Adolescent sexual competence and sexual risk-taking : an ecological model of risk and protection

Using Bronfenbrenner\u27s ecological paradigm of human development as a framework, this study investigated the risk and protective factors associated with adolescent sexual behaviors and introduced the concept of sexual competence. Using data from the National Longitudinal Study of Adolescent Health, longitudinal and cross-sectional models were tested. Key findings include: (a) individual-level variables as well as family, peer, and school variables contribute to the total variance explained and have a direct effect on adolescents\u27 sexual competence; (b) the early influence of peers on sexual competence is later replaced by parental influences; (c) parent\u27s membership in a parent-teacher organization is associated with increased sexual competence; (d) the associations between the predictor variables and sexual competence are fairly consistent across gender and ethnicity; (e) overall, risk factors seem to be stronger predictors of adolescent sexual competence than protective factors; and (f) engaging in other health-risk behaviors and perceiving that there are obstacles to contraceptive use are strong indicators of sexual competence. These findings support the proposition that within an adolescent\u27s sphere of influence there are specific factors that promote the development of sexual competence as well as factors that inhibit the development of sexual competence. In addition, these findings indicate that the affect of these factors is consistent across gender and ethnicity

Quantitative analysis of approaches to group marking

Group work, where students work on projects to overcome challenges together, has numerous advantages, including learning of important transferable skills, better learning experience and increased motivation. However, in many academic systems the advantages of group projects clash with the need to assign individualised marks to students. A number of different schemes have been proposed to individualise group project marks, these include marking of individual reflexive accounts of the group work and peer assessment. Here we explore a number of these schemes in computational experiments with an artificial student population. Our analysis highlights the advantages and disadvantages of each scheme and particularly reveals the power of a new scheme proposed here that we call pseudoinverse marking.Comment: 13 pages, 1 table, 4 figure

Constraints on the tachyon condensate from anomalous symmetries

Using anomalous symmetries of the cubic string field theory vertex we derive set of relations between the coefficients of the tachyon condensate. They are in agreement with the results obtained from level truncation approximation.Comment: 6 page

Magnetic Monopoles in String Theory

Magnetic monopole solutions to heterotic string theory are discussed in toroidal compactifications to four spacetime dimensions. Particular emphasis is placed on the relation to previously studied fivebrane solutions in ten dimensions and on the possibility of constructing exact monopole solutions related to symmetric fivebranes.Comment: 24 pages (Corrected title

Global Defects In Theories With Lorentz Symmetry Violation

We study global topological defects in the Jacobson-Corley model which breaks Lorentz symmetry and involves up to fourth order derivatives. There is a window in the parameter space in which no solution exists. Otherwise, different profiles are allowed for the same values of the parameters. For a scale of Lorentz violation much higher than the scale of gauge symmetry breaking, the energy densities are higher, of the same order or smaller than in the usual case for domain walls, cosmic strings and hedgehogs respectively. Possible cosmological implications are suggested.Comment: 11 pages latex, misprints corrected, version to appear in PR

Noncommutative Q-balls

We obtain Q-ball solutions in noncommutative scalar field theory with a global U(1) invariance. The Q-ball solutions are shown to be classically and quantum mechanically stable. We also find that "excited Q-ball" states exist for some class of scalar potentials, which are classically stable in the large noncommutativity limit.Comment: 12 pages, LaTeX, v2: a typo corrected, v3: two references adde