Ionic Liquids and Cellulose: Dissolution, Chemical Modification and Preparation of New Cellulosic Materials

Due to its abundance and a wide range of beneficial physical and chemical properties, cellulose has become very popular in order to produce materials for various applications. This review summarizes the recent advances in the development of new cellulose materials and technologies using ionic liquids. Dissolution of cellulose in ionic liquids has been used to develop new processing technologies, cellulose functionalization methods and new cellulose materials including blends, composites, fibers and ion gels.

Bismuth-activated luminescent materials for broadband optical amplifier in WDM system

New broadband near infrared luminescence covering the whole work windows (1260-1625 nm) of the current wavelength division multiplexing (WDM) system was found from bismuth-activated M2O-Al2O3-SiO2 (M = Li, Na) and Li2O-Ta2O5-SiO2 glasses at room temperature in the case of 808 nm-laser excitation. But the near infrared luminescence mechanism of the bismuth-activated glasses is not well understood up to now. The figure-of-merits of bandwidth and gain of the glasses are better than those of Er3+-doped silicate glasses and Ti3+ doped sapphire, implying they are the promising gain-medium candidates for the broadband amplifiers and the widely tunable laser sources. (c) 2007 Elsevier B.V. All rights reserved.

SupraMOFs: Supramolecular porous materials assembled from metal-nucleobase discrete entities

289 p.

"A lição da mocidade reta": um olhar sobre biografias de Getúlio Vargas para crianças e jovens (1937-1945)

O presente trabalho destina-se à reflexão acerca de algumas das dimensões do projeto político e educacional posto em prática no período do Estado Novo (1937-1945), buscando focalizar estratégias encaminhadas no sentido da formação da população infanto-juvenil, com base em valores morais e sociais afinados com a ideologia do regime. No âmbito das estratégias voltadas para fortalecimento e legitimação do regime, que procurava construir uma identificação com a nação, houve a preocupação com a produção de uma imagem idealizada do próprio Estado Novo, da figura de Vargas diante do povo e de sua relação com este, em especial, com os trabalhadores e a juventude. Para isso, o governo lançou mão de estratégias diversas para popularização da figura do presidente diante dos jovens e produziu todo um conjunto de representações acerca de valores como família, educação, trabalho e nação. Tais estratégias compreenderam uma vasta produção de materiais impressos e, entre estes,biografias de Getúlio Vargas, voltadas para o público infanto-juvenil. Assim, a intenção deste estudo é refletir sobre a produção destes impressos no âmbito do projeto político e educacional do regime, buscando apreender de que forma estas publicações, que têm como pano de fundo a trajetória de vida do presidente, forneceram aos jovens modelos de comportamento e parâmetros de conduta valorizados socialmente e, em que medida, se configuraram, elas próprias, produtoras daquela realidade.

Nano-modification inside transparent materials by femtosecond laser single beam

Periodic nanostructures along the polarization direction of light are observed inside silica glasses and tellurium dioxide single crystal after irradiation by a focused single femtosecond laser beam. Backscattering electron images of the irradiated spot inside silica glass reveal a periodic structure of stripe-like regions of similar to 20 nm width with a low oxygen concentration. In the case of the tellurium dioxide single crystal, secondary electron images within the focal spot show the formation of a periodic structure of voids with 30 nm width. Oxygen defects in a silica glass and voids in a tellurium dioxide single crystal are aligned perpendicular to the laser polarization direction. These are the smallest nanostructures below the diffraction limit of light, which are formed inside transparent materials. The phenomenon is interpreted in terms of interference between the incident light field and the electric field of electron plasma wave generated in the bulk of material.

Three-dimensional micro- and nano-fabrication in transparent materials by femtosecond laser

Femtosecond pulsed lasers have been widely used for materials microprocessing. Due to their ultrashort pulse width and ultrahigh light intensity, the process is generally characterized by the nonthermal diffusion process. We observed various induced microstructures such as refractive-index-changed structures, color center defects, microvoids and microcracks in transparent materials (e.g., glasses after the femtosecond laser irradiation), and discussed the possible applications of the microstructures in the fabrication of various micro optical devices [e.g., optical waveguides, microgratings, microlenses, fiber attenuators, and three-dimensional (3D) optical memory]. In this paper, we review our recent research developments on single femtosecond-laser-induced nanostructures. We introduce the space-selective valence state manipulation of active ions, precipitation and control of metal nanoparticles and light polarization-dependent permanent nanostructures, and discuss the mechanisms and possible applications of the observed phenomena.