Measurements of drag and lift on tennis balls in flight

Measurements are presented of drag and lift on new tennis balls in flight. Two video cameras were used to measure the velocity and height of the balls at two positions separated horizontally by 6.4 m. The balls were fired from a ball launcher at speeds between 15 and 30 m/s and with topspin or backspin at rates up to 2,500 rpm. Significant shot-to-shot variations were found in both the drag and lift coefficients. The average drag coefficient was 0.507 ± 0.024, independent of ball speed or spin, and lower than the value usually observed in wind tunnel experiments. The lift coefficient increased with ball spin, on average, but significant lift was observed even at very low spin. The latter effect can be attributed to a side force arising from asymmetries in the ball surface, analogous to the side force responsible for the erratic path of a knuckleball in baseball.     

Sexual approach conditioning: Omission contingency tests

Male Japanese quail learned to approach a light that predicted visual exposure to a female quail. In Experiment 1, duration of visual exposure to the female did not systematically affect the speed or strength of conditioning. Introduction of an omission contingency for approach to the light after acquisition did not suppress conditioned approach relative to the performance of yoked controls. In Experiment 2, males learned to approach a light that predicted visual exposure to a female despite an omission contingency for approach in effect during acquisition. Experimental males were not slower to acquire the approach response under an omission contingency than were yoked controls. The findings indicate strong Pavlovian control of sexual conditioned approach in Japanese quail.     

An urban school renewal program: A case analysis

Conclusion One of the most gratifying returns was a chance comment offered by a teacher as we walked across the lawn toward a local fast food restaurant. We were chatting about what he had experienced during the preceding two years. You know, he said, when we began this, I didn't see many hopeful signs, but I think that most of us (teachers) feel now that we work in the best high school in the city. The source may have been biased, and rigorous controls were obviously lacking, but that is the way one teacher perceived the changes. Many gained planning, leadership, problem solving, and other important behavioral and coping skills that contributed in interactively subtle, but nevertheless real ways.Can good things be made to happen in urban schools? The quantified data are equivocal, but we believe that the associations among interventions and perceived changes support cautious optimism.     

Making and Mistaking Reality: What is Emotional Education?

A central thesis of this paper is that the mind and its thought evolve out of the experience of the whole person in their unique surroundings. It attempts to articulate the meaning and value of Emotional Education, especially in its relation to thought processes. It shows the value of learning from the particular, and from awareness of feeling states. It shows how making emotional enquiry can change the nature of the thinking, reducing the need of the thinker, and involves experiencing while not-knowing as well as more usual rational approaches.Recent affirmations from neuroscience of the psychoanalytic picture of conscious awareness arising from unconscious emotional processes are noted. Systemic and emotional thought processes are described and illustrated.While the nature of unconscious choice is recognised as part of all thought process, the “use of self” is explored as a conscious means of influencing the nature of thinking, and the attributes of both person and context necessary to flourishing thought are contrasted with the human needs which produce mistaken thought. Some questions which have been asked by students in Emotional Education classes, about free will, abuse, and ethics are raised. I hope the gratitude to people who have shared their feelings in order to think and be thought about in “emotional thinking” is evident; it is very real to me.     

Spanish-Speaking Children's Social and Language Development in Pre-Kindergarten Classrooms

The current study examined the social and language development of 345 Spanish-speaking pre-kindergartners who attended pre-kindergarten programs that varied widely in how much Spanish was spoken in the classroom by the teacher. Previous studies on English language learners have focused on how the language of instruction impacts children's language proficiency, ignoring the context in which children are learning. The current study found better social skills and closer teacher—child relationships in classrooms where teachers spoke some Spanish. Teacher ratings of children's peer social skills and assertiveness were positively associated with increased amounts of Spanish being spoken. More Spanish language use in the classroom was also related to a decrease in children's likelihood of being victims of aggression as rated by independent observers. The findings have implications for better understanding how policy decisions regarding language of instruction impact children in the social domain. As early education programs are faced with the challenging task of developing best practices for English language learners, it is essential that programs are attentive to the social implications of language.     

Kinematic analysis of shot-putting performed by wheelchair athletes of different medical classes

The aim of this study was to identify those kinematic characteristics that are most closely related to an athlete's medical classification and measured distance of a put. Two S-VHS camcorders (60 fields per second) were used to record the performance of 17 males of different classes. Each participant performed six trials and the best trial for each was selected for analysis. Three-dimensional kinematics of the shot and upper body segments at the instant of release and during the forward thrust (delivery) were determined. The average speeds and angles of the shot at release for different classes (5.3-7.8 ms -1 and 21.2 to 34.4°, respectively) were smaller than those exhibited by elite male able-bodied throwers. The height of the shot at release, the angular speed of the upper arm at release, the range of motion of the shoulder girdle during the delivery, and the average angular speeds of the trunk, shoulder girdle and upper arm during the delivery, were all significantly correlated with both the classification and measured distance ( P ? 0.05). The results indicate the importance of achieving a high average angular speed for each upper body segment during the delivery.     

The positions of primary and secondary schools in the English school field: a case of durable inequality

In interviews as part of a research study of structural reform in England, some tension between primary head teachers and their secondary peers was evident. This was symptomatic of a long-standing difference in status between the two phases. At a time when relations between stakeholders in local systems are subject to change, we seek to understand anew why that might be the case and how the tension we found was evidence of a current difference of power within interactions between representatives of the phases. We analyse differences of size, resources, workforce, pedagogy and history, and how they have resulted in different, and differently valued, practices and professional identities. We explore how attributes of the two phases have been counterposed and how, in complex interaction with wider discourses of politics, gender and age, this process has invested the differences with meanings and values that tend to relegate attributes associated with primary school. By focusing on the activation of cumulative inequality in interactions, we contribute a complementary perspective to studies of perceived relative status and highlight the implications for understanding school positioning in local arenas as the role of local authorities is reduced.     

托尼的美国梦

他来自意大利一个石场,在罗马南边的某个地方。他何时、如何到美国的,我不得而知。但一天晚上,我看见他正站在我家车库后面的车道上,大约五英尺七英寸或者八英寸高,瘦瘦的。