Understanding Teacher Reflection as a Significant Tool for Bringing Reform-Based Teaching to College Mathematics

This paper describes a senior mathematics professor’s effort to change his teaching practice in a mathematical analysis course for secondary pre-service teachers in alignment with the current reform movement. Data include semester-long observations and interviews with the professor and his students. The data were analyzed by the use of reflection as the most significant tool for examining his experience of bringing about change. The reflection was used as a bridge from theory to practice by serving as a significant point for the professor to experience the process of professional development in a real sense. Discussions include the role of teacher reflection, teacher beliefs about good teaching and their manifestation in practice, the role of students in a reform-based classroom and the professor\u27s effort for changing pedagogy of the mathematics course and his search for continuing the effort. The researcher includes her own reflection of the processes of understanding the change process. Her views on inconsistency between the professors beliefs and his practice, the role of reflection as a hallmark of professionalism, and the importance of environment and support for the change to be sustainable are addressed

MIMIC Models for Uniform and Nonuniform DIF as Moderated Mediation Models.

In this article, the authors describe how multiple indicators multiple cause (MIMIC) models for studying uniform and nonuniform differential item functioning (DIF) can be conceptualized as mediation and moderated mediation models. Conceptualizing DIF within the context of a moderated mediation model helps to understand DIF as the effect of some variable on measurements that is not accounted for by the latent variable of interest. In addition, useful concepts and ideas from the mediation and moderation literature can be applied to DIF analysis: (a) improving the understanding of uniform and nonuniform DIF as direct effects and interactions, (b) understanding the implication of indirect effects in DIF analysis, (c) clarifying the interpretation of the "uniform DIF parameter" in the presence of nonuniform DIF, and (d) probing interactions and using the concept of "conditional effects" to better understand the patterns of DIF across the range of the latent variable

Symbiosis through exploitation and the merger of lineages in evolution

A model for the coevolution of two species in facultative symbiosis is used to investigate conditions under which species merge to form a single reproductive unit. Two traits evolve in each species, the first affecting loss of resources from an individual to its partner, and the second affecting vertical transmission of the symbiosis from one generation to the next. Initial conditions are set so that the symbiosis involves exploitation of one partner by the other and vertical transmission is very rare. It is shown that, even in the face of continuing exploitation, a stable symbiotic unit can evolve with maximum vertical transmission of the partners. Such evolution requires that eventually deaths should exceed births for both species in the free-living state, a condition which can be met if the victim, in the course of developing its defences, builds up sufficiently large costs in the free-living state. This result expands the set of initial conditions from which separate lineages can be expected to merge into symbiotic units

Hydrogen-like Atoms from Ultrarelativistic Nuclear Collisions

The number of hydrogen-like atoms produced when heavy nuclei collide is estimated for central collisions at the Relativistic Heavy Ion Collider using the sudden approximation of Baym et al. As first suggested by Schwartz, a simultaneous measurement of the hydrogen and hadron spectra will allow an inference of the electron or muon spectra at low momentum where a direct experimental measurement is not feasible.Comment: 6 pages, 4 figure

New evidence on taxes and portfolio choice

Identifying the effect of differential taxation on portfolio allocation requires exogenous variation in marginal tax rates. Marginal tax rates vary with income, but income surely affects portfolio choice directly. In systems of individual taxation – like Canada’s – couples with the same household income can face different effective tax rates on capital income when labor income is distributed differently within households. Using this source of variation we find statistically significant but economically modest responses to taxation. In a “placebo” test, using data from the U.S. (which has joint taxation), we find no effect of the intra-household distribution of labor income on portfolios

Semiconductor quantum dots in high magnetic fields: The composite-fermion view

We review and extend the composite fermion theory for semiconductor quantum dots in high magnetic fields. The mean-field model of composite fermions is unsatisfactory for the qualitative physics at high angular momenta. Extensive numerical calculations demonstrate that the microscopic CF theory, which incorporates interactions between composite fermions, provides an excellent qualitative and quantitative account of the quantum dot ground state down to the largest angular momenta studied, and allows systematic improvements by inclusion of mixing between composite fermion Landau levels (called $\Lambda$ levels).Comment: 13 pages, 8 figure