Safer by design

Abstract not available

A new technique to automatically quantify microstructures of fine grained carbonate mylonites: two-step etching combined with SEM imaging and image analysis

A two-step etching technique for fine-grained calcite mylonites using 0.37% hydrochloric and 0.1% acetic acid produces a topographic relief which reflects the grain boundary geometry. With this technique, calcite grain boundaries become more intensely dissolved than their grain interiors but second phase minerals like dolomite, quartz, feldspars, apatite, hematite and pyrite are not affected by the acid and therefore form topographic peaks. Based on digital backscatter electron images and element distribution maps acquired on a scanning electron microscope, the geometry of calcite and the second phase minerals can be automatically quantified using image analysis software. For research on fine-grained carbonate rocks (e.g. dolomite calcite mixtures), this low-cost approach is an attractive alternative to the generation of manual grain boundary maps based on photographs from ultra-thin sections or orientation contrast images.

INFLUENCE OF A NATIVE INSECTARY PLANT, CHAMAECRISTA FASCICULATA (MICHX.) ON ORGANIC FIELD CORN AND ARTHROPOD COMMUNITIES

Increasing plant diversity in conventionally monoculture agrosystems has been promoted as a method to enhance beneficial arthropod density and efficacy, suppress herbivory and provide a range of ecosystem services. I investigated the pest suppressive potential and economic impact of plant diversification in organic field corn. The experiment consisted of two treatments, corn grown in monoculture (C) and bordered by strips of partridge pea (PP). Pest and natural enemy populations, corn damage, yield, and profits were compared among treatments. Natural enemy and herbivore arthropod populations were affected by treatment and distance from plot border. Corn damage due to pests was also affected by treatment and location, but did not significantly affect yield. Yield in monoculture plots was generally greater than in PP but did not result in greater profit. Pest and natural enemy arthropod abundances were elevated in partridge pea treatment borders, but these populations did not consistently diffuse into plot interiors. The potential causes and implications of findings are discussed.

Outras Lisboas

Dissertação para obtenção do grau de Mestre em Arquitetura com Especialização em Urbanismo, apresentada na Universidade de Lisboa - Faculdade de Arquitetura.

City & Spectacle: A Vision of Lisbon Before the 1755 Great Earthquake

City & Spectacle: a vision of pre-earthquake Lisbon consists of a virtual recrea on of the city of Lis- bon on the eve of the great earthquake of 1 November 1755, giving shape to a laboratory model for research into the city’s history. As its star ng point the project has the virtual recrea on of one the most emblema c of spaces from 18th century Lisbon, the Royal Opera House, which disappeared during the 1755 earthquake. The recrea on of the Opera House was developed in the scope of the commemora- ons of the 250th anniversary of the 1755 catastrophe as an a empt to restore this space of the highest ar s c quality to memory and to return it to the inventory of the Portuguese heritage of architectural history.1 Using Second Life® technology it was possible to put forward a model of both the struc- ture and interiors of the Opera House as well as its anima on combined with a small piece of the opera presented at the inaugura on of the building in April 1755. The public presenta on of this virtual model at the conference 1755: Catástrofe, memória e arte (1755: catastrophe, memory and art), which took place at the Centro de Estudos Compara- stas, Universidade de Lisboa, led to a debate on the study and cri cal analysis of documentary sources and their selec on and applica on on recrea ons using virtual world technology. It also emphasized the need to extend the research on pre-earthquake Lisbon.

Investigating stellar mixing processes through the study of the Red-Giant Branch bump

Extra mixing at the borders of convective zones in stellar interiors takes on an important role in the chemical evolution of stars and galaxies through the transport of chemical elements towards the stellar surface: knowing the overshooting mechanism can therefore lead to a better understanding of the observed chemical abundances in stellar photospheres. The comprehension of this phenomenon is quite uncertain and currently object of many studies. In particular, concerning low mass stars, in the past decades several works highlighted a discrepancy between the observed luminosity of the Red-Giant Branch bump and its prediction from simulations, which can be fixed including overshooting at the base of the convective envelope. This work, studying the Red-Giant Branch bump and using it as a diagnostic for extra mixing processes, tries to classify two different types of overshooting, instantaneous and diffusive, using both simulations from stellar models and Globular Clusters’ data. The aim is to understand which one of the two mixing processes is the most suitable in reproducing the observed stellar behaviour and, in case both of them provide reliable results, what are the conditions under which they produce the same effects on the Red-Giant Branch bump luminosity function and are consequently indistinguishable. Finally, possible dependences of overshooting efficiency on stellar parameters, such as chemical composition, are analysed.