis for homeostasis and for some apparent hormetic effects.     

An Asymptotic Analysis of the Logrank Test

Asymptotic expansions for the null distribution of the logrank statistic and its distribution under local proportional hazards alternatives are developed in the case of iid observations. The results, which are derived from the work of Gu (1992) and Taniguchi (1992), are easy to interpret, and provide some theoretical justification for many behavioral characteristics of the logrank test that have been previously observed in simulation studies. We focus primarily upon (i) the inadequacy of the usual normal approximation under treatment group imbalance; and, (ii) the effects of treatment group imbalance on power and sample size calculations. A simple transformation of the logrank statistic is also derived based on results in Konishi (1991) and is found to substantially improve the standard normal approximation to its distribution under the null hypothesis of no survival difference when there is treatment group imbalance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inference in model-based cluster analysis

A new approach to cluster analysis has been introduced based on parsimonious geometric modelling of the within-group covariance matrices in a mixture of multivariate normal distributions, using hierarchical agglomeration and iterative relocation. It works well and is widely used via the MCLUST software available in S-PLUS and StatLib. However, it has several limitations: there is no assessment of the uncertainty about the classification, the partition can be suboptimal, parameter estimates are biased, the shape matrix has to be specified by the user, prior group probabilities are assumed to be equal, the method for choosing the number of groups is based on a crude approximation, and no formal way of choosing between the various possible models is included. Here, we propose a new approach which overcomes all these difficulties. It consists of exact Bayesian inference via Gibbs sampling, and the calculation of Bayes factors (for choosing the model and the number of groups) from the output using the Laplace–Metropolis estimator. It works well in several real and simulated examples.     

Asymmetric generalizations of symmetric univariate probability distributions obtained through quantile splicing

Abstract

Balakrishnan et al. proposed a two-piece skew logistic distribution by making use of the cumulative distribution function (CDF) of half distributions as the building block, to give rise to an asymmetric family of two-piece distributions, through the inclusion of a single shape parameter. This paper proposes the construction of asymmetric families of two-piece distributions by making use of quantile functions of symmetric distributions as building blocks. This proposition will enable the derivation of a general formula for the L-moments of two-piece distributions. Examples will be presented, where the logistic, normal, Student’s t(2) and hyperbolic secant distributions are considered.     

Make way for the wealthy? Autonomous vehicles,markets in mobility,and social justice

ABSTRACT

The development of a ‘mobility as a service’ model for accessing urban transport via autonomous vehicles may be expected to have far-reaching implications for the economics of road transport. In particular, it would offer a new opportunity to price access to the roads in accordance with the principles of the free market. Once people are paying for mobility on the roads on a ‘per trip’ basis, it will be possible to offer different levels of access – and service – at different prices. According to hegemonic ideas in the transport planning and economics literature the introduction of such a ‘market in mobility’ would be an economically efficient way of allocating access to the scarce good of space on the roads. In this paper we draw attention to a number of ethical and political challenges to the appropriateness of the use of such a pricing mechanism in the context of urban mobility.     

A Social Cognitive Framework for Career Choice Counseling

This article extends social cognitive career theory by suggesting how several of its major hypotheses can be applied to counseling persons with career choice difficulties. Several theory-derived counseling strategies are described that can be used to assist clients in developing a broad array of career options, analyzing and overcoming barriers to career choice, and counteracting choice-limiting self-efficacy beliefs. Each strategy is illustrated with a case example. Future research needs related to the counseling model are discussed.     

Evolution of recent economic-demographic modeling: A synthesis

This paper develops a flexible framework for modeling population's role in economic growth by assessing and extending a rendering suggested by several Harvard economists. Our framework includes a ``productivity' model explaining output-per-worker growth and a ``translation' model translating that growth into per-capita terms. We specify a core economic model and several ``enriched' demographic variants that include dependency, size, and density. Regressions using a cross-country panel spanning the period 1960-1995 reveal that combined impacts of demographic change have accounted for approximately 20% of per capita output growth impacts, with larger shares in Asia and Europe. An earlier draft of this paper was presented at a conference on ``Population Change, Labor Market Transition and Economic Development in Asia,' Institute of Economics, Academia Sinica, Taipei, Taiwan, 6–9 December 2002. A pre-publication version of this paper will be presented at a joint conference (by COE/JEPA) entitled ``Towards a new economic paradigm: Declining population growth, labor market transition and economic development under globalization,' held at the Awaji Yumebutai International Conference Center, Kobe, Japan, 17–19 December 2005. We have benefited from comments by Michelle Connolly, Andrew Mason, Pietro Peretto, Warren Sanderson, Alessandro Tarozzi, Jeffrey Williamson, and two anonymous referees. Responsible editor: Junsen Zhang.