Analytical and computational study of magnetization switching in kinetic Ising systems with demagnetizing fields

An important aspect of real ferromagnetic particles is the demagnetizing field resulting from magnetostatic dipole-dipole interaction, which causes large particles to break up into domains. Sufficiently small particles, however, remain single-domain in equilibrium. This makes such small particles of particular interest as materials for high-density magnetic recording media. In this paper we use analytic arguments and Monte Carlo simulations to study the effect of the demagnetizing field on the dynamics of magnetization switching in two-dimensional, single-domain, kinetic Ising systems. For systems in the ``Stochastic Region,'' where magnetization switching is on average effected by the nucleation and growth of fewer than two well-defined critical droplets, the simulation results can be explained by the dynamics of a simple model in which the free energy is a function only of magnetization. In the ``Multi-Droplet Region,'' a generalization of Avrami's Law involving a magnetization-dependent effective magnetic field gives good agreement with our simulations.Comment: 29 pages, REVTeX 3.0, 10 figures, 2 more figures by request. Submitted Phys. Rev.

Does Research on Nature of Science and Social Justice Intersect? Exploring Theoretical and Practical Convergence for Science Education

Even though enhancement of students’ understanding of social justice is thought to contribute to good citizenship, contextualising social justice in science education remains challenging for teachers because social justice is not conventionally a common feature of science teaching and learning. A separate issue in science education concerns a vast body of work on nature of science (NOS) elated to understanding of and about science. Understanding NOS is thought to contribute to scientific literacy as well as citizenship. Although social justice and NOS literatures share similar themes such as citizenship goals, the precise intersection of these literatures remains relatively understudied. In this chapter, we present an argument about how contemporary conceptualizations of NOS as well as NOS instruction might be used to promote goals related to social justice. In so doing, we aim to contribute to NOS literature by drawing on theories of social justice grounded in political philosophy. We trace the potential overlap of social justice and NOS concepts and draw out example recommendations for curriculum statements and practical teaching as well as practical teaching and learning approaches. Overall, we advocate the promotion of educational goals related to social justice through NOS instruction

Argumentation in school science : Breaking the tradition of authoritative exposition through a pedagogy that promotes discussion and reasoning

The value of argumentation in science education has become internationally recognised and has been the subject of many research studies in recent years. Successful introduction of argumentation activities in learning contexts involves extending teaching goals beyond the understanding of facts and concepts, to include an emphasis on cognitive and metacognitive processes, epistemic criteria and reasoning. The authors focus on the difficulties inherent in shifting a tradition of teaching from one dominated by authoritative exposition to one that is more dialogic, involving small-group discussion based on tasks that stimulate argumentation. The paper builds on previous research on enhancing the quality of argument in school science, to focus on how argumentation activities have been designed, with appropriate strategies, resources and modelling, for pedagogical purposes. The paper analyses design frameworks, their contexts and lesson plans, to evaluate their potential for enhancing reasoning through foregrounding the processes of argumentation. Examples of classroom dialogue where teachers adopt the frameworks/plans are analysed to show how argumentation processes are scaffolded. The analysis shows that several layers of interpretation are needed and these layers need to be aligned for successful implementation. The analysis serves to highlight the potential and limitations of the design frameworks

The moral impact of studying science

Science and religion are most usually compared on epistemic grounds: what do they tell us about the natural world and what methods do they use to determine those truths? The suggestion here is that the two fields should be compared on moral grounds: how do scientific and religious experiences affect the way a person lives his or her life? A hypothesis is presented in this vein: engaging in scientific work or education alters a person’s moral outlook on everyday matters. In this chapter, I articulate and motivate this claim by framing it against both theological and philosophical debate. I explore how it might be tested as a claim in moral psychology. The resulting vision presented here is of science and religion engaged in dialogue—at times necessarily embroiled—not only about the nature of the world, but regarding how best we navigate our way in it

Power, justice, and trust: a moderated mediation analysis of tax compliance among Ethiopian business owners

We explored the moderating roles of legitimate and coercive power held by the tax authority in the relationship between procedural justice, trust in the tax authority, and voluntary tax compliance. Drawing from fairness heuristic theory and the slippery slope framework of tax compliance, we predicted that procedural justice fosters voluntary tax compliance, particularly when legitimate power of the tax authority is low and when coercive power of the authority is high. Moreover, we predicted that these interactive effects are mediated by (cognition-based) trust. Finally, we predicted that coercive power of the tax authority is positively related with enforced tax compliance. The results of a field study among Ethiopian business owners supported most predictions. This research is among the first to integrate social-psychological and deterrence-related factors to understand tax compliance behavior in a developing country

Body fat mass and the proportion of very large adipocytes in pregnant women are associated with gestational insulin resistance.

Pregnancy is accompanied by fat gain and insulin resistance. Changes in adipose tissue morphology and function during pregnancy and factors contributing to gestational insulin resistance are incompletely known. We sought to characterize adipose tissue in trimesters 1 and 3 (T1/T3) in normal weight (NW) and obese pregnant women, and identify adipose tissue-related factors associated with gestational insulin resistance

Design, development and validation of a model of problem solving for Egyptian Science classes

Educators and policymakers envision the future of education in Egypt as enabling learners to acquire scientific inquiry and problem-solving skills. In this article, we describe the validation of a model for problem solving and the design of instruments for evaluating new teaching methods in Egyptian science classes. The instruments were based on an established model for problem solving and were designed to assess seventh grade students’ problem solving, experimental strategy knowledge, achievement and motivation towards science. The test for assessing students’ knowledge has been developed based on the topic, density and buoyancy which will be taught in seventh grade in a later intervention study. The instruments were partly self-developed and partly adapted from newly performed studies on strategy knowledge and problem solving in Germany. All instruments were translated into Arabic; the translation process and quality control are described. In order to determine the quality of the instruments, 44 students in Egypt completed the questionnaires and tests. The study’s aim to develop and validate the instruments did require an ad hoc and typical sample which was drawn from an accessible population. Accordingly, the characteristics of the sample are described. Data were analysed according to the classical test theory, but to underpin the results, the instruments were additionally analysed using the even stronger Rasch model. The findings demonstrated the reliability of the items and aspects of validity. In addition, this study showed how test items can be successfully developed and adapted in an international study and applied in a different language