The financialisation of primary sector MNEs

Since the 1990s, three major developments occurred within the primary sector. First, in a rather short time period, resource prices have displayed major changes. During the 1990s, price indices for food, metals and energy resources were more or less stable. Things changed at the dawn of the new millennium and prices peaked around 2008. After the outbreak the financial and economic crisis, prices dropped and have shown a rather volatile path since then. Second, in the same period, state-owned-enterprises and parastatals emerged to become global players. Mainly, companies from the so-called BRICS (e.g. PetroChina, Gazprom, Petrobas) assumed leading roles. Third, a concentration of capital and market power occurred due to multiple mergers and acquisitions (M&A). These multinational enterprises (MNEs) are listed as some of the biggest companies worldwide. Within their respective commodity chains, they hold dominant and defining positions.To understand and analyse these developments, a framework that draws on Marxist political economy is elaborated. By combining the debate on rent theory with the discussion on financialisation, that is, capital accumulation based on fictitious capital, the following arguments can be made. On the one hand, M&As are partially a response to the increasing influence of financial actors on natural resource markets. Simultaneously, the financial sector induced a change in the corporate governance of MNEs towards the principle of shareholder value. Moreover, the conflict between extractive companies and natural resource owners (that is, nation states) over the distribution of rents gained weight due to increasing prices. Strategic M&A allowed MNEs to enhance their bargaining position and secure access to resource reserves. On the other hand, it is characteristic of the companies embedded in the primary sector to follow a mixed accumulation strategy based on both the accumulation of fictitious capital  (rent appropriation) and productive capital. Precisely, the access to, and control over, pseudo-commodities define the long-term success of these enterprises. By means of M&A, this access and control are secured, an outcome which supports the ability of MNEs to generate revenue based on rents. Therefore, recent developments in natural resource industries are only partially induced by a general, macroeconomic financialisation.Keywords: Natural resources; Mining; Oil; Food; Primary sector; MNE; Financialisation; Rent theory; Critical political econom

Persistent luminescence in rare-earth doped nitrido-silicates

Some luminescent materials are able to continue emitting light for hours after they have been excited, a phenomenon known as persistent luminescence. The majority of persistent phosphors known today are based on aluminates or silicates and emit in the blue or green region of the visible spectrum. Orange or red phosphors, strongly desired for emergency signage and medical imaging, are scarce. We prepared the yellowish-orange nitrido-silicates M2Si5N8:Eu,R (M = Ca, Sr, Ba), and their rare-earth codoped variants (R = Nd, Dy, Sm, Tm) through a solid state reaction, and investigated their luminescence and afterglow properties. Persistent luminescence is present in all the prepared samples, but the brightness and duration of the afterglow strongly depend on the host material, the codopant and the choice and ratio of the starting products. This demonstrates the importance of charge carrier traps that are suitably located (both physically and energetically), since these govern the maximum light storage and release capabilities of a persistent phosphor. The number and depth of these traps are estimated from the thermoluminescent glow curve, the integrated light output and the decay profile. Of all the prepared materials, Ca2Si5N8:Eu,Tm is the most promising persistent phosphor with a bright orange afterglow that remains visible for about an hour

Persistent luminescence in Eu2+-doped compounds : a review

In 1996, Matsuzawa et al. reported on the extremely long-lasting afterglow of SrAl2O4:Eu2+ codoped with Dy3+ ions, which was more than 10-times brighter than the previously widely used ZnS:Cu,Co. Since then, research for stable and efficient persistent phosphors has continuously gained popularity. However, even today - almost 15 years after the discovery of SrAl2O4:Eu2+, Dy3+ - the number of persistent luminescent materials is still relatively low. Furthermore, the mechanism behind this phenomenon is still unclear. Although most authors agree on the general features, such as the existence of long-lived trap levels, many details are still shrouded in mystery. In this review, we present an overview of the important classes of known persistent luminescent materials based on Eu2+-emission and how they were prepared, and we take a closer look at the models and mechanisms that have been suggested to explain bright afterglow in various compounds