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Surface‐enhanced Raman scattering (SERS) has become a valuable tool for the characterization of trace quantities of environmental toxins. Utilizing established wet chemical synthetic protocols, dogbone‐shaped colloidal gold nanoparticle substrates with sharp features were prepared with regions that exhibit significant SERS enhancement due to the lightning rod effect. These highly enhancing substrates were utilized for the quantitative determination of two dithiocarbamate fungicides by SERS in several complex matrices such as tap water, apple juice, and vegetable juice. Limits of detection and quantitation are reported and compared with Environmental Protection Agency mandated maximum allowable concentrations in tap water. In the case of tap water, limits of detection of 13.39 ± 3.89 nM for thiram and 1.78 ± 0.20 nM for ferbam was achieved. The sensitivity of the solution‐based SERS method decreased with increasing complexity of the matrix in which the limit of detection achieved in apple juice is 47.22 nM for thiram and 11.88 ± 1.38 nM for ferbam and that for vegetable juice is 87.01 ± 2.88 nM for thiram and 36.72 ± 2.90 nM for ferbam. It was found that using the solution‐based SERS method results in sensitivities that are greater than that required by Environmental Protection Agency mandated maximum allowable concentrations for complex matrices such as apple and vegetable juice. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Marcy B. Wood Amy M. Olson Elizabeth J. Freiberg Ruby I. Vega 《School science and mathematics》2013,113(8):390-399
A sample of third‐, fourth‐, and fifth‐grade student responses to the question “What is a fraction?” were examined to gain an understanding of how children in upper elementary grades make sense of fractions. Rather than measure children's understanding of fractions relative to mathematically conventional part–whole constructions of fractions, we attempted to understand children's actions and processes. A small but nontrivial group of children used subtraction (takeaway and removal) as a framework for understanding how fractions were created and written. An analysis of the content of their responses as well as a comparison of the performance of these children with that of children who used other ways of describing fractions suggests that the use of subtraction may be a reasonable (or at least not harmful) way for children to begin to access concepts related to fractions. Also, this study suggests that attention to children's understanding through the lens of children's activity might reveal ways of thinking and insights that are masked when we compare children's thinking in more structured research settings. 相似文献
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Timothy Kyng Leonie Tickle Leigh Wood 《International Journal of Mathematical Education in Science & Technology》2013,44(2):214-231
Software may be used in university teaching both to enhance student learning of discipline-content knowledge and skills, and to equip students with capabilities that will be useful in their future careers. Although research has indicated that software may be used as an effective way of engaging students and enhancing learning in certain scenarios, relatively little is known about academic practices with regard to the use of software more generally or about the extent to which this software is subsequently used by graduates in the workplace. This article reports on the results of a survey of academics in quantitative and financial disciplines, which is part of a broader study also encompassing recent graduates and employers. Results indicate that a variety of software packages are in widespread use in university programmes in quantitative and financial disciplines. Most surveyed academics believe that the use of software enhances learning and enables students to solve otherwise intractable problems. A majority also rate spreadsheet skills in particular as very important for the employability of graduates. A better understanding of the use of software in university teaching points the way to how curricula can be revised to enhance learning and prepare graduates for professional work. 相似文献
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为推进素质教育适应开放式实验教学的要求,大学物理实验可在思想观念、教学内容、教学方法、学生评价等各个方面进行一系列优化和改革。 相似文献
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Yan-Xin Chu Shao-Feng Wu Guo-Hong Yang 《International Journal of Theoretical Physics》2009,48(5):1247-1262
We study the RSII brane world corrected by the four-dimensional scalar curvature and five-dimensional Gauss-Bonnet curvature.
The energy transfer between brane and bulk is also taken into account. Parameterizing the energy transfer, the resulting Friedmann
equation on brane is solved at low energy. It is shown that phantom divide crossing may be achieved in the braneworld model
with wide possibilities, embodying the combined effect of brane-bulk energy transfer, curvature corrections, and the fine-turning
mechanics. 相似文献
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