Membranes for Direct Methanol Fuel Cell Applications: analysis based on characterization, experimentation and modeling

A critical analysis is performed about fundamental aspects regarding the direct methanol fuel cell (DMFC) technology, focusing mainly on the proton exchange membrane (PEM). First, the basic DMFC operation principles, thermodynamic background and polarization characteristics are presented with a description of each of the components that comprise the membrane electrode assembly (MEA) and of the DMFC testsystem usually used for DMFC research. Next, the paper focuses particularly on the PEM development chain, performing an overview of the research progress regarding this DMFC component. Specific efforts are devoted to research aspects related with the membrane preparation, characterization, DMFC tests and modeling. Apart from this, recent achievements at our research groups regarding the PEM development for DMFC applications are emphasized

Electrochemical synthesis of diaminodicarboxylic acid derivatives

Diaminoadipic acid derivatives were synthesized in good yields by electrolysis of N,N-diacyidehydroalanines. Cyclic voltammetry measurements on the precursors are presented and interpreted as supporting formation of a nucleophilic intermediate generated by electrochemical reduction. (C) 2003 Elsevier Science Ltd. All rights reserved.- Fundação para a Ciência e a Tecnologia (project no. POCTI/1999/QUI/32689)

Synthesis of non-proteinogenic amino acids from N-(4-toluenesulfonyl)dehydroamino acid derivatives

By treating N-(4-toluenesulfonyl)-N-(tert-butyloxycarbonyl)-dehydroamino acid derivatives with different reactants under different conditions, a variety of new amino acids are obtained, viz. (i) alpha-alcoxy-alpha-amino acids, (ii) alpha,alpha-diamino acids and (iii) novel beta-substituted dehydroamino acids. (C) 2002 Elsevier Science Ltd. All rights reserved.Fundação para a Ciência e a Tecnologia for financial support (project no. POCTI/ 1999/QUI/32689)

Synthesis of 2,3,5-substituted pyrrole derivatives

2,3,5-Substituted pyrrole derivatives are prepared by treatment of 2,3-dihydrofuran derivatives with trifluoroacetic acid. These in turn are obtained by Michael addition of carbon nucleophiles of the beta-dicarbonyl type to N-(4-toluenesulfonyl)-N-(tert-butyloxycarbonyl)-dehydroalanine methyl ester.- Fundação para a Ciência e a Tecnologia(POCTI/1999/QUI/32689

Efficient synthesis of dehydroamino acid derivatives

By using a DMAP catalysed reaction of P-hydroxyamino acid derivatives with tert-butylpyrocarbonate, the corresponding dehydroamino acid derivatives were obtained in high yields.- (undefined

Materiais de construção e materiais líticos nas práticas funerárias neolíticas da serra da Boa Viagem (Centro-Oeste de Portugal). O caso do monumento megalítico do Cabeço dos Moinhos, Figueira da Foz

Este trabalho contribui para o conhecimento do Neolítico do Centro-Oeste português. O caso de estudo foi o monumento megalítico do Cabeço dos Moinhos, edificado na serra da Boa Viajem, no que é hoje a freguesia da Brenha, concelho da Figueira da Foz. Para além de ser óbvio que esta região se encontrava, durante o Neolítico, no limiar de diferentes mundos culturais, o meridional e o setentrional, a partir das matérias usadas na construção do monumento e das matérias usadas no fabrico de oferendas líticas e de objetos de adorno, teceram-se algumas considerações relacionadas com as práticas funerárias, os modos de vida e de vivenciar o mundo por parte das comunidades neolíticas que aqui ergueram estes monumentos. Em relação às oferendas líticas notou-se a ausência de traços de uso o que indicia que foram fabricadas apenas para ritos funerários. Além do simbolismo intrínseco às formas, as diferentes matérias em que foram construídos (locais, regionais e inter-regionais) indiciam a importância da interligação física e simbólica das comunidades locais com lugares próximos e remotos, o que não será alheio a um modo de vida com grande abertura ao mundo exterior e, talvez, pouco sedentarizado . O mesmo se poderá interpretar em termos arquitetónicos pois, se a construção sobre um afloramento calcário e em local culminante poderá revelar assimilação das propriedades inerentes ao local e à matéria aí existente, a reunião de matérias de diferentes proveniências na câmara/corredor implicará uma interligação física e mental entre os diferentes lugares vivenciados pelos seus construtores, ou seja, entre lugares de habitat, de subsistência e de veneração dos espíritos dos antepassados.This paper contributes to the understanding of the Neolithic burial practices in Western Central Portugal. It relies on the reviewing of Santos Rocha texts, which describes research carried out in the megalithic monument of Cabeço dos Moinhos (Brenha, Figueira da Foz), fieldwork and the study of bone remains and “offerings” that were found in the monument. Cabeço dos Moinhos tomb was built on a limestone outcrop located in a hill placed on the ridgeline of Serra da Boa Viagem. From this hill there is a wide visibility to the sandy coastal plain (to the north) and to the Baixo Mondego area (to the south). Under a mound of "yellowish soil without mixture" a polygonal chamber with corridor oriented east was built. The standing stones were made of greyish white limestone (local) and of whitish, greyish, yellowish and reddish sandstone. The last two are sourced from slopes located more than 250m south of the tomb. Santos Rocha (1949: 14) found some "skeletons lying in gravel beds" and rare burnt bones. The dead were buried together with pottery, lithic and bone objects. Some of these indicate a reutilization of the monument during the Chalcolithic. The absence of use-wear in the majority of the lithics suggests that they were produced only for the burial practices. In addition to the symbolism intrinsic to morphologies, the use of different “raw” materials suggests the importance of the reunion of their own properties at the time of the burial, setting a symbolic and physical interconnection between local communities and near and remote places. The same reasoning can be applied to the architecture of the monument: if its construction on a limestone outcrop which is a culminating spot suggests the assimilation of the properties associated to the place and to the matter that exists there, the presence of “raw” materials from different sources among the standing stones of the chamber and the corridor imply a mental and physical interconnection between different places experienced by the builders. The visualized landscape must also have been significant to the people who built and attended the Cabeço dos Moinhos megalithic monument.info:eu-repo/semantics/publishedVersio

Mechanical behavior of hot-mix asphalt made with recycled concrete aggregates from construction and demolition waste: a design of experiments approach

[Abstract:] The present work is a re-evaluation of previous research on the durability of hot-mix asphalt made with recycled concrete aggregates from construction and demolition waste (CDW) with a different approach. Response surface methodology (RSM) was used to conduct this study. The kind of natural aggregates (schist and calcite-dolomite), the recycled concrete aggregates percentage (0%, 20%, 40% and 60%) and the water saturation (0% and 100%) were the pertinent factors for this methodology. Indirect tensile stress (ITS) was determined in mixtures fabricated with 0%, 20%, 40% and 60% recycled concrete aggregates. According to the results, the ITS of the bituminous mixtures increases as the percentage of recycled concrete aggregate increases. This behavior is more significant when calcite-dolomite is used as a natural aggregate. Water saturation has the same influence in both natural aggregates. The indirect tensile strength ratio (ITSR) was calculated to evaluate the stripping potential. According to the Spanish specifications, the results suggest that the percentage of CDW that can be used for hot mixes is 17% when schist is used as natural aggregate and 14% for calcite-dolomite

Evaluation of the Resilient Modulus of Hot-Mix Asphalt Made With Recycled Concrete Aggregates From Construction and Demolition Waste

[Abstract] This paper reports the influence of the percentage of recycled aggregate (RCA) from construction and demolition waste (C&DW) together with the percentage of binder (L), curing time (t) and temperature (T) of the samples on the stiffness of a hot asphalt mixture. The study was carried out using the response surface methodology (RSM). The resilient modulus was chosen to estimate the stiffness of the mixture. The percentages of RCA studied were 0% (control), 5%, 10%, 20% and 30%, whilst 3.5%, 4% and 4.5% were those chosen for the binder content. Before compacting the samples, they were left into the oven to cure. Curing time, or pretreatment time, were set at 0 (control), 2 and 4 h. The samples were subjected to temperatures of 0, 10 and 20 °C. The natural aggregate is of the hornfels type. All the specimens studied showed high stiffness at low temperatures. According to this research, temperature proved to be the most influential factor on the decrease in the resilient modulus and, conversely, the percentage of recycled aggregate is not a significant factor in the range of values studied.Portugal. Fundação para a Ciência e Tecnologia; UIDB/04730/202