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We experimentally study nonlinear force propagation into granular material during impact from an intruder, and we explain our observations in terms of the nonlinear grain-scale force relation. Using high-speed video and photoelastic particles, we determine the speed and spatial structure of the force response just after impact. We show that these quantities depend on a dimensionless parameter, $M'=t_c v_0/d$, where $v_0$ is the intruder speed at impact, $d$ is the particle diameter, and $t_c$ is the collision time for a pair of grains impacting at relative speed $v_0$. The experiments access a large range of $M'$ by using particles of three different materials. When $M' \ll 1$, force propagation is chain-like with a speed, $v_f$, satisfying $v_f \propto d/t_c$. For larger $M'$, the force response becomes spatially dense and the force propagation speed departs from $v_f\propto d/t_c$, corresponding to collective stiffening of a strongly compressed packing of grains., Comment: 3 figures, 5 pages

When an intruder strikes a granular material from above, the grains exert a stopping force which decelerates and stops the intruder. Many previous studies have used a macroscopic force law, including a drag force which is quadratic in velocity, to characterize the decelerating force on the intruder. However, the microscopic origins of the force law terms are still a subject of debate. Here, drawing from previous experiments with photoelastic particles, we present a model which describes the velocity-squared force in terms of repeated collisions with clusters of grains. From our high speed photoelastic data, we infer that `clusters' correspond to segments of the strong force network that are excited by the advancing intruder. The model predicts a scaling relation for the velocity-squared drag force that accounts for the intruder shape. Additionally, we show that the collisional model predicts an instability to rotations, which depends on the intruder shape. To test this model, we perform a comprehensive experimental study of the dynamics of two-dimensional granular impacts on beds of photoelastic disks, with different profiles for the leading edge of the intruder. We particularly focus on a simple and useful case for testing shape effects by using triangular-nosed intruders. We show that the collisional model effectively captures the dynamics of intruder deceleration and rotation; i.e., these two dynamical effects can be described as two different manifestations of the same grain-scale physical processes., Comment: 14 pages, 13 figures

Synthesizing research on effective at-risk/dropout prevention programs and the learning theory articulated in the American Psychological Association (APA) Learner-Centered Principles, this study examined the essential components present in an exemplary at-risk/dropout prevention program for kindergarten through sixth grade students. The perceptions of district-level and building-level administrators, at-risk coordinators, at-risk teachers, regular classroom teachers, and parents of at-risk students were investigated regarding the programs ability to reduce at-risk behaviors. In all, 25 people were interviewed. Findings of this qualitative case study suggest three major themes that were essential to the effectiveness of the at-risk program: (1) shared assumptions about mission; (2) student-centered focus; and (3) commitment to creation of a nurturing environment. The findings further suggest that 11 subthemes supported the major themes. Analysis of the findings revealed that features within each of the three broad areas clearly reflected the four domains of the APA learner-centered principles, although not every subtheme incorporated the concepts of all four domains. Participants indicated that their program effectively reduced three major at-risk behaviors through improved attendance, academics, and self-esteem. Parents described impressive changes in improved self-esteem, but other respondents identified changes in all three areas. (Contains 2 tables and 53 references.) (Author/SLD)

The relationship between the superintendent and board of education has a significant impact on the quality of a district's educational program. This conceptual paper explores the implications of three distinct trends for that relationship: (1) changing demographics; (2) changes brought about by school reform; and (3) changes in superintendents themselves. The heart of this paper explores the impact of these trends on superintendent-board relationships in the future. After examining current research on superintendent-board relations, the paper considers recent demographic trends and speculates whether changing demographics would alter, in any substantive way, relations between superintendents and boards of education. In a similar vein, how do reforms such as the development of more comprehensive accountability systems (often tied to performance or merit pay for administrators) and changes in school governance models (such as the Chicago model) impact the relationship between superintendents and their school boards? Finally, how do changes in superintendents themselves--in their training and work experiences--affect their relations with school boards? Essentially, the authors ask whether any of these changes will influence or alter relations between superintendents and school boards and, if so, in what way? The essay concludes by posing a series of "Interesting Questions" meant to stimulate discussion and further research into board-superintendent relations. (Contains 49 references.) (RT)

The field of educational leadership faces serious challenges in the 21st century, such as the shortage of principals and superintendents, the growing demands for leadership positions, and the struggle for adequate resources. This paper explores the challenges facing this field from the position of university educational leadership preparation. The many factors involved with school leadership preparation do not operate separately of each other but are interdependent. What occurs in one area, such as university administration's awareness of the education administration program, can affect how the university supports the program, which in turn, affects faculty promotion, tenure, salary, program quality, and student enrollment. The interdependency practiced by baseball leagues is used as a metaphor of school leader preparation to help communicate the nature of mutual collaboration. To meet the needs of current and future schools, this paper recommends that practitioners in all aspects of educational leadership realize their work is fundamentally interdependent, that they come together to seek a mutual and complex understanding of the educational leadership context and the stakeholders who work within it, that they build common ground and shared goals, and that they work collaboratively toward the realization of those goals. (Contains 56 references.) (RT)

The district superintendent's instructional leadership has emerged as a critical issue in ongoing efforts to reform schools. To elaborate on this trend, an exploratory case study that focused on the perceived and actual leadership characteristics and actions of district superintendents is presented here. For the study, indepth interviews were conducted with five district superintendents in California. Interview responses indicated that the superintendents perceived four attributes to be essential in their ability to be successful instructional leaders: (1) possession and articulation of an instructional vision; (2) the creation of an organizational structure that supports their instructional vision and leadership; (3) assessment and evaluation of personnel and instructional programs; and (4) organizational adaptation. By employing responses given by the superintendents and by scrutinizing their articulated roles, a preliminary model of perceived superintendent behaviors was constructed. To confirm perceptions, actions, and behaviors articulated by the superintendents, triangulation interviews were conducted with school principals and school board members in each of the participating districts. A 52-item questionnaire was also administered to every principal and school board member in these districts. The responses confirmed the articulated actions and behaviors of these superintendents in their promotion of the technical core of curriculum and instruction. (Author/RJM)

Personnel evaluation in education occurs predominantly at the summative level and is used primarily for personnel decisions. Teachers are provided little feedback regarding their classroom performance and even less assistance in improving areas identified as weaknesses. While the improvement of instructional practice is perhaps the most important--and most positive--purpose of teacher evaluation, the current "dominant model" of teacher evaluation does not empower teachers to improve their instructional practices. Typically, there is no feedback for the teacher and no suggestions for improvement. The Collaborative Teacher Growth Model is offered as a possible alternative to the current system of evaluating teacher performance. This model incorporates feedback from a variety of sources--administrator observations, peer evaluations, student feedback, and teacher self-assessment--in an attempt to obtain a thorough and representative assessment of a teacher's instructional performance. The individuals then work collaboratively to develop an appropriate and individualized improvement plan for the teacher. However, several limitations to this alternative model exist. Language contained in state law and/or collective bargaining agreements often limit the frequency and scheduling of teacher evaluations. Fair dismissal laws may also specify that only individuals holding certain positions within the district may serve as evaluators of teaching performance. Finally, teachers must still be open to the idea of constructive feedback and must acknowledge that there is a need for improvement and that all teachers can improve. (Contains 36 references.) (Author)

An essential component of effective leadership is the cultivation of followers. This study examined whether 67 California and Ohio elementary and secondary school teachers understood the role and importance of followership in influencing school leadership. Teachers provided demographic data and completed the Teacher Sentiment Inventory, which assessed the extent to which their specific actions and characteristics reflected their understanding of followership. They ranked statements associated with particular actions or beliefs concerning the relationship between the teacher and the principal. Results indicated that teachers fell into one of three styles of followership: exemplary followers (with high levels of active engagement and independent thinking), pragmatist followers (who perform required tasks well but seldom venture beyond them), or conformist followers (with high active engagement but low independent thinking). None of the teachers were classified as alienated (independent thinking only) or passive (neither independent thinking nor actively engaged) followers. Both men and women scored high on independent thinking in their work. Female teachers reported higher levels of active engagement in the role of follower than did male teachers. (Contains 26 references.) (SM)

This study investigated the criteria for admission to teacher education at 50 National Council for Accreditation of Teacher Education (NCATE) accredited undergraduate universities. These universities varied in geographical location, public and private affiliation, and size of student enrollment. The study analyzed and evaluated admission criteria in light of recent educational reforms that call for higher standards and more qualified candidates in order to ascertain whether the universities had actually implemented more demanding performance based on criteria for teacher candidate selection. Based on the findings, the study identified the absence of standardized admission criteria and consistent policies of ongoing assessment. It proposed a balanced integration of both performance based admission criteria as well as continual evaluation of program goals in the admission and education of preservice teachers. (Contains 32 references.) (Author)

This study investigated the criteria for admission to teacher education at 50 undergraduate universities accredited by the National Council for Accreditation of Teacher Education (NCATE). These universities varied in geographical location, public and private affiliation, and size of student enrollment. The study analyzed and evaluated admission criteria in light of recent educational reforms that call for higher standards and more qualified candidates, in order to ascertain whether the universities had actually implemented more demanding performance based criteria for teacher candidate selection. The study employed the qualitative and quantitative analysis of data drawn from university published materials, telephone inquiries, teacher-education and public school teacher interviews, and surveys of the dean, department chair, or director at the 50 universities. The study disclosed: (1) a general lack of consistency in requirements for admission to teacher candidate programs at the university level; (2) a need for qualitative measures to evaluate admission candidates; and (3) a need to modify initial screening and ongoing evaluation of teacher candidates. (Contains 19 references.) (MAH)