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  • 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.
321

Sistemas agroflorestais como alternativa para recomposição e uso sustentável das reservas legais / Agroforestry as an alternative to restoration and sustainable use of legal reserves

Martins, Tatiana Parreiras 30 August 2013 (has links)
As reservas legais (RL) são uma categoria de área protegida brasileira que visa o uso econômico sustentável concomitante à proteção ambiental da biodiversidade e dos processos ecológicos. Entre as alternativas para concretização dessas funções, seja na restauração e/ou uso desses espaços, estão os sistemas agroflorestais (SAF). Tais sistemas são frequentemente apontados como sustentáveis, por proporcionarem simultaneamente benefícios biológicos e socioeconômicos. Este trabalho tem como objetivo abordar, nos aspectos teórico e prático, a possibilidade de uso de SAF para recomposição e uso sustentável das RL. Os dois primeiros capítulos, baseados em revisão bibliográfica, discutem: a adequação, os potenciais, as limitações e as características de SAF para cumprimento de objetivos de conservação e para constituição das RL (capítulo 1); a viabilidade, os meios e as metas para conciliação da proteção ambiental ao desenvolvimento socioeconômico preconizado para as RL (capítulo 2). O capítulo 3 estabelece um conjunto de indicadores para avaliar e monitorar a sustentabilidade, na dimensão ecológica/ambiental, de SAF no contexto da restauração e uso das RL, em áreas de fisionomia florestal tropical. A metodologia adotada para o capítulo consistiu em pesquisas bibliográficas e consultas a especialistas. Do capítulo 1, destacam-se as seguintes conclusões: SAF podem constituir ótimas opções para reorientar os sistemas produtivos humanos, mas seu emprego em áreas protegidas é questionável e deve ser criterioso; os SAF complexos são a opção mais próxima de cumprir com objetivos de conservação e princípios da sustentabilidade; SAF são pobres substitutos para ecossistemas naturais, portanto, não devem ser promovidos em detrimento da vegetação natural remanescente, mas como ferramenta complementar aos esforços de conservação, restaurando ecossistemas e compondo uma matriz de melhor qualidade fora das áreas protegidas. Do capítulo 2, as principais conclusões são: a conciliação da proteção ambiental ao desenvolvimento socioeconômico permanece um desafio; a busca e aprimoramento de práticas sustentáveis de uso direto dos recursos naturais deveriam ocorrer predominantemente fora das áreas protegidas, que devem priorizar a proteção da biodiversidade; a legislação, que propõe diversas funções para as RL, não orienta como concretizá-las; é necessário definir critérios e metas para restauração e uso sustentável das RL, nas distintas dimensões da sustentabilidade, mantendo a flexibilidade para adequação aos distintos contextos. O capítulo 3 evidenciou a diversidade, e divergência, de visões e posicionamentos dos profissionais que trabalham com SAF e propôs o seguinte conjunto de indicadores, subdivididos em três categorias: (a) estrutura estrato (avaliação atemporal), distribuição em classes diamétricas, densidade e exposição do solo; (b) composição riqueza, abundância, ciclos de vida, função das exóticas; (c) função regenerantes e mudas, horizonte orgânico (serrapilheira ou turfa). São recomendadas adaptações em função do contexto de restauração ou uso sustentável e do diagnóstico da área. No caso da restauração sugere-se a adicional observação do nível de complexificação do ambiente demandado pelas espécies a serem implantadas. São também apresentadas considerações e sugestões acerca dos parâmetros para avaliação realizada por meio dos indicadores propostos. Espera-se que este trabalho contribua para futuras discussões em âmbito acadêmico e para aplicação prática subsidiando as ações do Estado na orientação da implantação e manejo, na fiscalização e monitoramento dos SAF que comporão as RL. / Legal Reserve (RL) is a Brazilian category of protected area that aims to provide sustainable economic uses in agreement to environmental protection of biodiversity and ecological processes. Among the alternatives to achieve these functions, either in the restoration or use of these areas, there are the agroforestry systems (SAF). These systems are considered sustainable by offering biological and socioeconomic benefits. This research addresses the theoretical and practical aspects of the possibility of using SAF for restoration and sustainable use of RL. The first two chapters, based on literature review, discuss: the suitability, the potential, the limitations and the characteristics of SAF for achieving conservation objectives and for constitution of RL (chapter 1); the viability, means and targets to conciliate environmental protection to the socioeconomic development advocated for RL (chapter 2). Chapter 3 provides a set of indicators to assess and monitor the ecological/environmental sustainability of SAF in the context of restoration and use of RL in tropical forest areas. The chapter was constructed based on literature review and consultations to specialists. From chapter 1, some important conclusions are: SAF can be a great option to refocusing the human productive systems, but its use in protected areas is questionable and must be careful; complex SAF are the best option to meet conservation objectives and principles of sustainability; SAF are poor substitutes for natural ecosystems, therefore, they should not be promoted at the expense of the remaining natural vegetation, but as a complementary tool to conservation efforts by restoring ecosystems and composing a best quality matrix outside protected areas. From chapter 2, the main conclusions are: reconciling environmental protection to socioeconomic development remains as a challenge; the research and improvement of sustainable development practices should occur outside protected areas, which should primarily be dedicated to the protection of biodiversity; the legislation proposes various functions to the RL but does not guide how to achieve them, it is necessary to define clear criteria and goals for restoration and sustainable use of the RL in the different sustainability dimensions, while maintaining the flexibility of adapting them to the different contexts. Chapter 3 highlighted the diverse and divergent viewpoints and attitudes of SAF professionals workers and proposed the following set of indicators, divided into three categories: (a) structure vertical structure (timeless evaluation), diameter classes distribution, density and soil exposure, (b) composition species richness and relative abundance, life cycles, exotic species function (c) function natural regeneration, organic horizon (litter or peat). Adaptations are recommended regarding the context of restoration and sustainable use, and the diagnosis of the area. For the restoration context, the environmental complexity level demanded by the species to be implanted should be observed. Suggestions about the parameters for evaluation carried out by the proposed indicators are presented. It is hoped that this study contribute to future scientific discussions and to support the government in guiding the implementation and management, supervision and monitoring of the SAF that will compose RL.
322

Did quantitative easing impact wealth inequality?

Georget, Marie-Jacques January 2019 (has links)
On November 25, 2008, the Federal Reserve initiated what came to be the largest Asset Purchase Program in history1, the Large-Scale Asset Purchase Program, widely known a quantitative easing (QE). When the Federal Reserve in October 29, 2014, announced the end of the program, they held $4.5 trillion worth of assets. This rather unconventional monetary policy came in the aftermath of the 2008 financial crisis and since its implementation, critics have argued that the policy increases inequality in terms of income and wealth. Studies on the impact of QE on income inequality lead to divergent conclusions, but the close link between QE and the stock markets, as explained by the Portfolio Rebalancing Effect, suggests that QE should increase wealth inequality. This hypothesis however, relies on a crucial assumption, namely that richer households hold a larger portion of their wealth in stocks. As other assets of a household, such as the primary residence, are likely to increase less than proportionally with wealth, I find it plausible that the portion allocated to direct or indirect stock holdings increases with wealth, resulting in a higher exposure to stocks for the very rich. Statistics from the Survey of Consumer Finances, presented in this paper, confirm that richer households indeed have the higher exposure to stocks. I use a difference-in-difference model to estimate the causal impact of QE on wealth inequality in the United States and my results suggests that wealth inequality attributable to QE) increased with at least 25 percent, measured as a change in the wealth-ratio between the 9th decile of households and the artificial middle-income household constructed in accordance with the Synthetic Control Method.
323

Bornhuetterova-Fergusonova metoda, odhadování parametrů a chyba predikce / The Bornhuetter-Ferguson method, parameter estimation and prediction error

Santnerová, Petra January 2012 (has links)
This diploma thesis describes the Bornhuetter-Ferguson method, which is used to calculate the IBNR reserve. It is divided into deterministic and stochastic parts. The deterministic part deals with the derivation of development pattern and ultimate loss amount, which are needed to calculate the reserve. The stochastic part deals with reserve estimation error and prediction error. The calculation results of the reserve estimate and its error are compared with the results of the chain ladder method. The last chapter deals with the problematic areas of the described method.
324

Kredibilitní přístupy k výpočtu rezerv na pojistná plnění / Credibility approach to claims reserves calculation

Dzugas, Erik January 2012 (has links)
In this work we summarize the various techniques of claims reserves evaluating which consist in estimate of the future uncertain and hardly antici- pated loss development. It appears that the methods which are based on some credibility formula bring in the mean squared error sense the most accurate results. We consider this in the text derived conclusion very relevant and con- tributing, therefore we illustrate and present it on the numerical example. The calculations are introduced in the attached charts that build the important sup- plement of the text. The topic of this work follows up the content of Nonlife Insurance and Risk Theory lectures, therefore this text can be useful also for the students of the Faculty of Mathematics and Physics to extend their knowledge. 1
325

Biogeografia da conservação de morcegos no cerrado brasileiro / Conservation biogeography of bats in the brazilian cerrado

Barreto, Bruno de Souza 06 June 2008 (has links)
Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-25T18:57:04Z No. of bitstreams: 2 Bruno de Souza Barreto - 2008 - Dissertação.pdf: 2633509 bytes, checksum: 9a1040f27931399225f28b393e640b6e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2014-09-26T11:43:42Z (GMT) No. of bitstreams: 2 Bruno de Souza Barreto - 2008 - Dissertação.pdf: 2633509 bytes, checksum: 9a1040f27931399225f28b393e640b6e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-26T11:43:42Z (GMT). No. of bitstreams: 2 Bruno de Souza Barreto - 2008 - Dissertação.pdf: 2633509 bytes, checksum: 9a1040f27931399225f28b393e640b6e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2008-06-06 / Fundação de Apoio à Pesquisa - FUNAPE / The units of conservation are main strategy adopted by the rulers to guarantee that the negative effects of the socioeconomic development reach less the biodiversity. recent researches have been trying to outline the problem through reserve selection that seek larger representativeness of the goals of conservation (in general some estimador of the biodiversity as the species) in terms of a smaller number of areas as possible. in the last 50 years the cerrado is going by transformations in their natural landscapes due to the progress of the modern agriculture and of the livestock. due to that, the objective of that work was to define priority areas network for conservation of bats in terms of five conservation sceneries differents. the generated nets were restricted by socioeconomic cost, presence of cave and a cost that considers the previous two cost. the results revealed main features of analyses of complementarity: multiple solutions, flexibility of the nets, and influence of the rarity of the species for the definition of groups starting from the pattern of rarity. the costs were important for definition of nets that avoided as much conflicts of conservation as prioritized the species in areas of cave. / As unidades de conservação são principal estratégia adotada pelos governantes para garantir que os efeitos negativos do desenvolvimento socioeconômico atinjam menos a biodiversidade. recentes pesquisas têm tentado contornar o problema através de seleção de reservas que visam maior representatividade das metas de conservação (em geral algum estimador da biodiversidade como as espécies) em termos de um menor número de áreas quanto possível. nos últimos 50 anos o cerrado vem passando por transformações em suas paisagens naturais em decorrência do avanço da agricultura moderna e da pecuária. os morcegos são também ameaçados e em decorrência disso, o objetivo desse trabalho foi definir redes de reservas regionais prioritárias para conservação de morcegos em termos de cinco cenários de conservação diferentes. as redes geradas foram restringidas por custo socioeconomico, custo presença de caverna e custo que podera os dois anteriores. os resultados reelaram as principais caracteísticas de análises de complementaridade: multiplas soluçoes, flexibilidade das redes, influência da raridade das espécies pela definição de grupos a partir do padrão de raridade. os custos foram importantes para definição de redes que evitaram tanto conflitos de conservação quanto priorizaram as espécies em regioes de caverna.
326

Automação como recurso de planejamento de redes de distribuição de energia elétrica. / Automation as resource for distribution systems planning.

Daniel Perez Duarte 16 May 2008 (has links)
Como produto de engenharia, os componentes das redes de distribuição de energia elétrica são, pela sua própria natureza, susceptíveis a falhas de funcionamento ou a ações de manutenção que impedem a operação de alguma instalação. No sentido de manter o desempenho adequado, nessas condições, são adotados critérios de planejamento e projeto que prevêem redundâncias de instalações, de forma que haja a continuidade de fornecimento de energia mesmo com componentes fora de operação. Com alguma freqüência os sistemas de potência, principalmente em seus segmentos de transmissão e de distribuição de energia, adotam critérios de planejamento de suas instalações que consideram reserva de capacidade local (\"N-1\"local) para garantir a continuidade do serviço quando um de seus componentes está fora de operação. Esse critério se reveste de um conceito qualitativo na medida que, em geral, não quantifica o prejuízo e o transtorno que uma falha pode provocar, nem os recursos operativos que podem permitir ao sistema suportar ações de manutenção programada, sendo dessa forma, insuficiente para a perfeita avaliação de alternativas de expansão da rede de distribuição. Por outro lado, cálculo da Energia Não Distribuída - END - de forma probabilística para as falhas e de forma sistemática para eventuais interrupções durante as ações de manutenção preventiva é um recurso mais elaborado, de caráter quantitativo, para o dimensionamento da reserva de capacidade dos sistemas elétricos e portanto, de alternativas de expansão. Com a introdução de dispositivos automáticos e meios de comunicação na rede de distribuição é possível a realização de manobras e transferências de carga de maneira a garantir a continuidade do fornecimento em níveis aceitáveis, substituindo, muitas vezes a instalação de novas estruturas como alimentadores ou mesmo subestações. Disto resulta uma redução de custo proporcionada pela otimização da capacidade instalada, necessária para reserva de contingência, sem prejuízo do desempenho e da qualidade de serviço. O escopo deste trabalho é propor uma metodologia de planejamento fundamentada no custo da interrupção como uma alternativa ao critério N-1, de forma a permitir a avaliação tanto da aplicação de recursos de automação como também dos recursos convencionais de expansão da rede. A validação da metodologia proposta está ilustrada numa aplicação apresentada neste texto. / Concerning the components of an electrical distribution network and their susceptibility to functional failures or need for maintenance actions, planning and project criteria should be adopted to assure continuity of energy supply even though some components may be out of work. Traditionally the power systems, especially in power transmission and distribution, adopt the N-1 criterion in the planning of its installations to keep the service continuity when one of the components is out of work. This criterion is based on a qualitative concept, in general, it does not quantify the loss and the inconvenience that a failure can cause, neither the operative resources that can allow the system to support programmed maintenance actions, thus being, insufficient for the perfect evaluation of expansion alternatives of the distribution network. Whereas, the Non Distributed Energy calculus - NDE - a probabilistic approach for failures and a systematic approach for interruptions during the preventive maintenance actions is a more elaborated resource, based on a quantitative concept, for the dimensioning of capacity reserve of the electric systems and therefore, the expansion alternatives. The introduction of the automatic devices and communication technologies in the distribution network make it possible to do maneuvers and load transfers in order to keep the supply continuity on acceptable levels, substituting, many times, the installation of new structures as feeders or even substations. The result is being cost reduction provided by the optimization from installed capacity, necessary to contingency reserve, without affecting the performance and service quality. The scope of this work is to propose a planning methodology based on the cost of the NDE, which enables the evaluation of both the automation resources and conventional resources as well. In this work you shall find an application of the methodology in a case study.
327

Leis ambientais e pequenos proprietários no município de Manfrinópolis - PR: isonomia X (in)sustentabilidade / Enviromental laws and small property owners in the city of Manfrinópolis - PR: isonomy X (in)sustentability

Bello, Ivanilda Bernardon 08 December 2009 (has links)
Made available in DSpace on 2017-07-10T17:30:57Z (GMT). No. of bitstreams: 1 Ivanilda Capa.pdf: 163952 bytes, checksum: 5f34a84026e28612eb6a2cbab47a305f (MD5) Previous issue date: 2009-12-08 / The focus of four work takes us to social and economical problems caused by the environmental policy related to the isonomy of Legal Reserves and to the small landowners in the city of Manfrinópolis PR. We understand that the Brazilian legislation, when it establishes the environmental law of Legal Reserves, only seeks to bound the small property, regionalizing it geographically. To generate the very concept of equality or Isonomy, it should have, at least, conceptualized the small farmer, and not only the small property. We affirm this because the same (small or big) owner can have several small properties. However, the application of laws that regulate environmental resources is still a problematic issue in Brasil. Within this context, the isonomy applied to the same percentage set aside to Legal Reserve, to big and small owner, infringe the social function of property. Unlike the big owner, who has the privilege to plan and direct the course of his areas for the implementation of the law, the small owner, without this option, is obligated to allocate the same percentage inside his small area, reducing more yet his property, act that may compromise his survival. / O enfoque de nosso trabalho nos remete aos problemas socieoconômicos causados pela política ambiental quanto à isonomia das Reservas Legais junto aos pequenos proprietários rurais residentes no município de Manfrinópolis-PR.Entendemos que a legislação brasileira ao elaborar a lei ambiental referente as Reservas Legais, tão somente procurou delimitar a pequena propriedade regionalizando-a geograficamente. Deveria a mesmo, para haver surtido o verdadeiro conceito de igualdade ou Isonomia, conceituar o pequeno produtor rural, e não a pequena propriedade. Afirmamos isso uma vez que um mesmo proprietário (médio ou grande) pode ser possuidor de diversas pequenas propriedades.Todavia, se constata que a aplicação das leis reguladoras dos recursos ambientais ainda é uma questão problemática no país. Dentro desse contexto, a isonomia aplicada ao mesmo percentual reservado de Reserva Legal ao grande proprietário quanto ao pequeno fere a função social da propriedade, pois diferentemente do grande proprietário que possui o privilégio de programar e direcionar o curso de suas áreas para a implantação da lei, o pequeno proprietário sem esta opção é obrigado a destinar o mesmo percentual em sua pequena área reduzindo ainda mais seu imóvel podendo comprometer a sua sobrevivência.
328

Leis ambientais e pequenos proprietários no município de Manfrinópolis - PR: isonomia X (in)sustentabilidade / Enviromental laws and small property owners in the city of Manfrinópolis - PR: isonomy X (in)sustentability

Bello, Ivanilda Bernardon 08 December 2009 (has links)
Made available in DSpace on 2017-05-12T14:42:29Z (GMT). No. of bitstreams: 1 Ivanilda Capa.pdf: 163952 bytes, checksum: 5f34a84026e28612eb6a2cbab47a305f (MD5) Previous issue date: 2009-12-08 / The focus of four work takes us to social and economical problems caused by the environmental policy related to the isonomy of Legal Reserves and to the small landowners in the city of Manfrinópolis PR. We understand that the Brazilian legislation, when it establishes the environmental law of Legal Reserves, only seeks to bound the small property, regionalizing it geographically. To generate the very concept of equality or Isonomy, it should have, at least, conceptualized the small farmer, and not only the small property. We affirm this because the same (small or big) owner can have several small properties. However, the application of laws that regulate environmental resources is still a problematic issue in Brasil. Within this context, the isonomy applied to the same percentage set aside to Legal Reserve, to big and small owner, infringe the social function of property. Unlike the big owner, who has the privilege to plan and direct the course of his areas for the implementation of the law, the small owner, without this option, is obligated to allocate the same percentage inside his small area, reducing more yet his property, act that may compromise his survival. / O enfoque de nosso trabalho nos remete aos problemas socieoconômicos causados pela política ambiental quanto à isonomia das Reservas Legais junto aos pequenos proprietários rurais residentes no município de Manfrinópolis-PR.Entendemos que a legislação brasileira ao elaborar a lei ambiental referente as Reservas Legais, tão somente procurou delimitar a pequena propriedade regionalizando-a geograficamente. Deveria a mesmo, para haver surtido o verdadeiro conceito de igualdade ou Isonomia, conceituar o pequeno produtor rural, e não a pequena propriedade. Afirmamos isso uma vez que um mesmo proprietário (médio ou grande) pode ser possuidor de diversas pequenas propriedades.Todavia, se constata que a aplicação das leis reguladoras dos recursos ambientais ainda é uma questão problemática no país. Dentro desse contexto, a isonomia aplicada ao mesmo percentual reservado de Reserva Legal ao grande proprietário quanto ao pequeno fere a função social da propriedade, pois diferentemente do grande proprietário que possui o privilégio de programar e direcionar o curso de suas áreas para a implantação da lei, o pequeno proprietário sem esta opção é obrigado a destinar o mesmo percentual em sua pequena área reduzindo ainda mais seu imóvel podendo comprometer a sua sobrevivência.
329

L'enrichissement olfactif au cours du vieillissement : implication de la Noradrénaline et modèle de réserve cognitive / Olfactory enrichment during aging : improvement of Noradrenaline and model of cognitive reserve

Terrier, Claire 27 November 2018 (has links)
Le vieillissement est un phénomène biologique complexe et inévitable associé à un déclin progressif des fonctions cognitives, sensorielles et motrices qui affecte la qualité de vie et la santé des sujets âgés. Le vieillissement normal s'accompagne de changements structuraux et fonctionnels, conduisant au déclin cognitif. Parmi ces changements, les altérations du système noradrénergique semblent contribuer de façon significative aux déficits cognitifs. Inversement, le maintien de l'intégrité du Locus Coeruleus semble participer à la préservation des performances. Par ailleurs, une stratégie pour promouvoir le bien vieillir propose de booster la réserve cognitive associée à un haut niveau de stimulation cérébrale et à des modulations de l'activation et de la connectivité cérébrales chez l'humain. Chez les rongeurs, l'enrichissement environnemental promouvant les stimulations sensorielles, l'activité motrice et les interactions sociales, mime les conditions de mise en place de la réserve cognitive chez l'homme et a largement montré ses effets bénéfiques sur la cognition. Les objectifs de cette thèse sont premièrement, d'étudier le rôle de la NA dans le maintien de la plasticité structurale et des capacités de discrimination olfactive chez la souris âgée, puis dans un second temps de tester l'enrichissement olfactif comme modèle de construction de la réserve cognitive. Dans une première étude, nous avons utilisé le modèle d'apprentissage perceptif olfactif pour étudier la contribution de la Noradrénaline au maintien de la plasticité structurale et des performances cognitives au cours du vieillissement chez la souris. Cet apprentissage consiste en une amélioration de la discrimination entre deux odorants proches sur le plan perceptif après une exposition répétée à ces odorants. Nos résultats suggèrent que la libération de Noradrénaline dans le bulbe olfactif via une stimulation optogénétique des fibres issues du Locus Coeruleus maintient les capacités de discrimination au cours du vieillissement. Nos données révèlent aussi une forme de plasticité du réseau noradrénergique dans le bulbe olfactif âgé. Ces résultats soutiennent l'hypothèse d'une contribution importante de la Noradrénaline au bien vieillir cérébral. Dans une deuxième étude, nous avons utilisé une stratégie basée sur un enrichissement olfactif, manipulation capable de mobiliser la Noradrénaline, proposé tout au long de la vie de l'animal, dans le but de permettre le développement d'une réserve cognitive. Nos résultats montrent qu'un tel enrichissement améliore les capacités de discrimination olfactive même à un âge avancé. De façon intéressante, les performances non olfactives de mémoire spatiale et de flexibilité sont aussi améliorées. Ces résultats indiquent que les effets bénéfiques de l'enrichissement s'étendent au-delà de la sphère olfactive et incluent des bénéfices sur différentes performances cognitives sensibles à l'âge. Nous proposons donc l'enrichissement olfactif comme un modèle de la construction d'une réserve cognitive qui nous permettra par la suite d'identifier les bases cellulaires du bien vieillir et de tester la contribution de la Noradrénaline dans la construction de la réserve cognitive / Aging is an inevitable and complex biological phenomenon associated with a progressive decline of sensory, motor and cognitive functions with time, affecting life quality and health. Normal brain aging is accompanied by functional and structural changes, leading to cognitive decline. Among these changes, age-related alterations of the noradrenergic system seem to contribute significantly to cognitive deficits. Conversely, the integrity of the Locus Coeruleus seems to allow healthy cognitive aging. A potentially powerful tool to achieve successful brain aging is to boost the cognitive reserve, associated with higher level of brain stimulation and modulations in brain activation and connectivity in humans. In rodents, environmental enrichment, increasing sensory stimulations, motor activity and social interactions, mimics the conditions leading to constitution of the cognitive reserve in humans and has largely proven cognitive benefits.The goals of this thesis are, in the first place, to study the role of Noradrenaline in the maintenance of structural plasticity and olfactory discrimination abilities in aged mice, then secondly, to test the olfactory enrichment as a model of the cognitive reserve build-up.In the first study, we used the olfactory perceptual learning paradigm to investigate the contribution of Noradrenaline to the maintenance of structural plasticity and cognitive abilities during aging in mice. This learning consists in an improvement of the discrimination between perceptually close odorants after repeated exposure to these odorants. Our results suggest that the local release of Noradrenaline in the olfactory bulb, by optogenetic stimulation of Locus Coeruleus fibers allows the maintenance of discrimination abilities during aging. Our data also reveal a form of structural plasticity of the noradrenergic innervation in the aged olfactory bulb. The overall work supports a contribution of Noradrenaline to healthy brain aging.In a second study, we used a strategy based on repeated olfactory enrichment during the whole life of the animal in order to enable the cognitive reserve buildup. Such enrichment maintained olfactory discrimination performances at late ages. Interestingly, mice’s performances in spatial memory and cognitive flexibility improved too. This result indicates that the benefits of an odor-based enrichment extend beyond the olfactory sphere and include broader cognitive benefits on age-sensitive functions. We thus propose lifelong olfactory enrichment as model of the cognitive reserve build-up to further identify its cellular basis and test the contribution of Noradrenaline to cognitive reserve build-up and healthy brain aging
330

Exploring the Resting State Neural Activity of Monolinguals and Late and Early Bilinguals

Gold, Carrie Elizabeth 01 January 2018 (has links)
Individuals who speak more than one language have been found to enjoy a number of benefits not directly associated with the use of the languages themselves. One of these benefits is that bilingual individuals appear to develop symptoms of dementia 4-5 years later than comparable individuals who speak just one language. Studies on this topic, however, do not consistently account for factors including if the individual learned their second language as a child or later in life, or their language proficiency. In an attempt to more carefully examine these variables, this study looks at structural and resting-state functional MRI scans of the default mode network, English and Spanish (where applicable) proficiency, language background, and demographics of young healthy adults who fall into one of three groups: early bilinguals, late bilinguals, and monolinguals. Of the three groups, late bilinguals were found to have a small but statistically significantly higher level of connectivity compared with early bilinguals in the region of the medial prefrontal cortex; patterns found examining number of languages and language proficiency in relation to functional connectivity and research group also supported this finding. These results indicate studying a language after adolescence could provide neuroprotective benefits of a nature that could potentially help delay symptoms of dementia. Age, gender, ethnicity, level of education, English language proficiency, and Spanish language use did not result in statistically significant findings, the latter of which challenges using frequency of language use to define bilingualism.

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