Spelling suggestions: "subject:"tradeoffs"" "subject:"tradeoffs""
41 |
An Examination of Possible Maternal Effects due to Parasite and Density Stress on the Mealworm Beetle, Tenebrio molitorBennell, Maria C. 01 December 2011 (has links)
Few empirical studies examine the influence that the maternal parasite environment can have on offspring fitness (maternal effects) in invertebrates. Several recent studies have found that mothers can adjust offspring phenotype to counter the negative effects of parasite infection. In this thesis I subjected the parental generation of the host species, Tenebrio molitor (Insecta: Coleoptera), to a high parasite, high density, or control treatment. Offspring were subsequently subjected to either the same stress, the alternate stress, or to the control, and fitness-related life history traits were measured in both generations. The results from this thesis do not support the hypothesis that T. molitor mothers influence offspring fitness in a positive way. Instead, maternal effects led to a reduction in offspring fitness under both types of stress. At least under some environmental conditions, females invest in their fitness at the expense of their offspring.
|
42 |
Measuring and Navigating the Gap Between FPGAs and ASICsKuon, Ian 08 March 2011 (has links)
Field-programmable gate arrays (FPGAs) have enjoyed increasing use due to their low non-recurring engineering (NRE) costs and their straightforward implementation process. However, it is recognized that they have higher per unit costs, poorer performance and increased power consumption compared to custom alternatives, such as application specific integrated circuits (ASICs). This thesis investigates the extent of this gap and it examines the trade-offs that can be made to narrow it.
The gap between 90 nm FPGAs and ASICs was measured for many benchmark circuits. For circuits that only make use of general-purpose combinational logic and flipflops, the FPGA-based implementation requires 35 times more area on average than an equivalent ASIC. Modern FPGAs also contain "hard" specific-purpose circuits such as multipliers and memories and these blocks are found to narrow the average gap to 18 for our benchmarks or, potentially, as low as 4.7 when the hard blocks are heavily used. The FPGA was found to be on average between 3.4 and 4.6 times slower than an ASIC and this gap was not influenced significantly by hard memories and multipliers. The dynamic power consumption is approximately 14 times greater on average on the FPGA than on the ASIC but hard blocks showed promise for reducing this gap. This is one of the most comprehensive analyses of the gap performed to date.
The thesis then focuses on exploring the area and delay trade-offs possible through architecture, circuit structure and transistor sizing. These trade-offs can be used to selectively narrow the FPGA to ASIC gap but past explorations have been limited in their scope as transistor sizing was typically performed manually. To address this issue, an automated transistor sizing tool for FPGAs was developed. For a range of FPGA architectures, this tool can produce designs optimized for various design objectives and the quality of these designs is comparable to past manual designs.
With this tool, the trade-off possibilities of varying both architecture and transistor-sizing were explored and it was found that there is a wide range of useful trade-offs between area and delay. This range of 2.1 X in delay and 2.0 X in area is larger than was observed in past pure architecture studies. It was found that lookup table (LUT) size was the most useful architectural parameter for enabling these trade-offs.
|
43 |
Community assembly and food web interactions across pond permanence gradientsGreig, Hamish Stuart January 2008 (has links)
Ecological communities along gradients of environmental stress are thought to be structured by trade-offs between resisting biotic interactions in physically benign habitats and successfully exploiting physically stressful habitats. However, these trade-offs are likely to be affected by the predictability of abiotic stressors, and variation in the strength of biotic interactions. I investigated community assembly and food web interactions in ponds across an unpredictable gradient of water inundation (pond permanence) in Canterbury, New Zealand. Pond community composition and species richness were strongly influenced by pond permanence. However, species in temporary ponds were a nested subset of generalists that were also found in permanent ponds, rather than a unique assemblage of temporary pond specialists. Subsequent experiments indicated predator impact decreased with pond permanence, partially due to the foraging suppression of predatory invertebrates in permanent ponds by fish. Weak predation in permanent ponds combined with unpredictable drying regimes likely selected for generalist traits, and resulted in community assembly being driven by a gradient of drying stress rather than trade-offs between biotic interactions and drying. Furthermore, predator impact increased over time in temporary ponds. In predictable snow-melt ponds in the Colorado Rocky Mountains, seasonal windows of weak predation were exploited by vulnerable species, leading to increased diversity within habitats. However in unpredictable systems like Canterbury, temporal increases in predation risk that depend on drying history are likely to increase variability in the spatial arrangement of suitable habitats for particular species. This should further favour the evolution of generalist traits and reduce the importance of trade-offs between predation and drying in the assembly of communities. Considering the predictability of disturbance regimes and the spatial and temporal variation in biotic interactions will greatly enhance understanding and management of communities in heterogeneous landscapes.
|
44 |
Functional Traits Affecting Photosynthesis, Growth, and Mortality of Trees Inferred from a Field Study and Simulation ExperimentsJanuary 2017 (has links)
abstract: Functional traits research has improved our understanding of how plants respond to their environments, identifying key trade-offs among traits. These studies primarily rely on correlative methods to infer trade-offs and often overlook traits that are difficult to measure (e.g., root traits, tissue senescence rates), limiting their predictive ability under novel conditions. I aimed to address these limitations and develop a better understanding of the trait space occupied by trees by integrating data and process models, spanning leaves to whole-trees, via modern statistical and computational methods. My first research chapter (Chapter 2) simultaneously fits a photosynthesis model to measurements of fluorescence and photosynthetic response curves, improving estimates of mesophyll conductance (gm) and other photosynthetic traits. I assessed how gm varies across environmental gradients and relates to other photosynthetic traits for 4 woody species in Arizona. I found that gm was lower at high aridity sites, varied little within a site, and is an important trait for obtaining accurate estimates of photosynthesis and related traits under dry conditions. Chapter 3 evaluates the importance of functional traits for whole-tree performance by fitting an individual-based model of tree growth and mortality to millions of measurements of tree heights and diameters to assess the theoretical trait space (TTS) of “healthy” North American trees. The TTS contained complicated, multi-variate structure indicative of potential trade-offs leading to successful growth. In Chapter 4, I applied an environmental filter (light stress) to the TTS, leading to simulated stand-level mortality rates up to 50%. Tree-level mortality was explained by 6 of the 32 traits explored, with the most important being radiation-use efficiency. The multidimentional space comprising these 6 traits differed in volume and location between trees that survived and died, indicating that selective mortality alters the TTS. / Dissertation/Thesis / Doctoral Dissertation Biology 2017
|
45 |
Rela??o entre a biodiversidade de plantas e os servi?os do ecossistema na caatingaManh?es, Adriana Pellegrini 13 March 2015 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-05-31T00:33:23Z
No. of bitstreams: 1
AdrianaPellegriniManhaes_TESE.pdf: 3111265 bytes, checksum: d57769e61e98f4dddb1171bdf72cc466 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-06-02T23:30:21Z (GMT) No. of bitstreams: 1
AdrianaPellegriniManhaes_TESE.pdf: 3111265 bytes, checksum: d57769e61e98f4dddb1171bdf72cc466 (MD5) / Made available in DSpace on 2016-06-02T23:30:21Z (GMT). No. of bitstreams: 1
AdrianaPellegriniManhaes_TESE.pdf: 3111265 bytes, checksum: d57769e61e98f4dddb1171bdf72cc466 (MD5)
Previous issue date: 2015-03-13 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico (CNPq) / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Muito tem se discutido na literatura sobre o papel da biodiversidade no funcionamento e servi?os do ecossistema, que s?o benef?cios essenciais para o bem-estar humano, derivados de processos ecol?gicos. Muitos experimentos em escala local j? evidenciaram a import?ncia da biodiversidade de plantas sobre o funcionamento do ecossistema, mas pouco se conhece ainda de como esta rela??o se desenvolve em sistemas naturais antropizados. Assim, o objetivo do primeiro cap?tulo desta tese foi avaliar como a biodiversidade de plantas e cobertura vegetal media os efeitos do uso da terra sobre as propriedades do ecossistema. Evidenciou-se a import?ncia da diversidade (funcional e taxon?mica) de plantas nas propriedades do ecossistema, como biomassa, fertilidade do solo e reten??o de ?gua no solo, al?m do efeito negativo do uso da terra. J? em uma escala maior, o entendimento da rela??o espacial dos servi?os com a biodiversidade tem dado suporte ?s pesquisa na ?rea de conserva??o da natureza. O segundo cap?tulo objetivou analisar a associa??o espacial entre biodiversidade de plantas e servi?os e como est?o distribu?dos nas unidades de conserva??o do bioma Caatinga. Mostrou-se que as unidades de conserva??o n?o est?o incluindo importantes ?reas com alta biodiversidade de plantas e a maioria dos servi?os do ecossistema (total de nove). Complementarmente, o cap?tulo 3 objetivou selecionar ?reas priorit?rias para conserva??o utilizando biodiversidade de plantas e servi?os do ecossistema como alvos, assim como incluir custos socioecon?micos. Como resultado, a inclus?o dos custos modificou a distribui??o das ?reas priorit?rias, diminuindo a porcentagem protegida de principais servi?os por?m, com pouca influ?ncia na prote??o da biodiversidade. Concluindo, esta tese contribui para o entendimento da rela??o entre biodiversidade de plantas e servi?os do ecossistema no bioma Caatinga, e recomenda??es podem ser feitas para pr?ticas de manejo em uma escala local, assim como, aplica??es para conserva??o em uma escala importante para tomadores de decis?es.
|
46 |
Comunidades arbóreas em florestas de restinga: o papel das demandas conflitantes e dos inimigos naturais no nicho de regeneração / Tree communities in restinga forests: the role of trade-offs and natural enemies in the regeneration nicheDaniela Zanelato 27 August 2012 (has links)
A presente dissertação teve como objetivo investigar se padrões presentes nas comunidades arbóreas adultas podem ser gerados por diferenças em aspectos relacionados ao nicho de regeneração das espécies. Nosso modelo de estudo foram duas florestas de restinga localizadas na Ilha do Cardoso, litoral sul do estado de São Paulo. A floresta de restinga alta (RA) é uma formação geologicamente mais antiga e possui dossel mais fechado que a floresta de restinga baixa (RB). No Capítulo 1, investigamos se as inversões de abundância das árvores adultas entre RA e RB podem ser geradas devido ao desempenho diferenciado destas espécies ainda na fase de plântula, devido à atuação do filtro ambiental luminosidade. Hipotetizamos que as espécies apresentem pior desempenho no estágio de plântula na floresta em que são menos abundantes como adultos, devido a uma demanda conflitante entre crescimento e sobrevivência. Esperávamos também que a mortalidade por patógenos fosse a principal causa de mortalidade das plântulas na floresta mais sombreada. Realizamos um experimento manipulativo em campo com seis espécies arbóreas, no qual plântulas com um mês após a germinação foram transplantadas nas duas florestas e no viveiro. Acompanhamos o desempenho destas plântulas durante nove meses. Não houve diferenças no desempenho das espécies entre as duas florestas estudadas, exceto na sobrevivência de Clusia criuva (no sentido esperado) e de Tapirira guianensis (sentido oposto ao esperado). Diferente do esperado, a principal causa de mortalidade de todas as espécies foi a herbivoria severa e não foi observado um conflito entre crescimento e sobrevivência. No Capítulo 2 investigamos se as diferenças de tamanho de semente entre as espécies arbóreas zoocóricas podem gerar diferenças nos padrões da comunidade adulta e essas diferenças ocorrem devido à atuação do filtro ambiental da luminosidade ou apenas devido às diferenças de capacidade de dispersão das espécies. Acompanhamos a chuva de sementes das espécies zoocóricas arbóreas durante quatro anos nas duas florestas e verficamos que a capacidade de dispersão ativa está negativamente relacionada ao tamanho de sementes, como é previsto por ambas as hipóteses (filtro ambiental e capacidade dispersão). Além disso, a relação entre a produção média de sementes e o tamanho de sementes apresentou um padrão triangular, de modo que as espécies de sementes grandes apresentam sempre baixas produções. Comparamos os tamanhos médios de sementes e a amplitude de tamanhos de sementes dos indivíduos e espécies estabelecidos como adultos nas duas florestas (DAP>= 5cm). Verificamos que a RA apresenta tamanho médio de semente e amplitude de tamanhos de sementes maiores que a RB. Além disso, a composição florística da RB está aninhada na composição da RA. Assim, hipotetiamos que as diferenças na capacidade de dispersão das espécies, aliadas às diferenças de idade das florestas são responsáveis pela distribuição de tamanho de sementes dos adultos estabelecidos nas duas florestas. Por fim, no capítulo 3, realizamos uma revisão bibliográfica sobre o papel dos microorganismos do solo no nicho de regeneração das espécies arbóreas tropicais. Foram encontrados estudos que abordam apenas a atuação de fungos, seja em interações positivas (fungos micorrízicos) ou negativas (fungos patogênicos). Discutimos os principais fatores e características associadas à mortalidade por patógenos do solo, bem como relações levantadas pelos estudos pioneiros que não foram corroboradas ou testadas / The objective of the current research was to investigate if the existing patterns in the adult tree communities can be generated by differences in the aspect related to the regeneration niche of species. Our model of study were two restinga\'s forests located at the Cardoso Island, on the South coast of São Paulo state. The tall resting forest (TRF) is an older formation, geologically speaking, and it hás closer canopies than the short resting forest (SRF). In the first chapter, we investigated if the abundance inversions of adult trees existing between the TRF and the SRF could be generated due to the differentiated performances of these species at the stage of the seedling, due to the action of the environmental light filter. We assumed as a hypothesis that the species show a worst performance in the stage of seedling in the forest where they are less abundant as adult, due to a trade-off between growth and survival. We expected that the mortality by pathogens was the main cause for the mortality of plants in the more shaded forest. We achieved a manipulative experiment in field with six tree species, in which one-month-old seedlings after germination were transplanted in the two forests and in the nursery. We followed the performance of the species in the two studied forests for nine months. There were no differences in the performance of the two species, except the survival of the Clusia criuva (in the expected way) and of the Tapirira guianensis (opposite to the expected way).Different from what was expected, the main cause of the mortality of all the species was the severe herbivory, and it was not possible to observe a conflict between the growth and the survival of them. In the second chapter, we investigated if the differences in the size of the seeds among the zoochoric tree species can generate differences in the patterns of the adult community and if those differences occur due to an action of the environment lighting filter or only by the differences of the dispersion capacity of the species. We followed the seed rain of the zoochoric tree species for four years in both forests and we could check that the active dispersion capacity of them is negatively related to the size of the seeds, as it can be predicted by both the hypothesis (environmental filter and dispersion capacity). Besides, the relationship between the average production of seeds and the size of the seeds presented a triangular pattern, as species with big seeds always provide low productions. We compared the seeds average sizes and the range of the seeds sizes of the individual plants and of the adult species in both forests (DAP_> 5 cm. We could verify that the TRF presents average size of seeds and range of the seeds\'s sizes that were bigger than in SRF. Furthermore, the SRF floristic composition is nested in the TRF composition. Therefore, we assumed as a hypothesis that the differences in the dispersal capacity of species, plus the age differences of the forests, are responsible for the distribution of the seeds sizes of the adult plants present in both forests. Finally, in chapter 3, we made a literature review about the role of the soil microorganisms in the specific site of the regeneration of the tropical tree species. We found studies that focus only on the action of the fungi as far in positive interactions (mycorrhizal fungi) as in negative ones (pathogenic fungi). We discussed the main factors and the characteristics associated to the mortality caused by the soil pathogens, as well as the relationship proposed by the pioneer studies which were not confirmed nor tested
|
47 |
Trade-offs and Conflicts Between Quality AttributesHenningsson, Kennet January 2001 (has links)
It is next to impossible to let a day go by without coming into contact with a computer system in some way, either by direct usage, or making a telephone call that is directed by computer systems. Due to the importance of computer systems we are all concerned with their quality, directly or indirectly, a malfunctioning system will disturb our lives in more or less drastic ways. Each stakeholder promotes his qualities and priorities for the system, and this will eventually lead to conflict, depending on relations between qualities. There is no simple solution to the problem of relating and conflicting quality attributes. But by making an informed decision it is possible to soften the effects of the trade-offs and gain a higher level of total software quality. The way to make an informed decision is to have knowledge about the relations between quality attributes along with insights of the consequences of the decision. This report gives a short introduction to the problem, and surveys both the relations stated within academia, and industry. The intention is to explore the knowledge present within academia and collect and present the established relations found by researchers. Further this report presents a survey carried out at companies working in different areas with software engineering, to show which relations that are visible to industry and how they are handling the relations between quality attributes. This gathered knowledge intends to support the ambition towards higher quality in software engineering.
|
48 |
Land use, food production, and the future of tropical forest species in GhanaPhalan, Benjamin Timothy January 2010 (has links)
Agriculture is arguably the greatest threat to tropical forest species. Conservation scientists disagree over the relative importance of two opposing strategies for minimising this threat: enhancing on-farm biodiversity, through wildlife-friendly farming practices, or sparing land for nature by using high-yielding farming methods on the smallest possible area to reduce the need to convert natural habitats. Previous theoretical work shows that understanding the relationship between population density and yield for individual species is crucial for determining whether one of these strategies, or a mixed strategy, will maximise their populations for a given food production target. In this thesis, I aim to identify what land-use strategy will permit increases in food production with least impact on species in the forest zone of Ghana. Farm-fallow mosaic landscapes with shifting cultivation and native canopy trees produced only around 15% as much food energy per hectare as the highest-yielding oil palm plantations. In farm mosaics where perennial tree crops dominate, food production and profits were higher, but did not reach those of oil palm plantations. I surveyed birds and trees in forest, farm mosaic, and oil palm plantation, and combined these data with information on yields to assess the likely consequences of plausible future scenarios of land-use change. My results provide evidence of a strong trade-off between wildlife value and agricultural yield. Species richness was high in low-yielding farming systems, but there was considerable turnover between these systems and forests, with widespread generalists replacing narrowly endemic forest-dependent species. Species most dependent on forest as a natural habitat, those with smaller global ranges and those of conservation concern showed least tolerance of habitat modification. For virtually all species, including even widespread generalists, future land-use strategies based on land sparing are likely to support higher populations of most species and minimise their risk of extinction compared to land-use strategies based on wildlife-friendly farming. If food production is to increase in line with Ghana‘s population growth, a combination of efforts to improve forest protection and to increase yields on current farmed land is likely to achieve this at least cost to forest species. Efforts to better protect forests, which require further restrictions on human use, might be most effective if they can be closely linked to support for farmers to improve their yields. In the long term however, this strategy will only delay and not avert biodiversity loss, unless global society can limit its consumption.
|
49 |
Interactions between Spider Mites and Predators in Systems with Dispersal Opportunities / 分散可能な環境でのハダニと捕食者の攻防Otsuki, Hatsune 23 March 2020 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第22475号 / 農博第2379号 / 新制||農||1074(附属図書館) / 学位論文||R2||N5255(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 日本 典秀, 教授 田中 千尋, 准教授 刑部 正博 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM
|
50 |
Understanding Human Disturbance to Birds at the Intersection of Birding and Bird PhotographyBrennan G Radulski (9749159) 15 December 2020 (has links)
<div>Human disturbance to birds is a subject of concern for bird conservation. Bird recreationalists, such as birders and bird photographers, who actively seek out birds, are identified as a broad group of people that contribute to bird disturbance. There are few studies on birders’ and bird photographers’ perceptions and behaviors related to bird disturbance, and these studies have conflicting results. Furthermore, little research identifies why bird recreationalists engage in behavior that disturbs birds. Understanding perceptions and behavior related to bird disturbance and the context behind engaging in this behavior is important for creating comprehensive solutions for preventing disturbance to birds. The purpose of this thesis is to create a typology of bird recreationalists, based on whether they engage in birding or bird photography as primary activities; identify the socio-demographic characteristics among bird recreationalists that are connected to an increased likelihood to engage in behavior that disturbs birds; assess perceptions of blame for disturbance to birds; and identify how motivations, barriers, challenges and trade-offs are associated with following ethical birding and bird photography guidelines. </div><div><br></div><div>The thesis used an online survey and in-person interviews of birders and bird photographers in two Midwestern states in the U.S., Illinois and Indiana, to achieve these objectives. Three sub-groups of bird recreationalists were identified through the online survey: individuals who only engage in birding; individuals who primarily engage in birding and secondarily, bird photography; and individuals who primarily engage in bird photography and secondarily, birding. Our findings indicate that individuals who 1) are male, 2) only engage in birding, 3) maintain life lists, 4) have more birds on their life lists, 5) can identify more birds by sight, 6) have more years of experience or 7) have a higher level of achievement-oriented motivation are more likely to engage in potentially harmful behaviors to birds. Additionally, quantitative findings suggest that birders and bird photographers may not perceive themselves as main contributors to bird disturbance. </div><div><br></div><div>The qualitative portion of the research identifies multiple ethical birding and bird photography guidelines that recreationalists found challenging to follow that had both ecological (e.g., maintaining distance) and social (e.g., respectfully educating others) implications. Recreationalists identified listing, photographing and seeing birds as key motivations to breaking ethical guidelines. Barriers to following guidelines included apathy, ignorance and improper technology. Finally, recreationalists identified bad photography and missed experiences as major trade-offs associated with following ethical guidelines. he concepts explored in this thesis research provide important management implications for natural resource managers and stakeholders in bird conservation and suggest a further need for examining bird recreationalists’ decision-making around bird disturbance.</div>
|
Page generated in 0.0521 seconds