Why Do Historical Beeswax Seals Become Brittle Over Time?

ABSTRACT

Mechanical properties of aged beeswax were studied by an indirect measurement, using hydrogenated beeswax as a model material. The adequacy of the model was evaluated by comparison of its chemical composition and thermal properties with those of samples of historical beeswax. It was found that the gradual decrease in content of unsaturated compounds in beeswax contributes significantly to changes of its mechanical properties. As a consequence, beeswax artefacts become increasingly prone to mechanical damage during natural ageing. Understanding the difference between mechanical properties of recent and historical beeswax is primarily important from the point of view of safe handling and storage of such artefacts. Besides, this knowledge could help conservation scientists, e. g. when preparing model samples for testing new conservation methods.     

Special knowledge needs of family enterprises in transition economies: experiences from Slovenia

In many countries throughout the world the majority of enterprises are family ones. Particularities in the development and management of family enterprises create needs for special knowledge. Therefore, in providing knowledge to these enterprises consideration must be given to their complexity, which is derived from the involvement of a family in ownership and management. In this paper, we discuss the importance of knowledge created and transferred from external sources such as counselling, publications, and education and training programs. External sources of knowledge considering the unique characteristics of family enterprises are well developed in many countries with established market economies. In Slovenia and, we believe, in many other former socialist countries, such external sources of knowledge are rare and still developing. The results of our research in Slovenia show that more than two-thirds of family business owners-managers regard such sources of knowledge as unimportant. This paper analyzes the reasons for such a finding.     

Dubious Early Medieval Jewels from Matzhausen (Bavaria): New Material and Technological Investigations

ABSTRACT

A controversial set of elite jewels assumed to be of early medieval period, recovered in 1937–1938 from a burial site in Matzhausen (northeastern Bavaria) was investigated to determine their technological coherency as well as their authenticity. The discovery of these jewels was exploited by German nationalists to argue that the material culture observed in Bohemia and Moravia in the ninth century had Germanic roots. The circumstances of their discovery, however, remain unclear. Research in archives demonstrated the involvement of the SS Ahnenerbe organisation in the recovery of the jewels. Are these jewels authentic or are they forgeries manufactured or modified by a modern craftsman to serve German expansionist nationalism? Three jewels recovered in the grave – a gombik (hollow spherical pendant), an earring with chainlet, and a zoomorphic figurine – were investigated using scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDX), X-radiography, and stereomicroscopy. The investigation revealed a very heterogeneous set of objects with respect to technology and state of preservation. It also uncovered repairs and past invasive interventions involving modern metal and solder. Comparison with similar types of jewels from Bohemia and Moravia points to important differences in construction and technology, which confirms the uniqueness of this set of objects and casts suspicion on their authenticity.     

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

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.     

Action research through lesson study for the reconstruction of teachers’ practical knowledge. A review of research at Málaga University (Spain)

ABSTRACT

This article aims to set out our discussions, reflections and research at Málaga University (Spain) in relation to Lesson Study (LS), as a cooperative action research process. The paper aims to summarise the main findings of ten years of research, addressing the concepts and dilemmas found both in forming teachers’ practical thinking and in the complex processes of reconstruction through LS. The results of our research provide evidence that it is a useful way to deal with the reconstruction of teachers’ practical knowledge in teacher training. Teachers’ practical knowledge should be more broadly seen as an active combination of theoretical knowledge, procedural knowledge and skills, attitudes, emotions, believes, and values: i.e. teachers’ practical thinking. Most of these personal and professional resources are unconscious, or rather sub-conscious. Changes in teachers’ practical thinking require more practical experience and reflexion: a dialectical process based around two key components: theorisation of practice and experimentation of reconstructed theory. The results of our research show that these dialectical process could be developed with LS as a particular way of developing AR, adding a complex, systematic, flexible and cooperative way of dealing with specific and contextual curricular innovation projects. We therefore conclude that LS could be a very useful path to follow in reconstructing teachers’ practical thinking from within, strengthening the professional teaching community.     

Empirical Research on Ethnic Minority Students: 1995–2009

Ethnic minority disproportionality has been a topic of extensive discussion and research for many years. In 1997, Artiles, Trent, and Kuan conducted a seminal review of the special education research literature to identify how often researchers report and disaggregate data in ways that would support conclusions about specific ethnic minority groups. These authors found alarmingly low rates of publication on identifiable minority groups. The purpose of this review is to replicate the work of Artiles et al. and extend this literature analysis to the subsequent 15‐year period (1995–2009). We found increases in the proportion of articles reporting ethnic minority information 15 years following the Artiles et al. publication. Discussion focuses on the gap in our knowledge of evidence‐based practices for ethnic minority students in special education.     

A novel way of liver preservation improves rat liver viability upon reperfusion

Background/aim： Currently, the liver is cold-preserved at 0-4 ℃ for experimental and clinical purposes. Here, we investigated whether milder hypothermia during the initial phase of the preservation period was beneficial for liver viability upon reperfusion. Methods： In the first set of experiments, rat livers were preserved either conventionally in clinically used histidine-trypthopan-ketoglutarate （HTK） solution （Group A： 45 min and Group B： 24 h） or by slow cooling HTK solution （from 13 ℃ to 3 ℃） during the initial 45 min of preservation （Group C： 24 h）. In the second set of experiments, additional groups of livers were evaluated： Group BB-preservation according to Group B and Group CC-preservation according to Group C. Further, some livers were preserved at 13 ℃ for 24 h. Livers were then reperfused using a blood-free perfusion model. Results： Bile production was approximately 2-fold greater in Group C compared to Group B. Alanine transaminase （ALT） and aspartate transaminase （AST） release into perfusate were 2-3-fold higher in Group B compared to Group C. No significant differences were found in ALT and AST release between Group C and Group A. Livers in Group CC compared to Group BB exhibited significantly lower portal resistance, greater oxygen consumption and bromosulfophthalein excretion into bile and lower lactate dehydrogenase （LDH） release into perfusate. Histological evaluation of tissue sections in Group BB showed parenchymal dystrophy of hepatocytes, while dystrophy ofhepatocytes was absent in Group CC. Livers preserved at 13 ℃ for 24 h exhibited severe ischemic injury Conclusion： These results suggest that the conventional way of liver preservation is not suitable at least for rat livers and that slow cooling of HTK solution during the initial phase of cold storage can improve liver viability during reperfusion.