How Does Practice-Based Teacher Preparation Influence Novices' First-Year Instruction?

Background/Context Teacher preparation suffers from a lack of evidence that guides the design of learning experiences to produce well-prepared beginners. An increasing number of teacher educators are experimenting with practice-embedded approaches to prepare novices for ambitious instruction. This study examines the role of core instructional practices introduced during preparatory experiences in shaping novices’ first-year teaching. Research design Employing a mixed-methods approach, we compare the first-year teaching of two groups of individuals with secondary science certification, one of which comprises graduates from a practice-embedded preparation program, and the other graduates from programs that did not feature practice-embedded preparation. A total of 116 science lessons taught by 41 first-year teachers were analyzed, focusing on the quality of student opportunities to learn (OTL) observed during the lessons. Research questions This study sought answers to two research questions: 1) What are the characteristics of students’ OTL from first-year teachers, one group of whom learned a set of core instructional practices during their preparation program and the other group of whom were not exposed to core practices? 2) Who provides opportunities for students to engage in meaningful disciplinary practices as outlined in the Next Generation Science Standards, during the first year of teaching, if any? How did they create such opportunities? Findings Independent-sample t-tests showed that there are significant mean differences between the two groups (t=3.1∼8.9; p <.001), on four metrics associated with their students’ opportunities to learn. In-depth qualitative case studies reveal two ways that core practices shape instruction in new teachers’ classrooms: (a) they support novices in formulating an actionable curricular vision as advocated by the science education community, and (b) they appear to help novices notice, attend to, and build upon students’ ideas in classrooms with the use of strategies and tools recommended by the program. Conclusions/Recommendations A focus on a set of strategic and intentional practices, designed to help teachers achieve rigorous and equitable learning goals, has potential as a curricular frame for teacher preparation. But the emphasis should be placed on the vision and pedagogical goals that underlie the core practices, rather than the ungrounded use of strategies or tools themselves

Visible-ultraviolet spectroscopic ellipsometry of lead zirconate titanate thin films

We measured pseudodielectric functions in the visible-ultraviolet spectral range of Pb(ZrxTi1−x)O3 (x=0.2, 0.56, 0.82) (PZT)grown on platinized silicon substrate using the sol-gel method and also on (0001) sapphire using radio frequency sputtering method. Using a parametric optical constant model, we estimated the dielectric functions of the PZTthin films. Taking the second derivative of the fitted layer dielectric functions and using the standard critical point model, we determined the parameters of the critical points. In the second derivative spectra, the lowest bandgap energy peak near 4eV is fitted as a double peak for annealedPZTs associated with the perovskite phase. As-grown PZTs have mainly pyrochlore phase and the lowest bandgap is fitted as a single peak. We compared the bandgap energies with literature values

High quality epitaxial growth of PbTiO3 by molecular beam epitaxy using H2O2 as the oxygen source

Single crystalline PbTiO3films have been epitaxially grown on SrTiO3 (001) substrates by molecular beam epitaxy using H2O2 as the source of active oxygen. The optimum growth conditions have been determined by analyzing a range of growth parameters affecting growth and used to attain single phase and stoichiometric PbTiO3thin films.In situ reflection high-energy electron diffraction pattern indicated the PbTiO3films to be grown under a two-dimensional growth mode. The full width at half maximum of the rocking curve of a relatively thin65nm (001) PbTiO3film is 6.2arcmin which is indicative of high crystal quality. The band gap of PbTiO3, as determined by ellipsometric measurement, is 3.778eV

Rigor and Responsiveness in Classroom Activity

Background/Context: There are few examples from classrooms or the literature that provide a clear vision of teaching that simultaneously promotes rigorous disciplinary activity and is responsive to all students. Maintaining rigorous and equitable classroom discourse is a worthy goal, yet there is no clear consensus of how this actually works in a classroom. Focus of Study: What does highly rigorous and responsive talk sound like and how is this dialogue embedded in the social practices and activities of classrooms? Our aim was to examine student and teacher interactions in classroom episodes (warm-ups, small group conversations, whole group conversation, etc.) and contribute to a growing body of research that specifies equity in classroom practice. Research Design: This mixed-method study examines differences in discourse within and across classroom episodes (warm-ups, small group conversations, whole group conversation, etc.) that elevated, or failed to elevate, students’ explanatory rigor in equitable ways. Data include 222 secondary science lessons (1,174 episodes) from 37 novice teachers. Lessons were videotaped and analyzed for the depth of students’ explanatory talk and the quality of responsive dialogue. Findings: The findings support three statistical claims. First, high levels of rigor cannot be attained in classrooms where teachers are unresponsive to students’ ideas or puzzlements. Second, the architecture of a lesson matters. Teachers and students engaging in highly rigorous and responsive lessons turned potentially trivial episodes (such as warm-ups) of science activity into robust learning experiences, connected to other episodes in the same lesson. Third, episodes featuring one or more forms of responsive talk elevated rigor. There were three forms of responsive talk observed in classrooms: building on students’ science ideas, attending to students’ participation in the learning community, and folding in students’ lived experiences. Small but strategic moves within these forms were consequential for supporting rigor. Conclusions/Recommendations: This paper challenges the notion that rigor and responsiveness are attributes of curricula or individual teachers. Rigorous curriculum is necessary but not sufficient for ambitious and equitable science learning experiences; the interactions within the classroom are essential for sustaining the highest quality of scientific practice and sense-making. The data supported the development of a framework that articulates incremental differences in supporting students’ explanatory rigor and three dimensions of responsiveness. We describe implications for using this framework in the design of teacher programs and professional development models

Dielectric functions and critical points of PbTiO3, PbZrO3, and PbZr0.57Ti0.43O3 grown on SrTiO3 substrate

Single crystalline PbTiO3, PbZrO3, and PbZr0.57Ti0.43O3 thin films on SrTiO3 (001) substrates were grown by a combination of molecular beam epitaxy and rf sputtering methods. The authors measured the dielectric functions of the thin films using spectroscopic ellipsometry and determined the interband critical point energies using standard critical point model. They compared the critical point energies to the band structure calculations in the literature. The data suggest that anticrossing behavior occurs between Ea and Eb near Zr=0.17. This phenomenon is attributed to a coupling between X1c and X3c bands caused by intrinsic alloy disorder

Spectroscopic ellipsometric study of ZnO and Zn1-xMgxO thin films grown on (0001) sapphire substrate

We grew ZnO and Zn1-xMgxO thin films on (0001) sapphire substrates by using metal-organic vapor phase epitaxy and measured the pseudo-dielectric functions using variable-angle spectroscopic ellipsometry. We analyzed the pseudo-dielectric functions by using the multi-layer model. The dielectric functions were fitted by using a Holden model dielectric function. We used anisotropic layer modeling for the ZnO thin film, whereas we adopted the approximation of isotropic layer modeling for the Zn1-xMgxO alloys. We also discuss the Mg composition dependence of the bandgap and the binding energy in Zn1-xMgxO alloys, and consider the valence-band ordering in ZnO thin films.The work of H. Lee was supported in part by the Special Equipment Program of the Korean Basic Science Institute through the Korean Science and Engineering Foundation (KOSEF, R23-2002-000-00006-0). The work of G.-C. Yi was supported by the Advanced Environmental Biotechnology Research Center (No. R11-2003-006)

Spectroscopic ellipsometry and absorption study of Zn1-xMnxO/Al2O3 (0 \u3c= x \u3c= 0.08) thin films

We grow Zn1−xMnxO∕Al2O3 (0⩽x⩽0.08)thin films on sapphire (0001) using radio-frequency sputtering deposition method with Ar and various N2 flow rates. We examine the effect of N2 codoping on the band gap and Mn-related midgap absorption of (Zn,Mn)O. Using spectroscopic ellipsometry, we measure pseudodielectric functions in the spectral range between 1 and 4.5eV. Using the model of Holden et al. [T. Holden et al., Phys. Rev. B56, 4037 (1997)], we determine the uniaxial (Zn,Mn)O dielectric function and the E0 band-gapenergy. The fitted band gap does not change appreciably with increasing Mn composition up to 2%. We find a very large broadening of both the E0 band gap and its exciton partner E0x peaks even for less than 2% of optically determined Mn composition. In ellipsometric spectra, we also find Mn-related 3eV optical structure. In particular, optical absorption spectra with varying N2 gas flow rate show that the Mn-related peak intensity decreases with increasing N2 flux. The decrease of the 3eV Mn-related peak intensity is attributed to increasing N2 flow rate and Mn–N hybridization

Dielectric functions and electronic band structure of lead zirconate titanate thin films

We measure pseudodielectric functions in the visible-deep ultraviolet spectral range of Pb(ZrxTi1−x)O3 (x=0.2,0.56,0.82) (PZT), Pb0.98Nb0.04 (Zr0.2Ti0.8)0.96O3, Pb0.91La0.09 (Zr0.65Ti0.35)0.98O3, and Pb0.85La0.15Ti0.96O3 films grown on platinized silicon substrates using a sol-gel method and on (0001) sapphire using a radio-frequency sputtering method. Using a parametric optical constant model, we estimate the dielectric functions(ϵ) of the perovskite oxide thin films. Taking the second derivative of the fitted layer dielectric functions and using the standard critical-point model, we determine the parameters of the critical points. In the second derivative spectra, the lowest band-gapenergy peak near 4 eVis fitted as a double peak for annealed PZTs due to the perovskite phase. As-grown PZTs have mainly pyrochlore phase and the lowest band-gap peak is fitted as a single peak. We also examine the effect of dopants La and Nb, which substitute at Pb and Zr (Ti) sites, respectively. We found three band gaps Ea(∼3.9eV), Eb (∼4.5eV), and Ec (∼6.5eV) in the order of increasing energy. The Ea and Eb band-gap energies were not sensitive to Zr composition. We discuss the change of critical-point parameters for PZTs in comparison to the band-structure calculations based on local-density approximation. The near constancy of the lowest band-gap energy independent of Zr composition is consistent with the band-structure calculations

Fabrication and current-voltage characterization of a ferroelectric lead zirconate titanate/AlGaN∕GaN field effect transistor

We demonstrated ferroelectricfield effect transistors (FFETs) with hysteretic I-V characteristics in a modulation-doped field effect transistors(MODFET)AlGaN∕GaN platform with ferroelectricPb(Zr,Ti)O3 between a GaN channel and a gate metal. The pinch-off voltage was about 6–7V comparable to that of conventional Schottky gate MODFET. Counterclockwise hysteresis appeared in the transfer characteristics with a drain current shift of ∼5mA for zero gate-to-source voltage. This direction is opposite and much more pronounced than the defect induced clockwise hysteresis in conventional devices, which suggests that the key factor contributing to the counterclockwise hysteresis of the FFET is the ferroelectric switching effect of the lead zirconate titanate gate

Reducing time to discovery : materials and molecular modeling, imaging, informatics, and integration

This work was supported by the KAIST-funded Global Singularity Research Program for 2019 and 2020. J.C.A. acknowledges support from the National Science Foundation under Grant TRIPODS + X:RES-1839234 and the Nano/Human Interfaces Presidential Initiative. S.V.K.’s effort was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), Materials Sciences and Engineering Division and was performed at the Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences (CNMS), a U.S. Department of Energy, Office of Science User Facility.Multiscale and multimodal imaging of material structures and properties provides solid ground on which materials theory and design can flourish. Recently, KAIST announced 10 flagship research fields, which include KAIST Materials Revolution: Materials and Molecular Modeling, Imaging, Informatics and Integration (M3I3). The M3I3 initiative aims to reduce the time for the discovery, design and development of materials based on elucidating multiscale processing-structure-property relationship and materials hierarchy, which are to be quantified and understood through a combination of machine learning and scientific insights. In this review, we begin by introducing recent progress on related initiatives around the globe, such as the Materials Genome Initiative (U.S.), Materials Informatics (U.S.), the Materials Project (U.S.), the Open Quantum Materials Database (U.S.), Materials Research by Information Integration Initiative (Japan), Novel Materials Discovery (E.U.), the NOMAD repository (E.U.), Materials Scientific Data Sharing Network (China), Vom Materials Zur Innovation (Germany), and Creative Materials Discovery (Korea), and discuss the role of multiscale materials and molecular imaging combined with machine learning in realizing the vision of M3I3. Specifically, microscopies using photons, electrons, and physical probes will be revisited with a focus on the multiscale structural hierarchy, as well as structure-property relationships. Additionally, data mining from the literature combined with machine learning will be shown to be more efficient in finding the future direction of materials structures with improved properties than the classical approach. Examples of materials for applications in energy and information will be reviewed and discussed. A case study on the development of a Ni-Co-Mn cathode materials illustrates M3I3's approach to creating libraries of multiscale structure-property-processing relationships. We end with a future outlook toward recent developments in the field of M3I3.Peer reviewe