Optimization of epidemic multicast protocols

Dissertação de mestrado integrado em Engenharia InformáticaEpidemic multicast protocols, also known as gossip protocols, offer fault tolerance and good performance at large scale. Therefore, these are used in peer-to-peer (P2P) systems on the Internet and in NoSQL data management systems. Research has shown there are multiple variants of these protocols which are most efficient in certain environments and applications. Some protocols, such as Plumtree, even allow the application to configure to obtain different performance trade-offs. This dissertation aims at taking advantage of Machine Learning (ML) to configure these protocols, developing a solution that adapts in runtime to network conditions and evaluate it experimentally. The results obtained by using ML models to control the transmission strategy used when forwarding messages show that it is possible to achieve a better trade-off between bandwidth used and the time to reach the entire network. Moreover, this does not endanger the characteristics of epidemic multicast protocols, maintaining their reliability while becoming even more scalable.Os protocolos de difusão epidémica, também conhecidos como gossiping, oferecem tolerância a faltas e bom desempenho em grande escala. São por isso usados, por exemplo, em sistemas entre-pares (P2P) na Internet e em sistemas de gestão de dados NoSQL. A investigação feita mostrou que existem múltiplas variantes destes protocolos, adaptadas a diferentes ambientes e aplicações. Alguns protocolos concretos, como o Plumtree, permitem até que a aplicação faça uma configuração das suas características, de forma a obter diferentes compromissos de desempenho. Nesta dissertação apresenta-se uma abordagem que tira partido de tecnologias de aprendizagem automática para fazer a configuração destes protocolos, desenvolvendo uma solução capaz de se adaptar em runtime tendo em conta o estado atual da rede e posteriormente é feita uma avaliação da solução experimentalmente. Os resultados obtidos com os modelos que controlam a estratégia de transmissão na distribuição de mensagens demonstram ser possível alcançar um melhor compromisso entre o número de mensagens enviadas e o tempo necessário para as distribuir. Além disso, não compromete as características dos protocolos de difusão epidémica, mantendo a sua confiabilidade e tornando-se ainda mais escaláveis

Mestrado em Biofísica e Bionanossistemas: comemoração da 10ª edição

[Excerto] Preâmbulo O Mestrado em Biofísica e Bionanossistemas (MBB) comemora, em 2020, 10 anos de existência. Este curso tem por objetivo formar profissionais com competências avançadas nas áreas interdisciplinares da Física e da Biologia, destacando-se no domínio da nanotecnologia

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Growing knowledge: an overview of Seed Plant diversity in Brazil

Abstract An updated inventory of Brazilian seed plants is presented and offers important insights into the country's biodiversity. This work started in 2010, with the publication of the Plants and Fungi Catalogue, and has been updated since by more than 430 specialists working online. Brazil is home to 32,086 native Angiosperms and 23 native Gymnosperms, showing an increase of 3% in its species richness in relation to 2010. The Amazon Rainforest is the richest Brazilian biome for Gymnosperms, while the Atlantic Rainforest is the richest one for Angiosperms. There was a considerable increment in the number of species and endemism rates for biomes, except for the Amazon that showed a decrease of 2.5% of recorded endemics. However, well over half of Brazillian seed plant species (57.4%) is endemic to this territory. The proportion of life-forms varies among different biomes: trees are more expressive in the Amazon and Atlantic Rainforest biomes while herbs predominate in the Pampa, and lianas are more expressive in the Amazon, Atlantic Rainforest, and Pantanal. This compilation serves not only to quantify Brazilian biodiversity, but also to highlight areas where there information is lacking and to provide a framework for the challenge faced in conserving Brazil's unique and diverse flora