Efficient algorithms for minimum-cost flow problems with piecewise-linear convex costs

We present two efficient algorithms for the minimum-cost flow problem in which arc costs are piecewise-linear and convex. Our algorithms are based on novel algorithms of Orlin, which were developed for the case of linear arc costs. Our first algorithm uses the Edmonds-Karp scaling technique. Its complexity isO(M logU(m+n logM)) for a network withn vertices,m arcs, M linear cost segments, and an upper boundU on the supplies and the capacities. The second algorithm is a strongly polynomial version of the first, and it uses Tardos's idea of contraction. Its complexity isO(M logM(m+n logM)). Both algorithms improve by a factor of at leastM/m the complexity of directly applying existing algorithms to a transformed network in which arc costs are linear.The final stage of this work was performed while Ron Shamir was a visitor at DIMACS (Center for Discrete Mathematics and Theoretical Computer Science), Rutgers University. Supported in part by National Science Foundation Grant NSF-STC88-09648, and by Air Force Grants AFOSR-89-0512 and AFOSR-90-0008.     

Violence and risk of PTSD, major depression, substance abuse/dependence, and comorbidity: Results from the National Survey of Adolescents.

With a national household probability sample of 4,023 telephone-interviewed adolescents ages 12-17, this study provides prevalence, comorbidity, and risk-factor data for posttraumatic stress disorder (PTSD), major depressive episode (MDE), and substance abuse/dependence (SA/D). Roughly 16% of boys and 19% of girls met criteria for at least 1 diagnosis. Six-month PTSD prevalence was 3.7% for boys and 6.3% for girls, 6-month MDE prevalence was 7.4% for boys and 13.9% for girls. and 12-month SAM prevalence was 8.2% for boys and 6.2% for girls. PTSD was more likely to be comorbid than were MDE and SA/D. Results generally support the hypothesis that exposure to interpersonal violence (i.e., physical assault, sexual assault, or witnessed violence) increases the risk of these disorders and of diagnostic comorbidity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A family of stewart platforms with optimal dexterity

Stewart platform configurations (architectures and poses) optimizing local dexterity are investigated. The condition number of the Jacobian matrix is used to quantify the dexterity of the manipulator. For a platform-centered Jacobian reference location and a given characteristic length for scaling purposes, a two-parameter family of optimal configurations is shown to exist. Two suitable architectural parameters defining the family are identified and properties of the optimal configurations are discussed. The optimization results are shown to be easily extended for other Jacobian reference locations and for other singular value-based local dexterity measures. It is suggested that the existence of a two-parameter family of optimal local configurations could be exploited to aid in the resolution of optimal architectures for global measures.     

The effects of password length and reference profile size on the performance of a multivariate text-dependent typist verification system

The performance of Napier et al.'s typist verification algorithm (Keyboard user verification: toward an accurate, efficient, and ecologically valid algorithm, International Journal of Human-Computer Studies 43 (1995) 213-222) was assessed in a text-dependent setting. Twenty-nine subjects typed a 17 character password 50 times. False acceptance and false rejection rates were then calculated as the number of repetitions of the password included in the reference profile was increased from 6 to 20 and the number of digraphs from the password included in the verification process was increased from 2 to 16. The performance of the system (12% total error rate) was found to be comparable with the best results reported in other studies using text-dependent algorithms, and substantially better than that reported in studies using a text-independent paradigm with passwords of this length. The relationship between password length and reference profile size was found to conform to an exponential decay function, which accounted for 92% of the variability in verification error rates.     

Misidentification rate in the Israeli dairy cattle population and its implications for genetic improvement

The DNA microsatellites can be efficiently used to determine incorrect paternity attribution of cattle without genotyping of dams. Allelic frequencies of the population were determined for 12 microsatellites using the maternal alleles of 102 AI sires. The frequency of the most common microsatellite allele ranged from 0.27 to 0.58. Most loci had at least one allele that was present in only a single individual. Paternity of 9 of 173 cows (5.2%) and 3 of 102 bulls (2.9%) was excluded because putative paternal alleles were not present in progeny for at least one locus. For 4 of the 9 cows and all 3 bulls, exclusion was based on at least two loci. Mean probability of exclusion was 0.85 for cows and 0.99 for bulls. With an assumed cost of US $5 per genotype, a misidentification rate of 5%, and a discount rate of 0.05, additional profit for the Israeli-Holstein breeding program from genotyping 100 test daughters of each young sire becomes positive within 10 yr and reaches nearly US $2.4 million after 20 yr.     

Umbilical cord fluoride serum levels may not reflect fetal fluoride status

An exercise for the estimation of the percentage risk of cases of tuberculosis attributable to co-infection HIV/AIDS, using the following formula, is propounded: RA%=p[m2r(hR-h)] + (1-p)[m3r (hR-h)]/p[m1+m2r (hR+1-h)] + (1-p)[m3r (hR+1-h)] x 100 where: p= proportion of BK infected, r= risk of tuberculosis infection, h= proportion of persons infected with HIV, m1= breakdown rate of endogenous tuberculosis, m2= breakdown rate of exogenous tuberculosis, m3= breakdown rate of primary tuberculosis, R= relative risk of morbidity among persons infected with HIV.     

Responding to the Needs of Children, Families, and Schools: The 2002 Multisite Conference on the Future of School Psychology.

The preparations for and the implementation of the 2002 Multisite Conference on the Future of School Psychology are described. The conference goals were to (a) achieve consensus on current and future demands for school psychologists and our profession's ability to meet those demands; (b) conceptualize the practice of school psychology in the face of diminishing numbers and increasing demand for services; and (c) develop an agenda to use the resources we have to maximize the benefits to the children and schools that we serve. A problem-solving model served as the conceptual foundation of the conference. School psychologists at the host site in Indianapolis and 30 remote sites collaborated to identify threats, opportunities, strategies, and action plans to respond better to the needs of children, families and schools. The conference not only generated excitement and hope for our future, but also provided a framework to propel the current and future practice of school psychology. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Pitch discrimination in field- and isolation-reared black-capped chickadees (Parus atricapillus).

Prior research has shown that male black-capped chickadees (Parus atricapillus) raised in the field produce constant relative pitch cues (frequency ratios) in their songs, whereas males reared in isolation from adult song do not. In this study, the authors found that field-reared male chickadees needed fewer than half as many sessions to learn an operant (go/no-go) auditory discrimination that linked S+ note pairs with a constant-frequency ratio than a discrimination that varied the frequency ratio of S+ pairs randomly. Most important, isolation-reared males needed over 5 times as many sessions to learn the constant-ratio discrimination compared with field-reared males. This is, to the authors' knowledge, the first report of impaired pitch discrimination in isolate songbirds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)