Development of hybrid composite plate (HCP) for strengthening and repair of RC structures

Tese de Doutoramento em Engenharia Civil

Influência do fator visão do céu na propagação do ruído em zonas urbanas

Dissertação de mestrado integrado em Engenharia Civil

Programa com abordagem probabilística do sistema de avaliação de qualidade de taludes Slope Quality Index (SQI)

Dissertação de mestrado integrado em Engenharia Civil

Enzymatic treatments to improve mechanical properties and surface hydrophobicity of jute fiber membranes

Fiber membranes prepared from jute fragments can be valuable, low cost, and renewable. They have broad application prospects in packing bags, geotextiles, filters, and composite reinforcements. Traditionally, chemical adhesives have been used to improve the properties of jute fiber membranes. A series of new laccase, laccase/mediator systems, and multi-enzyme synergisms were attempted. After the laccase treatment of jute fragments, the mechanical properties and surface hydrophobicity of the produced fiber membranes increased because of the cross-coupling of lignins with ether bonds mediated by laccase. The optimum conditions were a buffer pH of 4.5 and an incubation temperature of 60 °C with 0.92 U/mL laccase for 3 h. Laccase/guaiacol and laccase/alkali lignin treatments resulted in remarkable increases in the mechanical properties; in contrast, the laccase/2,2-azino-bis-(3-ethylthiazoline-6-sulfonate) (ABTS) and laccase/2,6-dimethoxyphenol treatments led to a decrease. The laccase/ guaiacol system was favorable to the surface hydrophobicity of jute fiber membranes. However, the laccase/alkali lignin system had the opposite effect. Xylanase/laccase and cellulase/laccase combined treatments were able to enhance both the mechanical properties and the surface hydrophobicity of jute fiber membranes. Among these, cellulase/laccase treatment performed better; compared to mechanical properties, the surface hydrophobicity of the jute fiber membranes showed only a slight increase after the enzymatic multi-step processes.

Predicting SO2 pollution incidents by means of additive models with optimum variable selection

The aim of this paper is to predict time series of SO2 concentrations emitted by coal-fired power stations in order to estimate in advance emission episodes and analyze the influence of some meteorological variables in the prediction. An emission episode is said to occur when the series of bi-hourly means of SO2 is greater than a specific level. For coal-fired power stations it is essential to predict emission epi- sodes sufficiently in advance so appropriate preventive measures can be taken. We proposed a meth- odology to predict SO2 emission episodes based on using an additive model and an algorithm for variable selection. The methodology was applied to the estimation of SO2 emissions registered in sampling lo- cations near a coal-fired power station located in Northern Spain. The results obtained indicate a good performance of the model considering only two terms of the time series and that the inclusion of the meteorological variables in the model is not significant.

Comparative genomics reveals adaptations of a halotolerant thaumarchaeon in the interfaces of brine pools in the Red Sea

The bottom of the Red Sea harbors over 25 deep hypersaline anoxic basins that are geochemically distinct and characterized by vertical gradients of extreme physicochemical conditions. Because of strong changes in density, particulate and microbial debris get entrapped in the brine-seawater interface (BSI), resulting in increased dissolved organic carbon, reduced dissolved oxygen toward the brines and enhanced microbial activities in the BSI. These features coupled with the deep-sea prevalence of ammonia-oxidizing archaea (AOA) in the global ocean make the BSI a suitable environment for studying the osmotic adaptations and ecology of these important players in the marine nitrogen cycle. Using phylogenomic-based approaches, we show that the local archaeal community of five different BSI habitats (with up to 18.2% salinity) is composed mostly of a single, highly abundant Nitrosopumilus-like phylotype that is phylogenetically distinct from the bathypelagic thaumarchaea; ammonia-oxidizing bacteria were absent. The composite genome of this novel Nitrosopumilus-like subpopulation (RSA3) co-assembled from multiple single-cell amplified genomes (SAGs) from one such BSI habitat further revealed that it shares [sim]54% of its predicted genomic inventory with sequenced Nitrosopumilus species. RSA3 also carries several, albeit variable gene sets that further illuminate the phylogenetic diversity and metabolic plasticity of this genus. Specifically, it encodes for a putative proline-glutamate 'switch' with a potential role in osmotolerance and indirect impact on carbon and energy flows. Metagenomic fragment recruitment analyses against the composite RSA3 genome, Nitrosopumilus maritimus, and SAGs of mesopelagic thaumarchaea also reiterate the divergence of the BSI genotypes from other AOA.

Development of composite auxetic structures for civil engineering applications

Tese de Doutoramento em Engenharia Têxtil