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Temperature analysis on fire resistance experiments of partially encased beams

Piloto, P.A.G.; Ramos Gavilán, A.B.; Mesquita, L.M.R.
Fonte: WIT Press Publicador: WIT Press
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.07%
Twelve fire resistance tests, grouped in four series, were developed using partially encased beams (PEB) without concrete slab, for different load level and shear connection. PEB were built with standard hot rolled IPE100 profile and reinforced concrete between flanges. Fire resistance was determined for standard ISO834 nominal heating curve, using small fire resistance furnace and portal frame. Temperature was measured in three different sections along PEB length, for three different materials (steel, concrete and reinforcement). Average temperature in each section and material was compared to the average over length temperature. Each series presented similar results, with good reproducibility. Special focus was given to critical temperature. The maximum temperature difference between sections S1, S2, S3 and the average element length temperature is smaller than 3.2 % for test series 1. For test series 2, 3 and 4 the maximum temperature difference is smaller than 5.1%, 6.3% and 11.2%, respectively. Temperature is not uniform in cross-section. After the initial heating stage, temperature revealed a constant difference of approximately 150ºC between temperatures measured inside and outside, defining two main temperature evolutions. Temperatures measured outside revealed always higher temperature level.

Temperature assessment on fire resistance experiments of partially encased beams

Piloto, P.A.G.; Gavilán, Ana; Mesquita, L.M.R.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.07%
Twelve fire resistance tests, grouped in four series, were developed using partially encased beams (PEBs) without concrete slab, for different load levels and shear condition. PEBs were built with standard hot rolled IPE100 profile and reinforced concrete between flanges. Fire resistance was determined for standard ISO834 nominal fire curve, using small fire resistance furnace and portal frame. Temperature was measured in three different sections along PEB length (S1, S2, S3), for three different materials (steel, concrete and reinforcement). Average temperature in each section and material was compared with the average temperature over length. Each series presented similar results, with good reproducibility. Special focus was given to critical temperature. The maximum temperature difference between sections and the average temperature of element length is smaller than 3.2%, 5.1%, 6.3% and 11.2%, for test series 1, 2, 3 and 4, respectively. Temperature is not uniform in cross-section. After the initial heating stage, temperature revealed a constant difference of approximately 150°C between temperatures measured inside and outside, defining two main temperature evolutions. Temperatures measured outside revealed always higher temperature level.

Variação da temperatura intramuscular durante e após a aplicação cutânea de frio e calor superficial.; Variation of the intramuscular temperature during and after cutaneous application of cold andsuperficial heat

Gomes, Elizabete Dias Flauzino Gaspar
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 31/08/2001 PT
Relevância na Pesquisa
36.08%
A utilização do frio e calor superficial, com propósitos terapêuticos é antiga, e seus efeitos ainda apresentam inúmeras controvérsias. Este experimento objetivou determinar as variações de temperatura em planos musculares profundos durante e após aplicação de frio e calor superficial na região cutânea adjacente.Foram usados 5 cães mestiços submetidos à implantação cirúrgica (músculo longo do tronco) de sensor térmico (PT100), em profundidade de 3 cm. Foi aplicado frio na pele adjacente, durante 30 min, em 3 dias consecutivos, em área delimitada,usando bolsa de gelo triturado, verificando temperatura a cada 5 min durante a aplicação e 30 min após cessar a aplicação. No 4º dia (pós-operatório) foram iniciadas as aplicações de calor superficial, durante 20 min (bolsa de gel a 55ºC), por 3 dias, verificando temperatura a cada 5 min durante a aplicação e mais 20 min após cessar a aplicação. Os dados de temperatura x tempo foram analisados descritivamente. Durante a aplicação de frio houve uma queda rápida da temperatura na interface com variação média de 23ºC, com tempo médio de alcance da temperatura mínima em 24 min. A região intramuscular apresentou variação lenta (média de 4,30ºC)...

Efeito da temperatura e da UR na biologia de Liriomyza trifolii (Burgess, 1880) (Diptera: Agromyzidae) em Vigna unguiculata (L.) Walp.; Effect of temperature and RH on the biology of Liriomyza trifolii (Burgess, 1880) (Diptera: Agromyzidae) in Vigna unguiculata (L.) Walp.

Costa-Lima, Tiago Cardoso da
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/01/2008 PT
Relevância na Pesquisa
36.07%
Esta pesquisa teve como o objetivo estudar a influência da temperatura e da umidade relativa do ar (UR) nos aspectos biológicos da mosca-minadora, Liriomyza trifolii (Burgess, 1880), em feijão caupi [(Vigna unguiculata (L.) Walp.)], para fornecer subsídios a futuros projetos de controle biológico desta praga. Verificou-se uma relação inversa entre a duração de desenvolvimento e o aumento da temperatura na faixa de 15 a 32°C. A viabilidade larval não foi afetada na faixa térmica estudada, enquanto a 32°C houve uma alta mortalidade da fase de pupa. O limiar térmico inferior de desenvolvimento obtido para o período ovo-adulto foi baixo (7,3°C), se comparado a outras espécies de Liriomyza, sendo bastante reduzido para a fase larval (3,4°C). De acordo com as exigências térmicas constatadas para L. trifolii, foi possível estimar a ocorrência de 24,5 gerações anuais em região produtora de melão no RN, sendo que apenas durante a safra da cultura, a praga pode dar 14,8 gerações. A longevidade dos adultos decresceu com a elevação térmica, sendo sempre maior para as fêmeas, independente da temperatura. Os períodos de pré-oviposição e oviposição também foram reduzidos com o aumento da temperatura. A fecundidade foi similar na faixa de 18 a 30°C...

Influência da temperatura no crescimento e nas respostas fisiológicas do Surubim do Paraíba Steindachneridion parahybae (Siluriformes: Pimelodidae) criados em cativeiro; Influence of temperature in growth and physiological responses in Surubem dy Paraíba Steindachneridion parahybae (Siluriformes: Pimelodidae) in captivity

Tolussi, Carlos Eduardo
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 09/12/2010 PT
Relevância na Pesquisa
36.08%
As mudanças climáticas devido às ações antrópicas tendem a alterar diversos fatores ambientais, entre eles a temperatura. Um recente prognóstico sobre a elevação da temperatura menciona que em uma escala otimista a temperatura na Terra se elevará em 1.8 graus C até 2100. Esta alteração pode causar diversas modificações nos processos fisiológicos, justificando a realização de estudos para avaliar os efeitos da temperatura na fisiologia dos animais. A Bacia do Paraíba do Sul há muito tempo, vem sofrendo com ações antrópicas, culminando no risco de extinção de espécies endêmicas, sendo este o caso do surubim do Paraíba, Steindachneridion parahybae. Com a possível elevação da temperatura ambiental o risco de extinção da espécie pode se tornar ainda mais eminente, sendo assim, o objetivo do presente trabalho é avaliar se a variação da temperatura da água, dentro dos valores previstos na escala otimista, de 1,8 graus C influencia o crescimento e as respostas fisiológicos dos juvenis de surubim do Paraíba. Foi estabelecido um modelo experimental no qual dois tanques foram cobertos com uma estufa de plástico (grupo Estufa) e outros dois tanques permaneceram sem cobertura (grupo Sem Estufa), com um número inicial de 100 peixes em cada tanque. Nos meses de setembro de 2009 (início)...

Composição química dos grãos e da cera foliar de variedade Glycine max (L.) Merrill cv. MG/ BR-46 Conquista cultivada sob atmosfera enriquecida de gás carbônico e temperatura elevada; Chemical composition of seeds and leaf waxes of the variety Glycine max (L.) Merrill cv. MG/BR-46 Conquista grown under enrichment of atmospheric carbon dioxide and elevated temperature

Jara, Carmen Eusebia Palacios
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 05/11/2012 PT
Relevância na Pesquisa
36.07%
A concentração do gás carbônico (CO2) tem aumentado nas últimas décadas, devido principalmente à queima de combustíveis fósseis. Como consequência, admite-se que haverá gradual aumento da temperatura atmosférica em nível global. A soja é importante planta agrícola em todo o mundo, consumida na alimentação humana e de animais domésticos. O presente trabalho compõe-se de dois capítulos, o primeiro versando sobre o efeito da concentração de gás carbônico e da temperatura sobre vários parâmetros bioquímicos e o segundo, sobre a composição da cera foliar cuticular de uma variedade de soja. O capítulo I trata da composição química dos grãos e do teor de ceras foliares de plantas da cultivar 'MG/BR-46 Conquista' crescendo em câmaras de topo aberto sob duas condições de CO2 (380ppm ambiente e 800ppm elevado) e duas condições de temperatura (ambiente e elevada [+5°C]). Foram coletados dados de 6 coletas ao longo de 105 dias de desenvolvimento da planta. As plantas crescidas em altas concentrações de CO2 aumentaram a biomassa seca da folha, caule, raiz e frutos, além do número de sementes; temperaturas elevadas estimularam a senescência precoce. A floração foi antecipada sob condição de CO2 elevado. Entre os carboidratos dos grãos...

Expressão histoimunológica de proteínas de reparo celular e comportamento de juvenis de Trachinotus carolinus (Linnaeus, 1766) (Perciformes, Carangidae) durante aumento gradual de temperatura; Histoimmunology of cellular repair proteins and behavior of juvenile Trachinotus carolinus (Linnaeus, 1766) (Perciformes, Carangidae) during gradual increase of temperature

Cardoso, Caroline Margonato
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/05/2013 PT
Relevância na Pesquisa
36.07%
A temperatura é um fator abiótico que exerce profundos efeitos no funcionamento dos ecossistemas marinhos, influenciando na biologia das espécies. Os peixes são um bom modelo para se estudar este fator, pois são pecilotérmicos e possuem importância comercial e ecológica. O objetivo deste trabalho foi analisar o comportamento, a tolerância térmica e os mecânicos moleculares de juvenis de peixe pampo Trachinotus carolinus em relação à elevação da temperatura. Para isso, foram submetidos ao aumento controlado da temperatura da água (2°C/h) a partir da temperatura de coleta (22°C) até 26°C, 30°C, 32°C, 34°C e 36°C e nestas foram mantidos por 120 minutos, ou foram aquecidos até a morte no estudo de tolerância térmica. O comportamento foi analisado usando-se vídeos e as expressões de Hsp70 e p53 nas brânquias e no coração dos pampos foram obtidas por meio da técnica de imuno-histoquímica Os resultados mostraram que os pampos comportam-se de forma agitada com o aquecimento até a temperatura de 36°C, e a partir dela apresentam uma desorganização dos sistemas e órgãos. A expressão de Hsp70 e p53 está relacionada ao aumento de temperatura até 34°C e decai nas temperaturas de 36°C e TCS. Assim, conclui-se que o aumento de temperatura afeta o comportamento e a expressão de Hsp70 e p53.; Temperature is an abiotic factor that influences the biology of marine species. Fishes are a good model to study temperature because they are poikilothermic and have ecological and commercial importance. The aim of this study was to analyze the behavior and study the expression of Hsp70 and p53 using the immunohistochemistry assay. The Expression of these two protein was observed in relation to temperature rise in heart and gills tissues of juvenile pompano fish Trachinotus carolinus. The Fishes were exposed to controlled increase of the water temperature (2°C/h)...

Incubation and rearing temperature effects on Hsp70 levels and heat stress response in broilers

Givisiez, P. E. N.; Furlan, R. L.; Malheiros, E. B.; Macari, Marcos
Fonte: Agricultural Inst Canada Publicador: Agricultural Inst Canada
Tipo: Artigo de Revista Científica Formato: 213-220
ENG
Relevância na Pesquisa
36.07%
Incubation temperature (IT) was changed to evaluate if 6-wk-old birds become more tolerant to heat stress. After 13 d of incubation, 470 eggs were submitted to low (36.8degreesC), normal (37.8degreesC) and high (38.8degreesC) temperatures. At day 7 post-hatching, 144 birds were allocated to three rearing temperatures (48 birds/treatment): control/thermoneutral (35-24degreesC), high (33-30degreesC) or low (27-18degreesC) according to the age of the birds. Hsp70 levels in tissues of birds (1 d and 42 d), stress response (42 d) and performance were evaluated. High IT decreased brain (P < 0.01) and liver (P < 0.01) Hsp70 levels, whereas low IT decreased brain (P < 0.01) but increased heart (P < 0.01) Hsp70 levels in 1-d-old chicks. Birds incubated at a low temperature had higher (P < 0.05) feed intake (1-42d). High rearing temperature decreased feed intake (P<0.01) and liveweight (P<0.01). Colonic temperature was lower in birds incubated at a low temperature (P < 0.05) and higher in birds reared in a high temperature (P < 0.05) before heat stress. Birds reared in low temperature had higher increase in colonic temperature after heat stress (P < 0.05). Tissue Hsp70 levels were differently affected by rearing temperature, which affected broiler performance more than IT. Lower IT seemed to increase the sensitivity of birds to heat stress at market age.

Effect of breeder age on eggshell thickness, surface temperature, hatchability and chick weigh

Gualhanone, A.; Furlan, Renato Luis; Fernandez-Alarcon, M. F.; Macari, Marcos
Fonte: Fundação APINCO de Ciência e Tecnologia Avícolas Publicador: Fundação APINCO de Ciência e Tecnologia Avícolas
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.07%
Two experiments were carried out to study the effect of breeder age on incubation parameters (hatchability, eggshell thickness, egg surface temperature and chick weight). In Exp. 1, fertile eggs (30- and 60-wk-old breeders) were incubated at three different temperatures (36.8, 37.8 and 38.8 ºC). Eggshell surface temperature was measured by attaching a thermocouple to the shell and data were collected in a datalogger every ten minutes. This study was conducted according to a 3 x 2 factorial design (three temperatures and two breeder ages). Data revealed that eggshell surface temperature changed according to incubation temperature, with the main increase occurring between 10 and 13 days of incubation, and that the maximum increase in eggshell surface temperature was not higher than +0.6 ºC, irrespective of incubator temperature. The incubator temperature affected total incubation period and hatchability (%) at 38.8 ºC, independent of breeder age. Heavier eggs resulted in heavier chicks, irrespective of incubator temperature. In Exp 2, the eggs (30- and 60-wk-old breeders) were incubated at 37.8 ºC and eggs characteristics (weight, specific gravity, total hatchability and chicks weight) were evaluated according to a randomized experimental design. The data showed that breeder age affected eggshell thickness and chick weight (heavier eggs resulted in heavier chicks)...

Genetic group x ambient temperature interaction effects on physiological responses and growth performance of rabbits

Zeferino, C. P.; Moura, A. S. A. M. T.; Fernandes, S.; Kanayama, J. S.; Scapinello, C.; Sartori, J. R.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 177-183
ENG
Relevância na Pesquisa
36.08%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); The objective of this study was to evaluate the effects of the interaction between genetic group (Botucatu or crossbred) and ambient temperature (thermoneutral, moderate or intense heat stress) on physiological indicators and performance of growing rabbits. Ninety-six weaned rabbits were used, half from the Botucatu genetic group and half crossbreds (New Zealand White males x Botucatu females). They were assigned to a completely randomized design in a 2 x 3 factorial arrangement (two genetic groups and three ambient temperatures) with repeated measures (weeks). Colonic temperature, skin surface temperature, ear surface temperature, and respiratory rate were recorded from 42 to 67 days of age, whereas body weight and feed intake were recorded from 35 to 70 days of age. Average ambient temperature and relative humidity in the environmental chambers were 18.4 degrees C and 63.9% (thermoneutral), 24.4 degrees C and 80.2% (moderate heat stress) and 29.6 degrees C and 75.9% (intense heat stress). Mean colonic temperatures ranged from 39.4 to 39.7 degrees C across treatments. Botucatu rabbits showed higher (P<0.05) skin surface temperature under moderate heat stress than the crossbreds (33.0 +/- 0.1 vs. 32.6 +/- 0.1 degrees C...

Effects of Temperature on Intraspecific Competition in Ectotherms

Amarasekare, Priyanga; Coutinho, Renato M.
Fonte: Univ Chicago Press Publicador: Univ Chicago Press
Tipo: Artigo de Revista Científica Formato: E50-E65
ENG
Relevância na Pesquisa
36.09%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Understanding how temperature influences population regulation through its effects on intraspecific competition is an important question for which there is currently little theory or data. Here we develop a theoretical framework for elucidating temperature effects on competition that integrates mechanistic descriptions of life-history trait responses to temperature with population models that realistically capture the variable developmental delays that characterize ectotherm life cycles. This framework yields testable comparative predictions about how intraspecific competition affects reproduction, development, and mortality under alternative hypotheses about the temperature dependence of competition. The key finding is that ectotherm population regulation in seasonal environments depends crucially on the mechanisms by which temperature affects competition. When competition is strongest at temperatures optimal for reproduction, effects of temperature and competition act antagonistically, leading to more complex dynamics than when competition is temperature independent. When the strength of competition increases with temperature past the optimal temperature for reproduction...

The Effect of Culture Temperature on Recombinant IFN-γ Production and Quality

Fox, Steven R.; Yap, Miranda G.S.; Wang, Daniel I.C.
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 236677 bytes; application/pdf
EN_US
Relevância na Pesquisa
36.09%
The goal of this research project is to analyze the effect of culture temperature on the production and quality of IFN-γ produced and secreted by suspension culture CHO cells.The effect of low temperature on IFN-γ glycosylation, which is under the control of a battery of enzymes whose activities will be influenced by temperature, is unknown. Work is focused on implementing a system for accurately monitoring the glycosylation of IFN-γ and then using the system for quantifying the effect of culture temperature on glycosylation. The system consists of immunoaffinity purification of IFN-γ , followed by capillary electrophoresis for determining glycosylation macroheterogeneity and MALDI-TOF MS and HPLC for determining glycosylation microheterogeneity. Initial results suggest that glycosylation macroheterogeneity is slightly decreased (~5%) at low temperature, thereby identifying a potential quality “bottleneck” for the use of low temperature to increase IFN-γ production. Low temperature (32°C) shifts the cells towards the non-growth, G1 portion of the cell cycle. In batch culture, if cells are shifted to low temperature once a reasonably high cell density is reached, an approximately 4-fold improvement in total IFN-γ production compared to 37°C culture is achieved. Pseudo-continuous culture was used to show that IFN-γ production is statistically significantly higher at 32°C compared to 37°C even when nutrient depletion is not a concern (p < 0.5). In fed-batch bioreactor culture...

The effects of temperature on nickel tocicity in goldfish (carassius auratus L.)

Norris, Stacey L.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
Relevância na Pesquisa
36.12%
Although it is widely assumed that temperature affects pollutant toxicity, few studies have actually investigated this relationship. Moreover, such research as has been done has involved constant temperatures; circumstances which are rarely, if ever, actually experienced by north temperate, littoral zone cyprinid species. To investigate the effects of temperature regime on nickel toxicity in goldfish (Carassius auratus L.), 96- and 240-h LCSO values for the heavy metal pollutant, nickel (NiCI2.6H20), were initially determined at 2DoC (22.8 mg/L and 14.7 mg/L in artificially softened water). Constant temperature bioassays at 10°C, 20°C and 30°C were conducted at each of 0, 240-h and 96-h LCSO nickel concentrations for 240 hours. In order to determine the effects of temperature variation during nickel exposure it was imperative that the effects of a single temperature change be investigated before addressing more complex regimes. Single temperature changes of + 10°C or -10°C were imposed at rates of 2°C/h following exposures of between 24 hand 216 h. The effects of a single temperature change on mortality, and duration of toxicant exposure at high and low temperatures were evaluated. The effects of fluctuating temperatures during exposure were investigated through two regimes. The first set of bioassays imposed a sinewave diurnal cycle temperature (20.±.1DOC) throughout the 10 day exposure to 240-h LeSO Ni. The second set of investigations approximated cyprinid movement through the littoral zone by imposing directionally random temperature changes (±2°C at 2-h intervals)...

The impact of core temperature corrections on exercise-induced hypoxemia.

Shipp, Nicholas Jon
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
Relevância na Pesquisa
36.11%
The primary purpose of this doctoral dissertation was to investigate the effect of body temperature responses at physiologically relevant sites during an incremental exercise test on the phenomenon of exercise-induced hypoxemia (EIH). This phenomenon has been considered as an important limitation to physical performance with a prevalence of ~50 % in trained male athletes, but described in both sexes, across the range of both age and physical fitness in more recent literature. Previously this phenomenon has been described as a decrement in both arterial oxygen partial pressure (PaO₂) and oxy-haemoglobin saturation (SaO₂or SpO₂) with, particularly important for PaO₂, a lack of or inappropriate correction made for the change in body temperature during intense exercise. The initial study of this thesis determined the thermal response within the body at physiologically relevant sites measured simultaneously during an incremental exercise test. The results demonstrated the inadequacy of rectal temperature as an indicator of the acute temperature changes occurring during an incremental exercise test due to its slow response rate and relative thermal inertia. Radial arterial blood and oesophageal temperatures were shown to behave almost identically during the exercise test...

Temperature control instrumentation for scanning tunnelling microscopy

Visser, Jason Willem
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 8658393 bytes; application/pdf
EN; EN
Relevância na Pesquisa
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This thesis describes three different design projects that are intellectually connected by the fact that they all involve the development of apparatus to facilitate the precise control of sample temperature in modern microscopes. The first project is a low-temperature sample stage, for a beetle-type scanning tunnelling microscope. The design for this sample stage, and images taken on it with atomic resolution at 114 K are presented. This stage has the capability for variable-temperature sample cooling, which is also discussed. The second project is a set of low- and variable-temperature isothermal radiation shields for a new microscope that is currently being designed and assembled by our research group. These shields provide temperature control between 5 K and room temperature, with measured stability better than +/- 0.1 K. Controlled and stable temperature changes at rates up to 1.5 K per minute have been produced. The shields are modular and can easily accommodate future modifications. The design for the shields, along with their cooling and temperature control capabilities, is presented. The third project is a new stage design for heating, cleaning, and transferring metal and semiconductor samples. Also for use with the new microscope...

Réponse métabolique du saumon Atlantique (Salmo salar) aux fluctuations journalières de température : rôles de la température d’acclimatation et de l’historique thermique

Oligny-Hébert, Hélène
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.12%
En général, le métabolisme des poissons est estimé à des valeurs de température constantes, mais les effets de fluctuations journalières de température similaires à celles retrouvées en milieu naturel semblent peu connus. Les objectifs du présent mémoire sont de quantifier les effets de la température moyenne d’acclimatation et d’évaluer les effets de l’historique thermique des individus, sur les réponses métaboliques de tacons de saumon Atlantique (Salmo salar) aux fluctuations journalières de la température. Des tacons provenant de deux rivières, une fraîche et une chaude, ont été acclimatés à un maximum de quatre régimes thermiques (constant 15 °C ou 20 °C, fluctuant 15 °C ± 2.5 °C ou 20 °C ± 2.5 °C) et leur taux métabolique standard estimés par respirométrie par débit-intermittent. Les fluctuations journalières de température (15 °C ± 2.5 °C) près de l’optimum thermique pour cette espèce (16 °C) n’affectent pas le taux métabolique standard. À l’opposé, les fluctuations journalières de température plus chaudes (20 °C ± 2.5 °C) augmentent de 35.4% le taux métabolique standard des tacons de la rivière plus chaude, mais pas ceux des poissons de la rivière fraîche. Ainsi...

Effet de la température sur les interactions trophiques et intraguildes au sein d’un système plante-herbivore-ennemis naturels : modélisation et approches expérimentales

Sentis, Arnaud
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
Relevância na Pesquisa
36.12%
Il est maintenant reconnu que les changements climatiques ont des impacts importants sur l’ensemble des organismes vivants. Parmi les facteurs de ces changements, la température occupe une place prépondérante pour les organismes ectothermes car elle régule leur métabolisme. Toutefois, bien que les effets de la température sur les individus d’une espèce soient largement connus, les connaissances demeurent limitées quant aux conséquences sur les interactions trophiques. Dans ce contexte, notre étude s’intéresse aux effets de la température sur un système biologique composé d’une plante, le poivron Capsicum annuum L., d’un herbivore, le puceron Myzus persicae Sulzer (proie extraguilde), ainsi que de deux de ses ennemis naturels : la coccinelle maculée Coleomegilla maculata lengi Timberlake (prédateur intraguilde) et la cécidomyie prédatrice Aphidoletes aphidimyza Rondani (proie intraguilde). Dans ce but, nous avons opté pour une approche multiple comprenant : (1) la modélisation des interactions prédateur-proie et intraguilde (prédation entre deux compétiteurs d’espèces différentes qui exploitent une même ressource), (2) la réalisation d’expériences empiriques en laboratoire permettant de tester les prédictions des modèles et de caractériser l’effet de la température et de ses variations sur les composantes du système biologique étudié. Conformément aux prédictions d’un premier modèle...

Spectroscopie de luminescence à température et pression variables pour des complexes des lanthanides et de l'or

Intissar, Mourad
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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36.09%
Ce travail est axé vers la compréhension détaillée des propriétés de luminescence de composés de certains métaux lourds. La première partie de ce mémoire décrit la caractérisation spectroscopique d'un radical de type nitronyle nitroxyde, 2-(2-pyridinyl)-4,4,5,5-tétraméthyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxyde, abrégé (NIT2-Py), et de ses complexes avec les cations Tb(III), [Tb(hfac)3NIT2-Py], et Y(III), [Y(hfac)3NIT2-Py]. La variation de la température affecte les spectres de luminescence qui montrent de la structure vibronique résolue. Les maxima de ces transitions vibroniques se rapprochent au fur et à mesure que la température augmente. Ces variations des maxima en fonction de la température ne correspondent pas à des variations de fréquences vibrationnelles et sont de l'ordre de 200 cm-1 entre 80 K et 240 K. La variation de la température n'a pas d'influence significative sur la structure moléculaire, comme atteste la variation mineure des maxima des spectres Raman entre 80 K et 300 K. La comparaison des spectres expérimentaux à des spectres calculés montre que ces variations peuvent être reproduites par l'utilisation d'une combinaison de fréquences vibrationnelles. Le paramètre dont la variation est très significative est la résolution du spectre de luminescence...

The hot and the cold: unravelling the variable response of plant respiration to temperature

Atkin, Owen Kenneth; Bruhn, Dan; Hurry, Vaughan; Tjoelker, Mark G
Fonte: CSIRO Publishing Publicador: CSIRO Publishing
Tipo: Artigo de Revista Científica
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When predicting the effects of climate change, global carbon circulation models that include a positive feedback effect of climate warming on the carbon cycle often assume that (1) plant respiration increases exponentially with temperature (with a constant Q10) and (2) that there is no acclimation of respiration to long-term changes in temperature. In this review, we show that these two assumptions are incorrect. While Q10 does not respond systematically to elevated atmospheric CO2 concentrations, other factors such as temperature, light, and water availability all have the potential to influence the temperature sensitivity of respiratory CO2 efflux. Roots and leaves can also differ in their Q10 values, as can upper and lower canopy leaves. The consequences of such variable Q10 values need to be fully explored in carbon modelling. Here, we consider the extent of variability in the degree of thermal acclimation of respiration, and discuss in detail the biochemical mechanisms underpinning this variability; the response of respiration to long-term changes in temperature is highly dependent on the effect of temperature on plant development, and on interactive effects of temperature and other abiotic factors (e.g. irradiance, drought and nutrient availability). Rather than acclimating to the daily mean temperature...

Water temperature and riverine ecosystems: An overview of knowledge and approaches for assessing biotic responses, with special reference to South Africa

Dallas,Helen
Fonte: Water SA Publicador: Water SA
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2008 EN
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Available information pertaining to water temperature in riverine ecosystems is examined and consolidated into an overview that describes the spatial and temporal variation in water temperature, the importance of water temperature in lotic ecosystems, the measurement and modelling of water temperature, anthropogenic factors that modify water temperature, the effects of temperature changes on the physical and chemical characteristics of water; and on aquatic organisms and ecosystems. Methods for assessing the effects of temperature changes on aquatic organisms are discussed and current water temperature guidelines for the protection of aquatic ecosystems are outlined. This paper highlights the complexity of water temperature in the aquatic environment and the importance of understanding the spatio-temporal variability in water temperature and the variable responses of aquatic organisms to thermal stress. Anthropogenic modifiers of the thermal regime, which include heated discharges, flow modifications, riparian vegetation removal and global climate change; present ongoing threats to aquatic ecosystems. Whilst Northern Hemisphere information on water temperature is plentiful, this overview has identified the huge gap that exists in temperature-related data in South Africa. Without baseline data on water temperature and the thermal requirements of aquatic organisms...