Le criblage virtuel est utilisé dans la recherche de médicaments et la construction de modèle de prédiction de toxicité. L’application d’un protocole de criblage est précédée par une étape d’évaluation sur une banque de données de référence. La composition des banques d’évaluation est un point critique ; celles-ci opposent généralement des molécules actives à des molécules supposées inactives, faute de publication des données d’inactivité. Les molécules inactives sont néanmoins porteuses d’information. Nous avons donc créé la banque NR-DBIND composée uniquement de molécules actives et inactives expérimentalement validées et dédiées aux récepteurs nucléaires. L’exploitation de la NR-DBIND nous a permis d’étudier l’importance des molécules inactives dans l’évaluation de modèles de docking et dans la construction de modèles de pharmacophores. L’application de protocoles de criblage a permis d’élucider des modes de liaison potentiels de petites molécules sur FXR, NRP-1 et TNF⍺. / Virtual screening is widely used in early stages of drug discovery and to build toxicity prediction models. Commonly used protocols include an evaluation of the performances of different tools on benchmarking databases before applying them for prospective studies. The content of benchmarking tools is a critical point; most benchmarking databases oppose active data to putative inactive due to the scarcity of published inactive data in the literature. Nonetheless, experimentally validated inactive data also bring information. Therefore, we constructed the NR-DBIND, a database dedicated to nuclear receptors that contains solely experimentally validated active and inactive data. The importance of the integration of inactive data in docking and pharmacophore models construction was evaluated using the NR-DBIND data. Virtual screening protocols were used to resolve the potential binding mode of small molecules on FXR, NRP-1 et TNF⍺.

Este trabalho estudou o impacto do nitrato, proveniente de uma fossa negra desativada nas zonas não-saturada e saturada no Aqüífero Adamantina (Urânia, SP), através do acompanhamento hidrogeoquímico dos íons maiores (incluindo a série nitrogenada), menores, isótopos estáveis (15NNO3, 15NN2O, 18ON2O, 18ONO3, 18OO2, 13CCO2) e gases (O2, CO2, N2O e CH4). Os três anos de monitoramento da fossa negra, desativada desde 2002, se deu pela construção de uma estação experimental, constituída de um poço cacimba com 11,20 m de profundidade. Foram instalados, ao longo de sua parede até a zona saturada, 12 tensiômetros e 12 lisímetros de sucção (0,5 a 9,0 m), bem como um poço de monitoramento instalado no fundo da estação, para o monitoramento dos processos hidráulicos e da qualidade da água infiltrada. Os resultados obtidos sobre a hidráulica de infiltração mostraram que a zona nãosaturada apresenta condutividade hidráulica média vertical entre 3,1x10-6 a 1,4x10-5 m/s. As tensões capilares medidas indicaram a ocorrência de variações laterais e em profundidade, cuja origem está relacionada às heterogeneidades do material geológico. Tais constatações possibilitaram a identificação de três diferentes zonas hidráulicas: a primeira, entre 0,5 e 2,0 m; a segunda, de 2,0 a 7,0 m e a terceira, a partir de 7,0 m até o nível d´água. A taxa de recarga na área é de 171 mm, o que corresponde a 13% da precipitação anual. As velocidades das frentes de molhamento indicaram um tempo de trânsito de 90 dias para a água se deslocar de 0,5 até 9,0 m de profundidade. As análises químicas da água ao longo do perfil da zona não-saturada e do poço de monitoramento, apontaram concentrações altas de nitrato ao longo de todo o perfil (até 2028,94 mg/L). Os parâmetros físico-químicos, isotópicos e de gases analisados apresentaram variações, sazonais e em profundidade, de suas concentrações. Os perfis de concentração de gases, isótopos e série nitrogenada indicam que estes parâmetros apresentam um comportamento ?zigue-zague? sendo os maiores valores a 2,0; 4,0 e 6,0 m de profundidade. Este comportamento seria condicionado pelas características texturais do material geológico, o que leva a considerar a existência de áreas de menor permeabilidade nestes pontos, restringindo o acesso de águas ricas em oxigênio e de gases ao longo da zona não-saturada e co-existência de zonas redutoras em meio a zonas oxidantes (microcosmos). Este monitoramento detalhado possibilitou o estabelecimento dos principais processos hidrogeoquímicos atuantes na zona não-saturada: i) oxidação da matéria orgânica, ii) amonificação, iii) nitrificação, iv) metanogênese e v) desnitrificação. Um fator muito importante a ser levantado é a simultaneidade entre os mecanismos de nitrificação e desnitrificação na zona não-saturada. Várias foram as constatações que reforçam esta hipótese, exemplificadas pelas seguintes relações: i) 15NN2O e 18ON2O; ii) 15NN2O e 15NNO3 e iii) 18ONO3 e15NNO3. Os valores de ?15NNO3 obtidos foram de +6,80 a +30,09? (estação úmida) e +9,54 a +23,25? (estação seca). Valores mais enriquecidos de ?15NNO3, comparados à assinatura isotópica reportada para dejetos humanos (+8,1? a +13,1?), em conjunto com os resultados de ?18ONO3 (-3,60 a 4,50 ?), razão de fracionamento destes isótopos e os coeficientes de regressão, obtidos em outros trabalhos, reforçaram a coexistência de desnitrificação e nitrificação na área estudada. Os resultados de ?15NN2O e ?18OO2 também são indicativos de desnitrificação. As assinaturas destes dois isótopos (-16,16 a -11,94? e 28,05 a 30,69?, respectivamente), confrontados aos valores reportados em outros trabalhos (-37 a -11? e -21 a +57?), indicam que o N2O, detectado na área, seria produzido por esse processo. Contudo, cabe salientar que o uso de isótopos de 18OO2 e 15NN2O constitui-se ainda em técnica muito recente em estudos hidrogeológicos, carecendo de trabalhos que stabeleçam as assinaturas isotópicas para os processos de nitrificação e desnitrificação considerando as diferentes fontes de contaminação de nitrato. / The present work studied the impact of nitrate from an inactive cesspit to the unsaturated and saturated zones of the Adamantina Aquifer (Urânia, São Paulo, Brazil), through the hydrogeochemistry of major ions (including the nitrogen series), minor ions, stable isotopes (15NNO3, 15NN2O, 18ON2O, 18ONO3, 18OO2, 13CCO2) and gases (O2, CO2, N2O and CH4). The cesspit, which has been inactive since 2002, was monitored for three years after the construction of a monitoring station. The station is comprised by a 11.20m deep dug well, in which 12 tensiometers and 12 suction lysimeters were installed from the surface down to the saturated zone (0.5-9.0 m). A monitoring well was installed at the bottom of the monitoring station. The station was used to examine the hydraulic processes and the quality of the infiltrating water. The results from the hydraulics of the water infiltration show that the unsaturated zone presents average hydraulic conductivity between 3.1x10-6 and 1.4x10-5 m/s. The capillary tension varies laterally and vertically, which is attributed to the heterogeneities of the geological material. These results allowed the identification of three different hydraulic zones: the first one, between the depths of 0.5 and 2.0 m; the second one, between 2.0 and 7.0 m and the third one, from the depth of 7.0 m down to the water level. The recharge rate of the area is 171 mm, which corresponds to 13% of the annual precipitation. The velocities of the wetting fronts indicated a travel time of 90 days for the water to move between the depths of 0.5 m and 9.0m. The chemical analyses of the water of the unsaturated and saturated zones indicated high concentration of nitrate, along the entire unsaturated zone (up to 2028,94 mg/L). The physico-chemical, isotopic and gases data vary seasonally and spatially. The concentration of gases, isotopes and nitrogen species show a ?zig-zag? behavior, with peaks of concentration at the depths 2.0; 4.0 and 6.0 m. This behavior is a consequence of the textural features of the geological material, with less permeable areas occuring at these depths, which can restrict the access of oxygen- and gases-rich waters along the unsaturated zone and the coexistence of reducing zones among oxidizing ones (microcosms). The detailed monitoring provided data to establish the main hydrogeochemical processes occuring in the unsaturated zone: i) oxidation of organic matter, ii) ammonification, iii) nitrification, iv) methanogenesis and v) denitrification. A very important fact is the simultaneous occurrence of nitrification and denitrification processes in the unsaturated zone. This fact is verified by a series of observations, which can be demonstrated by the following relationships: i) 15NN2O and 18ON2O; ii) 15NN2O and 15NNO3 and iii) 18ONO3 and15NNO3. The values obtained for ?15NNO3 are between +6.80 and +30.09? (wet season) and between +9.54 and +23.25? (dry season). The values of ?15NNO3, which are more enriched than the isotopic fingerprint for sewage (+8.1? to +13.1?), along with the results for ?18ONO3 (-3.60 to 4.50 ?), the fractionation ratio of this isotopes and the linear regression coefficient, obtained by other authors, reinforced the coexistence of denitrification and nitrification in the studied area. The results of ?15NN2O and ?18OO2 also indicated the presence of denitrification. The signatures of these two isotopes (-16.16 to -11.94? and 28.05 to 30.69?, respectivelly), compared to values reported by other authors (-37 to -11? and -21 to +57?), indicate that the N2O detected in the area is produced by this process. However, it is worth emphasizing that the use of 18OO2 and 15NN2O isotopes is still a very new technique in hydrogeological studies, and more studies are needed to establish the isotopic fingerprints of the nitrification and denitrification processes, considering the different sources of nitrate contamination.

Este trabalho estudou o impacto do nitrato, proveniente de uma fossa negra desativada nas zonas não-saturada e saturada no Aqüífero Adamantina (Urânia, SP), através do acompanhamento hidrogeoquímico dos íons maiores (incluindo a série nitrogenada), menores, isótopos estáveis (15NNO3, 15NN2O, 18ON2O, 18ONO3, 18OO2, 13CCO2) e gases (O2, CO2, N2O e CH4). Os três anos de monitoramento da fossa negra, desativada desde 2002, se deu pela construção de uma estação experimental, constituída de um poço cacimba com 11,20 m de profundidade. Foram instalados, ao longo de sua parede até a zona saturada, 12 tensiômetros e 12 lisímetros de sucção (0,5 a 9,0 m), bem como um poço de monitoramento instalado no fundo da estação, para o monitoramento dos processos hidráulicos e da qualidade da água infiltrada. Os resultados obtidos sobre a hidráulica de infiltração mostraram que a zona nãosaturada apresenta condutividade hidráulica média vertical entre 3,1x10-6 a 1,4x10-5 m/s. As tensões capilares medidas indicaram a ocorrência de variações laterais e em profundidade, cuja origem está relacionada às heterogeneidades do material geológico. Tais constatações possibilitaram a identificação de três diferentes zonas hidráulicas: a primeira, entre 0,5 e 2,0 m; a segunda, de 2,0 a 7,0 m e a terceira, a partir de 7,0 m até o nível d´água. A taxa de recarga na área é de 171 mm, o que corresponde a 13% da precipitação anual. As velocidades das frentes de molhamento indicaram um tempo de trânsito de 90 dias para a água se deslocar de 0,5 até 9,0 m de profundidade. As análises químicas da água ao longo do perfil da zona não-saturada e do poço de monitoramento, apontaram concentrações altas de nitrato ao longo de todo o perfil (até 2028,94 mg/L). Os parâmetros físico-químicos, isotópicos e de gases analisados apresentaram variações, sazonais e em profundidade, de suas concentrações. Os perfis de concentração de gases, isótopos e série nitrogenada indicam que estes parâmetros apresentam um comportamento ?zigue-zague? sendo os maiores valores a 2,0; 4,0 e 6,0 m de profundidade. Este comportamento seria condicionado pelas características texturais do material geológico, o que leva a considerar a existência de áreas de menor permeabilidade nestes pontos, restringindo o acesso de águas ricas em oxigênio e de gases ao longo da zona não-saturada e co-existência de zonas redutoras em meio a zonas oxidantes (microcosmos). Este monitoramento detalhado possibilitou o estabelecimento dos principais processos hidrogeoquímicos atuantes na zona não-saturada: i) oxidação da matéria orgânica, ii) amonificação, iii) nitrificação, iv) metanogênese e v) desnitrificação. Um fator muito importante a ser levantado é a simultaneidade entre os mecanismos de nitrificação e desnitrificação na zona não-saturada. Várias foram as constatações que reforçam esta hipótese, exemplificadas pelas seguintes relações: i) 15NN2O e 18ON2O; ii) 15NN2O e 15NNO3 e iii) 18ONO3 e15NNO3. Os valores de ?15NNO3 obtidos foram de +6,80 a +30,09? (estação úmida) e +9,54 a +23,25? (estação seca). Valores mais enriquecidos de ?15NNO3, comparados à assinatura isotópica reportada para dejetos humanos (+8,1? a +13,1?), em conjunto com os resultados de ?18ONO3 (-3,60 a 4,50 ?), razão de fracionamento destes isótopos e os coeficientes de regressão, obtidos em outros trabalhos, reforçaram a coexistência de desnitrificação e nitrificação na área estudada. Os resultados de ?15NN2O e ?18OO2 também são indicativos de desnitrificação. As assinaturas destes dois isótopos (-16,16 a -11,94? e 28,05 a 30,69?, respectivamente), confrontados aos valores reportados em outros trabalhos (-37 a -11? e -21 a +57?), indicam que o N2O, detectado na área, seria produzido por esse processo. Contudo, cabe salientar que o uso de isótopos de 18OO2 e 15NN2O constitui-se ainda em técnica muito recente em estudos hidrogeológicos, carecendo de trabalhos que stabeleçam as assinaturas isotópicas para os processos de nitrificação e desnitrificação considerando as diferentes fontes de contaminação de nitrato. / The present work studied the impact of nitrate from an inactive cesspit to the unsaturated and saturated zones of the Adamantina Aquifer (Urânia, São Paulo, Brazil), through the hydrogeochemistry of major ions (including the nitrogen series), minor ions, stable isotopes (15NNO3, 15NN2O, 18ON2O, 18ONO3, 18OO2, 13CCO2) and gases (O2, CO2, N2O and CH4). The cesspit, which has been inactive since 2002, was monitored for three years after the construction of a monitoring station. The station is comprised by a 11.20m deep dug well, in which 12 tensiometers and 12 suction lysimeters were installed from the surface down to the saturated zone (0.5-9.0 m). A monitoring well was installed at the bottom of the monitoring station. The station was used to examine the hydraulic processes and the quality of the infiltrating water. The results from the hydraulics of the water infiltration show that the unsaturated zone presents average hydraulic conductivity between 3.1x10-6 and 1.4x10-5 m/s. The capillary tension varies laterally and vertically, which is attributed to the heterogeneities of the geological material. These results allowed the identification of three different hydraulic zones: the first one, between the depths of 0.5 and 2.0 m; the second one, between 2.0 and 7.0 m and the third one, from the depth of 7.0 m down to the water level. The recharge rate of the area is 171 mm, which corresponds to 13% of the annual precipitation. The velocities of the wetting fronts indicated a travel time of 90 days for the water to move between the depths of 0.5 m and 9.0m. The chemical analyses of the water of the unsaturated and saturated zones indicated high concentration of nitrate, along the entire unsaturated zone (up to 2028,94 mg/L). The physico-chemical, isotopic and gases data vary seasonally and spatially. The concentration of gases, isotopes and nitrogen species show a ?zig-zag? behavior, with peaks of concentration at the depths 2.0; 4.0 and 6.0 m. This behavior is a consequence of the textural features of the geological material, with less permeable areas occuring at these depths, which can restrict the access of oxygen- and gases-rich waters along the unsaturated zone and the coexistence of reducing zones among oxidizing ones (microcosms). The detailed monitoring provided data to establish the main hydrogeochemical processes occuring in the unsaturated zone: i) oxidation of organic matter, ii) ammonification, iii) nitrification, iv) methanogenesis and v) denitrification. A very important fact is the simultaneous occurrence of nitrification and denitrification processes in the unsaturated zone. This fact is verified by a series of observations, which can be demonstrated by the following relationships: i) 15NN2O and 18ON2O; ii) 15NN2O and 15NNO3 and iii) 18ONO3 and15NNO3. The values obtained for ?15NNO3 are between +6.80 and +30.09? (wet season) and between +9.54 and +23.25? (dry season). The values of ?15NNO3, which are more enriched than the isotopic fingerprint for sewage (+8.1? to +13.1?), along with the results for ?18ONO3 (-3.60 to 4.50 ?), the fractionation ratio of this isotopes and the linear regression coefficient, obtained by other authors, reinforced the coexistence of denitrification and nitrification in the studied area. The results of ?15NN2O and ?18OO2 also indicated the presence of denitrification. The signatures of these two isotopes (-16.16 to -11.94? and 28.05 to 30.69?, respectivelly), compared to values reported by other authors (-37 to -11? and -21 to +57?), indicate that the N2O detected in the area is produced by this process. However, it is worth emphasizing that the use of 18OO2 and 15NN2O isotopes is still a very new technique in hydrogeological studies, and more studies are needed to establish the isotopic fingerprints of the nitrification and denitrification processes, considering the different sources of nitrate contamination.

The Monte Carlo method is, practically, the only approach capable of giving detail insight into complex neutron transport problems. In reactor physics, the method has been used mainly for determining the keff in criticality calculations. In the last decade, the continuously growing computer performance has allowed to apply the Monte Carlo method also on simple burnup simulations of nuclear systems. Nevertheless, due to its extensive computational demands the Monte Carlo method is still not used as commonly as deterministic methods. One of the reasons for the large computational demands of Monte Carlo criticality calculations is the necessity to carry out a number of inactive cycles to converge the fission source. This thesis presents a new concept of fission matrix based Monte Carlo criticality calculations where inactive cycles are not required. It is shown that the fission matrix is not sensitive to the errors in the fission source, and can be thus calculated by a Monte Carlo calculation without inactive cycles. All required results, including keff, are then derived via the final fission matrix. The confidence interval for the estimated keff can be conservatively derived from the variance in the fission matrix. This was confirmed by numerical test calculations of Whitesides's ``keff of the world problem'' model where other Monte Carlo methods fail to estimate the confidence interval correctly unless a large number of inactive cycles is simulated.   Another problem is that the existing Monte Carlo criticality codes are not well shaped for parallel computations; they cannot fully utilise the processing power of modern multi-processor computers and computer clusters. This thesis presents a new parallel computing scheme for Monte Carlo criticality calculations based on the fission matrix. The fission matrix is combined over a number of independent parallel simulations, and the final results are derived by means of the fission matrix. This scheme allows for a practically ideal parallel scaling since no communication among the parallel simulations is required, and no inactive cycles need to be simulated.   When the Monte Carlo criticality calculations are sufficiently fast, they will be more commonly applied on complex reactor physics problems, like non-linear steady-state calculations and fuel cycle calculations. This thesis develops an efficient method that introduces thermal-hydraulic and other feedbacks into the numerical model of a power reactor, allowing to carry out a non-linear Monte Carlo analysis of the reactor with steady-state core conditions. The thesis also shows that the major existing Monte Carlo burnup codes use unstable algorithms for coupling the neutronic and burnup calculations; therefore, they cannot be used for fuel cycle calculations. Nevertheless, stable coupling algorithms are known and can be implemented into the future Monte Carlo burnup codes. / QC 20100709

With the rapid development of economy, Taiwan¡¦s enterprises become bigger and bigger. Hence, the huge business groups play an important role in business environment of Taiwan. However, enterprises collectivization usually causes earning management by cross-shareholding and the related party transaction between group enterprises. In addition, former research which discussing business groups did not include the factor of financial operating. Therefore, in order to confirm if the financial operating is the key factor of earning management, the study separates the total samples into ¡§active financial operating business groups¡¨ and ¡§inactive financial operating business groups¡¨ according to the relevant financial ratio. The period of research contains 2000~2009, and the total effective research tests are 570 copies. Finally, the study develops eight hypotheses in a basis of four kinds of common related party transactions in Taiwan and two kinds of financial operating business groups. The empirical results show that the percentage of disposal assets in active financial operating business groups and the percentage of purchase and sales in inactive financial operating business groups have positive impact on earning management. However, the rest hypotheses have no obvious significance. Therefore, the rest hypotheses will not established.

No description available.

Machine learning is a field that is inspired by how humans and, by extension, the brain learns.The brain consists of a biological neural network that has neurons that are either active or inactive. Modern-day artificial intelligence is loosely based on how biological neural networks function. This paper investigates whether a multi layered perceptron that utilizes inactive/active neurons can reduce the number of active neurons during the forward and backward pass while maintaining accuracy. This is done by implementing a multi layer perceptron using a python environment and building a neuron activation algorithm on top of it. Results show that it ispossible to reduce the number of active neurons by around 30% with a negligible impact on test accuracy. Future works include algorithmic improvements and further testing if it is possible to reduce the total amount of mathematical operations in other neural network architectures with a bigger computational overhead.

Oil and gas companies in Alberta, Canada lose millions of dollars per year due to ineffective management of retired assets. Ineffective management of inactive oil and gas assets in Alberta has led to over 80,000 inactive wells, highlighting the practice of prolonged deferment of asset end-of-life costs. Using the corporate sustainability model and asset management concept model as frameworks, this multiple case study was conducted to explore the strategies that asset managers in small- and medium-sized oil and gas companies used to manage retired assets effectively to increase organizational sustainability. The population for the study included 3 business leaders of small- and medium-sized oil and gas companies in Alberta who implemented effective strategies to manage their retired assets. Data were collected through semistructured interviews with the leaders and review of artifacts including firm documents and websites. Data were compiled, disassembled into fragments, reassembled into a sequence of groups, clarified, and interpreted for meaning. Methodological triangulation and member checking validated the interpretations. Data analysis resulted in 7 themes: responsible leadership commitment, adoption and communication of corporate social responsibility philosophy, regulatory compliance, asset management software tools, dedicated inactive assets and reclamation champion/team, annual budget/long-term planning, and performance measurement/reporting. The findings may contribute to positive social change by providing insights for small- and medium-sized oil and gas business leaders on strategies for managing inactive assets and for fostering an environmental culture among employees that has beneficial impacts on their families and communities.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / MudanÃas climÃticas na escala de tempo de sÃculos ou dÃcadas podem produzir variaÃÃes ecolÃgicas significativas, alterando os cenÃrios naturais do globo terrestre, assim como, comprometer o bem estar do homem e de outros seres vivos no planeta, por isso, torna -se importante estudar as evoluÃÃes climÃticas durante o perÃodo QuaternÃrio, pois se conhecido as alteraÃÃes do clima no passado recente pode-se, com mais seguranÃa, determinar as condiÃÃes futuras. Os campos de dunas eÃlicas inativas, com extensÃes regionais, tÃm sido considerados como indicadores geomorfolÃgicos e sedimentolÃgicos de mudanÃas paleoclimÃticas durante o QuaternÃrio. A zona costeira do estado do MaranhÃo à dona de um dos maiores registros eÃlicos da costa brasileira. Nela estÃo inseridos os corpos dunares mÃveis (LenÃÃis Maranhenses) e dunas inativas (fÃsseis) adjacentes, cuja Ãrea està em torno de 1.000.000 hectares. O trabalho consiste em realizar um estudo da evoluÃÃo destes corpos dunares, fazer uma relaÃÃo cronolÃgica dos diferentes tipos de dunas a fim de moldar as condiÃÃes climÃticas e paleoambientais pretÃritas e mostrar a atual situaÃÃo destes depÃsitos, bem como a interaÃÃo dos mesmos com outros ecossistemas, atravÃs de tÃcnicas de geoprocessamento aplicadas em imagens de sensoriamento remoto dos satÃlites Landsat 5, Landsat 7, QUICKBIRD, imagens de radar da missÃo SRTM, levantamentos de campo e anÃlises em laboratÃrio de sedimentos. A Ãrea possui pelo menos trÃs compartimentos de relevo, cada um com seu ecossistema ou unidade geoambiental correspondente e padrÃes de drenagem caracterÃsticos. Dividida em quatro estÃgios, a evoluÃÃo dos depÃsitos eÃlicos comeÃa, por volta de 123 mil anos antes do presente (A.P), Ãpoca correspondente ao mÃximo da penÃltima transgressÃo, quando o mar erodiu total ou parcialmente os depÃsitos continentais de estÃgios anteriores. As dunas deste estÃgio sÃo atualmente de cor avermelhada tÃpicas dos tabuleiros prÃ-litorÃneos e nÃo apresentam forma definida. O segundo estÃgio se encaixa nas evidÃncias da glaciaÃÃo ocorrida entre 70 e 60 mil anos A.P. O mar estava em nÃveis muito mais baixos do que o atual, disponibilizando material suficiente para a formaÃÃo de dunas. Um grande deserto de areia teria se formado. Estas dunas mÃveis do Pleistoceno sofreram processos de estabilizaÃÃo posteriormente no terceiro estÃgio, e hoje sÃo as dunas vegetadas que encontramos na Ãrea estudada. O quarto estÃgio à marcado pelo aparecimento das dunas mÃveis dos LenÃÃis Maranhenses que continuam a migra atualmente. As mudanÃas climÃticas e ambientais ocorridas durante o QuaternÃrio estÃo intrinsecamente ligadas à gÃnese e evoluÃÃo dos depÃsitos arenosos deste perÃodo, tomando como evidÃncia suas caracterÃsticas sedimentolÃgicas e sua disposiÃÃo morfolÃgica atual no espaÃo. / Climate change covering centuries or decades can produce important ecological variations altering the Earth natural scenarios, as well as, endangering human welfare and others being livings. For this reason, itâs important to study climatic evolutions during Quaternary, since trough the knowledge the weather conditions in the past we can anticipate future conditions. The inactive aeolian dune fields regionally distributed, are considered sedimentologic and geomorphologic indicators of paleoclimatic changes during Quaternary. The MaranhÃo state coast shows perhaps the greatest aeolian record of Brazilian littoral which includes active dune fields (LenÃÃis Maranhenses) inactive dunes (fossil) covering a 1,000,000 hectares surface. It was held in this dissertation a dunar evolution study, setting up the several dunes types formation chronology, climatic and paleoenvironmental conditions through remote sensing techniques using Landsat 5, Landsat 7, Quickbird and radar SRTM satellites images, field survey and laboratory analysis. The region morphology is composed of three types of relief: dune bodies (active and inactive), pre-coastal tabuleiros and dissect tabuleiros. Linear structures that occur in this region are responsible for morphologic features and control the hydrographic patterns: parallel, rectangular, dendritical and contorted. There are four evolution phases that correspond to the formation of aeolian deposits. The first one was formed 123.000 years B.P. during the highest of Last Transgression, when the sea eroded total or partially the ancient continental sediments. These dunes now have a reddish tint and they have lost the original form. The second phase has been developed during glaciations between 70 and 60 years B.P. and sea level was lower than the actual, providing sediments to produce a sand desert. These active dunes from Pleistocene were, subsequently fixed that correspond to the third phase. The last one is marked by the active dunes (LenÃÃis Maranhenses) that keep on moving. Climatic and environmental changes during Quaternary are related to the genesis and evolution of Aeolian sand deposits, according to the regional dunes sedimentology and morphology

No description available.