Dissertations / Theses on the topic 'Environmental conditions'
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Robertson, Marta. "Epigenetic Response to Challenging Environmental Conditions." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6939.
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The discovery of epigenetic mechanisms has ignited speculation into their role in ecological and evolutionary processes. In particular, the contribution of epigenetic variation to adaptation or phenotypic plasticity that is distinct from genetic variation would be an important addition to existing evolutionary mechanisms. Although the research of epigenetic mechanisms from an ecological and evolutionary (or eco-evolutionary) perspective has been growing, it is still unclear how epigenetic variation might function in natural populations and settings and to what extent it might serve to mediate population response to changing environmental conditions over time. Over the course of my dissertation, I explored the importance of DNA methylation in population response to a variety of environmental conditions.
In the first chapter of my dissertation, I reviewed existing literature on the relationship between DNA methylation and environmental response. I argued that given the weight of current evidence, DNA methylation, in addition to other epigenetic mechanisms, needs to be included the evolutionary synthesis. Additionally, I identified a number of outstanding questions and outlined research directions that would help elucidate the role of epigenetic mechanisms in evolution.
In my second chapter, I studied the genetic and epigenetic composition of populations of Spartina alterniflora that were impacted by the Deepwater Horizon oil spill in 2010. Current evolutionary theory predicts that following a severe environmental stressor, populations may experience a bottleneck effect, in which one or only a few genotypes survive to reproduce in subsequent generations. However, it is unclear whether these patterns are reflected in epigenetic variation as well, because novel environmental perturbations may serve to induce epigenetic variation rather than diminish it. We found a significant genetic signature of oil exposure in exposed populations, but did not see a similar effect in the epigenetic composition of exposed populations. These data suggest that epigenetic modifications, such as DNA methylation, may not always increase in number during stressful episodes, but may instead follow genetic variation. These results provide valuable information for the development of nascent population epigenetic theory, and may help parameterize expectations about conditions that provoke epigenetic variation, particularly when genetic variation may be limited.
In addition to strong, unpredictable stressors, populations also respond via phenotypic changes over time through developmental stages and life histories that coincide with seasonal, regular environmental cues. Epigenetic mechanisms influence these regulatory and developmental changes that occur within an individual over time. In my third chapter, I examined the epigenetic response to seasonality in multiple coastal plant species. We found a weak signature of single methylation polymorphisms that was associated with seasonal environmental change within the studied species, as well as global patterns of methylation that were consistent across species. The results of this study indicate the possibility of conservation of methylation patterns across phylogenetic histories.
In my fourth chapter, I explored in detail how the ability to maintain methylation might affect stress response. We compared individuals of the model plant Arabidopsis thaliana that were deficient in maintenance methylation machinery to control genotypes under both abiotic and biotic stresses, and then studied the growth of their offspring in the absence of stress. We found inherited phenotypic signatures of parental stress in the offspring generation and interactive effects of parental stress and genotype. This study not only reinforces the correlations that we observed in our field studies, but adds to the growing body of literature highlighting the importance of DNA methylation both in immediate environmental response and as a mechanism for heritability.
Overall, this dissertation demonstrates that DNA methylation is highly abundant in natural populations and may be part of the response to various stressors at a number of time scales. The integration of DNA methylation in the evolutionary synthesis will aid in the explanation of phenomena such as phenotypic plasticity or adaptation, and will be an important contribution to the existing body of evolutionary mechanisms.
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Carmichael, Hannah. "Environmental conditions favouring ice pellet aggregation." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18788.
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Winter precipitation is an important issue in Canada because of its common occurrence and associated destructive consequences. Prediction of the precipitation type when temperatures are near 0°C is often difficult because so many types can occur. This study examines the microphysics of ice pellet formation, in particular the ability of these to form aggregates and the consequences of these aggregates. This issue was examined by modelling the freezing of a distribution of precipitation particles as they fall through the atmosphere and interact through collisions. Three mechanisms for aggregation were examined, collisions among the particles involved in these mechanisms were modelled and the relative importance of each mechanism was determined. It is shown that, for the conditions considered, aggregates are often able to collect freezing rain drops and that aggregation can sometimes be very effective at eliminating freezing rain but the conditions need to be precise for this to occur.Les divers types de précipitations observées durant les tempêtes hivernales sont souvent la cause d'inconvénients durant cette période au Canada. Il est difficile de prédire ces divers types de précipitations du fait de leur sensibilité à certaines conditions atmosphériques, en particulier à des températures près de 0°C. Cette étude examine la microphysique de la formation des granules de glace. Plus précisément, la capacité de ces granules de former des agrégats et les conséquences de ces agrégats sur les autres types de précipitation présents. Cette recherche repose sur l'étude du regel d'une distribution de pluie verglaçante dans une atmosphère sous le point de congélation à l'aide de simulations incluant les interactions entre particules. Une attention particulière a été prêtée sur trois principaux aspects. Premièrement, trois mécanismes formant des agrégats de particules ont été étudiés. Deuxièmement, les collisions parmi les particules entraînées dans ces mécanismes ont été modélisées. Finalement, l'importance relative de chaque mécanisme a été déterminée. Les résultats illustrent que pour les conditions atmosphériques considérées, la pluie verglaçante est souvent collectée par les agrégats de particules formés durant leur descente dans l'atmosphère. De plus, l'agrégation de particules s'avère efficace à l'élimination complète de la pluie verglaçante dans des conditions atmosphériques précises et favorables.
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Ferreira, Ana Helena Ferreira. "Peptides in Cyanobacteria under different environmental conditions." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979948371.
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GASTOLDI, LUCIA. "Cyanobacteria Sulfur Metabolism under Precambrian environmental Conditions." Doctoral thesis, Università Politecnica delle Marche, 2020. http://hdl.handle.net/11566/274568.
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Durante il Precambriano, le variazioni di SO42- negli oceani sono state così importanti da ipotizzare che la disponibilità di S abbia influenzato l’evoluzione del fitoplancton. Ho investigato come la regolazione del suo metabolismo nei cianobatteri possa essere cambiata nel tempo, concentrandomi sul primo step della catena assimilativa controllato dalla ATP sulforilasi (ATPS). I cambiamenti ambientali preistorici hanno influenzato la chimica oceanica portando ad un aumento del SO42- disponibile, a una diminuzione del Fe disciolto e ad un aumento nel consumo di equivalenti riducenti. Questi fattori avrebbero potuto influenzare l'uso di equivalenti riducenti negli organismi unicellulari primitivi, con evidenti ripercussioni sulla regolazione del metabolismo e sulla distribuzione delle risorse. Poiché la prima produzione primaria dipendeva principalmente dai cianobatteri fotossigenici, mi sono concentrata su di essi, studiandone le prestazioni fisiologiche, la composizione chimica e la ripartizione di risorse in ambiente proterozoico ricostruito e in quello moderno. Per comprendere l'impatto che i cambiamenti ambientali potrebbero aver avuto sull'ecologia degli oceani, ho analizzato le conseguenze sulla qualità della biomassa cianobatterica. I risultati ottenuti indicano 1) che le variazioni della disponibilità di O2 influenzano il tasso di crescita nei cianobatteri, 2) che la limitazione dei nutrienti unita alla variazione del potere riducente disponibile ha un effetto sull'attività delle ATPS (la concentrazione di nutrienti sembra avere un effetto più forte), e 3) che la limitazione dei nutrienti influenza l'assimilazione degli elementi e il pool macromolecolare. È possibile concludere che l'ossigenazione del pianeta potrebbe non essere stata l'unico vincolo evolutivo per lo sviluppo di una regolazione redox nelle ATPS. Inoltre i risultati biochimici supportano la teoria per cui i cianobatteri evolvendosiin acqua dolce hanno conquistato solo secondariamente l'oceano.During Precambrian, sulfate variations were so strong that one hypothesis guesses that S availability influenced phytoplankton evolution/radiation in the oceans. Considering this concept, I investigated how sulfate metabolism regulation in cyanobacteria may have changed through geological times focusing on the first step of the S assimilation pathway, which is controlled by the ATP sulfurylase (ATPS) protein. Precambrian environmental changes caused variation in the ocean chemistry, leading to an increase of sulfate availability, a decrease of dissolved Fe and, an increase in sinks for reducing equivalents in cell metabolism. Since all these factors could have influenced the usage of reducing equivalents in primitive unicellular organisms, evident repercussions on their metabolism regulation and resource/energy allocation/distribution are ensuing. Since the early primary production mostly depended on photo-oxygenic cyanobacteria, I focused on them studying their physiological performance, their chemical composition, and their resource and energy partitioning in the reconstructed proterozoic environment and in the modern one. To understand the impact that environmental changes may have had on ocean ecology, I also studied consequences on cyanobacterial biomass quality, to comprehend the consequences on the trophic webs. Present results point out that (1) oxygen availability variations influence growth rate in cyanobacteria, (2) nutrient limitation combined with redox power variation has an effect on the ATPS activity, but the nutrient concentration seems to be the strongest one, (3) nutrient limitation influences elements assimilation and macromolecular pool in cyanobacteria. It is possible to conclude that the oxygenation of the planet may not have been the only evolutive constraint for redox regulation in ATPS enzymes. Moreover, biochemical results support the theory stating cyanobacteria evolved in the freshwater environment and only secondly conquered the ocean.
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Roncarati, Francesca <1977>. "Phytoplankton physiological responses under changing environmental conditions." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/541/1/roncarati_francesca_tesi.pdf.
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Roncarati, Francesca <1977>. "Phytoplankton physiological responses under changing environmental conditions." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/541/.
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Kiorapostolou, Natasa. "Tree growth responses to different environmental conditions." Doctoral thesis, Università degli studi di Padova, 2020. http://hdl.handle.net/11577/3425789.
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Increasing frequency and intensity of droughts affect forest ecosystems. There are already higher rates of tree mortality and forest drought-induced dieback. Since climate change affects the soil conditions, the precipitation rates and the growth seasons, it is expected that trees will develop acclimation and adaptation strategies in order to maintain vigor. Since the two most important reasons of mortality are carbon starvation and hydraulic failure, adjustments in physiological traits are expected to be related to the maintenance of the tree carbon and water balances.
This thesis focused on understanding how trees respond under different environmental conditions (e.g. wet vs dry) both at the intraspecific and interspecific level. The conducted studies focused on biomass allocation, xylem and phloem anatomies of stem and branches, xylem anatomy of leaves, plant hydraulics, and wood density. Mostly, data from personal measurements were used, but also published data to compare the results. The aim was to understand which structural traits are linked to the acclimation and adaptation strategies of trees and how.
The structure of the thesis is: (i) general introduction, (ii) five main chapters based on different studies, (iii) one main chapter describing in short three more studies, (iv) overall conclusion, (v) additional information for each of the main chapters (if applicable), (vi) acknowledgments, (vii) anatomical images for some chapters, (viii) literature cited listed per chapter.
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Bernelot, Moens Rachel. "Environmental conditions regulating gene transfer in Rhodobacter capsulatus." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43523.
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Rhodobacter capsulatus is a metabolically versatile α-proteobacterium that produces a
bacteriophage-like particle called the gene transfer agent (RcGTA) that is capable of mediating
horizontal gene transfer. RcGTA particles transfer random 4.5 kb fragments of genomic DNA
that integrate into recipient genomes by allelic replacement. This thesis addresses certain
environmental conditions, in particular carbon limitation and the presence of subinhibitory
concentrations of antibiotics, that influence gene transfer by RcGTA. A new transduction assay
was developed to test the effects of various substances on gene transfer. Using this transduction
assay, both carbon limitation and low levels of DNA gyrase inhibitors were found to increase the
frequency of gene transfer, although by different mechanisms. Carbon limitation caused an
increase in production and release of RcGTA. This effect was a general response to carbon
limitation, and was independent of carbon source. Gyrase inhibitors, on the other hand, did not
influence production or release of RcGTA and instead were thought to act on the recipient cells
via DNA gyrase. GyrB overexpression constructs were made in order to confer resistance to
novobiocin. The presence of these constructs negated the novobiocin-mediated increase in gene
transfer. The results of this thesis suggest that certain antibiotics as well as carbon limitation
affect gene transfer in R. capsulatus and may be relevant to microbial genetic exchange in
natural ecosystems.
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Husby, Arild. "Ecological genetics of populations experiencing changing environmental conditions." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/5672.
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A major goal in evolutionary biology is to understand how ecological factors shape the phenotypic and genetic variation that we observe in natural populations and in this thesis I examine how rapid changes in temperature have influenced phenotypic and genetic variation in morphological and life history traits in long-term studies of great tits. In Chapter 1 I review what is known about the effects of environmental change on natural populations, and outline the quantitative genetic framework that is available to study genetic variation in natural populations. Much focus on the effects of climate change has concerned species’ phenology, far less attention has been given to other traits. In Chapter 2 I examine the effects changing environmental conditions have had on the proportion of females that produce second broods. Temperature operates mainly through indirect effects (such as food abundance) but may also have more direct effects. In Chapter 3 I show that over a 36 year period body size have declined in line with predictions from Bergmann’s rule and I explore the genetic basis of this decline and the environmental factors involved. Although we can learn much from population level responses, there is a great deal of additional information to be gained by studying between-individual responses. In Chapter 4 I therefore compare the multivariate pattern of between-individual variation in phenotypic plasticity and its genetic basis for laying date and clutch size, in two great tit populations. Environmental changes may also directly affect the expression of genetic variance as well as the strength of selection acting on a trait, and in Chapter 5 I show that, for laying date, the environment induces a positive covariance between strength of selection and the expression of additive genetic variance, something that may enhance the rate of adaptation. Finally, in Chapter 6 I discuss and summarise the wider implications of the findings from this thesis.
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Perkins, Kerry. "Cuttlefish (Sepia officinalis) camouflage in varying environmental conditions." Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/68322/.
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Cephalopods first appeared around 500 million years ago. Since then they have developed from the external shelled ammonites, belemnites and nautiloid's to the soft bodied organisms we find today. By becoming soft bodied, protection which would have been provided by the shell was lost and a different approach to predator avoidance was adopted. Modern day cephalopods such as octopus, squid and cuttlefish frequently use camouflage techniques to avoid detection. In addition to countershading, which is an often used camouflage technique by aquatic species, the presence of chromatophores allow a versatile and rapid response in relation to stimuli. Cuttlefish expression of these chromatic responses can be categorised into chromatic components. It is the intensity and combination of the expression which makes them an interesting organism to study, when looking at how the environment influences camouflage decisions. In this thesis, I present six experiments looking at how external environmental factors influence camouflage in Sepia officinalis. The first experimental chapter looks at how 3D objects and proximity play a role in not only camouflage, but behavioural responses. The first set of experiments discuss how factors such as contrast and size of an object may elicit different responses both behaviourally and chromatically. The proximity of the cuttlefish to the object was then investigated to determine if visual input was a possible cause for the differences. Size of the object, proximity and contrast produced a differing response to that of a cuttlefish on a uniform background. The two subsequent chapters look at differing light information and whether cuttlefish treat these differences similar to that of low contrast. Reaction to turbid and low light levels show similar responses in camouflage, suggesting that similar mechanisms are employed when there is reduced light and high scatter information. In respect to luminance versus reflectance, cuttlefish seem to be able to differentiate between a projected and reflected image where they appear to treat projected images like a lower contrast value. The last experimental chapter investigates motion camouflage in respect to predation. Prey and distance had a large effect on behaviour and how camouflage was expressed. Over greater distances behavioural variance reduced. Darkening of the head region and arm waving was also present over a greater distance. Camouflage varied in relation to background with a more uniform background producing reduced expression when moving. Stationary predation therefore elicits a different response than that of motion camouflage in cuttlefish.
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Гладченко, Оксана Робертівна, Оксана Робертовна Гладченко, Oksana Robertivna Hladchenko, and I. R. Khakimova. "Environmental protection in the conditions of country development." Thesis, Вид-во СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/21969.
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Environmental protection is one of the main problems nowadays. Technological progress improves people’s life, but at the same time it causes numerous problems that were unimaginable in the past centuries. What will be the verdict of time on the man-made world?
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/21969
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Гладченко, Оксана Робертівна, Оксана Робертовна Гладченко, Oksana Robertivna Hladchenko, and I. R. Khakimova. "Environmental protection in the conditions of country development." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/13419.
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Gopinath, Rakesh. "Concrete carbonation prediction for varying environmental exposure conditions." Doctoral thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/32700.
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The Durability Index (DI) approach has been developed in South Africa, in order to improve the durability performance of reinforced concrete structures. The DI approach is based on durability index tests, which are linked to transport mechanisms related to particular deterioration processes (Alexander et al., 1999a). Carbonation of concrete is governed, inter alia, by the microstructure and the transport characteristics of the concrete. A carbonation model with permeability coefficient (k) from the Oxygen Permeability Index (OPI) test as the key material variable was developed by Salvoldi (2010) using accelerated carbonation test data. The main aim of this research is to further develop the carbonation model by adopting the modelling framework of Salvoldi (2010) using natural carbonation data. For the experimental work, a total 48 different concrete mixes were produced by with different water: binder ratios (w/b), cement types, cement extender (addition) type and curing regime. The OPI test was conducted on all the concretes, and their corresponding permeability coefficients were determined. A set of 48 concrete specimens were exposed to five different sites for natural carbonation, and carbonation depths were measured periodically. Based on the modelling framework of Salvoldi (2010) and using the natural carbonation data between 150- 850 days, a model predicting the depth of natural carbonation was developed. However, in the case of concrete exposed to rain, drying/wetting is a major factor influencing the rate of carbonation. Therefore, the carbonation model was further modified taking into account the influence of drying/wetting cycles, by coupling it with a moisture model. For the development of the moisture model, the concrete specimens were exposed to a laboratory environment maintained at constant temperature and relative humidity (RH). The internal RH of the concrete specimens at varying depth was measured at different time intervals. Based on the measured RH data, the moisture model was also developed with ‘k' from the OPI test as the key input parameter. The moisture model was then coupled with the carbonation model developed. This provides an integrated and powerful solution for predicting carbonation of concrete both sheltered and exposed to rain by using only one main material input parameter ‘k', which is one of the major contributions of this research.
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Al-Homidan, Abrahim A. "The effect of environmental conditions on broiler performance." Thesis, University of Aberdeen, 1997. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU483542.
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1- Body weight was significantly affected by temperature at 49 days in all three experiments. Body weight was higher at the lower temperature (2591 vs 2518 g).2- Body weight was significantly affected by the light regime at 6 weeks of age. Body weight was higher with intermittent light (9L : 3D) compared to continuous light (23L : 1D) (2223 vs 2164 g).3 - As expected, given the differences in body weight at 49 days, at 6 weeks of age daily weight gain was significantly affected by temperature, and by light regime (52.5 vs 50.8 and 50.4 vs 51.8 g respectively).4- Ammonia concentrations increased greatly with the age of the birds. The mean concentrations in experiments 1 and 3 all fell below the recommended for animal threshold limit value of 20 ppm ( but in experiment 2 the mean concentrations of ammonia were higher (28 ppm) than the recommended TLV of 20 ppm.5- Ammonia concentration was significantly greater in rooms with a litter depth of 30 mm (32 ppm) compared with 45mm, (24.2 ppm).6- Ammonia concentration was greater than 'Litterite' than wood shavings after the third week (11.2 vs 7.9 ppm)7- Inspirable dust concentration was significantly greater in rooms at the higher temperature in all the three experiments (10 vs 13.3 mg/m3) and in rooms with near-continuous light in experiment 1 (8.5 vs 5.7 mg/m3).8- Settled dust concentration was significantly greater in rooms at higher temperature in all experiment 2 and 3 (614.5 vs 474.35 mg/m2).9- Ammonia concentration was higher (but NS) in rooms at the higher temperature (21°C) compared with rooms at the low temperature (19°C) in all three trials (19.3 vs 22.3 ppm).10- Stocking density significantly affected ammonia concentrations in the 5th week and from 3-7 weeks of age (8.9 vs 13.3 ppm) (8.5 vs 11.2) respectively. Overall, the lower temperature (19 C), intermittent light, a litter depth of 45mm and a low stocking density (16 birds/m2) led to reduced ammonia and dust concentrations, an increased body weight, and daily weight gain and reduced mortality (NS).
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Cavaliere, Emily Homann Peter S. "Elwha River sediments : phosphorus dynamics under diverse environmental conditions /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=344&CISOBOX=1&REC=18.
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Cordero, Arias Josbel Andreina. "Experimental analysis of soil cracking due to environmental conditions." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/667471.
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This thesis presents an experimental approach on the subject of cracking in soils due to changes in environmental conditions, where research is mainly directed to the soil-air interface and the effect of boundary conditions. At the theoretical level, hypotheses put forward by various authors on the cracking of soils in terms of origin and crack propagation are considered, which serve as a reference to describe the behavior obtained from the tests.
The objectives of the thesis belong to a line of research dedicated to studying the desiccation of soils and their implications in engineering works. The work consisted in the implementation of a one-year-long field test, subjected to natural environmental conditions, instrumented to monitor and record the main variables within the soil (temperature, volumetric water content, suction) and others very close to the ground-air interface area (wind speed and direction, temperature, relative humidity, solar radiation, rain intensity). For the laboratory experiments, significant improvements have been made in the existing environmental chamber to allow wetting of the specimens, and the automatic control of drying and wetting cycles. The cycles of humidity in the environmental chamber and the periods of rain and drought selected from the one-year-long field test measurements have been devised to study the behavior of the cracks in response to the variation of water content in the soil.
Several types of soil have been used for the development of the tests. One of the soils was a silty clay from the Campus Nord of the UPC in Barcelona, already well characterized in works already published. Another soil, used in both laboratory and field experiments, is a silty clay from the Agròpolis agricultural campus in Viladecans. This clay is characterized in depth in this thesis. To study the cracking of soils as an effect of suction and contraction, mixtures of Jeddah sand (Saudi Arabia) with Gordon’s Kaolinite (United States) have been used.
The analysis of the results is based on concepts of classical soil mechanics and unsaturated soil mechanics, notions of agro-meteorology, application of techniques for image analysis and concepts previously developed in the research group. Some theoretical analysis has been carried out to explain the results obtained and to reach conclusions on the proposed objectives.
In general, the results of the laboratory experiments confirm some hypotheses and coincide with observations from previous published studies. The modified soil classification system RSCS has worked well as a tool to anticipate the transition of the capillarity phenomenon and the tendency to cracking by drying according to the input parameters required by that classification system. The combination of laboratory and field experiments has led to the conclusion that drying in the field is more efficient than in the environmental chamber, despite an extreme decrease of the relative humidity, given that there are natural variables that affect the boundary conditions and may have effects on the process of cracking in the ground.Esta tesis presenta un enfoque experimental sobre el tema de agrietamiento en suelos debido a cambios en las condiciones medioambientales, donde la investigación se dirige principalmente a la interface suelo-aire y al efecto del contorno. A nivel teórico se consideran hipótesis expuestas por diversos autores sobre el agrietamiento de suelos en términos de origen y propagación de grietas, que sirven de referencia para describir el comportamiento obtenido de los ensayos. Los objetivos de la tesis se enmarcan dentro de una línea de investigación dedicada a estudiar la desecación de suelos y sus implicaciones en obras de ingeniería. El trabajo ha consistido en la implantación de un ensayo en campo a largo plazo, de un año de duración, sometido a las condiciones ambientales naturales, instrumentado para el registro de variables dentro del suelo (temperatura, contenido de humedad volumétrico, succión) y otras muy cercanas a la zona de la interface suelo-aire (velocidad y dirección del viento, temperatura, humedad relativa, radiación solar, intensidad de la lluvia). En el ámbito experimental de laboratorio se han hecho mejoras importantes en la cámara ambiental existente para permitir reproducir la humectación de las muestras y el control automático de ciclos de secado y humedecimiento. Los ciclos de humedad en cámara ambiental y periodos de lluvia y sequía seleccionados del año de medición al aire libre se plantean para estudiar el comportamiento de las grietas como respuesta ante la variación del contenido de agua en el suelo. Para el desarrollo de los ensayos se han utilizado varios tipos de suelo. Uno ha sido la arcilla limosa del Campus Nord de la UPC en Barcelona, ampliamente estudiada en trabajos ya publicados. Otro suelo, utilizado tanto en experimentos de laboratorio como en campo, es una arcilla limosa del campus agrario Agròpolis en Viladecans. Esta arcilla se caracteriza en profundidad en la presente tesis. Para estudiar el agrietamiento de suelos como un efecto de la succión y la retracción se han utilizado mezclas de arena de Jeddah (Arabia Saudí) con Caolinita de Gordon (Estados Unidos). El análisis de los resultados se basa en conceptos de la mecánica de suelos clásica y mecánica de suelos no saturados, nociones de agro-meteorología, aplicación de técnicas para el análisis de imagen y fundamentos definidos en trabajos previos del grupo de investigación. Se ha llevado a cabo un tipo de análisis teórico para explicar los resultados obtenidos y concluir sobre los objetivos planteados. En general los resultados de los experimentos de laboratorio confirman algunas hipótesis planteadas y coinciden con observaciones de estudios previos publicados. El sistema modificado de clasificación de suelos RSCS ha funcionado como una herramienta para anticipar la transición del fenómeno de capilaridad y la tendencia al agrietamiento por desecación según los parámetros de entrada que requiere el sistema de clasificación mencionado. La combinación de experimentos en laboratorio y en campo han llevado a concluir que el secado en campo es más eficiente que en la cámara ambiental, aunque se extreme la disminución de la humedad relativa, dado que hay variables naturales que afectan las condiciones de contorno y pueden llegar a tener efectos en el proceso de formación de grietas en el suelo.
Aquesta tesi presenta un treball experimental sobre el tema d'esquerdament en sòls a causa de canvis en les condicions mediambientals, on la investigació es dirigeix principalment a la interfície sòl-aire i a l'efecte de les condicions de contorn. A nivell teòric es consideren hipòtesis exposades per diversos autors sobre l'esquerdament de sòls en relació a la formació i propagació d'esquerdes, que serveixen de referencia per descriure els comportaments obtingut dels assajos. Els objectius de la tesi s'emmarquen dins d'una línia de recerca dedicada a estudiar la dessecació de sòls i les seves implicacions en obres d'enginyeria. El treball ha consistit en la implantació d'un assaig en camp a llarg termini, d'un any de durada, sotmès a les condicions ambientals naturals, instrumentat per al registre de variables dins del sòl (temperatura, contingut volumètric d'humitat, succió) i altres molt properes a la zona de la interfície sòl-aire (velocitat i direcció del vent, temperatura, humitat relativa, radiació solar, intensitat de la pluja). En l'àmbit experimental de laboratori s'han fet millores importants en la cambra ambiental existent per permetre reproduir la humectació de les mostres i el control automàtic de cicles d'assecat i humitejament. Els cicles d'humitat en cambra ambiental i els períodes de pluja-sequera seleccionats de l'any de mesurament a l'aire lliure es plantegen per estudiar el comportament de les esquerdes com a resposta davant la variació del contingut d'aigua en el sòl. Per al desenvolupament dels assajos s'han utilitzat diversos tipus de sòl. Un tipus de sòl és l'argila llimosa del Campus Nord de la UPC a Barcelona, àmpliament estudiada en treballs ja publicats. Un altre sòl, utilitzat tant en experiments de laboratori com en el de camp, és una argila llimosa del campus agrari Agròpolis a Viladecans. Aquesta argila s'ha caracteritzat en profunditat en la present tesi. Per estudiar l'esquerdament de sòls com un efecte de la succió i la retracció s'han utilitzat mescles de sorra de Jeddah (Aràbia Saudita) amb caolinita de Gordon (Estats Units). L’anàlisi dels resultats es basa en conceptes de la mecànica de sòls clàssica i mecànica de sòls no saturats, nocions d'agro-meteorologia, aplicació de tècniques per a l’anàlisi d'imatge i altres conceptes definits en treballs previs del grup de recerca. S'ha dut a terme un tipus d’anàlisi teòrica per explicar els resultats obtinguts i concloure sobre els objectius plantejats. En general els resultats dels experiments de laboratori confirmen algunes hipòtesis plantejades i coincideixen amb observacions d'estudis publicats prèviament. El sistema modificat de classificació de sòls RSCS ha funcionat com una eina per anticipar la transició del fenomen de capil·laritat i la tendència a l'esquerdament per dessecació segons els paràmetres d'entrada que requereix el sistema de classificació esmentat. La combinació d'experiments en laboratori i en camp han portat a la conclusió que l'assecat en camp és més eficient que a la cambra ambiental, malgrat la disminució extrema de la humitat relativa, atès que hi ha variables naturals que afecten les condicions de contorn i poden arribar a tenir efectes en el procés de formació d'esquerdes en el sòl.
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Moorby, H. "Environmental conditions affecting acid-base changes around plant roots." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375279.
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Reynolds, Michael. "Behavioural responses of fish to parasitism and environmental conditions." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/108207/.
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Every aspect of an individual’s behaviour is, to some extent, mediated by parasite exposure. Potential hosts can, for example, initiate evasive behaviours towards infected conspecifics to reduce infection risk. If infected, individuals may exhibit adaptive behavioural responses aimed at reducing pathological symptoms. In addition to infection-mediated behavioural modifications, hosts behaviourally adapt to the environment in which they reside. Disentangling the effects of parasitism from environmental variables on host behaviour can be challenging. In a series of self-contained experiments, this thesis investigates three research areas. Firstly, how thermal and hydrological environmental conditions impact freshwater host-parasite interactions; secondly, how parasite infections mediate host behavioural modifications; and finally, how such behavioural changes have population level effects with respect to social structuring. The first experiment in this thesis describes how, when presented with a range of thermal conditions, Trinidadian guppies, Poecilia reticulata Peters 1859, infected with a common monogenean ectoparasite, Gyrodactylus turnbulli Harris 1986, frequent warmer thermal conditions to self-medicate against infection (Chapter 2). In a second experiment, G. turnbulli infected guppies experiencing dissimilar flow conditions showed a significant decrease in shoaling tendencies; but only in the absence of flowing water (Chapter 3). During this experiment, infected fish were observed increasing body contact with conspecifics: a behavioural adaptation presumably aimed at offloading parasite burdens (investigated in Chapter 4). Furthermore, infected hosts exhibited nocturnal restlessness, which may have further repercussions for host health (Chapter 5). Finally, parasite-mediated host behavioural modifications had significant population level effects with respect to social structuring. G. turnbulli infected guppies significantly increased their social rank within a population and instigated more contacts than they received, in contrast to their uninfected counterparts (Chapter 6). The infection status of an individual therefore determines its significance in mediating a population’s social dynamics, and so driving disease transmission processes.
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Maheras, Anastasia Francis. "Assessing United States hurricane damage under different environmental conditions." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78479.
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Thesis (S.M. in Atmospheric Science)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 47-53).
Hurricane activity between 1979 and 2011 was studied to determine damage statistics under different environmental conditions. Hurricanes cause billions of dollars of damage every year in the United States, but damage locations and magnitudes vary from year to year. Seasonal hurricane forecasts predicting the strength of the upcoming hurricane season have the potential to be used by many industries and sectors to reduce and mitigate the effects of hurricanes. However, damage itself is not predicted by these forecasts. This work analyzed trends in hurricane damage due to atmospheric and oceanic conditions, and the results could be applied to and included in seasonal hurricane forecasts, thus increasing forecast applicability and value. This work used synthetic hurricane tracks generated from background climate conditions, a U.S. property portfolio, and a damage function based on wind speed to determine 1979-2011 hurricane damage. Damage was split into La Niña/El Niño and pre-/post- 1995 year sets to determine spatial and temporal trends in U.S. hurricane damage. This work concluded that different regions of the country experienced more or less hurricane damage under different environmental conditions. Knowledge of these trends can be applied to seasonal hurricane forecasts and can influence property owner, regulator, and insurer behavior across the nation.
by Anastasia Francis Maheras.
S.M.in Atmospheric Science
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Marks, Christopher. "Quantitative Genetics of Zebrafish Ontogeny Under Changing Environmental Conditions." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1334778150.
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CHANDRASEKAR, SUBHASHINI. "DISPERSANT EFFECTIVENESS DATA FOR A SUITE OF ENVIRONMENTAL CONDITIONS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1083270706.
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Ali, Hatim F. A. "Assessment of lime-treated clays under different environmental conditions." Thesis, University of Bradford, 2019. http://hdl.handle.net/10454/18313.
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Natural soils in work-sites are sometimes detrimental to the construction of engineering projects. Problematic soils such as soft and expansive soils are a real source of concern to the long-term stability of structures if care is not taken. Expansive soils could generate immense distress due to their volume change in response to a slight change in their water content. On the other hand, soft soils are characterised by their low shear strength and poor workability. In earthwork, replacing these soils is sometimes economically and sustainably unjustifiable in particular if they can be stabilised to improve their behaviour. Several techniques have evolved to enable construction on problematic soils such as reinforcement using fibre and planar layers and piled reinforced embankments.
Chemical treatment using, e.g. lime and/or cement is an alternative method to seize the volume change of swelling clays. The use of lime as a binding agent is becoming a popular method due to its abundant availability and cost-effectiveness. When mixed with swelling clays, lime enhances the mechanical properties, workability and reduces sensitivity to absorption and release of water. There is a consensus in the literature about the primary mechanisms, namely cation exchange, flocculation and pozzolanic reaction, which cause the changes in the soil characteristics after adding lime in the presence of water. The dispute is about whether these mechanisms occur in a sequential or synchronous manner. More precisely, the controversy concerns the formation of cementitious compounds in the pozzolanic reaction, whether it starts directly or after the cation exchange and flocculation are completed.
The current study aims to monitor the signs of the formation of such compounds using a geotechnical approach. In this context, the effect of delayed compaction, lime content, mineralogy composition, curing time and environmental temperature on the properties of lime-treated clays were investigated.
The compaction, swelling and permeability, and unconfind compression strength tests were chosen to evaluate such effect. In general, the results of the geotechnical approach have been characterised by their scattering. The sources of this dispersion are numerous and include sampling methods, pulverisation degree, mixing times and delay of compaction process, a pre-test temperature and humidity, differences in dry unit weight values, and testing methods. Therefore, in the current study, several precautions have been set to reduce the scattering in the results of such tests so that they can be used efficiently to monitor the evolution in the properties that are directly related to the formation and development of cementitious compounds. Four clays with different mineralogy compositions, covering a wide range of liquid limits, were chosen. The mechanical and hydraulic behaviour of such clays that had been treated by various concentrations of lime up to 25% at two ambient temperatures of 20 and 40oC were monitored for various curing times.
The results indicated that the timing of the onset of changes in mechanical and hydraulic properties that are related to the formation of cementitious compounds depends on the mineralogy composition of treated clay and ambient temperature. Moreover, at a given temperature, the continuity of such changes in the characteristics of a given lime-treated clay depends on the lime availability.
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Velpuri, Seshagirirao V. "Fracture Toughness Testing of Plastics under Various Environmental Conditions." Thesis, University of North Texas, 1997. https://digital.library.unt.edu/ark:/67531/metadc278346/.
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The primary objective of this study is to test the applicability to plastics of a fracture toughness testing tool developed for metals. The intent is to study pre-test conditioning of several plastic materials and the effect of the depth of the razor notch cut in the chevron notched fracture toughness test specimens. The study includes the careful preparation of samples followed by conditioning in various environments. Samples were subjected to laboratory air for a specific duration or to a controlled temperature-humidity condition as per the ASTM D1870. Some of the samples were subjected to vacuum conditioning under standard test specifications. Testing was conducted using the conventional three-point bend test as per ASTM D5045-95. ASTM E1304, which sets a standard for short rod and bar testing of metals and ceramics provides some basis for conducting chevron notched four-point bend tests to duplicate the toughness tool. Correlation of these results with the ASTM test samples is determined. The four-point bend test involves less specimen machining as well as time to perform the fracture toughness tests. This study of fracture toughness testing has potential for quality control as well as the fracture property determination.
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Zhang, Fangzhou. "Multiscale modeling of laminated composites under extreme environmental conditions." Thesis, Cachan, Ecole normale supérieure, 2014. http://www.theses.fr/2014DENS0027/document.
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À haute température, l'oxygène réagit avec la matrice organique du matériau composite, ce qui change les propriétés du matériau et réduit la résistance à la rupture globale. Mais la compréhension de la dégradation du composite stratifié oxydé, en particulier son comportement à l'échelle du pli, est aujourd'hui limitée et phénoménologique. Les travaux dans cette thèse ont été réalisés pour donner notre contribution sur les aspects méthodologiques de ce sujet. Des essais sont réalisés pour caractériser expérimentalement le comportement d'éprouvette oxydée : en particulier, un nouveau essai, l'essai 'oxy-délaminage', a été développé pour identifier la ténacité du matériau composite vieilli. Une stratégie a été proposée d'étudier le problème à partir des propriétés de la matrice oxydée à l'échelle fibre/matrice et jusqu'à la reproduction et la prédiction du comportement de fissuration transversale des échantillons oxydés à échelle méso via un procédé d'homogénéisationAt high temperature, the oxygen reacts with the organic matrix of composite material, which changes the material properties and reduces the resistance to global failure. But understanding on the degradation of the oxidized composite laminate, particularly its damage behavior, is now limited and phenomenological. Work in this thesis has been made to give our contribution to the methodological aspects of this topic. Tests are performed to characterize experimentally the behaviors of the oxidized specimens: in particular, a new test test oxy-delamination ', was developed to identify the tenacity of composite material aged. A strategy has been proposed to study the problem from the properties the oxidized matrix at the fiber/matrix scale up to the reproduction and predicting the behavior of transverse cracking of the sample at the scale of a ply via a homogenization process
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Elguindi, Jutta Ehlert. "Antimicrobial Efficacy of Copper Alloys in Changing Environmental Conditions." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/202696.
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Copper cast alloys de-activate antibiotic-resistant bacteria on contact and could be very effective in decreasing potentially harmful microorganisms in the environment. In this study copper alloys with varying copper contents were utilized to evaluate their antimicrobial effects on Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecium in changing environmental conditions. The survival rates of P. aeruginosa wild type and its derivative transposon mutants of the cin operon on copper cast alloys were investigated in order to demonstrate the influence of genes involved in copper resistance. The gene disruption of the response regulator of the cin operon resulted in shorter survival rates on copper alloys, which was also influenced by temperature and method of exposure. Bacteria often have acquired copper resistance mechanisms in order to withstand higher copper concentrations in their surroundings, which may be a factor in their survival rates on copper surfaces. Copper- and antibiotic-resistant E. coli and E. faecium strains were obtained from pigs raised on feeds containing copper sulfate and antibiotics. Survival rates of these bacteria were influenced by the percentage of copper in the alloys, varying moisture conditions on copper surfaces, suspension media used, and differences between strains. Survival was also dependent on copper corrosion rates since corrosion inhibition with benzotriazole or a thick surface layer of thermal oxide resulted in prolonged survival on copper surfaces. Corrosion of copper surfaces releases copper ions which directly affect bacterial survival on copper alloys. The results obtained in this study emphasize that copper alloys are effective as antimicrobial materials but changing environmental conditions can significantly influence bacterial survival on copper surfaces. These findings can be applied to a better utilization of copper alloys in water, food, and healthcare environments. Antibiotic- and copper ion-resistant bacteria can be killed on contact with copper alloys which makes the proliferation of these microorganisms less likely and reduces the risk to human health. However, in a very different environment copper ion-resistant microbes can be useful for plant-microbe associations in bioremediation of copper mining wastelands.
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ROSSI, Miriam. "Analysis of poplar plants responses to environmental stress conditions." Doctoral thesis, Università degli studi del Molise, 2017. http://hdl.handle.net/11695/79757.
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La problematica dei cambiamenti ambientali, alterando la funzionalità degli ecosistemi e la naturale distribuzione delle specie sul pianeta terra, ha destato negli ultimi anni una giustificata e crescente preoccupazione da parte della comunità scientifica e delle autorità locali (Aber et al., 2001; Loreau et al., 2001). Come ampiamente documentato in letteratura, i cambiamenti climatici e le varie forme di inquinamento ambientale rappresentano alcune tra le principali cause delle drammatiche alterazioni riscontrate a livello ambientale. Infatti, l’immissione nell’ambiente di sostanze tossiche può risultare letale per tutti gli esseri viventi che abitano il pianeta terra (piante, animali e uomo). Inoltre, assieme ai cambiamenti climatici mondiali, l’inquinamento ambientale è stato identificato dalla comunità scientifica come una delle principali cause dell’estinzione delle specie (Leduc et al., 2004).
Spesso i cambiamenti ambientali possono divenire fattori di stress per le piante (es. siccità, salinità, inquinanti o stress meccanico; Boyer, 1982). Nonostante ciò, queste ultime, per resistere e adattarsi a condizioni ambientali avverse, hanno sviluppato differenti strategie di risposta (Boyer, 1982; Nilsen and Orcutt et al., 1996; Borics et al., 2013) che comprendono vari adattamenti morfologici, fisiologici, biochimici e molecolari. Lo studio dei meccanismi di risposta delle piante agli stress ambientali è diventato negli ultimi anni oggetto di una intensa attività di ricerca in quanto approfondire i meccanismi che consentono alla specie vegetali di fronteggiare condizioni ambientali avverse può contribuire non solo ad ampliare le conoscenze inerenti alla biologia vegetale di base ma anche ad implementare l’efficienza delle strategie basate sull’ uso delle piante per la mitigazione degli stress ambientali (Mbow et al., 2014).
La ricerca di base presentata in questa tesi di dottorato ha come principale oggetto di studio l’analisi dei meccanismi molecolari di risposta di specie arboree perenni agli stress ambientali. In particolare, l’attenzione è stata focalizzata sullo stress meccanico e sullo stress da metalli pesanti.
La prima parte di questa tesi fornisce nuove informazioni sul complesso e ancora poco conosciuto meccanismo molecolare che modula la risposta dei sistemi radicali di specie arboree perenni allo stress meccanico. Quest’ultimo rappresenta una tipologia di stress ambientale molto comune in natura che può condizionare drammaticamente la crescita, lo sviluppo e la stabilità delle piante. Nel dettaglio, in questo studio, mediante un semplice sistema sperimentale (Trupiano et al 2012a, b) è stato possibile simulare lo stress meccanico in radici di Populus nigra. Per approfondire i meccanismi molecolari di risposta allo stress meccanico, sono state prima valutate le variazioni proteomiche e il ruolo dell’ormone vegetale auxina e successivamente sono stati valutati i livelli di espressione di alcuni miRNAs (micro RNAs) in risposta allo stress meccanico. Utilizzando la tecnica denominata reverse transcription-quantitative PCR (RT-qPCR) è stato possibile valutare i livelli di espressione di cinque miRNAs (ptc-miR162, ptc-miR164, ptc-miR172, ptc-miR408, ptc-miR473) precedentemente identificatiti da Lu et al., (2005) in fusti di piante di pioppo sottoposte a stress meccanico. Inoltre, lo studio presentato in questa tesi fornisce l’analisi dei cis-regulatory promoter elements e la predizione computazionale e sperimentale dei geni target dei cinque miRNAs precedentemente valutati. I risultati ottenuti in questa tesi permettono di evidenziare che il pattern di espressione dei cinque miRNAs valutati non è regolato solamente dalle forze di compressione e tensione che si generano lungo la radice soggetta a stress da piegamento (Trupiano et al., 2012 a, b), ma anche da altri importanti processi quali la formazione di radici laterali e la deposizione di lignina.
Dopo aver focalizzato l’attenzione sullo stress meccanico, nella seconda parte di questa tesi è stata affrontata la tematica del rizorimedio che rappresenta un’importante strategia incentrata sulle interazioni pianta-microrganismo per ridurre le concentrazioni di metalli pesanti da siti contaminati (Glick, 2003). I risultati preliminari dello studio dimostrano che un ceppo microbico appartenente al genere Bacillus isolato da un campione di suolo contaminato da piombo (Pb) e arsenico (As) mostra una grande capacità di tollerare l’esposizione ad arsenico e piombo e che potrebbe per questo essere utilizzato in futuro in associazione con diverse specie vegetali per diminuire le concentrazioni di metalli pesanti da suoli inquinati.
In conclusione, i risultati inerenti i meccanismi molecolari sulla risposta delle radici di specie arboree perenni allo stress meccanico e i dati ottenuti sui batteri resistenti ai metalli pesanti contribuiranno ad ampliare le conoscenze sull’ uso delle specie vegetali per la mitigazione dei cambiamenti ambientali.In the recent years, the issues of environmental changes received a well-justified attention from scientists and policy makers especially because several dramatic alterations have been recorded at ecosystem and species distribution level (Aber et al., 2001; Loreau et al., 2001). According to literature, global climate changes (Walther et al., 2002) and environmental pollution (Islam et al., 2004) are widely recognized as the most important causes of environmental alterations. In fact, it has been shown that environmental contamination by pollutants induces several diseases on plants, animals and human, representing with climate change, the most important cause of species extinction (Leduc et al., 2004). Often environmental changes become, for plants “stress conditions” (i.e. drought, salinity, extreme temperatures, pollutants or mechanical stress; Boyer, 1982). To forefront adverse conditions, plants have developed different adaptive strategies (Boyer, 1982; Nilsen and Orcutt et al., 1996; Borics et al., 2013) that include morphological, physiological, biochemical and molecular adjustments. Mechanisms that allow plants to withstand environmental stress has become an interesting field of scientific research. In fact, understanding how plants respond to stress conditions could be useful not only for plant biology advances, but also for improving the efficiency of strategies based on the use of plants for environmental changes mitigation (Mbow et al., 2014). This thesis presents a PhD research that focalized the attention on the molecular mechanism that allow woody perennial plants to forefront environmental changes, with a particular focus on mechanical and heavy metal stress. The first part of this thesis provides new insight about the complex and almost unknown molecular mechanisms regulating woody root responses to mechanical stress, that represents a really common environmental perturbation that considerably affect plant stability. By using a simple experimental system, a controlled simulation of mechanical stimuli was performed in Populus nigra roots. After analyzing the proteomic alteration and the involvement of auxin in poplar woody root subjected to bending stress, the attention was focalized on the role of miRNAs (microRNA) in regulating mechanical stress responses. By using a reverse transcription-quantitative PCR (RT-qPCR) approach, the study evaluated the expression level of five mechanically-induced miRNAs (ptc-miR162, ptc-miR164, ptc-miR172, ptc-miR408, ptc-miR473), previously identified in bent poplar stem by Lu et al., (2005). Moreover, the study provides the analysis of miRNAs cis-regulatory promoter elements and the computationally and experimentally prediction of miRNA target genes. A highly complex miRNAs expression pattern was recorded in poplars roots subjected to bending stress, showing that their expression is not only regulated by tension and compression forces (Trupiano et al., 2012 a, b), but also by other important process related to bending stress responses such as lateral root formation and lignin deposition. Since “rhizoremediation” represents a great challenge to phytoremediation purpose (Glick, 2003). Last part of the studies carried out in this thesis, were focused on plant-microbes interactions to remove heavy metal in polluted sites. Preliminary results are reported in this thesis where a strain belonging to Bacillus genus was isolated from a lead (Pb) and arsenic (As) polluted soil. This isolated strain showed the great capability to tolerate Pb and As exposure, and can be further used in association with several plants species for rhizoremediation purposes. In conclusion, results on molecular mechanisms involved in root response to mechanical stress, and the data on heavy metal bacteria strains although preliminar, provided by this thesis, contribute to widen the knowledge on the use of plants for environmental changes mitigation.
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Guillaud, Lucile M. (Lucile Marie). "Probability of derailment under earthquake conditions." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38236.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.Includes bibliographical references (leaves 141-144).
A quantitative assessment of the probability of derailment under earthquake conditions is presented. Two derailment modes are considered: by vibratory motion - during the ground motion - and by permanent track deformation - after the motion ended. Criteria for derailment that apply to both modes are derived in terms of peak transversal acceleration and peak transversal displacement. This allows a direct comparison between the two causes of derailment. We find that the first mode of derailment (by vibratory motion) dominates over the second mode (by track damage). The model considers the effect of spatial non-homogeneities in soil and structural characteristic and the incoherence of the ground motion into the assessment of derailment risk. The lateral motion experienced by the train under non-synchronous vibration of the track is obtained as the superposition of two contributions: one is the track motion at a fixed location and the other is the motion as the train travels on deformed tracks. Under linear elastic conditions, a method to obtain the power spectral density function for ground acceleration is presented and used to obtain acceleration and displacement response spectra.
(cont.) The second component of motion depends on speed. It is found that the train motion due to track deformation has small effects at ordinary speeds but that it becomes noticeable as the speed increases and the support spacing decreases. In general, it is shown that changes in soil and structural properties present a higher risk for derailment by vibratory motion. In some cases, the second component of train motion may increase the acceleration due to track motion at a single location by a factor of two. The analysis is first done assuming linear behavior of the soil and structure and then nonlinearities and permanent deformations are included. The elastic analysis is found to be adequate, except for structures with natural periods exceeding 1 second where the elastic analysis yields conservative estimates in comparison with the inelastic case.
by Lucile M. Guillaud.
S.M.
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Lin, Yatang. "Essays on environmental and urban economics." Thesis, London School of Economics and Political Science (University of London), 2017. http://etheses.lse.ac.uk/3560/.
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The thesis consists of three independent chapters on environmental and urban economics. A central theme explored in this thesis is what determines the distribution of economic activities across space. My exploration in this direction begins with the roles of industrial pollution and transportation infrastructure in shaping the spatial distribution of skills, and extends to evaluate the spatial allocation efficiency of renewable energy projects. The first chapter,“The Long Shadow of Industrial Pollution: Environmental Amenities and the Distribution of Skills”, investigates the role of industrial pollution in determining the competitiveness of post-industrial cities, with a focus on their ability to attract skilled workers and shift to a modern service economy. I assemble a rich database at a fine spatial resolution, which allows me to track pollution from the 1970s to the present and to examine its impacts on a whole range of outcomes related to productivity and amenity, including house prices, employment, wages, and crime. I find that census tracts downwind of highly polluted 1970s industrial sites are associated with lower housing prices and a smaller share of skilled employment three decades later, a pattern which became evermore prominent between 1980 and 2000. These findings indicate that pollution in the 1970s affected the ability of parts of cities to attract skills, which in turn drove the process of agglomeration based on modern services. To quantify the contribution of different mechanisms, I build and estimate a multi-sector spatial equilibrium framework that introduces heterogeneity in local productivity and workers’ valuation of local amenities across sectors and allows the initial sorting to be magnified by production and residential externalities. Structural estimation suggests that historical pollution is associated with lower current productivity and amenity; the magnitudes are higher for productivity, more skilled sectors and central tracts. I then use the framework to evaluate the impact of counterfactual pollution cuts in different parts of cities on nationwide welfare and cross-city skill distribution. The second chapter, “Travel Costs and Urban Specialization: Evidence from China’s High Speed Railway” examines how improvements in passenger transportation affect the spatial distribution of skills, exploiting the expansion of high speed railway (HSR) project in China. This natural experiment is unique because as a passenger-dedicated transportation device that aims at improving the speed and convenience of intercity travel, HSR mostly affects urban specialization through encouraging more frequent intercity trips and face-to-face interactions. I find that an HSR connection increases city-wide passenger flows by 10% and employment by 7%. To further deal with the issues of endogenous railway placement and simultaneous public investments accompanying HSR connections, I examine the impact of a city’s market access changes purely driven by the HSR connection of other cities. The estimates suggest that HSR-induced expansion in market access increases urban employment with an elasticity between 2 and 2.5. The differential impacts of HSR on employment across sectors suggest that industries benefiting more from enhanced market access are the ones intensive in nonroutine cognitive skills, such as finance, IT and business services. These findings highlight the role of improved passenger travel infrastructure in promoting the delivery of services, facilitating labour sourcing and knowledge exchange across cities, and ultimately shifting the specialization pattern of connected cities towards skilled and communication intensive sectors. In the last chapter, “Where does the Wind Blow? Green Preferences and Spatial Misallocation in the Renewable Energy Sector” , I focus on the spatial allocation efficiency of renewable energy projects. How efficiently are renewable energy projects distributed across the US? Are “greener” investors worse at picking sites? Using extensive information on wind resources, transmission, electricity prices and other restrictions that are relevant to the siting choices of wind farms, I calculate the predicted profitability of wind power projects for all possible locations across the contiguous US, use this distribution of this profitability as a counterfactual for profit-maximizing wind power investments and compare it to the actual placement of wind farms. The average predicted profit of wind projects would have risen by 47.1% had the 1770 current projects in the continental US been moved to the best 1770 sites. I also show that 80% and 42% respectively of this observed deviation can be accounted for by within-state and within-county distortions. I provide further evidence that a large proportion of the observed within-state spatial misallocation is related to green investors’ tendency of invest locally and sub-optimally. Wind farms in more environmentally-friendly counties are more likely to be financed by local and non-profit investors, are closer to cities, are much less responsive to local fundamentals and have worse performance ex-post. The implementation of state policies such as Renewable Portfolio Standard (RPS) and price-based subsidies are related to better within-state locational choices through attracting more for-profit investments to the “brown" counties, while lump-sum subsidies have the opposite or no effects. My findings have salient implications for environmental and energy policy. Policy makers should take account of the non-monetary incentives of renewable investors when determining the allocative efficiency of policies.
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Jiang, Ping. "Mercury Sulfide Dissolution in Environmental Conditions: Thermodynamic and Kinetic Approaches." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/3027.
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Mercury (Hg) is a global contaminant of ecosystems and human health risk, with complicated biogeochemical processes. Mercury sulfide (HgS) dissolution has been suggested as a key process in Hg cycling, as it could potentially increase the pool of inorganic Hg (iHg) for the production of methylmercury (MeHg). Despite previous sporadic observations of enhanced HgS dissolution under certain conditions, much remains unclear on mechanisms of HgS dissolution. The objective of my research was to advance the mechanistic understanding of HgS dissolution, concerning re-adsorption of released Hg, effects of thiol-ligands, and Hg speciation.
Considering the lack of feasible techniques to differentiate dissolution and re-adsorption processes, I first developed an efficient method using isotope tracer and isotope dilution techniques to investigate the re-adsorption of released Hg during HgS dissolution. The HgS dissolution rate with consideration of re-adsorption was two times the rate calculated from detecting Hg alone in the presence of O2, indicating the importance of Hg re-adsorption during HgS dissolution. I further examined the role of Hg-ligand complexation in HgS dissolution and Hg(II) re-adsorption using a thermodynamic adsorption method, selecting L-cysteine (Cys) as a model compound for low molecular weight ligands and Waskish fulvic acid (FA) for natural dissolved organic matter (DOM). My results suggest that the presence of Cys enhanced HgS dissolution through the decreased re-adsorption of Hg-Cys complex, whereas Waskish FA inhibited HgS dissolution, possibly because of the adsorption of FA on HgS surface that covered dissolution sites.
I further employed a geochemical modeling method to study Hg speciation and the relation of iHg speciation to MeHg, aiming to provide a methodological example for potentially evaluating the implications of Hg species distribution during HgS dissolution on MeHg production. I applied geochemical model PHREEQC to the Florida Everglades, a well-studied wetland with model input parameters available, to determine the distribution of iHg in surface water at different sites. The modeling results suggest that sulfide and DOM govern iHg speciation, and the Hg-sulfide and Hg-DOM species are related to MeHg in environmental media but not fish, suggesting the importance of iHg speciation in MeHg production and the complexity of Hg bioaccumulation.
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Agard, John Vincent. "Dependence of continental severe convective instability on climatological environmental conditions." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/113799.
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Thesis: Ph. D. in Atmospheric Science, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 115-119).
Most of Earth's strongest atmospheric convection occurs over the continents, where potential energy is stored over time in metastable vertical profiles, only to be released rapidly by severe storms. In contrast to equilibrium-state convection in tropical ocean regions, there is a relative paucity of research exploring the climate dynamics of continental deep convection. This work makes a contribution to rectifying that deficiency by exploring the physical mechanisms by which convective available potential energy (CAPE) is generated, and their dependence on climatological properties of the Earth's environment. First, a budget of the time tendency of CAPE is used to examine the buildup of CAPE in advance of severe convective storm events in North America via case studies using reanalysis data. Contributions to extreme peak CAPE from relative advection of air masses, diabatic heating of the surface boundary layer, and radiative cooling of the free troposphere are computed. In all 8 cases studied, CAPE buildup is found to be driven primarily by fluxes of heat and moisture from the surface into the boundary layer on sub-diurnal time scales, and not by radiative cooling or the relative advection of air masses at low and upper levels over multiple days. This result is then further explored using an idealized two-dimensional continental framework using a minimal numerical model. Experiments in both 2-column and 40- column configurations demonstrate a link between discontinuities in surface moisture and high levels of transient CAPE. Surface entropy flux is once again found to be the primary driver of peak CAPE buildup within the model. Finally, a thermodynamic constraint on CAPE in continental environments is established using an idealized, one-dimensional model. This theoretical model incorporates the physical principle of CAPE generation identified using reanalysis and two-dimensional modeling by considering a dry adiabatic column that comes into contact with a moist land surface. A system of equations is derived to describe the evolution of the ensuing surface boundary layer. From these, the maximum value of transient CAPE in the column can be found for any particular combination of surface temperature and moisture. It is demonstrated that, for a given range of surface temperatures, the value of peak CAPE scales with the Clausius-Clapeyron relation.
by John Vincent Agard.
Ph. D. in Atmospheric Science
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Maidment, Graeme G. "Optimisation of environmental conditions for unwrapped chilled foods on display." Thesis, London South Bank University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274293.
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Cross, Elizabeth. "On structural health monitoring in changing environmental and operational conditions." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2673/.
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Structural Health Monitoring (SHM) is the monitoring of any type of structure for the express purpose of determining its condition and future lifespan and if, when and where any reparative action is needed. A focus of the work in this thesis is SHM for long-span bridges and particularly the effects of environmental and operational conditions on a monitoring campaign. There is currently a trend for heavily instrumenting civil structures with large sensor networks that continually collect terabytes of data. However, these large data sets are often redundantly stored and not used for anything. One of the principal aims in the thesis is to exploit such monitoring data for the development of diagnostic tools for structural condition assessment. The first part of the thesis concerns formulating a baseline for the Tamar Bridge that represents the normal undamaged condition of the structure. To do this a large amount of analysis was needed in order to understand how different structural measurements are interrelated and how the bridge responds to normal environmental and operational conditions. Particular attention was paid to measurements that can be sensitive to structural degradation (such as modal properties). Often simple causal relationships were found between monitored variables, and response surface models were formulated that could predict selected variables with good accuracy given measurement of operational and environmental conditions, such as air temperature, traffic loading and wind profile. The predictive models developed are intended to be used as diagnostic tools, for example, a departure from the normal condition of the bridge will bring about a significant increase in prediction error, which may be monitored as a system alarm. The second part of the thesis directly concerns how the influence of environmental and operational variation on features sensitive to damage can be lessened or removed without measurement of these conditions themselves. This is a very important issue in SHM, as often the effects of fluctuating environmental and operational conditions can mask any indication of damage to a structure that may be evident in structural response. In the thesis a solution to the problem based on the econometric theory of cointegration is introduced. Application of this theory is found to be ideally suited to remove unwanted environmental and operational trends from SHM data, and forms an exceedingly promising contribution to the development of SHM technology.
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RAMEY, TONYA LEE. "BDELLOID ROTIFERS: ENVIRONMENTAL CONDITIONS IMPORTANT FOR SURVIVAL AT SUBZERO TEMPERATURES." Thesis, The University of Arizona, 2008. http://hdl.handle.net/10150/192205.
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SCANAVINO, MATTEO. "Design and testing methodologies for UAVs under extreme environmental conditions." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2898032.
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Sridharan, Srinivasan. "Environmental durability of E-glass/vinylester composites in hot-moist conditions." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/10144.
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Laing, Timothy. "Assessing the impact of institutional conditions upon REDD+." Thesis, London School of Economics and Political Science (University of London), 2014. http://etheses.lse.ac.uk/1024/.
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This thesis investigates the role that institutional conditions have on policy for Reducing Emissions from Deforestation and Forest Degradation (REDD+) by applying a New Institutional Economics perspective and a multimethodological approach. It focuses on three specific institutional conditions: property rights, governance and politics, and applies theoretical and empirical techniques. A single case study of Guyana’s innovative REDD+ programme is used for empirical analysis. The thesis provides contributions to normative and evaluative REDD+ literature, especially with regard to early assessments of the design, impacts and effectiveness of national-level REDD+. It makes subsidiary contributions in the areas of small-scale mining, policy design under political influence and environmental governance. Through analytical modelling the thesis finds that design of REDD+ is significantly altered when placed in a general equilibrium setting, along with when political influence is included. Econometric analysis of a unique data-set from Guyana shows effects from electoral cycles on the holding of property rights relating to the main driver of deforestation, mining, along with the introduction of REDD+. Qualitative analysis of interviews and media sources highlight that governance of REDD+ in Guyana has remained predominantly state-centric, with only some evidence that multi-actor, multilevel governance has emerged. Issues such as capacity, political will, electioneering, the retained control of finance by donors and the introduction of complicated systems of safeguards have all affected the emergence of ‘pure’ REDD+ in Guyana. The thesis provides key conclusions on the importance of a cognisance of the institutional landscape on which REDD+ is to be implemented. Including such an institutional perspective raises questions over the perceived cheapness of REDD+ as a mitigation option. It offers guidance for the design and implementation of national level REDD+ policy and highlights the need for a differentiated approach to REDD+, factoring in the relevant institutional conditions prevalent in each jurisdiction.
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Ali, Sani Muhammad. "Measured and perceived conditions of indoor environmental qualities (IEQ) of university learning environments in semi-arid tropics." Thesis, University of Portsmouth, 2018. https://researchportal.port.ac.uk/portal/en/theses/measured-and-perceived-conditions-of-indoor-environmental-qualities-ieq-of-university-learning-environments-in-semiarid-tropics(b611ff99-e930-42bc-b254-36d29cf6de97).html.
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This study investigates the conditions and the levels of satisfaction with indoor environmental quality (IEQ) in naturally ventilated (NV) learning environments in Bayero University, Kano and compares the results to international comfort standards' thresholds. It examines the thermal and visual comfort, acoustic quality as well as the indoor air quality of six learning environments in the University consisting of four lecture theatres and two laboratories. Researches in IEQ have shown that good quality indoor environment enhances occupants' comfort, wellbeing, raises their productivity, and most importantly for this research, it raises students' performances, reduces absenteeism, and reduces stress and fatigue among teachers. IEQ researches are mostly being undertaken in the four most advanced continents that are situated in the temperate regions of the world, but not in sub-Saharan Africa. Using both measurement and survey methods, internal and external physical parameters (air and radiant temperatures, air velocity, relative humidity, background noise, sound pressure level, horizontal and vertical illumination level, carbon dioxide concentration and particulate matter) were evaluated. The assessments were undertaken three times covering ten months, August 2016 to May 2017, which coincided with the three distinct seasons (warm and wet; cool and dry & hot and dry) in Kano. PMV model, as always, failed to predict the thermal conditions of the learning environments. Similarly some of the measured and calculated IEQ parameters, have not met the thresholds specified by the adaptive components of ASHRAE-55, but were in agreement with EN 15251, the respondents expressed their acceptance of their learning environments, subjectively. This is not surprising as these standards were often based on experiments implemented in developed countries, where the severity of the climatic conditions and the culture are dissimilar to sub Saharan Africa. The outcome of the research is hoped to raise awareness of IEQ potentialities among the academia, building industry professionals, building owners, university managers and other education policy makers in the region.
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Klein, Shannon. "Responses of Jellyfish to Environmental Change." Thesis, Griffith University, 2016. http://hdl.handle.net/10072/367711.
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Worldwide, marine ecosystems are being impacted by a suite of anthropogenic stressors. Jellyfish are distributed worldwide and often proliferate rapidly to form conspicuous and problematic blooms. Jellyfish are considered robust to a range of environmental stressors and, as a consequence, there is concern among researchers that changing environmental conditions could facilitate jellyfish populations. There is, however, a paucity of robust evidence to support these claims because few manipulative experiments have been done to establish causative mechanisms that may allow jellyfish to proliferate under environmental stress. The overall aim of this thesis was to use manipulative experiments to test hypotheses about the influence of local, regional and global scale stressors on jellyfish.
To assess the potential interactive effects of environmental stressors that occur episodically and on a local scale, I investigated the potential interactive effects of reduced salinity and a photosystem II herbicide (atrazine) on symbiotic medusae of Cassiopea sp. during a simulated rainfall event (Chapter 2). Medusae exposed to reduced salinity and high concentrations of atrazine individually exhibited negative effects. Medusae survived and recovered from conditions that mimicked mild and moderate rainfall events, but exposure to conditions that mimicked a heavy rainfall event (i.e. reduced salinity and high concentrations of atrazine in combination) caused medusae to die. These findings suggest that although symbiotic medusae can tolerate mild and moderate rainfall events, medusae may not survive heavy rainfall events that typically expose biota to high levels of herbicide runoff and reduced salinity.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Eisenbarth, Sabrina. "Essays on international trade, environmental regulation and resource management." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35736/.
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Chen, Ying. "Essays on urban and environmental economics in developing countries." Thesis, London School of Economics and Political Science (University of London), 2018. http://etheses.lse.ac.uk/3817/.
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My thesis is comprised of essays that study urban and environmental economic topics in developing countries. Three of the four essays study causal drivers behind the phenomenal urbanization and local economic growth in China. Its rapid growth in the recent decades provides an illustrative case for understanding how the spatial distribution of economic activities is affected by policies regulating factors of production. The fourth essay extends to another developing country, Tanzania, where the challenges posed by climate change faced by populations agglomerating in fast growing urban centers are substantial. This thesis strives to contribute to current research with my understanding of the contexts, utilization of new yet publicly available data, and novel methodology. The fist chapter, Political favoritism in China's capital markets and its effect on city sizes, examines political favoritism of cities and the effect of that favoritism on city sizes. To study favoritism we focus on capital markets, where defining favoritism is more clear-cut and not confounded with issues of city scale economies. Efficiency in capital markets requires equalized marginal returns to capital across cities, regardless of size. We estimate the city-by-city variation in the prices of capital across cities in China from 1998 to 2007. It shows how the prices facing the highest order political units and overall cross-city price dispersion change with changes in national policy and leadership. Next, the effect of capital market favoritism on city growth after the national relaxation of migration restrictions in the early 2000's is investigated. We develop a simple model to show that those cities facing a lower price of capital respond with larger population increases over the next decade, with the change labor mobility. The elasticity of the city growth rate with respect to the price of capital is estimated to be - 0.07 in the OLS approach and -0.12 in the IV approach. The second chapter, Early Chinese development zones: fist-mover advantage and persistency, studies the heterogeneous effects of China's special economic zone program by their level of government support and timing of designation. Using a difference-in-differences (DID) approach, I observe that the early national development zones in China have substantially greater and persistent success in attracting FDI compared to national zones established later, or those at the provincial level. Early national zones persistently attract higher levels of FDI inflows, attract more internal migration and are of significantly larger city sizes. To investigate whether the persistent success of early national zones is driven by their first-mover advantage or their unobservable high growth potential, I use their stronger ties to overseas Chinese investors in past waves of political instability as instrumental variable. The IV estimates are comparable to DID, suggesting the success of early national zones relative to newer and provincial zones can be attributed to their first-mover advantage. This conclusion also suggest that the large positive impacts found in China in the existing literature of evaluating place-based policies can potentially be driven by a small group of first-movers. In the third chapter, Air pollution, regulations, and labor mobility in China, I study the local economic impacts of pollution regulation in China at the time when migration costs fall. On the one hand, environmental regulations impose costs on firms, which tend to reduce local employment. On the other hand, lower pollution levels are an appealing amenity that attracts human capital to the region, possibly providing a boost to economic activity. The overall net effect of these two opposing forces is ambiguous. To investigate this, I study how local economies in China between 2000 and 2010 are affected by two significant reforms in environmental regulations and internal migration. Following the environmental reform, Chinese prefectures face new national air quality standards whose enforcement intensity can be proxied by their existing air quality at the time of the policy introduction. Meanwhile, the migration reform reduces migration costs and allows workers to relocate based on their preferences for air quality across prefectures. To formalize how air quality regulation affects local employment and city sizes by skill types following the two reforms, I first develop a spatial equilibrium model to guide the empirical analysis. To address the non-random spatial distribution of local air quality, I construct a novel instrumental variable of power plant suitability to capture a prefecture's likelihood to pollute heavily. Thermal power plants are major contributors to China's emissions, while electricity distribution and pricing are centralized. Therefore, locations with comparable economic characteristics may differ substantially in their air pollution levels simply because that some host thermal power plants and some do not. The estimation results show that air pollution regulations have an overall adverse impact on local manufacturing employment, with modest reallocation from heavy to non-polluting industries locally. There is little reallocation across space of low-skilled workers, whose employment prospects are more vulnerable under pollution regulation. However, the population of high-skilled workers in heavily polluted prefectures declines, showing their strong preference for air quality as migration costs fall. The last chapter, Cholera in times of floods: weather shocks and health in Dares Salaam, takes a slightly different perspective on urban and environmental issues in developing countries. We examine the challenges faced by urban population in Tanzania as the result of growing urban density and increasing extreme weather occurrences. Urban residents in developing countries have become more vulnerable to health shocks due to poor sanitation and infrastructure. This paper is the first to empirically measure the relationship between weather and health shocks in the urban context of a developing country. Using unique high-frequency datasets of weekly cholera cases and accumulated precipitation for wards in Dar es Salaam, we find robust evidence that extreme rainfall has a significant positive impact on weekly cholera incidences. The effect is larger in wards that are more prone to flooding, have higher shares of informal housing and unpaved roads. We identify limited spatial spillovers. Time-dynamic effects suggest cumulated rainfall increases cholera occurrence immediately and with a lag of up to 5 weeks.
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Watts, Dexter Brown. "Mineralization in soils amended with manure as affected by environmental conditions." Auburn, Ala. :, 2007. http://repo.lib.auburn.edu/2007%20Spring%20Dissertations/WATTS_DEXTER_20.pdf.
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Libertinova, Jitka. "Vent mussel shells as indicators of environmental conditions at hydrothermal vents." Thesis, Bangor University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520066.
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Stoodley, Jannine. "Saltmarsh sediments as indicators of changing environmental conditions : Thames Estuary, U.K." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394483.
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Nachmany, Michal. "The micro-dynamics of environmental policy diffusion : conditions, motivations, and mechanisms." Thesis, London School of Economics and Political Science (University of London), 2016. http://etheses.lse.ac.uk/3466/.
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This thesis contributes to the scholarship on policy diffusion in general, and on environmental policy diffusion in particular, by unpicking the drivers of different diffusion mechanisms. Its overarching aim is to investigate the motivational dynamics influencing environmental policymaking at the fuzzy, understudied, pre-legislative stage. The thesis comprises four standalone papers: The first paper (Chapter 2) examines policymakers’ motivations to engage with the climate change mitigation agenda based on a case study of Israeli climate change mitigation policy. It suggests that Israel’s engagement with the climate change mitigation agenda, displaying an evident pattern of diffusion by emulating developed countries, is significantly motivated by considerations of internal, rather than external, legitimacy, contrary to expectations. The second paper (Chapter 3) makes theoretical advancements in recognising issue attributes as explanatory factors for the different mechanisms of policy diffusion, addressing an acknowledged gap in the literature. The third paper (Chapter 4) is an empirical application of the issue attributes model introduced in Chapter 3; the concept is applied to three diffusion processes of environmental issues in Israel: climate change, air pollution, and waste, analysing the differences in the attributes of these three issues, and subsequently, the differences in diffusion mechanisms in practice. The fourth paper (Chapter 5) investigates GLOBE International, a previously unstudied network of legislators committed to advancing climate change legislation. Its main findings show that GLOBE facilitates a mechanism of policy and political learning, but perhaps more interestingly, generates network-enabled emotional energy and esprit de corps among its members, which has helped to motivate and sustain climate action by legislators. The thesis takes a qualitative, microlevel approach, utilising data from 64 interviews with policy actors from 21 countries, as well supporting textual sources, thus contributing to the qualitative knowledge base needed to support analytical aggregations on policy diffusion processes.
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Higuchi, Hirokazu. "Environmental Physiology of Cherimoya(Annona cherimola Mill.)under Heat Stress Conditions." Kyoto University, 1999. http://hdl.handle.net/2433/78092.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第7587号
農博第1026号
新制||農||773(附属図書館)
学位論文||H11||N3222(農学部図書室)
UT51-99-D204
京都大学大学院農学研究科熱帯農学専攻
(主査)教授 櫻谷 哲夫, 教授 杉浦 明, 教授 三野 徹
学位規則第4条第1項該当
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Blšáková, Daniela. "The impact of environmental conditions on young entrepreneurs' start-up activities." Master's thesis, Vysoká škola ekonomická v Praze, 2017. http://www.nusl.cz/ntk/nusl-359257.
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The diploma thesis deals with the influences that affect young people aged 18 to 24 in the establishment of start-ups. The main aim was to find out which environmental factors influence emergence of youth start-ups and how they differ in Europe, China and the US over time. The thesis describes three models that explain the entrepreneurial intentions and that serve better understanding of human behavior in setting up businesses. Further the thesis includes a description of the individual and environmental factors that are based on current studies. Due to the title of thesis only the impact of environmental factors was tested. The analysis was conducted on a public data of the Global Entrepreneurship Monitor.
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Johnson, David Wayne. "Stress productivity in alfalfa: Selection under saline and nonsaline environmental conditions." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185176.
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Alfalfa (Medicago sativa L.) forage yield may be reduced by moderate levels of salinity. Increasing forage yield in saline environments through plant breeding could ameliorate this problem. Selection for increased salt tolerance in alfalfa in cell culture, at germination, or during seedling growth with high NaCl levels has not resulted in agronomically relevant levels of salt tolerance. Different selection schemes were examined to identify alfalfa plants with the ability to germinate, establish, and regrow at salinity levels common in agricultural areas. Data from 'Sonora' and its parental ecotype African grown in a greenhouse and irrigated with 0, 30, 60, or 80 mM NaCl were used to simulate selection for increased forage yield in each NaCl environment through five harvests. Predicted gains in forage yield were highest in non-saline conditions and gains decreased as the NaCl level increased in the selection environment. Selection based on plant yield from regrowth harvests was predicted to be more efficient than that based on seedling harvest. Genetic and phenotypic relationships between plant performance at seed germination, seedling development, and post-harvest regrowth at 0 or 80 mM NaCl were also determined. The effect of NaCl on forage yield of alfalfa regenerated from non-saline callus cultures was examined. This research showed that selection for increased forage yield can be made at moderate NaCl levels in germplasm with ample variation for yield when grown in saline environments. Selection for increased forage yield in non-saline conditions may eliminate potentially salt tolerant plants from a population. Selection for increased alfalfa forage yield in saline environments at early stages of development is not necessarily optimum. Selection methods that include each critical growth stage may be required to develop alfalfa cultivars with increased forage yield in saline environments. (Abstract shortened with permission of author.)
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Manheim, Derek C. "Improved Microalgal Biomass Harvesting Using Optimized Environmental Conditions and Bacterial Bioflocculants." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/848.
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ABSTRACT
IMPROVED MICROALGAL BIOMASS HARVESTING USING OPTIMIZED ENVIRONMENTAL CONDITIONS AND BACTERIAL BIOFLOCCULANTS
DEREK CONTE MANHEIM
The cost and energy balance of microalgae biofuel production is sensitive to the algae harvesting method, among many other factors. Bioflocculation and settling of suspended microalgae cultures is a harvesting method with potentially low cost and energy input. However, bioflocculation (the spontaneous flocculation of algal cells without chemical addition) has not been a reliable process with cultures grown in ponds. To provide insights to help improve algae settling, factors affecting the settling of algae were investigated in the laboratory using pure cultures of two common microalgae species: Scenedesmus sp. and Chlorella vulgaris. Bioflocculation of these algae was studied with and without the addition of bioflocculants produced by the bacterium, Burkholderia cepacia, to improve settling efficiencies. The bioflocculant produced by this bacterium was used in two different forms: a cell suspension including capsular and dissolved extracellular polymeric substance (EPS) components of B. cepacia, and dialyzed filtrate of the bacterial culture (only dissolved EPS fraction). The effects of algal growth phase, mixing time, bioflocculant dose, and environmental conditions such as pH and nutrient deprivation of bacterial bioflocculant cultures on settling of the algae species were studied.
Settling characteristics were different for the two algae cultures, and their settling was affected differently by the many factors studied. Scenedesmus settling was best in later growth stages, while Chlorella settled much better in early growth phases. Addition of B. cepacia cells as a bioflocculant improved settling of Scenedesmus, with the greatest effect during mid to late exponential growth of the Scenedesmus. In contrast, addition of B. cepacia filtrate as a bioflocculant best improved Chlorella settling during stationary growth of Chlorella. Longer mixing times (contact time between the algae cells and bacterial bioflocculant) improved the settling of Scenedesmus, while Chlorella settled better with a shorter mixing time. Reducing the pH to 3 (a typical isoelectric point for microalgae) improved the settling of both algae cultures, with and without bioflocculant addition. Increasing the pH to 11 autoflocculated Scenedesmus cultures, but not Chlorella cultures, at early growth stages.
EPS produced by the algae, bacteria, and wastewater organisms was quantified using dialysis separation followed by total organic carbon (TOC) analysis. Wastewater organisms were included because wastewater is a potential growth medium for biofuel algae. Improved settling of both species of algae depended on both the quantity and type of EPS (dissolved or capsular) produced by both the bacterial bioflocculant, and the algae themselves. Scenedesmus settled the best during late growth phases while its own EPS production was high, and combined EPS (capsular and dissolved) from B. cepacia improved settling at a higher dosage of bacterial cells to algae (1:2 B. cepacia cells to algae cells). Since Chlorella settling was not improved at later growth stages when its own EPS production was greatest, it appears that Chlorella’s settling rate was less affected by the production of its own EPS. For Chlorella, B. cepacia EPS addition (capsular and dissolved) was effective only in low doses (1:6 B. cepacia cells to algae cells).
Settling results with the addition of bacterial bioflocculants with the pure algae cultures were compared to settling results of lab experiments with algae pondwater sampled from high-rate algae ponds (HRAPs). These algae samples were used to test the addition of return activated sludge (RAS) to improve settling. RAS addition improved the settling of Chlorella, which was the dominant algae species in the HRAP during the time of this study, at two different doses (a ratio of RAS to algae pond water of 1:3 and 1:6).
Nutrient deprivation of B. cepacia cells before use as a bioflucculant was found to improve settling for Scenedesmus, especially during early phases of growth when EPS production of Scenedesmus was low. The EPS produced by the starved bacterial cells was about 30% greater than that produced by cultures which were not nutrient-limited. For the bacterial cultures, EPS production peaked at mid stationary phase for non-starved cultures and during early stationary phase for starved cultures. Chlorella settling improved in early growth with starved bacterial cell addition and in later growth with non-starved bacterial cell addition.
These results suggest that the settling of microalgae can vary dramatically by species and that the settling of different species is affected differently by growth phase and environmental conditions. In addition, species of algae respond differently to addition of bacterial bioflocculants. Given the dramatically different settling behavior of the two species of algae used in this research, more research should be directed to studying settling of other microalgal species. Based on this research, the use of bacterial bioflocculants is promising for improving algae settling and may contribute to the development of a reliable, low cost harvesting process for commercial biofuel production from microalgae.
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Basu, Shreejita. "Bioremediation of BTEX polluted soil water systems under varying environmental conditions." Thesis, IIT Delhi, 2016. http://eprint.iitd.ac.in:80//handle/2074/8194.
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Hardbarger, Ashley N. "Viability of Methicillin-Resistant Staphylococcus aureus on Artificial Turf Under Outdoor and Laboratory Environmental Conditions." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1338581271.
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