Shortest paths among transient obstacles

Journal of Combinatorial Optimization - We present an optimal algorithm for determining a time-minimal rectilinear path among transient rectilinear obstacles. An obstacle is transient if it exists...     

Finding paths with minimum shared edges

Motivated by a security problem in geographic information systems, we study the following graph theoretical problem: given a graph G, two special nodes s and t in G, and a number k, find k paths from s to t in G so as to minimize the number of edges shared among the paths. This is a generalization of the well-known disjoint paths problem. While disjoint paths can be computed efficiently, we show that finding paths with minimum shared edges is NP-hard. Moreover, we show that it is even hard to approximate the minimum number of shared edges within a factor of $2^{\log^{1-\varepsilon}n}$ , for any constant ε>0. On the positive side, we show that there exists a (k?1)-approximation algorithm for the problem, using an adaption of a network flow algorithm. We design some heuristics to improve the quality of the output, and provide empirical results.     

A new preventive intervention for children of substance‐abusing parents: Results of a randomized controlled trial

Children of substance‐abusing parents (COS) are at risk for developing psychosocial problems. We evaluated the effectiveness of the manualized, 9‐session psycho‐educational preventive intervention “TRAMPOLINE” (PE) for 8–12‐year‐old COS compared with a non‐educational “fun and play” group (NE) of equal length delivered by social workers in 27 German counselling centres. A randomized controlled trial was conducted to compare PE (n = 130) and NE (n = 88) outcomes at baseline, post intervention, and 6‐month follow‐up. Primary outcomes were related to stress and coping; secondary were also examined. Analyses were conducted using baseline‐adjusted repeated measures linear mixed models. Five outcomes revealed improvements both in PE and NE, four of which were more pronounced in PE, and one more pronounced in NE. Small but significant group differences in favour of PE were found in “social isolation” and “addiction‐related knowledge.” Children from both groups reported reduced mental distress, reduced avoidance in coping with family stress, improved self‐perceived autonomy, and a better parent–child relationship. No changes were observed in self‐efficacy, physical stress symptoms, and in other health‐related quality of life aspects. TRAMPOLINE can instill positive changes in COS by reducing mental distress and social isolation.     

Premarital sexual intercourse: A test of the effects of peer group,religiosity, and sexual guilt

Previous research findings have been inconsistent concerning the influence on a person's sexual behavior of the peer group's sexual behavior and approval. Therefore, in this paper the relative importance of one's closest, friends' sexual behavior, their perceived approval for engaging in premarital coitus. age, sex guilt, and conventional religiosity were examined. Respondents were 467 dormitory students from a large mid‐Atlantic university. Results of separate path analyses for men and women showed that the greater the number of close friends thought to be nonvirgins, the greater the likelihood the man was also nonvirgin. Anticipated approval from close friends was not associated with a man being a nonvirgin. For women, both the sexual behavior and the expected degree of approval from close friends was associated with a woman being a nonvirgin. For both sexes, sex guilt was negatively associated with being a nonvirgin, whereas the respondent's age and degree of conventional religiosity were not associated with the sexual behavior. The findings indicate that researchers should specify whether a peer group's standards, or behavior, is being considered.