The reflection effect in eclipsing binary systems

The weakest point in the modern models of eclipsing binary systems (EBS) is the treatment given to the effects of mutual irradiation. In this review, which does not have a similar one in the literature, I tried to collect all the work done on the irradiation problem until the middle of 1984, in order to make possible an evaluation of the present status of problem. Special emphasis is given to the applicability of the results to the analysis of EBS. The treatment given to the effect by the early studies as well as by practically all the modern models of EBS is described, and special attention is given to works analysing the problem using stellar model atmospheres. It turns out that the effect is more complex than suspected earlier, but that significant progress has been made recently.Review article.     

Environmental influences on the demersal fish assemblages in the Sepetiba Bay, Brazil

The structure of the demersal fish assemblage in Sepetiba Bay, southeast Brazil (22°54′–23°04′S, 43°34′–44°10′W) was described and related to environmental variables. A 3-yr long trawl survey (from July 1993 to June 1996) was conducted using a stratified random sampling strategy at 158 stations. One hundred and seven species of fishes in 80 genera and 44 families were identified. Gerreidae and Ariidae made up 30.5% and 28.6%, and 19.8% and 28.1% of the total number and weight, respectively. Sciaenidae, Engraulididae, Sparidae, and Carangidae were other prominent families. Three assemblages existed in the bay: one inhabited shallow, less saline and less transparent water in the inner zone (depth <5 m, transparency <2 m, salinity <30 psu, and slightly higher temperature); another in the outer zone with the opposite situation (depth >10 m, transparency >3 m, salinity >30 psu, and slightly lower temperature); and a third assemblage in the middle zone likely to prefer average values or show no clear preferences. Most species decreased in abundance over the 3-yr period of study. No seasonal change was detected in the assemblage structure, but many species were rare, indicating high spatial and temporal patchiness. Canonical correlation analyses were used to describe and compare the fish assemblages in the three different habitats. The outer zone had the greatest number of species recorded, lowest abundance, highest diversity and evenness, and was comprised mainly byCynossion leiarchus, Prionotus punctatus, Anchoa tricolor, Haemulon steindachneri, Diplectrum radiale, Etropus crossotus, andSphoeroides greeleyi; the inner zone had the lowest number of species recorded but the greatest number of species per sample, highest abundance, lowest diversity and evenness, being comprised mainly byDiapterus rhombeus, Genidens genidens, Cathrops spixii, Chloroschombrus chrysurus, Sciadeichthyes luniscutis, Cetengraulis edentulus, andArchorsargus rhomboidalis; while the third group had the lowest number of species per sample, being comprised by species widely distributed asGerres aprion, G. genidens, Gerres gula, andMicropogonias furnieri. Depth, followed by transparency and salinity, were the primary factors influencing assemblage distribution.     

Numerical Analysis of Space–Time Finite Element Formulations for Miscible Displacements

A finite element formulation is proposed to approximate a nonlinear system of partial differential equations, composed by an elliptic subsystem for the pressure–velocity and a transport equation (convection–diffusion) for the concentration, which models the incompressible miscible displacement of one fluid by another in a rigid porous media. The pressure is approximated by the classical Galerkin method and the velocity is calculated by a post-processing technique. Then, the concentration is obtained by a Galerkin/least-squares space–time (GLS/ST) finite element method. A numerical analysis is developed for the concentration approximation. Then, stability, convergence and numerical results are presented confirming the a priori error estimates.     

Genetic and metamorphic conditions constrained by fluid inclusions from Paleoproterozoic (c. 1.8 Ga) magnesite ore deposits, NE Brazil

Precambrian magnesite occurrences hosted by metadolomites from the Orós belt, Ceará, Brazil, are part of a greenschist–amphibolite, metavolcano-sedimentary terrain, dated at 1.8 Ga, cut by Meso- to Neoproterozoic Brasiliano granites and Neoproterozoic basic sills. These rocks were affected by a shear zone between 580 and 500 Ma. The magnesite-bearing marbles can be grouped as medium-grained (1–9 mm) at the Riacho Fundo ore deposit or sparry magnesite (1–15 cm) at the Cabeça de Negro ore deposit. The sparry magnesite shows textural characteristics related to original sedimentary structures. Both types of magnesite-bearing marbles contain aqueous and aqueous-carbonic fluid inclusions that yield homogenization temperatures between 170 and 370 °C. Applying a pressure correction, these temperatures are compatible with the evolution from greenschist to amphibolite facies metamorphic conditions, as described in previous work on the Orós region. It also agrees with data in specialized literature on the metamorphism of carbonate rocks. Fluid inclusion distribution, composition, and physical-chemical characteristics suggest temperature increase, probably related to metamorphism on these rocks. The medium-grained magnesite records partial contamination of CO₂-rich inclusions by relict carbonaceous material (bitumen, hydrocarbons?) that favors, but does not confirm, a syngenetic sedimentary origin and could have caused the lowering of CO₂ melting point in these inclusions. Therefore, though textural evidence points to a sedimentary-diagenetic model, fluid inclusions record conditions of a metamorphic event.     

Parasite findings in archeological remains: Diagnosis and interpretation

Paleoparasitology has contributed to resolving the debate about the peopling of the Americas and determining the antiquity of human parasite infection. Hookworm (Ancylostomidae) and whipworm (Trichuris trichiura) and other exclusive human intestinal parasites have been recorded in pre-Columbian America. These parasite species originated in pre-hominids and have accompanied humans across continents when people went out of Africa. However, for those human populations that crossed the Bering Land Bridge from Siberia to Alaska, cold climate conditions hampered parasite transmission. Alternative migration routes have been proposed to explain the presence of these parasites in pre-Columbian populations in the Americas. Other parasites were established in the New World long before humans entered the American continents.One such malady is Chagas disease. Chagas disease, caused by Trypanosoma cruzi, offers an example of how animals and humans have interacted in the past. Classical theory points to the origin and dispersion of human T. cruzi infection among Andean populations, starting with sedentary habits and animal domestication 6000 years ago. However, recent PCR results in mummified bodies outside the Andean region have challenged this theory. Pre-Columbian Brazilian mummies were found positive for T. cruzi infection, raising an alternative hypothesis on the antiquity of Chagas disease in the Americas. Paleoparasitology is a new tool to study past events, shedding light on human and other animal behavior, migration routes, diet, and other aspects of host–parasite environment evolution.     

Timing and role of the Maranhão River Thrust in the evolution of the Neoproterozoic Brasília Belt and Tocantins Province, central Brazil

A low-angle thrust fault places high-PT granulites (hangingwall) of the Internal Zone of the Neoproterozoic Brasília Belt (Tocantins Province, central Brazil) in contact with a lower-grade footwall (External Zone) comprised of nappes of distal passive margin- and back-arc basin-related supracrustals. The footwall units were emplaced at  750 Ma onto proximal sedimentary rocks (Paranoá Group) of the São Francisco paleo-continent passive margin. The high-PT belt is comprised of 645–630 Ma granulite-facies paragneiss and orthogneiss, and mafic–ultramafic complexes that include three major layered intrusions and metavolcanic rocks granulitized at  750 Ma. These complexes occur within lower-grade metasedimentary rocks in the hangingwall of the Maranhão River Thrust, which forms the Internal Zone–External Zone boundary fault to the north of the Pirineus Zone of High Strain. Detailed lithostructural studies carried out in Maranhão River Thrust hangingwall and footwall metasedimentary rocks between the Niquelândia and Barro Alto complexes, and also to the east of these, indicate the same lithotypes and Sm–Nd isotopic signatures, and the same D₁–D₂ progressive deformation and greenschist-facies metamorphism. Additionally, footwall metasedimentary rocks exclusively display a post-D₂ deformation indicating that the Maranhão River Thrust propagated through upper crustal rocks of the Paranoá Group relatively late during the tectonic evolution of the belt. Fault propagation was a consequence of intraplate underthrusting during granulite exhumation. The results allow for a better tectonic understanding of the Brasília Belt and the Tocantins Province, as well as explaining the presence of the Pirineus Zone of High Strain.     

Predictive Mapping of Prospectivity in the Gurupi Orogenic Gold Belt,North–Northeast Brazil: An Example of District-Scale Mineral System Approach to Exploration Targeting

The Gurupi Belt hosts a Paleoproterozoic gold province located in north–northeastern Brazil, at the borders of Pará and Maranhão states. It is considered to be an extension of the prolific West African Craton’s Birimian gold province into South America. Additionally, the belt has been the object of recent mineral exploration programs with significant resource discoveries. This study presents the results of predictive mapping using up-to-date mineral system concepts and recently finished regional-scale geological mapping, stream sediment and airborne geophysical surveys conducted by the Geological Survey of Brazil. We relate gold mineralization to an initially enriched crust, metamorphism, deep fluid pathways, structurally controlled damage zones and hydrothermal alteration. Prospective targets were generated using only regional public datasets and knowledge-driven targeting technique. This work did not incorporate any known gold deposits, yet it predicted the largest known deposits and their satellite targets. Besides, high prospective targets mapped almost 40% of known primary gold occurrences within 7% of the project area. This work allowed considerable search area reduction and identification of new target areas, thus collaborating on reducing costs, time and risk of mineral exploration. Results indicate that we achieved an efficient understanding of the geological processes related to the Gurupi Belt mineral system.     

Comparative agroenvironmental risks of pesticides in different cropping systems: application of the I-Phy indicator

The green revolution laid the foundations of modern agriculture, by using science and technology to produce more from same resources. The pesticides contributed to agricultural output in the last decades; however, their use has resulted in environmental pollution, health problems, soil and water contamination and negative impact on biota. The impacts of agricultural activities to the environment depended on the practices adopted during the production process. Measurement tools to assess the impacts of those practices are necessary to improve agricultural systems and must be evaluated in different ecosystems. Different soils, climates and crops impose many phytosanitary arrangements. This complex network and the fact that most of the indicators and measurement tools are developed for temperate climates makes it difficult to quantify the environmental impacts under subtropical regions. The I-Phy index is a predictive indicator that assesses the risks of pesticide usage in agriculture and identifies as to which practices generate the main environmental impacts of pesticides. The objective of this study was to test the suitability of the I-Phy index for subtropical conditions and, if suitable, compare the pesticide risk between two regions. Five crops were assessed under three different cropping systems: no-tillage, minimal tillage and conventional tillage. The I-Phy index was sensitive in both regions and capable of identifying that no-tillage generally presented risks of environmental pollution slightly lower than the other tillage systems. The results of I-Phy index showed that high environmental vulnerability of the fields and the numerous applications of active ingredients with high risks resulted in high risks of general contamination. The application of I-Phy on these two case studies showed the indicator can be useful as a support tool to farmers, research and extension institutions pursuing management practices with lower impact on the environment.     

Mapping the Brazilian Amazon fluvial sensitivity index to oil spills with Shuttle Radar Topography Mission (SRTM) data

It is important to understand the Solimões River seasonal hydrological cycle and its dynamics to support systematic environmental monitoring efforts in the Amazon region. These are essential to the contingency response to possible accidents in the existing oil transportation network. This study seeks to map the environmental sensitivity to oil spills in the surroundings of Coari city, Amazonas State (AM). A computational method was employed representing the seasonal inundation phenomenon fluctuations, together with data from the Digital Elevation Model generated by the Shuttle Radar Topography Mission. These were matched with Coari fluviometric time series information and a Japanese Earth Resources Satellite-1 (JERS-1 SAR) geo-referenced mosaic of the Global Rain Forest Mapping Project. In this context, a mathematical morphology technique (watershed) integrated with all aforementioned data applying MatLab and ArcGIS computing resources generated results that enabled a better spatio-temporal understanding of the Amazon seasonal dynamics. Thus, the principal product of the research was the Coari fluvial oil spill sensitivity index map based on segmented inundation levels obtained with the proposed methodology.