Random regression models for human immunodeficiency virus ribonucleic acid data subject to left censoring and informative drop-outs

Objectives in many longitudinal studies of individuals infected with the human immunodeficiency virus (HIV) include the estimation of population average trajectories of HIV ribonucleic acid (RNA) over time and tests for differences in trajectory across subgroups. Special features that are often inherent in the underlying data include a tendency for some HIV RNA levels to be below an assay detection limit, and for individuals with high initial levels or high ranges of change to drop out of the study early because of illness or death. We develop a likelihood for the observed data that incorporates both of these features. Informative drop-outs are handled by means of an approach previously published by Schluchter. Using data from the HIV Epidemiology Research Study, we implement a maximum likelihood procedure to estimate initial HIV RNA levels and slopes within a population, compare these parameters across subgroups of HIV-infected women and illustrate the importance of appropriate treatment of left censoring and informative drop-outs. We also assess model assumptions and consider the prediction of random intercepts and slopes in this setting. The results suggest that marked bias in estimates of fixed effects, variance components and standard errors in the analysis of HIV RNA data might be avoided by the use of methods like those illustrated.     

The Economic Partnership Agreements: Rationale,Misperceptions and Non‐trade Aspects

The European Union and the African, Caribbean and Pacific (ACP) countries entered a new era in 2008. The Cotonou trade regime and the WTO waiver legitimising it have expired, and the long anticipated, and much debated, move to Economic Partnership Agreements (EPAs) has begun. This article explains the background and analyses the ‘alternatives’ to EPAs, in order to tackle common misperceptions. Moving on from what has been the focus of debates, namely, the reciprocal liberalisation required under WTO rules, it sheds some light on the non‐goods trade aspects of EPAs which, while integral to economic policy, are inherently hard to quantify and often skimmed over in existing studies or addressed in ideological terms.     

Politics,Plurality and Problemsheds: A Strategic Approach for Reform of Agricultural Water Resources Management

Starting from the assessment that past efforts at reform in agricultural water management in developing countries have achieved very little, this article argues that a fundamental change is required in the approach to policy and institutional transformation if the present deadlock in the internalisation of ecological sustainability, human development/poverty alleviation and democratic governance into the ‘core business’ of water bureaucracies is to be overcome. ‘Social engineering’ approaches need to be replaced by ‘strategic action’ approaches that acknowledge the inherently political character and the plurality of actors, institutions and objectives of water management — a perspective operationalised here around the notions of ‘problemshed’ and ‘issue network’.     

Globalisierung und die Veränderung sozialer Ungleichheiten in modernen Gesellschaften

This article deals with the effects of globalization on individual life courses and employment careers and the resulting changes in patterns of social inequality in modern societies. Empirically, we draw back to results from the international research project GLOBALIFE which studied the effects of globalization on modern life courses for the first time. The results show that the effects of globalization on individual life courses show marked differentiation with regards to specific life course phases: while especially the employment of mid-career men remained considerably stable under globalization, the careers of young adults, mid-career women as well as late-career workers underwent significant alterations. At the same time, results from the GLOABLIFE study indicate that the changes induced by globalization have not yet led to identical results at the national level. Globalization appears to be differentially filtered by deeply embedded and path-dependent national institutions. These “institutional packages” entail variable forms of labour market “flexibilisation” which themselves differentially shape patterns of social inequality in modern societies: While Scandinavian countries have largely succeeded in limiting an increase in social inequality under globalization through active public welfare engagement, globalization has led to a significant amplification of social inequalities in other regime types, either between labour market insiders and outsiders (in conservative and Southern European countries) or between individuals with different human capital resources (in liberal countries).     

Minimax-variance L- and R-estimators of location

We consider the problem of minimax-variance, robust estimation of a location parameter, through the use of L- and R-estimators. We derive an easily checked necessary condition for L-estimation to be minimax, and a related sufficient condition for R-estimation to be minimax. Those cases in the literature in which L-estimation is known not to be minimax, and those in which R-estimation is minimax, are derived as consequences of these conditions. New classes of examples are given in each case. As well, we answer a question of Scholz (1974), who showed essentially that the asymptotic variance of an R-estimator never exceeds that of an L-estimator, if both are efficient at the same strongly unimodal distribution. Scholz raised the question of whether or not the assumption of strong unimodality could be dropped. We answer this question in the negative, theoretically and by examples. In the examples, the minimax property fails both for L-estimation and for R-estimation, but the variance of the L-estimator, as the distribution of the observation varies over the given neighbourhood, remains unbounded. That of the R-estimator is unbounded.     

A Screening Methodology for the Identification and Ranking of Infrastructure Vulnerabilities Due to Terrorism

The extreme importance of critical infrastructures to modern society is widely recognized. These infrastructures are complex and interdependent. Protecting the critical infrastructures from terrorism presents an enormous challenge. Recognizing that society cannot afford the costs associated with absolute protection, it is necessary to identify and prioritize the vulnerabilities in these infrastructures. This article presents a methodology for the identification and prioritization of vulnerabilities in infrastructures. We model the infrastructures as interconnected digraphs and employ graph theory to identify the candidate vulnerable scenarios. These scenarios are screened for the susceptibility of their elements to a terrorist attack, and a prioritized list of vulnerabilities is produced. The prioritization methodology is based on multiattribute utility theory. The impact of losing infrastructure services is evaluated using a value tree that reflects the perceptions and values of the decisionmaker and the relevant stakeholders. These results, which are conditional on a specified threat, are provided to the decisionmaker for use in risk management. The methodology is illustrated through the presentation of a portion of the analysis conducted on the campus of the Massachusetts Institute of Technology.     

Diesel Engine Exhaust and Lung Cancer Mortality: Time‐Related Factors in Exposure and Risk

To develop a quantitative exposure‐response relationship between concentrations and durations of inhaled diesel engine exhaust (DEE) and increases in lung cancer risks, we examined the role of temporal factors in modifying the estimated effects of exposure to DEE on lung cancer mortality and characterized risk by mine type in the Diesel Exhaust in Miners Study (DEMS) cohort, which followed 12,315 workers through December 1997. We analyzed the data using parametric functions based on concepts of multistage carcinogenesis to directly estimate the hazard functions associated with estimated exposure to a surrogate marker of DEE, respirable elemental carbon (REC). The REC‐associated risk of lung cancer mortality in DEMS is driven by increased risk in only one of four mine types (limestone), with statistically significant heterogeneity by mine type and no significant exposure‐response relationship after removal of the limestone mine workers. Temporal factors, such as duration of exposure, play an important role in determining the risk of lung cancer mortality following exposure to REC, and the relative risk declines after exposure to REC stops. There is evidence of effect modification of risk by attained age. The modifying impact of temporal factors and effect modification by age should be addressed in any quantitative risk assessment (QRA) of DEE. Until there is a better understanding of why the risk appears to be confined to a single mine type, data from DEMS cannot reliably be used for QRA.     

(Im)perishable Pleasure, (In)destructible Desire: Sexual Themes in U.S. and English News Coverage of Male Circumcision and Female Genital Cutting

Under what conditions do sexual pleasure and desire get addressed in news coverage of sexual health issues like female genital cutting (FGC) and male circumcision (MC)? In this study we employed an embodied ethnosexuality approach to analyze sexual themes in 1,902 items published from 1985 to 2009 in 13 U.S. and 8 English newspapers and news magazines. Journalists' discussions of sexual pleasure, desire, control, problems, and practices differed in quantity and quality depending on the practice and nation to which they pertained. News coverage in both nations presented FGC as impeding female sexual pleasure, desire, and activity in ways that reinforce (hetero)sexist understandings of sexuality. The English press depicted MC as diminishing male sexuality, whereas U.S. papers showed it as enhancing male sexuality. These patterns are influenced by, and serve to reinforce, cultural norms of embodiment and ethnosexual boundaries based on gender, race, and nationality. They may, in turn, shape public understandings of FGC and MC as social problems.