Sampling from multimodal distributions using tempered transitions

I present a new Markov chain sampling method appropriate for distributions with isolated modes. Like the recently developed method of simulated tempering, the tempered transition method uses a series of distributions that interpolate between the distribution of interest and a distribution for which sampling is easier. The new method has the advantage that it does not require approximate values for the normalizing constants of these distributions, which are needed for simulated tempering, and can be tedious to estimate. Simulated tempering performs a random walk along the series of distributions used. In contrast, the tempered transitions of the new method move systematically from the desired distribution, to the easily-sampled distribution, and back to the desired distribution. This systematic movement avoids the inefficiency of a random walk, an advantage that is unfortunately cancelled by an increase in the number of interpolating distributions required. Because of this, the sampling efficiency of the tempered transition method in simple problems is similar to that of simulated tempering. On more complex distributions, however, simulated tempering and tempered transitions may perform differently. Which is better depends on the ways in which the interpolating distributions are deceptive.     

Wither or whither London? An application of industry structure analysis

Industry structure analysis provides a tool for managers and leaders to more clearly understand the context in which day-by-day decisions are to be taken. It encourages a systematic analysis of ‘whither an enterprise?’ in the sense of ‘in what direction’ and ‘wither an enterprise?’ in the sense of ‘to what purpose’. Industry structure analysis applied to London reveals those forces which may doom current approaches to the solution to inner city problems to early failure and suggests new areas for the application of effort. As we enter a decade in which economic, political and social upheaval will be the norm, such a tool could be of use in helping managers in other enterprises to chart a surer course through uncertainty.     

From the case files: reconstructing a history of involuntary sterilisation

Although it is well-known that numerous jurisdictions in North America adopted legislation in the first half of the twentieth century allowing the involuntary sterilisation of persons diagnosed as 'mentally deficient', analysis of its implementation has rarely progressed beyond the examination of the legislation and the aggregate data presented in official reports. In this paper we analyse the case files of the Eugenics Board for the province of Alberta. The primary sources contained in these files reveal something of the hand of officialdom: clinical reports, diagnoses, test results and 'patient' history. The files allow glimpses of the individual stories of those who were sterilised. Much more directly, they present the case made for involuntary sterilisation from professional, often custodial perspectives. Thus, they afford us a richer understanding of the culture which sanctioned the practice of forcible sterilisation.     

A sequential scheme to estimate the optimal age replacement policy

Consider a system which is subject to failure and must be replaced when this occurs. If it costs less to replace the system in advance before failure, it may be advantageous to use an age replacement policy. However, the optimal age to replace the system is unknown if the underlying failure distribution is unknown. This paper develops a scheme to update the current estimate of the optimal age replacement policy in an on-line fashion and simultaneously controlling costs by reducing system failures.     

Interpretive claims and methodological warrant in small-number qualitative,longitudinal research

This article discusses issues of methodological warrant in a qualitative, longitudinal study with only a small number of subjects. The 12 to 18 Project was designed to contribute to research on gender, class and schooling. The rationale for a design using only 26 students spread between four schools is explained. It is argued that even with small-number research, issues of selection and comparison are important--but emphasis on techniques of data-treatment and comparison is misplaced. The meaningfulness and contribution of studies of this type lie in multiple acts of design, comparison, reflexive interpretation and dialogue with the broader field, and the more that such studies emphasize technical analytic procedures, the more they undermine their warrant to be anything other than a report on a small sample. Illustrations of interpretations of the data and from the data are given.     

Science for people who don't want to know about science

Newspapermen and scientists are both in pursuit of the truth. That's about all they have in common. Scientists tend to be very serious about trivial things. Journalists are often trivial about very serious things. It may not be possible to square this circle.     

Residential Respite Care: The Caregiver's Last Resort

Understanding the beliefs that caregivers of people with dementia have in regard to the use of residential respite may inform strategies to address low service utilisation. In this article, the application of theory in qualitative research with 36 caregivers provides insight into why most delay service use. Although some believe that service use may increase caregiving longevity, others position service use in conflict with normative values, and may hold beliefs that negative outcomes will result from utilisation. To address caregivers' beliefs to support service use, improvements are required to service promotion, as well as to models of care.     

SUCCESSFUL STEPFAMILY THERAPY: CLIENTS' PERSPECTIVES

This study examined responses from 267 adults who sought therapy because of stepfamily issues. Concerns identified at the initiation of therapy and those aspects of therapy found to be helpful or unhelpful to stepfamily adjustment were investigated. Results indicated that issues around parenting/stepparenting and stepfamily functioning were of greatest concern at the initiation of therapy. Affective support, clarification of issues, and the process and structure of therapy were most frequently reported as helpful. The therapist's perceived lack of training and skill in treating stepfamily issues was reported most frequently as unhelpful in therapy.