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Search Results: 1 - 10 of 611331 matches for " Rodrigo A. B. da;Almeida "
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Three electrode electrochemical microfluidic cell: construction and characterization
Silva, Rodrigo A. B. da;Almeida, Edimar G. N. de;Rabelo, Adriano C.;Silva, Abílio T. C. da;Ferreira, Lucas F.;Richter, Eduardo M.;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000700006
Abstract: this work describes the construction and characterization of an electrochemical flow-through microcell with the three electrodes (working, pseudo-reference, and auxiliary) inserted in microchannels with thickness smaller than 20 μm. these microchannels were constructed between two stacked polycarbonate slides using one or more overlapped toner masks as spacer. this strategy allows the construction of microcells with a variable internal volume on the working electrode (0.6 to 2.4 μl). three different materials were optimized as electrodes: gold film or graphite-epoxy composite as working electrode, silver-epoxy composite as pseudo-reference electrode and, graphite-epoxy composite as auxiliary electrode. the performance of the microfluidic cell was characterized by cyclic voltammetry, potentiometric stripping analysis at constant current, and square wave anodic stripping voltammetry using ferrocyanide and heavy metals (cu2+, hg2+, pb2+, and cd2+) as model analytes.
Local Community Identification through User Access Patterns
Rodrigo B. Almeida,Virgilio A. F. Almeida
Computer Science , 2002,
Abstract: Community identification algorithms have been used to enhance the quality of the services perceived by its users. Although algorithms for community have a widespread use in the Web, their application to portals or specific subsets of the Web has not been much studied. In this paper, we propose a technique for local community identification that takes into account user access behavior derived from access logs of servers in the Web. The technique takes a departure from the existing community algorithms since it changes the focus of in terest, moving from authors to users. Our approach does not use relations imposed by authors (e.g. hyperlinks in the case of Web pages). It uses information derived from user accesses to a service in order to infer relationships. The communities identified are of great interest to content providers since they can be used to improve quality of their services. We also propose an evaluation methodology for analyzing the results obtained by the algorithm. We present two case studies based on actual data from two services: an online bookstore and an online radio. The case of the online radio is particularly relevant, because it emphasizes the contribution of the proposed algorithm to find out communities in an environment (i.e., streaming media service) without links, that represent the relations imposed by authors (e.g. hyperlinks in the case of Web pages).
Genome mapping and expression analyses of human intronic noncoding RNAs reveal tissue-specific patterns and enrichment in genes related to regulation of transcription
Helder I Nakaya, Paulo P Amaral, Rodrigo Louro, André Lopes, Angela A Fachel, Yuri B Moreira, Tarik A El-Jundi, Aline M da Silva, Eduardo M Reis, Sergio Verjovski-Almeida
Genome Biology , 2007, DOI: 10.1186/gb-2007-8-3-r43
Abstract: A survey of mRNA and EST public databases revealed more than 55,000 totally intronic noncoding (TIN) RNAs transcribed from the introns of 74% of all unique RefSeq genes. Guided by this information, we designed an oligoarray platform containing sense and antisense probes for each of 7,135 randomly selected TIN transcripts plus the corresponding protein-coding genes. We identified exonic and intronic tissue-specific expression signatures for human liver, prostate and kidney. The most highly expressed antisense TIN RNAs were transcribed from introns of protein-coding genes significantly enriched (p = 0.002 to 0.022) in the 'Regulation of transcription' Gene Ontology category. RNA polymerase II inhibition resulted in increased expression of a fraction of intronic RNAs in cell cultures, suggesting that other RNA polymerases may be involved in their biosynthesis. Members of a subset of intronic and protein-coding signatures transcribed from the same genomic loci have correlated expression patterns, suggesting that intronic RNAs regulate the abundance or the pattern of exon usage in protein-coding messages.We have identified diverse intronic RNA expression patterns, pointing to distinct regulatory roles. This gene-oriented approach, using a combined intron-exon oligoarray, should permit further comparative analysis of intronic transcription under various physiological and pathological conditions, thus advancing current knowledge about the biological functions of these noncoding RNAs.The five million expressed sequence tags (ESTs) deposited into public sequence databases probably constitute the best representation of the human transcriptome. Human EST data have been extensively used to identify novel genes in silico [1,2] and novel exons of protein-coding genes [3-6]. Informatics analyses of the EST collection mapped to the human genome have also shown that the occurrence of overlapping sense/antisense transcription is widespread [7-9]. However, the complement of unspliced
Comparative Graph Theoretical Characterization of Networks of Spam and Legitimate Email
Luiz H. Gomes,Rodrigo B. Almeida,Luis M. A. Bettencourt,Virgilio Almeida,Jussara M. Almeida
Physics , 2005,
Abstract: Email is an increasingly important and ubiquitous means of communication, both facilitating contact between private individuals and enabling rises in the productivity of organizations. However the relentless rise of automatic unauthorized emails, a.k.a. spam is eroding away much of the attractiveness of email communication. Most of the attention dedicated to date to spam detection has focused on the content of the emails or on the addresses or domains associated with spam senders. Although methods based on these - easily changeable - identifiers work reasonably well they miss on the fundamental nature of spam as an opportunistic relationship, very different from the normal mutual relations between senders and recipients of legitimate email. Here we present a comprehensive graph theoretical analysis of email traffic that captures these properties quantitatively. We identify several simple metrics that serve both to distinguish between spam and legitimate email and to provide a statistical basis for models of spam traffic.
Oxidative stress biomarkers and aggressive behavior in fish exposed to aquatic cadmium contamination
Almeida, Jeane A.;Barreto, Rodrigo E.;Novelli, Ethel L. B.;Castro, Fabio J.;Moron, Sandro E.;
Neotropical Ichthyology , 2009, DOI: 10.1590/S1679-62252009000100013
Abstract: the objective of this study was to investigate the possible link between cadmium exposure, hepatic markers of oxidative stress and aggressive behavior in nile tilapia (oreochromis niloticus). fish were first exposed to 0.75 mg/l cdcl2 for 15 days (12 isolated fish for each group) and afterward a behavioral test was performed. fish from the control and cadmium-exposed groups were paired for 1 h (6 pairs of fish per group) for determination of aggressiveness parameters. immediately after the behavioral test, the animals were sacrificed and the liver was used to determine biochemical parameters. cadmium decreased aggression in nile tilapia. subordinate animals exposed to cadmium showed decreased glutathione peroxidase (gsh-px) activity compared to dominant ones. no alterations were observed in selenium-dependent glutathione peroxidase se-gsh-p and cu-zn superoxide dismutase activities, but total superoxide dismutase activity was increased in subordinate animals exposed to cadmium compared to subordinate control. catalase activity was increased in cadmium-exposed fish. lipoperoxide concentrations also increased in cadmium exposed fish indicating that cadmium toxicity may affect oxidative stress biomarkers in nile tilapia. social stress induced lipoperoxidation in nile tilapia, and subordinate animals exposed to cadmium responded with lower activities of liver antioxidant enzymes compared to dominant fish. the present study shows that cadmium exposure is capable of inducing changes in the social status and oxidative stress parameters in this species.
Improving Spam Detection Based on Structural Similarity
Luiz H. Gomes,Fernando D. O. Castro,Rodrigo B. Almeida,Luis M. A. Bettencourt,Virgilio A. F. Almeida,Jussara M. Almeida
Computer Science , 2005,
Abstract: We propose a new detection algorithm that uses structural relationships between senders and recipients of email as the basis for the identification of spam messages. Users and receivers are represented as vectors in their reciprocal spaces. A measure of similarity between vectors is constructed and used to group users into clusters. Knowledge of their classification as past senders/receivers of spam or legitimate mail, comming from an auxiliary detection algorithm, is then used to label these clusters probabilistically. This knowledge comes from an auxiliary algorithm. The measure of similarity between the sender and receiver sets of a new message to the center vector of clusters is then used to asses the possibility of that message being legitimate or spam. We show that the proposed algorithm is able to correct part of the false positives (legitimate messages classified as spam) using a testbed of one week smtp log.
Fauna de Hymenoptera em Ficus spp. (Moraceae) na Amaz?nia Central, Brasil
Nazareno, Alison G.;Silva, Ranyse B. Querino da;Pereira, Rodrigo A. S.;
Iheringia. Série Zoologia , 2007, DOI: 10.1590/S0073-47212007000400013
Abstract: the interaction between ficus (moraceae) and fig wasps is considered one of the most extreme examples of plant-insect mutualism. in the present study, we reported the fig wasp fauna associated with five ficus species in the central amazon, brazil, and considered some aspects of the pollination mode found in ficus (urostigma) cremersii, ficus (urostigma) greiffiana, ficus (urostigma) mathewsii, ficus (urostigma) pertusa e ficus (pharmacosycea) maxima. the study was carried out from april to july 2004, in the cities of manaus and presidente figueiredo (state of amazonas, brazil). the number of fig wasp species per host tree varied from one to 13. wasps of the genus pegoscapus cameron, 1906, pollinators of ficus (urostigma) spp., showed an active pollination mode. indeed, these species have coxal combs and pollen pockets to collect and transport pollen. tetrapus mayr, 1885 species, pollinators of ficus (pharmacosycea) spp., demonstrated a passive pollination mode and they do not show morphological traits adapted to collect and transfer pollen grains. besides fig wasps, f. (pharmacosycea) maxima and f. (urostigma) pertusa are associated with mites, ants (solenopsis sp., formicidae), beetles (staphylinidae) and larvae of diptera and lepidoptera.
Avalia??o da morfologia e propriedades termo-mecanicas em nanocompósitos de PVC
Silva, Rodrigo P. da;Mauler, Raquel S.;Oliveira, Ricardo V. B. de;Salles, Cleia A.;
Polímeros , 2010, DOI: 10.1590/S0104-14282010005000012
Abstract: the search for the use of reinforcement fillers into polymeric materials has been the great objective of researchers and industry. in this work pvc nanocomposites were obtained by melt blending in a single-screw extruder. additionally, three different organophilic montmorillonite concentrations of 1, 2 and 5% wt were incorporated. these were characterized by morphology, thermal and thermo-dynamic-mechanical properties. the degree of intercalation and exfoliation of nanocomposites was characterized by met. the thermogravimetric analysis did not show an increase in the thermal stability of the nanocomposites with the clay content.
Primary pulmonary paraganglioma: case report and literature review
Silva Rodrigo Afonso da,Gross Jefferson Luiz,Haddad Fábio J.,Toledo Cíntia A. B.
Clinics , 2006,
The taxonomic status of Scilla beirana Samp. (Hyacinthaceae)
Roselló, Josep A.,Caldas, Francisco B.,Almeida da Silva, Rubim M.
Anales del Jardín Botánico de Madrid , 1998,
Abstract: Populations of Scilla beirana Samp. were sampled in NW Portugal and compared with its relatives S. ramburei Boiss, and S. peruviana L. Leaf and scape anatomy, morphology, chromosome number and idiogram were identical in S. beirana and S. ramburei, but differed from S. peruviana. Diagnostic characters previously used to discriminate S. beirana (width of leaves and flower number) showed continuous, but not clinal, variation, and failed to provide a clear-cut basis for identification and no other morphological attributes were found to separate the taxa. All available evidence suggests that S. beirana should be put into synonymy with S. ramburei, as was earlier suggested by COUTINHO (1935). Se muestreó Scilla beirana Samp. en diversas poblaciones del noroeste de Portugal y se comparó con dos táxones con los que se había relacionado previamente, S. ramburei Boiss, y S. peruviana L. La macromorfología, la anatomía de la hoja y escapo, el número cromosomático y el idiograma de S. beirana y S. ramburei fueron indistinguibles, pero diferentes de los de S. peruviana. Los caracteres diagnósticos que se habían utilizado previamente para discriminar a S. beirana -anchura foliar y número de flores- revelaron una variación continua y no permitieron diferenciarla de S. ramburei, en la cual debería ser incluida como sinónimo, tal como había sugerido COUTINHO (1935).
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