FORECASTING CREDIT HOURS

This paper employs Tobit to estimate retentionprobabilities and credit hours at two universities. Theinnovation is that this technique examines credit-hourchoice with the decision to depart the university treated as the choice of zero credit hours.Tobit is appropriate for this problem because itrecognizes the lower bound of zero on credit hours andincorporates this bound into the parameter estimates and forecasts. Models are estimated for credithours in a single year and cumulative hours over asix-year horizon.     

Child Effects on Parental Negativity: The Role of Heritable and Prenatal Factors

This study examined two possible mechanisms, evocative gene–environment correlation and prenatal factors, in accounting for child effects on parental negativity. Participants included 561 children adopted at birth, and their adoptive parents and birth parents within a prospective longitudinal adoption study. Findings indicated child effects on parental negativity, such that toddlers’ negative reactivity at 18 months was positively associated with adoptive parents’ over-reactive and hostile parenting at 27 months. Furthermore, we found that child effects on parental negativity were partially due to heritable (e.g., birth mother [BM] internalizing problems and substance use) and prenatal factors (e.g., BM illicit drug use during pregnancy) that influence children’s negative reactivity at 18 months. This study provides critical evidence for “child on parent” effects.     

The role of school leadership in Singapore's future-ready school reform

In this paper, we propose that successful education needs to fulfil three purposes while being cognisant of time and context: (a) learning, (b) lifework and (c) well-being. An education system is successful if it can develop future-ready individuals who will continue to learn beyond graduation, take on future lifework, and thrive in a changing society and environment. The future is context-situated and context-dependent. We have chosen to examine the economic, social and environmental context of Singapore to provide insight on the values, skills and knowledge that are required of future-ready learners according to the three purposes. We have compared the trajectories of other high-income nations with those of Singapore. Traditional teaching and learning practices no longer serve us well in the new realities that emerge. Education practices need to evolve in tandem to meet the demands of the 21st century. The roles that school leaders play include creating teaching and learning environments where these practices can be implemented. In our review of leadership practices and concepts, we have found that it is important for school leaders to question existing assumptions of teaching, learning and leadership practices in order to advance the development of 21st century skills, knowledge, values, and habits in learners.     

Concurrent validity of the early screening profiles and the differential ability scales with an at‐risk preschool sample

The relationship between the Early Screening Profiles (ESP; Harrison, 1990) and the Differential Ability Scales (DAS; Elliott, 1990a) was studied. The participants were 94 (57 males, 37 females) at‐risk preschoolers ranging in age from 3 years 6 months to 5 years 11 months (M= 4 years 7 months; SD= 6.3 months). The sample included 72 Caucasians, 21 African Americans, and one Hispanic. This study found that the DAS GCA (General Conceptual Ability) mean score was significantly lower than the ESP Total Screening mean score. However, a strong relationship (r= .78) was found between the ESP Total Screening and DAS GCA scores, indicating that the ESP is a good predictor of cognitive ability among at‐risk preschoolers. © 2000 John Wiley & Sons, Inc.     

Extra-curricular participation in sports and socio-demographic factors in Spanish adolescents: the AVENA study

The aims of this study were to identify differences between the sexes in extra-curricular participation in sports and to determine its association with body fat and socio-demographic factors in Spanish adolescents. A total of 2165 adolescents (1124 males and 1041 females) aged 13.0-18.5 years from the AVENA Study participated. Participants filled in an ad hoc questionnaire for extra-curricular participation in sports, which was the dependent variable. Independent variables were: age, percent body fat, and father's and mother's educational level and occupation. Chi-square tests and logistic regression were applied. Bivariate analysis showed for male adolescents that age and father's occupation were related to extra-curricular participation in sports. In addition, body fat and mother's education and occupation (all P?相似文献   

Detecting and correcting errors in rapid aiming movements: effects of movement time, distance, and velocity

According to closed-loop accounts of motor control, movement errors are detected by comparing sensory feedback to an acquired reference state. Differences between the reference state and the movement-produced feedback results in an error signal that serves as a basis for a correction. The main question addressed in the current study was how distance, movement time, and velocity influence both spatial or temporal error detection. Forty college-aged participants (30 women and 10 men) performed rapid aiming movements over 30 degrees or 50 degrees in either 210 ms or 350 ms without vision. The participants verbally estimated the distance moved and the movement time during acquisition before knowledge of results was given and during an immediate retention test without knowledge of results. Spatial and temporal objective-subjective correlations were greater in the 210-ms condition compared to the 350-ms condition, but were not related to movement velocity.     

Bifurcation analysis of a microcantilever in AFM system

The atomic force microscope system (AFM) has become a popular and useful instrument to measure the intermolecular forces with atomic resolution that can be applied in electronics, biological analysis, materials, semiconductors, etc. This paper studies the bifurcation phenomenon and complex nonlinear dynamic behavior of the probe tip between the sample and microcantilever of an atomic force microscope using the differential transformation method. The dynamic behavior of the probe tip is characterized with reference to bifurcation diagrams, phase portraits, power spectra, Poincaré maps, and maximum Lyapunov exponent plots produced using the time-series data obtained from differential transformation method. The results indicate that the probe tip behavior is significantly dependent on the magnitude of the vibrational amplitude. Specifically, the probe tip motion changes from T-periodic to 3T-periodic, then from 6T-periodic to multi-periodic, and finally to chaotic motion with windows of periodic motion as the vibrational amplitude is increased from 0 to 5.0. Furthermore, it is demonstrated that the differential transformation method is in good agreement for the considered system.