Modelo de Fisher-Kolmogorov em dinâmica populacional com capacidade de suporte espacialmente dependente

Pós-graduação em Física - IFT

Estimulador elétrico funcional com utilização de ponte H e fonte de corrente no estágio de potência

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Contribuição ao estudo de lajes lisas unidirecionais de concreto armado com pilares retangulares ao puncionamento

São apresentadas análises das recomendações para estimar a resistência ao puncionamento de lajes lisas de acordo com a versão atual da norma brasileira, a NBR 6118:2003, que não considera o efeito da retangularidade de pilares internos, e sua predecessora, a NBR 6118:1980. Em seções transversais retangulares, o índice de polarização das tensões de cisalhamento é crescente. Isto altera a forma de ruptura da laje, já que a punção se inicia em torno das extremidades da seção do pilar, não se estendendo para os lados maiores, como prescreve a norma, comportamento este que reduz a resistência última das lajes frente às estimativas normativas. São apresentados os resultados de uma análise numérica por elementos finitos (M.E.F.) e uma proposta para melhorar a ductilidade das lajes lisas através das dimensões mínimas dos pilares. Observou-se que a NBR 6118:1980 mostrou-se conservadora e que as estimativas da NBR 6118: 2003 podem ser melhoradas.

Provisioning Strategies of Antarctic Fur Seals and Chinstrap Penguins Produce Different Responses to Distribution of Common Prey and Habitat

Central-place foragers that must return to a breeding site to deliver food to offspring are faced with trade-offs between prey patch quality and distance from the colony. Among colonial animals, pinnipeds and seabirds may have different provisioning strategies, due to differences in their ability to travel and store energy. We compared the foraging areas of lactating Antarctic fur seals and chinstrap penguins breeding at Seal Island, Antarctica, to investigate whether they responded differently to the distribution of their prey (Antarctic krill and myctophid fish) and spatial heterogeneity in their habitat. Dense krill concentrations occurred in the shelf region near the colony. However, only brooding penguins, which are expected to be time-minimizers because they must return frequently with whole food for their chicks, foraged mainly in this proximal shelf region. Lactating fur seals and incubating penguins, which can make longer trips to increase energy gain per trip, and so are expected to be energy-maximizers, foraged in the more distant (>20 km from the island) slope and oceanic regions. The shelf region was characterized by more abundant, but lower-energy-content immature krill, whereas the slope and oceanic regions had less abundant but higher-energy-content gravid krill, as well as high-energy-content myctophids. Furthermore, krill in the shelf region undertook diurnal vertical migration, whereas those in the slope and oceanic regions stayed near the surface throughout the day, which may enhance the capture rate for visual predators. Therefore, we sug- gest that the energy-maximizers foraged in distant, but potentially more profitable feeding regions, while the time-minimizers foraged in closer, but potentially less profitable regions. Thus, time and energy constraints derived from different provisioning strategies may result in sympatric colonial predator species using different foraging areas, and as a result, some central-place foragers use sub- optimal foraging habitats, in terms of the quality or quantity of available prey.

Estimulador elétrico funcional com utilização de ponte H e fonte de corrente no estágio de potência

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A computer-controlled color vision test for children based on the Cambridge Colour Test

The present study aimed at providing conditions for the assessment of color discrimination in children using a modified version of the Cambridge Colour Test (CCT, Cambridge Research Systems Ltd., Rochester, UK). Since the task of indicating the gap of the Landolt C used in that test proved counterintuitive and/or difficult for young children to understand, we changed the target Stimulus to a patch of color approximately the size of the Landolt C gap (about 7 degrees Of Visual angle at 50 cm from the monitor). The modifications were performed for the CCT Trivector test which measures color discrimination for the protan, deutan and tritan confusion lines. Experiment I Sought to evaluate the correspondence between the CCT and the child-friendly adaptation with adult subjects (n = 29) with normal color vision. Results showed good agreement between the two test versions. Experiment 2 tested the child-friendly software with children 2 to 7 years old (n = 25) using operant training techniques for establishing and maintaining the subjects` performance. Color discrimination thresholds were progressively lower as age increased within the age range tested (2 to 30 years old), and the data-including those obtained for children-fell within the range of thresholds previously obtained for adults with the CCT. The protan and deutan thresholds were consistently lower than tritan thresholds, a pattern repeatedly observed in adults tested with the CCT. The results demonstrate that the test is fit for assessment of color discrimination in young children and may be a useful tool for the establishment of color vision thresholds during development.

Unraveling the drivers of community dissimilarity and species extinction in fragmented landscapes

Communities in fragmented landscapes are often assumed to be structured by species extinction due to habitat loss, which has led to extensive use of the species-area relationship (SAR) in fragmentation studies. However, the use of the SAR presupposes that habitat loss leads species to extinction but does not allow for extinction to be offset by colonization of disturbed-habitat specialists. Moreover, the use of SAR assumes that species richness is a good proxy of community changes in fragmented landscapes. Here, we assessed how communities dwelling in fragmented landscapes are influenced by habitat loss at multiple scales; then we estimated the ability of models ruled by SAR and by species turnover in successfully predicting changes in community composition, and asked whether species richness is indeed an informative community metric. To address these issues, we used a data set consisting of 140 bird species sampled in 65 patches, from six landscapes with different proportions of forest cover in the Atlantic Forest of Brazil. We compared empirical patterns against simulations of over 8 million communities structured by different magnitudes of the power-law SAR and with species-specific rules to assign species to sites. Empirical results showed that, while bird community composition was strongly influenced by habitat loss at the patch and landscape scale, species richness remained largely unaffected. Modeling results revealed that the compositional changes observed in the Atlantic Forest bird metacommunity were only matched by models with either unrealistic magnitudes of the SAR or by models ruled by species turnover, akin to what would be observed along natural gradients. We show that, in the presence of such compositional turnover, species richness is poorly correlated with species extinction, and z values of the SAR strongly underestimate the effects of habitat loss. We suggest that the observed compositional changes are driven by each species reaching its individual extinction threshold: either a threshold of forest cover for species that disappear with habitat loss, or of matrix cover for species that benefit from habitat loss.

Enhanced Expression of Heme Oxygenase-1 and Carbon Monoxide Excitatory Effects in Oxytocin and Vasopressin Neurones During Water Deprivation

A growing body of evidence indiates that carbon monoxide (CO) acts as a gas neurotransmitter within the central nervous system. Although CO has been shown to affect neurohypophyseal hormone release in response to osmotic stimuli, the precise sources, targets and mechanisms underlying the actions of CO within the magnocellular neurosecretory system remain largely unknown. In the present study, we combined immunohistochemistry and patch-clamp electrophysiology to study the cellular distribution of the CO-synthase enzyme heme oxygenase type 1 (HO-1), as well as the actions of CO on oxytocin (OT) and vasopressin (VP) magnocellular neurosecretory cells (MNCs), in euhydrated (EU) and 48-h water-deprived rats (48WD). Our results show the expression of HO-1 immunoreactivity both in OT and VP neurones, as well as in a small proportion of astrocytes, both in supraoptic (SON) and paraventricular (PVN) nuclei. HO-1 expression, and its colocalisation with OT and VP neurones within the SON and PVN, was significantly enhanced in 48WD rats. Inhibition of HO activity with chromium mesoporphyrin IX chloride (CrMP; 20 mu m) resulted in a slight membrane hyperpolarisation in SON neurones from EU rats, without significantly affecting their firing activity. In 48WD rats, on the other hand, CrMP resulted in a more robust membrane hyperpolarisation, significantly decreasing neuronal firing discharge. Taken together, our results indicate that magnocellular SON and PVN neurones express HO-1, and that CO acts as an excitatory gas neurotransmitter in this system. Moreover, we found that the expression and actions of CO were enhanced in water-deprived rats, suggesting that the state-dependent up-regulation of the HO-1/CO signalling pathway contributes to enhance MNCs firing activity during an osmotic challenge.

Regulation of ventral surface CO2/H+-sensitive neurons by purinergic signalling

Central chemoreception is the mechanism by which the brain regulates breathing in response to changes in tissue CO2/H+. Abrainstemregion called the retrotrapezoid nucleus (RTN) contains a population of CO2/H+-sensitive neurons that appears to function as an important chemoreceptor. Evidence also indicates that CO2-evoked ATP release from RTN astrocytes modulates activity of CO2/H+-sensitive neurons; however, the extent to which purinergic signalling contributes to chemoreception by RTN neurons is not clear and the mechanism(s) underlying CO2/H+-evoked ATP release is not fully elucidated. The goals of this study are to determine the extent to which ATP contributes to RTN chemoreception both in vivo and in vitro, andwhether purinergic drive to chemoreceptors relies on extracellularCa(2+) or gap junction hemichannels. We also examine the possible contribution of P2Y1 receptors expressed in theRTNto the purinergic drive to breathe. We showthat purinergic signalling contributes, in part, to the CO2/H+ sensitivity of RTN neurons. In vivo, phrenic nerve recordings of respiratory activity in adult rats show that bilateral injections of pyridoxal-phosphate-6-azophenyl-2',4'-disulfonate (PPADS, a P2 receptor blocker) decreased the ventilatory response to CO2 by 30%. In vitro, loose-patch recordings from RTN neurons show that P2 receptor blockers decreased responsiveness to both 10% and 15% CO2 also by 30%. In the slice, the contribution of purinergic signalling to RTN chemoreception did not increase with temperature (22-35 degrees C) and was retained in low extracellular Ca2+ medium. Conversely, the gap junction blockers carbenoxolone and cobalt decreased neuronal CO2/H+ sensitivity by an amount similar to P2 receptor antagonists. Inhibition of the P2Y1 receptor in the RTN had no effect on CO2 responsivness in vitro or in vivo; thus, the identity of P2 receptors underlying the purinergic component of RTN chemoreception remains unknown. These results support the possibility that CO2/H+-evoked ATP release is mediated by a mechanism involving gap junction hemichannels.

Characterization of selectivity and pharmacophores of type 1 sea anemone toxins by screening seven Na-v sodium channel isoforms

During their evolution, animals have developed a set of cysteine-rich peptides capable of binding various extracellular sites of voltage-gated sodium channels (VGSC). Sea anemone toxins that target VGSCs delay their inactivation process, but little is known about their selectivities. Here we report the investigation of three native type 1 toxins (CGTX-II, delta-AITX-Bcg1a and delta-AITX-Bcg1b) purified from the venom of Bunodosoma cangicum. Both delta-AITX-Bcg1a and delta-AITX-Bcg1b toxins were fully sequenced. The three peptides were evaluated by patch-clamp technique among Nav1.1-1.7 isoforms expressed in mammalian cell lines, and their preferential targets are Na(v)1.5 > 1.6 > 1.1. We also evaluated the role of some supposedly critical residues in the toxins which would interact with the channels, and observed that some substitutions are not critical as expected. In addition, CGTX-II and delta-AITX-Bcg1a evoke different shifts in activation/inactivation Boltzmann curves in Nav1.1 and 1.6. Moreover, our results suggest that the interaction region between toxins and VGSCs is not restricted to the supposed site 3 (S3-54 linker of domain IV), and this may be a consequence of distinct surface of contact of each peptide vs. targeted channel. Our data suggest that the contact surfaces of each peptide may be related to their surface charges, as CGTX-II is more positive than delta-AITX-Bcg1a and delta-AITX-Bcg1b. (C) 2011 Elsevier Inc. All rights reserved.

Abdominal compression: A new intraoperative maneuver to detect chyle fistulas during left neck dissections that include level IV

Background Chyle fistulas may occur after left neck dissections that include level IV, due to injury of the thoracic duct or of 1 of its major branches. Despite being unusual, this complication carries substantial postoperative morbidity and even mortality. So far, no effective intraoperative maneuver has been reported to detect this fistula at the end of a neck dissection. In this cohort study, we sought to describe a simple new maneuver, intraoperative abdominal compression, which can effectively help to identify an open major lymphatic duct on level IV at the end of a neck dissection. Patients and Methods From March 1989 to September 2010, 206 patients underwent neck dissections involving left level IV, and underwent intraoperative abdominal compression. There were 119 men and 87 women, with ages ranging from 18 to 81 years (median, 52 years). One hundred forty-four patients had squamous cell carcinomas, 54 had thyroid carcinomas, 5 had malignant melanomas, and 3 had salivary cancers. Distribution by type of left neck dissection was: selective including levels II, III, and IV (73 cases; 35.4%), selective including levels II, III, IV, and V (55 cases; 26.6%), selective including levels I, II, III, and IV (12 cases; 5.8%), modified radical (47 cases; 22.8%), and radical (19 cases; 9.2%). In all cases, at the end of the procedure, the endotracheal tube was temporarily disconnected from the ventilator. Keeping the dissected level IV area under clear visualization, an abdominal compression was performed. At this moment, any detected lymphatic leak was carefully clamped and tied with nonabsorbable sutures. After ventilating the patient, the intraoperative abdominal compression was repeated to reassure complete occlusion of the lymphatic vessel. Results In 13 cases (6.3%), a chyle leak was detected after performing the intraoperative abdominal compression. All leaks except for 2 were successfully controlled after 1 attempt. In these 2 patients, a patch of muscle and fat tissue was applied with fibrin glue on the top. In 1 of these patients, another chyle leak in a different location was detected only at the second intraoperative abdominal compression, and was also effectively closed. Postoperatively, there were 2 (1%) chyle fistulas, both among these 13 cases, and all were successfully managed with clinical measures only. No fistulas occurred among the remaining 193 patients in whom intraoperative abdominal compression did not demonstrate lymphatic leak. Conclusion To our knowledge, this is the first description of a specific maneuver to actively detect a lymphatic fistula at the end of a left neck dissection involving level IV. In this study, intraoperative abdominal compression was able to detect an open lymphatic vessel in 6.3% of the cases, as well as to assure its effective sealing in the remaining 93.7% of the patients. Moreover, no life-threatening high-volume fistula was noted in this study. (C) 2012 Wiley Periodicals, Inc. Head Neck, 2012

Rupture of the right ventricular free wall after myocardial infarction

Patient, 75 years-old, with free wall rupture of the right ventricle, corrected with prolene 3.0 points anchored in bovine pericardium patch, promoting the closure of the rupture. The patient was discharged on the 59th day after surgery in good clinical ans laboratorial conditions.

Sedimentary processes on the NW Iberian Continental Shelf since the Little Ice Age

The OMEX core CD110 W90, retrieved from the Douro Mud Patch (DMP) off the River Douro in the north of Portugal, records the period since the beginning of Little Ice Age (LIA). The core chronology is based upon the data attributes for Pb-210, Cs-137 and a C-14 dating from a level near the core base. Geochemical, granulometric, microfaunal (benthic foraminifera) and compositional data suggest the occurrence of precipitation changes which may have been, at least partially, influenced by the North Atlantic Oscillation (NAO), that contributes to the regulation of the ocean-atmosphere dynamics in the North Atlantic. Southwesterly Atlantic storm track is associated with the negative phases of the NAO, when the Azores High is anomalously weak, higher oceanographic hydrodynamism, downwelling events and increased rainfall generally occurs. Prevalence of these characteristics during the LIA left a record that corresponds to phases of major floods. During these phases the DMP received a higher contribution of relatively coarse-grained terrigenous sediments, enriched in quartz particles, which diluted the contribution of other minerals, as indicated by reduced concentrations of several lithogenic chemical elements such as: Al, As, Ba, Ce, Co, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Rb, Sc, Sn, Th, V and Y. The presence of biogenic carbonate particles also underwent dilution, as revealed by the smaller abundance of foraminifera and correlative lower concentrations of Ca and Sr. During this period, the DMP also received an increased contribution of organic matter, indicated by higher values of lignin remains and a benthic foraminifera high productivity index, or BFHP, which gave rise to early diagenetic changes with pyrite formation. Since the beginning of the 20th century this contribution diminished, probably due to several drier periods and the impact of human activities in the river basins, e.g. construction of dams, or, on the littoral areas, construction of hard-engineering structures and sand extraction activities. During the first half of the 20th century mainly positive phases of the NAO prevailed, caused by the above normal strengthening of the subtropical high pressure centre of the Azores and the deepening of the low pressure centre in Iceland. These phases may have contributed to the reduction in the supply of both terrigenous sediments and organic matter from shallow water to the DMP. During the positive phases of the NAO, sedimentation became finer. The development of mining and industrial activities during the 20th century is marked, in this core, by higher concentrations of Pb. Furthermore, the erosion of heaps resulting from wolfram exploitation leaves its signature as a peak of W concentrations recorded in the sediments of the DMP deposited between the 1960s and the 1990s. Wolfram exploitation was an important activity in the middle part of the 20th century, particularly during the period of the Second World War. (C) 2012 Elsevier Ltd. All rights reserved.

GENERALIZED FINITE ELEMENT METHOD ON NONCONVENTIONAL HYBRID-MIXED FORMULATION

The generalized finite element method (GFEM) is applied to a nonconventional hybrid-mixed stress formulation (HMSF) for plane analysis. In the HMSF, three approximation fields are involved: stresses and displacements in the domain and displacement fields on the static boundary. The GFEM-HMSF shape functions are then generated by the product of a partition of unity associated to each field and the polynomials enrichment functions. In principle, the enrichment can be conducted independently over each of the HMSF approximation fields. However, stability and convergence features of the resulting numerical method can be affected mainly by spurious modes generated when enrichment is arbitrarily applied to the displacement fields. With the aim to efficiently explore the enrichment possibilities, an extension to GFEM-HMSF of the conventional Zienkiewicz-Patch-Test is proposed as a necessary condition to ensure numerical stability. Finally, once the extended Patch-Test is satisfied, some numerical analyses focusing on the selective enrichment over distorted meshes formed by bilinear quadrilateral finite elements are presented, thus showing the performance of the GFEM-HMSF combination.

Descriptions of Thereza murutinga sp. nov. and Pristocnemis caipira sp. nov., and new records of Caelopyginae (Opiliones: Laniatores: Gonyleptidae)

Two new species of Caelopyginae are described: Pristocnemis caipira sp. nov. from Parque Nacional da Serra da Canastra, Minas Gerais, Brazil, and Thereza murutinga sp. nov., from Parati, Rio de Janeiro, Brazil. Pristocnemis caipira sp. nov. is diagnosed by shallow grooves on the dorsal scutum, a lower number of tarsal segments, presence of a spine on the anal operculum, large, pointed tubercles on the lateral margins of the dorsal scutum, and an absence of white patches on the dorsal scutum. Thereza murutinga sp. nov. is diagnosed by the combination of the following characters: incomplete median longitudinal groove on area III and absent on area II, prosoma much smaller than opisthosoma, and a large white patch covering the prosoma and whole areas of the opisthosomal scutum. A cladistic analysis including the two new species was performed to investigate their relationship within the subfamily. We obtained 927 trees of 185 steps (CI=0.4, RI=0.74), which corroborated the generic assignments of the new species, but infrageneric relationships remained unsolved. In addition, male genitalia of Ampheres luteus (Giltay) and genera Pristocnemis and Thereza are redescribed, new distribution records for Caelopyginae species are presented, and biogeographical implications are discussed.