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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.
161

Sledování exprese proteinů v savčích buňkách infikovaných virem klíšťové encefalitidy

KOČOVÁ, Pavlína January 2017 (has links)
This study is focused on changes in protein expression in a glioblastoma cell line during infection with tick-borne encephalitis virus. Newly synthesized proteins were distinguished from previously synthesized proteins using bioorthogonal chemistry (BONCAT method) to observe changes in protein synthesis. Labelled proteins were visualized using two-dimensional PAGE and western blotting followed by Click reaction on membrane. Differences in protein pattern between control and infected cells were observed.
162

Dinâmica do fósforo na interface água-sedimento em reservatórios

Franzen, Melissa January 2009 (has links)
Os sedimentos aquáticos podem fornecer importantes subsídios na avaliação dos ecossistemas aquáticos lênticos, uma vez que grande parte dos nutrientes se encontra no estado sólido. A ocorrência de uma floração de cianobactérias tóxicas originada no Blang, segundo de três reservatórios em cascata do Sistema Salto de Hidrelétricas, localizado no município de São Francisco de Paula (RS), motivou a investigação das possíveis fontes de nutrientes, especialmente de fósforo (P) que foi identificado como limitante para a eutrofização. Foram investigadas fontes de origens difusas (solos, águas e sedimentos dos tributários) e pontuais (uso urbano e a carga interna representada pelo sedimento do leito dos reservatórios). Os resultados mostraram características oligotróficas nas fontes externas e a presença de P disponível em excesso no sedimento do leito, indicando que a carga interna poderia ser uma fonte significativa de nutrientes. A possibilidade de circulação da água hipolimnética foi investigada através de números adimensionais e características físicas do corpo de água, demonstrando que dificilmente ocorreria, uma vez que somente eventos climáticos extremos poderiam provocar a inversão da massa líquida. Excluídas as fontes externas, os resultados sugerem que a fertilização do reservatório Blang tenha sido causada pela abertura da comporta de fundo do reservatório Divisa, localizado imediatamente à montante, durante uma estiagem. O segundo objetivo desta pesquisa foi avaliar a importância dos agregados de partículas e da seleção granulométrica para a análise química de nutrientes em sedimentos aquáticos. Resultados obtidos em sedimentos de ambientes lóticos e lênticos (Sistema Salto, RS), demonstraram que os agregados maiores (465 - 63 μm) concentram nitrogênio nos ambientes lênticos, por isso a análise deve ser realizada, preferencialmente, na fração ≤ 465 μm em sedimentos de ambientes lênticos e na fração ≤ 63 μm dos ambientes lóticos. O último objetivo deste estudo foi testar os efeitos da oxidação sobre a capacidade e a velocidade da sorção de fosfato em sedimentos aquáticos orgânicos, identificando as melhores condições para retenção. Foram utilizados sedimentos aquáticos siliciclásticos de origens distintas, principalmente no que se refere ao clima e à origem do conteúdo orgânico, alóctone e autóctone, representados pelos tipos Dy (Reservatório Divisa, RS) e Sapropel (Reservatório de Tapacurá, São Lourenço da Mata, PE) respectivamente. O experimento foi realizado em suspensões de sedimentos mantidos sob níveis de potencial redox compreendidos entre - 200 mV e + 400 mV. Resultados demonstram que a sorção de fosfato é maior no sedimento tipo Dy em condições reduzidas e no Sapropel em condições oxidadas. / Water-borne sediments can provide important information for evaluating lentic aquatic ecosystems because a large proportion of their nutrients are found in the solid phase. A toxic algal bloom in the Blang Reservoir, the second of three in the Salto System chain of hydroelectric dams located in Sao Francisco de Paula in Rio Grande do Sul, Brazil, motivated the investigation of possible nutrient sources, especially phosphorus, which was identified as the limiting nutrient for eutrophization. Non-point sources, including soil, water and sediment carried by tributaries, and point sources, including urban areas and the internal load from the reservoir bottom, were examined. Results showed oligotrophic characteristics in the external sources and excess P availability in bottom sediments, indicating that the internal load may be a significant source of nutrients. The possible circulation of hypolimnic water was investigated using adimensional numbers and physical characteristics of the body of water, demonstrating that this is unlikely to occur, since only extreme climatic events could cause inversion of the liquid mass. By excluding external sources, results suggest that the fertilization of the Blang Reservoir was most likely caused by the opening of the floodgates from the Divisa Reservoir immediately upstream during a drought period. The second goal of this study was to evaluate the importance of particle aggregates and particle size selection for chemical analyses of nutrients and water-borne sediments. Results from sediments in lentic and lotic environments from the Salto System show that the larger aggregates (465 - 63 μm) concentrate nitrogen under lentic conditions and that, therefore, analyses should be performed on the fraction smaller than 465 μm in lentic environments and in the fraction ≤ 63 μm in lotic environments. The final objective of this study was to test the effects of oxidation on the phosphate sorption capacity and rate in organic aquatic sediments, identifying the best conditions for retention. Silicate aquatic sediments from different origins in terms of climate and source of organic content (allochtonous or autochtonous) were used, and were represented by the types Dy (Divisa Reservoir, RS) and Sapropel (Tapacurá Reservoir, São Lourenço da Mata, PE), respectively. The experiment was carried out in suspended sediment maintained under levels of redox potential between –200mV and +400mV. Results demonstrated that phosphate sorption is greatest in sediment type Dy under reduced conditions and in Sapropel under oxidized conditions.
163

Diagnóstico e avaliação do saneamento básico da zona leste da cidade de Teresina - PI

Arcoverde Filho, Dirceu Mendes [UNESP] 10 May 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:27:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-05-10Bitstream added on 2014-06-13T19:36:07Z : No. of bitstreams: 1 arcoverdefilho_dm_me_rcla.pdf: 6204134 bytes, checksum: 02ac879ad43e1d76e4f0e87c4a264bd8 (MD5) / A forma pela qual os recursos hídricos são utilizados vem degradando os mananciais a um nível tal que se compromete a qualidade de vida das populações. Exauridos pela atividade antrópica, esse fato pode se tornar, no futuro, causador de conflitos. O setor de saneamento básico, sendo um dos que mais se utilizam dos recursos hídricos, é parte de fundamental importância no sentido de promover a melhoria da qualidade de vida da população, utilizando os recursos hídricos de maneira ambientalmente sustentável e garantindo os serviços de abastecimento de água e esgotamento sanitário, mesmo no cenário atual de crescente urbanização, quando se enfrenta a falta de recursos suficientes para expansão dos serviços e a ineficiência no uso dos recursos arrecadados no setor. No quadro dessa problemática, este estudo analisa o espaço urbano da zona leste de Teresina, focalizando o saneamento básico em seus bairros no que diz respeito à problemática dos serviços de abastecimento de água, esgoto sanitário e coleta de lixo. Verifica-se que as camadas mais pobres da população são as que mais sofrem as conseqüências da falta de infraestrutura desses serviços, com a ocorrência de doenças como hepatite e enteroinfecções, contribuindo para a redução da qualidade de vida da população e evidenciando ainda a segregação social existente entre os bairros de uma mesma região da cidade / The way in which water resources are used is degrading the water sources at a level that compromises the quality of life of populations. Depleted by human activity, this may become in the future, causing conflicts. The basic sanitation sector, being one of the most use of water resources, is part of fundamental importance to improving the quality of life of the population using water resources in an environmentally sustainable manner and ensuring the supply services water and sanitation, even in the current scenario of increasing urbanization, when faced with the lack of sufficient resources for expansion of services and inefficiency in the use of funds raised in the industry. As part of this problem, this study examines the urban spaces of the east side of Teresina, focusing on sanitation in their neighborhoods with respect to the issue of services of water supply, sewage and garbage collection. It appears that the poorest of the population are the ones that suffer the consequences of lack of infrastructure such services, with the occurrence of diseases like hepatitis and enteroinfecções, contributing to reduced quality of life of people and showing also the social segregation between the neighborhoods of the same region of the city
164

Možnost ovlivnění zájmu o očkování proti klíšťové encefalitidě v ohnisku nákazy / Possibility interference interest in vaccination against curse encephalitic in focus infection

VOBORSKÁ, Eliška January 2010 (has links)
This diploma thesis addresses the topic of informing people of tick-borne encephalitis and vaccination against this disease. Our diploma thesis has four objectives in total. The first objective was to ascertain how many of the respondents were vaccinated against tick-borne encephalitis. The second and the third objectives were to demonstrate the reasons of vaccinated and unvaccinated respondents. The fourth objective was to analyze the attitudes of the respondents to publicization of the tick-borne encephalitis issue. As an infection with the natural focus, the disease is caused by a tick-borne encephalitis virus belonging among flaviviruses. The carrier is a sheep tick (Ixodes ricinus). Ticks live as parasites on reservoir animals, such as small rodents, ungulates and domestic animals. The clinical picture of the disease has mostly two stages and the symptomatologic form affects in particular adults and seniors. South Bohemia is a significant focus of tick-borne encephalitis with the sickness rate considerably exceeding the average of the Czech Republic. The most efficient prevention of the disease is vaccination. Two vaccines have been registered in the Czech Republic at present, namely FSME-Immun of Baxter and Encepur of Novartis. Both the vaccines are intended for children from 1 year of age. The basic vaccination scheme consists of 3 doses and the vaccinated person needs to be revaccinated every 3-5 years. It follows from the questionnaire research that 49 % of the total number of 136 respondents are vaccinated. As expected, the most frequent reason for vaccination (65 %) is the fear of becoming infected with tick-borne encephalitis. Other reasons are the interventions of the surrounding persons persuading the person to become vaccinated (19 %) and the financial contribution of the health insurance company or the employer (16 %). 35 % of the unvaccinated respondents do not plan to become vaccinated in the future. Approximately 40 % of the unvaccinated respondents feel that they do not need the vaccination or do not trust vaccination as such. 42 % of the unvaccinated persons would agree to vaccination if they received a financial contribution of the health insurance company or the employer, but nothing at all would convince 35 % of the unvaccinated respondents. It follows from the research that most respondents are satisfied with the quantity and the content of the information about tick-borne encephalitis. They do not think that anything should be changed in the system of informing of the disease. This thesis contributes to monitoring the trends in thinking of the public, and will eventuate in the finding which way the education of people about tick-borne encephalitis should be directed.
165

Změny v genomu viru klíšťové encefalitidy u variant s různou historií pasáží a odlišnými biologickými vlastnostmi / Genome changes of tick-borne encephalitis virus in variants with different passage history and biological properties

STROUHALOVÁ, Renata January 2011 (has links)
Tick-borne encephalitis virus (strain Hypr) was serially subcultured in PS cells and tick cell line IRE/CTVM19, producing four different viral variants. Biological properties of these new variants were investigated in mouse model. Possible determinants of virulence were found by full-genome sequencing. The role of glycosylation for tick-borne encephalitis virus was evaluated.
166

Multi-Hazard Damage Mitigation for Low-Rise Wood-Framed Structures using a CarbonFlex Composite

January 2013 (has links)
abstract: This study focused on investigating the ability of a polymeric-enhanced high-tenacity fabric composite called CarbonFlex to mitigate damages from multi-natural hazards, which are earthquakes and tornadoes, in wood-framed structures. Typically, wood-framed shear wall is a seismic protection system used in low-rise wood structures. It is well-known that the main energy dissipation of the system is its fasteners (nails) which are not enough to dissipate energy leading to decreasing of structure's integrity. Moreover, wood shear walls could not sustain their stiffness after experiencing moderate wall drift which made them susceptible to strong aftershocks. Therefore, CarbonFlex shear wall system was proposed to be used in the wood-framed structures. Seven full-size CarbonFlex shear walls and a CarbonFlex wrapped structures were tested. The results were compared to those of conventional wood-framed shear walls and a wood structure. The comparisons indicated that CarbonFlex specimens could sustain their strength and fully recover their initial stiffness although they experienced four percent story drift while the stiffness of the conventional structure dramatically degraded. This indicated that CarbonFlex shear wall systems provided a better seismic protection to wood-framed structures. To evaluate capability of CarbonFlex to resist impact damages from wind-borne debris in tornadoes, several debris impact tests of CarbonFlex and a carbon fiber reinforced storm shelter's wall panels were conducted. The results showed that three CarbonFlex wall panels passed the test at the highest debris impact speed and the other two passed the test at the second highest speed while the carbon fiber panel failed both impact speeds. / Dissertation/Thesis / Ph.D. Civil and Environmental Engineering 2013
167

Construção e validação de critérios quantitativos na definição do risco sanitário em cardápios de restaurantes de hotéis / Development and validation of quantitative index for sanitary risk of offered dishes in restaurants of hotels and resorts

Carlos Sabato Dell Aglio 26 February 2018 (has links)
Houve um crescimento no consumo de alimentos fora do domicílio nas últimas décadas, impulsionado pela urbanização, economia, fatores demográficos e participação das mulheres no mercado de trabalho. O consumo em restaurantes de hotéis passou de 1,4 kg para 7,2 kg per capita entre 2005 e 2014 e apesar de seguir as orientações sanitárias, pode ser risco à saúde humana, devido ao tipo de prato, matéria prima ou cozimento. Assim, foram avaliados os cardápios de hotéis através de um índice de risco sanitário para os usuários, e comparou-se este índice médio do cardápio com características organizacionais e demográficas dos hotéis, seu sucesso midiático e a percepção do pessoal de problemas sanitários. Foi possível mostrar que há um conhecimento de risco pelo maior preço de pratos com risco mais alto. Os hotéis com mais risco têm cardápios mais variados e taxa de ocupação mais alta, sem diferença nos demais critérios demográficos. O pessoal de atendimento tem mais consciência de riscos que a gerência e avaliações midiáticas são menores nos hotéis de maior risco. Quanto à gestão do restaurante pelo hotel, este se mostrou mais segura para os hóspedes na gestão, sendo os restaurantes independentes mais ativos em número de pratos e turismo gastronômico, o que leva a uma melhor avaliação midiática, independente do maior risco. A avaliação do risco médio do cardápio pode levar uma melhor segurança sanitária do hóspede, mas existem outros fatores mercadológicos que podem interferir no cardápio do restaurante. Este conhecimento de risco sanitário pode orientar a escolha mercadológica do restaurante do hotel, provendo um elemento de julgamento da oferta de alimentos que podendo aumentar a fidelização e a segurança sanitária dos hóspedes. A alimentação segura de hóspedes é um processo extremamente importante para o sucesso da hotelaria, já que estes são associados a problemas pelos clientes, o que implica em maior cuidado sanitário na atual expansão do turismo de negócio e lazer no Brasil. / There has been an increase in consumption of food outside the home in the last decades, driven by urbanization, economy, demographic factors and women\'s participation in the labor market. The consumption in hotel restaurants went from 1.4 kg to 7.2 kg per capita between 2005 and 2014 and despite following the sanitary guidelines, can be risk to human health, by type of dish, raw food or cooking. Thus, we evaluated the hotel menus through a sanitary risk index for the users, and compared this average menu index with organizational and demographic characteristics of the hotels, their media success and the staff\'s perception of health problems. It was possible to show that there is a knowledge of risk by the higher price of dishes with higher risk. The hotels with more risk have more varied menus and higher occupancy rate, with no difference in the other demographic criteria. Service staff are more aware of risks that management and media reviews are lower in hotels at higher risk. As for the management of the restaurant by the hotel, this is safer for guests in hotel management, with independent restaurants more active in number of dishes and gastronomic tourism, which leads to a better media assessment, regardless of the greater risk. The evaluation of the average risk of the menu may lead to a better sanitary security of the guest, but there are other marketing factors that can interfere with the menu of the restaurant. This knowledge of sanitary risk can guide the market choice of the hotel restaurant, providing an element of judgment of the food supply that can increase the loyalty and sanitary security of the guests. The safe feeding of guests is an extremely important process for the success of the hotel industry, since these are associated with problems by the clients, which implies in greater health care in the current expansion of business and leisure tourism in Brazil.
168

Dinâmica do fósforo na interface água-sedimento em reservatórios

Franzen, Melissa January 2009 (has links)
Os sedimentos aquáticos podem fornecer importantes subsídios na avaliação dos ecossistemas aquáticos lênticos, uma vez que grande parte dos nutrientes se encontra no estado sólido. A ocorrência de uma floração de cianobactérias tóxicas originada no Blang, segundo de três reservatórios em cascata do Sistema Salto de Hidrelétricas, localizado no município de São Francisco de Paula (RS), motivou a investigação das possíveis fontes de nutrientes, especialmente de fósforo (P) que foi identificado como limitante para a eutrofização. Foram investigadas fontes de origens difusas (solos, águas e sedimentos dos tributários) e pontuais (uso urbano e a carga interna representada pelo sedimento do leito dos reservatórios). Os resultados mostraram características oligotróficas nas fontes externas e a presença de P disponível em excesso no sedimento do leito, indicando que a carga interna poderia ser uma fonte significativa de nutrientes. A possibilidade de circulação da água hipolimnética foi investigada através de números adimensionais e características físicas do corpo de água, demonstrando que dificilmente ocorreria, uma vez que somente eventos climáticos extremos poderiam provocar a inversão da massa líquida. Excluídas as fontes externas, os resultados sugerem que a fertilização do reservatório Blang tenha sido causada pela abertura da comporta de fundo do reservatório Divisa, localizado imediatamente à montante, durante uma estiagem. O segundo objetivo desta pesquisa foi avaliar a importância dos agregados de partículas e da seleção granulométrica para a análise química de nutrientes em sedimentos aquáticos. Resultados obtidos em sedimentos de ambientes lóticos e lênticos (Sistema Salto, RS), demonstraram que os agregados maiores (465 - 63 μm) concentram nitrogênio nos ambientes lênticos, por isso a análise deve ser realizada, preferencialmente, na fração ≤ 465 μm em sedimentos de ambientes lênticos e na fração ≤ 63 μm dos ambientes lóticos. O último objetivo deste estudo foi testar os efeitos da oxidação sobre a capacidade e a velocidade da sorção de fosfato em sedimentos aquáticos orgânicos, identificando as melhores condições para retenção. Foram utilizados sedimentos aquáticos siliciclásticos de origens distintas, principalmente no que se refere ao clima e à origem do conteúdo orgânico, alóctone e autóctone, representados pelos tipos Dy (Reservatório Divisa, RS) e Sapropel (Reservatório de Tapacurá, São Lourenço da Mata, PE) respectivamente. O experimento foi realizado em suspensões de sedimentos mantidos sob níveis de potencial redox compreendidos entre - 200 mV e + 400 mV. Resultados demonstram que a sorção de fosfato é maior no sedimento tipo Dy em condições reduzidas e no Sapropel em condições oxidadas. / Water-borne sediments can provide important information for evaluating lentic aquatic ecosystems because a large proportion of their nutrients are found in the solid phase. A toxic algal bloom in the Blang Reservoir, the second of three in the Salto System chain of hydroelectric dams located in Sao Francisco de Paula in Rio Grande do Sul, Brazil, motivated the investigation of possible nutrient sources, especially phosphorus, which was identified as the limiting nutrient for eutrophization. Non-point sources, including soil, water and sediment carried by tributaries, and point sources, including urban areas and the internal load from the reservoir bottom, were examined. Results showed oligotrophic characteristics in the external sources and excess P availability in bottom sediments, indicating that the internal load may be a significant source of nutrients. The possible circulation of hypolimnic water was investigated using adimensional numbers and physical characteristics of the body of water, demonstrating that this is unlikely to occur, since only extreme climatic events could cause inversion of the liquid mass. By excluding external sources, results suggest that the fertilization of the Blang Reservoir was most likely caused by the opening of the floodgates from the Divisa Reservoir immediately upstream during a drought period. The second goal of this study was to evaluate the importance of particle aggregates and particle size selection for chemical analyses of nutrients and water-borne sediments. Results from sediments in lentic and lotic environments from the Salto System show that the larger aggregates (465 - 63 μm) concentrate nitrogen under lentic conditions and that, therefore, analyses should be performed on the fraction smaller than 465 μm in lentic environments and in the fraction ≤ 63 μm in lotic environments. The final objective of this study was to test the effects of oxidation on the phosphate sorption capacity and rate in organic aquatic sediments, identifying the best conditions for retention. Silicate aquatic sediments from different origins in terms of climate and source of organic content (allochtonous or autochtonous) were used, and were represented by the types Dy (Divisa Reservoir, RS) and Sapropel (Tapacurá Reservoir, São Lourenço da Mata, PE), respectively. The experiment was carried out in suspended sediment maintained under levels of redox potential between –200mV and +400mV. Results demonstrated that phosphate sorption is greatest in sediment type Dy under reduced conditions and in Sapropel under oxidized conditions.
169

Investigating the compliance with universal precautions among health care providers in Tikur Anbessa Central Referral Hospital, Addis Ababa, Ethiopia

Gebreselassie, Fasil Taye January 2009 (has links)
Magister Public Health - MPH / This study has reveled the levels of knowledge and compliance towards Universal Precautions and examined the factors that are influential in having a positive and negative effect on their adoption by healthcare practitioners in practice. Despite acceptable knowledge regarding the potential for infection and mechanisms to prevent these infections, this study has found out that health care workers are not as compliant with universal precautions as they need to be. The findings that compliance correlated directly with knowledge, with in-service training and with availability of protective equipment, provide important indications for future interventions. Therefore a regular on job refreshing training program on Universal Precautions, a written guideline and reminder poster on Universal Precautions and personal protective equipment need to be made available for all health care providers in every department of the hospital for better compliance.
170

Étude asymptotique des processus de branchement sur-critiques en environnement aléatoire / Asymptotic study for supercritical branching processes in a random environment

Miqueu, Éric 09 December 2016 (has links)
L’objet de cette thèse concerne l’étude asymptotique des processus de branchement sur-critiques en environnement aléatoire, qui sont une généralisation du processus de Galton-Watson, avec une loi de reproduction choisie aléatoirement et de manière i.i.d. suivant les générations. Dans le cas de non extinction, nous démontrons une succession de résultats asymptotiques plus fins que ceux établis dans des travaux antérieurs. Le chapitre 1 est consacré à l’étude de l’écart relatif entre le processus (Zn) normalisé et la loi normale. Nous établissons une borne de type Berry-Esseen ainsi qu’un développement pour des déviations de type Cramér, généralisant ainsi le théorème central limite et le principe des déviations modérées établis précédemment dans la littérature. Le second chapitre concerne l'asymptotique de la distribution du processus (Zn) ainsi que le moment harmonique critique de la variable limite W de la population normalisée. Nous établissons un équivalent de l'asymptotique de la distribution du processus Zn et donnons une caractérisation des constantes via une équation fonctionnelle similaire au cas du processus de Galton-Watson. Dans le cas des processus de branchement en environnement aléatoire, les résultats améliorent l'équivalent asymptotique de la distribution de Zn établi dans des travaux antérieurs sous normalisation logarithmique, sous la condition que chaque individu donne naissance à au moins un individu. Nous déterminons aussi la valeur critique pour l'existence du moment harmonique de W sous des conditions simples d'existence de moments, qui sont bien plus faibles que les hypothèses imposées dans la littérature, et généralisons le résultat à Z_0=k individus initiaux. Le troisième chapitre est consacré à l'étude de l'asymptotique des moments harmoniques d'ordre r>0 de Zn. Nous établissons un équivalent et donnons une expression des constantes. Le résultat met en évidence un phénomène de transition de phase, relié aux transitions de phase des grandes déviations inférieures du processus (Zn). En application de ce résultat, nous établissons un résultat de grandes déviations inférieures pour le processus (Zn) sous des hypothèses plus faibles que celles imposées dans des travaux précédents. Nous améliorons également la vitesse de convergence dans un théorème central limite vérifié par W_n-W, et déterminons l'asymptotique de la probabilité de grandes déviations pour le ratio Zn+1/Z_n. / The purpose of this Ph.D. thesis is the study of branching processes in a random environment, say (Z_n), which are a generalization of the Galton-Watson process, with the reproduction law chosen randomly in each generation in an i.i.d. manner. We consider the case of a supercritical process, assuming the condition that each individual gives birth to at least one child. The first part of this work is devoted to the study of the relative and absolute distance between the normalized process log Z_n and the normal law. We show a Berry-Esseen bound and establish a Cramér type large deviation expansion, which generalize the central limit theorem and the moderate deviation principle established for log Z_n in previous studies.In the second chapter we study the asymptotic of the distribution of Z_n, and the critical value for the existence of harmonic moments of the limit variable W of the normalized population size. We give an equivalent of the asymptotic distribution of Z_n and characterize the constants by a functional relation which is similar to that obtained for a Galton-Watson process. For a branching process in a random environment, our result generalizes the equivalent of the asymptotic distribution of Z_n established in a previous work in a log-scale, under the condition that each individual gives birth to at least one child. We also characterize the critical value for the existence of harmonic moments of the limit variable W under weaker conditions that in previous studies and generalize this result for processes starting with Z_0=k initial individuals. The third chapter is devoted to the study of the asymptotic of the harmonic moments of order r>0 of Z_n. We show the exact decay rate and give an expression of the limiting constants. The result reveals a phase transition phenomenon which is linked to the phase transitions in the lower large deviations established in earlier studies. As an application, we improve a lower large deviation result for the process (Z_n) under weaker hypothesis than those stated in the literature. Moreover, we also improve the rate of convergence in a central limit theorem for W-W_n and give the asymptotic of the large deviation for the ratio Zn+1/Z_n.

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