Relationships between undergraduates' argumentation skills, conceptual quality of problem solutions, and problem solving strategies in introductory physics

Title from PDF of title page (University of Missouri--Columbia, viewed on March 4, 2013).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Lloyd H. BarrowIncludes bibliographical references.Vita.Ph. D. University of Missouri--Columbia 2012."December 2012"This study explored the effects of alternative forms of argumentation on undergraduates' physics solutions in introductory calculus-based physics. A two-phase concurrent mixed methods design was employed to investigate relationships between undergraduates' written argumentation abilities, conceptual quality of problem solutions, as well as approaches and strategies for solving argumentative physics problems across multiple physics topics. Participants were assigned via stratified sampling to one of three conditions (control, guided construct, or guided evaluate) based on gender and pre-test scores on a conceptual instrument. The guided construct and guided evaluate groups received tasks and prompts drawn from literature to facilitate argument construction or evaluation. Using a multiple case study design, with each condition serving as a case, interviews were conducted consisting of a think-aloud problem solving session paired with a semi-structured interview. The analysis of problem solving strategies was guided by the theoretical framework on epistemic games adapted by Tuminaro and Redish (2007). This study provides empirical evidence that integration of written argumentation into physics problems can potentially improve the conceptual quality of solutions, expand their repertoire of problem solving strategies and show promise for addressing the gender gap in physics. The study suggests further avenues for research in this area and implications for designing and implementing argumentation tasks in introductory college physics.Includes bibliographical reference

Spin filtering in nanowire directional coupler

The spin transport characteristics of a nanowire directional electronic coupler have been evaluated theoretically via a transfer matrix approach. The application of a gate field in the region of mixing allows for control of spin current through the different leads of the coupler via the Rashba spin-orbit interaction. The combination of spin-orbit interaction and applied gate voltages on different legs of the coupler give rise to a controllable modulation of the spin polarization. Both structural factors and field strength tuning lead to a rich phenomenology that could be exploited in spintronic devices.Comment: 9 pages, 4 figure

Association between maternal-fetal genetic histocompatibility and maternal undernutrition in mice: influence on intrauterine growth

OBJECTIVE: The purpose of this study was to evaluate the effects of maternal-fetal genetic histocompatibility and the association of that condition with maternal undernutrition regarding fetal growth and litter size. STUDY DESIGN: Fetuses that were either syngeneic or allogeneic with the mothers were bred, using mice of well-defined syngeneic strains (A/J and Balb/c). Pregnant mice were fed using either unrestricted normal diet with 22% protein, consumed ad libitum, or a diet containing 14% protein, with intake restricted to 70% of that consumed by the unrestricted group. At the end of gestation, the number of fetoplacental units and fetal losses, the fetal and placental weight, and the weights of fetal brain and liver were recorded. RESULTS: Fetuses from undernourished mothers showed a reduction in body, placental, and brain weight (P < 0.01); the association of undernourishment with maternal-fetal genetic compatibility resulted in a greater impairment of fetal growth (P < 0.01). A reduction in the number of viable fetuses per female in the dietary-restricted groups was observed. (P < 0.01). Although the concurrence of maternal-fetal genetic compatibility resulted in a trend towards a greater reduction in the number of viable fetuses as well as in a higher rate of fetal loss, these differences did not reach statistical significance. CONCLUSIONS: In mice, the occurrence of maternal-fetal genetic histocompatibility alone did not change fetal growth; maternal undernutrition during pregnancy resulted in growth stunting of progenies with reduction of litter size; and the association of these 2 factors produced greater reduction of fetal weight.OBJETIVO: Avaliar os efeitos da histocompatibilidade genética materno-fetal e sua associação com a desnutrição materna em relação ao crescimento fetal e número de fetos. MÉTODOS: Fetos singênicos ou alogênicos em relação às respectivas mães foram obtidos através de cruzamentos de camundongos com linhagens genéticas bem definidas (A/J e Balb/c). As fêmeas grávidas foram alimentadas ad libitum com dieta normal contendo 22% de proteínas ou dieta com restrição, contendo 14% de proteína e aporte máximo de 70% do total consumido pelo grupo em dieta livre. No final da gestação, o número de unidades feto-placentárias e de perdas fetais, o peso da placenta e do feto, assim como o peso do cérebro e do fígado foram anotados. RESULTADOS: Os fetos das mães submetidas à desnutrição mostraram redução no peso corpóreo, placentário e cerebral (

Fractal analysis of weld defect patterns obtained by radiographic tests

This paper presents a fractal analysis of radiographic patterns obtained from specimens with three types of inserted welding defects: lack of fusion, lack of penetration, and porosity. The study focused on patterns of carbon steel beads from radiographs of the International Institute of Welding (IIW). The radiographs were scanned using a greyscale with 256 levels, and the fractal features of the surfaces constructed from the radiographic images were characterized by means of Hurst, detrended-fluctuation, and minimal-cover analyses. A Karhunen-Loeve transformation was then used to classify the curves obtained from the fractal analyses of the various images, and a study of the classification errors was performed. The obtained results indicate that fractal analyses can be an effective additional tool for pattern recognition of weld defects in radiographic tests.Comment: 7 pages, 2 figures. To appear AIP Conference Proceedings - QNDE 200

Supporting the Development of Science Teacher Leaders - Where Do We Begin?

This conference paper was presented at the annual meeting of the Association for Science Teacher Education in Minneapolis, MN, in January 2011.Teacher leadership has been recognized as a necessary ingredient to support educational reform efforts. Leaders provide the needed expertise to ensure reforms are successful in promoting student learning. The overarching goal of the Leadership in Freshman Physics program is to support a cadre of teachers-leaders who will become advocates for “Physics First” by developing their knowledge of physics content and research-based pedagogy. In order to support teachers in developing the knowledge, skills, and dispositions for effective leadership, it is important to first understand their initial views of teacher leadership and their prior leadership experiences. In this paper we present results from the initial phase of our multi-year research study in which we examine teacher' past leadership experiences, definitions of teacher leadership, and views of themselves as leaders. Participants include a cohort of 36 teachers participating in the program, each of whom has committed to teaching a year‐long freshman physics course at their school. Our findings indicate teachers' definitions of leadership are relatively narrow, and often confined to formal leadership roles. Though teachers participate in numerous leadership activities, they don't explicitly consider these to be leadership. Implications for addressing teachers' conceptions through professional development are shared

A POÉTICA URBANA DE MAURÍCIO SALGUEIRO

O objetivo desta dissertação é refletir sobre a poética urbana da série Urbis, produzida entre as décadas de 1960 e 1970 pelo artista plástico Maurício Salgueiro. O termo Urbis faz menção direta à palavra cidade, objeto de estudo do artista. A série é um projeto futurista de e construção da cidade que conglomera objetos dotados de dispositivos eletromecânicos, que por vezes os intitulamos como máquinas. Esta combinação possibilita reflexões sobre a cidade, principalmente no seu caráter frenético e movimentado, enfatizando o caos que invade o dia a dia dos que a habitam, na viva e atual reflexão dos habitantes da cidade enquanto personagens presentes da máquina maior: o próprio mundo contemporâneo. As novas buscas e práticas artísticas, no Século XX, tornaram possível a existência de outro olhar sobre o universo da escultura, em especial, na maneira de observar e discutir o papel do objeto artístico em si. As mudanças e os avanços ocorridos no decorrer do século passado deram origem a algumas questões a serem discutidas, principalmente sobre os caminhos convergentes entre a arte e a tecnologia, trazendo à tona a discussão sobre o hibridismo no campo da arte contemporânea, focando a discussão na série Urbis. Os avanços tecnológicos e os debates acerca do objeto tiveram início no final da década de 1950 e foram fatores fundamentais para o processo criativo e poético de Salgueiro. Abrem-se lacunas a ser preenchidas por uma série de reflexões acerca da presença do espectador no espaço físico onde o objeto artístico se encontra, bem como a interatividade entre objeto e espectador, que advém da necessidade de envolvimento e experimentação. A partir de então, a Urbis caminha em direção ao espaço e ao tempo, não constituindo, somente, um objeto para ensimesmar-se. A veleidade de Salgueiro pelos objetos/máquinas motorizadas influencia diretamente na estética da série, oferecendo possibilidades outrora impensáveis, como a revelação de sons e ruídos abrindo-se a diversas possibilidades de questionamentos por parte do sujeito/espectador. Maurício Salgueiro transforma a cidade num espaço para ser questionado e investigado, com significados a serem decodificados. Palavras-chave: Maurício Salgueiro. Cidade. Hibridismo. Arte/Tecnologia