The challenge of changing deeply-held student beliefs about the relativity of simultaneity

Previous research indicates that after standard instruction students at all academic levels often construct a conceptual framework in which the ideas of absolute simultaneity and the relativity of simultaneity co-exist. This article describes the development and assessment of instructional materials intended to improve student understanding of the concept of time in special relativity, the relativity of simultaneity, and the role of observers in inertial reference frames. Results from pretests and post-tests are presented to demonstrate the effect of the curriculum in helping students deepen their understanding of these topics. Excerpts from taped interviews and classroom interactions help illustrate the intense cognitive conflict that students encounter as they are led to confront the incompatibility of their deeply-held beliefs about simultaneity with the results of special relativity.Comment: 17 pages, 6 figures, 2 tables, 27 references; Accepted for publication in Physics Education Research Section, American Journal of Physics (2001

Mitochondrial diaphorases as NAD+ donors to segments of the citric acid cycle that support substrate-level phosphorylation yielding ATP during respiratory inhibition

Substrate-level phosphorylation mediated by succinyl-CoA ligase in the mitochondrial matrix produces high-energy phosphates in the absence of oxidative phosphorylation. Furthermore, when the electron transport chain is dysfunctional, provision of succinyl-CoA by the alpha-ketoglutarate dehydrogenase complex (KGDHC) is crucial for maintaining the function of succinyl-CoA ligase yielding ATP, preventing the adenine nucleotide translocase from reversing. We addressed the source of the NAD+ supply for KGDHC under anoxic conditions and inhibition of complex I. Using pharmacologic tools and specific substrates and by examining tissues from pigeon liver exhibiting no diaphorase activity, we showed that mitochondrial diaphorases in the mouse liver contribute up to 81% to the NAD+ pool during respiratory inhibition. Under these conditions, KGDHC's function, essential for the provision of succinyl-CoA to succinyl-CoA ligase, is supported by NAD+ derived from diaphorases. Through this process, diaphorases contribute to the maintenance of substrate-level phosphorylation during respiratory inhibition, which is manifested in the forward operation of adenine nucleotide translocase. Finally, we show that reoxidation of the reducible substrates for the diaphorases is mediated by complex III of the respiratory chain.-Kiss, G., Konrad, C., Pour-Ghaz, I., Mansour, J. J., Nemeth, B., Starkov, A. A., Adam-Vizi, V., Chinopoulos, C. Mitochondrial diaphorases as NAD+ donors to segments of the citric acid cycle that support substrate-level phosphorylation yielding ATP during respiratory inhibition

Student learning paths from exploration of optical diffraction with on-line sensors to formal interpretative models

Optical physics is part of many national curricula, but is usually treated in a reductive and not useful way for students learning. A wide research literature point out that many students do not have clear the features of the phenomena considered, have difficulties in applying the maxima/minima condition to solve also simple problem of interference, apply reasoning based on the rays and rectilinear propagation or models mixing optical and geometrical optics. To overcome these learning problems, different research groups proposed new educational approaches and the use of on-line sensors opened new opportunities for learning in this field. The PERG of the University of Udine studied how to exploit the potentiality of new technologies in teaching optical diffraction, aiming to enable students to acquire a complete vision of optical diffraction and to build a functional understanding of the wave nature of light and the wave model of light behavior. Researches was performed to explore how students analyze the phenomenology and pass from a geometrical description of light behavior, to a wave model. The students conceptions on light diffraction, their learning path and their learning progression were monitored using inquiry based learning open tutorials, audio recording of teaching/learning sessions with students. The qualitative analysis of the monitoring tools showed that students developed different models when they faced a phenomenology far from their everyday experience as that of the light diffraction one. Many students developed models based on a geometrical rectilinear path light propagation to account the phenomenology they observed. The in depth analysis of phenomenology produce an adaptation of student models able to describe some features of the phenomenology, but not to interpret it