Cana Brava Research Articles

Pre- to post-collisional Ediacaran magmatism in the western portion of the Borborema Province (NE Brazil): Petrogenesis and insights for the crustal evolution during the Brasiliano Orogeny

The Central subprovince of the Borborema Province (NE Brazil) is characterized by a voluminous and diversified late-Neoproterozoic magmatism (ca. 640 to 540 Ma) that resulted in plutons with significant correlations among their U-Pb ages, TDM Nd model ages, εNd(t) values, geochemical signatures, and petrology, evidencing the importance of their study to the understanding of the Brasiliano/ Pan-African evolution in the region. The Jardim Mirim Suite (630 Ma) comprises magmatic-epidote bearing calc-alkaline to slightly high-K calc-alkaline tonalitic and granodioritic rocks characterized by εNd(t) values ranging from −3.0 to 0.8 and Mesoproterozoic TDM Nd model ages (1.4 to 1.1 Ga). The Colina do Horto Pluton (594 Ma) is composed of shoshonitic monzodiorites, monzonites, and granites that exhibit, in general, strongly negative εNd(t) values (−18.2 to −16.5) and Paleoproterozoic TDM Nd model ages (1.9 to 2.1 Ga). The Cana Brava (572 Ma) and Poço plutons consist of alkaline ferroan granites composed of Fe-rich mafic minerals and characterized by strongly negative εNd(t) values (−15.3 to −14.8, respectively), Paleoproterozoic TDM Nd model ages (2.0 Ga), and geochemical signatures similar to high Ba-Sr granites. The study of these plutonic bodies indicates three main magmatic events, developed in pre-collisional (probably associated with the closure of a narrow oceanic basin) to post-collisional (associated with lithospheric delamination process) settings. The contrasting features of the studied rocks reflects changes in magmatic sources in the region. Whereas the origin of pre-collisional magmas is associated with the mixing of juvenile Brasiliano source with Cariris Velhos rocks (ca. 1000–870 Tonian crustal rocks from the Borborema Province), post-collisional rocks were generated by underplating-driven partial melting of a mafic to felsic Paleoproterozoic crust.

Functional distance does not predict interspecific synchrony, but functional diversity directly affects community stability

Several studies attempt to understand the mechanisms underlying compensatory and synchronous dynamics, and how these mechanisms relate to community stability. For this purpose, the use of functional traits, in theory, would allow for a direct evaluation of whether functional similarity generates compensatory dynamics or interspecific synchrony. Likewise, a trait-based approach is also needed to evaluate the effect of functional biodiversity on community stability. Using phytoplankton data from the Cana Brava Reservoir (Goiás State, Brazil), we tested whether interspecific synchrony depends on functional distance and whether variability in total abundance depends on community synchrony and functional diversity. We did not find a significant relationship between interspecific synchrony and functional distance. However, we found a predominance of positive correlations between pairs of species and a strong negative relationship between functional diversity and community variability. Our results suggest that interspecific synchrony cannot be reliably predicted by functional distance. Given the predominance of positive synchrony, we indirectly infer that environmental variations similarly controlled the dynamics of most species. Our findings also highlight the stabilizing role of functional diversity.

Niche measures and growth rate do not predict interspecific variation in spatial synchrony of phytoplankton

Spatial synchrony occurs when local populations exhibit correlated dynamics over time. Recent studies, both experimental and observational, have indicated that the magnitude of spatial synchrony, in cross-species analyses, is correlated with the level of specialization. In theory, specialist species would exhibit higher levels of synchrony than generalist species because they would be more sensitive to environmental variations. In addition, according to simulation studies, species with high growth rates should have more synchronized dynamics. In this study, we tested these hypotheses using datasets (phytoplankton populations and environmental variables) obtained in the Cana Brava Reservoir (State of Goias, Brazil). We used a multiple regression model to test whether the average level of spatial synchrony was correlated with variables that indicate environmental specialization and population growth rate. In general, the average values of spatial synchrony were low, indicating the predominance of local factors in controlling population dynamics. We found no significant relationship between synchrony and our explanatory variables. To assess the generality of correlates of spatial synchrony, we suggest that future studies should focus on a common same set of explanatory variables.

A não resposta no Atlas Linguístico do Português em Áreas Indígenas (ALiPAI): um olhar sobre o campo semântico corpo humano

Este artigo consiste em um estudo sobre a não resposta no corpus do projeto Atlas Linguísticodo Português em Áreas Indígenas (ALiPAI), a partir das questões 89 (pálpebras) e 117 (rótula)do campo semântico Corpo humano do Questionário Semântico-Lexical (QSL) aplicadopelos pesquisadores do projeto. Os dados foram coletados in loco nas Terras IndígenasTrocará, Nova Jacundá e Sororó, no estado do Pará, e Cana Brava, no estado do Maranhão.Os resultados apresentam alto índice de não resposta para ambas as questões consideradas;mostram que os dados analisados são tímidos para explicar a não resposta, mas podem indicaro perfil do colaborador (no que tange a fatores sociais como idade e escolaridade) como pontoimportante quando do seu entendimento e refletem a ocorrência da não resposta relacionando-aà aspectos referentes à extensão do QSL e à ordem de aplicação dos questionários, à históriae à cultura dos povos indígenas participantes desta pesquisa e ao conhecimento de mundo quepossuem. Além disso, a não resposta estabelece-se como um tópico de reflexão metodológicano que tange a instrumentos de coleta de dados, à ampliação de variáveis e de colaboradoresna sua compreensão no âmbito da pesquisa geossociolinguística.

Study on Mercury Methylation in the Amazonian Rivers in Flooded Areas for Hydroelectric Use

This study aimed to estimate in laboratory the temporal production of methylmercury during the filling of reservoirs of hydropower plants and to correlate it to the ecosystem of different locations in northern Brazil: Jirau hydropower plant in the Madeira River in the state of Rondonia (white waters—under construction), Cana Brava hydropower plant in the Tocantins River in the state of Goias (clear waters—completed), and the Negro River in the Amazon (black waters—comparative). After collecting water, soil, and sediment samples in the regions mentioned, a microcosm was created to reproduce the conditions close to those found in nature. Water/soil/Hg0/Hg2+ and water/sediment/Hg0/Hg2+ were added to glass recipients. Next, methylmercury concentration was monitored by atomic fluorescence spectrometry, total organic carbon by TOC 5000A, and physical and chemical parameters such as pH, redox potential, and dissolved oxygen, for 25 days. The results obtained allow concluding that organic matter plays an important role, providing excess methyl groups to react with inorganic Hg and form organic Hg. The Negro River, which has higher contents of organic matter in its soil, water, and sediment, presented higher potential of mercury methylation in both experiments performed, followed by rivers Madeira and Tocantins.

O amianto e seus impactos no município de Minaçu

A extração mineral do amianto é a principal fonte econômica, do município de Minaçu, localizado na região norte do estado de Goiás, que desde a sua criação desenvolveu-se em função da Mina Cana Brava. Atualmente, em decorrência da declaração de inconstitucionalidade do artigo 2º da Lei federal 9.055/1995 que permitia a extração, a industrialização, a comercialização e a distribuição do amianto na variedade crisotila no país, decisão de 29 de novembro de 2017 pelo Supremo Tribunal Federal, o município vive em ambiente de incertezas quanto ao futuro. O objetivo deste artigo é promover uma reflexão sobre a dependência econômica do município e do seu posicionamento, ao lado da mineradora SAMA, do “uso controlado do amianto”, deixando evidente que os argumentos econômicos e mercadológicos prevalecerão, diante do desenvolvimento de diversos estudos científicos em várias partes do mundo que demonstram os males à saúde humana.
 
 Abstract
 
 THE EARTH-FLAX AND ITS IMPACTS IN THE CITY OF MINAÇU
 
 The mineral extraction of Earth-flax is the main economic source of the city of Minaçu, located in the north of the State of Goiás, since its foundation has developed thanks to the Cana Brava mine. Nowadays, the city is uncertain about the future, due to the declaration of unconstitutionality of the Second article of the federal law 9.055/1995 which permitted the extraction, industrialization, commercialization and the distribution of earth-flax in the variety chrysotile in the country, decision dated of the day 29, November of 2017 from the Federal Court of Justice. This article objective to promote the discussion about the economic dependence of the city and it positioning, facing to the mining SAMA, defending “the controlled use of Earth-flax”, making clear that the economic and market reasons are more important, face to the development of multiple scientific studies in different places around the world showing the malfunctions to the human health.

Isotopic constraints on contamination processes in the Tonian Goiás Stratiform Complex

The Tonian Goiás Stratiform Complex (TGSC, Goiás, central Brazil), is one of the largest mafic-ultramafic layered complexes in the world, emplaced during the geotectonic events that led to the Gondwana accretion. In this study, we present trace elements and in-situ U/Pb-Lu-Hf analyses of zircons and 87Sr/86Sr ratios of plagioclases from anorthosites and gabbros of the TGSC.Although formed by three isolated bodies (Cana Brava, Niquelândia and Barro Alto), and characterized by a Lower and Upper Sequence (LS and US), our new U/Pb zircon data confirm recent geochemical, geochronological, and structural evidences that the TGSC has originated from a single intrusive body in the Neoproterozoic.New Hf and Sr isotope ratios construe a complex contamination history for the TGSC, with different geochemical signatures in the two sequences. The low Hf and high Sr isotope ratios of the Lower Sequence (εHf(t) from −4.2 down to −27.5; 87Sr/86Sr = 0.706605–0.729226), suggest the presence of a crustal component and are consistent with contamination from meta-pelitic and calc-silicate rocks found as xenoliths within the Sequence. The more radiogenic Hf isotope ratios and low Sr isotope composition of the Upper Sequence (εHf(t) from 11.3 down to −8.4; 87Sr/86Sr = 0.702368–0.702452), suggest a contamination from mantle-derived metabasalts in agreement with the occurrences of amphibolite xenoliths in the US stratigraphy. The differential contamination of the two sequences is explained by the intrusion of the TGSC in a stratified crust dominated by metasedimentary rocks in its deeper part and metavolcanics at shallower levels. Moreover, the differential thermal gradient in the two crystallizing sequences might have contributed to the preservation and recrystallization of inherited zircon grains in the US and total dissolution or magmatic overgrowth of the LS zircons via melt/rock reaction processes.

Evaluation of the physical and mechanical properties of caña brava (Arundo donax) reinforced panels

Introduction: The use of composites made of vegetable origin materials has gained importance in some areas of engineering, mainly in civil construction. Objective: The objective of this paper is to analyze the physical and mechanical behavior of panels made with cana brava fibers and vegetal resin. Methodology: For the elaboration of the panels, the fibers were extracted using a mechanical crusher. The fibers were treated with a sodium hydroxide solution. The effect of the chemical treatment was evaluated by scanning electron microscopy. The roughness of the fibers was determined using the atomic force microscopy technique. For the manufacture of the composite, a compression method was used. The physical characterization of the panels was focused on the evaluation of the effective absorption, density, and percentage of swelling. To evaluate the mechanical behavior, static bending and mechanical fracture tests were performed. To evaluate the degradation of the material with the temperature, a thermogravimetric test was executed. Results: From the results, it is possible to verify that panels made with cana brava fibers and vegetal resin can present an increase in their dimensional stability when compared to panels made with Guadua Angustifolia Kunth fibers and show higher values of strength and stiffness than panels elaborated with coconut and bamboo fibers. Conclusions: Considering that cana brava is an invasive plant, its application as reinforcement of composite panels is a viable option to promote the development and application of new materials in civil construction.

New U-Pb SHRIMP-II zircon intrusion ages of the Cana Brava and Barro Alto layered complexes, central Brazil: constraints on the genesis and evolution of the Tonian Goias Stratiform Complex

The Cana Brava, Niquelândia and Barro Alto complexes (Goiás, central Brazil) are three of the largest mafic-ultramafic layered complexes in the world and their origin has been a matter of debate for several decades. One hypothesis suggests that Niquelândia and Barro Alto were both formed by two distinct igneous events at 1.3Ga and at 790Ma and were later overlapped during tectonic exhumation at 650Ma; according to this reconstruction Cana Brava belongs to the youngest intrusion at 790Ma. A second hypothesis suggests that the three complexes formed during the same event. Here we provide new U-Pb SHRIMP-II zircon ages for the Cana Brava and Barro Alto complexes, constraining their intrusion age to the Neoproterozoic (between 770 and 800Ma), coeval with Niquelândia. A review of new and literature ages indicate that these complexes formed during a single igneous event and were not modified by regional metamorphism. We propose that the complexes represent fragments of the larger Tonian Goiás Stratiform Complex, which was likely part of a back-arc environment connected to the formation of the Goiás Magmatic Arc at about 790Ma, later disrupted and accreted to the São Francisco craton.

DETERMINACIÓN DE TARIFAS ÓPTIMAS PARA GENERACIÓN DE ELECTRICIDAD AL SISTEMA INTERCONECTADO A PARTIR DE RESIDUOS DE BIOMASA, UTILIZANDO EL SOFTWARE RETSCREEN Y APLICATIVOS DEL PROYECTO BEFS RAPID APPRAISAL DE NACIONES UNIDAS PARA LA AGRICULTURA Y LA ALIMENTACIÓN (FAO)

El Perú cuenta con una extensión de 82‘369, 713 hectáreas de aptitud forestal, 7’600,000 con capacidad para los cultivos agrícolas y un potencial de biomasa para la producción de energía estimado en 272 millones de toneladas métricas anuales [2]. Para fines energéticos, existen cuatro categorías: plantaciones bioenergéticas, residuos agrícolas, bostas de ganado y residuos sólidos urbanos. La tecnología de gasificación sería la más conveniente para los fines del estudio. Evaluando el potencial teórico de generación eléctrica con biomasa que se pueda interconectar a la red, se obtuvo como resultado dos fuentes: arroz (Cajamarca, Lambayeque y Piura) y caña de azúcar (Lambayeque, Piura y Lima). Con el fin de proyectar la demanda, se tomó como guía el Plan Referencial de Electricidad 2008 - 2017. Los supuestos considerados son los siguientes: Escenario de Crecimiento Medio: Tasa de crecimiento Anual 7.55%; Escenario de Crecimiento Optimista: Tasa de crecimiento Anual 8.7%; Escenario de Crecimiento Conservador: Tasa de crecimiento Anual 6.36%. Para determinar el Potencial Energético por Regiones desagregado por proyectos, se utilizó el aplicativo FAO BEFS Rapid Apraisal y el software RETScreen. De los 17 proyectos analizados, las herramientas calcularon que solamente cuatro podrían ser parte de una cartera de proyectos viables: Agroindustria Paramonga, Agroindustria Caña Brava, Relleno Sanitario Huaycoloro y Gran Mercado Mayorista de Lima (Santa Anita). La principal barrera que se ha encontrado es que las tarifas tope que ha establecido el Gobierno en las últimas subastas de proyectos para generación con energías renovables, no llega siquiera a estar próxima a las tarifas optimas analizadas en este estudio. Palabras clave.- Energía renovable, Biomasa, Bioenergía, Proyectos de biomasa. ABSTRACTPeru has a surface of 82’369,713 hectares of forestry suitability, 7’600,000 hectares with agriculture farming capacity and a biomass potential for energy generation estimated in 272 million annual metric tons [2]. For energy generation scope, there are four categories: bioenergy crops, agriculture waste, livestock waste and urban solid waste. Gasification technology would be more convenient for the scope of the study. Assessing the theoretical potential of energy generation with biomass for grid connection, the result was the identification of two sources: Rice (Cajamarca, Lambayeque and Piura) and sugar cane (Lambayeque, Piura and Lima).With the aim to design the energy demand, the Electricity Referential Plan 2008 – 2017 was used as base document. The considered assumptions were the following: Medium growth scenario: Annual growth rate 7.55%; Optimist growth scenario: Annual growth rate 8.7%; Conservative growth scenario: Annual growth rate 6.36%. In order to determine the energy potential by regions disaggregated by projects, it was used the application FAO BEFS Rapid Appraisal and the software RETScreen. From the 17 analyzed projects, the tools calculated that only four could be part of a viable Project portfolio: Agroindustria Paramonga, Agroindustria Caña Brava, Huaycoloro Landfill and Gran Mercado Mayorista de Lima (Santa Anita). The main barrier found is that the top tariffs established by the Government in the last bids are even near to the optimum tariffs analyzed in this study. Keywords.- Renewable energy, Biomass, Bioenergy, Biomass projects.

The growth and contamination mechanism of the Cana Brava layered mafic-ultramafic complex: new field and geochemical evidences

The Cana Brava complex is the northernmost of three layered complexes outcropping in the Goias state (central Brasil). New field and geochemical evidences suggest that Cana Brava underwent hyper- to subsolidus deformation during its growth, acquiring a high-temperature foliation that is generally interpreted as the result of a granulite-facies metamorphic event. The increase along the stratigraphy of the incompatible elements abundances (LREE, Rb, Ba) and of the Sr isotopic composition, coupled with a decrease in eNd(790), indicate that the complex was contaminated by the embedded xenoliths from the Palmeiropolis Sequence. The geochemical data suggest that the contamination occurred along the entire magma column during the crystallization of the Upper Mafic Zone, with in situ variations determined by the abundance and composition of the xenoliths. These features of the Cana Brava complex point to an extremely similarity with the Lower Sequence of the most known Niquelândia intrusion (the central of the three complexes). This, together with the evidences that the two complexes have the same age (c.a. 790 Ma) and their thickness and units decrease northwards suggests that Cana Brava and Niquelândia are part of a single giant Brasilia body grown through several melt impulses.

U-Pb zircon SHRIMP data from the Cana Bravalayered complex: new constraints for themafic-ultramafic intrusions of Northern Goiás,Brazil

Abstract The Cana Brava Complex is the northernmostand least well known layered intrusion of a discontinuousbelt of mafic-ultramafic massifs within the Brasilia Belt,which also comprises theNiquelândia and Barro Alto complexes.Available geochronological data from a range oftechniques (K/Ar, Ar/Ar, Rb/Sr, Sm/Nd and U/Pb) providea range of possible ages (time span from 3.9 Ga to 450 Ma),hence a precise and reliable age for the Cana Brava Complexis still lacking. Also, preliminary isotopic and geochemicaldata of the Cana Brava Complex suggest a significantcrustal contamination, which could have affectedbulk-rock Sr and Nd systematics resulting in meaninglessage determinations. In this paper, we present new U-PbSHRIMP zircon analyses from four samples of differentunits of the Cana Brava Complexwhich suggest that the intrusionoccurred during the Neoproterozoic, between 800and 780 Ma, i.e. at the same age ofNiquelândia. Discordantolder 206Pb/238U ages are provided by inherited zircons,and match the age of the metamorphism of the embeddingPalmeirópolis Sequence.

Neoproterozoic Cana Brava chrysotile deposit (Goiás, Brazil): Geology and geochemistry of chrysotile vein formation

The Cana Brava chrysotile asbestos deposit of Goiás, Brazil, contains approximately 150Mt of ore with an average of 3.5wt.% of cross-fiber chrysotile and lies in the differentiated, mafic–ultramafic Neoproterozoic Cana Brava complex. This complex was formed at approximately 0.79Ga and metamorphosed at 0.77 to 0.76 and 0.63Ga. The 0.77 to 0.76Ga metamorphic event was a high-grade one that transformed the mafic and ultramafic rocks into meta-peridotites and meta-pyroxenites. The low-grade 0.63Ga metamorphism allowed the formation of black, red and brown serpentinite, graphitic, magnesite-rich talc serpentinite, and rodingite, which became folded and foliated. At the end of the 0.63Ga metamorphism, black serpentinites were oxidized to form red serpentinites, the main type of serpentinite that outcrops today at the Cana Brava mineralized region. Post-metamorphic fluids reactivated the process of serpentinization, thereby generating massive green serpentinite from the red. Green formed on the most fractured zones, and double red and green reaction rims formed on the sides of the veins located outside the green serpentinite zones. This process did not cause significant variation in the volume of the rocks and resulted in a strongly reducing system thanks to the loss of Fe2O3 and iron and the subsequent crystallization of magnetite within veinlets and altered rocks. Low angle shear, developed under brittle conditions, caused hydraulic fracturing and the generation of oversaturated, oxidizing fluids that crystallized the cross-fiber chrysotile inside open fractures. Very densely fractured zones with fractures filled with cross-fiber chrysotile constitute the ore that is mined at present.

A ENCHENTE DE 2010 EM UNIÃO DOS PALMARES - AL: OS IMPACTOS SÓCIOAMBIENTAIS DAS ÁREAS RIBEIRINHAS

The aim of this paper was to analyze the impacts that social and environmental impacts caused to areas border the Rio Mundaú in Uniao dos Palmares-AL after the flood of 2010. The areas most affected were the ones that are on the river and its tributary creek Mundaú Cana Brava, which its population had significant amount riverside people. The methodology we used was the literature and observation of the affected areas, through visits in locus before, during and after the flood. What happened was a great flood that devastated these riparian areas, leaving many people homeless and displaced, destroying the structural and dreams of people. Besides the change in the social life of the people and the environment, there were also significant changes in the landscape of the riverside areas of Rio Mundaú. The river banks have been changed completely, which was once occupied by houses and a heavy flow of residents currently see only debris, scrub and isolated areas, completely abandoned by their former inhabitants and the government. By being abandoned for the risk of invasions of homeless people or even old residents, who have no prospect of achieving better houses. The flood was a watershed in the recent history of Uniao dos Palmares, when it comes to infrastructure and development of new neighborhoods, because even with the creation of precarious housing and structural development of a breakthrough, it provided an economic development for the city and some improvements for the population.

Utilização de elipsoide de anisotropia variográfica como indicador cinemático em maciços rochosos fragmentados por falhas - o exemplo do depósito de asbestos crisotila cana brava (Minaçu, GO)

The parameters of a variogram depend on which direction it is calculated, such as the ellipsoid of variographic anisotropy, whose axes indicate the directions of higher, medium and lower continuity of the variable used to calculate the variogram. Consequently, the ellipsoid can be used as a kinematic indicator, since the anisotropy ellipsoids of blocks of the same rock massif or mineralized body will be rotated if the blocks are also rotated. The chrysotile ore body of the Cana Brava Asbestos deposit is composed of 13 blocks separated by faults. Comparing the ellipsoids of variographic anisotropy of the variable amount of chrysotile in these 13 blocks, it was observed that, although they are displaced in relation to each other, in most cases this displacement was not caused by rotation. As a result, it was possible to group some blocks together and use only six ellipsoids and their respective variograms to estimate the amount of chrysotile in the deposit.

Neoproterozoic age of the Niquelândia Complex, central Brazil: Further ID-TIMS U–Pb and Sm–Nd isotopic evidence

The age and tectonic significance of the Barro Alto, Niquelândia, and Cana Brava layered mafic–ultramafic complexes in Goiás have been a matter of debate and controversy. In many models, they have been considered representative of Paleoproterozoic intrusions metamorphosed in the Neoproterozoic, at approximately 0.79–0.76 Ga. Recent SHRIMP U–Pb data for dioritic rocks of the Niquelândia Complex, however, suggest that they crystallized around 0.80 Ga. Petrologic and field data suggest that these dioritic rocks are late-stage crystallization phases representing intense contamination with sialic country rocks rather than much younger intrusions into the lower layered series of the complex. In this study, igneous zircon grains from a cumulate websterite belonging to the upper part of the lower series of the Niquelândia Complex are investigated by the ID-TIMS U–Pb method and yield an age of 799±6 Ma. Sm–Nd isotopic data for the same sample reveal strong contamination with older crust ( ε Nd( T) of −6.5 and T DM of 1.88 Ga). Additional Sm–Nd data for dioritic and late-stage granitic rocks of the complex have produced a whole-rock isochron with an age of 759±65 Ma and ε Nd( T) of −8.8. The data confirm that the upper mafic unit of the lower series of the Niquelândia Complex is Neoproterozoic and that the original magma is contaminated with Meso- to Paleoproterozoic crust. The layered complex may have been intruded into a continental rift developed at the western limb of the São Francisco-Congo continent, coeval with the development of the Goiás Magmatic Arc to the west.

An experimental study of bamboo ants in western Amazonia

Numerous ant taxa naturally inhabit stems of live and dead Guadua bamboo (Bambusoidea, Poaceae) in western Amazonia. In an experiment at the onset of the wet season in Peru’s Manu National Park, we augmented potential nest sites in stems of live bamboo, dead bamboo and dead cana brava (Gynerium sagittatum, another woody grass) at five stations within each of ten bamboo patches and ten control areas outside those patches. Each experimental stem possessed three vacant and available internodes, pre-drilled with, respectively, large, small and linear holes, mimicking the range of forms of surveyed natural entrances. After 24 days, approximately 13% of 798 available internodes had been colonized, the majority by fragments of existing colonies. Ignoring entrance type, which did not affect colonization for any species or species group, and censoring non-independent internodes of the same stem, we used individual stems as independent sample units in other tests. One specialist in live bamboo (Camponotus longipilis), and a likely specialist in dead bamboo (Camponotus depressus), were identified based on overrepresentation in bamboo habitat and disproportionate occurrence in live or dead bamboo stems. A third species, Camponotus (Pseudocolobopsis sp.) was more abundant in bamboo areas but colonized both dead bamboo and dead cana. Relatively high abundance of standing dead stems in Guadua forests may account for the presence of a dead stem specialist. The experiment missed detecting specialization in one live culm specialist (Camponotus mirabilis), likely due to its failure to simulate conditions required for the species’ unique modes of colony establishment and spread into new culms. Most opportunistic stem nesters colonized dead bamboo at significantly greater rates than dead cana, but were either equally well represented in bamboo and control areas, or underrepresented in bamboo habitat. Given low colonization rates overall, underrepresentation in bamboo cannot be attributed to competition from bamboo specialists for nesting space. Rather, it may be due to combined effects of seasonal flooding of bamboo habitat, and greater importance of food limitation, relative to nest site limitation, in that habitat.

Uma nova espécie do gênero Atractus wagler, 1928 (Colubridae: Dipsadinae) do Cerrado do Brasil Central

Atractus edioi sp. n. é descrita para a região da usina hidrelétrica Cana Brava, localizada no extremo norte do Estado de Goiás, município de Minaçu, dentro dos limites do ecossistema Cerrado no Brasil Central. Esta espécie se distingue das outras espécies de Atractus pela combinação da fórmula temporal 1+1, 5 supralabiais, supralabiais 2-3 margeando a órbita, 6 infralabiais, infralabiais 1-3 em contato com as gulares anteriores, 15 escamas nas fileiras dorsais e um padrão de coloração dorsal de manchas escuras sobre um fundo marrom-claro.

The Biopersistence of Brazilian Chrysotile Asbestos Following Inhalation

With the initial understanding of the relationship of asbestos to disease, little information was available on whether the two different groups of minerals that are called asbestos were of similar or different potency in causing disease. Asbestos was often described as a durable fiber that if inhaled would remain in the lung and cause disease. It has been only more recently, with the development of a standardized protocol for evaluating the biopersistence of mineral fibers in the lung, that the clearance kinetics of the serpentine chrysotile have been shown to be dramatically different from those of amphibole asbestos, with chrysotile clearing rapidly from the lung. In addition, recent epidemiology studies also differentiate chrysotile from amphibole asbestos. The biopersistence studies mentioned have indicated that chrysotile from Canada and California clear rapidly from the lung once inhaled. However, variations in chrysotile mineralogy have been reported depending upon the region. This is most likely associated with variations in the forces which created the chrysotile fibers centuries ago. In the present study, the dynamics and rate of clearance of chrysotile from the Cana Brava mine in central Brazil was evaluated in a comparable inhalation biopersistence study in the rat. For synthetic vitreous fibers, the biopersistence of the fibers longer than 20 μ m has been found to be directly related to their potential to cause disease. This study was designed to determine lung clearance (biopersistence) and translocation and distribution within the lung. As the long fibers have been shown to have the greatest potential for pathogenicity, the chrysotile samples were specifically chosen to have more than 450 fibers/cm3 longer than 20 μ m in length present in the exposure aerosol. For the fiber clearance study (lung digestions), at 1 day, 2 days, 7 days, 2 wk, 1 mo, 3 mo, 6 mo, and 12 mo following a 5-day (6 h/day) inhalation exposure, the lungs from groups of animals were digested by low-temperature plasma ashing and subsequently analyzed by transmission electron microscopy (at the GSA Corp.) for total chrysotile fiber number in the lungs and chrysotile fiber size (length and diameter) distribution in the lungs. This lung digestion procedure digests the entire lung with no possibility of identifying where in the lung the fibers are located. A fiber distribution study (with confocal microscopy) was included in order to identify where in the lung the fibers were located. At 2 days, 2 wk, 3 mo, 6 mo, and 12 mo postexposure, the lungs from groups of animals were analyzed by confocal microscopy to determine the anatomic fate, orientation, and distribution of the retained chrysotile fibrils deposited on airways and those fibers translocated to the broncho-associated lymphoid tissue (BALT) subjacent to bronchioles in rat lungs. While the translocation of fibers to the BALT and lymphatic tissue is considered important as in cases of human's with asbestos-related disease, there has been no report in the literature of pathological changes in the BALT and lymphatic tissue stemming from asbestos. Thus, if the fibers are removed to these tissues, they are effectively neutralized in the lung. Chrysotile was found to be rapidly removed from the lung. Fibers longer than 20 μ m were cleared with a half-time of 1.3 days, most likely by dissolution and breakage into shorter fibers. Shorter fibers were also rapidly cleared from the lung with fibers 5–20 μ m clearing even more rapidly (T1/2 = 2.4 days) than those < 5μ m in length (T1/2 weighted = 23. days). Breaking of the longer fibers would be expected to increase the short fiber pool and therefore could account for this difference in clearance rates. The short fibers were never found clumped together but appeared as separate, fine fibrils, occasionally unwound at one end. Short free fibers appeared in the corners of alveolar septa, and fibers or their fragments were found within alveolar macrophages. The same was true of fibers in lymphatics, as they appeared free or within phagocytic lymphocytes. These results support the evidence presented by that the chrysotile fibers are rapidly cleared from the lung in marked contrast to amphibole fibers which persist.

Modelagem gravimétrica do Complexo de Cana Brava e Seqüência De Palmeirópolis, GO

The tectonic set composed by the Mafic Ultramafic Complex of Cana Brava ( CCB ) and the Volcano Sedimentary Sequence of Palmeiropolis ( SVSP ) is located in the north of Goias state, at the limit with Tocantins state, in Central Brazil. The complex is part of Tocantins Province, that lies between the Amazonian and Sao Francisco cratons. The Bouguer anomaly of the set is a large positive feature, elongated NS like the geological boundaries of the bodies, and does not have any small anomalies that could characterize the two main bodies. 2 ½D and 3D gravity models were used to determine the anomalous mass distribution at depth. The residual Bouguer profiles, for 2 ½D model, were obtained by graphic adjusting of a line, and the Bouguer residual map, for 3D model, was obtained by polynomial fitting of order 1. At both models, the major thickness is at the center of the exposed body and the contacts between the studied geological units are dipping westward. The SVSP unit has a depth of 15.5km at the north and 4.5km at the south. The denser CCB unit is thicker at the south (6.5km) than at the north (4km). The 2 ½D model suggests a triangular vertical section for the body ( CCB+SVSP ) with a broader area close to the surface. Small residual positives east of the geological boundary can be modeled by a small buried body of CCB , disconnected of the main one.