4 resultados para commodity

em Helda - Digital Repository of University of Helsinki


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The main aim of the study is to create a many-sided view of dancing in Roman Egypt (1st - early 4th centuries AD) and especially of the dancers who earned their living by dancing as hired performers. Even though dancers and other performers played a central part in many kinds of festivities throughout the ancient world, research on ancient professional dancers is rare and tends to rest on the ancient literature, which reflects the opinions of the elite. Documentary written sources (i.e., papyri, ostraka) the core of the present study are mentioned rather superficially, easily resulting in a stereotypical view of the dancers. This study will balance the picture of professional dancers in antiquity and of ancient dancing in a more general sense. The second aim characterizes this study as basic research: to provide a corpus of written sources from Greco-Roman Egypt on dancing and to discuss pictorial sources contemporary with the texts. The study also takes into account the theoretical discussion that centres on dancing as a nonverbal communicative mode. Dancers are seen as significant conveyors of social and cultural matters. This study shows that dancers were hired to perform especially in religious contexts, where the local associations on the village level also played an important part as the employers of the performers. These performers had a better standard of living in economic terms than the average hired worker, and dancers were better paid than other performers. In the Egyptian villages and towns, where the dancers performed and lived, the dancers do not seem to have been marginal because they were professionals or because of some ethnic or social background. However, their possible marginality may have occurred for reasons related to the practicalities of their profession (e.g., the itinerant life style). The oriental background of performers was a literary topos reflecting partly the situation in the centres of the empire, especially Rome, where many performers were of other than Roman origin. The connection of dancing, prostitution and slavery reflects the essential link between dance, body and gender: dancers are equated with such professions or socio-legal statuses where the body is the focus of attention, a commodity and a source of sensual pleasure; this dimension is clearly observable in ancient literature. According to the Egyptian documentary sources, there is no watertight evidence that professional dancers would have been engaged in prostitution and very little, if any, evidence that the disapproval of the professional dancers expressed by the ancient authors was shared by the Egyptians. From the 4th century onwards the dancers almost disappear from the documentary sources, reflecting the political and religious changes in the Mediterranean east.

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The commodity plastics that are used in our everyday lives are based on polyolefin resins and they find wide variety of applications in several areas. Most of the production is carried out in catalyzed low pressure processes. As a consequence polymerization of ethene and α-olefins has been one of the focus areas for catalyst research both in industry and academia. Enormous amount of effort have been dedicated to fine tune the processes and to obtain better control of the polymerization and to produce tailored polymer structures The literature review of the thesis concentrates on the use of Group IV metal complexes as catalysts for polymerization of ethene and branched α-olefins. More precisely the review is focused on the use of complexes bearing [O,O] and [O,N] type ligands which have gained considerable interest. Effects of the ligand framework as well as mechanical and fluxional behaviour of the complexes are discussed. The experimental part consists mainly of development of new Group IV metal complexes bearing [O,O] and [O,N] ligands and their use as catalysts precursors in ethene polymerization. Part of the experimental work deals with usage of high-throughput techniques in tailoring properties of new polymer materials which are synthesized using Group IV complexes as catalysts. It is known that the by changing the steric and electronic properties of the ligand framework it is possible to fine tune the catalyst and to gain control over the polymerization reaction. This is why in this thesis the complex structures were designed so that the ligand frameworks could be fairly easily modified. All together 14 complexes were synthesised and used as catalysts in ethene polymerizations. It was found that the ligand framework did have an impact within the studied catalyst families. The activities of the catalysts were affected by the changes in complex structure and also effects on the produced polymers were observed: molecular weights and molecular weight distributions were depended on the used catalyst structure. Some catalysts also produced bi- or multi-modal polymers. During last decade high-throughput techniques developed in pharmaceutical industries have been adopted into polyolefin research in order to speed-up and optimize the catalyst candidates. These methods can now be regarded as established method suitable for both academia and industry alike. These high-throughput techniques were used in tailoring poly(4-methyl-1-pentene) polymers which were synthesized using Group IV metal complexes as catalysts. This work done in this thesis represents the first successful example where the high-throughput synthesis techniques are combined with high-throughput mechanical testing techniques to speed-up the discovery process for new polymer materials.

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Even though cellulose is the most abundant polymer on Earth, its utilisation has some limitations regarding its efficient use in the production of bio-based materials. It is quite clear from statistics that only a relatively small fraction of cellulose is used for the production of commodity materials and chemicals. This fact was the driving force in our research into understanding, designing, synthesising and finding new alternative applications for this well-known but underused biomaterial. This thesis focuses on the developing advanced materials and products from cellulose by using novel approaches. The aim of this study was to investigate and explore the versatility of cellulose as a starting material for the synthesis of cellulose-based materials, to introduce new synthetic methods for cellulose modification, and to widen the already existing synthetic approaches. Due to the insolubility of cellulose in organic solvents and in water, ionic liquids were applied extensively as the reaction media in the modification reactions. Cellulose derivatives were designed and fine-tuned to obtain desired properties. This was done by altering the inherent hydrogen bond network by introducing different substituents. These substituents either prevented spontaneous formation of hydrogen bonding completely or created new interactions between the cellulose chains. This enabled spontaneous self-assembly leading to supramolecular structures. It was also demonstrated that the material properties of cellulose can be modified even those molecules with a low degree of substitution when highly hydrophobic films and aerogels were prepared from fatty acid derivatives of nanocellulose. Development towards advanced cellulose-based materials was demostrated by synthesising chlorophyllcellulose derivatives that showed potential in photocurrent generation systems. In addition, liquid crystalline cellulose derivatives prepared in this study, showed to function as UV-absorbers in paper.

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Delay and disruption tolerant networks (DTNs) are computer networks where round trip delays and error rates are high and disconnections frequent. Examples of these extreme networks are space communications, sensor networks, connecting rural villages to the Internet and even interconnecting commodity portable wireless devices and mobile phones. Basic elements of delay tolerant networks are a store-and-forward message transfer resembling traditional mail delivery, an opportunistic and intermittent routing, and an extensible cross-region resource naming service. Individual nodes of the network take an active part in routing the traffic and provide in-network data storage for application data that flows through the network. Application architecture for delay tolerant networks differs also from those used in traditional networks. It has become feasible to design applications that are network-aware and opportunistic, taking an advantage of different network connection speeds and capabilities. This might change some of the basic paradigms of network application design. DTN protocols will also support in designing applications which depend on processes to be persistent over reboots and power failures. DTN protocols could also be applicable to traditional networks in cases where high tolerance to delays or errors would be desired. It is apparent that challenged networks also challenge the traditional strictly layered model of network application design. This thesis provides an extensive introduction to delay tolerant networking concepts and applications. Most attention is given to challenging problems of routing and application architecture. Finally, future prospects of DTN applications and implementations are envisioned through recent research results and an interview with an active researcher of DTN networks.