Markov-modulated infinite-server queues driven by a common background process

This paper studies a system with multiple infinite-server queues that are modulated by a common background process. If this background process, being modeled as a finite-state continuous-time Markov chain, is in state j, then the arrival rate into the i-th queue is λ_{i, j}, whereas the service times of customers present in this queue are exponentially distributed with mean μ^{? 1}_{i, j}; at each of the individual queues all customers present are served in parallel (thus reflecting their infinite-server nature).

Three types of results are presented: in the first place (i) we derive differential equations for the probability-generating functions corresponding to the distributions of the transient and stationary numbers of customers (jointly in all queues), then (ii) we set up recursions for the (joint) moments, and finally (iii) we establish a central limit theorem in the asymptotic regime in which the arrival rates as well as the transition rates of the background process are simultaneously growing large.     

The Impact of the Within My Reach Relationship Training on Relationship Skills and Outcomes for Low‐Income Individuals

A federal grant was awarded to provide the Within My Reach healthy relationships curriculum to low‐income, at‐risk individuals involved with various social service agencies. The effectiveness of this curriculum was evaluated for 202 participants through measures of training and relationship outcomes pre‐, immediately post‐ and 6 months posttraining. Participants experienced high levels of training satisfaction; significant increases in knowledge, communication/conflict resolution skills, and relationship quality; as well as a trend in the reduction of relationship violence. An important implication of this research is that MFTs may broaden their service delivery to at‐risk individuals by collaborating with community agencies to adapt established relationship enhancement programs, evidence‐based tools, and principles that complement traditional couples therapy.     

Job strain and psychotropic drug use among white-collar workers

The main objective of this study was to measure the association between simultaneous exposure to high psychological demand and low decision latitude at work and the use of psychotropic drugs among white-collar workers. A second objective was to determine whether social support at work modified this association. A cross-sectional study was performed that included 2786 workers from the public sector in the Greater Quebec City area. A self-administered questionnaire was used in order to evaluate psychological demand, decision latitude and social support at work. Psychotropic drug use was measured over a period of 2 days. The prevalence of psychotropic drug use among the participants was found to be 3.9%, even though 20.5% were exposed to job strain. The association between job strain and psychotropic drug use, after adjustment for social support at work, age, gender, education, family income, employment status, occupation, stressful life events, cigarette smoking, alcohol consumption and physical activity, was statistically significant (odds ratio: 4.5, 95% CI 1.7?12.2). Social support did not appear to modify this association. The results of this study suggest that job strain might be a determinant of psychotropic drug use among white collar workers. Social support at work does not appear, however, to modify this association.     

After New Social Movements

This article combines an historical and a sociological approach. Historically, it distinguishes three main moments in the history of social movements since the 1960s. After working-class movements, which corresponded to industrial societies, came the so-called new social movements, in the late 1960s and early 1970s, and these were followed by a third generation of actors deserving a new denomination as alter-globalization activists. Sociologically, this articles analyses the differences between these three figures from the point of view of the identity of the actors, of their relationship to culture, to their adversary, to their subjectivity, or to their framework for action (national or otherwise). The article introduces the concept of anti-movement, which is illustrated with the contemporary cases of ‘global’ anti-movements such as global terrorism or global anti-Semitism.     

Optimal location and capability of oil-spill response facilities for the south coast of Newfoundland

The south coast of Newfoundland (Canada) includes both open sea and semi-enclosed waterways which collectively account for over 20,000 vessel movements annually. Every such movement poses the risk of an oil spill which can endanger the fragile marine life and tourism locales in the region, and is a source of concern to the communities. In an effort to analyze the problem, we present a two-stage stochastic programming approach which tackles both the location and stockpile of equipment at the emergency response facilities. The proposed optimization program was tested on realistic data collected from publicly available reports and through personal communications with emergency response personnel. These data were then varied to solve a number of scenarios which account for the stochastic nature of the problem parameters. Although only two response facilities seem to be appropriate for almost all scenarios, the size of equipment stockpile is a function of both the societal disutility factor and the trade-off between environmental cost and facility and equipment acquisition cost.     

Reliability and validity of the French version of the 18-item Karasek job content questionnaire

Previous studies have shown that job strain, a combination of high psychological demands and low decision latitude, may be involved in the development of cardiovascular diseases and other health outcomes. In 1985, Karasek recommended a standard questionnaire to measure psychological demands (nine items) and job decision latitude (nine items). The internal consistency, factorial validity, discriminant validity, and 1-year stability of the French version of this instrument were evaluated in a population of 8263 white collar workers. Participants filled out the questionnaire during working hours in the context of a larger cardiovascular study. A subgroup of the study population completed the questionnaire again 1 year later (n = 953). Internal consistency was adequate: .74 for men and .73 for women for psychological demands and .83 for men and .81 for women for decision latitude. The results of the factor analysis were consistent with the two dimensions expected from the theory, although some items had high loading on two factors. Variations in the means of psychological demand and decision latitude scores and variations in the prevalence of high job strain by gender, job category, and age support the discriminant validity. These results were generally comparable to those observed with the English version. The percentages of workers remaining, after 1 year, in the same category of psychological demands, decision latitude, and job strain were 86.6, 86.1 and 75.2% respectively. These data provide evidence of the reliability and validity of the French version of these psychological demand and decision latitude scales     

Choosing subsets: a size-independent probabilistic model and the quest for a social welfare ordering

“Subset voting” denotes a choice situation where one fixed set of choice alternatives (candidates, products) is offered to a group of decision makers, each of whom is requested to pick a subset containing any number of alternatives. In the context of subset voting we merge three choice paradigms, “approval voting“ from political science, the “weak utility model” from mathematical psychology, and “social welfare orderings” from social choice theory. We use a probabilistic choice model proposed by Falmagne and Regenwetter (1996) built upon the notion that each voter has a personal ranking of the alternatives and chooses a subset at the top of the ranking. Using an extension of Sen's (1966) theorem about value restriction, we provide necessary and sufficient conditions for this empirically testable choice model to yield a social welfare ordering. Furthermore, we develop a method to compute Borda scores and Condorcet winners from subset choice probabilities. The technique is illustrated on an election of the Mathematical Association of America (Brams, 1988). Received: 18 August 1995 / Accepted: 13 February 1997