This study explored the nature of the integration of the five components of pedagogical content knowledge (PCK): (a) Orientations toward Teaching Science, (b) Knowledge of Student Understanding, (c) Knowledge of Instructional Strategies and Representations, (d) Knowledge of Science Curriculum, and (e) Knowledge of Assessment of Science Learning. Given the topic and context specificity of PCK, this investigation was conducted in the context of the photosynthesis and heredity instruction of four teachers who were working at the same high school with the same curricular materials. Data sources included classroom observations, semi‐structured interviews, lesson plans, instructional materials, and students' work samples. Data were analyzed through three different approaches: (a) in‐depth analysis of explicit PCK, (b) enumerative approach, and (c) the constant comparative method. Data analysis indicated five salient features of the integration of the PCK components: (a) the integration of the components was idiosyncratic and topic‐specific; (b) Knowledge of Student Understanding and Knowledge of Instructional Strategies and Representations were central in the integration; (c) Knowledge of Science Curriculum and Knowledge of Assessment of Science Learning had most limited connection with other components; (d) Knowledge of Assessment of Science Learning was more often connected with Knowledge of Student Understanding and Knowledge of Instructional Strategies and Representations than with the other components; and (e) Didactic Orientations toward Teaching Science directed Knowledge of Instructional Strategies and Representations inhibiting its connection with other components. This study highlights that the quality of PCK depends on the coherence among the components as well as the strength of individual components. From a methodological perspective, this study demonstrates the possibility to make PCK more visible and accessible by using a PCK Map, a pictorial representation of the interactions of the PCK components. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 922–941, 2012

Argumentation is a core practice of science that inherently contains uncertainty. Relatively few studies have examined the role of uncertainty within argumentation and how teachers manage uncertainty leading to conceptual development. This design-based, multiple-case study employed the constant K E Y W O R D S argumentation, dialogue, epistemic understanding, managing uncertainty, social negotiation

This study tested a hypothesis that focused on whether or not teachers' pedagogical content knowledge (PCK) is a necessary body of knowledge for reformed science teaching. This study utilized a quantitative research method to investigate the correlation between a teacher's PCK level as measured by the PCK rubric (Park et al. 2008) and the degree to which his/her classroom is reform-oriented as measured by RTOP (Sawada et al. 2002). Data included 33 instructional sessions of photosynthesis and heredity videotaped with 7 high school biology teachers. Each session was given a score on both the PCK rubric and RTOP by two independent raters. Results indicate that PCK score is significantly related to RTOP score in terms of both total score (r=.831, p<.01) and subcomponent scores (ranging from r=.616 to .805, p<.01). Implications for science teacher education and future research are discussed.

This study demonstrates the fabrication and characterization of chicken egg albumen-based bio-memristors. By introducing egg albumen as an insulator to fabricate memristor devices comprising a metal/insulator/metal sandwich structure, significant bipolar resistive switching behavior can be observed. The 1/f noise characteristics of the albumen devices were measured, and results suggested that their memory behavior results from the formation and rupture of conductive filaments. Oxygen diffusion and electrochemical redox reaction of metal ions under a sufficiently large electric field are the principal physical mechanisms of the formation and rupture of conductive filaments; these mechanisms were observed by analysis of the time-of-flight secondary ion mass spectrometry (TOF-SIMS) and resistance–temperature (R–T) measurement results. The switching property of the devices remarkably improved by heat-denaturation of proteins; reliable switching endurance of over 500 cycles accompanied by an on/off current ratio (Ion/off) of higher than 103 were also observed. Both resistance states could be maintained for a suitably long time (>104 s). Taking the results together, the present study reveals for the first time that chicken egg albumen is a promising material for nonvolatile memory applications.

Arsenic (As) is considered the most common toxic metalloid, but its molecular mode of action is not well understood. We investigated whether arsenate [As(V)] can induce intracellular reactive oxygen species production and calcium oscillation in rice roots. To better understand the molecular basis of plant cell responses to As, we performed a large-scale analysis of the rice transcriptome during As(V) stress. As(V) induced genes involved in abiotic stress, detoxification pathways and secondary metabolic process. Genes involved in secondary cell wall biogenesis, cell cycle and oligopeptide transport were mainly downregulated. Genes encoding signalling components such as receptor-like cytoplasmic kinases protein kinase, APETALA2/ethylene response factor, heat shock factor, MYB and zinc-finger protein expressed in inflorescence meristem transcription factors were increased in expression. The expression of GARP-G2-like and C3H transcription factors was specifically modulated by As(V) stress. The predominant families of As(V)-regulated transporters belonged to the ATP-binding cassette superfamily and telurite-resistance/dicarboxylate transporters. Several factors involved in signaling, such as mitogen-activated protein kinase (MAPK), MAPK kinase kinase and calcium-dependent protein kinase (CDPK), were also upregulated. Moreover, As(V) markedly increased the activity of MAPKs and CDPK-like kinases, and CDPK and NADPH oxidases were involved in As-induced MAPK activation. Further characterization of these As(V)-responsive genes and signalling pathways may help better understand the mechanisms of metalloid uptake, tolerance and detoxification in plants.

We demonstrate that laser beams can be converged toward a light-absorbing target through optically diffusive media by using photoacoustic-guided interferometric focusing. The convergence of light is achieved by shaping the wavefront of the incident light with a deformable mirror to maximize the photoacoustic signal, which is propor tional to the scattered light intensity at the light absorber.

This quasi‐experimental and pre/posttest study was designed to examine whether fourth‐grade students who engaged in collaboratively writing letters to 11th‐grade students performed better on tests of conceptual understanding of a unit on force and motion than students who did not. The participants included 835 fourth‐grade students and 416 11th‐grade students from four elementary schools and one high school in the United States. Students in treatment groups were asked to write three letters for exchange at the beginning/during/completion of an 8‐week teaching unit about force and motion. The structure of writing was based on three components of arguments: question, claim, and evidence. A comparison of the pre‐ and posttest results indicated that students who engaged in collaborative letter‐writing tasks performed better than students who did not. The pre‐ and posttest results also showed that female, special, low socioeconomic status, and gifted students benefited the most from the collaborative letter‐writing tasks. Through the letter‐writing exchange activities, the fourth‐grade students were supported and encouraged to learn difficult concepts by the 11th‐grade students. The more the 11th graders asked the fourth graders for explanation and clarification of the concepts in the letters, the more the fourth‐grade students learned. Two factors related to argumentative writing were identified as predictors of success on students’ achievement tests: overall cohesiveness, with an emphasis on embedding multiple modal representations in the text and the strength of the relationship between claims and evidence. This study suggests that there is a pedagogical need to build support structures to help students understand the role of audience, the function of multiple modal representations, and the quality of evidence for supporting knowledge claims in argumentative writing, as this could lead to a better understanding of scientific concepts. © 2013 Wiley Periodicals, Inc. Sci Ed 97:745–771, 2013

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