896 resultados para Gold coins


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Vol. 6, unanalyzed publications, cont. Records of Buckinghamshire, by the Architectural and Archaeological Society for the County of Buckingham (1854). Includes articles: Ancient British gold coins found in Whaddon Chase. Antiquities of the Chiltern Hills / W.J. Burgess. Aylesbury Church in 1848 : architect's report / Geo. Gilbert Scott. A letter from G.G. Scott, Esq., on the supposed Saxon work at Iver and at Wing. Church bells / Robert Eaton Batty. The desecrated churches of Buckinghamshire [cont.]. Drayton Beauchamp / by W. Hastings Kelke. St. Mary's, Ashendon, Bucks. / by Frederick George Lee. Earth-works at Hampden and Little Kimble / by Boughey Burgess. Hilldesden Church -- Transactions of the St. Albans Architectural and Archaeological Society (1851). Includes article: Notice of a seal formed of bone, discovered in the Abbey Church, St. Albans ... / by Albert Way.

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La historia de la moneda en la Castilla medieval ha estado siempre mediatizada por la convivencia no siempre armónica entre dos sistemas monetarios muy diferentes. Uno basado en la plata, de origen europeo, otro centrado en el oro, de raíces árabes. La necesidad de conectar y de establecer unas equivalencias entre ellos se convirtió pronto en una necesidad, máxime cuando las monedas de oro incrementaron sus variantes. En esta compleja situación aparecen mencales y maravedís citados conjuntamente en muchos fueros: Zorita, Uclés, Cuenca,... sin que su naturaleza quede del todo clara. Este artículo compara estas referencias y analiza las equivalencias que los unen. Como colofón al trabajo podemos afirmar que los maravedís citados en cada texto corresponden a monedas áureas de distinto peso y valor mientras el mencal es identificado con un ponderal de oro que los relaciona.

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We report large photoluminescence (PL) enhancement in Eu(3+)-doped GeO(2)-Bi(2)O(3) glasses containing gold nanoparticles (NPs). Growth of approximate to 1000% in the PL intensity corresponding to the Eu(3+) transition (5)D(0)->(7)F(2), at 614 nm, was observed in comparison with a reference sample that does not contain gold NPs. Other PL bands from 580 to 700 nm are also enhanced. The enhancement of the PL intensity is attributed to the increased local field in the Eu(3+) locations due to the presence of the NPs and the energy transfer from the excited NPs to the Eu(3+) ions.

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We have investigated the structure of disordered gold-polymer thin films using small angle x-ray scattering and compared the results with the predictions of a theoretical model based on two approaches-a structure form factor approach and the generalized Porod law. The films are formed of polymer-embedded gold nanoclusters and were fabricated by very low energy gold ion implantation into polymethylmethacrylate (PMMA). The composite films span (with dose variation) the transition from electrically insulating to electrically conducting regimes, a range of interest fundamentally and technologically. We find excellent agreement with theory and show that the PMMA-Au films have monodispersive or polydispersive characteristics depending on the implanted ion dose. (C) 2010 American Institute of Physics. [doi:10.1063/1.3493241]

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Shallow subsurface layers of gold nanoclusters were formed in polymethylmethacrylate (PMMA) polymer by very low energy (49 eV) gold ion implantation. The ion implantation process was modeled by computer simulation and accurately predicted the layer depth and width. Transmission electron microscopy (TEM) was used to image the buried layer and individual nanoclusters; the layer width was similar to 6-8 nm and the cluster diameter was similar to 5-6 nm. Surface plasmon resonance (SPR) absorption effects were observed by UV-visible spectroscopy. The TEM and SPR results were related to prior measurements of electrical conductivity of Au-doped PMMA, and excellent consistency was found with a model of electrical conductivity in which either at low implantation dose the individual nanoclusters are separated and do not physically touch each other, or at higher implantation dose the nanoclusters touch each other to form a random resistor network (percolation model). (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3231449]

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We have investigated the fundamental structural properties of conducting thin films formed by implanting gold ions into polymethylmethacrylate (PMMA) polymer at 49 eV using a repetitively pulsed cathodic arc plasma gun. Transmission electron microscopy images of these composites show that the implanted ions form gold clusters of diameter similar to 2-12 nm distributed throughout a shallow, buried layer of average thickness 7 nm, and small angle x-ray scattering (SAXS) reveals the structural properties of the PMMA-gold buried layer. The SAXS data have been interpreted using a theoretical model that accounts for peculiarities of disordered systems.

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PMMA (polymethylmethacrylate) was ion implanted with gold at very low energy and over a range of different doses using a filtered cathodic arc metal plasma system. A nanometer scale conducting layer was formed, fully buried below the polymer surface at low implantation dose, and evolving to include a gold surface layer as the dose was increased. Depth profiles of the implanted material were calculated using the Dynamic TRIM computer simulation program. The electrical conductivity of the gold-implanted PMMA was measured in situ as a function of dose. Samples formed at a number of different doses were subsequently characterized by Rutherford backscattering spectrometry, and test patterns were formed on the polymer by electron beam lithography. Lithographic patterns were imaged by atomic force microscopy and demonstrated that the contrast properties of the lithography were well maintained in the surface-modified PMMA.