Synthesis and formation mechanism of silver nanowires by a templateless and seedless method

Silver nanowires in large quantities can be obtained through a simple method in the absence of a surfactant or polymer and without addition of external seeding nanocrystallites. A plausible mechanism was proposed to elucidate the formation mechanism of silver nanowires based on TEM studies.

Dynamic readout of subdiffraction-limited pit arrays with a silver superlens

Recent theoretical and experimental results suggested that the silver superlens could be constructed through controlling silver thin film thickness and preparation conditions, and applied in subdiffraction-limited optical imaging and optical lithography. In this work, we report another significant application of silver superlens-ultrahigh density optical data storage. With the silver superlens the subdiffraction-limited pit arrays on an optical disk are dynamically read out and the carrier-to-noise ratio can reach 25 dB for the thin film thickness of 46 nm. The readout laser power and readout velocity have little effect on the carrier-to-noise ratio. Additionally, in our experiment the silver thin film thickness needs to be controlled in the range from 20 to 80 nm.

On the dynamic readout of sub-diffraction-limit pit arrays with a silver thin film

Fast moving arrays of periodic sub-diffraction-limit pits were dynamically read out via a silver thin film. The mechanism of the dynamic readout is analysed and discussed in detail, both experimentally and theoretically. The analysis and experiment show that, in the course of readout, surface plasmons can be excited at the silver/air interface by the focused laser beam and amplified by the silver thin film. The surface plasmons are transmitted into the substrate/silver interface with a large enhancement. The surface waves at the substrate/silver interface are scattered by the sinusoidal pits of sub-diffraction-limit size. The scattered waves are collected by a converging lens and guided into the detector for the readout.

Space-selective co-precipitation of silver and gold nanoparticles in femtosecond laser pulses irradiated Ag+, Au3+ co-doped silicate glass

We report on space-selective co-precipitation of silver and gold nanoparticles in Ag+, Au3+ co-doped silicate glasses by irradiation of femtosecond laser pulses and subsequent annealing at high temperatures. The color of the irradiated area in the glass sample changed from yellow to red with the increase of the annealing temperature. The effects of average laser power and annealing temperature on precipitation of the nanoparticles were investigated. A reasonable mechanism was proposed to explain the observed phenomena. (c) 2006 Elsevier Ltd. All rights reserved.

Effect of chromium intermediate layer on properties of silver coatings

Coatings with layer structures of Ag/glass, Ag/Cr/glass, and Ag/Cr-Ag/Cr/glass deposited with magnetron sputtering are investigated. The results indicate that the performance for reflectance, hardness, adherence, and humidity durability of the silver coatings with Ag/Cr/glass and Ag/Cr-Ag/Cr/glass structures are better than pure silver film. In addition, the silver coatings with an Ag/Cr-Ag/glass structure present more advantages than that of the Ag/Cr/glass. Reasons are analyzed accordingly. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

Thickness dependence of structure and optical properties of silver films deposited by magnetron sputtering

A series of silver films with different thickness were prepared under identical conditions by direct current magnetron sputtering. The optical properties of the silver films were measured using spectrophotometric techniques and the optical constants were calculated from reflection and transmission measurements made at near normal incidence. The results show that the optical properties and constants are affected by films' thickness. Below the critical thickness of 17 nm at which Ag film forms a continuous film, the optical properties and constants vary significantly as the thickness of films increases and then tends to a stable value which is reached at 41 nm. X-ray diffraction measurements were carried out to examine the structure and stress evolution of the Ag films as a function of films' thickness. It was found that the interplanar distance of (111) orientation decreases when the film thickness increases and tends to be close to that of bulk material. The compressive strains also decrease with increasing thickness. (C) 2007 Published by Elsevier B.V.

A cicatriz do Tatarana: o sagrado feminino em Grande sertão: veredas

O trabalho analisa, na obra Grande Sertão: Veredas de João Guimarães Rosa (1956), elementos discursivos indicadores de um modo de narrar que ficcionaliza, tanto na forma quanto no teor de sua mensagem, manifestações do sagrado originárias da Antiguidade grega e da tradição judaico-cristã. A partir da analogia entre a obra de Guimarães Rosa e a Odisseia de Homero, tornam-se evidentes vestígios do épico e de modelos clássicos de narrativa que, revestidos do peculiar trabalho da linguagem rosiana, adensam a complexidade do romance. O paralelismo com as Sagradas Escrituras, mais difuso, projeta as ações num patamar dramático, em que se decidem o destino das personagens e a solenidade do discurso memorável. A fundamentação teórica articula o pensamento de Erich Auerbach, André Jolles, Rudolf Otto e também de estudiosos que se dedicaram à obra do autor mineiro, como Kathrin Rosenfield. Esse recorte mostrou a presença do sagrado em microcélulas entretecidas ao emaranhado de histórias e causos que costuram a obra prima de Rosa. A cicatriz da Tatarana alude à cicatriz de Ulisses, sinal revelador da identidade do herói grego e que, no caso do jagunço Riobaldo, desoculta um amor negado por meio da purgação do passado, elaborada numa conversa "unilateral com um suposto interlocutor. Em linguagem mítica e mágica, a figura nebulosa de Diadorim funciona como índice de ambiguidade e, ao mesmo tempo, da revelação alcançada através da morte. A pesquisa, por seu turno, segue as veredas abertas pelo estudo de Tereza Virgínia Ribeiro Barbosa a respeito das mulheres vestidas de sol, metáfora relacionada a Medeia, mas que se projeta na Virgem Maria e numa linhagem de figuras femininas da América Latina ligadas ao sagrado. Verificamos, na perspectiva das transferências culturais do tipo passado místico-mistérico/posteridade fabular, que o discurso de Riobaldo é atravessado por micronarrativas de longa tradição que sincretizam diferentes símbolos exotéricos. O trabalho encerra sua investigação desvendando a dualidade do sertão rosiano, onde impera o embate entre fé e ceticismo, a dúvida e a razão, o amor e o ódio, o masculino e o feminino, que resulta no inacabado, na travessia, a vida como metáfora, no campo das infinitas possibilidades do homem humano

Evolutionary associations between sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) inferred from morphological characters, mitochondrial DNA, and microsatellite markers

The evolutionary associations between closely related fish species, both contemporary and historical, are frequently assessed by using molecular markers, such as microsatellites. Here, the presence and variability of microsatellite loci in two closely related species of marine fishes, sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus), are explored by using heterologous primers from red drum (Sciaenops ocellatus). Data from these loci are used in conjunction with morphological characters and mitochondrial DNA haplotypes to explore the extent of genetic exchange between species offshore of Galveston Bay, TX. Despite seasonal overlap in distribution, low genetic divergence at microsatellite loci, and similar life history parameters of C. arenarius and C. nothus, all three data sets indicated that hybridization between these species does not occur or occurs only rarely and that historical admixture in Galveston Bay after divergence between these species was unlikely. These results shed light upon the evolutionary history of these fishes and highlight the genetic properties of each species that are influenced by their life history and ecology.

Spatial and seasonal abundance of sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) off the coast of Texas, determined with twenty years of data (1987–200

Sand seatrout (Cynoscion arenarius) and silver seatrout (C. nothus) are both found within the immediate offshore areas of the Gulf of Mexico, especially around Texas; however information is limited on how much distributional overlap really occurs between these species. In order to investigate spatial and seasonal differences between species, we analyzed twenty years of bay and offshore trawl data collected by biologists of the Coastal Fisheries Division, Texas Parks and Wildlife Department. Sand seatrout and silver seatrout were distributed differently among offshore sampling areas, and salinity and water depth appeared to correlate with their distribution. Additionally, within the northernmost sampling area of the gulf waters, water depth correlated significantly with the presence of silver seatrout, which were found at deeper depths than sand seatrout. There was also an overall significant decrease in silver seatrout abundance during the summer season, when temperatures were at their highest, and this decrease may have indicated a migration farther offshore. Sand seatrout abundance had an inverse relationship with salinity and water depth offshore. In addition, sand seatrout abundance was highest in bays with direct passes to the gulf and correlated with corresponding abundance in offshore areas. These data highlight the seasonal and spatial differences in abundance between sand and silver seatrout and relate these differences to the hydrological and geological features found along the Texas coastline.

A estandardização dos contratos internacionais e o modelo FIDIC - Silver Book para contratos EPC

No presente trabalho acadêmico se apresentarão as principais características do processo de globalização, passando-se à exposição da relevância do Direito Comparado, até se chegar à análise da adoção de modelos internacionais de contratos como esforço uniformizador, de modo a reduzir riscos e a minorar custos de transação. Na sequência, investigar-se-á o modelo contratual EPC (acrônimo das palavras inglesas Engineering, Procurement and Construction - Engenharia, Gestão de Compra e Construção), originário da prática anglo-saxã, focando-se na análise e na qualificação tipológica do Contrato EPC, comparando-o com institutos existentes na legislação brasileira. Delinear-se-á o contexto de disseminação do Contrato EPC no exterior e sua consolidação no Brasil, amparadas, em larga medida, na necessidade de que - em vultosos projetos de infraestrutura, sobretudo em áreas de investimento em relação às quais os empreendedores desconheçam o ambiente regulatório e a realidade socioeconômica se tenha estatuto privado a transladar ao construtor a maior parte dos riscos atinentes a serviços complexos de engenharia. Enfrentar-se-ão as características essenciais deste modelo contratual, tomando-se como padrão o Conditions of Contract for EPC Turnkey Projects - general conditions, guidance for the preparation of particular conditions, forms of letter of tender, contract agreement and dispute adjudication agreement, recomendado pela Fédération Internationale des Ingénieurs Conseils - FIDIC. Apresentar-se-á como o direito estrangeiro equilibra a assunção dos riscos pelo construtor (Contractor ou Builder), inclusive aqueles, referentes a eventos não antecipáveis (unforeseen risks), inobstante a preservação pelo contratante (Owner) de lato poder de monitoramento e fiscalização (overseeing attributions, key personnel and contract manager approval, step-in rights).

Basque legacy in the New World: on the surnames of Latin American presidents

[EN] In this article we explain the etymology of the surnames of Basque origin that some presidents of Latin American countries have or have had in the past. These family names were created in the language called Euskara, in the Basque Country (Europe), and then, when some of the people who bore them emigrated to America, they brought their surnames with them. Most of the family names studied here are either oiconymic or toponymic, but it must be kept in mind that the oiconymic ones are, very often, based on house-nicknames, that is, they are anthroponymic in the first place. As far as possible, we have related the surname, when its origin is oiconymic or toponymic, to its source, i.e. to the house or place where it was created.