Paulo Henrique Vieira Oliveira - Academia.edu (original) (raw)

Papers by Paulo Henrique Vieira Oliveira

Ecologia mediterranea, 2003

The diet of feral cats Felis catus on Santa Luzia, Cape Verde Islands, was studied. A total of 14... more The diet of feral cats Felis catus on Santa Luzia, Cape Verde Islands, was studied. A total of 147 prey items were identified during the analysis of 26 scat groups collected during the summer of 2010. House mouse Mus musculus was the most important prey, both in percentage of biomass and number of preys consumed (89.7% and n= 117, respectively). Reptiles were the second most important prey, represented by one skink species (Chioninia stangeri) and an unidentified gecko species. The remainder of the identified prey consisted of one bird species (Passer iagoensis) and one undetermined Tettigoniidae species (Insecta). No endangered species were identified in scats of this introduced predator, but future surveys must be carried out to further avoid threats to the island's biodiversity.

Proceedings of the 26th annual international ACM SIGIR conference on Research and development in informaion retrieval - SIGIR '03, 2003

In general terms the evaluation of a summary depends on how close it is to the chief points in th... more In general terms the evaluation of a summary depends on how close it is to the chief points in the source text. This begets the question as to what are the chief points in the source text and how is this information used in itself in identifying the source text. This is crucially important when we discuss automatic evaluation of summaries. So the question of main points is the source text. Typically, this would be around a nucleus of keywords. However, the salience, the frequency, and the relationship of the text with other texts in the collection (of these keywords is perhaps) are important. Text categorisation using neural networks explicates these points well and also has a practical impact.

Lecture Notes in Computer Science

Recent contributions have uncovered the potential of network coding, i.e. algebraic mixing of mul... more Recent contributions have uncovered the potential of network coding, i.e. algebraic mixing of multiple information flows in a network, to provide enhanced security in packet oriented wireless networks. We focus on exploiting network coding for secret key distribution in a sensor network with a mobile node. Our main contribution is a set of extensions for a simple XOR based scheme,

Security and Communication Networks, 2011

Q25 The vision towards the Network of the Future cannot be separated from the fact that today's n... more Q25 The vision towards the Network of the Future cannot be separated from the fact that today's networks, and networking services are subject to sophisticated and very effective attacks. When these attacks first appeared, spoofing and distributed denial-of-service attacks were treated as apocalypse for networking. Now, they are considered moderate damage, whereas more sophisticated and inconspicuous attacks, such as botnets activities, might have greater and far reaching impact. As the Internet is expanding to mobile phones and 'smart dust' and as its social coverage is liberalized towards the realization of ubiquitous computing (with communication), the concerns on security and privacy have become deeper and the problems more challenging than ever. Redesigning the Internet as the Network of the Future is self-motivating for researchers, and security and privacy cannot be provided again as separate, external, add-on, solutions. In this paper, we discuss the security and privacy challenges of the Network of the Future and try to delimit the solutions space on the basis of emerging techniques. We also review methods that help the quantification of security and privacy in an effort to provide a more systematic and quantitative treatment of the area in the future.

2010 IEEE Global Telecommunications Conference GLOBECOM 2010, 2010

We consider distributed storage over two untrusted networks, whereby coding is used as a means to... more We consider distributed storage over two untrusted networks, whereby coding is used as a means to achieve a prescribed level of confidentiality. The key idea is to exploit the algebraic structure of the Vandermonde matrix to mix the input blocks, before they are stored in different locations. The proposed scheme ensures that eavesdroppers with access to only one of the networks are unable to decode any symbol even if they are capable of guessing some of the missing blocks. Informationtheoretic techniques allow us to quantify the achievable level of confidentiality. Moreover, the proposed approach is shown to offer low complexity and optimal rate.

Journal of Ornithology, 2013

This study addresses for the first time the issue of pigeon (genus Columba) phylogeny within the ... more This study addresses for the first time the issue of pigeon (genus Columba) phylogeny within the archipelagos of Madeira (Columba trocaz) and Azores (C. palumbus azorica), located in the singular biogeographic area of Macaronesia. The phylogeny of these endemic pigeons was inferred based on mitochondrial (cytochrome b and cytochrome c oxidase I) and nuclear (b-fibrinogen intron 7) genetic markers through multiple approaches. Despite the non-monophyletic pattern for the insular endemic species recovered in the phylogenies, topology tests presented somewhat different results. C. trocaz, the Madeiran endemic species, clustered strongly with the Canarian endemic C. bollii, and these two are thus more closely related to each other than C. bollii to C. junoniae, the other endemic species of Canary Islands, which seems to have diverged independently. Moreover, C. trocaz was found to be phylogenetically closer to C. bollii than to C. palumbus from mainland Europe and Azores Islands. No genetic differentiation was found between the continental C. p. palumbus and the endemic C. p. azorica, which suggests a relatively recent colonisation event of the Azores Islands. Keywords Columba Á Endemic pigeons Á Macaronesia Á Phylogeny Á Mitochondrial DNA Á b-Fibrinogen intron 7 Zusammenfassung Phylogenetische Ursprü nge endemischer Taubenarten auf Madeira (Columba trocaz) und den Azoren (Columba palumbus azorica) Diese Studie untersucht erstmalig phylogenetische Fragen bei Tauben (Gattung Columba) auf den Inselgruppen Communicated by M. Wink.

Marine Environmental Research, 1999

Mercury concentrations in 1809 egg and plumage samples of adults and chicks of seabirds from colo... more Mercury concentrations in 1809 egg and plumage samples of adults and chicks of seabirds from colonies in the Portuguese Atlantic (3040° N, 832° W) were determined. Species and tissues were selected to ensure varied levels of ecological (epipelagic vs mesopelagic), ...

Journal of Ornithology, 2010

IEEE Transactions on Information Forensics and Security, 2008

IEEE Transactions on Information Forensics and Security, 2012

We focus on the problem of secure distributed storage over multiple untrusted clouds or networks.... more We focus on the problem of secure distributed storage over multiple untrusted clouds or networks. Our main contribution is a low complexity scheme that relies on erasure coding techniques for achieving prescribed levels of confidentiality and reliability. Using matrices that have no singular square submatrices, we subject the original data to a linear transformation. The resulting coded symbols are then stored in different networks. This scheme allows users with access to a threshold number of networks to reconstruct perfectly the original data, while ensuring that eavesdroppers with access to any number of networks smaller than this threshold are unable to decode any of the original symbols. This holds even if the attackers are able to guess some of the missing symbols. We further quantify the achievable level of security, and analyze the complexity of the proposed scheme.

The Condor, 2002

We studied the temporal diet variation of the endemic Madeira Laurel Pigeon (Columba trocaz) and ... more We studied the temporal diet variation of the endemic Madeira Laurel Pigeon (Columba trocaz) and fruit resource availability in the laurel forests of northwestern Madeira Island, during 1996 and 1997. We studied a total of 224 fecal samples using microhistological methods and conducted surveys of fruiting phenology throughout a year. Fruits (pulp and seeds) represented 57% of the optical fields analyzed. Leaves and flowers constituted 38% and Ͻ1% respectively. Over 33 plant species were identified in the fecal samples. Fruits of Ocotea foetens, Laurus azorica, Persea indica, and Ilex canariensis (fruits and leaves) were the most frequently detected food items. Most seeds were defecated intact (Ilex canariensis, Myrica faya, Visnea mocanera, Ocotea foetens, and Apollonias barbujana), except in the case of Laurus azorica where most were damaged. The diet showed a marked seasonal variation. Fruits constituted the major component of the diet in winter and autumn, whereas leaves were frequent in spring and summer. The presence of fruits in the diet was concordant with their availability, and leaves and flowers became important when fruits were scarce. This fact suggests that the Madeira Laurel Pigeon is capable of dietary switching, corresponding to temporal variations in food resource availability. This microhistological technique shows promise for study of the diets of pigeons and other herbivorous bird species.

Bird Conservation International, 2009

It is widely accepted that the gadfly petrels of the Macaronesian islands comprise three closely ... more It is widely accepted that the gadfly petrels of the Macaronesian islands comprise three closely related and morphologically similar taxa, Petrodroma madeira from Madeira island, P. deserta (also treated as P. feae deserta) from Bugio and P. feae (also treated as P. feae feae) from Cape Verde Islands. However, the taxonomic rank of each taxon is not well defined, and has been subject to a long debate. Partial sequences of cytochrome b (893 bp) from 39 individuals (five from Madeira, 18 from nearby Bugio, and 16 from Fogo) and morphometric data from five characters from 102 individuals (74 from Bugio and 28 from Fogo in Cape Verde), were used to compare and estimate phylogenetic relationships and the taxonomic status of these petrels. In the phylogenetic analysis and sequence divergence estimation, we also include 23 sequences of 19 Pterodroma species available from GenBank. Our results show that Macaronesian gadfly petrels form a monophyletic clade. Birds from Bugio and Cape Verde are the most closely related taxa followed by those from Madeira. The group formed by the three taxa studied is closely related to Bermuda Petrel P. cahow and Black-capped Petrel P. hasitata. A hypothesis for the colonization of the islands is presented. The level of sequence divergence is sufficient to consider the populations of Bugio and Cape Verde as separate species. Reproductive isolation is supported by exclusive haplotypes and fixed changes. Despite the presence of some significant differences in bill and tarsus measurements, the two species seem to be morphologically similar because the great overlap of variation intervals in the measurements hinders identification. It therefore appears suitable for consideration as a cryptic species. An important conservation implication is that the world population of both species is very small; if treated as a full species, deserta on Bugio may qualify for uplisting to 'Vulnerable' on the IUCN Red List. In the past, colonies were considered as different subspecies within Soft-plumaged Petrel P. mollis, a species with a wide geographical distribution throughout the Antarctic or Southern Ocean, Indian and Atlantic Oceans, characterized by variations in morphology, colouration and breeding behaviour (Bretagnolle 1995). The individuals breeding on Bugio were considered as P. m. deserta, and those from Cape Verde islands as P. m. feae (Mathews 1934a, b, Bannerman and Bannerman 1965, 1968). Bourne (1955) suggested raising the taxon from Bugio to specific level, P. deserta. Based on morphology, colouration and calls, Bretagnolle (1995) suggested splitting P. mollis into two distinct species: P. mollis in the South Atlantic and P. feae in the North Atlantic, with subspecies P. f. feae, P. f. madeira and P. f. deserta assigned to Cape Verde, Madeira and Bugio respectively. Other studies (Bourne 1983, Imber 1985, Warham 1990) proposed splitting the Northeastern Atlantic petrels from the P. mollis complex and suggested a species rank for the birds of Madeira (P. madeira) and those of Bugio and Cape Verde islands (P. feae). Recently, using morphological and mitochondrial DNA sequence data (cytochrome b), Zino et al. (2008) concluded that breeding colonies from Madeira and Desertas should be considered different species, as already suggested by previous studies (Bourne 1983, Imber 1985, Zino and Zino 1986). Emphasizing the recognition of the Madeira and Desertas gadfly petrels as distinct species, Sangster et al. (2002) suggested that they diverged 840,000 years ago, in the Early Pleistocene. Petrels from Bugio have been found to be morphologically similar to those from Cape Verde

Bird Conservation International, 1999

SummaryA survey was undertaken in 1995 to assess the conservation status of the Madeira Laurel Pi... more SummaryA survey was undertaken in 1995 to assess the conservation status of the Madeira Laurel Pigeon Columba trocaz, a threatened species endemic to the Island of Madeira. The first large scale survey was carried out 1986, following the cessation of legal hunting of the species, to provide a baseline for future monitoring of population changes. The current study therefore aims to (1) compare population size with those of 1986 and (2) employ distance sampling methods (not used in 1986) to obtain estimates of population density and size. Eighteen transects (13 repeated from the 1986 survey and five new) were conducted in the four main areas of laurel forest. Pigeon numbers had increased on nearly all transects but some of the highest increases, proportionately and often numerically, were in areas with lower numbers in 1986. We estimate the current population to be 10,400 individuals, a considerable increase since 1986, probably due to a ban on hunting. As laurel forest habitat is now...

Bird Conservation International, 2004

The diet of the endemic Madeira Laurel Pigeon Columba trocaz in agricultural and forest areas of ... more The diet of the endemic Madeira Laurel Pigeon Columba trocaz in agricultural and forest areas of Madeira Island was studied in 1997 by means of microhistological analysis of 157 faecal samples, 94 from two of the main agricultural zones and 63 from a laurel forest. Cabbage was the most important component of the diet in agricultural areas, representing more than 54% of the optical fields analysed. Samples collected further from the forest contained a higher proportion of cabbage. Native fruits did not figure highly in the samples collected from agricultural areas and crop plants did not appear in the forest samples, suggesting a degree of dietary separation and that some individuals may concentrate on crops. Madeira Laurel Pigeon is normally a highly frugivorous species and fruit availability is relatively high in winter when the birds go to agricultural areas to feed. This suggests that it is not a shortage of natural foods that causes them to leave the forest. The unpopularity of ...

Biological Conservation, 2006

This study was conducted over a two year period in the north west of Madeira Island (Macaronesian... more This study was conducted over a two year period in the north west of Madeira Island (Macaronesian Atlantic Islands, Portugal). It investigates the relationship between fruiting patterns in the indigenous forest and the use by the Madeira laurel pigeon of forest habitats and cultivated areas. ...

Event modelling requires a good understanding of the modes used in communicating the events, incl... more Event modelling requires a good understanding of the modes used in communicating the events, including natural language, graphs and images. A case study of financial market movement, where text, or news wires, and graphical information, or a financial time series, were correlated, is described. This leads to a need for automatic text classification: a method based on unsupervised neural networks and autonomous assignment of keywords is described. These are preliminary results of an EU 5 Framework Project –GIDA (No. IST 2000-31123). Methods of corpus linguistics and terminology are used to underpin the methods.

Acta Theriologica, 2010

In tro duc tion Fe ral cats Felis catus Linnaeus, 1758 have be come a top pred a tor in the food ... more In tro duc tion Fe ral cats Felis catus Linnaeus, 1758 have be come a top pred a tor in the food chains on islands where they were in tro duced (Nogales et al. 1992), con trib ut ing to the de cline and ex tinc tion of nu mer ous na tive spe cies world wide (Le ver 1994, Tershy et al. 2002). From con ti nents (Dickman 1996) to is lands of con ti nen tal or i gin [241]

acta ethologica, 2006

Previous studies of Cory's shearwater nesting biology suggest that pairs nesting at very close ra... more Previous studies of Cory's shearwater nesting biology suggest that pairs nesting at very close range to one another lay their eggs more synchronously than the colony as a whole. However, such apparent synchrony could be confounded by the existence of spatial structure in the quality of nesting sites and, hence, quality of the birds occupying the nests. If laying dates differ between sites of different quality, then synchrony is just a by-product of the spatial arrangement of nest sites. In this study, we show that when studying laying dates in artificial nests of uniform quality, no local synchronization of laying could be detected. We point to other shortcomings of previous analyses and conclude that, although Cory's shearwaters show remarkably synchronized attendance behaviors at the nesting sites, there is no conclusive evidence showing that laying dates are influenced by the behavior of near neighbors.