99 resultados para tetragonal tungstênio bronze


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Self-assembly of monodisperse, silica-encapsulated, face-centered tetragonal FePt nanoparticles forms closely packed 2D arrays (see figure). Placing monodisperse FePt nanoparticles in silica nanocapsules allows the transition from a disordered face-centered cubic phase to a ferromagnetic crystalline face-centered tetragonal structure at elevated temperature without severe sintering. These materials are potential candidates for the generation of ultrahigh-density magnetic recording media.

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The Bronze Age barrows on the downs of southern England have been investigated and discussed for nearly 200 years, but much less attention has been paid to similar structures in the areas of heathland beyond the chalk and river gravels. They were built in a phase of expansion towards the end of the Early Bronze Age, and more were constructed during the Middle Bronze Age. They have a number of distinctive characteristics. This paper considers the interpretation of these monuments and their wider significance in relation to the pattern of settlement. It also discusses the origins of field systems in lowland England.

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Finds of metalwork always raise the question of why they were deposited: a smith's collection, a concealed hoard or a votive offering? Findspots in water suggest offerings, since they would be awkward to retrieve. But understanding the context of deposition means knowing the prehistoric environment. The Fenland area of England has many Bronze Age sites, and deposits of metalwork and a well-mapped ancient environment too. Putting all three together the authors begin to assemble a grammar of deposition: swords and rapiers in rivers, some mixed collections placed in still water and others on once-dry land with burnt mounds.

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Activity within caves provides an important element of the later prehistoric and historic settlement pattern of western Scotland. This contribution reports on a small-scale excavation within Croig Cave, on the coast of north-west Mull, that exposed a 1.95m sequence of midden deposits and cave floors that dated bewteen c 1700 BC and AD 1400. Midden analysis indicated the processing of a .... 950 BC, a penannular copper bracelet a discrete ritual episode within the cycle of otherwise potentially mundane activities. Lead isotope analysis indicates an Irish origin for the copper ore. A piece of iron slag within later midden deposits, dated to c 400 BC, along with high frequencies of wood charcoal, suggest that smithing or smelting may have occurred within the cave. High zinc levels in the historic levels of the midden c AD 1200 might indicate intensive processing of seaweed.

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The use of ionic self-assembly, a facile noncovalent approach, to access non-conventional block copolymer morphologies, including tetragonal and helical structures, from a combination of polyferrocenylsilane diblock copolymer polyelectrolytes and AOT-based surfactants, is described.

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This paper examines the significance of seventeen later Bronze Age wells found during construction at Swalecliffe, in north-east Kent. The unusual depth of the features made for exceptional preservation of wooden structural elements, including steps and revetments, demonstrating rare evidence for woodworking and woodmanship. Extensive biological remains facilitated environmental reconstruction, and a lengthy dendrochronological sequence corroborates the internationally important Flag Fen chronology. Dendrochronological and radiocarbon dates demonstrate around 500 years of seemingly continuous use and replacement of wells. Votive deposits and apparatus used for water collection provide glimpses of small-scale ritual and domestic activities. The highly unusual concentration of wells is compared to contemporary sites regionally and elsewhere.