Transparent colloid containing upconverting nanocrystals: An alternative medium for three-dimensional volumetric display

We report an alternative medium of transparent upconverting colloid containing lanthanide ion doped NaYF4 nanocrystals for three-dimensional (3D) volumetric display. The colloids exhibit tunable upconversion luminescence with a wide spectrum of colors by adjusting the doping concentrations of the nanocrystals and the compositions of the colloids. Our preliminary experimental result indicates that an upconverting colloid-based 3D volumetric display using a convergent, near infrared laser beam to induce a localized luminescent spot near the focus is technically feasible. Therefore arbitrary 3D objects can be created inside the upconverting colloid by use of computer controlled 3D scanning systems. (C) 2008 Optical Society of America

Communication mer-lagune: impact d'une réouverture sur l'ichtyofaune de la lagune Ebrié (Côte d'Ivoire)

The artificial reopening of the lagoon inlet, made in Grand-Bantam in September 1987 in order to reduce the aquatic weeds proliferation, induced some environmental and fish communities alterations in the eastern part of the Ebrié lagoon (Côte d'Ivoire). A preliminary field survey made in May 1988 shows an increase in the salinity rate and an increase of the marine component among fish communities, when compared to the former ecological state of this lagoon area (reference data of 1980 and 1981).

Do laptop ao jogo interacional: sentidos circulantes no Fórum de discussão do Programa Conexão Professor (2008-2010)

Esta pesquisa analisa os sentidos circulantes nos textos publicados (postagens) por professores e Moderadora no Fórum de discussão online do Programa Conexão Professor, desenvolvido pela Secretaria de Estado de Educação do Rio de Janeiro (SEEDUC). Parte de dois modos de objetivação das tecnologias da informação e da comunicação (TIC): uma, em que as TIC são apontadas como revolução tecnológica no contexto da sociedade da informação; e outra centrada na recontextualização educacional das TIC. Situa a distribuição de laptops para os professores da rede estadual de ensino no contexto do Programa citado, buscando apreender ambos nos termos do ciclo contínuo de políticas, de Richard Bowe e Stephen Ball. Trata o Fórum de discussão online como locus privilegiado e os textos nele produzidos, entre dezembro de 2008 e julho de 2010, como corpus. Assume como alternativa teórico-metodológica a Análise Crítica do Discurso (ACD), formulada por Norman Fairclough, elegendo como pontos de entrada: o controle interacional, as escolhas lexicais e a modalidade. Investiga, a partir das pistas discursivas detectadas nas postagens, as relações estabelecidas entre a proposta de incorporação das TIC e a totalidade do trabalho docente. Conclui que os sentidos postos em circulação contestam a centralidade atribuída às TIC, apontando a substituição tecnológica como tendência política atual, expressa pelo deslocamento da ênfase na discussão para o fornecimento de materiais prontos, denominados objetos de aprendizagem

Age and growth of spiny dogfish (Squalus acanthias) in the Gulf of Alaska: analysis of alternative growth models

Ten growth models were fitted to age and growth data for spiny dogfish (Squalus acanthias) in the Gulf of Alaska. Previous studies of spiny dogfish growth have all fitted the t0 formulation of the von Bertalanffy model without examination of alternative models. Among the alternatives, we present a new two-phase von Bertalanffy growth model formulation with a logistically scaled k parameter and which estimates L0. A total of 1602 dogfish were aged from opportunistic collections with longline, rod and reel, set net, and trawling gear in the eastern and central Gulf of Alaska between 2004 and 2007. Ages were estimated from the median band count of three independent readings of the second dorsal spine plus the estimated number of worn bands for worn spines. Owing to a lack of small dogfish in the samples, lengths at age of small individuals were back-calculated from a subsample of 153 dogfish with unworn spines. The von Bertalanffy, two-parameter von Bertalanffy, two-phase von Bertalanffy, Gompertz, two-parameter Gompertz, and logistic models were fitted to length-at-age data for each sex separately, both with and without back-calculated lengths at age. The two-phase von Bertalanffy growth model produced the statistically best fit for both sexes of Gulf of Alaska spiny dogfish, resulting in L∞ = 87.2 and 102.5 cm and k= 0.106 and 0.058 for males and females, respectively.

Eurobalise-Train communication modelling to assess interferences in railway control signalling systems

The evolution of the railway sector depends, to a great extent, on the deployment of advanced railway signalling systems. These signalling systems are based on communication architectures that must cope with complex electromagnetical environments. This paper is outlined in the context of developing the necessary tools to allow the quick deployment of these signalling systems by contributing to an easier analysis of their behaviour under the effect of electromagnetical interferences. Specifically, this paper presents the modelling of the Eurobalise-train communication flow in a general purpose simulation tool. It is critical to guarantee this communication link since any lack of communication may lead to a stop of the train and availability problems. In order to model precisely this communication link we used real measurements done in a laboratory equipped with elements defined in the suitable subsets. Through the simulation study carried out, we obtained performance indicators of the physical layer such as the received power, SNR and BER. The modelling presented in this paper is a required step to be able to provide quality of service indicators related to perturbed scenarios.

A survey of ichthyofauna of Lake Kanyaboli and other small waterbodies in Kenya: alternative refugia for endangered fish species

In 1988, the World Conservation Union (WCU) Red Book of Endangered Species listed hundreds of endemic fishes of Lake Victoria under a single heading - "ENDANGERED". Most of the endemic native food fishes are either endangered or extinct. However, a survey of the fauna of Lake Kanyaboli, revealed that a few remaining samples of these native fishes are actually thriving. These include several unidentified Haplochromis spp., Oreochromis esculentus and Oreochromis variabilis. As a result, a stock rehabilitation and management strategy has been designed to use Lake Kanyaboli and other small waterbodies as conservation 'Refugia' for endangered fish species of the larger Lake Victoria.