Kinematic analyses of seated throwing activities with and without an assistive pole

In Paralympic seated throwing events, the athlete can throw with and without an assistive pole. This study aimed to identify and compare performance-related kinematic variables associated with both seated throwing techniques. Twenty-nine non-disabled males (21.9 ± 2.6 years) performed 12 maximal throws using a 1-kg ball in two conditions (no-pole and pole). Automatic 3D-kinematic tracking (150 Hz) and temporal data were acquired. There was no significant difference between ball speeds at the point of release between conditions (no-pole = 12.8 ± 1.6 m/s vs. pole = 12.9 ± 1.5 m/s). There were four kinematic variables that were strongly correlated with ball speed when throwing with or without an assistive pole. These variables were elbow flexion at the start phase (pole r = .39 and no-pole r = .41), maximum shoulder external rotation angular velocity during the arm cocking phase (pole r = .42), maximum shoulder internal rotation angular velocity during the arm acceleration phase (pole r = .47), and should internal rotation angular velocity at the instant of ball release (pole r = .40). The pole clearly influenced the throwing technique with all four strongly correlated variables identified in this condition, compared to only one during the no-pole condition. When using the pole, participants produced significantly higher shoulder internal rotation angular velocities during the arm acceleration phase (pole = 367 ± 183°/s vs. no-pole = 275 ± 178°/s, p < .05) and at the instant of ball release (pole = 355 ± 115°/s vs. no-pole = 264 ± 120°/s, p < .05), compared to throwing without the pole. These findings have implications for the development of evidence-based classification systems in Paralympic seated throwing, and facilitate research that investigates the impact of impairment on seated throwing performance.     

A momentous hour at Panama

The experimental investigation of the laws governing the excitation of x-rays by electron impact appears to be near completion. However, the existence of the proton, with its mass of 1,846 times that of the electron, provides the possibility of introducing anew variable—the mass—into collision experiments. Previous investigations have led to inconclusive results except that it is known that when fast α-particles fall on an element, its characteristic x-ray spectrum is excited.In the writer's experiments, a mass spectrograph is used to bring either protons or electrons, of same energy in the range from 15 kv. to 25 kv., onto a copper target. The arrangement eliminates several known sources of error. X-radiation produced passed into an argon filled Geiger counter.The procedure was to compare two currents: (1) the current composing an electron beam just intense enough to produce detectable x-rays; and (2) that composing the strongest proton beam which certainly produced less radiation.The ratio of these currents is a minimum value for p, the ratio of the efficiencies for excitation of electrons and protons respectively.The results were that (1) no radiation from proton impacts was observed, (2) the minimum value of p from three sets of experiments was 740; 237,000; and 6,400.In view of the directness of the experiment, the order of magnitude of the highest figure is presented as the result, i.e. ? = 10⁵. This may be compared with ($\text{M/m = 1,846, W/m)}\text{3}\text{2}\text{= 79,310, (M/m)}{}^2\text{= 3,408,000}$.Wave mechanical considerations of impact processes indicate that radiation should be produced by proton impacts of energy greater than the critical energy (for copper, 8.86 kv.) but intensity formulas have not been derived.If they can be derived the present results offer the possibility of checking the wave mechanics of impact processes.     

ASSESSING THE QUALITY OF PARENT–TEACHER RELATIONSHIPS FOR STUDENTS WITH ADHD

Family involvement in education, including the quality of family–school communication, has been demonstrated repeatedly to have a substantial effect on child development and success in school; however, measures of this construct are limited. The purpose this study was to examine the factor structure and concurrent validity of the Quality of the Parent–Teacher Relationship, a subscale of the Parent–Teacher Involvement Questionnaire, in a sample of children with attention deficit hyperactivity disorder (ADHD). Participants were 260 parents and teachers of children diagnosed with ADHD in Grades kindergarten to 6. Results provided support for a two‐factor model, consisting of separate factors for parents and teachers, and correlational findings provided support for concurrent validity. This measure appears to have utility in assessing parent–teacher relationships and evaluating the effectiveness of family–school interventions.     

Action learning: cultural differences

The article describes the experience of forming a set in a higher education institution and offers some observations and insights gained from the perspectives of the role of the set adviser, cultural differences and the challenges of attempting to align theory, practice and experience.