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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

ANALYSIS OF ANNUAL GROWTH PATTERNS OF MILLETTIA STUHLMANNII, IN MOZAMBIQUE

Remane, Ivan Abdul Dula 01 August 2013 (has links)
The tropical hardwood forests of Mozambique are among its most important natural resources. Long-term sustainable management of these resources will require proper forest management, which depends on understanding the growth rates and the life history of important commercial species as well as the impacts of natural forces (e.g., climate variability) and human management. This study analyzes radial growth rate dynamics and climate-growth relationships of Millettia stuhlmannii and examines its dendrochronological potential. This tree locally known as Panga-panga or Jambirre is one of the most important timber species in Mozambique. Ranked as a first class commercial timber in Mozambique, it is frequently harvested in an unsustainable way and sustainable management of the species is urgently needed for the continued utilization of this resource. Five different methods demonstrate that the semi-ring porous tree rings of M. stuhlmannii are annual: (1) Ring structure and anatomy; (2) Successful cross-dating within and between trees; (3) Ring counting in trees with known age (young trees collected from an experimental "plantation") (4) Cambial wounding and (5) Correlation between ring width and climate data. Through these methods, M. stuhlmannii trees showed distinct reaction to pinning, adding one annual ring after one year. Cross dating of annual ring width growth was successful within and among selected M. stuhlmannii trees, which indicates that this species forms annual rings and that growth responds to an external climate variability. M. stuhlmannii annual growth ring boundaries were characterized by alternating patterns of parenchyma and fibre vessels and marginal parenchyma. Precipitation during previous December (r= 0.30; p<0.05), current February (r=0.30; p<0.05) and the entire rainy season (NDJFM; r=0.43, p<0.01) over a long period (1900-1996) showed a significant influence on Panga-panga tree ring growth. Declining rainfall has caused a growth increment decrease since 1940. The results of this study show that the mean annual increment of M. stuhlmannii is 0.51 cm/year and it takes about 75 years for an average M. stuhlmannii tree to reach the minimum lawful cutting diameter of 40 cm DBH (diameter at breast height). Temporal differences in movement through increasing diameter classes are large among and within classes. The median time necessary for trees to grow into the next diameter class was not statistically significant (Kruskal-Wallis chi-squared = 9.568, p>0.001). The relationship between stem diameter and percentage of heartwood is significantly high (R2 = 0.9701, p < 0.0001) and results suggest that from 33cm diameters on, the HW% remain stable. Partial correlation coefficients show that significant effects on growth to minimum cutting diameter occur while stems move through the 20-30 cm DBH class. This indicates the specific sizes at which silviculture treatments have to be started in order to maximize the productivity of this species. Correlation analyses revealed that heartwood width (HW) is positively correlated with total stem diameter (TSD), cambial Age (Ac), number of rings in heartwood (HWR), heartwood area (HWA), Total stem diameter area (TSDA) and Mean annual increment (MAI). This study suggests that further studies to improve diameter growth rate models as well as volume increment models need to be carried out. Strong correlation with precipitation during the rainy season suggests that this species is potentially useful for future climate reconstruction studies in Mozambique.
22

Emissions and Climate Impacts of Aerosol Emissions from Cookstoves and Gasoline Direct Injection Vehicles

Saliba, Georges 01 February 2018 (has links)
Anthropogenic gas- and particle-phase emissions affect the climate by absorbing and scattering radiation, and have been linked to adverse health effects. Black carbon (BC), a by-product of incomplete combustion, is the most potent light-absorbing component of atmospheric aerosols, with a top-of-the atmosphere direct radiative forcing estimated to be only second to CO2. However, there is a large uncertainty associated with BC’s total direct and indirect radiative forcings due to uncertain source emissions and optical properties and complex interactions with clouds. In this dissertation we investigate the direct radiative impact of two of the most important sources of BC particles: biofuel combustion and vehicles. Together these sources contribute around 40% of the global atmospheric BC burden. Recently, both of these energy sources are undergoing rapid technology changes, and the climate impacts from the emissions of these newly adopted technologies remain uncertain. We also investigate the role of atmospheric processing on the optical properties and growth rates of particles. This dissertation first assesses the climate impacts of aerosol emissions of two rapidly emerging technologies: improved cookstoves and gasoline direct injection (GDI) vehicles. We performed extensive measurements of gas- and particle emissions and optical properties of emissions from both these sources. Our data suggests that improved rocket cookstoves have, on average, a factor of two lower particulate matter (PM) emissions compared to traditional cookstoves but only a 4% climate benefits associated with their emissions. In contrast, we estimated a 30% climate benefit from switching traditional cookstoves to gasifier ones. Of all the stoves tested, charcoal stoves had the lowest emissions and climate impacts. Our data suggests the widespread deployment of improved cookstoves to replace existing, inefficient, traditional cookstoves will likely result in health and climate co-benefits. Similarly, we estimated that the rapid adoption of GDI vehicles to replace existing port fuel injection (PFI) vehicles will likely result in reduced warming from emissions. This is due to the higher fuel economy of GDI engines; we measured an average CO2 reduction of 57 g/mi, from switching engine technologies. GDI engine emissions had higher PM emissions compared to PFI engines, similar to previous findings. In addition, our data suggests that newer GDI engines have a factor of two lower PM emissions compared to older GDI engines. These improvements in emissions may enable GDI-equipped vehicles to meet the new Federal Tier 3 PM standard of 3.0 mg/mi without gasoline particulate filters (GPF, which would reduce their fuel economy). To better constrain the large uncertainty of radiative forcing associated with cookstove emissions, this dissertation examines emissions and optical properties from several cookstove and fuel combinations. We performed extensive laboratory measurements of the optical properties of fresh cookstove emissions using the newly developed firepower sweep protocol. Current model treatments of the optical properties of cookstove emissions assume: (1) complete internal mixture between BC and non-BC material and (2) absorption properties of organics based on parametrizations developed for biomass burning emissions. These assumptions do not accurately represent optical properties of fresh cookstove emissions. We developed new parametrizations of optical properties (BC-mass absorption cross section (MACBC), absorption angstrom exponent (AAE), and single scattering albedo (SSA)) of aerosol emissions from cookstoves as a function of the BC-to-PM mass ratio. These parametrizations are designed for use in climate models to more rigorously assess the global climate implications from adoption of improved stove technologies. Upon entering the atmosphere aerosol emissions undergo complex chemical transformations. Aerosol optical properties depend on their atmospheric processing which controls the amount of coating the particles accumulate and their lifetime. To assess the effects of coating on the optical properties, we performed targeted experiments using real world, size selected, BC particles emitted from a rocket improved cookstove, and coated with biogenic secondary organic aerosol (SOA) material. These experiments explicitly target to evaluate measurements and modeling using simple formulation like Mie theory. Measurements of MACBC and the mass scattering cross section (MSC) of coated BC particles were in good agreement with Mie predictions when the organic-to-BC mass ratio>5. Scattering (but not absorption) was sensitive to BC fractal-like morphology; Mie theory under-predicted measured scattering of fresh emissions. Our data suggest that Mie theory can be used in climate models to approximate the optical properties of coated BC particles emitted from cookstoves, if the mixing-state of BC particles is known. In this dissertation, we present initial evidence that particle growth rates depend on seed composition and gas-phase supersaturation. Current models do not account for seed-dependent growth rates. We conducted experiments to investigate the growth of diesel and biogenic SOA particles. Both seeds were exposed to the same gas-phase supersaturation, which allows us to accurately retrieve differences in growth rates and decouple the effects of surface activity and accommodation coefficients. We estimated that the accommodation coefficients of condensing material was 10% to 30% lower on the diesel particles compared to the SOA particles. Moreover, we measured larger surface activity of condensing material on the diesel particles, potentially due to less-miscible condensing vapors in the diesel particles compared to the SOA particles. Our data suggest that growth of BC (diesel) particles in the atmosphere is likely slower compared to SOA particles. Accurately representing these processes is important to estimate the lifetime and absorption enhancement from coated BC particles, as they compete with other particles for condensable vapors.
23

Methylglyoxal Effects on Cell Division of Scenedesmus quadricauda (Scenedesmaceae)

Rhie, Kitae 08 1900 (has links)
Cell division of ggeneflesmus quadricauda (Turp.) Breb. (Scenedesmaceae) is enhanced by methylglyoxal, a general inhibitor of cell division, at threshold concentration in conjunction with treatment timing related to growth stage of batch cultures. At 0.5 mM methylglyoxal concentration, cell division was significantly enhanced in algae treated in the logarithmic phase. Specific growth rates of methylglyoxal-treated cultures were rapidly increased at the beginning of logarithmic phase. Cultures inoculated with high cell numbers were less sensitive, but still showed high specific growth rates in logarithmic phase. Cell division in cultures which had low cell numbers was inhibited by 0.5 mM methylglyoxal treatment. Both specific activity of Glyoxalase I and the ratio of Glyoxalase I to Glyoxalase II of methylgloxal-treated cultures were higher than those of controls (1.3 and 2.1- fold, respectively). Pyruvate concentration in treated cultures was increased after methylglyoxal treatment.
24

Dynamics of heterotrophic bacterioplankton in costal ecosystems of the central Red Sea

Silva, Luis 03 1900 (has links)
Heterotrophic bacterioplankton dynamics have seldom been assessed in the Red Sea, an exceptionally warm oligotrophic basin, which could be used as a model for the future ocean. To understand the function of heterotrophic bacteria in biogeochemical cycles and the flows of matter and energy to higher trophic levels, it is peremptory to understand how bacterial growth is controlled. Bottom-up (resources availability), top-down (mortality by predators and viruses) and temperature are the main hypotheses of control of bacterial activity and stocks. This dissertation aims to assess the spatial-temporal variability of heterotrophic bacteria and their interactions with diverse sources of dissolved organic matter (DOM) through the observed effects on bacterial growth rates and productivity in coastal environments of the central Red Sea. To that end we conducted a total of 66 shortterm incubations (4-6 days) concurrently with the whole microbial community and predator-free (by filtration) in various shallow ecosystems characterized by different dominant sources of DOM. Frequent sampling combined flow cytometry and biogeochemical analysis allowed us to measure bacterial standing stocks, including the carrying capacity (maximum abundances), growth rates, characterize DOM concentrations and lability, assess bacterial DOM consumption rates and biomass production and ultimately quantify bacterial growth efficiencies. Our findings suggest that although bacteria seemed to thrive in nutrient-sufficient waters, the central coastal Red Sea is characterized by unusually low bacterial standing stocks (4.05 ± 0.31 x105 cells ml-1), probably controlled by protistan grazing. At the same time, bacterioplankton showed high potential to grow (0.35-1.75 d-1, reaching 4.16 d-1 when dilution and pre-filtration were performed). Even though the highest specific growth rates were observed during the warmer periods, we did not find any consistent relationship with temperature. While temperature seemed not to constrain bacterial specific growth rates, we observed a tight link between bacterial growth and resource availability in terms of both quantity and quality. Overall, by surveying one of the warmest marine regions on Earth, this dissertation provides detailed insights into heterotrophic bacterioplankton dynamics and how bottomup, top-down and temperature regulate them in tropical waters, a vast geographical extension of the world oceans that had remained strongly undersampled to date.
25

Pattern Avoidance in Ordered Set Partitions

Godbole, Anant, Goyt, Adam, Herdan, Jennifer, Pudwell, Lara 01 January 2014 (has links)
In this paper we consider the enumeration of ordered set partitions avoiding a permutation pattern of length 2 or 3. We provide an exact enumeration for avoiding the permutation 12. We also give exact enumeration for ordered partitions with 3 blocks and ordered partitions with n-1 blocks avoiding a permutation of length 3. We use enumeration schemes to recursively enumerate 123-avoiding ordered partitions with any block sizes. Finally, we give some asymptotic results for the growth rates of the number of ordered set partitions avoiding a single pattern; including a Stanley-Wilf type result that exhibits existence of such growth rates.
26

A study of growth rates in seedlings of Douglas fir ecotypes

Papenfuss, Herbert D. 28 May 1964 (has links)
The purpose of this study was to find out if ecological races with different growth rates existed in douglas fir. Seeds were collected from six areas by the Forest Service and the author. A study was made of stem and tap root growth utilizing three photoperiods of varying length. Rate of tap root growth was significant for ecotype suggesting selection for tap root length in the plants from utah and Arizona. Each geographical area represents a growth rate ecotype with a wide break in the data on stem growth.
27

Spatial Impacts of Growth Centres

Fotheringham, Alexander Stewart 08 1900 (has links)
<p> The paper indicates, by a review of the early growth centre literature and the later spatial analysis literature, how little is known, particularly in quantitative terms, about the spatial impacts of growth centres. A regression model is then presented by which several aspects of the spatial impacts of growth centres in Ontario are investigated. Generally, it was found that growth was polarised around a set of designated growth centres and this growth diffused away from the growth centres quite gradually. The exceptions were for large centres, growing slowly, where growth rates increased sharply as distance to growth centres increased and for small centres , growing rapidly, where growth rates decreased rapidly with distance from growth centres. </p> <p> From the regression model, a further model was derived which was used to investigate the extent of spread effects from growth centres in Ontario. The approximate mean maximum distance of the diffusion of spread effects from growth centres was found to be 163 miles. This could have important implications for the spacing of growth centres and government policies relating to growth centres. </p> <p> The analysis also investigates the relationship between growth rates and population size and this was found to be non-linear. Generally, for small centres, population. size and growth rates were negatively related: for intermediate-sized centres the relationship was positive; and for large centres the relationship was again negative. </p> / Thesis / Master of Arts (MA)
28

The Regional Distribution Pattern of Economic Activity in Canada: A Linear Programming Exercise

Aziz, Rashid January 1980 (has links)
Resource allocation across regions in an economy has been analysed by many authors, both from the efficiency and equity viewpoints. In general, these aspects are assumed to be conflicting - the attainment of higher growth rates and income levels in accordance with efficient resource allocation normally discrimminates against the relatively less well off sections of society. The literature concentrates largely on the allocation of resources across sectors, irrespective of geographic considerations, so that the decision to invest in a region seldom incorporates the area's absorptive capacity. The regional imbalance that results is shown just as clearly by the lack of high technology industry in some areas as it is by the (potential) congestion and overcrowding that characterises other regions. This study focuses on the relationship between the regional allocation of income generating activities and the total income generated for the nation. The growth potential of any area is defined by the availability of all essential facilities - service and repair facilities, transport and energy supplies being only a part of the picture. Factor supplies and the supply of credit, alongwith the high degree of interaction between regions and sectors also complement the picture. The low income potential of the peripheral areas of any nation is the result of a lack of these ancilliary facilities. However, once these bottlenecks are removed, the outlying areas normally depict higher growth rates than the core regions. In this study, a linear programming model is developed 1 in king the commodity, factor and asset markets of a nation, both across sectors and across regions. Thus, the commodity market of any region is related to the commodity, asset and factor markets of all regions. National absorptive capacity is now defined in terms of the potentials of all areas of the nation. The application of this model to Canada results in a set of optimal regional patterns of economic activity. Growth in any area is now encouraged only if the regional economy is not operating close to some capacity limitation, and if a full complement of goods and services, factors and assets is available. The results obtained justify these expectations because the model depicts a pattern of resource allocation that stresses areas where all facilities for growth are present. Thus, further investment in the traditional center Quebec and Ontario - is restricted, some critical thresholds regarding absorptive capacity having been hit. However, the regions where a full complement of services and asset supplies is not available - the Atlantic provinces - are not the alternatives. The relative ordering favours the modern manufacturing and service sec tors in Alberta and British Columbia. The model does suggest the existence of a tradeoff between national income and regional balance, since the imposition of regional balance constraints reduces the value of national consumption. However, even when regional equity constraints are imposed, the model suggests that more national income can be generated through reallocation of economic activity than was generated by the historical pattern of allocation. / Thesis / Doctor of Philosophy (PhD)
29

Some properties of a class of stochastic heat equations

Omaba, McSylvester E. January 2014 (has links)
We study stochastic heat equations of the forms $[\partial_t u-\sL u]\d t\d x=\lambda\int_\R\sigma(u,h)\tilde{N}(\d t,\d x,\d h),$ and $[\partial_t u-\sL u]\d t\d x=\lambda\int_{\R^d}\sigma(u,h)N(\d t,\d x,\d h)$. Here, $u(0,x)=u_0(x)$ is a non-random initial function, $N$ a Poisson random measure with its intensity $\d t\d x\nu(\d h)$ and $\nu(\d h)$ a L\'vy measure; $\tilde$ is the compensated Poisson random measure and $\sL$ a generator of a L\'{e}vy process. The function $\sigma:\R\rightarrow\R$ is Lipschitz continuous and $\lambda>0$ the noise level. The above discontinuous noise driven equations are not always easy to handle. They are discontinuous analogues of the equation introduced in \cite{Foondun} and also more general than those considered in \cite{Saint}. We do not only compare the growth moments of the two equations with each other but also compare them with growth moments of the class of equations studied in \cite{Foondun}. Some of our results are significant generalisations of those given in \cite{Saint} while the rest are completely new. Second and first growth moments properties and estimates were obtained under some linear growth conditions on $\sigma$. We also consider $\sL:=-(-\Delta)^{\alpha/2}$, the generator of $\alpha$-stable processes and use some explicit bounds on its corresponding fractional heat kernel to obtain more precise results. We also show that when the solutions satisfy some non-linear growth conditions on $\sigma$, the solutions cease to exist for both compensated and non-compensated noise terms for different conditions on the initial function $u_0(x)$. We consider also fractional heat equations of the form $ \partial_t u(t,x)=-(-\Delta)^{\alpha/2}u(t,x)+\lambda\sigma(u(t,x)\dot{F}(t,x),\,\, \text{for}\,\, x\in\R^d,\,t>0,\,\alpha\in(1,2),$ where $\dot{F}$ denotes the Gaussian coloured noise. Under suitable assumptions, we show that the second moment $\E|u(t,x)|^2$ of the solution grows exponentially with time. In particular we give an affirmative answer to the open problem posed in \cite{Conus3}: given $u_0$ a positive function on a set of positive measure, does $\sup_{x\in\R^d}\E|u(t,x)|^2$ grow exponentially with time? Consequently we give the precise growth rate with respect to the parameter $\lambda$.
30

Efeitos de diferentes taxas de crescimento na recria sobre o desempenho, idade a puberdade e produção leiteira em fêmeas da raça Santa Inês / Effects of growing rates in prepubertal period on performance, age at puberty and milk yield of Santa Ines sheep

Silva, Marlon Richard Hilário da 30 November 2009 (has links)
Experimento I: Foram utilizadas 60 borregas da raça Santa Inês com o objetivo de avaliar os efeitos de três taxas de crescimento até os 7 meses de idade. Os tratamentos foram delineados visando obter alta taxa de crescimento (ATC), moderada taxa de crescimento (MTC) e baixa taxa de crescimento (BTC). Foram avaliados o consumo de matéria seca, o ganho de peso corporal e as concentrações séricas de progesterona para a detecção da idade à puberdade. Foram verificados efeitos lineares (p<0,01) para o peso corporal e metabólico, sendo os maiores valores encontrados para os animais do tratamento ATC. Efeito linear (p<0,01) foi verificado para o ganho médio diário (GMD) sendo de 0,182; 0,156 e 0,136 kg/dia para os tratamentos ATC, MTC e BTC respectivamente. Borregas pertencentes ao tratamento ATC apresentaram maior conversão alimentar sendo os valores para o tratamento ATC de 6,1; MTC de 7,1 e BTC de 9,2 kg MS/ kg de ganho de peso. Verificou-se diferença (p<0,01) quanto a porcentagem de animais que atingiram a puberdade sendo o tratamento MTC com o maior número de borregas púberes até os 7 meses de idade (60%), seguida dos tratamentos ATC (45%) e BTC (15%)com peso médio de 39,3 kg de peso corporal, sendo 70% do peso adulto. Experimento II: As borregas utilizadas no experimento 1 com 37 Kg de PC entraram em estação de monta e após o parto receberam uma única dieta, sendo blocadas de acordo com o peso e dias de lactação. Observou-se efeito quadrático (p<0,01) na produção de leite em 3h (137,9; 150,1 e 104,4 g), efeito quadrático (p<0,05) para LCG (167,2; 178,9 e 129,4) e efeito quadrático (p<0,03) LCGP (216,5; 140,5 e 162,7). Os teores de gordura (9,8; 8,9 e 8,3%) e de proteína (4,2; 4,2 e 4,6 apresentaram efeitos lineares sendo (p=0,01) para gordura e (p<0,01) para proteína. Experimento III: Os objetivos deste experimento foram avaliar o efeito da inclusão de bagaço de cana-de-açúcar in natura (BIN) sobre o consumo e a digestibilidade aparente dos nutrientes, balanço de nitrogênio e os parâmetros ruminais de cordeiros Santa Inês. Quatro cordeiros providos de cânula ruminal com peso corporal (PC) médio inicial de 30kg foram alojados individualmente em gaiolas para ensaios de metabolismo. O tratamento controle positivo (CONT) consistia de uma ração de alto concentrado contendo de 10% de feno de coastcross (Cynodon sp.) na MS, sendo os demais tratamentos níveis crescentes de BIN em 10, 20 e 30% da MS, constituindo os tratamentos 10BC, 20BC e 30BC. As rações experimentais foram isonitrogenadas (13,75±0,25% PB). Não verificou-se efeito de tratamento (p>0,05) sobre o consumo de MS, MO, e PB em kg/dia e g/kg de PC 0,75; apenas sobre consumo de FDN com efeito linear (p< 0,01). O balanço de nitrogênio, assim como a concentração de acetato, propionato, butirato, concentração total de AGCC, amônia no fluido ruminal e a de digestibilidade aparente da MS, MO, PB e FDN não foram afetados pelos tratamentos. / Trial I: Sixty Santa Ines ewe lambs were used to evaluate the effects of three growing rates until 7 months of age. Treatments were defined to achieve high (HGR), moderate (MGR) and low (LGR) growing rates. The dry matter intake and average daily gain (ADG) were evaluated, well as serum levels of progesterone in order to detect the age of puberty. Linear effects (P<0.01) to body weight (BW) with values being 59.5, 61.4, and 58.0 to HGR, MGR and LGR, respectively. Linear effects (P<0.01) was also observed for average daily gain with values being 0.182, 0.156, and 0.136 kg/day, for HGR, MGR and LGR, respectively. The feed:gain ratio showed a linear effects (p<0.02) according to raw sugarcane bagasse inclusion in diet with values being 6.1, 7.1 (M) and 9.2 kgDM/kg BW for HGR, MGR and LGR, respectively. Linear effects (p<0.01) was observed for the percentage of animals of ewe lambs the reached puberty at 7 months of age, showing highest values for MGR (60%), followed by HGR (45%) and LGR (15%) treatment. Trial II: The same ewe lambs of Experiment 1 were bred at 37 kg of BW and after lambing they received a unique diet. The ewe lambs were blocked according to body weight and days in milking. According to the energy density increase in the diet, quadratic effects (p<0.01) was observed on milk production recorded in a 3-hour interval (137.9; 150.1 and 104.4 g), fat corrected milk (167.2, 178.9 and 129.4 g) and fat and protein corrected milk (216.5, 140.5, 162.7g). Fat (9.77, 8.92 and 8.35%) and protein (4.2, 4.2, and 4.6%) showed linear effects (P=0.01) for fat and (P<0.01) for protein. Trial III: The aim of this study was to evaluate the inclusion of raw sugarcane bagasse (RSB) on dry matter intake and apparent digestibility of nutrients, nitrogen balance and ruminal parameters of Santa Ines ram lambs. Four ruminally fistulated ram lambs averaging 30 kg of BW were placed in metabolism crates. The control treatment (CONT) consisted of a high concentrate diet with 10% of coastcross (Cynodon sp.) hay in the dietary DM and the others treatments consisted of 10, 20 and, 30% of RBS in the dietary DM. The diets were formulated to provide similar concentration of crude protein (13.75±0.25%). No effects were observed for DMI, OM, and CP in kg/day and g/kg of BW0.75. Linear effects (p<0.02) was observed for NDF intake according RBS inclusion. Variables, as well as total SCFA, acetate, propionate, and butyrate concentrations. Ruminal ammonia and apparent nutrient digestibility also did not differ among treatments.

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