En raison de l’hétérogénéité et de l’extravagance de leur contenu, les lapidaires ont souvent été délaissés et restent, encore à ce jour, très peu considérés dans les études sur la littérature médiévale. Le nombre important de manuscrits répertoriés attestent pourtant de leur grande popularité et de la place qu’occupaient les pierres précieuses dans la société et la littérature médiévales. Le lapidaire anonyme tanscrit par le manuscrit Paris, BnF, fonds français, 2007, un lapidaire en prose daté du XVe siècle, n’est à ce jour abordé que dans une seule étude, celle de Barbara Geromel, qui s’est intéressée surtout à un autre témoin (le Turin, Biblioteca Reale, Varia 110) dont le contenu – même s’il est incomplet – correspond en tout point à celui du manuscrit de Paris. Ce lapidaire en prose s’inscrit dans une histoire longue et riche, celle des pierres précieuses depuis l’Antiquité, mais s’en démarque également par son organisation complexe de la matière, puisqu’il adopte de manière partielle et imparfaite le paradigme alphabétique, jusqu’alors très peu employé dans les encyclopédies dû aux tensions qu’il incarnait vis-à-vis l’ordre théologique. Témoin matériel d’une sphère plus considérable encore – celle de l’encyclopédisme médiéval –, ce lapidaire participe à la compilation du savoir de jadis et invite à une étude plus approfondie, à la fois de la matière qu’il recèle, de ses sources, issues d’une quantité importante de traditions manuscrites, et de son classement alphabétique. / Regarding the heterogeneity and extravagant nature of their content, the lapidaries have too often been put aside from studies concerning medieval literature, and, still to this day, only a few of them have been studied by scholars. However, the very high number of known manuscripts of such texts does tell us a lot about the popularity and the role played by precious gems within medieval society and litterature. The prose lapidary copied in ms Paris, BnF, fonds français, 2007, a prosaic lapidary dated from the XVth century, has yet only been mentioned once, in a study by Barbara Geromel, who was mostly interested by another manuscript – albeit incomplete – of the same text : ms Turin, Biblioteca Reale, Varia 110. The content remaining in this manuscript corresponds precisely to the one found within the Paris manuscript. This manuscript written in prose represents one single step in a long and rich history (the tradition of describing precious stones dating back to the Antiquity). Nervertheless, it also differs from this tradition by its complex inner organisation of the subject, since it puts to use to this effect an imperfect and incomplete alphabetical paradigm as a mean of classification, an unpopular paradigm at the time, as it embodied elements difficult to correlate with the theological order. This lapidary, a material witness of an even larger intelectual context – the world of mediaeval encyclopedism –, participates to the compilation of knowledge from older times, and calls for deeper studies of its general content, sources (themselves coming from varied manuscript traditions) and usage of an alphabetical classification.

aaaaaRare earth elements (Sc, Y and group 15 lanthanides) and their compounds currently have significant practical use in metallurgy, glass industry, as highly active catalysts for the production of so-called. NiMH batteries, alloys for the manufacture of permanent magnets and e.g. moderators rods in the nuclear energy, but above all they have an irreplaceable role in modern electronics for phosphors TV screens, CRT earlier today, PDP and LCD monitors and displays, tablets, mobile phones etc., which give them a high-quality picture and sound. Unlike most base and precious metals are concentrated in the conquerable ore deposits, occur in the form of compounds as part of mixed minerals in the rarely economically exploitable concentrations, a mining and processing is costly and negative impacts on the environment, paradoxically towards the title but their overall content in the crust is relatively high, the average concentration in the range of about 150 to 220 ppm. The main world producer of REE, China, in 2010, significantly reduced exports by 40 %, making prices of some REE increased up to 1500 % during the month. Demand for REE is growing, so often talks about the recycling of valuable materials back into production, as called. "Urban mining", ie "urban mining", thereby reducing the amount of...

Text in English / The purpose of this study was to establish the vulnerabilities of the security control measures that are being used at Impala Platinum mines and refinery to prevent the theft of Platinum Group Metals (PGMs). It is important to ensure that the security control measures in place are effective and efficient in preventing the occurrence of such theft. The research examined the security risk management approach to the prevention of theft of PGMs and the causes of theft of PGMs by organised crime syndicates operating in South Africa and abroad. The study found that Impala Platinum employees, in collusion with contractors and members of mine security services, are involved in the theft of PGMs. To achieve the goals and objective of the research study, effective security control measures were identified that will help Impala Platinum mines and refinery to overcome the risks and challenges related to the theft of PGMs. / Security Risk Management / M. Tech. (Security Management)