Browsing by Issue Date, starting with "2018-02-15"
Now showing 1 - 5 of 5
Results Per Page
Sort Options
- Volcano-tectonic evolution of a linear volcanic ridge (Pico-Faial Ridge, Azores Triple Junction) assessed by paleomagnetic studiesPublication . Silva, Pedro; Henry, Bernard; Marques, Fernando Ornelas; Hildenbrand, Anthony; Lopes, Ana; Madureira, Pedro Miguel; Madeira, JFA; Nunes, João C.; Roxerová, ZuzanaThe morphology of volcanic oceanic islands results from the interplay between constructive and destructive processes, and tectonics. In this study, the analysis of the paleomagnetic directions obtained on well-dated volcanic rocks is used as a tool to assess tilting related to tectonics and large-scale volcano instability along the Pico-Faial linear volcanic ridge (Azores Triple Junction, Central-North Atlantic). For this purpose, 530 specimens from 46 lava flows and one dyke from Pico and Faial islands were submitted to thermal and alternating magnetic fields demagnetizations. Detailed rock magnetic analyses, including thermomagnetic analyses and classical high magnetic field experiments revealed titanomagnetites with different Ti-content as the primary magnetic carrier, capable of recording stable remanent magnetizations. In both islands, the paleomagnetic analysis yields a Characteristic Remanent Magnetization, which presents island mean direction with normal and reversed polarities in agreement with the islands location and the age of the studied lava flows, indicating a primary thermo-remanent magnetization. Field observations and paleomagnetic data show that lava flows were emplaced on pre-existing slopes and were later affected by significant tilting. In Faial Island, magmatic inflation and normal faults making up an island-scale graben, can be responsible for the tilting. In Pico Island, inflation related to magma intrusion during flow emplacement can be at the origin of the inferred tilting, whereas gradual downward movement of the SE flank by slumping processes appears mostly translational.
- Fast phylogenetic inference from typing dataPublication . Carrico, Joao; Crochemore, Maxime; Francisco, Alexandre; Pissis, Solon; Gonçalves, Bruno RibeiroBackground: Microbial typing methods are commonly used to study the relatedness of bacterial strains. Sequencebased typing methods are a gold standard for epidemiological surveillance due to the inherent portability of sequence and allelic profile data, fast analysis times and their capacity to create common nomenclatures for strains or clones. This led to development of several novel methods and several databases being made available for many microbial species. With the mainstream use of High Throughput Sequencing, the amount of data being accumulated in these databases is huge, storing thousands of different profiles. On the other hand, computing genetic evolutionary distances among a set of typing profiles or taxa dominates the running time of many phylogenetic inference methods. It is important also to note that most of genetic evolution distance definitions rely, even if indirectly, on computing the pairwise Hamming distance among sequences or profiles. Results: We propose here an average-case linear-time algorithm to compute pairwise Hamming distances among a set of taxa under a given Hamming distance threshold. This article includes both a theoretical analysis and extensive experimental results concerning the proposed algorithm. We further show how this algorithm can be successfully integrated into a well known phylogenetic inference method, and how it can be used to speedup querying local phylogenetic patterns over large typing databases.
- Retomar a visualização: resume viewingPublication . Freitas, Rodolfo Silva de; Antunes, DavidUm processo realizado através de descrições políticas do “self”, recorrendo inevitavelmente a experiências pessoais, que não têm necessariamente de contar uma história. Tento assim criar um estudo artístico, recorrendo aos escritores, filósofos e dramaturgos que parecem encaixar no universo por mim construído e trabalho na criação de um objeto de performance e videográfico documental (Resume Viewing), que pretende desconstruir ideias e conceitos relacionados com padrões ou estigmas sobre a vivência humana como animal político, expressão de Aristóteles.
- Fast phylogenetic inference from typing dataPublication . Carrico, Joao; Crochemore, Maxime; Francisco, Alexandre; Pissis, Solon; Ribeiro-Gonçalves, Bruno; Vaz, CátiaBackground: Microbial typing methods are commonly used to study the relatedness of bacterial strains. Sequence based typing methods are a gold standard for epidemiological surveillance due to the inherent portability of sequence and allelic profle data, fast analysis times and their capacity to create common nomenclatures for strains or clones. This led to development of several novel methods and several databases being made available for many microbial species. With the mainstream use of High Throughput Sequencing, the amount of data being accumulated in these databases is huge, storing thousands of diferent profles. On the other hand, computing genetic evolution ary distances among a set of typing profles or taxa dominates the running time of many phylogenetic inference methods. It is important also to note that most of genetic evolution distance defnitions rely, even if indirectly, on computing the pairwise Hamming distance among sequences or profles. Results: We propose here an average-case linear-time algorithm to compute pairwise Hamming distances among a set of taxa under a given Hamming distance threshold. This article includes both a theoretical analysis and extensive experimental results concerning the proposed algorithm. We further show how this algorithm can be successfully integrated into a well known phylogenetic inference method, and how it can be used to speedup querying local phylogenetic patterns over large typing databases.
- Modeling MARX Generators for maximum pulse repetition rate estimationPublication . Rocha, Luis Lamy; Canacsinh, Hiren; Silva, J. Fernando; Redondo, Luis; Luciano, T.This paper presents a generalized n stage dynamic model for unipolar semiconductor based Marx generators. The model is tailored for the capacitors charging mode to enable the estimation of the maximum pulse repetition rate of the n stage generator. T The maximum pulse repetition rate for the n stage Marx generator can be calculated as a function of the number n of stages, and of the voltage decay allowed in each capacitor (usually less than 10%). Furthermore, given a needed pulse repetition rate the model can estimate the optimum number of stages (n) so that the working voltage of each stage can be selected. Simulation results for a ten-stage (n=10) positive output Marx generators are presented and discussed.