Fontes primárias da história do vácuo e da pressão atmosférica na sala de aula: cartas e jornais históricos em articulação com o livro-texto do ensino médio

The use of the History and the Philosophy of Science (HPS) for the teaching of science and scientific subjects has been advocated in recent decades. It has been pointed out that the History of Science could make for a deeper learning of scientific concepts, since it would promote a contact with the problems which that knowledge has set out to solve. Furthermore, historical episodes would serve to put the discussions about the nature of scientific knowledge into context. With a view to explore those potentialities, the literature in the field has sought to identify the challenges and obstacles for the didactic transposition of subjects from the History of Science. Amongst many aspects, the deficiencies in the training of teachers, so that they can work with the insertion of HPS in the classroom have been highlighted. Another aspect that has been mentioned to be a challenge has to do with the didactic transposition of the Primary Sources, that is, of the original texts on the History of Science. The Primary Sources have significant potentialities: making a connection possible between scientists and concepts, showing the difficulties faced during scientific endeavors, perceiving the role of mistakes as obstacles to be surpassed, not as defeat, etc. On the other hand, there has been little exploration of these concepts in an educational context, due to their own peculiarities. The original texts are often hard to understand and their interpretation demands knowledge of the historical and scientific context in which they were written, as well as skills pertaining to the conduction of research in the field of the History of Science. With this scenario in mind, the research towards this Professional MSc degree starts from the challenge of elaborating and discussing proposals which could enable the didactical transposition of the Primary Sources. We have worked specifically with Primary Sources on the History of the Vacuum and of the Atmospheric Pressure, because of the insertion of these subjects in the Brazilian High School curriculum, in connection with the didactical textbooks. "Historic Journals" were made up from clippings of the original historical texts, as was a Didactical Unit, which takes the usual textbooks as a basis and contemplates using the Journals and the entire Primary Sources in High School. At last, we have elaborated and implemented a course designed for the preparation of teachers and for being an opportunity for the discussion of the feasibility of putting these kinds of proposal into practice

Olhar em terra de cego: a visualidade em Ensaio sobre a Cegueira

"Looking at earth from blind: travel in the visuality of the test on Blindness" is a literary Essay resulted from the experience of different points of view regarding the Essay on Blindness (1996), not only showing a Modern aesthetical tendency in dialog with the Baroque one, but also discussing subjects related to the History of Mentalities. The chapters are disposed as follows: The first one presents a short Excursus about the author and his work; the second one introduces the concept of Allegory exemplifying it with representative images of Romance; the third one presents tragic elements in dialog with the Bataille Eroticism in an Allegory of Feeling; the fourth one shows Stylistic Features used as a display mean of Comedy in Romance going towards the musicalness, being the features used to provoke laugh; the fifth and last one discusses about the study pertinence. To conclude, in favor of a Sight Education, the study considered authors such as: Ariès (1977), Bataille (2003), Bakhtin (2002, 2000, 1999), Benjamin (2000, 1996), Chauí (2005, 2000), Foucault (2006, 2005, 2004, 2002), Freud (1970), Hansen (2006), Lino (2004), Sartre (2005), Vovelle (1996)

Função de distribuição generalizada aplicada à velocidade de rotação estelar

In the present work we use a Tsallis maximum entropy distribution law to fit the observations of projected rotational velocity measurements of stars in the Pleiades open cluster. This new distribution funtion which generalizes the Ma.xwel1-Boltzmann one is derived from the non-extensivity of the Boltzmann-Gibbs entropy. We also present a oomparison between results from the generalized distribution and the Ma.xwellia.n law, and show that the generalized distribution fits more closely the observational data. In addition, we present a oomparison between the q values of the generalized distribution determined for the V sin i distribution of the main sequence stars (Pleiades) and ones found for the observed distribution of evolved stars (subgiants). We then observe a correlation between the q values and the star evolution stage for a certain range of stel1ar mass

Caracterização estatística de processos sísmicos via Distribuição Generalizada de Pareto. Estudo de caso: João Câmara-RN

The work is to make a brief discussion of methods to estimate the parameters of the Generalized Pareto distribution (GPD). Being addressed the following techniques: Moments (moments), Maximum Likelihood (MLE), Biased Probability Weighted Moments (PWMB), Unbiased Probability Weighted Moments (PWMU), Mean Power Density Divergence (MDPD), Median (MED), Pickands (PICKANDS), Maximum Penalized Likelihood (MPLE), Maximum Goodness-of-fit (MGF) and the Maximum Entropy (POME) technique, the focus of this manuscript. By way of illustration adjustments were made for the Generalized Pareto distribution, for a sequence of earthquakes intraplacas which occurred in the city of João Câmara in the northeastern region of Brazil, which was monitored continuously for two years (1987 and 1988). It was found that the MLE and POME were the most efficient methods, giving them basically mean squared errors. Based on the threshold of 1.5 degrees was estimated the seismic risk for the city, and estimated the level of return to earthquakes of intensity 1.5°, 2.0°, 2.5°, 3.0° and the most intense earthquake never registered in the city, which occurred in November 1986 with magnitude of about 5.2º

Uma Análise Comparativa entre Sistemas de Combinação de Classificadores com Distribuição Vertical dos Dados

In systems that combine the outputs of classification methods (combination systems), such as ensembles and multi-agent systems, one of the main constraints is that the base components (classifiers or agents) should be diverse among themselves. In other words, there is clearly no accuracy gain in a system that is composed of a set of identical base components. One way of increasing diversity is through the use of feature selection or data distribution methods in combination systems. In this work, an investigation of the impact of using data distribution methods among the components of combination systems will be performed. In this investigation, different methods of data distribution will be used and an analysis of the combination systems, using several different configurations, will be performed. As a result of this analysis, it is aimed to detect which combination systems are more suitable to use feature distribution among the components

Uso de replicação móvel para distribuição de vídeo digital em redes de computadores

A maioria da soluções apresentadas como candidatas à implementação de serviços de distribuição de áudio e vídeo, têm sido projetadas levando-se em consideração determinadas condições de infra-estrutura, formato dos fluxos de vídeo a serem transmitidos, ou ainda os tipos de clientes que serão atendidos pelo serviço. Aplicações que utilizam serviços de distribuição de vídeo normalmente precisam lidar com grandes oscilações na demanda pelo serviço devido a entrada e saída de usuários do serviço. Com exemplo, basta observar a enorme variação nos níveis de audiência de programas de televisão. Este comportamento coloca um importante requisito para esta classe de sistemas distribuídos: a capacidade de reconfiguração como conseqüência de variações na demanda. Esta dissertação apresenta um estudo que envolveu o uso de agentes móveis para implementar os servidores de um serviço de distribuição de vídeo denominada DynaVideo. Uma das principais características deste serviço é a capacidade de ajustar sua configuração em conseqüência de variações na demanda. Como os servidores DynaVideo podem replicar-se e são implementados como código móvel, seu posicionamento pode ser otimizado para atender uma dada demanda e, como conseqüência, a configuração do serviço pode ser ajustada para minimizar o consumo de recursos necessários para distribuir vídeo para seus usuários. A principal contribuição desta dissertação foi provar a viabilidade do conceito de servidores implementados como agentes móveis Java baseados no ambiente de desenvolvimento de software Aglet.

Algorítmo evolucionário para a distribuição de produtos de petróleo por redes de polidutos

The distribution of petroleum products through pipeline networks is an important problem that arises in production planning of refineries. It consists in determining what will be done in each production stage given a time horizon, concerning the distribution of products from source nodes to demand nodes, passing through intermediate nodes. Constraints concerning storage limits, delivering time, sources availability, limits on sending or receiving, among others, have to be satisfied. This problem can be viewed as a biobjective problem that aims at minimizing the time needed to for transporting the set of packages through the network and the successive transmission of different products in the same pipe is called fragmentation. This work are developed three algorithms that are applied to this problem: the first algorithm is discrete and is based on Particle Swarm Optimization (PSO), with local search procedures and path-relinking proposed as velocity operators, the second and the third algorithms deal of two versions based on the Non-dominated Sorting Genetic Algorithm II (NSGA-II). The proposed algorithms are compared to other approaches for the same problem, in terms of the solution quality and computational time spent, so that the efficiency of the developed methods can be evaluated

Uma abordagem através de algoritmos transgenéticos para o problema da configuração do traçado de uma rede de distribuição de gás natural

Este trabalho apresenta um algoritmo transgenético híbrido para a solução de um Problema de Configuração de uma Rede de Distribuição de Gás Natural. O problema da configuração dessas redes requer a definição de um traçado por onde os dutos devem ser colocados para atender aos clientes. É estudada neste trabalho uma maneira de conectar os clientes em uma rede com arquitetura em forma de árvore. O objetivo é minimizar o custo de construção da rede, mesmo que para isso alguns clientes que não proporcionam lucros deixem de ser atendidos. Esse problema pode ser formulado computacionalmente através do Problema de Steiner com Prêmios. Este é um problema de otimização combinatória da classe dos NPÁrduos. Este trabalho apresenta um algoritmo heurístico para a solução do problema. A abordagem utilizada é chamada de Algoritmos Transgenéticos, que se enquadram na categoria dos algoritmos evolucionários. Para a geração de soluções inicias é utilizado um algoritmo primaldual, e pathrelinking é usado como intensificador

A história do intemperismo na Província Borborema Oriental, Nordeste do Brasil: implicações paleoclimáticas e tectônicas

Until some years ago, weathering geochronology was primarily based on the K-Ar and 40Ar/39Ar dating of supergene minerals. Recent advances in the analysis of supergene goethite by the (U-Th)/He method expanded the number of suitable minerals for such purpose, as well as the time of application for weathering geochronology. This study represents the first systematic approach in Brazil, combining both the 40Ar/39Ar e (U-Th)/He methodologies to improve the knowledge on the weathering and the age of nonfossiliferous sediments. Supported by geologic and geomorphologic correlations, we identified different types of weathering profiles occurring in the interior and coastal areas of northeastern Brazil. These profiles were correlated to main regional geomorphological domains: the Borborema Plateau , the Sertaneja Depression , and the Coastal Cuestas and Plains, and respective planation surfaces, which study is fundamental to understand the landscape evolution of the northern portion of the eastern Borborema Province. The depth and stratigraphic organization of the weathering profiles in each of the geomorphological domains permitted to establish that: (i) the profiles on the highlands that cap the Borborema Surface are deeper (up to 100 m) and can be considered as typical lateritic profiles; (ii) on the lowlands that form the Sertaneja Surface , the weathering profiles are shallow and poorly developed (2-5 m deep); (iii) the profiles along the coastal area are moderately developed (up to 25 m deep), and are characterized by thick saprolites and mottle zones. Aiming to establish the timing of the evolution of northeastern Brazil, we studied 29 weathering profiles representing distinct topographic levels of the Borborema Province, from the highlands to the coast, through the analysis of 248 grains of supergene manganese oxides using laser step-heating 40Ar/39Ar geochronology. Additionally, we applied the (U-Th)/He method in 20 weathering profiles, by dating 171 grains of supergene iron oxides and hydroxides. Geochronological results for 248 grains of manganese oxides analyzed by the 40Ar/39Ar method indicate that the weathering profiles in the study area record the history of weathering from the Oligocene to the Pleistocene, with ages in the order of 31.4 ± 1.0 Ma to 0.8 ± 0.4 Ma. Dating of 171 grains of goethite by the (U-Th)/He method yielded ages ranging from 43.2 ± 4.3 Ma to 0.8 ± 0.1 Ma, suggesting the weathering processes last from the Eocene to the Pleistocene. The precipitation of supergene goethite in this interval confirms the age of the weathering processes identified from the manganese oxides record. 105 goethite grains from 8 different occurrences of the Barreiras Formation were dated by the (U-Th)/He method. Five grains collected from the cement in the Barreiras Formation sandstones, in the Lagoa Salgada and Rio do Fogo coastal cuestas, yielded ages of 17.6 ± 1.8 Ma, 17.3 ± 1.7 Ma, 16.3 ± 1.6 Ma, 16.2 ± 1.6 Ma and 13.6 ± 1.4 Ma. Results of 69 goethite grains from authigenic pisoliths collected in 7 different localities also yielded concordant ages, varying from 17.8 ± 1.8 to 7.5 ± 0.8 Ma. Results obtained from 31 detrital grains are concordant in 3 distinct localities (Lagoa Salgada, Praia da Garças e Ponta Grossa); they vary in the range of 43.2 ± 4.3 to 21.6 ± 2.2 Ma, and indicate that the maximum age for the Barreiras Formation deposition is around 22 Ma. 40Ar/39Ar results for 15 manganese oxides grains associated with the Barreiras Formation weathering profiles, in 3 different localities, vary from 13.1 ± 0.9 to 7.7 ± 0.4 Ma, in the same range of ages obtained by the (U-Th)/He method. The systematic application of the 40Ar/39Ar and (U-Th)/He methods, respectively for manganese oxides and goethites, show that the Barreiras Formation sediments were already deposited since ca. 17 Ma, and that the weathering processes were active until ca. 7 Ma ago. The ages obtained from manganese oxides collected in the Cenozoic basalts (Macau Formation) also reveal a weathering history between 19 and 7 Ma, pointing to hot and humid conditions during most of the Miocene. 40Ar/39Ar ages yielded by manganese oxides associated with the Serra do Martins Formation vary from 14.1 ± 0.4 to 10.5 ± 0.3 Ma. On the other hand, (U-Th)/He ages from iron oxides/hydroxides collected in the Serra do Martins Formation mesas vary from 20.0 ± 2.0 to 5.5 ± 0.6 Ma, indicating that those sediments are older than 20 Ma. 40Ar/39Ar and (U-Th)/He results produced in this study are in agreement with paleoclimatic interpretations based on stable isotopes and clay index values measured in the Atlantic Ocean sediments, validating the use of weathering geochronology to investigate paleoclimatic variations. The direct dating of the Barreiras Formation permitted, for the first time, confident inferences on the age of the brittle deformation recorded by this sedimentary unit in the Rio Grande do Norte and Ceará states. The first event, syn-deposition, occurred during the early Miocene; an younger event, related to the post-depositional deformation of the Barreiras Formation, is associated with tectonic activity from the very early Miocene to the Holocene. In agreement with data from other areas, results obtained in this study reveal that the depth and complexity of the weathering profiles reflect the time of exposition of such areas to the weathering agents close to the surface. However, there is no clear relationship between ages vs. altitude. The depth and the stratigraphic organization of weathering profiles in northeastern Brazil, contrary to the southeastern Brazil pattern, do not vary toward the coast. In our study area, field observations reveal the presence of ancient, thick and complex lateritic profiles preserved in the sedimentary mesas on the Borborema Plateau, as younger, narrow and incipient ones occur in the dissected areas. Geochronological results obtained for these profiles yielded older ages on the high altitudes, and younger ages in the lowlands, suggesting the scarp retreatment is the most reliable model to explain the regional landscape evolution. However, in the coastal lowlands, the relatively older ages obtained indicate that more complexes processes were involved in the modeling of the local relief

Evolução morfodinâmica da região de influência estuarina do Rio Curimataú/RN, com ênfase nas alternativas do ambiente deposicional de manguezal e a integração de geodados em Sig

The estuaries are important investigation zones of the actual morphodynamic and of depositional facies of recent geological history. They are constituted in important receptor means of the coastal area sediments, where the evolutionary processes occur quickly. They are also attractive means for the development of anthropic activities, which in a disordered way interfere in the active processes in the sedimentary balance of the coastal areas. Among the human interventions, the alterations of the depositional environment of mangroves in areas of tropical estuary is deserving relevance, whose implications for the environment estuarine and the coastal adjacent, they are still far to be known. Due to the interest of the sedimentologic component in the comprehension of the processes linked to the evolution of the environments estuarine and coastal adjacent, this work, aimed at the understanding of the morphodynamic coastal phenomena that comprise the region of estuarine influence of the River Curimataú / RN. It was also evaluated in the morphodynamic context the implications due to alterations of the depositional environment of mangrove by anthropic activity. The Curimataú Estuary, located in the south portion of the oriental coast of Rio Grande do Norte, in the last decades has been objective of the overwhelming occupation of the shrimp farm in areas of mangroves, which were implanted with perspectives of development in a short to medium period. On the other hand, the estuary and its region of coastal influence lacks enough information to subsidize the planning and reorganization more effective of the surrounding activities. Thus, it was intended with this work to give a contribution target tothe maintainable use of the coastal resources of this region. A series of studies using data of orbital and acoustic remote sensing, as of sediments sampling, were executed in the gutter of the estuary. The obtained results starting from the interpretation of bathymetric maps, echo sounder graphics and of distribution of sediments made possible the location of the estuary based in morpho-sedimentar criteria. The estuarine tidal flat was dissected in environments of intertidal mangroves, supratidal mangroves and apicuns with base in the integration of data of sensor optic and of radar following by the field control. The adjacent coast that is influenced by the Curimataú estuary, was segmented according to their geomorphologic characteristics, where each segment had a point of observation of the beach morphodynamic, during the period from january/2001 to february/2002. Once every month, beaches profiles, collections of sediments in the beach zones, as measurement of hydrodynamic parameters were executed. The results of the observations of the tidal environment showed that the area of estuarine influence of the Curimataú begins to suffer negative sedimentary taxes, where in some beaches, the erosive processes are already observed. The granulometric characteristics of the beach sediments start to tend for the increase of thin sand in the erosive periods. The destruction of the depositional environments of mangroves of the Curimataú estuary, to the construction of shrimp farms, can be providing the diminution of the tidal prism of the estuary, enlarging the effects of the local increasing of the sea level, through the smaller supplying of sediments to the adjacent coast. Besides this, it was verified the possibility of the sanding of the tidal channel in the margins of the destroyed areas of mangroves, where very high taxes of sedimentation of thin materials were estimated in case of these areas were preserve

Caracterização infravermelho e distribuição espectral de energia para as estrelas com planetas

Neste trabalho estudamos o comportamento das estrelas pertencentes a sistemas planetários no que diz respeito às suas características infravermelho e à distribuição espectral de energia (SED). Nosso estudo tem como base uma análise detalhada do comportamento da emissão no infravermelho de 48 estrelas com planetas, classificadas como estrelas da seqüência principal, subgigantes ou gigantes. Foram analisados dados de fotometria infravermelho nas bandas 12, 25 e 60µm do catálogo de fontes IRAS puntiformes (IPSC) e nas bandas JHK do projeto 2 Micron All Sky Survey (2MASS). A partir do cálculo da discrepância na posição de apontamento da fonte e do cálculo do índice de cor, selecionamos e localizamos os objetos no diagrama de cor-cor do IRAS. Este diagrama permite-nos identificar possíveis objetos detentores de disco de poeira. Fizemos também uma análise da distribuição espectral de energia onde observamos também traços de excesso de fluxo no infravermelho, com isso, confirmarmos a presença do disco de poeira nos objetos identificados no diagrama de cor. Apesar da atual amostra de estrelas com planetas incluir apenas um subconjunto de estrelas com planetas detectadas na vizinhança solar, a presente análise do fluxo infravermelho nesses objetos oferecem uma possibilidade única de estudar as características infravermelho das estrelas pertencentes aos sistemas planetários extra-solar. Neste contexto, nosso estudo aponta resultados interessantes, entre outros destacamos o fato de algumas estrelas com planetas apresentarem um peculiar fluxo IRAS [60-25], indicando a co-existência de poeira juntamente com os planetas destes sistemas extra solar

A distribuição F generalizada para selecionar modelos de sobrevivência com fração de cura

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Usando a história da resolução de alguns problemas para introduzir conceitos: sistemas lineares, determinantes e matrizes.

In this work we studied the method to solving linear equations system, presented in the book titled "The nine chapters on the mathematical art", which was written in the first century of this era. This work has the intent of showing how the mathematics history can be used to motivate the introduction of some topics in high school. Through observations of patterns which repeats itself in the presented method, we were able to introduce, in a very natural way, the concept of linear equations, linear equations system, solution of linear equations, determinants and matrices, besides the Laplacian development for determinants calculations of square matrices of order bigger than 3, then considering some of their general applications

Evolução termocronológica do sistema de falhas Senador Pompeu-CE

The region of the Senador Pompeu Shear Zone (SPSZ), in the North Tectonic Domain of the Borborema Province (BP), has its recent history associated with to South Atlantic Ocean formation event at the Jurassic. A lot of geologics models have discussed about crustal axis elevation in local scale and large scale (Borborema Province), relative to importants regionals tectonics directions of it. The identification and the relationship among this surfaces, stepped in many topographyc levels by tectonics mecanisms, is dificult because of the erosion process on it. Over there, sedimentary deposits is complex and it has not biostratigraphyc record in continental deposits. The analysis metodology on apatita fission-track, in the region of the SPSZ, purpose the more knowledge about morphotectonics mecanisms of the area and the impruvement of its morphotectonics models. For this, it was moleled the age and thermal history of the 11 apatites samples collected on both sides of this shear zone, taking relationships among other results of the thermochronology studies in the BP. Based on the thermal studies in this search, the region of the BP developed on two distint cooling events, separated for one period of relative stabilited. The first episode occur between 130 and 90 M.y., has been began when the samples cross the 120°C isoterm for last time and fineshed at 70°C. The second moment of the cooling process was began about 30 M.y., when the temperature was 90°C, from this to the equlibrium with present surface temperature at 30°C. Some evidences indicated a relacionship between thermal episodes and uplift events of the regional relief. The fundaments of the interpretation was based mainly on comparatives studies among results of the thermochronology analysis and geologics studies about BP. Nóbrega et al.(2005), e.g., on studies about the Portalegre Shear Zone, got similar results on SPSZ, with some details relative to local tectonic activity. Morais Neto et al. (2000) interpreted two importants cooling events in the BP based on their regional studies, that can be associated to regional uplift events. When Assine (1992) studied the stratigraphyc sequences of the Araripe Basin, in the south of Ceará state, conclude that the abrupt return to continentals condictions from the last sedimentar sequency (albiano-cenomaniane) indicate a regional uplift of the NE region of the Brazil at the 100 M.y., in the Albiano Intermediate/Superior. This ages are compatible to termal model of the SPSZ. This two periods of the thermal history of the BP are completely registered in the apatites samples just one age groups of the fission-track, that it is the most ancient age groups. This one suggest it has happened in response to heating before 75 M.y and it has erased the last report of the first moment relief evolution of the BP. The NNE-SSW and E-W structure reativation can have created ideal condictions for heating and local elevations of the geothermal gradients. The equilibrium between the apatites temperatures of this groups and the regionais temperatures took place about 50 M.y., when the samples of the two ages groups had a simillar evolution to present surfaces temperatures

Caracterização de minerais pesados ao longo do Rio Piranhas-Açu/RN distribuição e proveniência

This dissertation deals with the characterization, distribution and provenience of heavy minerals along the Piranhas-Açu River, from the City of Parelhas (Seridó River) to your mouth at the City of Macau-RN. Many heavy minerals species were recorded in this study: clinoamphibole, epidote (including zoisite), garnet, sillimanite, tourmaline, staurolite, andalusite, zircon, rutile, augite, ilmenite, hematite and magnetite. Major transparent minerals, those forming more than 5% of some assemblages, are hornblende, epidote, tourmaline, staurolite and zircon. Predominant opaque mineral is ilmenite. Six assemblages were identified along the river: (i) Garnet-hornblende-tourmaline with sillimanite, when cutting rocks of the Seridó Formation; (ii) Hornblende-garnet-zircon, when crossing rocks of the Caicó gnaisse-migmatitic Complex; (iii) Hornblende-zircon-epidote-staurolite, when draining rocks of the Jucurutu Formation; (iv) Hornblende-zircon-epidote, when cutting rocks of the Açu Formation; (v) Hornblende-zircon-staurolite, on the lowermost Açu River, when crossing limestones of the Jandaíra Formation and (vi) Zircon-tourmaline-staurolite in the Açu River mouth (Cenozoic rocks) where coastal process dominate. Mineral ratios that reflect differences in grain shape, density, and selective chemical decomposition were used in an attempt to isolate the effects of source and process as controls of mineral variability. Reworking of the sediments was regionally effective in selective sorting; the more equant minerals (e.g. epidote) and heavier minerals (e.g. opaques) had a higher probability of being selected for permanent deposition during reworking. The processes of selective decomposition stand out at the river mouth. A priori knowledge of provenance, associated with the assemblage distribution and effects of process were utilized to the interpretations, that points to the follow provenances: hornblende comes from micashists of the Seridó Formation, orthognaisses and amphibolites of the Caico Complex, paragnaisses and paranphibolites of the Jucurutu Formation and granites intrusions; epidote comes from paragnaisses and calciosilicatics of the Jucurutu Formation, granites intrusions (-Npy3al/ca and -Npy3mz, gravels deposits and Açu Formation; Andalusite and staurolite come from the Seridó Formation; Sillimanite, tourmaline and garnet come from micashists of the Seridó Formation, as well as from quartzites of the Equador Formation; Zircon comes from Precambrian rocks (pink and prismatic zircon) and from sediments of several cycles (round zircon); Opaques come from all rocks cutted for the Piranhas-Açu River; Rutile comes from metamorphic rocks, in general; Augite comes from the Ceará-Mirim, Serra do Cuó and Macau volcanisms. The texture of gravels deposits reveals a sediment transport mechanisms by traction-current processes, together with a diagenetic clay matrix suggests a hot-humid environments for deposition. The presence of unstable heavy minerals assemblages, as well as pebbles of different composition and degrees of rounding and esfericity, indicate more than one source. The occurrence of calcio/alkaline granites suites, in areas closed to the gravel deposits, suggests that these intrusions are the main source of sediments. This could explain for instance, the significant amounts of epidote and presence of unstable heavy minerals (e.g. hornblende). The analyses of heavy minerals also show significante variability between the modern (Piranhas-Açu) and ancestral (Açu Formation) river sediments. In general, these variations reflect relatively higher unstable and lower stable heavy minerals contents of the modern Piranhas-Açu sediments. The absence of significant compositional differences probably reflects uniform weathering conditions