Browsing by Issue Date, starting with "2005-11"
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- Linear and crosslinked copolymers of p-tert-butylcalix[4]arene derivatives and styrene: new synthetic approaches to polymer-bound calix[4]arenesPublication . Mendes, Ana R.; Gregório, Carla C.; Barata, Patrícia; Costa, Alexandra I.; Prata, José V.As an extension of our previous studies concerning the free radical copolymerisation of 25,26,27-tripropoxy-28-(4-vinyl-benzyloxy)-p-tert-butylcalix[4]arene (3) with styrylic monomers, we report herein on the synthesis and characterisation of new terpolymers derived from 3, styrene and divinylbenzene, having nominal crosslinking degrees ranging from 4% to 40% wt. The terpolymers exhibited good thermal stabilities (DSC) and were prepared in good yields. Depending on the reaction conditions (dilution degree and aqueous phase to porogen ratio), materials with identical nominal crosslinking but otherwise differentiated morphologies and swelling abilities were obtained. In a related study, the radical polymerisation of styrene was carried out in the presence of a novel calix[4]arene derivative 4, bearing two distal benzyl–vinyl groups in the lower rim. It is shown that, albeit the presence of two phenolic groups within the calixarene moiety which could have functioned as inhibitors of the free radical polymerisation, the macrocycle was able to take part in the copolymerisation reaction, yielding new soluble and crosslinked polymers. In both cases, no pendant vinyl groups were found in the polymeric materials. The probable mechanisms underlying their formation are discussed.
- Estimação do subespaço de sinal em dados hiperespectraisPublication . Nascimento, Jose; Bioucas-Dias, José M.A redução de dimensionalidade é uma tarefa crucial no processamento e análise de dados hiperespectrais. Esta comunicação propõe um método de estimação do subespaço de sinal baseado no erro quadrático médio. O método consiste em primeiro estimar as matrizes de correlação do sinal e do ruído e em segundo seleccionar o conjunto de vectores próprios que melhor representa o subespaço de sinal. O eficiência deste método é ilustrada em imagens hiperespectrais sintéticas e reais.
- Structural characterization and immunogenicity in wildtype and immune tolerant mice of degraded recombinant human interferon alpha2bPublication . Hermeling, Suzanne; Caetano, Liliana Aranha; Damen, J. Mirjam A.; Slijper, Monique; Schellekens, Huub; Crommelin, Daan J. A.; Jiskoot, WimPurpose - To study the influence of protein structure on the immunogenicity in wildtype and immune tolerant mice of well-characterized degradation products of recombinant human interferon alpha2b (rhIFNα2b). Methods - RhIFNα2b was degraded by metal catalyzed oxidation (M), crosslinking with glutaraldehyde (G), oxidation with hydrogen peroxide (H) and incubation in a boiling water bath (B). The products were characterized with UV absorption, circular dichroism and fluorescence spectroscopy, gel permeation chromatography, reversed-phase HPLC, SDS-PAGE, Western blotting and mass spectrometry. The immunogenicity of the products was evaluated in wildtype mice and in transgenic mice immune tolerant for hIFNα2. Serum antibodies were detected by ELISA or surface plasmon resonance. Results - M-rhIFNα2b contained covalently aggregated rhIFNα2b with three methionines partly oxidized to methionine sulfoxides. G-rhIFNα2b contained covalent aggregates and did not show changes in secondary structure. H-rhIFNα2b was only chemically changed with four partly oxidized methionines. B-rhIFNα2b was largely unfolded and heavily aggregated. Native (N) rhIFNα2b was immunogenic in the wildtype mice but not in the transgenic mice, showing that the latter were immune tolerant for rhIFNα2b. The antirhIFNα2b antibody levels in the wildtype mice depended on the degradation product: M-rhIFNα2b > H-rhIFNα2b ~ N-rhIFNα2b >> B-rhIFNα2b; G-rhIFNα2b did not induce anti-rhIFNα2b antibodies. In the transgenic mice, only M-rhIFNα2b could break the immune tolerance. Conclusions - RhIFNα2b immunogenicity is related to its structural integrity. Moreover, the immunogenicity of aggregated rhIFNα2b depends on the structure and orientation of the constituent protein molecules and/or on the aggregate size.
- Corporate values in portuguese organizations: empirical cases and anthropological analysisPublication . Cavaleiro Rodrigues, JoséComunicação oral dedicada à análise da relação entre visão e valores das culturas organizacionais em empresas com forte presença na força de trabalho contratos precários.
- Tracking with Bayesian networks: extension to arbitrary topologiesPublication . Jorge, Pedro; Abrantes, Arnaldo; Marques, Jorge S.It was recently proposed an object tracking method, which is able to deal with object occlusions and group tracking, using Bayesian networks. The Bayesian network (BN) tracker has shown promising results in difficult situations but its architecture is limited to a maximum of 2 parents/2 children per node, in order to avoid the combinatorial explosion and difficult network generation procedures from the video signal. This paper addresses the major limitation of the BN tracker and presents a method to generalize the tracker to cope with arbitrary topologies, allowing the tracker to operate in more complex scenes.
- Convective patterns under the Indo-Atlantic << box >>Publication . Davaille, A.; Stutzmann, E.; Silveira, Graça; Besse, J.; Courtillot, VUsing fluid mechanics, we reinterpret the mantle images obtained from global and regional tomography together with geochemical, geological and paleomagnetic observations, and attempt to unravel the pattern of convection in the Indo-Atlantic "box" and its temporal evolution over the last 260 Myr. The << box >> presently contains a) a broad slow seismic anomaly at the CMB which has a shape similar to Pangea 250 Myr ago, and which divides into several branches higher in the lower mantle, b) a "superswell, centered on the western edge of South Africa, c) at least 6 "primary hotspots" with long tracks related to traps, and d) numerous smaller hotspots. In the last 260 Myr, this mantle box has undergone 10 trap events, 7 of them related to continental breakup. Several of these past events are spatially correlated with present-day seismic anomalies and/or upwellings. Laboratory experiments show that superswells, long-lived hotspot tracks and traps may represent three evolutionary stages of the same phenomenon, i.e. episodic destabilization of a hot, chemically heterogeneous thermal boundary layer, close to the bottom of the mantle. When scaled to the Earth's mantle, its recurrence time is on the order of 100-200 Myr. At any given time, the Indo-Atlantic box should contain 3 to 9 of these instabilities at different stages of their development, in agreement with observations. The return flow of the downwelling slabs, although confined to two main << boxes >> (Indo-Atlantic and Pacific) by subduction zone geometry, may therefore not be passive, but rather take the form of active thermochemical instabilities. (c) 2005 Elsevier B.V. All rights reserved.
- Mass media, mundialização da informação e erosão da cultura. A importância de Harold Innis para um conceito de comunicação como culturaPublication . Subtil, Filipa Mónica de Brito GonçalvesQuando aparentemente existem condições de liberdade e meios técnicos de expansão de qualidades determinantes para a existência de uma sociedade boa, tais como a comunicação e a cultura, são cada vez mais presentes as vozes que questionam o papel dos mass media na formação de um espaço público orientado pelo que Max Weber designou de “racionalidade substantiva” ou ética. O confronto de razões e argumentos está, para muitos, gangrenado por um fluxo de informação que estimula a iconomania, a supremacia do visível sobre o inteligível, a deterioração do pensamento abstracto, a redução das possibilidades abertas pelo mundo moderno aos seus elementos estratégicos. Sem pôr em causa as consequências negativas dos desenvolvimentos actuais da informação, explorar-se-ão formas de pensamento da sociedade moderna que não se conformam nem com a redução da comunicação a uma mera transmissão de informação mercadorizada, nem se limitam a assinalar os efeitos perversos do progresso da razão e da tecnologia.