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R. P. Clark Einar Lilja Eve Malmqvist Louis Arnaud Reid Edmund King John Downing C. M. Fleming Arnould Clausse G. de Landsheere Vernon Mallinson Paul Nash Tomio Goto M. A. Brimer Rudolf Cohen Gerhard Pause M. J. Langeveld W. E. Vliegenthart Emile Planchard 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》1963,9(3):351-382
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Skedsmo Guri Huber Stephan Gerhard 《Educational Assessment, Evaluation and Accountability》2019,31(2):151-153
Educational Assessment, Evaluation and Accountability - 相似文献
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ABSTRACTChalconatronite, Na2[Cu(CO3)]2·3H2O, is formed as a corrosion product when copper alloys are exposed to sodium carbonate solutions in the air. This also happens when metals come into contact with corroding soda glass which forms alkaline surface films in reaction with humidity from clean air. More often, substantial amounts of formaldehyde are present indoors which react to formate via the Cannizzarro reaction and accumulate over time in the films. Twenty cases of chalconatronite (including two mentioned in the literature) are reported as occurring on heritage objects with glass in contact with copper alloys: Baroque reliquaries with set glass gems, enamel on metal (sixteenth century and a modern replica of intentionally unstable composition), Christmas tree glass baubles with wires, glass buttons with metal shanks, a glass figure with a wire support, miners’ lamps, and a glass framed daguerreotype. These confirmed identifications might help conservators in investigating similar cases to shed more light on the formation conditions. 相似文献
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A sodium copper formate, first described in 2002, can also form on copper alloys with sodium originating from soda glass hydrolysis. The frequent occurrence (50% of 250 cases of glass-induced metal corrosion) is due to the presence of formaldehyde emissions in storage and its direct reaction to formate in the alkaline surface films. The compound can be produced without the presence of acetate when chalconatronite or metal coupons immersed in soda solution are exposed to formaldehyde vapours. The crystal structure, derived from X-ray powder diffraction, yielded the sum formula Cu4Na4O(HCOO)8(OH)2·4H2O. Except for the absence of acetate in the structure, this is in good agreement with the 2002 publication. To assess which kind of combined glass/metal objects are affected, a number of large museum collections were surveyed. Sodium copper formate was detected as a corrosion product using mainly micro-Raman spectroscopy, for instance, on 18 painted Limoges enamels, eight glass vessels with metal mountings, glass beads on metal wire from 11 bridal crowns, nine Christmas tree balls with wire decoration, 40 pieces of jewellery with glass gems, three daguerreotypes, and one miniature with cover glasses. 相似文献
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Copper(II) hydroxide (as the rarely occurring mineral spertiniite) is formed under alkaline, oxidising conditions. It has been observed as a naturally occurring corrosion product of brass in sea water. But most occurrences on copper alloys are due to conservation treatments using basic solutions (sodium hydroxide or ammonia) or to intentional patination. Classical brass centrepieces (c. 1800), ‘cleaned’ with ammonia solution, developed a blue spertiniite patina in gaps, where evaporation was hindered. Additional to the danger of stress corrosion cracking this is another reason now outlawing this treatment. Copper pigment layers will transform to copper hydroxide when exposed to bases. The treatment of basic copper salts with bases has been used intentionally in the production of Bremen blue and similar pigments which can be composed of copper hydroxide as well. 相似文献
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In an attempt to produce more news stories, faster and on different platforms, the national Danish Broadcasting Corporation, DR, has introduced a new workflow. This new workflow is based on principles and practices known internally as “the news engine,” and it has brought with it changes in regards to both the news products, the news processes and the individual news producers. This article is based on newsroom observations, interviews with employees and content analyses, and it shows how the practice of journalism at DR News has been altered in several ways after the implementation of the news engine. The changes in DR News have become the inspiration for other television stations, and the study concludes by discussing how this particular workflow affects the profession of journalism. Rather than a proletarianization of the profession, this study points to a polarization where some journalists experience a deskilling and a decrease in autonomy, while others experience an increase in autonomy as part of a process of reskilling and multiskilling. 相似文献
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