Radiation reaction forces and the expanding universe

The expanding universe is described in terms of the known forces of classical physics. It is shown that great clouds of stars are non-conservative systems and that radiation reaction forces play a part in guiding stellar motions. The forces are of importance in unsymmetrical stars and evidence is collected to show that perhaps all stars are possessed of deep seated thermal asymmetries. The forces continually act to increase the mean velocity of the stars and the galaxy is calculated to expand at a rate which closely approximates the observed rate of expansion. From a relation connecting the mean velocity of the stars and their age, it is deduced from the observed motions that the age of the galaxy is about 10¹⁰ years. The deduced rate of expansion of the galaxy agrees well with the observational data and is identical in form and numerical constant with Hubble's relation connecting the velocity of recession and distances of nebulæ.Because of the relative size and spacing of the extra galactic nebulæ and the short time scale it is supposed that the nebulae were formed by fission from a parent-super nebula and this resulted in thermal asymmetries which brought the newly considered forces into action.The resulting expansion was produced by slow evolutionary radiation processes which bear no direct relation to the properties of space or atomic constants.The calculations suggest that in describing the motions of typical stars over long periods of time, radiation reaction forces are as important as the classical gravitational forces.     

The role of higher education institutions in national development

Abstract from the report of the International Conference on Education (33rd Session) of the International Bureau of Education. It deals with (i) the role of higher education institutions in national development, (ii) improving and sustaining the competence of educators and (iii) managing the system of education.     

The effect of towing a range of relative resistances on sprint performance

The aim of this study was to compare sprint performance over 10 and 20?m when participants ran while towing resistances, weighing between 0 and 30% of body mass. The sample of 33 participants consisted of male rugby and soccer players (age 21.1?±?1.8 years, body mass 83.6?±?13.1?kg, height 1.82?±?0.1?m; mean?±?s). Each participant performed two sets of seven sprints over 20?m using a Latin rectangular design. The times were recorded at 10 and 20?m using electronic speed gates. The sprints of 13 players were video-recorded to allow calculation of stride length and frequency. For both sprints, a quadratic relationship was observed between sprint time and resistance as sprint time increased from 2.94?s to 3.80?s from 0 to 30% resistance. This relationship was statistically significant but considered not to be meaningful for performance because, over the range of resistances used in this study, the quadratic model was never more than 1% (in terms of sprint time) from the linear model. As resistance increased, the stride length shortened, with mean values of 1.63?±?0.13?m at 0% body mass and 1.33?±?0.13?m at 30% of body mass. There was no significant change in stride frequency with increasing resistance. The results show that in general there is an increase in sprint time with an increase in resistance. No particular resistance in the range tested (0?–?30%) can be recommended for practice.     

The kinematic differences between accurate and inaccurate squash forehand drives for athletes of different skill levels

ABSTRACT

To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball’s velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a “zeroing-in” effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the “functionality” of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot.     

Static and dynamic accuracy of a magnetic-inertial measurement unit used to provide racket swing kinematics

Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics.     

Egocentrism, ethnocentrism, and altrocentrism: factors in individual and intergroup violence

Egocentrism and ethnocentrism are considered as cognitive biases which foster violence at both individual and group levels. Each is characterized as a lack of empathy or an inability to see reality as it appears to others. Altrocentrism is conceptualized as a more mature, socialized form of perceiving in which the individual can understand another person because he sees the facts as they appear to the other. Adolescents tend to see policemen and teachers as hostile and threatening because they cannot empathize with the roles of these authority figures. Evidence indicates that violent behavior is associated with egocentric and ethnocentric thinking. Devices such as role-playing, stating the case of the other, fantasy, and the culture-assimilator foster altrocentric thinking, and some evidence indicates that they reduce the frequency of resort to violence. Cross-cultural education must begin use of such procedures if we are to minimize domestic and international violence.     

Technique and timing in women's inward two and one half somersault tuck (405C) and the men's inward two and one half somersault pike (405B) 3 m springboard dives

The purpose of this study was to compare the inward two and one half somersault dive in a tuck position (405C) performed by females (n = 22) and the inward two and one half somersault dive in a pike position (405B) performed by males (n = 24) to determine changes required by females to successfully perform 405B. Key performance variables in inward dives were also compared to those of backward dives. Video data of the dives performed at the 1999 FINA World Diving Cup were captured and digitized to obtain times and postures of the divers at specific events including takeoff and entry. Estimates of flight height and mass-normalised work done on the springboard were obtained from flight times. Some females worked the springboard strongly enough to generate sufficient height and rotation to perform 405B. Males performed 405B comfortably because they achieved better height and rotation than the females. A comparison of backward and inward dives revealed that divers are able to attain greater height in backward dives than inward dives.     

VALUE-FRAMING ABORTION IN THE UNITED STATES: AN APPLICATION OF MEDIA SYSTEM DEPENDENCY THEORY

This paper is in the tradition of social analysis aimed at creatingframeworks to join mass media and public opinion processes (e.g.Clarke and Evans, 1983; Gamson, 1975; Gitlin, 1980; Hall, 1977;Iyengar and Kinder, 1987; Lang and Lang, 1968, 1983; Lippman,1922; Mollotch and Lester, 1974; Noelle-Neuman, 1974; Paletzand Entman, 1981; Shaw and McCombs, 1977; Turner and Paz, 1986).After a brief review of media system dependency (MSD) theory,we illustrate how it may apply to public opinion processes thatentail contested issue ‘value-frames’ (Ball-Rokeachand Rokeach, 1987). In such cases, the media system is directlyimplicated in the negotiation of legitimacy of opposing positionson an issue. Our illustrative case is the abortion issue asit has been played out in the United States over recent decades(Luker, 1984). We focus upon the respective capacities of pro-and anti-abortion movements to control the value-frame of mediacoverage of the issue (Guthrie, 1989). A value-frame may beconceived as ‘... the main substantive theme of a moralityplay’ (Ball-Rokeach and Tallman, 1979) wherein the distinctionbetween ‘good’ and ‘bad’ hangs in thebalance; in this case, between positions on abortion. We suggestthat change in the value-frame of media coverage and publicdiscourse may be understood, at least in part, as an outcomeof change in contestants' MSD relations.