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21.
Comparison of oil and egg tempera paint systems using time-of-flight secondary ion mass spectrometry
Zachary E. Voras Kristin deGhetaldi Brian Baade Eric Gordon Glenn Gates Thomas P. Beebe 《文物保护研究》2016,61(4):222-235
Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is quickly becoming a critical tool in the field of art conservation. This technique provides high-resolution spatial maps of both inorganic and organic components located within cross-sectional samples collected from works of art. With recent advances in surface analysis, ToF-SIMS can now be used to identify specific amino acids present in protein-containing materials as well as fatty acids in drying oils. For example, the detection of the ion fragment associated with the amino acid hydroxyproline can be used to confirm the use of animal glue in a paint sample. As an analytical technique, ToF-SIMS avoids the need for derivatization/silylation reagents, with no interference by the presence of pigments. Furthermore, the layered systems that are often encountered in historical paint samples remain intact throughout the analytical procedure. This allows for the co-localization of organic and inorganic species in specific layers (e.g. egg yolk paint atop a glue ground). Because of this ability to localize the analytical signal to approximately 6?µm or less, the mass spectral information can be used to produce mass-resolved and spatially-resolve images which can be correlated to previous studies of the same samples. In this study, ToF-SIMS was used to analyze a paint cross section obtained from a painting attributed to Raphael, and another from a painting by the Sienese artist Matteo di Giovanni. 相似文献
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Lennart Fischer Joseph Baker Rebecca Rienhoff Bernd Strauß Judith Tirp Dirk Büsch 《Journal of sports sciences》2016,34(17):1637-1642
There is little research investigating the maintenance of perceptual-cognitive expertise in general and even less comparing coaches of different ages. The aim of this study was to test for perceptual-cognitive differences between age groups, licence levels, and their interaction. This study investigated differences in skilled performance between young and middle-aged coaches of three different skill levels. Participants performed an accuracy-oriented pattern recall (mean distance in pixel) and a time-oriented flicker test (mean detection time in ms). There were some significant differences between age groups and between skill groups for both tests, but no interactions. For the pattern recall test, the effect sizes were larger for skill level differences, while for the flicker test effects were larger for ageing. These results suggest coaches are able to maintain accuracy skills better than reaction timed tasks. This is in line with findings on speeded performance in general populations, which show declines with age. Moreover, results also support findings on perceptual expertise in skills where accuracy was important. 相似文献
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Joseph Sanacore 《Clearing house (Menasha, Wis.)》2017,90(4):152-158
Barack Obama's My Brother's Keeper is designed to narrow persistent gaps that boys and young men of color confront often and to help all young people achieve their potential in college and career. An important part of this initiative is comprehensive mentoring that supports students in schools and in communities. Because ethnic-minority students have extremely low graduation rates in high school and college, an essential question is addressed: Can My Brother's Keeper and similar initiatives with a mentoring component be effective in helping minority students to achieve success in elementary and secondary schools and in college? 相似文献
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There is an ongoing debate in the student evaluation of teaching literature about whether an overall rating or factorial dimensions of teaching effectiveness should be used in personnel decisions. Marsh and his colleagues have advocated the use of a weighted average approach to computing overall evaluations. A policy-capturing experiment was carried out where students in three different instructional contexts made overall evaluations of hypothetical instructors based on a manipulation of the teaching factors in Marsh's SEEQ. The results indicated (1) amount learned was consistently the most important factor affecting overall evaluations; (2) course difficulty was consistently the least important factor affecting overall evaluations; and (3) there was a strong similarity among the three groups in the relative importance of the various teaching factors in arriving at an overall evaluation. The implications of this research are discussed, as well as directions for future research. 相似文献
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Marco Snoek Mascha Enthoven Joseph Kessels Monique Volman 《International Journal of Leadership in Education》2017,20(1):26-56
In this case study, we investigate how the development and impact of teacher leadership through a Master’s programme can be supported by a design that encourages boundary crossing activities between schools and universities. The case study focuses on 42 experienced teachers from three vocational colleges who were promoted to senior teacher positions and participated in a Master’s programme. Through individual and focus group interviews, data were collected on how boundary crossing activities can connect professional development and school development, and on favourable conditions for effective boundary crossing. The study shows that strategic alignment and shared ownership between university and school, a collective approach with multiple participants from one school, and the use of boundary objects, created the conditions through which the Master’s programme could serve as a catalyst, stimulating innovation of work practices and development of new leadership practices. The leadership of the senior teachers initiated a development process that shifted from formally mandated forms of leadership to more culturally embedded forms of leadership. This case study leads to a new understanding of design criteria for Master’s programmes and boundary objects that can support the process of developing teacher leadership within schools by facilitating boundary crossing between university and school. 相似文献