Tveitite,a new calcium yttrium fluoride     

Sveinung Bergstøl  Brenda B. Jensen  Henrich Neumann 《Lithos》1977,10(1):81-87

Tveitite is a new mineral with formula of the type $\text{Ca}{}_{\mathrm{1?x}}\text{(}\text{Y, RE}\text{)}{}_{\mathrm{x}}\text{F}{}_{\mathrm{2+x}}\text{where}\text{x}$ is approximately 0.3. It is found in a cleavelandite pegmatite at Høydalen in Tørdal, Telemark, S. Norway. The sub-cell is thought to be monoclinic, $\text{a}\text{′=3.924,}\text{b}\text{′=3.893,}\text{c}\text{′=5.525, ß=90°26′,}\text{Z}\text{=2}$. The structure is very similar to that of fluorite and can be described in terms of a pseudo-cubic cell $\text{[1}\text{1}\text{0]}{}_0\text{= 5.527, [110]}{}_0\text{= 5.527,}\text{c}\text{= 5.525, α = 90°18′, γ = 89°37′}$ which contains approximately 1[YCa₃F₉]. The mineral shows twinning in at lest three different directions giving a grating structure probably due to high-low inversion. DTA studies show an inversion point at about 670°C. Material heated above this temperature gives X-ray diffraction patterns corresponding to yttrofluorite (a₀ 5.528). The effect of trivalent ions on the stability of fluorite is discussed.  相似文献   

Local content in emerging growth poles: Local effects of multinational corporations’ use of contract strategies     

Sveinung Eikeland  Trond Nilsen 《Norsk geografisk tidsskrift. Norwegian journal of geography》2016,70(1):13-23

The article analyses ‘local content’ in the strategies of multinational corporations (MNCs). Local content is explored as a link between MNCs and growth poles emerging through contract systems that encourage regional firms to connect with global networks entering a region. With a theoretical starting point in literature on local content and growth pole development, the analysis contributes to developing theories of growth poles by adding novel elements such as MNCs’ procurement strategies and their influence on growth poles through local content in contracts. Three aspects of MNCs’ contracts able to secure local content and thus increase contributions from extraction projects to regional development processes are analysed: (1) whether and how MNC projects are divided into subcontract modules, (2) the position and use of framework contracts, and (3) how transportation costs to sites are included in the biddings. It is concluded that further research on MNCs and local content would need to be aware of the following: factors that facilitate or maintain discrimination between bidders included and not included in global networks; reasons why advantages of geographical proximity are underexposed; and how public authorities (states) establish rules that give equality to local enterprises in their competition with firms entering from outside.  相似文献