Mapping Invasive Species Risks with Stochastic Models: A Cross-Border United States-Canada Application for Sirex noctilio Fabricius

Nonindigenous species have caused significant impacts to North American forests despite past and present international phytosanitary efforts. Though broadly acknowledged, the risks of pest invasions are difficult to quantify as they involve interactions between many factors that operate across a range of spatial and temporal scales: the transmission of invading organisms via various pathways, their spread and establishment in new environments. Our study presents a stochastic simulation approach to quantify these risks and associated uncertainties through time in a unified fashion. We outline this approach with an example of a forest pest recently detected in North America, Sirex noctilio Fabricius. We simulate new potential entries of S. noctilio as a stochastic process, based on recent volumes of marine shipments of commodities from countries where S. noctilio is established, as well as the broad dynamics of foreign marine imports. The results are then linked with a spatial model that simulates the spread of S. noctilio within the geographical distribution of its hosts (pines) while incorporating existing knowledge about its behavior in North American landscapes. Through replications, this approach yields a spatial representation of S. noctilio risks and uncertainties in a single integrated product. The approach should also be appealing to decisionmakers, since it accounts for projected flows of commodities that may serve as conduits for pest entry. Our 30-year forecasts indicate high establishment probability in Ontario, Quebec, and the northeastern United States, but further southward expansion of S. noctilio is uncertain, ultimately depending on the impact of recent international treatment standards for wood packing materials.     

A hybrid genetic algorithm/mathematical programming approach to the multi-family flowshop scheduling problem with lot streaming

This paper presents a hybrid genetic algorithm/mathematical programming heuristic for the n-job, m-machine flowshop problems with lot streaming. The number of sublots for each job and the size of sublots are directly addressed by the heuristic and setups may be sequence-dependent. A new aspect of the problem, the interleaving of sublots from different jobs in the processing sequence, is developed and addressed. Computational results from 12 randomly generated test sets of 24 problems each are presented.     

Ackoff's Fables revisited: stories to inform operational research practice

This paper considers Ackoff's Fables, a set of short stories published by Ackoff in 1978 as guides to creative problem solving. The paper argues that storytelling of this kind contributes usefully to management and MS/OR education, before addressing how such Fables might be interpreted. It is demonstrated, using one of Ackoff's Fables, The Smart Jackass, for illustrative purposes, that interpretation of even apparently straightforward stories such as these is not unambiguous. The Fables can be interpreted in a multitude of different and sometimes contradictory ways, and the truths they might contain are not self-evident. Yet, as the basis for discussion, they still have much to offer as educational tools. The paper concludes with a discussion of literal truth in stories, and presents a classification of story types according to their relationship to literal truth.     

Missing siblings: seeking more adequate social responses

Little is known about the experience of family and friends when a young adult goes missing, less is known about how siblings make sense of the experience. Police assistance to locate the missing person may be sought but there is little recognition of going missing or missingness as a social issue, and there is little or no adequate social response to the needs of those left behind. This paper links knowledge of siblings, loss and grief to an understanding of this phenomenon. It presents the methodology and findings of an exploratory, qualitative study into the experiences of nine adult siblings of long-term missing people in Australia and presents the themes drawn from their accounts. The themes are briefly elaborated using direct quotations from participants in the study and represented in a diagram. The paper seeks to develop greater understanding of the inter-relationship between missingness and other social issues, to give voice to the views of participants and to encourage practitioners to engage more purposefully in work with family and friends affected by this issue. Some implications for social work practice are presented.     

Problem Behavior and Heart Rate Reactivity in Adopted Adolescents: Longitudinal and Concurrent Relations

The present longitudinal study examined resting heart rate and heart rate variability and reactivity to a stressful gambling task in adopted adolescents with aggressive, delinquent, or internalizing behavior problems and adopted adolescents without behavior problems (total N=151). Early‐onset delinquent adolescents showed heart rate hyporeactivity to the stress‐eliciting gambling task compared to late‐onset delinquent adolescents and adolescents without behavior problems. Heart rate, heart rate variability, and reactivity to stress were not related to environmental factors such as early‐childhood parental sensitivity, parental socioeconomic status, or adoptee's health status at arrival. We conclude that the distinction between delinquency and aggression and between childhood‐onset and adolescence‐onset delinquency is important for the study of stress reactivity in adolescents.     

A Longitudinal Study of Depressive Symptoms and Marijuana Use in a Sample of Inner‐City African Americans

The association between marijuana use and depressive symptoms was examined longitudinally in a sample of 622 African American youth, interviewed on six occasions, using hierarchical linear modeling (HLM). We considered whether depressive symptoms predicted changes in marijuana use and vice versa from high school through the transition into young adulthood. We also examined gender differences in these behaviors over time. The results indicated that depressive symptoms predicted later marijuana use only for males. Marijuana use did not predict later depressive symptoms for females or males. These findings are consistent with a unidirectional hypothesis indicating that marijuana use may play a role as mood regulator among young males, but not among females. Research findings also indicate that females with lower depressive symptoms use more marijuana than females who report high depressive symptoms. These findings did not change even after controlling for the effects of using other substances at previous stages, school achievement, and demographics factors. These results suggest that depressive symptoms may be an antecedent of marijuana use among African American males.     

Constituents’ economic interests and senator support for spending limitations

Peltzman [Peltzman, S., 1984. Constituent interest and congressional voting. Journal of Law and Economics 27, 181–210] argues that if constituents’ economic interests have well-defined “winners and losers” and are appropriately measured, then constituents’ economic interests, and not legislator ideology, are the most important determinates of legislator voting. We test Peltzman's theory by examining senatorial voting on three mandated spending limitation bills. We find, consistent with Peltzman's theory, that the ratio of federal spending in a senator's state to federal taxes paid by that state, and not a senator's personal ideology, matters on legislation where there are well-defined economic “winners and losers.” This is particularly important because unlike other constituents’ economic interest measures that only impact a fraction of the constituency, the ratio of federal spending to federal taxes in a state represents the economic interests of all the constituents in a state.     

Friendships under strain: The work–personal life integration of middle managers

Middle managers in today's organisations have reported experiencing longer working hours and intensified work regimes. These increased pressures, in turn, have led to growing difficulty in addressing the integration of their work and personal lives. In an exploratory study of the daily workplace experiences of Australian middle managers and the impacts on their personal lives, one of the key themes to emerge was respondents’ concerns about the negative effects on their friendships. This paper discusses middle managers’ recognition of the value of friendships for their wellbeing, and the resultant anger and sadness reported at the strain on these relationships due to competing time demands. The significant role that friendships play in alleviating some of the stresses of work demands, while concurrently being impeded by these same demands, is an important issue for organisations to consider. These findings indicate the need for middle managers to truly have an ability to engage in activities – and friendships – which will aid them in their working lives. The study also indicates a need for further investigation into the development and maintenance of friendships for both middle managers and other groups of employees.     

The Effect of Learning Experiences and Context on Infant Imitation and Generalization

Over the first years of life, infants gradually develop the ability to retrieve their memories across cue and contextual changes. Whereas maturational factors drive some of these developments in memory ability, experiences occurring within the learning event may also impact infants' ability to retrieve memories in new situations. In 2 experiments we examined whether it was possible to facilitate 12‐month‐old infants' generalization of learning in the deferred imitation paradigm by varying experiences before or during the demonstration session, or during the retention interval. In Experiment 1, altering the length, timing, or variability of training had no impact on generalization; infants showed a low, but consistent level of memory retrieval. In Experiment 2, infants who experienced a unique context for encoding and retrieval exhibited generalization; infants who experienced the context prior to the demonstration session, or during the retention interval, did not. Specificity is a robust feature of infant memory and is not substantially altered by encoding experiences in an observational learning paradigm. Previous history with a learning environment can, however, impact the flexibility of memory retrieval.