A modified common factor model for modelling mortality jointly for both sexes

Journal of Population Research - There is an increasing attention on the joint modelling of multiple populations. Populations are related in several ways, such as neighbouring countries, females...     

The ‘right time’ – negotiating the timing of interviews with vulnerable young people

Participant retention is a key factor in determining the success of longitudinal research. Challenges in re-locating and retaining participants over the long term are major issues for researchers working with young people who face adversity and experience frequent changes in circumstances. This article reports on a study of vulnerable young people and their transition into adulthood. Rather than the more conventional schedule-based approach to locating and re-interviewing young people, a relational process, the ‘right time’ framework, was used to facilitate young people's involvement in the study. Embedded in the ‘right time’ framework is recognition of the diverse and fluctuating circumstances that shape young people's availability for interviews. Several case examples are considered which amplify the way that the ‘right time’ framework allowed the research to navigate around these circumstances. The case examples highlight the value young people attached to being involved in the research, the influence on the ‘right time’ of wider relational tensions for young people and the need to negotiate researcher status as a different sort of adult. The ‘right time’ framework contributed to a high retention rate in the study generating a more representative sample and enhancing the subsequent data analysis by providing valuable insights into the lives of these vulnerable young people.     

A semi-parametric approach to robust parameter design

Parameter design or robust parameter design (RPD) is an engineering methodology intended as a cost-effective approach for improving the quality of products and processes. The goal of parameter design is to choose the levels of the control variables that optimize a defined quality characteristic. An essential component of RPD involves the assumption of well estimated models for the process mean and variance. Traditionally, the modeling of the mean and variance has been done parametrically. It is often the case, particularly when modeling the variance, that nonparametric techniques are more appropriate due to the nature of the curvature in the underlying function. Most response surface experiments involve sparse data. In sparse data situations with unusual curvature in the underlying function, nonparametric techniques often result in estimates with problematic variation whereas their parametric counterparts may result in estimates with problematic bias. We propose the use of semi-parametric modeling within the robust design setting, combining parametric and nonparametric functions to improve the quality of both mean and variance model estimation. The proposed method will be illustrated with an example and simulations.     

Population Policy in Early Victorian England

This paper argues that the generally-held belief that there was no population policy in Great Britain during its fertility transition is incorrect. There were, in fact, clear and implicit and explicit policies in place by the early 19th Century which aimed at reducing population growth. These were negative, involving elimination of family allowances (the famous Poor Laws), and also positive, through subsidised emigration and ``transportation' of felons to the colonies. Moreover, a changed ``ideation' on the part of the nation's political, intellectual and spiritual leaders, changed norms about marriage and child-bearing, raising sharply the perceived economic and psychic cost of children. Lacking acceptable means to control pregnancies, many working class women resorted to abortion, infanticide and child abandonment to reduce their family size. The policy's actual impact on overall fertility is uncertain but it did constitute a deliberate attempt by society to affect demographic behaviour and outcomes.     

Children's involvement in their parents' divorce: implications for practice

The paper reports findings from a research study that explored children's experience of divorce. It shows that children experience parental divorce as a crisis in their lives but that they are able to mobilise internal and external resources to regain a new point of balance. In doing so, children demonstrate the degree to which they are active and competent participants in the process of family dissolution. The implications of the data are then considered in relation to engaging with children involved in divorce and in relation to some of the cultural presumptions that might militate against hearing what they have to say about their experiences. Copyright © 2002 John Wiley & Sons, Ltd.     

Physiologically Based Liver Modeling and Risk Assessment

Because of the inherent complexity of biological systems, there is often a choice between a number of apparently equally applicable physiologically based models to describe uptake and metabolism processes in toxicology or risk assessment. These models may fit the particular data sets of interest equally well, but may give quite different parameter estimates or predictions under different (extrapolated) conditions. Such competing models can be discriminated by a number of methods, including potential refutation by means of strategic experiments, and their ability to suitably incorporate all relevant physiological processes. For illustration, three currently used models for steady-state hepatic elimination--the venous equilibration model, the parallel tube model, and the distributed sinusoidal perfusion model--are reviewed and compared with particular reference to their application in the area of risk assessment. The ability of each of the models to describe and incorporate such physiological processes as protein binding, precursor-metabolite relations and hepatic zones of elimination, capillary recruitment, capillary heterogeneity, and intrahepatic shunting is discussed. Differences between the models in hepatic parameter estimation, extrapolation to different conditions, and interspecies scaling are discussed, and criteria for choosing one model over the others are presented. In this case, the distributed model provides the most general framework for describing physiological processes taking place in the liver, and has so far not been experimentally refuted, as have the other two models. These simpler models may, however, provide useful bounds on parameter estimates and on extrapolations and risk assessments.     

Institutional Voids,Economic Adversity and Inter‐firm Cooperation in an Emerging Market: The Mediating Role of Government R&D Support

This paper examines the mediating mechanism of the relationship between institutional voids (IVs) and inter‐firm cooperation and the moderating role of economic adversity in the context of small and medium‐sized enterprises (SMEs) based in emerging markets. The hypotheses are tested using time‐lagged survey data from 214 SMEs in Ghana. The findings provide support for the hypotheses by showing that: (1) IVs positively influence the use of government research and development (R&D) support; (2) the use of government R&D support mediates the relationship between IVs and inter‐firm cooperation; and (3) economic adversity positively moderates the relationship between IVs and the use of government R&D support. The findings contribute to understanding the role of IVs in inter‐firm cooperation. The wider implications for theory and practice are examined.     

West and Central Africa

This article reviews scientific and other literature during the 1990s that links migration and mobility with the spread of sexually transmitted diseases (STDs), including HIV/AIDS. The focus is on key population groups linked to the spread of HIV and STDs in West and Central Africa: migrant laborers, truck drivers, itinerant traders, commercial sex workers (CSWs), and refugees. Countries with high emigration and immigration tend to have high levels of HIV infection, with the exception of Senegal. The main destination of immigrants are Senegal, Nigeria, and Cote d'Ivoire in West Africa and Cameroon, Congo, Gabon, and Congo in Central Africa. The risk of infection and the spread of HIV is variable among migrants. There is little in the literature that substantiates hypotheses about the strong association between migration and HIV-positive status. Information is needed on the duration, frequency of return visits, living conditions, sexual activities with multiple partners, and information before departure, along the routes, at final destination, and at the time of returns. Action-based research in five West African countries (Burkina Faso, Cote d'Ivoire, Mali, Niger, and Senegal) should produce results in late 1998. Comparable studies in Central Africa are unknown. Regional studies should be complemented by local studies. Prevention would benefit from studies on the relative size of these five population groups by geographic location.