Effective Properties Evaluation for Smart Composite Materials

The purpose of this article is to present a method which consists in the development of unit cell numerical models for smart composite materials with piezoelectric fibers made of PZT embedded in a non-piezoelectric matrix (epoxy resin). This method evaluates a globally homogeneous medium equivalent to the original composite, using a representative volume element (RVE). The suitable boundary conditions allow the simulation of all modes of the overall deformation arising from any arbitrary combination of mechanical and electrical loading. In the first instance, the unit cell is applied to predict the effective material coefficients of the transversely isotropic piezoelectric composite with circular cross section fibers. The numerical results are compared to other methods reported in the literature and also to results previously published, in order to evaluate the method proposal. In the second step, the method is applied to calculate the equivalent properties for smart composite materials with square cross section fibers. Results of comparison between different combinations of circular and square fiber geometries, observing the influence of the boundary conditions and arrangements are presented.

Pb0.90Ba0.10Zr0.40Ti0.60O3 Nanostructured Ferroelectric Ceramics Prepared by Spark Plasma Sintering

Nanostructured Pb0.90Ba0.10Zr0.40Ti0.60O3 dense ceramics presenting an average grain size of 62 +/- 5 nm was prepared by the polymeric precursor method and using the spark plasma sintering technique. The dielectric permittivity curves versus temperature exhibit broad anomaly, indicative of a diffuse phase transition. This result can be explained by the spread of Curie temperatures which are expected to depend on the degree of tetragonality related to the grain size distribution. A pronounced decrease in the maximum of the dielectric permittivity value is attributed to the existence of a large amount of grain boundaries which are non-ferroelectric regions.

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.

Distribution patterns of a marsh vegetation metacommunity in relation to habitat configuration

The identification of the factors behind the distribution of plant communities in patched habitats may prove useful towards better understanding how ecosystems function. Plant assemblages are especially important for wetland productivity and provide food and habitat to animals. The present study analyses the distribution of a metacommunity of helophytes and phreatophytes in a wetland complex in oder to identify the effects of habitat configuration on the colonisation process. Ponds with wide vegetated shores and a short distance to a big (> 10 ha) wetland, had higher species richness. The average percentage of surface covered by each species in all the wetlands correlated positively with the number of patches occupied by that species. Moreover, the community presented a nested pattern (species-poor patches were subsets of species-rich patches), and this pattern came about by selective extinction and colonisation processes. We also detected the presence of some idiosyncratic species that did not follow nestedness. Conservation managers should attempt to maximise the vegetated shore width and to reduce the degree of isolation to enhance species richness. Furthermore, a single large and poorly isolated reserve may have the highest level of biodiversity in emergent vegetation species in this wetland complex, however, the particular ecological requirements of idiosyncratic species should also be taken into account when managing this type of community.

Terrestrial non-volant small mammals in agro-silvicultural landscapes of Southeastern Brazil

The area covered by Eucalyptus plantations is significantly increasing in Brazil for economic reasons. However, the impact of such land use change is still unknown. In this study we evaluated the spatial-temporal distribution and abundance of terrestrial non-volant small mammals on a recently converted landscape whose matrix is formed by Eucalyptus plantations up to 3 years of age. From August 2007 to July 2009 we carried out monthly sampling campaigns over a grid of 30 sampling units, formed by pitfall traps covering both the landscape matrix of Eucalyptus plantations (n = 18) and legal conservation areas of native vegetation (n = 7) and abandoned pastures (n = 5). A total of 1640 individuals from 14 species of the orders Didelphimorphia (4 spp.) and Rodentia (10 spp.) were captured. However, only three species of rodents (Olygorysomys flavescens, Oligoryzomys nigripes and Calomy tener) represented 81.8% of the total amount. Eucalyptus plantations had a lower species richness and abundance than the abandoned pasture and the remaining fragments of native vegetation. Although the present species are predominantly generalists, there is clear distinction among environments in terms of their species composition and relative abundance, which also present a pronounced time variation. The assemblage found in this study suggests that silvicultural landscapes still have some conservation value, with species that seem to be resident at the Eucalyptus plantations. Moreover, the presence of the native and abandoned pastures patches imbibed in the Eucalyptus plantation matrix may increase the carrying capacity of such a silvicultural system and these landscapes may play a role in maintaining local biodiversity. (C) 2012 Elsevier B.V. All rights reserved.

Land-use and land-cover change in Atlantic Forest landscapes

The Atlantic Forest is one of the most threatened tropical biomes, with much of the standing forest in small (less than 50 ha), disturbed and isolated patches. The pattern of land-use and land-cover change (LULCC) which has resulted in this critical scenario has not yet been fully investigated. Here, we describe the LULCC in three Atlantic Forest fragmented landscapes (Sao Paulo, Brazil) between 1960-1980s and 1980-2000s. The three studied landscapes differ in the current proportion of forest cover, having 10%, 30% and 50% respectively. Between the 1960s and 1980s. forest cover of two landscapes was reduced while the forest cover in the third landscape increased slightly. The opposite trend was observed between the 1980s and 2000s: forest regeneration was greater than deforestation at the landscapes with 10% and 50% of forest cover and, as a consequence, forest cover increased. By contrast, the percentage of forest cover at the landscape with 30% of forest cover was drastically reduced between the 1980s and 2000s. LULCC deviated from a random trajectory, were not constant through time in two study landscapes and were not constant across space in a given time period. This landscape dynamism in single locations over small temporal scales is a key factor to be considered in models of LULCC to accurately simulate future changes for the Atlantic Forest. In general, forest patches became more isolated when deforestation was greater than forest regeneration and became more connected when forest regeneration was greater than deforestation. As a result of the dynamic experienced by the study landscapes, individual forest patches currently consist of a mosaic of different forest age classes which is likely to impact bio-diversity. Furthermore, landscape dynamics suggests the beginning of a forest transition in some Atlantic Forest regions, what could be of great importance for biodiversity conservation due to the potential effects of young secondary forests in reducing forest isolation and maintaining a significant amount of the original biodiversity. (C) 2012 Elsevier B.V. All rights reserved.

Computational and experimental characterization of a low-cost piezoelectric valveless diaphragm pump

Flow pumps act as important devices in areas such as Bioengineering, Medicine, and Pharmacy, among other areas of Engineering, mainly for delivering liquids or gases at small-scale and precision flow rate quantities. Principles for pumping fluids based on piezoelectric actuators have been widely studied, since they allow the construction of pump systems for displacement of small fluid volumes with low power consumption. This work studies valveless piezoelectric diaphragm pumps for flow generation, which uses a piezoelectric ceramic (PZT) as actuator to move a membrane (diaphragm) up and down as a piston. The direction of the flow is guaranteed by valveless configuration based on a nozzle-diffuser system that privileges the flow in just one pumping direction. Most research efforts on development of valveless flow pump deal either with computational simulations based on simplified models or with simplified physical approaches based on analytical models. The main objective of this work is the study of a methodology to develop a low-cost valveless piezoelectric diaphragm flow pump using computational simulations, parametric study, prototype manufacturing, and experimental characterization. The parametric study has shown that the eccentricity of PZT layer and metal layer plays a key role in the performance of the pump.

Epidemiology of Brazilian spotted fever in the Atlantic Forest, state of Sao Paulo, Brazil

The tick-borne bacterium Rickettsia rickettsii is the aetiological agent of Brazilian spotted fever (BSF). The present study evaluated tick infestations on wild and domestic animals, and the rickettsial infection in these animals and their ticks in 7 forest areas adjacent to human communities in the Sao Paulo Metropolitan Area (SPMA). The results were compared to ecological traits of each sampled area. Two main tick species, Amblyomma aureolatum and Rhipicephalus sanguineus, were collected from dogs. The major ticks found on small mammals and birds were Ixodes loricatus and Amblyomma longirostre, respectively. Both anti-R. rickettsii antibodies and R. rickettsii-infected ticks were detected on dogs from only 2 areas in the southern part of the SPMA, which were considered to be endemic for BSF; the remaining 5 areas were considered to be non-endemic. Ecologically, the BSF-endemic areas clearly differed from the non-endemic areas by the presence of significantly more degraded forest patches in the former. The present results corroborate historical observations that have indicated that all human cases of BSF in the SPMA were contracted in the southern part of this metropolitan area. However, not all forest patches in the southern part of the SPMA were shown to be associated with BSF endemism.

Enzyme Microheterogeneous Hydration and Stabilization in Supercritical Carbon Dioxide

Supercritical carbon dioxide is a promising green-chemistry solvent for many enzyme-catalyzed chemical reactions, yet the striking stability of some enzymes in such unconventional environments is not well understood. Here, we investigate the stabilization of the Candida antarctica Lipase B (CALB) in supercritical carbon dioxide-water biphasic systems using molecular dynamics simulations. The preservation of the enzyme structure and optimal activity depend on the presence of small amounts of water in the supercritical dispersing medium. When the protein is at least partially hydrated, water molecules bind to specific sites on the enzyme surface and prevent carbon dioxide from penetrating its catalytic core. Strikingly, water and supercritical carbon dioxide cover the protein surface quite heterogeneously. In the first solvation layer, the hydrophilic residues at the surface of the protein are able to pin down patches of water, whereas carbon dioxide solvates preferentially hydrophobic surface residues. In the outer solvation shells, water molecules tend to cluster predominantly on top of the larger water patches of the first solvation layer instead of spreading evenly around the remainder of the protein surface. For CALB, this exposes the substrate-binding region of the enzyme to carbon dioxide, possibly facilitating diffusion of nonpolar substrates into the catalytic funnel. Therefore, by means of microheterogeneous solvation, enhanced accessibility of hydrophobic substrates to the active site can be achieved, while preserving the functional structure of the enzyme. Our results provide a molecular picture on the nature of the stability of proteins in nonaqueous media.

The importance of landscape structure for seed dispersal in rain forest fragments

Questions What are the main features of the seed rain in a fragmented Atlantic forest landscape? Can seed rain species attributes (life form, dispersal mode, successional status) relate to the spatial arrangement (size and number of fragments, edge density and presence of corridor) of forest fragments in the landscape? How does the rain forest landscape structure affect the seed rain? Location Atlantic rainforest, Sao Paulo State, Southeastern Brazil. Methods Seed rain samples were collected monthly throughout 1yr, counted, identified and classified according to species dispersal mode, successional status and life form. Seed rain composition was compared with woody species near the seed traps. Relationships between seed rain composition and landscape spatial arrangement (fragment area, presence of corridor, number of fragments in the surroundings, proximity of fragments, and edge density) were tested using canonical correspondence analysis (CCA). Results We collected 20142 seeds belonging to 115 taxa, most of them early successional and anemochorous trees. In general, the seed rain had a species composition distinct from that of the nearby forest tree community. Small isolated fragments contained more seeds, mainly of anemochorous, epiphytic and early-successional species; large fragments showed higher association with zoochorous and late-successional species compared to small fragments. The CCA significantly distinguished the species dispersal mode according to fragment size and isolation, anemochorous species being associated to small and isolated fragments, and zoochorous species to larger areas and fragment aggregation. Nevertheless, a gradient driven by proximity (PROX) and edge density (ED) segregated lianas (in the positive extremity), early successional and epiphyte species (in the negative end); large fragments were positively associated to PROX and ED. Conclusions The results highlight the importance of the size and spatial arrangement of forest patches to promote habitat connectivity and improve the flux of animal-dispersed seeds. Landscape structure controls seed fluxes and affects plant dispersal capacity, potentially influencing the composition and structure of forest fragments. The seed rain composition may be used to assess the effects of landscape spatial structure on plant assemblages, and provide relevant information for biodiversity conservation.

Comparing the establishment of an invasive and an endemic palm species in the Atlantic rainforest

Background: Biological invasions are one of the major causes of biodiversity loss, yet remain rather understudied in tropical environments. The Australian palm tree Archontophoenix cunninghamiana was introduced into Brazil for ornamental purposes, but has become an invasive species in urban and suburban forest patches. The substitution of A. cunninghamiana by the native palm Euterpe edulis has been proposed as a management action. Aims: We aimed to evaluate the regeneration potential of these two palm species in an Atlantic forest remnant in south-eastern Brazil where both species occur. Methods: We compared seedling establishment and seed longevity of both species through seed sowing, and also measured the contribution of A. cunninghamiana to the local seed rain and seed bank. Results: Nearly half of the non-anemochoric diaspores collected from the seed rain belonged to A. cunninghamiana, which represented a high propagule pressure in the community. The distribution of the alien palm seeds in the seed rain correlated with the distribution of nearby young and adult individuals inside the forest. Neither A. cunninghamiana nor E. edulis appeared to have a persistent seed bank in a burial experiment; seedling survival experiments suggested a much better performance for A. cunninghamiana, which had a survival rate of ca. 30% compared with a rate of only 3.5% for E. edulis. Conclusions: The results suggest a higher regeneration capacity for the alien palm over the native species when co-occurring in a forest fragment. Management actions are thus proposed to reduce a potential biological invasion process.

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.

Cross-taxon congruence of alpha and beta diversity among five leaf litter arthropod groups in Colombia

In this study alpha and beta diversity patterns of five leaf litter arthropod groups (ants, predatory ants, oribatid mites, spiders and other arachnids) were described and compared in 39 sampling patches of a transformed landscape in southwestern Colombia, that represented five vegetation types: secondary forest, riparian forest, giant bamboo forest, pasture and sugarcane crop. It was also assessed whether some taxa could be used as diversity surrogates. A total of 6,765 individuals grouped in 290 morphospecies were collected. Species richness in all groups was lower in highly transformed vegetation types (pasture, sugarcane crop) than in native ones (forests). In contrast, there were no clear tendencies of beta diversity among vegetation types. Considering sampling patches, 0.1-42% of the variation in alpha diversity of one taxonomic group could be explained from the alpha diversity of another, and 0.2-33% of the variation of beta diversity of a given taxon was explained by that in other groups. Contrary to recent findings, we concluded that patterns of alpha diversity are more congruent than patterns of beta diversity. This fact could be attributed to a sampling effect that promotes congruence in alpha diversity and to a lack of a clear regional ecological gradient that could promote congruent patterns of beta diversity. We did not find evidence for an ideal diversity surrogate although diversity patterns of predatory ants had the greatest congruencies. These results support earlier multi-taxon evaluations in that conservation planning should not be based on only one leaf litter arthropod group.

Effective properties evaluation for smart composite materials

The purpose of this article is to present a method which consists in the development of unit cell numerical models for smart composite materials with piezoelectric fibers made of PZT embedded in a non-piezoelectric matrix (epoxy resin). This method evaluates a globally homogeneous medium equivalent to the original composite, using a representative volume element (RVE). The suitable boundary conditions allow the simulation of all modes of the overall deformation arising from any arbitrary combination of mechanical and electrical loading. In the first instance, the unit cell is applied to predict the effective material coefficients of the transversely isotropic piezoelectric composite with circular cross section fibers. The numerical results are compared to other methods reported in the literature and also to results previously published, in order to evaluate the method proposal. In the second step, the method is applied to calculate the equivalent properties for smart composite materials with square cross section fibers. Results of comparison between different combinations of circular and square fiber geometries, observing the influence of the boundary conditions and arrangements are presented.

Effect of parametric uncertainties on the performance of a piezoelectric energy harvesting device

The use of piezoelectric materials for the development of electromechanical devices for the harvesting or scavenging of ambient vibrations has been extensively studied over the last decade. The energy conversion from mechanical (vibratory) to electrical energy is provided by the electromechanical coupling between mechanical strains/stresses and electric charges/voltages in the piezoelectric material. The majority of the studies found in the open literature present a tip-mass cantilever piezoelectric device tuned on the operating frequency. Although recent results show that these devices can be quite effective for harvesting small amounts of electrical energy, little has been published on the robustness of these devices or on the effect of parametric uncertainties on the energy harvested. This work focuses on a cantilever plate with bonded piezoelectric patches and a tip-mass serving as an energy harvesting device. The rectifier and storage electric circuit was replaced by a resistive circuit (R). In addition, an alternative to improve the harvesting performance by adding an inductance in series to the harvesting circuit, thus leading to a resonant circuit (RL), is considered. A coupled finite element model leading to mechanical (displacements) and electrical (charges at electrodes) degrees of freedom is considered. An analysis of the effect of parametric uncertainties of the device on the electric output is performed. Piezoelectric and dielectric constants of the piezoelectric active layers and electric circuit equivalent inductance are considered as stochastic parameters. Mean and confidence intervals of the electric output are evaluated.