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ABSTRACTConservation of wooden objects exposed outdoors is extremely difficult and complex due to their constant exposure to fluctuating weather conditions and biological degradation. Filling the gaps in such objects requires the use of specific materials that in particular can adapt to changes in wood dimensions in response to humidity variations. Various materials have been used so far for filling voids in wooden artefacts but none of them was entirely suitable. Therefore, the authors have attempted to provide the basic characteristics of the selected commonly used filling materials based on pine wood powder or glass microballoons as fillers and Paraloid® B-72, Klucel® G, or glutin glue as binders, as the first step in research aiming at developing new and more appropriate gap-fillers. Special attention was paid to the dimensional stability of filling materials upon drying and exposure to water vapour and liquid water. The overall results indicate that among the examined fills those consisting of Paraloid® B-72 and glass microballoons revealed best properties as they were relatively dimensionally stable upon drying and exposure to moisture – despite high absorption of water – and were quite easy to finish. Generally, better properties were observed for filling materials containing higher concentrations of adhesives and these materials will be modified in the next step of the research. Since the main drawbacks of the examined gap-fillers were low water resistance, poor dimensional stability upon drying or exposure to water vapour or liquid water, and fragility or friability, future research into their modification will head towards improvement of the above-mentioned properties. 相似文献
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Marianela Navarro Carla Förster Caterina González Paulina González-Pose 《International Journal of Science Education》2016,38(9):1459-1482
Understanding attitudes toward science and measuring them remain two major challenges for science teaching. This article reviews the concept of attitudes toward science and their measurement. It subsequently analyzes the psychometric properties of the Test of Science-Related Attitudes (TOSRA), such as its construct validity, its discriminant and concurrent validity, and its reliability. The evidence presented suggests that TOSRA, in its Spanish-adapted version, has adequate construct validity regarding its theoretical referents, as well as good indexes of reliability. In addition, it determines the attitudes toward science of secondary school students in Santiago de Chile (n?=?664) and analyzes the sex variable as a differentiating factor in such attitudes. The analysis by sex revealed low-relevance gender difference. The results are contrasted with those obtained in English-speaking countries. This TOSRA sample showed good psychometric parameters for measuring and evaluating attitudes toward science, which can be used in classrooms of Spanish-speaking countries or with immigrant populations with limited English proficiency. 相似文献
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Andr&#; Chiara Lindstr&#;m Paulina Arzarello Ferdinando Holmqvist Kenneth Robutti Ornella Sabena Cristina 《International Journal of Science and Mathematics Education》2013,13(2):237-259
We use eye tracking as a method to examine how different mathematical representations of the same mathematical object are attended to by students. The results of this study show that there is a meaningful difference in the eye movements between formulas and graphs. This difference can be understood in terms of the cultural and social shaping of human perception, as well as in terms of differences between the symbolic and graphical registers.
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How well does the UK corporate governance and financial system (CG&FS) support and encourage innovation? Each CG&FS faces four challenges which vary by sector: novelty, reconfiguration, visibility and spill-overs. High novelty in technologies and markets requires high industry-wide expertise; need for radical reconfiguration requires strong pressure for shareholder value. Low visibility of innovation processes requires shareholder engagement; high spill-overs to and from stakeholders require substantial stakeholder inclusion. The UK CG&FS is rated in these terms against the US and ‘insider’ economies, drawing on recent fieldwork, and the ratings are shown to account well for the relative R&D intensity and specialisation of UK-owned firms. 相似文献
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Katya Vargas-Ortiz Victoriano Pérez-Vázquez Arturo Figueroa Francisco J. Díaz Paulina G. Montaño-Ascencio 《European Journal of Sport Science》2018,18(2):226-234
In recent years, prevalence of obesity in children and adolescents has increased. A strategy for prevention and management of obesity is aerobic training (AT) due to its effectiveness to decrease fat mass. AT increases the content of SIRT3, a mitochondrial protein that increases the expression of PGC-1α and NFR1, thereby enhances mitochondrial function and metabolic health. Resistance training (RT) provides metabolic benefits but its effect on SIRT3 content is unknown. To compare the effect of AT and RT on SIRT3, PGC-1α and NRF-1 protein levels in skeletal muscle of sedentary obese adolescents. Twenty-seven sedentary obese male adolescents (age: 16.7?±?0.9 years; BMI: 33.7?±?4.3?kg/m2) completed a 1-month control period prior to randomization to one of two supervised exercise protocols: AT (3 days/week, 40 min/day, 70–80% peak heart rate) or RT (3 days/week, 11 exercises, 2 sets/exercise, 12 repetitions/set) for 12 weeks. Biopsies were obtained from the vastus lateralis muscle before and after 12 weeks to analyse SIRT3, PGC-1α and NRF-1 proteins content. Peak oxygen consumption (VO2peak) and anthropometric variables were evaluated before and after training. AT increased SIRT3 content, which was associated with improvements in PGC-1α content and body fat percentage. RT did not affect SIRT3 or PGC-1α. VO2peak increased only in AT. The increase in muscle mitochondrial SIRT3 was observed only following AT. In contrast, RT increased muscle mass without improving SIRT3 in obese male adolescents. 相似文献