Estimating the propagation rate of a viral infection of potato plants via mixtures of regressions

A problem arising from the study of the spread of a viral infection among potato plants by aphids appears to involve a mixture of two linear regressions on a single predictor variable. The plant scientists studying the problem were particularly interested in obtaining a 95% confidence upper bound for the infection rate. We discuss briefly the procedure for fitting mixtures of regression models by means of maximum likelihood, effected via the EM algorithm. We give general expressions for the implementation of the M-step and then address the issue of conducting statistical inference in this context. A technique due to T. A. Louis may be used to estimate the covariance matrix of the parameter estimates by calculating the observed Fisher information matrix. We develop general expressions for the entries of this information matrix. Having the complete covariance matrix permits the calculation of confidence and prediction bands for the fitted model. We also investigate the testing of hypotheses concerning the number of components in the mixture via parametric and 'semiparametric' bootstrapping. Finally, we develop a method of producing diagnostic plots of the residuals from a mixture of linear regressions.     

Energy and U.K. agriculture

This paper makes the point that although U.K. agriculture has become more efficient in many ways, it has become less efficient in its use of energy. Moreover, although farming utilises less than 3 per cent of national power energy consumption and produces over 40 per cent of the nation's food, there are no predominant users of energy in the U.K. Thus small savings in each individual industry, including agriculture, must be effected. How this can be achieved is discussed. But the paper concludes that it may well take another ‘energy crisis’ before farmers and growers respond by modifying their production systems accordingly.     

Television Coverage of State Government

An empirical analysis of 3,334 state and local television newsstories in 10 cities clarifies the reluctance of commercialtelevision newscasters to cover state government. Contrary towhat many television news directors assert, television's minimalattention to state government cannot be attributed to an allegednegative relationship between state government and newscastratings. Rather, it appears to stem from the high cost of obtainingfilmed coverage of state government in a timely fashion.     

Statistical simulations on the BBC microcomputer: significance tests of the pseudo-random number generator

Statistical tests of significance are carried out on the feedback shift register pseudo-random number generator employed on the BBC microcomputer. The tests are based on the practicalities of using a microcomputer in simulations for statistical education. The results indicate that the generator is not universally acceptable in this role.     

Avian Influenza in Vietnam: Chicken‐Hearted Consumers?

This study, based on quantitative and qualitative surveys conducted from July 2004 to September 2005, examines the perceptions of Hanoi consumers and their reactions to the Avian Influenza epizootic (H5N1). Hanoi consumers clearly link the risk of human contamination by the virus to the preparation and ingestion of poultry. During the first crisis, consumers reacted quickly and intensely (74% of them had already stopped eating poultry in January 2004). Nevertheless, once the crisis abated, they quickly resumed their consumption of poultry. This behavior corresponds to the pattern described by empirical studies of other crises, such as BSE. What is more surprising is the speed with which the different steps of this common pattern succeeded one another. It may be explained by a rapid decrease in risk anxiety. A logit model shows that, soon after the beginning of the crisis, AI risk anxiety was tempered by confidence in the information and recommendations issued by the government concerning AI and, in the long term, by a high perceived self-efficiency to deal with AI. Indeed, not only has poultry consumption been affected in terms of the quantity consumed, but alternative ways of selecting and preparing poultry have also been adopted as anti-risk practices. Risk communication strategies should take this into account, and rely on a previous assessment of consumer practices adopted to deal with the risk.     

Biological mothers' grief: the postadoptive experience in open versus confidential adoption

Advocates of open adoption believe that it lightens and in some cases alleviates the grieving process after relinquishment. Advocates of confidential adoption, however, believe that open adoption limits and denies the grieving process that must take place for subsequent life adjustment. A study of 59 women who had placed a child for adoption through an agency--18 via open adoption and 41 via confidential adoption--revealed significant differences between the two groups on five subscales of the research instruments. Implications of this pioneer study in this new practice area are discussed and further research suggested.     

A Sociological Alternative to the Psychiatric Conceptualization of Mental Suffering

Uncovering both the structural causes and experiences of suffering is a central sociological endeavor. Sociologists study many different kinds of suffering; after all, strife is experienced both physically and emotionally, because of internal factors such as illness, due to external factors such as trauma, and as a result of economic, political or natural environments. In this paper, I address one form of suffering: mental suffering. In particular, I describe the medicalization of mental suffering in biological psychiatry, which focuses on the genetic factors of illness and equates mental suffering with mental illness. The psychiatric concept of mental illness highlights the continuing, crucial role for sociology in both understanding the experience and identifying the structural roots of suffering. Since the dominant conceptualization of mental suffering is as a medical concept, it is vital for sociology to offer alternative explanations and contribute to a multidimensional analysis. The roots of mental suffering are much more than biological; social comparison, social inequality, and other social stressors are equally important etiological considerations. Therefore, a true understanding of mental suffering requires multiple perspectives, and sociological constructs guard against a total medicalization of mental suffering.