• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 134
  • 61
  • 16
  • 13
  • 8
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 3
  • 1
  • 1
  • 1
  • Tagged with
  • 317
  • 317
  • 45
  • 40
  • 27
  • 26
  • 26
  • 21
  • 20
  • 20
  • 20
  • 19
  • 19
  • 16
  • 15
  • 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.
181

Chronic effects of silica nanoparticles in Vibrio fischeri, Raphidocelis subcaptata, Danio rerio and Allium cepa / Efeitos crônicos das nanopartículas de sílica em Vibrio fischeri, Raphidocelis subcaptata, Danio rerio e Allium cepa

Gabriela Helena da Silva 03 October 2014 (has links)
Scientific research using nanotechnology is a relatively recent development with a variety of potential applications in many fields of science. Within this field of research, many new products, with improved performances, have been developed. Despite increased research on its toxicity to ecosystem, the knowledge about this area is still limited. To evaluate the toxicity and genotoxicity of different sizes silica nanoparticles (SiNP)to the environment, different species, on different trophic levels (Vibrio fisheri, Raphidocelissubcapitata, Daniorerio and Allium cepa) were exposed to TM40 (22 nm), HS30 (12 nm), SM30 (7 nm) with concentrations ranging from0.19 to 163.8 g/L (TM40) and 0.29 to 122.85 g/L (HS30 and SM30), and the following parameters were monitored during exposure: production of bioluminescence (V. fischeri), growth rate (R. subcapitata), embryonic development and DNA damage (D. rerio) and germination rate, growth and DNA damage (A. cepa). Within each test SiNPpresent a size dependent chronic toxicity. The bioluminescence test present a EC50 of 29.11, 32.34 and 4.58 g/L for TM40, HS30 and SM30, respectively. For the growth rate assay the EC50 was 9.32, 9.07 and 7.93 g/L for TM40, HS30 and SM30, respectively. And for the zebra fish embryonic development test for TM40, HS30 and SM30, the EC50 was 5.85, 1.13 and 2.68 g/L respectively. All particles also induce phytotoxicity in A.cepa, growth and germination reduce significatively when expose to SiNP. Futhermoregenotoxic effects were also induced by the particles for both A.cepaand D. rerio. Therefore, SiNP can cause toxicity to the environment and size can strongly influence this toxicity / Com uma variedade de aplicações potenciais, em diversos campos da ciência, as pesquisas científicas utilizando nanotecnologia são de desenvolvimento relativamente recente. Dentro deste campo de pesquisa, vários novos produtos, com desempenhos melhorados têm sido desenvolvidos. Apesar do aumento de pesquisas sobre a toxicidade dessas tecnologias à biota, o conhecimento sobre esta área ainda é limitado. Visando avaliar a toxicidade e genotoxicidade denanopartículasde sílica (SiNP) no meio ambiente diferentes espécies pertencentes a diversos níveis tróficos (Vibriofisheri, Raphidocelissubcapitata, DaniorerioandAllium cepa) foram expostos a Ludox TM40 (22 nm), Ludox HS30 (12 nm) e Ludox SM30 (7 nm). As espécies de teste foram expostas a concentrações de nanopartículas (NP) variando de 0.29 a 163.8 g/L (TM40) e 0.19 a 122.85 g/L (HS30 e SM30) e os seguintes parâmetros monitorizados durante a exposição: a produção de bioluminescência (V. fischeri), o crescimento taxa (R. subcapitata), inibição de alimentação (D. magna), desenvolvimento embrionário e dano ao DNA (D. rerio) e taxa de germinação, crescimento e danos ao DNA (A. cepa). Nos testes feitos com as SiNPfoi observado que a toxicidade é dependente do tamanho da partícula. O ensaio de bioluminescência apresentou um EC50 de 29.11, 32.34 e 4.58 g/L para TM40, HS30 e SM30, respectivamente. Para o ensaio de taxa de crescimento o EC50 foi 9.32, 9.07 e 7.93 g/Lpara TM40, HS30 e SM30, respectivamente. E para o teste de desenvolvimento embrionário com peixe zebra, para o TM40, HS30 e SM30 o EC50 foi de 5.85, 1.13 e 2.68g/L, respectivamente. Todas as partículas também induziram fitotoxicidade em A. cepa, crescimento e germinação reduziram significativamente quando o organismo foi exposto a SiNP. Efeitos genotóxicos também foram induzir pelas partículas, tanto para A. cepa quanto paraD. rerio. Portanto, as SiNP podem causar toxicidade ao ambiente e o tamanho pode influenciar fortemente a essa toxicidade
182

Influencia do teor de carbono na propagação de trinca por fadiga e na tenacidade a fratura em camada cementada em aços de alta resistencia mecanica / Influence of the carbon content on propagation in cracks of fadigue and on fracture toughness in carburized case in high strenght steels

Sandor, Leonardo Taborda 01 October 2008 (has links)
Orientador: Itamar Ferreira / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-10T13:08:50Z (GMT). No. of bitstreams: 1 Sandor_LeonardoTaborda_D.pdf: 12861330 bytes, checksum: 648e60efeced3118f4ec8272c46bddcc (MD5) Previous issue date: 2008 / Resumo: Este trabalho propõe uma metodologia para avaliar pontualmente as variações de tenacidade à fratura e taxa de crescimento de trinca de fadiga ao longo da camada cementada de um aço SAE 4320. A pequena espessura dessas camadas impede a retirada de corpos de prova nas dimensões especificadas pelas normas de ensaios de tenacidade à fratura. Assim, para simular uma camada cementada retirou-se amostras de aços SAE 43xx variando-se apenas teor de carbono de 0,20 a 1,00%. Os corpos de prova após eletrodeposição de cobre foram tratados termicamente numa carga de cementação, têmpera e revenimento para serem submetidos aos efeitos térmicos sem absorção de carbono. Os resultados da análise microestrutural, dos ensaios de microdureza, de tração e de tenacidade à fratura e de taxa de crescimento de trinca de fadiga foram agrupados em um único gráfico e comparados com o perfil de cementação de peças de aço SAE 4320 tratadas nas mesmas condições. Foi confirmado que as propriedades de fadiga variam de forma inversamente proporcional à microdureza (HV1) e que a previsão do comportamento de uma trinca numa camada cementada pode ser feita por meio de equação ou diagrama que relacionam a microdureza HV1 com a tenacidade à fratura ou taxa de crescimento de trinca de fadiga (KIC ou da/dN x ??) / Abstract: The purpose of this work is to propose a methodology for evaluating the crack growth rate and the fracture toughness along the SAE 4320 steel carburized layer. Due to the small thickness of those layers, it is impossible to machine specimens from those layers in accordance with standards. For simulating the microstructures of the carburized layer in order to get samples for tensile and the fracture toughness testing, specimens of SAE 43xx, from 0.20 %C to 1.00 %C, steels melted in vacuum induction melting, hot rolled and have been machined, assuming the local influence just the variation of the content of carbon and considering that the contents of the other alloy elements are essentially constant. The specimens after electroplated copper layer were heat treated in an industrial load of carburizing, quenching, and tempering for they be submitted to the thermal effects without absorption of carbon. The results of the microstructure analysis and microhardness, crack growth rate, and the fracture toughness tests were placed in a single graph and compared with the profile of the carburizing of the steel SAE 4320 heat treated in the same conditions. It was confirmed that the crack growth rate and the fracture toughness varies inversely proportional to the microhardness (HV1) and that the forecast of the behavior of a crack in a carburized layer can be made through equation or it designs that relate the microhardness (HV1) with the fracture toughness (KIC or CTODC) and crack growth rate (da/dN X ??) / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica
183

Variabilidade espacial e temporal do fitoplâncton na zona de arrebentação da praia do Cassino (RS, Brasil): relação com os depósitos de lama e nutrientes dissolvidos

Piedras, Fernanda Reinhardt January 2012 (has links)
Tese(doutorado) - Universidade Federal do Rio Grande, Programa de Pós–Graduação em Oceanografia Biológica, Instituto de Oceanografia, 2012. / Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2013-11-19T12:24:44Z No. of bitstreams: 1 fernanda.pdf: 1386021 bytes, checksum: e67fec86c13546d730d06a2d26086f69 (MD5) / Approved for entry into archive by Angelica Miranda (angelicacdm@gmail.com) on 2013-11-20T21:40:54Z (GMT) No. of bitstreams: 1 fernanda.pdf: 1386021 bytes, checksum: e67fec86c13546d730d06a2d26086f69 (MD5) / Made available in DSpace on 2013-11-20T21:40:54Z (GMT). No. of bitstreams: 1 fernanda.pdf: 1386021 bytes, checksum: e67fec86c13546d730d06a2d26086f69 (MD5) Previous issue date: 2012 / Na zona de arrebentação de praias arenosas e expostas ocorrem acumulações de diatomáceas, as quais são importantes produtores primários. Visando entender se existe uma variação espacial e temporal do fitoplâncton na zona de arrebentação da Praia do Cassino, foram analisadas semanalmente cinco estações no período de deposição lama (maio a julho de 2009), e posteriormente (agosto de 2009 a abril 2010) três estações quinzenalmente ao longo de 21 km. As relações entre variáveis ambientais e a composição e biomassa do fitoplâncton foram comparadas, verificando-se que a deposição de lama influenciou a transparência da água, mas não foi detectada diferença significativa entre os valores médios de nutrientes e de clorofila a nas estações ao longo do ano. As diatomáceas foram dominantes, destacando-se a contribuição de cêntricas unicelulares do microplâncton e Skeletonema spp., e das penadas Asterionellopsis glacialis e Pseudo-nitzschia sp. Porém, a densidade de A. glacialis encontrada neste ano foi menor do que em anos anteriores, enquanto os gêneros planctônicos Skeletonema e Pseudo-nitzschia apareceram em alta densidade. Em laboratório foram realizados experimentos curtos com enriquecimento de nutrientes inorgânicos dissolvidos testando-se ao todo sete proporções de silicato, nitrato e fosfato, com objetivo de determinar sua influência sobre as microalgas da Praia do Cassino. Como resultado, a biomassa fitoplanctônica exibiu um aumento significativo nos tratamentos com adição de nitrato, independentemente da proporção adicionada, indicando que o nitrato é o nutriente mais importante no controle da biomassa e do crescimento das diatomáceas da Praia do Cassino. / In the surf zone of exposed sandy beaches significant accumulations of diatoms occur, which are important primary producers. In order to determine the spatial and temporal variability of phytoplankton in the surf zone, five and three stations were studied in the period with mud deposition (weekly sampling, May to July 2009) and without (every two weeks, August 2009 to April 2010), respectively, along 21 km of Cassino Beach. The relationships among environmental variables and phytoplankton composition and concentration were compared. The influence of mud was evident on the water transparency, but not on the mean values of nutrients and chlorophyll a. The diatoms were dominant, emphasizing the contribution of the unicellular centric microplankton and Skeletonema spp., and the pennates Asterionellopsis glacialis and Pseudo-nitzschia spp. However, the density of A. glacialis found in this study was lower than in previous years. Moreover, the planktonic species Skeletonema and Pseudo-nitzschia appeared in high density. In laboratory, short experiments were performed with dissolved inorganic nutrient enrichment by testing seven proportions of silicate, nitrate and phosphate, in order to determine their influence on the microalgae from Cassino Beach. In both experiments, density showed a significant increase (mainly diatoms) in the treatments with nitrate addition, regardless of the proportion added, showing that nitrate is the most important nutrient controlling diatoms density and growth at the sandy Cassino Beach.
184

Caracterização de isolados de Colletotrichum musae no Estado de Pernambuco

SANTOS, Paulo Cézar das Nações 17 February 2011 (has links)
Submitted by (lucia.rodrigues@ufrpe.br) on 2017-03-23T11:38:02Z No. of bitstreams: 1 Paulo Cezar das Merces Santos.pdf: 945938 bytes, checksum: 4dcffae9a84258c9e4e04fc53d685685 (MD5) / Made available in DSpace on 2017-03-23T11:38:02Z (GMT). No. of bitstreams: 1 Paulo Cezar das Merces Santos.pdf: 945938 bytes, checksum: 4dcffae9a84258c9e4e04fc53d685685 (MD5) Previous issue date: 2011-02-17 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / From a socioeconomic perspective, the banana, one of the most consumed fruit, has great importance worldwide. The Brazilian production of this fruit presents particular geographic distribution, since it is present in all States of the federation. In the State of Pernambuco, the banana is grown in all the regions, occupying about 80000 permanent jobs in the field, with two distinct poles of banana production: the Zona da Mata and Vale do São Francisco. Among the limiting factors for this crop, there are the post-harvest diseases such as anthracnose, caused by Colletotrichum musae. This disease causes significant losses in production, manifesting itself mainly in the fruit at maturity stage. In order to verify the diversity of this pathogen isolated from C. musae from banana production fields of three municipalities (Vicência, São Vicente Férrer and Machados) of the Pernambuco State were characterized for daily mycelial growth rate (DMGR), colony color, reverse plate, topography, presence of sectors and microsclerotia, conidial morphology, biochemical tests, pathogens and molecular. The 60 isolates, based on morphological characters of shape and size of conidia, were identified as C. musae, followed with morphological measurements from 9.3 to 30.2 x 2.6 to 12.6 μm ( x = 15.0 x 4.9 μm, n = 6000). Most isolates showed conidia straight, oblong, with rounded apices. As for the DMGR, all isolates showed growth averaged more than 1.0 cm.day–1, ranging from 1.21 to 1.63 cm.day–1. It was found three groups of striking color to the colonies: white, cream and salmon, while the presence of sectors ranging from zero to eight per isolate. Most isolates (53) metabolized the ammonium tartrate as the sole source of carbon, while for citric acid, all isolates except the isolate CMM 3219, were not able to metabolize this carbon source. The pathogenic characterization showed significant differences in the epidemiological parameter AUDPC in fruits inoculated with injury, indicating the existence of variation in aggressiveness among isolates. For fruit inoculated and no injuries, the AUDPC was not estimated for 20 isolates because there was no injury. The dendrogram generated by UPGMA (Unweighted Pair Group Method with Arithmetic Mean) cluster analysis of DNA bands obtained with the combination of three primers (GTG5, GACA and 820) by ISSR-PCR allowed the separation of three groups of isolates to 62% by Jaccard’s similarity coefficient. The group I was composed of isolates from Vicência Group II isolates São Vicente Férrer and group III, Machados. The results suggest that isolates of C. musae can be discriminated as to their origin because they had genetic similarity between them. The ISSR markers in this study appear to be useful tools in the study of C. musae. / Do ponto de vista socioeconômico, a banana, uma das frutas mais consumidas, possui grande importância mundial. A produção brasileira dessa frutífera apresenta particular distribuição geográfica, já que está presente em todos os Estados da federação. No Estado de Pernambuco, a banana é cultivada em todas as microrregiões, ocupando cerca de 80 mil postos de trabalho permanente no campo, havendo dois pólos distintos de produção de banana: a Zona da Mata e o Vale do São Francisco. Dentre os fatores limitantes para esta cultura, destacam-se as doenças pós-colheita, como a antracnose, causada pelo fungo Colletotrichum musae. Essa doença causa perdas significativas na produção, manifestando-se, principalmente, na fruta em estádio de maturação. Com a finalidade de verificar a diversidade desse fitopatógeno, isolados de C. musae provenientes de campos de produção de banana de três municípios (Vicência, São Vicente Férrer e Machados) do Estado de Pernambuco foram caracterizados quanto à taxa de crescimento micelial diária (TCMD), coloração da colônia, reverso da placa, topografia, presença de setores e de microescleródios, além da morfologia de conídios, testes bioquímicos, patogênicos e moleculares. Os 60 isolados, com base nos caracteres morfológicos de formato e tamanho de conídios, foram identificados como C. musae, com as seguidas medidas morfológicas 9,3-30,2 x 2,6-12,6 μm ( x = 15,0 x 4,9 μm, n = 6000). A maioria dos isolados avaliados apresentaram conídios retos, oblongo, com ápices arredondados. Quanto à TCMD, todos os isolados apresentaram crescimento médio superior a 1,0 cm.dia–1, variando de 1,21 a 1,63 cm.dia–1. Foram encontrados três grupos marcantes de coloração de colônia: branca, creme e salmão, enquanto que a presença de setores variou de zero a oito por isolado. A maioria dos isolados (53) metabolizou o tartarato de amônio como fonte exclusiva de carbono, enquanto que para o ácido cítrico, todos os isolados, com exceção do isolado CMM 3219, não foram capazes de metabolizar essa fonte de carbono. A caracterização patogênica mostrou diferenças significativas para o parâmetro epidemiológico AACPD em frutas inoculadas com ferimento, indicando a existência de variação da agressividade entre os isolados. Para as frutas sem ferimentos e inoculadas, a AACPD não foi estimada para 20 isolados, pois não houve lesões. O dendrograma gerado pela análise de agrupamento UPGMA (Unweighted Pair Group Method with Arithmetic Mean) das bandas de DNA obtidas com a combinação dos três primers (GTG5, GACA e 820) por ISSR-PCR possibilitou a separação de três grupos de isolados a 62% pelo coeficiente de similaridade de Jaccard. O grupo I foi formado pelos isolados provenientes de Vicência; grupo II, isolados de São Vicente Férrer e grupo III, de Machados. Os resultados sugerem que isolados de C. musae podem ser discriminados quanto à sua origem por apresentarem similaridade genética entre si. Os marcadores ISSR, nesse estudo, parecem ser ferramentas bastante úteis no estudo populacional de C. musae.
185

Interação entre Cylindrospermopsis raciborskii e Microcystis aeruginosa: implicações no crescimento de culturas e na produção de microcistinas / Interaction between Cylindrospermopsis raciborskii and Microcystis aeruginosa: implications in cultures growth and microcystins production

Paulo Vagner dos Santos 18 June 2009 (has links)
Cianobactérias desempenham importante papel ecológico em diversos ecossistemas terrestres e aquáticos. Contudo, tornam-se problema de saúde pública quando biossintetizam compostos secundários tóxicos, denominados cianotoxinas, as quais podem atuar sobre diversos organismos. Sistemas aquáticos impactados favorecem o desenvolvimento destes microrganismos, que podem tornar-se dominantes em função dos diversos mecanismos que lhes conferem vantagens adaptativas em relação aos demais grupos fitoplanctônicos. Muitas vezes, elas apresentam-se sob forma de florescimento, cuja toxicidade varia de acordo com espécies e cepas que o compõem. Apesar das cianobactérias Cylindrospermopsis raciborskii e Microcystis aeruginosa formarem florações, terem potencial tóxico, serem competitivas e estarem presentes em diversos reservatórios, é desconhecido o efeito da interação entre elas na produção de microcistina. Para esclarecer esta questão, nesta pesquisa, foi estudada a interação entre cepas de C. raciborskii e M. aeruginosa visando: caracterizar o cultivo das espécies em monocultura e cultura mista; verificar se o caráter tóxico das cepas favoreceu a competição; mensurar a microcistina de M. aeruginosa e avaliar o efeito da interação sobre esta variável. Em salas climatizadas de cultivo (22ºC, fotoperíodo 12h, 60 \'mü\'mol photon/\'M POT.2\'.s) experimentos de interação foram realizados em culturas batch compostas por três tratamentos: (1) monocultura de M. aeruginosa, (2) monocultura de C. raciborskii, (3) cultura mista de M. aeruginosa e C. raciborskii. Foram realizadas análises da densidade e biovolume dos organismos, da velocidade específica de crescimento (\'mü\') e tempo de duplicação (Td) e da concentração de microcistinas, clorofila-a e nutrientes. A interação reduziu em até 22% a \'mü\' das linhagens estudadas. Tanto C. raciborskii quanto M. aeruginosa apresentaram vantagem competitiva em pelo menos um dos ensaios e, no caso de linhagem tóxica de M. aeruginosa, verificou-se que o seu caráter tóxico favoreceu a competição da espécie com linhagem atóxica de C. raciborskii. Além disso, M. aeruginosa elevou em até 53% a síntese de microcistina ao interagir com C. raciborskii. Este processo poderia se relacionar a três principais mecanismos: competição por interferência, produção de alelopáticos e comunicação química. Estudos de balanços genéticos dos florescimentos bem como da possível comunicação química existente entre cianobactérias são ferramentas investigativas importantes que poderão ajudar no aprimoramento da prevenção e manejo de florações tóxicas. / Cyanobacteria play important ecological role in many terrestrial and aquatic ecosystems. However, they become a public health problem when synthesize secondary toxic compounds, known as cyanotoxins, which may act on several organisms. Impacted aquatic systems favor their growth and these microorganisms can become dominant due to mechanisms that confer them adaptive advantages in relation to other phytoplanktonic groups. Frequently, cyanobacteria can form water blooms, whose toxicity varies according to their species and strains composition. Although the cyanobacteria Cylindrospermopsis raciborskii and Microcystis aeruginosa can form blooms, have toxic potential, are competitive and present in several reservoirs, it is unknown the interaction effect between them in the production of microcystins. To solve this question, the interaction among strains of C. raciborskii and M. aeruginosa was studied to: characterize the culture of the species in monoculture and mixed culture; check whether the character of toxic strains favored the competition; measure microcystin concentration produced by M. aeruginosa and evaluate interaction effect on this variable. In climatized growth room (22°C, 12h photoperiod, 60 \'mü\'mol photon/\'M POT.2\'.s) four interaction experiments composed by three treatments were performed in batch cultures: (1) monoculture of M. aeruginosa, (2) monoculture of C. raciborskii, (3) mixed culture of M. aeruginosa and C. raciborskii. Density and biovolume, specific growth rate (\'mü\'), doubling time (Td) and concentration of microcystin, chlorophyll-a and nutrients analyses were performed. The interaction reduced up to 22% the of studied strains. Both C. raciborskii and M. aeruginosa presented competitive advantage in at least one of the tests. In the case of toxic strain of M. aeruginosa, it was found that its toxic character favored the competition with non-toxic strain of C. raciborskii. Furthermore, M. aeruginosa increased by 53% the synthesis of microcystin while interacting with C. raciborskii. This process could be related to three main mechanisms: interference competition, communication and production of allelopathic chemicals. Genetical balance studies of blooms as the possible chemical communication existing among cyanobacteria are important investigative tools that might help prevention and management improvement of toxic blooms.
186

Host range of lichenivorous moths with special reference to nutritional quality and chemical defence in lichens

Pöykkö, H. (Heikki) 30 November 2005 (has links)
Abstract Host use and range of herbivorous insects are determined by several factors, of which nutritional quality and secondary chemistry have been shown to play very important roles. For herbivores feeding on lichens these traits are assumed to be more critical than for species feeding on higher plants, since lichens are nutritionally poor and often contain high concentrations of secondary metabolites. I examined the role of lichens' nutritional quality and secondary chemicals on the performance of lichen-feeding Lepidopteran larvae. I also tested whether females of lichenivorous species preferably oviposit on host species of the highest nutritional quality for the growth of larvae. Larvae of Eilema depressum performed best on Melanelia exasperata, which is of the highest nutritional quality, as indicated by the high N concentration and the absence of lichen secondary metabolites compared to the other lichens studied. Host nutritional quality did not promote the production of an additional generation. Larvae of E. depressum needed fewer instars and grew bigger on a high-quality diet than larvae reared on a diet of poorer quality. However, the main factor contributing to the wide variation in the number of larval instars was the question of whether or not larvae overwintered. Growth of Cleorodes lichenaria at the beginning of the larval period matched equally the nutritional quality of the hosts. However, the final larval period was shortest on Ramalina species, which was preferred by both females ovipositing their eggs and larvae searching for a host. In the field, larvae were found almost exclusively on Ramalina species. Larvae of E. depressum were not able to survive on intact thalli of Vulpicida pinastri and Hypogymnia physodes, but after removal of lichen's secondary metabolites, larval survival remained equally high as on other lichens. Larvae also showed a clear preference towards thalli with lowered concentrations of secondary metabolites in Parmelia sulcata, V. pinastri and H. physodes. Parietin in Xanthoria parietina was the only secondary metabolite that had no impact on the survival or host selection of E. depressum larvae. The present results show that the nutritional quality and some lichen secondary chemicals are important factors for the growth, survival and host selection of lichen-feeding Lepidopteran larvae. The preference-performance hypothesis is at least partly able to explain the host range of C. lichenaria, although it seems that there are also other factors, such as larval dispersal and host selection or top-down forces, that might contribute to host range of lichenivorous Lepidopteran larvae. Moreover, lichenivorous larvae seem to be partly responsible for their own host selection.
187

The Relationship between Human Capital and Economic Growth in Developing Countries : A Study and Analysis on Developing Countries

Khatri Chhetri, Surya Bahadur January 2017 (has links)
Abstract The purpose of the thesis has been to investigate the relation between human capital and economic growth in developing countries around the world. The main research question is how the human capital impact on the economic growth in developing countries during the period of 2010 -2015.The world is mainly divided into two major groups, which are Developed & Developing countries, as well as poor & rich countries. In this thesis mainly concern only developing and poor countries and their role of the economic growth. The key factors of economic growth are GDP/capita, per capita income, birth rate, death rate, population growth rate, life expectancy at birth, working age population, education, literacy rate and investment in technology. The world is populated day by day such has never been before. In the past history it look back to 123 years to increased from one billion to two billion from 1804 to 1927.Then, next billion took 33 years. The following two billions took 14 years and 13 years, respectively (Ray, Development Economics).             The data has been taken from the Developing countries around the world which is taken a cross sectional data set and data has been analysed with multiple liner regressions model with ordinary least squares (OLS). For this purpose which applied the difference tools & theory which are human capital and technology development, economic growth, norms, externalities and human social capital.   The previous studies is examined the most important factors of economic development that is economic growth and human capital investment. Similarly, the theoretical discussion is described the Solow model, human capital theory, technological progress, demographic transition and social capital. For examine the data is divided into two groups which are dependent and independent variables. Economic growth GDP/capita, GDP/capita growth rate are dependent variable and Ln. GDP initial, life expectancy at birth, population growth rate, education, working age population and investment in technology are independent variables.   This analysis shows the majority of the variables in the study have positive significant relation to the GDP/capita growth. This result furthermore support the developing countries provides insight on the world economic development status towards the independents variables.
188

Redshift-space distortions as a probe of dark energy

Gouws, Liesbeth-Helena January 2014 (has links)
>Magister Scientiae - MSc / We begin by finding a system of differential equations for the background and linearly perturbed variables in the standard, ɅCDM model, using the Einstein Field Equations, and then solving these numerically. Later, we extend this to dynamical dark energy models parameterised by an equation of state, w, and a rest frame speed of sound, cs. We pay special attention to the large-scale behaviour of Δm, the gauge invariant, commoving matter density, since the approximation Δm ≃ δm, where δm is the longitudinal gauge matter density, is more commonly used, but breaks down at large scales. We show how the background is affected by w only, so measurements of perturbations are required to constrain cs. We examine how the accelerated expansion of the universe, caused by dark energy, slows down the growth rate of matter. We then show the matter power spectrum is not in itself useful for constraining dark energy models, but how redshift-space distortions can be used to extract the growth rate from the galaxy power spectrum, and hence how redshift-space power spectra can be used to constrain different dark energy models. We find that on small scales, the growth rate is more dependent on w, while on large scales, it depends more on cs.
189

Zdroje prognóz vývoje jednotlivých odvětví pro potřeby oceňování podniku / Forecast sources for selected individual industries for business valuation purposes

Navrátil, David January 2013 (has links)
The aim of this thesis is to identify and according to selected criteria to evaluate the forecast sources for selected individual industries. The first section summarizes current situation in area of forecast sources for development of individual sectors. The second part presents outline of procedure for forecast sources identification and research. Then follows selection of individual industries that will be analyzed. Part of the second section is introduction of the evaluation criteria as well as methodology for the final assessment. Third part of the thesis is focused on practical work consisting of identification and searching for the sources for individual industries, their detailed evaluation based on established criteria and final assessment of individual sources for each sector. Third part is followed by summary and description of the findings and recommendations.
190

Growth-rate-dependent protein production in bacteria / Impact du taux de croissance sur la production des protéines chez les bactéries.

Borkowski, Olivier 19 February 2013 (has links)
Les théories actuelles suggèrent que l'efficacité de traduction (nombre de protéines produitespar ARN messager ; notion spécifique à chaque à gène) reste constante lorsque le taux decroissance varie. Néanmoins, une efficacité de traduction constante est incompatible avec lafaible corrélation observée, à l’échelle du génome, entre l’évolution en fonction du taux decroissance de la concentration des ARN messagers et des protéines pour lesquelles ils codent.Pour faire face à ce paradoxe, nous avons développé un modèle mathématique de la traductionbasé sur les connaissances actuelles de ce processus au niveau moléculaire. L’exploration despropriétés du modèle nous a amené à conduire des expériences de transcriptomique, de PCRquantitative et de Live Cell Array (LCA) dont l’analyse a montré que l'efficacité de traductiondiminue jusqu'à 4 fois entre faible et fort taux de croissance chez la bactérie modèle Bacillussubtilis. Notre modèle a révélé que la chute de l’efficacité de traduction repose sur une chutede la concentration des ribosomes libres. Pour étudier les conséquences de la chute desribosomes libres sur la production des protéines, nous avons rationnellement défini à partir dumodèle mathématique des constructions génétiques combinant des promoteurs, naturel ousynthétique, et différentes régions d'initiation de la traduction (TIRs) contrôlant l’expressiondu gène gfp. En utilisant ces constructions génétiques, nous avons montré que la productiondes protéines est non-linéaire en fonction de la concentration en ribosomes libres. Uneproduction non-linéaire entraine des efficacités de traduction différentielles des ARNmessagers en fonction de leurs TIRs. Ce mécanisme de régulation général des protéinesparticipe à la perte de corrélation entre la concentration des ARN messagers et des protéinescorrespondantes et nous a amené à revisiter la Physiologie Moléculaire Bactérienne. / Current theories suggest that translation efficiency (i.e. number of proteins produced permRNA) remains invariant with increasing growth rate, which is inconsistent with the scanty correlation between mRNAs and cognate proteins abundances at the genome-scale level. We tackled this apparent paradox using a systems biology approach. We developed a knowledgebased, nonlinear mathematical model of translation. The in-depth analysis of the model led us to reassess experimentally, using high-throughput and genome-wide technologies, each measurable RNA entity at different growth rates. In contrast to the current knowledge, the total mRNA abundance was not constant but linearly increased with respect to the growth rate. A model-driven integration of genome-wide and molecular experimental datasets demonstrated that the drop in abundance of a constitutively expressed protein with increasing growth rate is not only due to the dilution but also to an unexpected up to 4-fold decrease of translation efficiency. Our model revealed that this drop relies on a drastic decrease in free (untranslating) ribosomes, a non-measurable entity. Using a set of 18 Bacillus subtilis strains combining 9 synthetic translation initiation regions (TIRs) and 2 constitutive promoters, we show that TIRs together with free ribosome abundance strongly contribute to a nonlinear modulation of single proteins as a function of the growth rate. The nonlinearity accounted for the loss of correlation between mRNAs and cognate proteins abundances. Altogether, our results evidenced a unique, hard-coded and global growth-rate-dependent regulation of single bacterial proteins without dedicated regulators.

Page generated in 0.0614 seconds