Reliable Communication in a Dynamic Network in the Presence of Byzantine Faults

We consider the following problem: two nodes want to reliably communicate in a dynamic multihop network where some nodes have been compromised, and may have a totally arbitrary and unpredictable behavior. These nodes are called Byzantine. We consider the two cases where cryptography is available and not available. We prove the necessary and sufficient condition (that is, the weakest possible condition) to ensure reliable communication in this context. Our proof is constructive, as we provide Byzantine-resilient algorithms for reliable communication that are optimal with respect to our impossibility results. In a second part, we investigate the impact of our conditions in three case studies: participants interacting in a conference, robots moving on a grid and agents in the subway. Our simulations indicate a clear benefit of using our algorithms for reliable communication in those contexts

Influence of temperature, UV-light wavelength and intensity on polypropylene photothermal oxidation

A criterion based on the energy absorbed by photosensitive species was proposed to describe the contribution of UV-light to the initiation of the polypropylene photothermal oxidation whatever the light source. The calculation of this energy was performed using the widely accepted quantum theory. The criterion was then introduced in two different types of analytical models commonly used to describe the combined effects of UV light and temperature on induction time, namely: the reciprocity law and kinetic model. The limitations of both types of analytical models were then investigated: the latter, derived from a realistic mechanistic scheme, was found to be much more relevant than the former, which is presumably valid in a restricted range of light intensities, essentially due to its empirical origin

Variações morfométricas de Coprophanaeus saphirinus (Coleoptera: Scarabaeinae) em áreas da Mata Atlântica em diferentes estágios sucessionais

TCC(graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Biológicas. Biologia.Os besouros Scarabaeinae (Coleoptera: Scarabaeidae) têm sido sugeridos como indicadores da qualidade ambiental por apresentarem sensibilidade à degradação no hábitat e participarem de importantes serviços ambientais, ao enterrar dentro de túneis porções de fezes e carniças com as quais se alimentam. A maioria das espécies apresenta dimorfismo sexual. A biomassa incorporada nos indivíduos adultos está diretamente relacionada com a quantidade e qualidade do recurso alimentar disponível durante seu período larval. Evidências da diminuição da biomassa e do tamanho corporal se relacionam com tamanhos menores de estruturas secundárias (chifres) em machos. Neste trabalho, foram realizadas análises morfométricas de Coprophanaeus saphirinus (Sturm, 1826), para compreender a resposta da população frente à modificação ambiental de diferentes estágios sucessionais em três áreas da Mata Atlântica. Para tanto, foram comparados os parâmetros de abundância, razão sexual, variações fenotípicas dos machos, além da variação biométrica do comprimento do corpo e do peso seco e biomassa total dos indivíduos. Adultos de C. saphirinus provinham de quatro coletas realizadas com metodologia padronizada durante os anos de 2009 e 2010 em Unidades de Conservação do Estado de Santa Catarina. Foram analisados 159 espécimes e os resultados mostraram que tanto a abundância, a razão sexual e as variações fenotípicas dos machos nas três áreas não tiveram associação com o estágio sucessional. As variações biométricas do comprimento do corpo e do peso seco dos indivíduos mostraram que as fêmeas foram maiores somente em uma das áreas. Não houve diferença significativa no tamanho do corpo dos espécimes oriundos dos diferentes estágios sucessionais, bem como associação entre biomassa total de machos e de fêmeas. Os resultados mostram que os indivíduos que compõem a população de C. saphirinus (machos e fêmeas ou variações fenotípicas de machos) não apresentam comportamentos distintos em relação às áreas de Mata Atlântica em diferentes estágios sucessionais.Dung beetles (Coleoptera: Scarabaeidae) have been suggested as biological indicators of environmental quality by presenting sensitivity to changes in environment and participate in important environmental services, burying in tunnels portions of feces and carcasses in which they feed. Most of the species shows sexual dimorphism and the biomass incorporated in adults is directly related to the quantity and quality of food resources available during their larval period. Evidence of reduced biomass and smaller body sizes are related with smaller secondary structures (horns) in males. In this study, we performed morphometric analyzes of the species Coprophanaeus saphirinus (Sturm, 1826) to understand the response of the population to environmental changes in different successional stages in three areas of the Atlantic Forest. For this, we compared the parameters of abundance, sex ratio of male phenotypic variations, and biometric variation in body length, dry weight and total biomass of individuals. The specimens measured were from four samples collected with standardized methodology in 2009 and 2010 in Protected Areas of Santa Catarina state. We analyzed 159 specimens and the results showed that abundance, sex ratio and phenotypic variation in males in the three areas were not associated with the successional stage. The biometrical variations in body length and dry weight of the individuals showed that females were larger only in one area, but no significant difference were found in body size of specimens from different successional stages, just as there was no association between total biomass of males and females. These results show that individuals in the population of C. saphirinus (males and females or phenotypic variation for males) do not exhibit different behaviors in relation to the areas of Atlantic Forest in different successional stages

Computer-based assessment system for e-learning applied to programming education

Tese de mestrado integrado. Engenharia Informática e Computação. Faculdade de Engenharia. Universidade do Porto. 201

Dampening prey cycle overrides the impact of climate change on predator population dynamics : a long-term demographic study on tawny owls

Funded by ERA-Net BiodivERsA NERC. Grant Numbers: NE/E010660/1, NE/F021402/1, NE/G002045/1Peer reviewedPublisher PD

Do global warming-induced circulation pattern changes affect temperature and precipitation over Europe during summer?

Future climate change projections are not limited to a simple warming, but changes in precipitation and sea level pressure (SLP) are also projected. The SLP changes and the associated atmospheric circulation changes could directly mitigate or enhance potential projected changes in temperature and precipitation associated with rising temperatures. With the aim of analysing the projected circulation changes and their possible impacts on temperature and precipitation over Europe in summer [June–July–August (JJA)], we apply an automatic circulation type classification method, based on daily SLP, on general circulation model (GCM) outputs from the Coupled Model Intercomparison Project phase 5 (CMIP5) database over the historical period (1951–2005) and for climate under two future scenarios (2006–2100). We focus on summer as it is the season when changes in temperature and precipitation have the highest impact on human health and agriculture. Over the historical observed reference period (1960–1999), our results show that most of the GCMs have significant biases over Europe when compared to reanalysis data sets, both for simulating the observed circulation types and their frequencies, as well as for reproducing the intraclass means of the studied variables. The future projections suggest a decrease of circulation types favouring a low centred over the British Isles for the benefit of more anticyclonic conditions. These circulation changes mitigate the projected precipitation increase over north-western Europe in summer, but they do not significantly affect the projected temperature increase and the precipitation decrease over the Mediterranean region and eastern Europe. However, the circulation changes and the associated precipitation changes are tarnished by a high uncertainty among the GCM projections