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Carrier Transfer Induced Photoluminescence Change in Metal-Semiconductor Core-Shell Nanostructures
No full text[[abstract]]Metal-semiconductor core-shell nanostructures have been synthesized to explore the influence of metal nanostructures on the photoluminescence of semiconductors. Up to 40 times enhancement in the emission intensity was observed in the Au–CdS core-shell nanostructures. The mechanism where the excited electrons on Au surface by surface plasmon wave transfer to the conduction band of the CdS shell and recombine with holes in the valence band was proposed to interpret the enhancement. Our model can also be used to explain the quenched emission in FePt–CdS core-shell nanostructures and Au–CdSe nanodumbbells.
Electrically Controlled Surface Plasmon Resonance Frequency of Gold Nanorods
No full text[[abstract]]We have presented the voltage-controlled tuning of plasmonic response of absorption spectra of goldnanorods in liquid crystals. We observe that goldnanorods can be aligned along the rubbed polyimide substrate before applying external voltage. It is found that the transverse mode of goldnanorods shows a blueshift or a redshift when rotating the analyzer parallel or perpendicular to the rubbing direction, respectively, while all longitudinal modes display a redshift behavior. This work offers an easy way to tune the transverse and longitudinal modes of goldnanorods simultaneously, which makes it feasible to establish the color tunable devices.
Photoacoustic Flow Measurements with Gold Nanoparticles
No full text[[abstract]]The hypothesis that quantitative blood flow measurements are feasible with the time-intensity based method in photoacoustic imaging using gold nanoparticles as contrast agent is experimentally tested. The in vitro results show good linearity between the measurements and the theory, thus suggesting the potential of relative photoacoustic flow measurements with gold nanoparticles
Controlled growth of aligned alpha-helical-polypeptide brushes for tunable electrical conductivity
No full text[[abstract]]Polypeptide based molecular diode with high rectification ratio (∼122 at ±0.422 V) is formed by controlling molecular order and orientation. A film of tethered poly(γ-benzyl-L-glutamate) (PBLG) with high degree of molecular orientation was formed by solvent pair (good/bad) treatment. I-V characterization of the well aligned polypeptides showed that the rectification ratio of PBLG was sufficiently large for potential diode and transistor applications.
The nature of learners' science content understandings with the use of on-line resources
No full text[[abstract]]Early research on using the World Wide Web indicated that middle school students did not explore much and used Web tools naively. In response to these challenges, an on-line research engine, Artemis, was designed to provide a permanent workspace and allow students access to preselective on-line resources. This study investigated the depth and accuracy of sixth-grade students' content understandings as well as their use of search and assess strategies when they used on-line resources via Artemis. Eight student pairs from two science classes experienced support from teachers and used scaffolded curriculum materials while completing four on-line inquiry units during 9 months. Multiple sources of data were collected, including video recordings of students' computer activities and conversations, students' artifacts and on-line postings, classroom and lab video recordings, and interview transcripts. Analyses of data showed that students constructed meaningful understandings through on-line inquiry, although the accuracy and depth of their understandings varied. The findings suggest that students might develop accurate and in-depth understandings if they use search and assess strategies appropriately, if resources are thoughtfully chosen, and if support from the learning environment is extensively provided. This research lends evidence to questions regarding the value of students engaging in on-line inquiry.
從情境認知的觀點，?探討實習教師之教學信?與教 學實務的轉變?程
No full text[[abstract]]教學信?是教師在教學情境下對於教學的預設，以及選取最適教學方式的?考標
準。但教師實際教學時，除?教學信?，還會同時考?當時教學條件與本身所具備的教
學實務知?。而??是教學信?或教學實務知??會隨著教師本身的教學實務?斷演
進。這樣的改變在實習教師階段?為明顯。因此本個案研究以情境認知師徒制的觀點，
探討一位高中化學實習教師的信?與教學實務在實習?程中如何轉變，以及資深教師如
何產生影響。資?收集與分析以質性的訪談資?為主，配合個案實際上課的?影、平日
的田野觀察筆記、與教案收集。就整?出變動較大的三項信?與實務，再從中探討此三
項信?與實務的轉變情形。而本研究中這三項信?的確是伴隨實務進?轉變，沒有依像
是?需實務就會轉變的。轉變的趨勢上信?部份，除?個案自己?積的，還能發現有部
分和輔導教師相近。實務部分則大?會趨近輔導教師。但是造成個案轉變的關鍵人物其
實?只是輔導教師還包含其他資深教師。
Supporting scientific modeling practices in atmospheric sciences: Intended and actual affordances of a computer-based modeling tool
No full text[[abstract]]Computer-based learning tools include design features to enhance learning but learners may not always perceive the existence of these features and use them in desirable ways. There might be a gap between what the tool features are designed to offer (intended affordance) and what they are actually used (actual affordance). This study thus aims at investigating how the design features of a computer-based tool supported high school students' modeling practices in atmospheric sciences. Twenty-three 10th graders participated in 16 hours of learning activities by using the tool. We conducted a detailed analysis of students' computer activities, their use of the design features, and their building, testing, analyzing, and evaluating practices. The analysis showed that while some design features such as Variable List and Testing Variables were perceived by students and successfully afforded their enactment of building and analyzing practices, other features including Screen Shot and Edit were rarely used or not utilized in the desirable ways. Based on the findings, this study suggests that the realization of intended affordances may involve factors of learners' characteristics, the nature of learning activities, and the complexity of tasks, and constructs an affordance analysis scheme to inform the design of computer-based learning tools.
Toward an integrated model for designing assessment systems: An analysis of the current status of computer-based assessments in science
No full text[[abstract]]Drawing upon an integrated model proposed by Bennett and Bejar (1998), this review study examined how 66 computer-based science assessments (CBSAs) in basic science and medicine took advantage of advanced technologies. The model regarded a CBSA as an integrated system, included several assessment components (e.g., assessment purpose, measured construct, test and task design, examinee interface, and scoring procedure), and emphasized the interplay among these components. Accordingly, this study systematically analyzed the item presentations of interactive multimedia, the constructs measured, the response formats in formative and summative assessments, the scoring procedures, the adaptive test activities administrated based on the algorithms related to the item response theory (IRT) and other rules beyond IRT, and the strategies for the automatic provision of informative hints and feedbacks in the CBSAs. Our analysis revealed that although only 19 out of 66 assessments took advantage of dynamic and interactive media for item presentations, CBSAs with these media could measure integrated understanding of science phenomena and complex problem-solving skills. However, we also found that limitations in automated scoring may lead to infrequent use of the automated provision of hints and feedbacks with open-ended and extended responses. These findings suggest the interrelatedness of the assessment components, and thus we argue that designers should repeatedly consider the relationships between components of CBSAs to ensure the validity of the assessments. Finally, we also indicate the issues for future research in computer-based assessments.
Teacher Learning---Chemistry Teachers' Use of Learning Technologies in Science Classrooms (I)
No full text[[abstract]]This project is part of a three-year, intensive educational project and developed to
support chemistry teachers’ use of technology in science classrooms. Research on educational
technology has reported that teachers’ use of technology could play a role in their shifting
toward more constructivist pedagogy, and that the use of technology has positive impact on
student learning. If using technology could promote science learning and constructivist
pedagogy, then why are some science teachers still reluctant to use computers with students?
What are the factors that promote or discourage teachers’ use of technology in classrooms?
What are the important features of professional development curricula that could foster
teachers’ use of technology in classrooms? Do teaching practices change over time with the
use of technology? If so, how? What do teachers learn (or what knowledge do they develop)
from their experience of using technology in classrooms? This project is designed to answer
these questions. Using the CIPP model, this project will conduct context evaluation, input
evaluation, process evaluation, and product evaluation. Multiple sources of data (e.g., teacher
surveys, portfolios, and classroom activity recordings) will be collected and examined by
using both qualitative and quantitative methods. Findings of this project will inform
professional developers about what supports and professional development curricula teachers need in order to effectively integrate technology into their teaching practices. This project
will also provide insight into how the use of technology might foster teacher learning and
changes of teaching practices.