The vibrational mode structure of a golf ball

In this paper, we report the discrete frequencies at which golf balls can vibrate, the mode patterns of these vibrations and how these modes can be excited. There are two broad classes of modes: those that radiate sound waves and those that do not. Both silent and acoustic modes are excited by tangential (i.e. spin-producing) impact forces; only acoustic modes are excited by radial impact forces. Exact analytical results for a homogeneous ball core are compared with finite element numerical results for both a core and a model two-piece ball. Correspondences are readily established for the important low-frequency modes, and the good agreement suggests the validity of these results for real golf balls. The results potentially provide the basis for a rapid, simple and non-destructive method of measuring the effective high-frequency elastic shear modulae of balls (and ball cores) as well as a method for 'tuning' the performance of balls for specific clubs. Some of these aspects are explored further in our companion paper in this issue.     

Bundling in Cable Television: A Pedagogical Note With a Policy Option

Bundling can be a pricing mechanism by which monopolists capture economic surplus from consumers.We suggest that given the cost structure of media markets, channel bundling in the cable and satellite market could also emerge in a competitive environment. A la carte channel pricing on cable television may or may not increase consumer welfare and could decrease total welfare. Because bundling may create other problems, policymakers may consider allowing cable and satellite networks to sell packages of channel space to viewers at a given price, allowing viewers to choose which channels they want in their packages. We term this option quasi-bundling.     

Switching between science and culture in transpecies transplantation

This article discusses xenotransplantation (XTP: the surgical role of nonhuman tissues, organs, and cells for human transplantation) and examines the way its scientific promoters have defended their technology against potentially damaging public representations. The authors explore the criteria used to legitimate the selection of the pig as the best species from which to "harvest" transplant tissues in the future. The authors' analysis shows that scientists and medical practitioners routinely switch between scientific and cultural repertoires. These repertoires enable such actors to exchange expert identities in scientific discourse for public identities in cultural discourse. These discourses map onto similarities and differences between animal donors and human hosts. Finally, the case is used to comment on a number of related approaches where the dynamics of medical and scientific authority are discussed.     

Group size and organisational conditions for children’s learning in preschool: a teacher perspective

Background:?There is a limited amount of research about group size in preschool, and how it impacts on teachers’ working conditions and their ability to support children’s learning and knowledge development in line with curriculum intentions.

Purpose:?From a perspective on quality, this article examines the organisational conditions for children’s learning in preschool in relation to group size. The questions at issue are: how do teachers explain how they organise the child group and the learning environment in preschool, and why?

Sample:?The sample consists of 12 preschools from different parts of Sweden. The preschools selected for the study are stratified in order to represent small and large group sizes in Swedish preschools as defined by the Swedish National Agency for Education. The sample contains both urban and rural regions and represents districts that differ geographically, demographically, ethnically, and which include varied socioeconomic structures. The 12 preschools had children in three age groupings: 1–3, 3–5 or 1–5. The number of children in the participating preschools ranged from 12 children to 45 children, with seven of the preschools having more than 30 children in their groups.

Design and method:?The article is based on interactionist perspectives, Bronfenbrenner’s ecological systems theory, a critical ecology of the early childhood profession, theories of children’s learning, and four dimensions of pedagogical quality. Together, these theoretical perspectives contribute to an understanding of the relationships between policy issues, educational goals, group size and teachers’ competence in organising and creating conditions for children’s learning. Semi-structured interviews were conducted with two teachers from each of the 12 preschools. The interviews lasted between 40–60 minutes and were recorded and transcribed verbatim. The analytical process was conducted in three steps and can be described as an analytical process of abduction. The four dimensions of pedagogical quality were used as analytical lenses to discern and understand critical aspects related to the teachers’ understanding of group size.

Result: Irrespective of group size, most of the children participate in different group constellations throughout the day, some organised by the teachers and some by the children themselves. Teachers’ competence to organise the children in such ways that good conditions for learning were created, differed between preschools, and depended on the teachers’ approach, which can be described as either intentional or unintentional learning.

Conclusion: Teachers’ organisational approaches influence the quality of the preschool and conditions for children’s learning in distinct ways.     

Early education teachers’ conceptualizations and strategies for managing closeness with the class in child care

This study investigated teachers’ experiences of closeness during interactions with the group of children in child care. Structured interviews were conducted with 24 female teachers who were teaching children between the ages of three and five (mean age = 3.9) regarding their perceptions of closeness with the group of children in the class. Qualitative analyses of the interviews revealed a group solidarity domain of teacher–group relationships composed of three dimensions which comprise emotional solidarity, consensual solidarity, and functional solidarity, with emotional solidarity most dominant in the teachers’ perceptions. This group solidarity domain was interpreted as being consistent with qualities found in Grusec and Davidov’s group participation domain. The findings that, teachers’ closeness with the group of children in the class were dominated by the emotional dimension is similar to previous research results which report the predominance of personal and intimate interactions in relational closeness between teachers and individual children. Teachers described intentional strategies for managing close group relationships that made use of interactional histories between the teachers and children in the class. These discoveries provide a new perspective on teacher closeness with groups, an area of research not often investigated. It also provides insights into the importance teachers place on connecting emotionally with children when they are with the collective group in the classroom.     

The Influence of Teachers’ Efficacy and Beliefs Regarding Mathematics Instruction in the Early Childhood Classroom

This was a correlational study conducted with a population of prekindergarten educators from a large, metropolitan school district. The purpose was to examine if there were relationships between and among early childhood teachers’ sense of self-efficacy, their beliefs about the importance of mathematics, and their mathematics instructional practices. Examining teachers’ efficacy and beliefs can inform educational practice and help to differentiate between more and less successful instructional practices when teaching mathematics in the early childhood classroom. Data were collected on teacher efficacy and teacher beliefs about the importance of mathematics with two self-report questionnaires. The hypothesis that the teachers higher in efficacy will rate the importance of mathematics higher on the teacher-belief scale than the teachers with lower efficacy was found to be true with this sample, but the correlation was weak. The level of efficacy of the early childhood teachers in this sample confirmed that in assessing their capabilities, they rate themselves high in instructional strategies, classroom management, and student engagement. The early childhood teachers did not rate their belief in mathematics as high as their efficacy. Observations of mathematics instructional practices were conducted with twenty teachers. It was hypothesized that the combination of high teacher efficacy and high teacher mathematics beliefs would show alignment with the presence of standards-based mathematics instructional practices. The results were not statistically significant. No correlation signals a need for more research to explore what other personal or external factors relate to mathematics instructional practices in the early childhood classroom. The research may inform pre kindergarten teachers and teacher educators about effective instructional strategies and knowledge needed to launch early childhood students on a developmentally appropriate pathway to mathematical literacy.