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Eva Kotulanov Petr Bezdi
ka David Hradil Janka Hradilov Silvie varcov Tom Grygar 《Journal of Cultural Heritage》2009,10(3):367-378
Interactions of lead-based pigments with a number of inorganic salts, one of the most dangerous degradation agents of wall paintings, were studied under laboratory conditions. The results were used to interpret colour changes observed in 11th century frescoes from the church of Saint George in Kostoľany pod Tríbečom, the oldest preserved wall paintings in Slovakia. Interactions of selected pigments (lead white, massicot, red lead) with different salt solutions were performed within long-term laboratory experiments. We used a selection of naturally occurring salts (Na2SO4, MgSO4, CaSO4, NaCl, NaNO3, Ca(NO3)2, Na2CO3, K2CO3 and urea) and, additionally, a range of synthetic salts that are often applied to the wall paintings during their cleaning and conservation (NaHCO3, KHCO3, (NH4)2CO3, NH4HCO3). The reaction products were identified by X-ray powder diffraction. Red lead (Pb3O4) has a tendency to darken in all salt solutions containing dissolved atmospheric CO2 due to disproportionation to plattnerite (PbO2) and cerussite (PbCO3). Massicot (PbO) in a wet state reacts with atmospheric CO2 to form hydrocerussite and finally cerussite. Lead white (PbCO3 and Pb2CO3(OH)2) reacts with sulphates, carbonates and chlorides to form their respective salts in high yield and, sometimes, without any apparent colour change. Samples taken from the dark brown parts of the wall paintings in Saint George's church were analysed using laboratory X-ray powder microdiffraction. The presence of hydrocerussite, cerussite, plattnerite and lead magnesium carbonate was revealed. According to the results of laboratory experiments, the original lead-based pigment of the now darkened parts was red lead. 相似文献
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Eva Alerby 《Environmental Education Research》2000,6(3):205-222
This article attempts to visualise the way in which children and young people think about a specific topic, namely the environment. The aim is to make the thinking of children and young people available and to interpret the meaning of their thoughts about our environment. The theoretical roots of the study are to be found within the phenomenology of the lifeworld. The study is based on empirical material consisting of drawings produced by 109 children and young people, combined with subsequent oral comments. During the drawing analysis different structures and patterns gradually crystallised, and eventually four different themes emerged, consisting of thoughts which focus on the following: the good world, the bad world, the dialectics between the good and the bad world, and symbols and actions protecting the environment. It can be stated that the results which emerged, in the form of the thoughts of the children and young people on the environment, reflect a thinking characterisedby many nuances, such as clean and unspoilt nature in different manifestations, the need for human beings to use nature for recreation and well-being, environmental destruction in different forms, and direct or indirect ways of taking care of the prevailing environmental situation. 相似文献
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Gunvor Birkeland Wilhelmsen Monica L. Aanstad Eva Iren B. Leirvik 《Support for Learning》2015,30(2):134-149
This article presents experiences from vision research implemented in education and argues for the need for teachers with visual competence and insight into suitable methods for stimulation and learning. A new type of continuing professional development (CPD) focuses on the role of vision in children's learning and development, the consequences of frequently occurring vision disturbances and related new educational possibilities. Participating teachers undertake a period of practical teaching training in their home community. Two students' cases visualise the need to break out of the narrow definition of visual impairment and become capable of evaluating the visual challenges affecting many pupils and their learning. The two cases presented represent various issues of visual challenges; both reached a better functional level, including better reading, following improved vision after the educational interventions. These results illustrate that vision competence in schools is most useful and ought to be widely accessible. 相似文献
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We report results of two studies on metacognitive accuracy with undergraduate education students. Participating students were asked to judge their personal performance in a multiple-choice exam as well as to state their confidence in their performance judgement (second-order judgement [SOJ]). In each study, we compared four conditions that differed in the type of the presented 5-point confidence scale for SOJs. In Study 1, four bipolar scales with different labels were applied; in Study 2, unipolar and bipolar scales were implemented. The results of Study 1 with N?=?420 students show that undergraduates on average provided accurate performance estimations. However, students were not aware of their judgement accuracy, shown by a low fit of SOJ and judgement accuracy. In addition, the type of provided scale significantly influenced the SOJs. Study 2 with N?=?348 students replicated the findings of the first study and gave further insight into the effects of uni- vs. bipolar response scales. 相似文献
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