SEASCAPE AND MAN     

Gerhard Friedrich 《The Educational forum》2013,77(4)

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The Penguin     

Gerhard Friedrich 《The Educational forum》2013,77(2)

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Madonna With Child and Stars     

Gerhard Friedrich 《The Educational forum》2013,77(2)

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Sanitary engineering     

Wm.Paul Gerhard 《Journal of The Franklin Institute》1895,139(6):457-475

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Bookreviews     

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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Measuring teaching quality: some key issues     

Skedsmo  Guri  Huber  Stephan Gerhard 《Educational Assessment, Evaluation and Accountability》2019,31(2):151-153

Educational Assessment, Evaluation and Accountability -  相似文献   

When Glass and Metal Corrode Together,VI: Chalconatronite     

Andrea Fischer  Gerhard Eggert  Jörg Stelzner 《文物保护研究》2020,65(3):152-159

ABSTRACT

Chalconatronite, 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   

When Glass and Metal Corrode Together,V: Sodium Copper Formate     

Andrea Fischer  Gerhard Eggert  Robert Dinnebier  Tomče Runčevski 《文物保护研究》2018,63(6):342-355

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   

Copper(II) hydroxide on artefacts: Corrosion,conservation, colourants     

Britta Schmutzler  Gerhard Eggert  Charlotte F. Kuhn-Wawrzinek 《文物保护研究》2017,62(2):61-67

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   

Reliability,validity and fairness—key issues in assessing the quality of teaching,instructional leadership and school practice     

Guri Skedsmo  Stephan Gerhard Huber 《Educational Assessment, Evaluation and Accountability》2018,30(4):343-346

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