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Poor food quality can have large negative effects on zooplankton growth and this can also affect food web interactions. The main aims of this thesis were to study the importance of different food quality aspects in Daphnia, to identify potentially important differences among zooplankton taxa, and to put food quality research into a natural context by identifying the importance of food quality and quantity in lakes of different nutrient content. In the first experiment, the RNA:DNA ratio was positively related to the somatic growth rate of Daphnia, supporting a connection between P content, RNA content, and growth rate. The second experiment showed that EPA was important for Daphnia somatic growth, and 0.9 µg EPA mg C-1 was identified as the threshold below which negative effects on Daphnia growth occurred. A field survey identified patterns in the PUFA content of zooplankton that could be explained by taxonomy and trophic position. Cladocera enriched EPA and ARA relative to seston, and Copepoda primarily enriched DHA. In a whole-lake experiment, gentle fertilization of an oligotrophicated reservoir increased the seston P content and the biomass of high quality phytoplankton (Cryptophyceae, high EPA content). This was followed by increases in zooplankton and fish biomasses. An empirical model based on data from a literature survey predicted that food quantity is most important for zooplankton growth in oligotrophic lakes, and that food quality factors are more important in eutrophic lakes. Thus, zooplankton growth, and energy transfer efficiency in the food web, is predicted to be highest in mesotrophic lakes. The results predict that the strength and nature of food quantity and quality limitation of Daphnia growth varies with lake trophic state, and that some combination of food quantity and/or quality limitation should be expected in nearly all lakes.

published_or_final_version / Education / Doctoral / Doctor of Philosophy

v angličtině Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Pharmacology & Toxicology Student: Michela Morkusová Supervisor: Přemysl Mladěnka, Pharm.D., Ph.D. Title of diploma thesis: Chelation ability of experimentally used iron chelators Iron is a vital element, playing many important functions in the body. Its presence in too low or too high quantities is harmful. The body has no excretion route for iron, and in certain circumstances, excess iron can accumulate in body tissues. Iron is present in the body in excess particularly in individuals undergoing frequent blood transfusions or having genetically based diseases associated with iron overload (hemochromatosis). Iron excess is medically treated by administration of iron chelators. Such substances can find wider therapeutic use as well, e.g. in individuals with acute myocardial infarction or with tumours. This Thesis was aimed at determining the stoichiometric ratio in the complexes of two experimental chelators, salicylaldehyde isonicotinoyl hydrazone (SIH) and ethylenediaminetetraacetic acid (EDTA), with iron(II) and iron(III) ions at four different pathophysiologically significant pH levels (4.5, 5.5, 6.8 and 7.5). Spectrophotometry was used as the analytical method. In the processing stage, various new...

Le silicium est le matériau de prédilection de l'industrie de la microélectronique. L'augmentation du coût de celui-ci a donc incité les différentes industries à optimiser l'utilisation des plaquettes de silicium. La réutilisation de plaquettes (recyclage) est donc devenue monnaie courante : c'est le cas des plaquettes tests ou des plaquettes de type SOI. Le recyclage présente cependant des limites, en effet, au cours des cycles la qualité des plaquettes diminue plus ou moins rapidement. La compréhension des mécanismes de la dégradation des plaquettes lors de cycles de procédés est donc un enjeu important. Les procédés de recuit haute température sont connus pour être à la fois les plus répandus et les plus dégradants. Pour comprendre quels sont les phénomènes mis en jeu lors de tels cycles, un panel d'échantillons a subi différents nombres de cycles et a été étudié par diverses techniques. Le LST et la microscopie électronique en transmission ont tout particulièrement été utilisés, couplant ainsi des mesures globales de densités et dimensions de défauts à des mesures locales permettant de caractériser la nature des défauts et leur comportement à l'échelle nanométrique. L'évolution de la concentration en oxygène interstitiel dans le matériau, liée à la précipitation d'oxyde de silicium, a été mesurée par IRTF. Il a ainsi été montré que chaque cycle consistait en une étape de nucléation de défauts, principalement des précipités d'oxyde de silicium, et une étape de grossissement. La détermination de la morphologie, ainsi que de la stoechiométrie des précipités a été réalisée. / Silicon is the prefered material of the Microelectronics industry. The increase of its cost incited the industries to optimize the use of wafers. Recycling them thus became current : it is the case for test wafers or SOI wafers. However, recycling presents limits : during the cycles, wafers quality decreases more or less quickly. Impact of process cycles on wafers quality is thus very important. High-temperature annealing is the most detrimental process. To understand what phenomena are involved during annealing cycles, samples which have been cycled were studied by differents techniques. LST and TEM were quite particularly used, coupling global measurements of defects density and size with local measurements to determine defects characteristics. Interstitial oxygen loss during cycles were measured by FTIR. We found that every cycle is composed by a defects nucleation stage, mainly precipitates of silicon oxide, and a growth stage. The determination of morphology and precipitates stoichiometry was realized. The behavior of these precipitates was described by a model taking into account various phenomena : oxygen loss, point defects distribution and cycles effects (ramp up/down and high-temperature stage). The robustness of the model was also tested by comparing the predictions made with the results taken from the bibliography.

É sabido que o ensino de ciências no Brasil está entre os piores do mundo. Atualmente, a sociedade discute com bastante frequência este quadro: pensam-se as razões que levam a educação a estar tão defasada, e o que leva os estudantes a não gostarem da disciplina de Química. Uma dessas razões pode ser a forma como os conteúdos são passados para os discentes, a qual muitas vezes é descontextualizada e nada atrativa. As histórias em quadrinhos têm sido utilizadas como instrumento didático de aprendizagem em diferentes áreas no ensino médio, no entanto na área da química, ainda são pouco usadas. Baseado nisso o presente trabalho tem como objetivo desenvolver um estudo de caso elaborando uma revista em quadrinhos para explicar o conteúdo de estequiometria a alunos do segundo ano do ensino médio. A hipótese é de que a revista em quadrinhos, por ter um caráter lúdico, possa facilitar a aprendizagem do conteúdo. Primeiramente foi criada a revista, depois foi realizado um estudo de caso em uma escola estadual em Gravataí/RS, onde participaram da atividade utilizando a revista, 60 alunos de três turmas do segundo ano do ensino médio. A avaliação foi realizada por meio de prétestes e pós-testes e com o uso de questionários com perguntas abertas e fechadas, sendo que as respostas foram categorizadas sob um enfoque quantitativo. Os resultados encontrados mostraram que os estudantes ficaram motivados com a atividade e tiveram um maior entendimento do conteúdo quando utilizaram a revista em quadrinhos, sendo que 26% dos estudantes melhoraram suas respostas em frente ao conteúdo abordado. Além disso, observou-se que cerca de 25% compreenderam melhor os conceitos e os cálculos estequiométricos. Sendo assim, acredita-se que a revista em quadrinhos possa ser uma boa estratégia de ensinoaprendizagem para o ensino de Química. / It is a known fact that science education in Brazil is among the worst in the world. Nowadays, society often discusses this situation and considers the reasons why education is so outdated and why students do not like the subject of chemistry. One reason may be the method used to teach the subject matter, which is often decontextualized and unattractive. The hypothesis was that the comic book, due to its ludic character, might facilitate the understanding of this subject. First the comic book was created; then a case study was done at a state school in Gravataí/RS, where 60 students from three groups in the second year of high school participated in the activity. The evaluation was done through pretests and posttests and using questionnaires with open- and closed-ended questions, classifying the answers with a quantitative focus. The results showed that the students were motivated by the activity and had a better understanding of the subject when they used the comic book, with 26% of the students improving their answers about the subject matter. It was also observed that 25% of the students better understood the concepts and the stoichiometric calculus. Thus, we believe that comic books may be a good teachinglearning strategy for the study of chemistry.

Submitted by Maria Bernadete Dos Santos (mariabpds@id.uff.br) on 2017-09-19T14:18:34Z No. of bitstreams: 3 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Daniele.pdf: 6867436 bytes, checksum: ebb98bac0dc5447f8a1ae1479cfb7fdf (MD5) Produto Daniele.pdf: 1546415 bytes, checksum: 8128b223f9179e54cfa94a90746ab57c (MD5) / Approved for entry into archive by Biblioteca Central do Valonguinho Biblioteca Central do Valonguinho (bcv@ndc.uff.br) on 2017-09-20T20:07:08Z (GMT) No. of bitstreams: 3 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Daniele.pdf: 6867436 bytes, checksum: ebb98bac0dc5447f8a1ae1479cfb7fdf (MD5) Produto Daniele.pdf: 1546415 bytes, checksum: 8128b223f9179e54cfa94a90746ab57c (MD5) / Made available in DSpace on 2017-09-20T20:07:08Z (GMT). No. of bitstreams: 3 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Daniele.pdf: 6867436 bytes, checksum: ebb98bac0dc5447f8a1ae1479cfb7fdf (MD5) Produto Daniele.pdf: 1546415 bytes, checksum: 8128b223f9179e54cfa94a90746ab57c (MD5) / Esta pesquisa foi elaborada pensando nas dificuldades que os alunos apresentam na aprendizagem dos conteúdos de Química e nas causas que fazem com que essas dificuldades sejam tão comuns e recorrentes. A Teoria da Aprendizagem Significativa proposta por David Ausubel afirma que o aluno aprende de forma efetiva quando o conhecimento prévio sobre determinado assunto é substituído pelo novo saber, proporcionando a construção do conhecimento de uma forma significativa para o aluno. Dessa forma criou-se de um recurso didático constituído por histórias fictícias vividas por dois adolescentes em fase escolar. O enredo e os personagens foram desenvolvidos pela autora com o objetivo de criar um ambiente propício para a aprendizagem de forma que os alunos pudessem se identificar com os personagens buscando a motivação pelo estudo. O tema escolhido para essa narrativa foi Estequiometria e sua abordagem se deu através do cotidiano vivenciado pelos personagens Nitrilla e Rutherfórdio. Essa narrativa que recebeu o título “Desvendando o mundo da Estequiometria” foi utilizada durante todo o mês de outubro de 2013, em um colégio de aplicação localizado no Estado do Rio de Janeiro, em todas as três turmas da 2º série do Ensino Médio computando 78 alunos no total. As avaliações dos alunos através de questionário e opinião permitiram alterações que contribuíram para aperfeiçoamento do produto final. A avaliação da aprendizagem ocorreu de forma continuada através da investigação dos conhecimentos prévios, da participação em aula, da habilidade demonstrada na resolução de exercícios e prova final. Assim, foi possível verificar que o material didático aqui desenvolvido apresentou um grande potencial significativo, pois ao trabalhar o conteúdo de uma forma lúdica através das situações do dia-a-dia motivou a aprendizagem dos alunos e consequentemente melhoria no desempenho das turmas. / This research has been prepared in relation to the difficulties that students have in learning Chemistry. The causes that generate these difficulties are common and recurring. The Theory of Meaningful Learning proposed by David Ausubel states that students learn effectively when the prior knowledge of the issue is replaced by new knowledge, providing the construction of knowledge in a meaningful way for the student. Thus, was created a teaching resource consisting of fictional stories experienced by two teenagers of school age. The plot and characters were developed by the author in order to create a conducive environment for learning, só that students could identify with the characters, thereby providing motivation for the study. The theme chosen for this narrative was Soichiometry and his approach was detailed through the daily routine experienced by the characters Nitrilla and Rutherfordium. This narrative titled "Uncovering the world of Stoichiometry" was used throughout the month of October, 2013, in a school located in the State of Rio de Janeiro. It was used in all three classes of second year in the high school, with a total of 78 students participating overall. The evaluation of students opinions through the questionnaire led to changes that contributed to an improvement of the final product. The evaluation of learning occurred continuously, through the investigation of their previous knowledge, class participation, demonstrating their ability in problem solving and a final exam. Thus, we observed that the teaching materials developed here had great significant potential, as the work content, when done in a playful way, daily,motivated student learning and consequently improved the performance of the group.

Climate change is predicted to impact organismal nutritional ecology. Increased temperatures can directly accelerate physiological rate processes, which in turn, impact nutritional requirements. Climate change can also impact organisms indirectly by altering the quality and quantity of nutritional resources, creating the potential for nutritional mismatch between what nutrients are available in the environment and what organisms require. Investigation of organismal stoichiometry, particularly the balance of carbon, nitrogen, and phosphorus content of organisms, can help illuminate the extent to which changes in climate may impact organism nutritional ecology. Ants represent an excellent system to examine stoichiometry because they occur across a broad range of environmental conditions and perform important ecosystem services, such as seed dispersal, which may impact ecosystem functioning. In this thesis, I examined how climate variables influence ant stoichiometry across a broad latitudinal gradient in natural populations of three closely-related ant species in the genus Aphaenogaster. In a common garden study, I tested the extent to which such stoichiometric variation was due to plastic or evolved variation. I found significant species-specific differences in how ant stoichiometry responded to climate gradients. The northern species, A. picea contained more C, and less N and P at higher latitudes and elevation, consistent with increased winter lipid storage. In contrast, the more southern species, A. rudis, showed the opposite pattern, which may reflect N and P limitation at southern extremes. Aphaenogaster fulva, whose range is intermediate in latitude and partially overlaps with both congeners, contained more C in environments with more seasonal precipitation. Thus, these species appear to use different nutrient storage strategies in response to the variation in abiotic and trophic conditions across their range. When reared under the same feeding regime and thermal conditions, site-level differences in nitrogen storage between a northern and a southern ant population were retained over time and across years, suggesting that adaptive divergence in elemental composition is at least partially responsible for clinal patterns in the field. To connect latitudinal patterns to temporal changes projected under climate change, I evaluated how increases in temperature impact ant stoichiometry and associated functional traits at the individual and colony level using an experimental field mesocosm experiment at two sites, Harvard Forest (HF) and Duke Forest (DF). I examined how experimental increases in temperature impacted ant body size, colony demography, and nutritional status of two Aphaenogaster ant species. I found that Aphaenogaster ants at the northern site, HF, responded positively to direct increases in temperature, with increases in colony biomass, colony size, total reproductive output, and shifts toward increased nitrogen content with increases in temperature. In contrast, Aphaenogaster ants at the southern site, DF, were generally unaffected by temperature except for a decrease in maximum colony size with increases in temperature. Together, my findings provide evidence that both climate variables and evolutionary history impacts ant stoichiometry, which in turn, may impact ant colony fitness. Examination of the biochemical basis of stoichiometric trait variation is needed to ascertain the role stoichiometry may play in how ant species adapt to changing environmental conditions.