A mixed-integer linear programming approach to the optimization of event-bus schedules: a scheduling application in the tourism sector

This paper deals with “The Enchanted Journey,” which is a daily event tour booked by Bollywood-film fans. During the tour, the participants visit original sites of famous Bollywood films at various locations in Switzerland; moreover, the tour includes stops for lunch and shopping. Each day, up to five buses operate the tour. For operational reasons, however, two or more buses cannot stay at the same location simultaneously. Further operative constraints include time windows for all activities and precedence constraints between some activities. The planning problem is how to compute a feasible schedule for each bus. We implement a two-step hierarchical approach. In the first step, we minimize the total waiting time; in the second step, we minimize the total travel time of all buses. We present a basic formulation of this problem as a mixed-integer linear program. We enhance this basic formulation by symmetry-breaking constraints, which reduces the search space without loss of generality. We report on computational results obtained with the Gurobi Solver. Our numerical results show that all relevant problem instances can be solved using the basic formulation within reasonable CPU time, and that the symmetry-breaking constraints reduce that CPU time considerably.

Interactions between dorsolateral and ventromedial prefrontal cortex underlie context-dependent stimulus valuation in goal-directed choice.

External circumstances and internal bodily states often change and require organisms to flexibly adapt valuation processes to select the optimal action in a given context. Here, we investigate the neurobiology of context-dependent valuation in 22 human subjects using functional magnetic resonance imaging. Subjects made binary choices between visual stimuli with three attributes (shape, color, and pattern) that were associated with monetary values. Context changes required subjects to deviate from the default shape valuation and to integrate a second attribute in order to comply with the goal to maximize rewards. Critically, this binary choice task did not involve any conflict between opposing monetary, temporal, or social preferences. We tested the hypothesis that interactions between regions of dorsolateral and ventromedial prefrontal cortex (dlPFC; vmPFC) implicated in self-control choices would also underlie the more general function of context-dependent valuation. Consistent with this idea, we found that the degree to which stimulus attributes were reflected in vmPFC activity varied as a function of context. In addition, activity in dlPFC increased when context changes required a reweighting of stimulus attribute values. Moreover, the strength of the functional connectivity between dlPFC and vmPFC was associated with the degree of context-specific attribute valuation in vmPFC at the time of choice. Our findings suggest that functional interactions between dlPFC and vmPFC are a key aspect of context-dependent valuation and that the role of this network during choices that require self-control to adjudicate between competing outcome preferences is a specific application of this more general neural mechanism.

Effects of intrinsic pleasantness and goal conduciveness appraisals on somatovisceral responding: Somewhat similar, but not identical.

In the emotion literature, appraisals of an event's pleasantness and goal conduciveness are often considered as interchangeable and subsumed under the term valence. Some appraisal theories, however, emphasize that there is a conceptual difference between these two appraisals. With the current study, we investigated whether such a conceptual difference would be reflected in different somatovisceral response profiles for intrinsic pleasantness and goal conduciveness. Participants viewed unpleasant and pleasant pictures (intrinsic pleasantness) and performed either goal conducive (i.e., decreasing the size of unpleasant pictures, increasing the size of pleasant pictures) or goal obstructive (i.e., increasing the size of unpleasant pictures, decreasing the size of pleasant pictures) arm movements. Our data suggest that the two appraisals have somewhat similar, but not identical, response patterns. Thus, our results emphasize the importance of distinguishing between intrinsic pleasantness and goal conduciveness. Moreover, we find evidence that the efferent effects of the two appraisals combine multiplicatively, and that predictability of goal conduciveness may influence the impact of goal conduciveness appraisals on somatovisceral responding.

Appraisal-driven somatovisceral response patterning: effects of intrinsic pleasantness and goal conduciveness.

Several componential emotion theories suggest that appraisal outcomes trigger characteristic somatovisceral changes that facilitate information processing and prepare the organism for adaptive behavior. The current study tested predictions derived from Scherer's Component Process Model. Participants viewed unpleasant and pleasant pictures (intrinsic pleasantness appraisal) and were asked to concurrently perform either an arm extension or an arm flexion, leading to an increase or a decrease in picture size. Increasing pleasant stimuli and decreasing unpleasant stimuli were considered goal conducive; decreasing pleasant stimuli and increasing unpleasant stimuli were considered goal obstructive (goal conduciveness appraisal). Both appraisals were marked by several somatovisceral changes (facial electromyogram, heart rate (HR)). As predicted, the changes induced by the two appraisals showed similar patterns. Furthermore, HR results, compared with data of earlier studies, suggest that the adaptive consequences of both appraisals may be mediated by stimulus proximity.

First evidence for differential and sequential efferent effects of stimulus relevance and goal conduciveness appraisal.

In the context of a memory task, participants were presented with pictures displaying biological and cultural threat stimuli or neutral stimuli (stimulus relevance manipulation) with superimposed symbols signaling monetary gains or losses (goal conduciveness manipulation). Results for heart rate and facial electromyogram show differential efferent effects of the respective appraisal outcomes and provide first evidence for sequential processing, as postulated by Scherer's component process model of emotion. Specifically, as predicted, muscle activity over the brow and cheek regions marking the process of relevance appraisal occurred significantly earlier than facial muscle activity markers of goal conduciveness appraisal. Heart rate, in contrast, was influenced by the stimulus relevance manipulation only.

Index Tracking Using Data-Mining Techniques and Mixed-Binary Linear Programming

Index tracking has become one of the most common strategies in asset management. The index-tracking problem consists of constructing a portfolio that replicates the future performance of an index by including only a subset of the index constituents in the portfolio. Finding the most representative subset is challenging when the number of stocks in the index is large. We introduce a new three-stage approach that at first identifies promising subsets by employing data-mining techniques, then determines the stock weights in the subsets using mixed-binary linear programming, and finally evaluates the subsets based on cross validation. The best subset is returned as the tracking portfolio. Our approach outperforms state-of-the-art methods in terms of out-of-sample performance and running times.

Fetal programming and epigenetic mechanisms in arterial hypertension.

PURPOSE OF REVIEW To provide an overview of available evidence of the potential role of epigenetics in the pathogenesis of hypertension and vascular dysfunction. RECENT FINDINGS Arterial hypertension is a highly heritable condition. Surprisingly, however, genetic variants only explain a tiny fraction of the phenotypic variation and the term 'missing heritability' has been coined to describe this phenomenon. Recent evidence suggests that phenotypic alteration that is unrelated to changes in DNA sequence (thereby escaping detection by classic genetic methodology) offers a potential explanation. Here, we present some basic information on epigenetics and review recent work consistent with the hypothesis of epigenetically induced arterial hypertension. SUMMARY New technologies that enable the rigorous assessment of epigenetic changes and their phenotypic consequences may provide the basis for explaining the missing heritability of arterial hypertension and offer new possibilities for treatment and/or prevention.

SOMS: SurrOgate MultiStart algorithm for use with nonlinear programming for global optimization

SOMS is a general surrogate-based multistart algorithm, which is used in combination with any local optimizer to find global optima for computationally expensive functions with multiple local minima. SOMS differs from previous multistart methods in that a surrogate approximation is used by the multistart algorithm to help reduce the number of function evaluations necessary to identify the most promising points from which to start each nonlinear programming local search. SOMS’s numerical results are compared with four well-known methods, namely, Multi-Level Single Linkage (MLSL), MATLAB’s MultiStart, MATLAB’s GlobalSearch, and GLOBAL. In addition, we propose a class of wavy test functions that mimic the wavy nature of objective functions arising in many black-box simulations. Extensive comparisons of algorithms on the wavy testfunctions and on earlier standard global-optimization test functions are done for a total of 19 different test problems. The numerical results indicate that SOMS performs favorably in comparison to alternative methods and does especially well on wavy functions when the number of function evaluations allowed is limited.

Latent profiles of work motivation in adolescents in relation to work expectations, goal engagement, and changes in work experiences

Motivation plays a key role in successful entry into working life. Based on a cross-sectional and a one-year longitudinal study, we used a person-centered approach to explore work-related motivation (i.e., autonomous goals, positive affect, and occupational self-efficacy) among 577 students in 8th grade (Study 1) and 949 adolescents in vocational training (Study 2). Based on latent profile analysis, in both studies we identified four groups that were characterized by different levels of overall motivation and one group characterized by low positive affect and mean levels in autonomous goals and self-efficacy. Profiles characterized by high levels of motivation showed the highest levels of positive work expectations and goal engagement and the lowest levels of negative work expectations in Study 1 and the highest levels of person-job fit, work engagement, and job satisfaction in Study 2. Moreover, latent difference score analysis showed that motivational profiles predicted changes in person-job fit and work engagement across one year but not in job satisfaction. The results imply that career counselors should be aware of characteristic motivational patterns of clients that may require specific counseling approaches.

Adolescent Pregnancy Prevention in San Jose, Costa Rica : Assessment of an Educational Intervention

This thesis explores adolescent pregnancy in San Jose, Costa Rica and examines a school-based pregnancy prevention intervention. The relationships between school, gender and risk of adolescent pregnancy are also analyzed, and recommendations are made for effective pregnancy prevention programming. The Purral region of Guadalupe on the outskirts of San Jose, Costa Rica, suffers a higher rate of adolescent pregnancy compared to the rest of the country. In response to this problem, the International Health Central American Institute (IHCAI) implemented a sexual health education program in two local secondary schools in 2006. Very little information about the program is available. It is known that the program was initially evaluated through assessments of the participants’ knowledge before and after the educational sessions. There was no evaluation of the youth attitudes or behaviors, adolescent pregnancies, or long-term impact. The author worked with IHCAI in San Jose, Costa Rica to perform an assessment of the longer term effects of this sexual health education program. They developed a questionnaire to evaluate the knowledge, attitudes, and behaviors surrounding sexual health of youth in the Purral community. Researchers at IHCAI later used this survey to collect data from adolescents who had participated in the educational intervention and those who had not. This thesis analyzes the data collected by IHCAI to assess the effectiveness of the - 2 - educational intervention and the influence of other factors on the knowledge, attitudes, and behaviors of adolescents in the Purral region. The thesis begins with an overview of adolescent pregnancy, Costa Rica and the Purral region, and a description of the education intervention implemented by IHCAI. The research goal, logic model, and methods are then described. The results are reported, and the thesis then concludes with discussion of the results as well as study limitations and recommendations for future research and intervention. This thesis will be used to guide IHCAI’s continuation and expansion of adolescent pregnancy prevention programming.