Numerical simulations of the frictional collisions of solid balls on a rough surface

Three-dimensional simulations of the frictional collision between solid balls moving on a rough surface are analyzed in this paper. The analysis is performed in the context of pool and snooker, two popular games in the pocket billiards family. Accurate simulations of ball motion in billiard games are useful for television broadcasts, training systems and any robotic game playing systems. Studying solid ball collisions in a three-dimensional space requires careful consideration of the different phenomena involved in ball motion such as rolling, sliding and ball spin about a general axis. A set of differential equations are derived describing ball dynamics during collisions. In the absence of explicit analytical solutions to the differential equations, a numerical procedure is performed to determine post-collision ball velocities and spins after collision. In addition, the paper also presents a methodology to analyze the curved, slip trajectories of balls immediately after impact. The results presented here, when compared with some experimental shots, show that the percentile errors in post-collision velocities are reduced by the proposed method. The prediction accuracies for ball travel direction are increased twofold by the proposed impact simulation algorithm.     

A novel miniature dynamic microfluidic cell culture platform using electro-osmosis diode pumping

An electro-osmosis (EOS) diode pumping platform capable of culturing cells in fluidic cellular micro-environments particularly at low volume flow rates has been developed. Diode pumps have been shown to be a viable alternative to mechanically driven pumps. Typically electrokinetic micro-pumps were limited to low-concentration solutions (≤10 mM). In our approach, surface mount diodes were embedded along the sidewalls of a microchannel to rectify externally applied alternating current into pulsed direct current power across the diodes in order to generate EOS flows. This approach has for the first time generated flows at ultra-low flow rates (from 2.0 nl/s to 12.3 nl/s) in aqueous solutions with concentrations greater than 100 mM. The range of flow was generated by changing the electric field strength applied to the diodes from 0.5 Vpp/cm to 10 Vpp/cm. Embedding an additional diode on the upper surface of the enclosed microchannel increased flow rates further. We characterized the diode pump-driven fluidics in terms of intensities and frequencies of electric inputs, pH values of solutions, and solution types. As part of this study, we found that the growth of A549 human lung cancer cells was positively affected in the microfluidic diode pumping system. Though the chemical reaction compromised the fluidic control overtime, the system could be maintained fully functional over a long time if the solution was changed every hour. In conclusion, the advantage of miniature size and ability to accurately control fluids at ultra-low volume flow rates can make this diode pumping system attractive to lab-on-a-chip applications and biomedical engineering in vitro studies.     

Teachers Working Cooperatively with Parents and Caregivers when Implementing LGBT Themes in the Elementary Classroom

Many teachers are interested in having a more inclusive multicultural education that includes lesbian, gay, bisexual, and transgender (LGBT) themes and gay-themed children's literature; unfortunately, research has found that many teachers do not implement gay themes in their multicultural education curriculum because of fear of criticism from parents and administrators, lack of professional training, and their own negative attitudes. Moreover, the most common topic that surfaces during teacher discussions are concerns over parental objections. This article will detail techniques and strategies when implementing LBGT themes and gay-themed children's literature in the classroom and how to deal positively, cooperatively, and proactively with parents and caregivers.     

Don't forget,Thursday is test[icle] time! The use of humour in sexuality education

Sexuality and humour share a fraught relationship at school, so that how humour might be productively employed in sexuality education constitutes a ‘risky’ consideration. This paper explores the role of humour in sexuality education as observed in a Year 9 New Zealand health class. Adding to existing literature emphasising students' use of humour at school, it also considers how teachers might productively mobilise humour in the classroom. Findings reveal that while humour serves established purposes for students such as consolidating heterosexual masculinities, securing peer group hierarchies and disrupting learning agendas, it may hold other pedagogically productive possibilities. Potential uses include the relief of monotony, engaging with the needs of particular cultural groups of students, reinforcing taught information and reducing apprehension around potentially uncomfortable topics. Via this empirical exploration of the mobilisation of humour, the paper endeavours to open its potential as a conceptual site of possibility in sexuality education.     

"I am" versus "we are": effects of distinctive variants of self-talk on efficacy beliefs and motor performance

Before completing a team-based dart-throwing activity, 80 undergraduates were randomly assigned to one of three pre-performance self-talk conditions: (a) self-talk statements that focused upon one's personal capabilities, (b) self-talk statements emphasizing the group's capabilities, or (c) a control condition where neutral statements were implemented. Participants in all conditions subsequently rated their confidence in their own (i.e. self-efficacy) as well as their team's (i.e. collective efficacy) capabilities, before carrying out the task. Overall, self-efficacy, collective efficacy, and performance indicators were all greatest for individuals who practised self-talk focusing on the group's capabilities, as opposed to individual-focused and neutral conditions. Findings are considered with respect to their novel theoretical contribution to the social cognition literature and their implications for fostering efficacy perceptions and team performance.     

The past in the present: historicising contemporary debates about gender and education

History is often embedded, explicitly or implicitly, in discourses on contemporary aspects of gender and education, but relatively few scholars engage critically with history as they grapple with current issues. This article posits ‘historical sensibility’ as a means of engaging constructively with the past when scrutinising and working on current issues in gender and education. Four features of historical sensibility are mapped out and compared with established ways of approaching the relationship between the present and past. The utility of historical sensibility is demonstrated with reference to ongoing debates about the feminisation of schooling, the sexualisation of children and the leisure pursuits of young women.     

Untangling the relative contribution of maltreatment severity and frequency to type of behavioral outcome in foster youth

Within maltreatment research, type, frequency, and severity of abuse are often confounded and not always specifically documented. The result is samples that are often heterogeneous in regard to maltreatment experience, and the role of the different components of maltreatment in predicting outcome is unclear. The purpose of the present study was to identify and test the potential unique role of type, frequency, and severity of maltreatment to elucidate each variable's role in predicting outcome behavior. Data from 309 youth in foster care (ages 8–22) and their caregivers were collected using the Modified Maltreatment Classification System and the Behavioral Assessment System for Children, 2nd Edition (BASC2), to measure maltreatment exposure and behavioral outcome respectively. A measurement model of the BASC2 was completed to determine model fit within the sample data. A second confirmatory factor analysis (CFA) was completed to determine the unique contributions of frequency and severity of maltreatment across four types of abuse to externalizing, internalizing, and adaptive behavior. The result of the CFA determined good fit of the BASC2 to the sample data after a few modifications. The result of the second CFA indicated that the paths from severity to externalizing behavior and adaptive behavior (reverse loading) were significant. Paths from frequency of abuse were not predictive of behavioral outcome. Maltreatment is a complex construct and researchers are encouraged to examine components of abuse that may be differentially related to outcome behavior for youth. Untangling the multifaceted nature of abuse is important and may have implications for identifying specific outcomes for youth exposed to maltreatment.