• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 19
  • 18
  • 4
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 55
  • 10
  • 9
  • 7
  • 7
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Estado nutricional relativo ao zinco de crianças de duas comunidades ribeirinhas amazônicas, na cidade de Porto Velho - RO / Nutritional status on the zinc of children from two Amazonian riverines communities, in Porto Velho RO.

Rafael Barofaldi Bueno 09 April 2009 (has links)
Estudos epidemiológicos na Região Amazônica são escassos, principalmente aqueles que fazem diagnósticos do estado nutricional relativo a micronutrientes populações que vivem em comunidades ribeirinhas isoladas. Portanto, este estudo objetivou avaliar o estado nutricional relativo ao zinco de crianças em duas comunidades ribeirinhas da Cidade de Porto Velho RO: Gleba do Rio Preto e Demarcação. Foram avaliadas 39 crianças entre 3 e 9 anos, destas 29 da Demarcação e 10 da Gleba do Rio Preto. O perfil sócio-econômico mostrou que todas as famílias avaliadas não tinham destino adequado para os dejetos, as únicas fontes de água eram os rios ou poços cacimba e a principal fonte de renda era a cultura de subsistência, fornecendo renda mensal inferior a um salário mínimo. A avaliação do consumo alimentar mostrou que 39% das crianças avaliadas tinham ingestão de zinco inferior a EAR, a adequação calorica mostrou que 50% das crianças avaliadas tinham ingestão calórica inferior a 90%, no entanto, 92% das crianças tinham ingestão adequada de proteínas. A avaliação antropométrica, de acordo com o escore Z, mostrou que 92%, 84% e 86% das crianças estavam eutróficas para os padrões Estatura/Idade, Peso/Estatura e Peso/Idade, respectivamente. Na avaliação da concentração de zinco no plasma foi observada uma prevalência de deficiência em 90% dos casos e a concentração do zinco eritrocitário mostrou 71% de deficiência. Assim, pode-se concluir que o estado nutricional relativo ao zinco é grave, visto que a ingestão e as concentrações deste nutriente nos parâmetros avaliados estão reduzidas na maioria da população avaliada. / Epidemiological studies in Amazon Region are rarely, especially those that evaluated micronutrients nutritional status on isolated communities. This study aimed to evaluate zinc nutritional status from children who lives in two riverine communities from Porto Velho City RO; Gleba Rio Preto and Demarcação. We carried out of 39 children (3 to 9 years old). The economical and social profile showed that all families had no appropriate dejections destination, the waters sources were from well and rivers and the main source income were from subsistence culture. The food assessment showed 39% from evaluated children had no adequate zinc intake according EAR, the calorie intake was inadequate on 50% from evaluated children. The anthropometrics evaluation showed, according Z score, 92%, 84 e 86% of children were eutrophics to the standards Height/Age, Weight/Height and Weight/Age, respectively. The assessment of zinc concentrations on serum showed a prevalence of deficiency in 90% of the evaluated cases, and the zinc concentration on erythrocytes showed 71% of deficiency and 21% of normality in the evaluated children. Thus, we can conclude the nutritional status is severe, therefore the zinc intake and zinc concentrations are reduced in majority assessed population.
32

Sítio Moraes, uma biografia não autorizada: análise do processo de formação de um sambaqui fluvial / The Moraes site, an unauthorized biography. Formation process analysis of a riverine shellmound

Cláudia Regina Plens 15 February 2008 (has links)
Pesquisas recentes apontam para o fenômeno construtivo de sambaquis fluviais na região do médio Vale do Ribeira de Iguape, São Paulo, mais precisamente em três regiões, Itaoca, bacia do rio Jacupiranguinha e bacia do Juquiá, durante, pelo menos, o período de 9000 anos. O presente trabalho tem por objetivo definir o perfil de um sambaqui fluvial, sítio Moraes (6000-4000 anos a.P.), no município de Miracatu, SP, com a finalidade de criar a compreensão intra-sítio dos processos formativos envolvidos para a elevação desta estrutura monticular, através de diferentes abordagens: distribuição espacial intra-sítio, tecnologia, subsistência, isótopos estáveis, estudo sedimentológico e análise de proporção componencial volumétrico. Os resultados destas análises associados aos dados advindos de outras pesquisas nos permitiram ampliar a discussão sobre o processo formativo do sítio Moraes e abordar a questão sobre as relações genética e cultural entre sambaquieiros fluviais e os demais grupos vizinhos. / Previous research at the Ribeira de Iguape valley, at the southern part of the State of São Paulo, Brasil, has revealed a long cultural sequence (ca. 11 to 1,2 kyBP) characterized by small shellmound sites generally designated as riverine, or fluvial, sambaquis. Besides the conspicuous presence of a terrestrial gastropod (Megalobulimus sp.) shells, these little mounds also share relevant amounts of human burials and similar technological patterns as regards lithic and bone industries, among other compositional elements. The principal aim of this thesis is to describe one of these mounds, Moraes, investigating the cultural and post-depositional formation processes implied on the long duration (6 to 4 kyBP) construction phase of such mound structure and after its abandonment, by means of zooarchaeological, technological, geochemical and isotopic analysis of its various deposits and cultural components therein, as well as their spatial distribution and articulation. This thesis also discusses the cultural and historical relationships of this fluvial shellmound culture with other cultural patterns and populations found at the same and nearby areas.
33

Abundance of <i>Archaias angulatus</i> on the West Florida Coast Indicates the Influence of Carbonate Alkalinity over Salinity

Beckwith, Sean Thomas 19 October 2016 (has links)
Archaias angulatus, a large symbiont-bearing foraminifer (Order Miliolida) that produces a Mg-calcite shell, is common throughout the Caribbean and warm western Atlantic region. This species lives abundantly in seagrass beds along the Springs Coast of northwest Florida (up to 4 adults per gram of sediment) where spring-fed rivers emerge from a limestone aquifer, and in Florida Bay to the southeast (25 adults/g) where the sediment is primarily biogenic carbonate. In contrast, live specimens are seldom found in the seagrass beds along the central-west coast of Florida, where barrier islands are dominated by quartz sand. My working hypothesis is that substratum and carbonate chemistry, in addition to temperature and salinity, explain differences in abundance of A. angulatus associated with the seagrass meadows along the west Florida coastline and shelf. Water chemistry measurements were taken diurnally over 1-2 day periods at four sites in winter, spring and autumn of 2015. Salinity and temperature were measured in situ, and sealed bottles of seawater were transported to the laboratory for analysis of Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA). The highest TA was found in the Springs Coast (2766 μmol/kg-seawater, three-season average), along with the lowest salinities, which reveals a strong contribution from the nearby rivers, springs and seeps. A TA end-member regression analysis predicts, and sampling confirms, TA increases with proximity to the river mouth, highlighting the atypical relationship between alkalinity and salinity in this carbonate province. A gradient in the value of TA was seen among the northern three sites, with TA decreasing from the Springs Coast site southward to Fort Desoto; additionally, the pH and calcium carbonate saturation states were higher at the northernmost sites. The highest ratio of TA to DIC among all four sites was found at the southern edge of the Springs Coast, reflecting strong primary production and DIC uptake by the dense meadows of seagrass in the area. A daytime increase in the TA to DIC ratio was seen at all sites; however, the Springs Coast site (~5km from the Weeki Wachee river mouth) exhibited stronger tidal influences on TA and DIC than diurnal influences. Plots of salinity-normalized TA and DIC indicate the Weeki Wachee coastal area is impacted by calcification and dissolution to a greater extent than by photosynthesis and respiration. The gradual relief off the Springs Coast, as well as clarity of the water column, provide ideal physical habitat, and the input from spring-fed sources enhances the water chemistry for calcifying organisms. Presence of A. angulatus in low salinity waters influenced by high alkalinity riverine discharge led to a new hypothesis that calcification in A. angulatus requires high carbonate alkalinity but not necessarily full marine salinity.
34

Influence of Experimental Sheet Flow on Aquatic Foods Webs of the Central Everglades

Bornhoeft, Sarah C. 01 July 2016 (has links)
Establishing historical water velocities is a goal of Everglades restoration because of their role maintaining landscape topographic relief. However, flows may also change the trophic state of marshes by phosphorus loading. I used fatty acid (FA) and stoichiometric data to quantify how increased sheet flow altered the relative heterotrophic and autotrophic contributions to aquatic consumers in a field experiment that introduced flowing water to an Everglades marsh in November, 2014. Algal taxonomic composition was different between pre-flow and flow sampling, marked by increases in the nutrient exploiting Mougeotia species (green algae) during flow sampling. Dietary tracer FAs in consumers reflected changes in algal resources, including an increase in green algae-derived and a decrease in bacteria-derived FAs. These food web responses indicate that establishing historic water velocity in degraded wetlands can shift the origins of organic matter from a more detrital to more algal supported web.
35

Comparing hypotheses proposed by two conceptual models for stream ecology

Collins, Sean E. 27 October 2014 (has links)
No description available.
36

GULF OF MAINE LAND COVER AND LAND USE CHANGE ANALYSIS UTILIZING RANDOM FOREST CLASSIFICATION: TO BE USED IN HYDROLOGICAL AND ECOLOGICAL MODELING OF TERRESTRIAL CARBON EXPORT TO THE GULF OF MAINE VIA RIVERINE SYSTEMS

Mordini, Michael B. 14 August 2013 (has links)
No description available.
37

Modeling fine sediment behavior in gravel-bed rivers

Lamparter, Gabriele Johanna January 2014 (has links)
Fine-grained sediment accumulation in the interstices of gravel beds is a key factor in degrading riverine habitats. However, interstitial deposits are highly dynamic and are not sufficiently understood. This work enhances the understanding of interstitial fine sediment deposition by investigating interstitial storage and ingress, flow, suspended sediment and gravel bed character. Furthermore, this work introduces a numerical suspended sediment deposition model with the power to predict patterns of interstitial ingress. The investigation of interstitial deposition were carried out on two levels. Both data orginating from flume experiments and from three locations of the River Culm, Devon, UK was collected. The experimental data showed the significant influence of small scale variations in flow and bed character and their influence on interstitial ingress. The field investigation showed clear differences in interstitial fine-grained sediment for the different river reaches and an overall higher interstitial ingress compared to recent published data. The numerical model development was realised in a two-step approach. First, the model was coded and calibrated for the flume scale processes and, second, an upscaled reach scale model was devolped for the field data. This reach scale suspended sediment deposition model included flow information, for which depthaveraged two dimensional hydrodynamic models were developed with the software Delft3D. The overall explanatory power of the model at this state is not satisfactory with regards to local deposition distribution. A separate chapter discusses the possible causes and implications of this short coming for further research from a data aquisition and modelling perspective.
38

Ekologie, etologie a variabilita ještěrky zelené, Lacerta viridis v Přírodní rezervaci Tiché údolí / Ecology,ethology and variability of european green lizard Lacerta viridis in Natural reservation Tiché údolí

Chmelař, Jan January 2014 (has links)
The European green lizard, Lacerta viridis, is in the Bohemia region stated as critically endangered species. Populations in this region are located beyond the northern border of continuous range of this species and are closely related to the "riverine phenomenon", and deeply engorged river valleys. The chosen locality in Tiché údolí is a subject to a long-term conservational management aimed to strengthen and maintain abundance of the local population. This management is a direct output of a previous study of this population performed in years 1995-1997. Main goal of the presented study is to compare current population characteristics with the older study. The locality has been visited 119 times in years from 2011 to 2014. The studied population now displays higher abundance and inhabits a larger area. The author also performed a spatial analysis of the places with presence of an observed individual in order to determine and evaluate significance of the chosen abiotic factors for habitat discrimination. The results indicate that positive discrimination is based on the presence of a rock debris and a hiding place. Strongest factors towards negative discrimination were high percentages of grass and high vegetation coverage. This study also contains and discusses ecological, ethological and...
39

Estado nutricional relativo ao selênio de crianças residentes em duas localidades de Rondônia, Amazônia Ocidental / Selenium nutritional status of children living in two places from Rondônia State, Western Amazon

Rocha, Ariana Vieira 31 March 2009 (has links)
Estudos sobre o estado nutricional da população de Rondônia são escassos, principalmente nas localidades ribeirinhas mais isoladas. Estas populações estão expostas a vários fatores ambientais que podem interferir no seu estado nutricional. Portanto, o objetivo principal deste estudo foi avaliar o estado nutricional relativo ao selênio de crianças ribeirinhas de 3 a 9 anos de idade residentes nas localidades de Demarcação, no Rio Machado e Gleba do Rio Preto, no Rio Preto. O método utilizado para avaliação do selênio foi a espectrometria de absorção atômica por geração de hidretos acoplada à cela de quartzo (HGQTAAS). Das 42 crianças estudadas, 74% pertenciam à localidade Demarcação e 26% à Gleba do Rio Preto. De acordo com os pontos de cortes estabelecidos para antropometria, a maioria das crianças das duas localidades apresentou eutrofia. Em relação aos níveis de selênio no plasma, 84% das crianças de Demarcação apresentaram concentrações abaixo do valor de referência, e 16% apresentaram concentrações normais. Por outro lado, as crianças da Gleba do Rio Preto apresentaram concentrações elevadas e acima dos valores de referência estabelecidos. Nos eritrócitos. 45% das crianças residentes na Demarcação apresentaram concentrações baixas do mineral e as demais, níveis normais. Na Gleba, 45% apresentaram concentrações normais e as demais, concentrações acima dos valores de referência. O consumo médio de selênio em Demarcação foi de 41,8&#181;g/dia e na Gleba do Rio Preto, de 179,0&#181;g/dia. Houve correlação significativa apenas entre o consumo de selênio e a concentração deste elemento nos eritrócitos, nas crianças de Demarcação. Desta maneira, conclui-se que as crianças estudadas apresentaram diferenças em relação ao estado nutricional para selênio, as crianças de Demarcação apresentando um estado entre deficiência e normalidade, e as da Gleba do Rio Preto, sujeitas a um possível risco de excesso com possibilidade de efeitos adversos. As concentrações de mercúrio nos cabelos das crianças e em peixes da região foram determinadas por espectrometria de absorção atômica com geração de vapor frio (CV AAS), visando estudar a interação deste elemento com o selênio, e os resultados confirmaram esta possível relação. A maioria das crianças de ambas as localidades apresentou níveis elevados deste metal nos cabelos, assim como foram elevadas as concentrações nos peixes da região. As crianças da Gleba do Rio Preto apresentaram níveis superiores às de Demarcação. / Studies about the nutritional status of population from Rondônia State are scarce, mainly at more isolated riverine places. Populations from these communities are exposed to several environmental factors that interfere in the nutritional status. Thus, the aim of this study was to evaluate the selenium nutritional status of riverine children aged between 3-9 years from Demarcação, placed at Madeira River, and from Gleba do Rio Preto, placed at Rio Preto River. The selenium was analyzed by hydride generation (quartz cell) atomic absorption spectrometry (HGQTAAS). From the 42 evaluated children, 74% of them resided at the first community and the others, at the second one. According to the established cut-offs for anthropometry, the most part of the children from both places were eutrophic. In relation to the plasma selenium levels, 84% of the children from Demarcação presented low levels, while the others 16% had normal levels. On the other hand, all children from Gleba do Rio Preto presented high plasma selenium levels, exceeding the established reference values. In the case of the erythrocyte levels, the percentage of normal and low selenium concentrations in those children from Demarcação was 55% and 45%, respectively. At Gleba do Rio Preto there were high selenium erythrocyte levels in 55% of the children. The mean selenium intake from diet was 41.8 &#181;g/day at Demarcação, and 179.0 &#181;g/day at Gleba do Rio Preto. There was a significant correlation only between the selenium ingested by diet and the erythrocyte selenium levels in those children from Demarcação. Taking the results together, it is possible to conc1ude that the studied children presented differences in relation to the selenium nutritional status with those from Demarcação showing a status between deficiency and normality, and those from Gleba do Rio Preto, a possible risk of excess, being liable to adverse effects. The hair and fishes mercury concentrations were determined intending to study the interaction between this metal with selenium, and the obtained results corroborated this possible relation. The great majority of the children from both places showed high hair mercury levels, as well as the fishes of that region. Children from Gleba do Rio Preto presented higher levels than those from Demarcação.
40

Ecodynamique des substances poly- et perfluoroalkylées (PFAS) dans les systèmes aquatiques : identification des sources en milieu urbain et évaluation du transfert trophique / Environmental fate of poly- and perfluoroalkyl substances (PFAS) in aquatic systems : identification of urban sources and trophic transfer assessment

Simonnet-Laprade, Caroline 19 December 2017 (has links)
Les activités humaines sont responsables de l’apport de nombreux micropolluants vers les systèmes aquatiques parmi lesquels les substances poly- et perfluoroalkylées (PFAS) ont été identifiées. Ces molécules sont utilisées depuis les années 1950 comme tensio-actifs dans de nombreuses applications industrielles et produits d’usage courant. Depuis deux décennies, certaines de ces substances, les acides perfluoroalkylés (PFAA) ont particulièrement attiré l’attention en raison de leur caractère ubiquiste et persistant dans l’environnement. Actuellement, il existe un réel manque de connaissance sur l’intégralité de la contamination environnementale par l’ensemble des PFAS. L’objectif global de ces travaux de thèse est de poursuivre les efforts menés depuis le début des années 2000 pour mieux comprendre la dynamique des PFAS depuis leurs sources en milieu urbain, leurs rejets dans les rivières et leur transfert trophique.La première partie consiste à optimiser une configuration de l’échantillonneur passif POCIS (Polar Organic Chemical Integrative Sampler) pour l’analyse ultra-trace de 25 PFAS dans les eaux de surface. Dans un second temps, il est question d’identifier les sources en PFAS sur la métropole de Bordeaux. L’analyse de 30 PFAS dans les eaux usées collectées en raiseau d’assainissement tend à montrer l’importance des apports industriels par rapport aux rejets domestiques pour la quasi-totalité des PFAS étudiés. A noter que les eaux de ruissellement sont également vectrices de contamination en PFAS. La caractérisation des effluents d’entrée et de sortie des quatre principales stations d’épuration des eaux usées (STEU) de la métropole met en évidence une faible efficacité des filières de traitement. L’utilisation d’une approche d’analyse non ciblée par oxydation, la méthode TOP (Total Oxidizable Precursors) révèle des quantités non négligeables de précurseurs de PFAA aussi bien en réseau d’assainissement que dans les effluents de STEU. L’impact de l’exutoire collectant les eaux de ruissellement en provenance de l’aéroport et d’une portion du périphérique de Bordeaux sur les niveaux en PFAS d’une petite rivière périurbaine est également montré. Enfin, la dernière partie renseigne la bioamplification des PFAS en milieu lotique. L’évaluation des concentrations le long de 5 réseaux trophiques du bassin hydrographique Rhône-Méditerranée permet d’une part de confirmer la bioamplification du perfluorooctane sulfonate (PFOS) et des perfluoroalkyles carboxylates (PFCA) à chaîne longue, et d’autre part d’évaluer la variabilité spatiale des facteurs d’amplification trophique (TMF). Le caractère bioamplifiable de PFAS d’intérêt « plus émergent » tels que les 8:2 et 10:2 fluorotélomères sulfonates est mis en évidence dans une rivière localisée à la périphérie de Paris. L’application de la méthode TOP à différents maillons de cette chaîne trophique permet de soutenir l’hypothèse de l’implication de la biotransformation des précurseurs dans la bioamplification apparente des PFAA. / Human activities are responsible for the release of multiple micropollutants into aquatic systems, such as poly- and perfluoroalkylated substances (PFASs). These molecules have been used since the 1950s as surfactants in many industrial applications and commonly used products. For two decades, some of these substances, perfluoroalkylated acids (PFAA), have generated a major concern due to their ubiquitous and persistent behavior in the environment. Currently, there is a real lack of knowledge about the full extent of environmental contamination by all PFASs. The overall objective of this thesis is to continue the efforts undertaken since the early 2000s to gain a better understanding of the dynamics of PFASs, from their sources in urban areas, their releases to aquatic systems, to their trophic transfer.The first part consisted in optimizing a configuration of the Polar Organic Chemical Integrative Sampler (POCIS) for the ultra-trace analysis of 25 PFASs in surface water. In a second time, the dynamics of the PFASs on the Bordeaux conurbation is studied. The analysis of 30 PFASs in wastewater collected in the sewerage network tends to show the importance of industrial inputs compared to domestic discharges for almost all the studied PFASs. Note that urban runoff is also a source of PFAS contamination. The characterization of the influents and effluents of the four main wastewater treatment plants (WWTP) in the metropolis shows a low efficiency of treatment channels. The use of a non-targeted analysis approach by oxidation, the TOP method (Total Oxidizable Precursors) reveals significant amounts of PFAA precursors in the sewerage network as well as in WWTP effluents. The impact of urban and airport storm water discharge on the contamination levels of a small peri-urban river has also been shown. The last part dealt with the biomagnification of PFASs in lotic systems. The evaluation of PFAS concentrations along 5 food webs from the Rhone-Mediterranean watershed enables to confirm the biomagnification of perfluorooctane sulfonate (PFOS) and long-chain perfluoroalkyl carboxylates (PFCA) and to evaluate the spatial variability of trophic magnification factors (TMF). The biomagnification character of PFASs of "more emerging" interest, such as the 8:2 and 10:2 fluorotelomer sulfonates, is observed in a river located on the outskirts of Paris. The application of the TOP method to different trophic levels supports the hypothesis of the involvement of the biotransformation of precursors in the apparent biomagnification of PFAAs.

Page generated in 0.1038 seconds