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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Structure et dynamique de la communauté bactérienne libre et attachée dans les écosystèmes lacustres

Parveen, Bushra 25 January 2012 (has links)
C'est essentiellement sur les bactéries libres que portent les études récentes en écologie microbienne d'eau douce, et seulement quelques études ont concerné les communautés bactériennes attachées. Dans cette étude basée sur l'analyse des séquences du gène 16SARNr, la diversité des communautés bactériennes attachées ainsi que de la fraction libre a été étudiée sur deux systèmes d'eau douce ; un lac mésotrophe (le lac du Bourget) et un lac hypereutrophe (le lac Villerest). La diversité des Actinobacteria, Betaproteobacteria et Verrucomicrobia libres et attachées a été étudié en relation avec les variables environnementales, dans le lac du Bourget pendant deux périodes à dominances contrastées de phytoplancton. L'analyse des résultats a montré une différence au niveau phylogénétique entre les communautés bactériennes attachées et libres des trois groupes de bactéries étudiées. Le clade betaI, dominait les Betaproteobacteria des fractions libres et attachées, avec 57,8% de la totalité des unités taxinomiques opérationnelles (OTUs). Pour les Actinobacteria, le groupe d'acIV a été détecté comme le plus abondant, suivi par acI avec respectivement 45% et 25% du total des OTUs. De même, les groupes Verrucomicrobia d'eau douce, à savoir CREPA29, FukuN18, CL120-10 sont apparus comme les plus importants, avec 22,3%, 16,15% et 14,61% des OTUs respectivement. Cette étude a permis de définir 15 nouveaux clades putatifs représentant la diversité bactérienne d'eau douce des Betaproteobacteria (lbI-lbVIII), Actinobacteria (acLBI) et Verrucomicrobia (CRE-PA29, FukuS27, BourFI-BourFIV). Par ailleurs, 12 groupes représentant la diversité de phylogénétique des Betaproteobacteria, Actinobacteria et Verrucomicrobia contiennent exclusivement des OTUs de la fraction attachée. La dynamique saisonnière souligne les changements des phylotypes bactériens distincts pour les deux communautés attaché et libre. Les Actinobacteria dans la fraction attachée était associée avec la biomasse des Chrysophyceae et N-NO3, et les Betaproteobacteria avec la biomasse de Chlorophyceae et de la richesse du phytoplancton tandis que les Verrucomicrobia de cette même fraction ont semblé être principalement influencés par la richesse du phytoplancton, l′abondance des rotifères et les nutriments inorganiques (N-NO3, SiO2). D'autre part, dans les communautés libres, peu de clades d'actinobacterie dépendent des nutriments ou du phytoplancton, alors que les Betaproteobacteria et Verrucomicrobia ont été principalement associés avec les paramètres biologiques (i.e. phytoplancton et copépodes). Pendant le bloom des cyanobacteries (Microcystis sp.) dans le lac Villerest, les Betaproteobacteria, Gammaproteobacteria, Alphaproteobacteria, Bacteroidetes et Actinobacteria ont été détectés comme taxa dominants dans les banques de clones du gène 16S ARNr. Toutefois Verrucomicrobia et Deinococcus-Thermus sont apparus relativement moins abondants dans les deux fractions, tandis que,Gemmatimonadetes, Acidobacteria, Chloroflexi, Planctomycetes, Deltaproteobacteria, Firmicutes et Op11 sont apparus comme des phyla mineurs dans la banque de clones des communautés bactériennes attaché et libre. Les Betaproteobacteria (n=118) attachées sont apparus comme le groupe dominant, suivi par Gammaproteobacteria (n=74) et Bacteroidetes (n=52). L'analyse phylogénétique des séquences obtenues pour la banque de clone de la fraction libre a montré que la plupart des OTUs appartiennent à Betaproteobacteria (n=192), suivi par Bacteroidetes (n=132) et Actinobacteria (n=61). Tandis que les Gammaproteobacteria (n=42) et Alphaproteobacteria (n=42) sont présents dans des proportions égales dans la banque de clones du 16S ARNr libre. (...) / The free-living bacteria point of view dominates in recent research of freshwater microbial ecology, only a few studies have focused on attached bacterial communities. In present study, based on 16S rRNA gene sequences, diversity of attached and free-living bacterial community was investigated from two freshwater aquatic systems ; a mesotrophic lake Bourget and a hypereutrophic lake Villerest. The diversity of attached and free-living Actinobacteria, Betaproteobacteria and Verrucomicrobia, in relation to environmental variables was investigated from lake Bourget during two contrasting periods of phytoplankton dominance. Comparison analyses showed a phylogenetic difference between attached and free-living bacterial communities of all three studied bacterial groups. The betaI, appeared as most dominant among all clades representing phylogenetic diversity of freshwater Betaproteobacteria, for both attached and free-living fractions, contributing to 57.8% of of the total retrieved opertational taxonomic units (OTUs). For Actinobacteria, the acIV cluster was detected as dominant, followed by acI accounting for 45% and 25% of the total retrieved OTUs respectively. Similarly, freshwater Verrucomicrobia cluster namely, CRE-PA29, FukuN18, CL120-10 appeared as dominant, comprising 22.3%, 16.15% and 14.61% of the total retrieved OTUs respectively. This study allowed defining 15 new putative clades representing the freshwater bacterial divesity of Betaproteobacteria (lbI-lbVIII), Actinobacteria (acLBI) and Verrucomicrobia (CRE-PA29, FukuS27, BourFI-BourFIV). In addition, 12 clusters representing the phylogenetic diversity of Betaproteobacteria, Actinobacteria and Verrucomicrobia were exclusively comprised of OTUs from the attached fraction. The seasonal dynamics of environmental variables have been reflected as changes in distinct bacterial phylotypes for both attached and free-living communities. The attached bacterial communities of Actinobacteria showed affiliation with Chrysophyceae biomass and N-NO3, while attached Betaproteobacteria were affiliated with biomass of Chlorophyceae and phytoplankton richness. Similarly attached verrucomicrobial communities appeared to be mainly influenced by phytoplankton richness, rotifers abundances and inorganic nutrients (NNO3,SiO2). On the other hand, within free-living communities, few actinobacterial clades were found to be dependent on either nutrients or phytoplankton communities, whereas Betaproteobacteria and Verrucomicrobia were mainly associated with biological parameters (i.e. phytoplankton and copepods communities). In another study during a cyanobacterial (Microcystis sp.) bloom from lake Villerest, Betaproteobacteria, Gammaproteobacteria, Alphaproteobacteria, Bacteroidetes and Actinobacteria were detected as prevalent taxa among the 16S rRNA gene clone libraries, however, Verrucomicrobia and Deinococcus-Thermus appeared as comparatively less abundant bacterial groups in both fractions. Whereas, Gemmatimonadetes, Acidobacteria, Chloroflexi, Planctomycetes, Deltaproteobacteria, Firmicutes and Op11 were appeared as minor phyla in clone libraries of attached and free-living bacterial communities. For attached bacterial communities Betaproteobacteria (n=118) appeared as most dominant group, followed by Gammaproteobacteria (n=74) and Bacteroidetes (n=52). The phylogenetic analysis of the sequences obtained for the clone library from free-living fraction showed that most of the OTUs belonged to Betaproteobacteria (n=192) followed in decreasing order by Bacteroidetes (n=132) and Actinobacteria (n=61) whereas Gammaproteobacteria (n=42) and Alphaproteobacteria (n=42) appeared in equal proportion in free-living 16S rRNA clone libraries. (...)
32

High Resolution Scattering of He Atoms and D<sub>2</sub> Molecules from the LiF(001) Crystal Surface / Hochaufgelöste Streuung von Helium Atomen und Deuterium Molekülen an einer LiF(001) Oberfläche

Ekinci, Yasin 15 December 2003 (has links)
No description available.
33

Säugetierkundliche Freilandforschung zur Populationsbiologie des Waschbären (Procyon lotor Linnaeus, 1758) in einem naturnahen Tieflandbuchenwald im Müritz-Nationalpark (Mecklenburg-Vorpommern) / Population biology of the North American raccoon (Procyon lotor Linnaeus, 1758) in a Northern German lowland beech forest (Müritz National Park)

Michler, Frank-Uwe Fritz 12 March 2018 (has links) (PDF)
In der Dissertation werden Fragen zur Populationsbiologie des neozonalen Nordamerikanischen Waschbären (Procyon lotor) behandelt. Die knapp sechsjährigen Freilanduntersuchungen fanden im Rahmen eines umfangreichen Waschbärenforschungsprojektes (www.projekt-waschbaer.de) in einem naturnahen Tieflandbuchenwald im Müritz-Nationalpark (Mecklenburg-Vorpommern) statt. Das Nationalparkgebiet wird nachweislich seit Ende der 1970er Jahre vom Waschbären besiedelt und stellt aufgrund seines Gewässerreichtums und seiner alten Laubbaumbestände einen idealen Lebensraum für Waschbären dar. Die Dissertation schließt die populationsbiologischen Arbeiten des Gesamtprojektes ab und stellt die Ergebnisse in fünf separaten Themenschwerpunkten vor (I. Raumverhalten, II. Sozialverhalten, III. Reproduktionsbiologie, IV. Populationsstruktur, V. Populationsdynamik). Übergeordnetes Ziel der Arbeit war die Erhebung valider populationsbiologischer Daten, um eine grundlegende ökologische Charakterisierung des Waschbären unter dem Aspekt des Natur- und Artenschutzes vornehmen zu können. Dazu wurden zwischen 2006 und 2011 in einem 1.114 ha großen Fallennetz im Serrahner Teilgebiet des Nationalparks an 53 verschiedenen Fallenstandorten 145 verschiedene Waschbären (62 ♀♀, 83 ♂♂) insgesamt 489 Mal gefangen, genetisch beprobt, vermessen und individuell markiert. 51 adulte Waschbären (23 ♀♀, 28 ♂♂) und 18 Jungtiere (10 ♀♀, 8 ♂♂) wurden darüber hinaus mit einem UKW-Halsbandsender ausgestattet und im Rahmen der telemetrischen Arbeiten insgesamt 31.202 Mal geortet (≙ im Mittel 452 Lokalisationen pro Tier). Im Kernuntersuchungsgebiet wurde an 36 beköderten Standorten ein Fotofallenmonitoring durchgeführt. Bei einer Überwachungsdauer von 5.365 Fotofallennächten entstanden dabei 18.721 Aufnahmen von 183 verschiedenen Waschbären. 82 % aller Waschbärenbilder zeigten individuell markierte Individuen. Alle 145 gefangenen Waschbären wurden im Rahmen eines separaten Teilprojektes mit hochvariablen Mikrosatelliten erfolgreich genotypisiert, so dass die Verwandtschaftsverhältnisse sowie der individuelle Reproduktionserfolg der Untersuchungstiere bekannt sind. Für die Analysen zur Populationsstruktur wurden unter anderem von 120 verendet aufgefunden Waschbären (Totfunden) aus dem unmittelbaren Umfeld des Nationalparks klassische morphometrische und phänotypische Merkmale sowie die Mortalitätsursachen erfasst. / This study considers questions concerning the spatial and social behaviour, reproduction, population structure and dynamics of the alien North American raccoon (Procyon lotor) in Germany. The investigations took place within the framework of a comprehensive raccoon research project (www.projekt-waschbaer.de) over a period of nearly six years in a close-to-nature lowland beech forest in the Müritz National Park (Mecklenburg-West Pomerania). The National Park has been verifiably colonized by raccoons since the end of the 1970s, and due to its abundance of water and its old deciduous tree population it represents an ideal habitat for this mammal. Between 2006 and 2011, 145 individual raccoons (62 ♀♀ and 83 ♂♂) were captured, genetically sampled, measured and individually tagged. Sampling took place within a 1,114 hectare area of the National Park, at 53 trap sites and with 489 trappings. 51 adult raccoons (23 ♀♀, 28 ♂♂) and 18 juveniles (10 ♀♀, 8 ♂♂) were also fitted with radio collars and located a total of 31,202 times as part of the telemetric survey (=452 localisations per individual). Camera trap monitoring was carried out at 36 baited locations of the main investigation area (1,628 ha): 18,721 camera trap pictures were taken of 183 different raccoons over a monitorring period of 5,365 nights. 82 % of all the raccoon pictures showed individually tagged ani-mals. All 145 of the trapped raccoons were successfully genotyped as part of a subproject with highly polymorphic microsatellites. Both the familial relationships and the individual reproductive success of the subject animals could be determined with the genotyping results. For the analyses of the population structure, classic morphometric and phenotypical characteristics, as well as the cause of mortality of 120 raccoon carcasses in the immediate vicinity of the National Park, were recorded.
34

Säugetierkundliche Freilandforschung zur Populationsbiologie des Waschbären (Procyon lotor Linnaeus, 1758) in einem naturnahen Tieflandbuchenwald im Müritz-Nationalpark (Mecklenburg-Vorpommern)

Michler, Frank-Uwe Fritz 03 July 2017 (has links)
In der Dissertation werden Fragen zur Populationsbiologie des neozonalen Nordamerikanischen Waschbären (Procyon lotor) behandelt. Die knapp sechsjährigen Freilanduntersuchungen fanden im Rahmen eines umfangreichen Waschbärenforschungsprojektes (www.projekt-waschbaer.de) in einem naturnahen Tieflandbuchenwald im Müritz-Nationalpark (Mecklenburg-Vorpommern) statt. Das Nationalparkgebiet wird nachweislich seit Ende der 1970er Jahre vom Waschbären besiedelt und stellt aufgrund seines Gewässerreichtums und seiner alten Laubbaumbestände einen idealen Lebensraum für Waschbären dar. Die Dissertation schließt die populationsbiologischen Arbeiten des Gesamtprojektes ab und stellt die Ergebnisse in fünf separaten Themenschwerpunkten vor (I. Raumverhalten, II. Sozialverhalten, III. Reproduktionsbiologie, IV. Populationsstruktur, V. Populationsdynamik). Übergeordnetes Ziel der Arbeit war die Erhebung valider populationsbiologischer Daten, um eine grundlegende ökologische Charakterisierung des Waschbären unter dem Aspekt des Natur- und Artenschutzes vornehmen zu können. Dazu wurden zwischen 2006 und 2011 in einem 1.114 ha großen Fallennetz im Serrahner Teilgebiet des Nationalparks an 53 verschiedenen Fallenstandorten 145 verschiedene Waschbären (62 ♀♀, 83 ♂♂) insgesamt 489 Mal gefangen, genetisch beprobt, vermessen und individuell markiert. 51 adulte Waschbären (23 ♀♀, 28 ♂♂) und 18 Jungtiere (10 ♀♀, 8 ♂♂) wurden darüber hinaus mit einem UKW-Halsbandsender ausgestattet und im Rahmen der telemetrischen Arbeiten insgesamt 31.202 Mal geortet (≙ im Mittel 452 Lokalisationen pro Tier). Im Kernuntersuchungsgebiet wurde an 36 beköderten Standorten ein Fotofallenmonitoring durchgeführt. Bei einer Überwachungsdauer von 5.365 Fotofallennächten entstanden dabei 18.721 Aufnahmen von 183 verschiedenen Waschbären. 82 % aller Waschbärenbilder zeigten individuell markierte Individuen. Alle 145 gefangenen Waschbären wurden im Rahmen eines separaten Teilprojektes mit hochvariablen Mikrosatelliten erfolgreich genotypisiert, so dass die Verwandtschaftsverhältnisse sowie der individuelle Reproduktionserfolg der Untersuchungstiere bekannt sind. Für die Analysen zur Populationsstruktur wurden unter anderem von 120 verendet aufgefunden Waschbären (Totfunden) aus dem unmittelbaren Umfeld des Nationalparks klassische morphometrische und phänotypische Merkmale sowie die Mortalitätsursachen erfasst. / This study considers questions concerning the spatial and social behaviour, reproduction, population structure and dynamics of the alien North American raccoon (Procyon lotor) in Germany. The investigations took place within the framework of a comprehensive raccoon research project (www.projekt-waschbaer.de) over a period of nearly six years in a close-to-nature lowland beech forest in the Müritz National Park (Mecklenburg-West Pomerania). The National Park has been verifiably colonized by raccoons since the end of the 1970s, and due to its abundance of water and its old deciduous tree population it represents an ideal habitat for this mammal. Between 2006 and 2011, 145 individual raccoons (62 ♀♀ and 83 ♂♂) were captured, genetically sampled, measured and individually tagged. Sampling took place within a 1,114 hectare area of the National Park, at 53 trap sites and with 489 trappings. 51 adult raccoons (23 ♀♀, 28 ♂♂) and 18 juveniles (10 ♀♀, 8 ♂♂) were also fitted with radio collars and located a total of 31,202 times as part of the telemetric survey (=452 localisations per individual). Camera trap monitoring was carried out at 36 baited locations of the main investigation area (1,628 ha): 18,721 camera trap pictures were taken of 183 different raccoons over a monitorring period of 5,365 nights. 82 % of all the raccoon pictures showed individually tagged ani-mals. All 145 of the trapped raccoons were successfully genotyped as part of a subproject with highly polymorphic microsatellites. Both the familial relationships and the individual reproductive success of the subject animals could be determined with the genotyping results. For the analyses of the population structure, classic morphometric and phenotypical characteristics, as well as the cause of mortality of 120 raccoon carcasses in the immediate vicinity of the National Park, were recorded.
35

QUANTUM EFFECTS ON ENERGY TRANSPORT IN 2D HETERO-INTERFACES AND LEAD HALIDE PEROVSKITE QUANTUM DOTS

Victoria A Lumsargis (15060268) 10 October 2023 (has links)
<p dir="ltr">Photovoltaics are leading devices in green energy production. Understanding the fundamental physics behind energy transport in candidate materials for future photovoltaic and optoelectronic devices is necessary to both realize material limitations and improve efficiency. Excitons, which are bound electron-hole pairs, are central to determining how energy propagates throughout semiconductors. Exciton transport is greatly influenced by material dimensionality. In highly ordered quantum dot (QD) systems, electronic coupling between individual QDs can lead to coherent exciton transport, whereas in two-dimensional heterostructures, excitons can form at the interface of a heterojunction, creating charge-transfer excitons.</p><p dir="ltr">This dissertation is dedicated to summarizing the studies of exciton transport and behavior in two systems: perovskite QD superlattices and transition metal dichalcogenide (TMDC)/polyacene heterostructures. Chapter 1 provides readers with details on these materials in addition to information on the fundamental concepts (i.e., excitons, phonons, energy transfer) needed to best appreciate further chapters. Chapter 2 summarizes the spectroscopic techniques (photoluminescence and transient absorption spectroscopy and microscopy) used to examine exciton behavior. Next, the effects of disorder and dephasing pathways on the ability of perovskite QDs to coherently couple is investigated through the lens of superradiance in Chapter 3. After this, the temperature-dependent exciton transport within perovskite QD superlattices is imaged with high spatial and temporal resolutions in Chapter 4. The experimental transport data on these superlattices provides evidence for environment-assisted quantum transport, which, until this study, had yet to be realized in solid-state systems. In Chapter 5, attention is switched to verifying the existence and deepening the understanding of the behavior of several spatially separated interlayer excitons in a tungsten disulfide/tetracene heterostructure. Finally, Chapter 6 summarizes the preliminary results obtained through transient absorption spectroscopy on other TMDC/polyacene heterostructures where separation of the triplet pair state is attempted. </p><p dir="ltr">It is this author’s hope that this dissertation will not only summarize their graduate work but will also serve as inspiration for others to continue learning and contribute to the advancement of the energy research field.</p>
36

MODELING AND SIMULATION OF CUTTING MECHANICS IN CFRP MACHINING AND ITS MACHINING SOUND ANALYSIS

Kyeongeun Song (13169763) 28 July 2022 (has links)
<p>Carbon fiber bending during Carbon Fiber Reinforced Plastic (CFRP) milling is an important factor on the quality of the machined surface. When the milling tool rotates, the fiber first contacts the rake face instead of the tool edge at a certain cutting angle, then the fiber is bent instead of being cut by the tool. It causes the matrix and the fiber to fall out, and the fiber is broken from deep inside the machined surface. The broken fibers are pulled out as the tool rotates, which is known as pull-out fibers. The machining defect is the main cause of deteriorating the quality of the machined surface. To reduce such machining defects, it is important to predict the carbon fiber bending during CFRP milling. However, it is difficult to determine a point where fiber bending occurs because the fiber cutting angle changes every moment as the tool rotates. Therefore, in this study, CFRP milling simulation was performed to numerically analyze the machining parameters such as fiber cutting angle, fiber length, and the magnitude of fiber bending according to the different milling conditions. In addition, the deformation of the matrix existing between carbon fibers is predicted based on the fiber bending information obtained through simulation, and matrix shear strain energy model is developed. Also, the relationship between the matrix shear strain energy and machining quality is analyzed. Through verification experiments under various machining conditions, it is confirmed that the quality of the machined surface deteriorated as the matrix shear strain energy increased. Moreover, this study analyzed the fiber cutting mechanism considering bent fibers during CFRP milling and proposed a method to identify the type of machining mechanism through machining sound analysis. Through experiments, it was verified that fiber bending or defects can be identified through machining sound analysis in the high-frequency range between 7,500 Hz and 14,800 Hz. From the analysis, the effect of different chip thickness in up-milling and down-milling on fiber bending was investigated by analyzing simulation and sound signal. From machining experiments, the effect of this difference on cutting force and machining quality was verified. Lastly, we developed a minimum chip thickness and fiber fracture model in CFRP milling and analyzed the effect of fractured fibers on the machining sound. Carbon fibers located below the minimum chip thickness do not contact the tool edge and are compressed by the bottom face of the tool, and these fibers are excessively bent and broken. As these broken fibers are discharged while scratching the flank face of the tool, a loud machining sound is generated. Moreover, through the verification experiment, it was confirmed that the number of broken fibers is proportional to the loudness of the sound, and calculated number of broken fibers for one second using the fiber fracture model coincides with the high-frequency machining sound range of 7,500 Hz to 14,800 Hz.</p>
37

Sea Breeze Circulation in the Auckland Region:Observational Data Analysis and NumericalModelling

Khan, Basit Ali January 2010 (has links)
The main aim of this research is to improve our knowledge of the sea breeze circulation in the complex coastal environments, where more than one mesoscale circulations occur. Interaction of these circulations with each other and with external factors such as topographical features and large scale winds leads to pronounced changes in the thermodynamic structure of the boundary layer. The variations in sea breeze circulation also have distinct effect on the pollutant transport and dispersion mechanisms in the coastal urban areas. In this research, dynamic and thermodynamic characteristics of the sea breeze circulation and their associated air pollution potential have been investigated by utilizing observational data for two summer periods and numerical modelling techniques. Effect of some external factors such as gradient flow and terrain elevation has also been examined. Observed meteorological and air quality data was obtained from a number of monitoring sites within and around Auckland while Advanced Weather Research & Forecasting (WRF) and ‘The Air Pollution Model’ (TAPM) were employed to simulate meteorology and pollutant dispersion in Auckland. WRF is used to investigate the thermally induced mesoscale circulation while TAPM has been employed to examine the pollutant dispersion in the region. Both models were validated against observed data from six different sites within Auckland. Validation results of WRF and TAPM are also compared with surface meteorology. Validation and inter-comparison of the two models show that WRF performed better than TAPM for all the surface meteorology variables. WRF showed a positive bias in predicted winds speed and relative humidity and a cold bias in the near surface Temperature. TAPM on the other hand under-predicted surface winds, while near surface temperature and relative humidity are similar to WRF. Results show that the sea breeze occurred around 20% of the two summer periods of 2006 and 2007. Both observed data analysis and the numerical modelling results confirmed the existence of two thermally induced systems in the Auckland region. Bay breezes are initiated in the morning hours (0800 – 1000 hours) from small bodies of water (Manukau, Waitemata, and Kaipara Harbour, and along the Hauraki Gulf coastline), followed by mature sea breezes from the main bodies of water (Tasman Sea and larger Hauraki Gulf area) in the late morning. The cessation of sea breezes started after 1600 hours. Frequency of sea breeze days was the highest under coast-parallel gradient winds (southeast and northwest), with speeds < 6 m s-1. The predicted depth of the sea breeze inflow ranged between 200 and 600 m, while the depth of the return flow was in the range of 200 – 500 m. Sensible heat flux is an important control in the development of sea breeze over the region. Coastal mountain ranges helped early onset of the sea breeze, but also inhibited inland propagation. Strong jet-like westerly winds along the coastline near the Manukau Harbour are due partly to the narrow opening at the Manukau Head, reduced friction over the harbour water, and divergence of wind due to coastline shape. Gradient winds significantly affect the evolution of the sea breeze and modify many of its dynamics, such as the sea breeze inflow layer, return flow, inland penetration, sea breeze head, etc. Under northerly gradient flow northeast sea breeze lasts longer while under southerly gradient flow cessation of the westerly sea breeze was delayed. Over both east and west coasts, WRF predicted anticlockwise rotation, especially under easterly gradient wind conditions. However, inland stations near Manukau Harbour show partial and complete clockwise rotation, which is primarily due to orographic features of the region. The diurnal rotation of the sea breeze system may contribute to recirculation of pollutants in the morning hours under coast-parallel gradient wind conditions. Pollutants that are emitted during morning peak traffic hours and advected towards Manukau Harbour by the remnants of the land breeze may be returned by bay breezes in the mid morning hours. Mixed layer height over land before arrival of the sea breeze also varied a lot and ranged between 600 to 1400 m. A convective internal boundary layer (CIBL) forms in the surface layer after arrival of the sea breeze. The CIBL under coast parallel gradient winds was relatively shallow (200 – 400 m), while under coasts-normal gradient winds (southwest and northeast), the predicted depth was in the range of 400 to 500 m. However, the inland extent of the CIBL was greater under coast-normal winds, especially under south-westerly gradient winds. The ground level concentration of air pollutants thus can be increased during sea breeze inflow over the region. Both bay breeze and mature sea breeze contribute towards development, extent and strength of the sea breeze convergence zones (SBCZs). Gradient winds and terrain play an important role in the position and strength of SBCZs. Under strong south-westerly gradient flow, a SBCZ is formed along the eastern coastline, while under north-easterly gradient winds a SBCZ is formed along the west coastline. During coast-parallel gradient winds the SBCZ is formed in the middle of landmass, and is then gradually displaced eastward or westward depending on the balance between large scale PGF and surface friction effect. In addition to SBCZs, terrain and coastline-induced convergences were also evident. Higher ground level concentrations of pollutants are expected under coast-normal gradient winds, when SBCZs are formed in the middle of the land mass and the wind speed of the sea breeze inflow and the sea breeze front is relatively low. This may increase pollution concentration, especially in the evening hours, to unacceptable levels. Results of this research suggest that given the size, synoptic meteorology and specific geography of the region, significant recirculation of pollutants is not likely to happen to contribute to next day’s pollution. The pollutant concentration may increase in the SBCZs, but their ability to recirculate the pollutants requires more extensive research. A closed sea breeze circulation cell is unlikely to form in this region due to topographical influences and a strong gradient wind effect. The pollutant plume is expected to be advected in the return flow over the peaks of higher terrain and via the top of the convergence zones, but its remixing in the onshore flow is subject to many factors such as gradient wind speed and direction, direction of the return flow and nature (size and state) of the pollutant. In appropriate conditions, pollution levels may reach to unhealthy levels under coast-parallel gradient wind condition.
38

PhD Dissertation-Chemistry-Aayush-2023

Aayush Aayush (15354604) 26 April 2023 (has links)
<p> </p> <p>Learning about ‘behavior’ has always been at the heart of my research endeavors. While my undergraduate work in evolution and ecology exposed me to the science behind why a behavior exists, in my graduate work, I intended to explore how to use something’s behavior to widen its applicability. In this thesis, <em>I will present three works that utilize some of the fundamental</em></p> <p><em>behaviors (i.e., properties) of elastin-like polypeptides (ELP) to improve existing protein purification methods or explore their applicability in bladder cancer imaging and immunotherapy. </em></p> <p>Bladder cancer has high recurrence rates (60-70 % annually) that necessitate multiple follow-up therapies making it one of the costliest cancers per patient. In this work, we have attempted to address two leading causes of the recurrence. First is a low sensitivity (62-84 %) and variable specificity (43-95 %) of white light cystoscopy used to diagnose and remove tumors. We aimed to address the heart of this problem, i.e., the non-specific mode of detection using white light. Only the trained eyes can discern abnormal from normal-appearing tissues even then, leaving up to 45% of tumors unresected to colonize and spread. <em>We developed and characterized near infrared dye-peptide-ligand conjugates (NIR-ELP-ligand) that undergo receptor-mediated binding and internalization to human bladder cancer cells in vitro and tissues ex vivo.</em> By using a molecular target-based probe in combination with NIR imaging, we can aid in improving the detection limit via selective binding to the tumor and reduction in background autofluorescence.</p> <p>Bacillus-Calmette Guérin (BCG) instillation in the bladder is the gold-standard</p> <p>immunotherapy used after surgical removal of bladder tumors. This was approved as a response to the inefficiency of surgery alone in improving cancer status. It has succeeded by reducing the recurrence rate to 30-50 %. But it comes with the complications of putting a live mycobacterium</p> <p>in the human body and giving a patient a urinary tract infection right after surgical tumor resection. <em>Thus, we aimed to deliver nucleic acid as immunotherapeutic cargo in a selective manner to elicit robust anti-tumor immune responses while minimizing the side effects due to its carrier.</em> Towards</p> <p>this goal, we have developed a highly modular and adaptable ELP-ligand fusion protein-based nucleic acid delivery carrier targeted toward bladder cancer. Before developing targeted peptide-based cancer imaging and nucleic acid delivery modalities, we addressed the Achilles heel of peptide-based approaches. The peptide and protein industry suffers</p> <p>through complex, time-consuming, inconsistent, and low-yielding purification methods. <em>We have developed a scalable, facile, and reproducible protein purification method that delivers ELP and ELP fusion proteins free of host cell proteins and nucleic acids and has low lipopolysaccharide</em></p> <p><em>content in just 3 h starting from a bacterial pellet. </em>Thus, for a coherent narrative, the thesis is structured as follows:</p> <p>1. Introduction</p> <p>2. ELP as a protein purification tag: Development of a rapid purification method for ELPs and ELP fusion proteins.</p> <p>3. ELP as a cancer imaging agent: Development of NIR-ELP-Ligand imaging probe targeting bladder cancer.</p> <p>4. ELP as a drug delivery agent: Utilizing ELP-ligand fusion protein in the formulation of targeted nucleic acid delivery carrier to bladder cancer.</p>
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THE EFFECT OF MOLECULAR DESIGN ON SPIN DENSITY LOCALIZATION AND RADICAL-INITIATED DEGRADATION OF CONJUGATED RADICAL CATIONS

Kaelon Athena Jenkins (16613448) 19 July 2023 (has links)
<p> Radical species are essential in modern chemistry. In addition to fundamental chemistry, their unique chemical bonding and distinct physicochemical features serve critical functions in materials science in the form of organic electronics. Due to their high reactivity, radicals of the main group element are often transient. In recent years, remarkably stable radicals are often stabilized by π-delocalization, sterically demanding side groups, carbenes, and weakly coordinating anions. The impacts of modifications such as electron-donating, electron-withdrawing, and end-capping on the spin density distribution and thermodynamic and kinetic stability of archetypal radical-driven processes such as dimerization are not well understood. This dissertation aims to track the perturbation of spin density from EDG and EWG modifications, provide mechanistic insight into the radical-initiated reactions of conjugated radical cations, and establish correlations between molecular design and thermochemical properties and their resulting kinetic stability by computationally evaluating these characteristics against experimental data. The disclosed connections give useful new recommendations for the rational design of thermodynamically and kinetically stable novel materials.</p>
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CRYSTAL PLASTICITY OF PENTAERYTHRITOL TETRANITRATE (PETN)

Jennifer Oai Lai (17677422) 24 April 2024 (has links)
<p dir="ltr">We investigate the crystal plasticity and shock response of single crystal and polycrystalline pentaerythritol tetranitrate (PETN) using mesoscale finite element simulations. The model includes the Mie-Grüneisen Equation of State and a single crystal plasticity model. Simulations with single crystals with different orientations are tested using our plasticity model under shock compression to explore shear stress and slip. Parameters regarding the Mie-Grüneisen Equation of State are also verified in various orientations from 0.50 to 1.75 km/s. A polycrystalline PETN sample with varying grain sizes and orientations are subjected to shock loading with impact velocities ranging from 0.25 to 0.75 km/s. We study how differences in shock orientation affect slip and stress in PETN at different shock strengths.</p>

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