Quantifying uncertainty in the biospheric carbon flux for England and Wales

Summary.  A crucial issue in the current global warming debate is the effect of vegetation and soils on carbon dioxide (CO₂) concentrations in the atmosphere. Vegetation can extract CO₂ through photosynthesis, but respiration, decay of soil organic matter and disturbance effects such as fire return it to the atmosphere. The balance of these processes is the net carbon flux. To estimate the biospheric carbon flux for England and Wales, we address the statistical problem of inference for the sum of multiple outputs from a complex deterministic computer code whose input parameters are uncertain. The code is a process model which simulates the carbon dynamics of vegetation and soils, including the amount of carbon that is stored as a result of photosynthesis and the amount that is returned to the atmosphere through respiration. The aggregation of outputs corresponding to multiple sites and types of vegetation in a region gives an estimate of the total carbon flux for that region over a period of time. Expert prior opinions are elicited for marginal uncertainty about the relevant input parameters and for correlations of inputs between sites. A Gaussian process model is used to build emulators of the multiple code outputs and Bayesian uncertainty analysis is then used to propagate uncertainty in the input parameters through to uncertainty on the aggregated output. Numerical results are presented for England and Wales in the year 2000. It is estimated that vegetation and soils in England and Wales constituted a net sink of 7.55 Mt C (1 Mt C = 10¹² g of carbon) in 2000, with standard deviation 0.56 Mt C resulting from the sources of uncertainty that are considered.     

Do Lets Work?

This study aims to uncover some of the reasons for differences in attitudes towards family‐friendly and equal opportunities (EO) policies for women between senior and junior staff and between male and female staff. This in‐depth case study of a multi‐national corporation in Hong Kong that included a survey questionnaire, interviews and participant observation suggests four categories of female employees according to their approach to EO: advocators, supporters, outsiders and rejecters. The approach adopted was dependent on the woman's level of empathy towards the situation of working women and the extent of her career ambition. Four categories of male employees can also be classified depending on their level of empathy towards women's situation (similar to women's case) and their extent of career satisfaction (in contrast to women's career ambition), namely, antagonists, outsiders, fence‐sitters and sympathizers. Women at higher levels were less supportive of EO than women at lower levels. No such clear relationship between organizational level and attitudes towards EO was observed among men. In Hong Kong, female managers had little expectation that their organization would be family‐friendly and women workers who consciously chose to balance work and family accepted that it meant fewer promotional chances. No such self‐adjusted depressed ambition was observed among men.     

The Migration–Development Nexus: Evidence and Policy Options

Migration and development are linked in many ways – through the livelihood and survival strategies of individuals, households, and communities; through large and often well–targeted remittances; through investments and advocacy by migrants, refugees, diasporas and their transnational communities; and through international mobility associated with global integration, inequality, and insecurity. Until now, migration and development have constituted separate policy fields. Differing policy approaches that hinder national coordination and international cooperation mark these fields. For migration authorities, the control of migration flows to the European Union and other OECD countries are a high priority issue, as is the integration of migrants into the labour market and wider society. On the other hand, development agencies may fear that the development policy objectives are jeopardized if migration is taken into consideration. Can long–term goals of global poverty reduction be achieved if short–term migration policy interests are to be met? Can partnership with developing countries be real if preventing further migration is the principal European migration policy goal? While there may be good reasons to keep some policies separate, conflicting policies are costly and counter–productive. More importantly, there is unused potential in mutually supportive policies, that is, the constructive use of activities and interventions that are common to both fields and which may have positive effects on poverty reduction, development, prevention of violent conflicts, and international mobility. This paper focuses on positive dimensions and possibilities in the migration–development nexus. It highlights the links between migration, development, and conflict from the premise that to align policies on migration and development, migrant and refugee diasporas must be acknowledged as a development resource.     

Book Review: Strategic Management for Voluntary Nonprofit Organizations,by Roger Courtney. Routledge,New York, 2002

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations -     

Bayesian analysis of elapsed times in continuous‐time Markov chains

The authors consider Bayesian analysis for continuous‐time Markov chain models based on a conditional reference prior. For such models, inference of the elapsed time between chain observations depends heavily on the rate of decay of the prior as the elapsed time increases. Moreover, improper priors on the elapsed time may lead to improper posterior distributions. In addition, an infinitesimal rate matrix also characterizes this class of models. Experts often have good prior knowledge about the parameters of this matrix. The authors show that the use of a proper prior for the rate matrix parameters together with the conditional reference prior for the elapsed time yields a proper posterior distribution. The authors also demonstrate that, when compared to analyses based on priors previously proposed in the literature, a Bayesian analysis on the elapsed time based on the conditional reference prior possesses better frequentist properties. The type of prior thus represents a better default prior choice for estimation software.     

Distal and Proximal Factors in Domestic Violence: A Test of an Integrated Model

We employed 4,095 couples from both waves of the National Survey of Families and Households (NSFH) to test a model of couple violence drawn from several theoretical perspectives. The outcome distinguishes among nonviolent couples and those experiencing either physical aggression or intense male violence. According to the model, background characteristics of couples are related to relationship stressors, which affect the risk of violence via their tendency to promote verbal conflict. Considerable support for the model was found. Couples were at higher risk for one or both forms of violence if they were younger at union inception, had been together for less time, were both in their first union, had only one partner who was employed, had a nontraditional woman paired with a traditional man, had at least one partner who abused substances, had more children, had more frequent disagreements, exhibited a more hostile disagreement style, or lived in an economically disadvantaged neighborhood. Moreover, the effects of stressors such as the number of children and couples' employment status disparities appear to be mediated by disagreement frequency and disagreement style.     

Human Salmonellosis: Estimation of Dose-Illness from Outbreak Data

The quantification of the relationship between the amount of microbial organisms ingested and a specific outcome such as infection, illness, or mortality is a key aspect of quantitative risk assessment. A main problem in determining such dose-response models is the availability of appropriate data. Human feeding trials have been criticized because only young healthy volunteers are selected to participate and low doses, as often occurring in real life, are typically not considered. Epidemiological outbreak data are considered to be more valuable, but are more subject to data uncertainty. In this article, we model the dose-illness relationship based on data of 20 Salmonella outbreaks, as discussed by the World Health Organization. In particular, we model the dose-illness relationship using generalized linear mixed models and fractional polynomials of dose. The fractional polynomial models are modified to satisfy the properties of different types of dose-illness models as proposed by Teunis et al . Within these models, differences in host susceptibility (susceptible versus normal population) are modeled as fixed effects whereas differences in serovar type and food matrix are modeled as random effects. In addition, two bootstrap procedures are presented. A first procedure accounts for stochastic variability whereas a second procedure accounts for both stochastic variability and data uncertainty. The analyses indicate that the susceptible population has a higher probability of illness at low dose levels when the combination pathogen-food matrix is extremely virulent and at high dose levels when the combination is less virulent. Furthermore, the analyses suggest that immunity exists in the normal population but not in the susceptible population.     

The Poverty Reduction Strategy Approach Six Years On: An Examination of Principles and Practice in Uganda

It is over six years since the World Bank and the IMF started promoting a PRS approach to development management in low‐income countries. The 2005 review endorsed the approach, but highlighted the need for a renewed focus on the principles underpinning it: country ownership; results orientation; comprehensiveness; partnership focus; and long‐term outlook. Uganda is often hailed as one of the best PRS performers. This article finds that Uganda's Poverty Eradicaton Action Plan (PEAP) has brought significant gains to development management, but that its performance against several of the PRS principles is disappointing. A return to these principles could improve the practice of the government and development partners around the PEAP – a finding likely to be applicable to many countries implementing a PRS.     

A Numerical Solution to the Nonhomogeneous Two-Stage MVK Model of Cancer

In this article, we describe a straightforward method for solving the probability of at least one malignant cell by time t, and the associated hazard function, in the general (i.e., nonhomogeneous) two-stage Moolgavkar-Venzon-Knudson (MVK) model of cancer. The method consists of solving four coupled ordinary differential equations derived from the Kolmogorov backward equations for this process. The relationship of this method to previously proposed solutions is discussed.