751 resultados para lytic activity and cooperativity


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The current study describes the composition and activity of the snake community of the Pa-hay-okee wetlands of Everglades National Park. The study was conducted from January 1987 to January 1989. Sixteen species were observed, with Thamnophis sauritus, Thamnophis sirtalis, Nerodia fasciata pictiventris, and Agkistrodon piscivorus representing 90.2% of the total sample. The seasonal distribution and activity of the snakes were closely related to fluctuations in the water table. Most activity occurred in the winter months as snakes migrated west following the drying water edge of Shark River Slough. Seventy percent of all snakes observed during this study were either injured or dead on the road. Over 50% of annual mortality occurred during migration. The impact that road mortality is having on the local snake community cannot be ignored. Management options are provided to minimize loss. A comparison is made to the snake community of the Long Pine Key Region of Everglades National Park.

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Present theories of deep-sea community organization recognize the importance of small-scale biological disturbances, originated partly from the activities of epibenthic megafaunal organisms, in maintaining high benthic biodiversity in the deep sea. However, due to technical difficulties, in situ experimental studies to test hypotheses in the deep sea are lacking. The objective of the present study was to evaluate the potential of cages as tools for studying the importance of epibenthic megafauna for deep-sea benthic communities. Using the deep-diving Remotely Operated Vehicle (ROV) "VICTOR 6000", six experimental cages were deployed at the sea floor at 2500 m water depth and sampled after 2 years (2y) and 4 years (4y) for a variety of sediment parameters in order to test for caging artefacts. Photo and video footage from both experiments showed that the cages were efficient at excluding the targeted fauna. The cage also proved to be appropriate to deep-sea studies considering the fact that there was no fouling on the cages and no evidence of any organism establishing residence on or adjacent to it. Environmental changes inside the cages were dependent on the experimental period analysed. In the 4y experiment, chlorophyll a concentrations were higher in the uppermost centimeter of sediment inside cages whereas in the 2y experiment, it did not differ between inside and outside. Although the cages caused some changes to the sedimentary regime, they are relatively minor compared to similar studies in shallow water. The only parameter that was significantly higher under cages at both experiments was the concentration of phaeopigments. Since the epibenthic megafauna at our study site can potentially affect phytodetritus distribution and availability at the seafloor (e.g. via consumption, disaggregation and burial), we suggest that their exclusion was, at least in part, responsible for the increases in pigment concentrations. Cages might be suitable tools to study the long-term effects of disturbances caused by megafaunal organisms on the diversity and community structure of smaller-sized organisms in the deep sea, although further work employing partial cage controls, greater replication, and evaluating faunal components will be essential to unequivocally establish their utility.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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We present an innovation value chain analysis for a representative sample of new technology based firms (NTBFs) in the UK. This involves determining which factors lead to the usage of different knowledge sources and the relationships that exist between those sources of knowledge; the effect that each knowledge source has on innovative activity; and how innovation outputs affect the performance of NTBFs. We find that internal (i.e. R&D) and external knowledge sources are complementary for NTBFs, and that supply chain linkages have both a direct and indirect effect on innovation. NTBFs' skill resources matter throughout the innovation value chain, being positively associated with external knowledge linkages and innovation success, and also having a direct effect on growth independent of the effect on innovation. ©2010 IEEE.

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We present an innovation value chain analysis for a representative sample of new technology based firms (NTBFs) in the UK. This involves determining which factors lead to the usage of different knowledge sources and the relationships that exist between those sources of knowledge; the effect that each knowledge source has on innovative activity; and how innovation outputs affect the performance of NTBFs. We find that internal (i.e. R&D) and external knowledge sources are complementary for NTBFs, and that supply chain linkages have both a direct and indirect effect on innovation. NTBFs' skill resources matter throughout the innovation value chain, being positively associated with external knowledge linkages and innovation success, and also having a direct effect on growth independent of the effect on innovation. ©2010 IEEE.

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Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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The developmental histories of 32 players in the Australian Football League (AFL), independently classified as either expert or less skilled in their perceptual and decision- making skills, were collected through a structured interview process and their year-on-year involvement in structured and deliberate play activities retrospectively determined. Despite being drawn from the same elite level of competition, the expert decision-makers differed from the less skilled in having accrued, during their developing years, more hours of experience in structured activities of all types, in structured activities in invasion-type sports, in invasion-type deliberate play, and in invasion activities from sports other than Australian football. Accumulated hours invested in invasion-type activities differentiated between the groups, suggesting that it is the amount of invasion-type activity that is experienced and not necessarily intent (skill development or fun) or specificity that facilitates the development of perceptual and decision-making expertise in this team sport.

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Background: Adolescence is a period of life associated with self-perceptions of negative body image. Physical activity levels are low and screen time levels are also high during this stage. These perceptions and behaviours are associated with poor health outcomes, making research on their determinants important. With adolescent populations, certain groups may be at higher risk of body dissatisfaction than others, and body dissatisfaction may influence individual physical activity and screen time levels. Objectives: The objectives of this thesis were to: 1) describe body image among young Canadians, examining possible health inequalities 2) estimate the strength and significance of associations between body satisfaction, physical activity and screen time, and 3) examine the potential etiological role of biological sex. Methods: Objective 1: The 2013/2014 Health Behaviour in School-aged Children study was employed. Sex-stratified Rao-Scott chi-square analyses were conducted to examine associations between socio-demographic factors and body satisfaction. Objective 2: The 2005/2006 and 2013/2014 cross-sectional and 2006 longitudinal HBSC data sets were used. Sex-stratified modified Poisson regressions were conducted and risk estimates and associated confidence intervals obtained. Results: Objective 1: Among males, being older, of East and Southeast Asian ethnicity, and reporting low SES all were associated with body dissatisfaction. Among females, being older, of Arab and West Asian or African ethnicity, being born in Canada, and reporting low SES were all associated with being body dissatisfied. Objective 2: Cross-sectionally, males who reported ‘too fat’ body dissatisfaction were more likely to be physically inactive. Adolescents of both sexes who reported ‘too fat’ body dissatisfaction were more likely to engage in high levels of screen time. Data from the longitudinal component supported the idea that male ‘too fat’ body dissatisfaction temporally leads to physical inactivity, but showed an inverse relationship between body dissatisfaction and screen time. Conclusions: Objective 1: Future prevention efforts in Canada should target subgroups to effectively help those at greatest risk of body dissatisfaction, and ameliorate potential inequalities at the population level. Objective 2: The presence of these relationships may inform future interventions as part of a multi-factorial etiology, in order to increase physical activity and decrease screen time among youth.

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Airports have become increasingly active in route development as a means of attracting, growing and retaining air services. However, little is known about the different levels of route development activity at airports, or the extent to which route development activity affects performance. Based on the findings of a survey of 124 airports worldwide, this study finds that larger airports are significantly more active than smaller airports. It also finds that private airports are more active than public airports, and that airports in Europe are more active than airports in other world regions, although differences according to ownership and location are not significant. Route development activity has a significant positive effect on performance. Factors associated with the airport business environment (market turbulence, competitive intensity, market growth and airport constraints) were not found to have a significant moderating effect on the relationship between route development activity and performance. However, two factors were found to have a significant direct effect on performance; market growth has a significant positive effect while airport constraints have a significant negative effect.