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1
MacArthur, Shona. "Bubbles guide migrating smolts around hydropower plants." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160490.
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The development of hydroelectric power production and the damming of water courses that ensues causes a threat to the migration patterns of Atlantic salmon (Salmo salar), by altering their habitat and compromising river connectivity. Because the species’ survival heavily depends on the completion of their migration between rivers and oceans, the design of guidance structures that promote successful passages around dams is a critical goal. Physical structures have been used to steer downwards-migrating smolts through safe fishways but they have not always proven effective, both from an ecological and economical perspective. In this study, the potential of bubbles in guiding salmon trajectories around a hydropower dam was tested as an alternative to existing guiding systems. Here the hypotheses were: i) bubbles guide downstream-migrating smolts around dams; ii) the reaction of smolts to a bubble barrier is linked to their individual boldness; iii) bubbles have varying effects on different school sizes. The first and third hypotheses were tested in the field, by recording sonar footage at the entrance of a fishway, downstream of a bubble barrier. The second hypothesis was evaluated by conducting a scototaxis experiment and an assessment of the reaction of young salmon to bubbles in the laboratory. My analysis of the fish abundance data collected in the river confirmed the first and third hypotheses. In the field, the presence of a predator (Esox lucius) was revealed to be a more influential factor than bubbles in regulating the number of smolts steered towards the fishway, indicating that predators generated a larger anxiety-like response in smolts than bubbles. In the controlled laboratory setting, there was no significant correlation between anxiety-like behaviour and reaction to bubbles and the second hypothesis did not appear to be valid. Therefore, the cause of avoidance of the barrier remains unclear, but bubble barriers seem to be an efficient and cost-effective structure for guiding downstream-migrating salmon smolts.
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Suddaby, Anthony J. R. "An experimental and theoretical investigation of the migration of moisture in cocoa beans." Thesis, London Metropolitan University, 1990. http://repository.londonmet.ac.uk/2993/.
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This work is essentially an investigation of non-convective moisture movement as the result of a temperature gradient in hygroscopic porous materials, in particular, cocoa beans. The aim of the research has been to determine experimentally the bulk moisture diffusion coefficient for cocoa, and, by quantifying it, to investigate the contribution of such diffusion to wetting and mould damage that has occurred on the surface of cargoes during shipment from West Africa to Northern Europe.
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Clark, Vincent Ralph. "The phytogeography of the Sneeuberg, Nuweveldberge and Roggeveldberge (Great Escarpment): assessing migration routes and endemism." Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1003756.
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The Great Escarpment forms a semi-continuous mountain system 5 000 km long, stretching from Angola in the north-west, south through Namibia, and into western, southern and eastern South Africa, including Lesotho and Swaziland. It is composed of a wide variety of geological suites but is unified in representing the edge of the African plateau and the passive Gondwanan continental margin. The Great Escarpment falls into all major climatic zones on the subcontinent, is a repository of palaeo- and neo-endemics, hosts more than half of southern Africa‟s centres of plant endemism, and has a rich suite of endemic fauna. In addition, the Great Escarpment is believed to be both a refugium and corridor for biological diversity. Despite the biological richness of the Great Escarpment, research to date has been fragmented and many sections of the Great Escarpment have not been studied. The aim of this study is to contribute to research on the Great Escarpment by undertaking a detailed floristic study of the southern Great Escarpment (the Sneeuberg, Nuweveldberge and Roggeveldberge). Together these mountains comprise approximately 1 000 km (one fifth) of the Great Escarpment, and occupy a transition zone between the summer rainfall zone in the east and the winter rainfall zone in the west. They are also the sections of Great Escarpment most closely situated to the Cape Floristic Region (CFR) and would thus be involved in hypothesised migration routes for lineages that also occur further north through the Drakensberg Alpine Centre (DAC) to the East African mountain chain. Detailed fieldwork of the southern Great Escarpment was undertaken over a period of four years in all seasons. Approximately 8 000 specimens were collected. Particular emphasis was placed on areas that may represent refugia, i.e. the highest plateaux and peaks, mesic areas and cliff-lines. An overview of each mountain range, together with their endemic plant species and phytogeography, is provided. Approximately ten new species have been discovered during this study, two of which have been described to date. Numerous endemics only known from their types have also been rediscovered. The Sneeuberg is defined as a new centre of plant endemism on the Great Escarpment (endemism of 2.3%), and the role of the Boschberg and Groot-Bruintjieshoogde (part of the Sneeuberg) as a nexus for floristic migration routes is discussed. The Nuweveldberge is shown to have low endemism despite a floristic tally similar to the Sneeuberg, while the Roggeveldberge are confirmed to be the most endemic-rich section of the southern Great Escarpment. The field data collected was augmented by available data in taxonomic revisions, and floras for the Sneeuberg, Nuweveldberge and Roggeveldberge were compiled. In order to floristically compare the southern Great Escarpment with other sections of the Great Escarpment and the CFR, a database of some 12 000 taxa was created using available floristic data for the CFR, DAC and Great WinterbergAmatolas, together with the data collated for the Sneeuberg, Nuweveldberge and Roggeveldberge. These data were analysed using phenetic methods and Parsimony Analysis of Endemicity (PAE). The results indicate stronger linkages in the east, particularly between the Sneeuberg and Nuweveldberge, and between the Sneeuberg and the Great WinterbergAmatolas. The relationship of the Roggeveldberge with the rest of the southern Great Escarpment remains ambiguous. In order to refine notions of connectivity and migration routes, 19 well-sampled phylogenies were assessed for sister-taxon disjunctions to explore CFRGreat Escarpment connections. Palaeo-connectivity between the CFR and southern Great Escarpment is most strongly supported for the south-eastern (SE) connection, and less so for the north-western (NW) and Matjiesfontein connections. There is support for the current (or recent) use of these three connections from numerous species that occur on both sides of the connections. Results of these analyses indicate that the southern Great Escarpment is a palaeo-corridor, the functioning of which has been broken by the aridification of the Nuweveldberge since the Last Glacial Maximum (LGM). Floristic connectivity is strongest in the east, from the Nuweveldberge to the DAC, and is less so in the west between the Nuweveldberge and the Roggeveldberge a finding attributed to the transition from a reliable winter rainfall regime on the Roggeveldberge to an unpredictable moisture regime on the Nuweveldberge. The mountains of the southern Great Escarpment are thus a series of refugia from a previous moister, cooler climate and are a corridor between the eastern and western components of the Great Escarpment. The SE connection is the primary link between the CFR and the eastern Great Escarpment Afromontane region in southern Africa. The implications of this research are that accurate conservation assessments and Red Data listings for many of the previously poorly-known endemics can now be made, and appropriate conservation measures implemented. Climate change remains the primary threat to these endemics and montane taxa in general, while degradation of wetlands is the primary threat to the water catchment service provided by the southern Great Escarpment. Future detailed research on the Great WinterbergAmatolas and Stormberg and a comprehensive flora of the HantamRoggeveldberge will further enhance our understanding of the floristics of the southern Great Escarpment, and provide the necessary data for comprehensive GIS-based models of proposed climate change scenarios for local, regional and national conservation planning.
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Yahaya, Ewura Seidu. "The effect of three Ghanaian plants on fibroblast migration, inflammation and bacterial growth in vitro." Thesis, University of Pretoria, 2018. http://hdl.handle.net/2263/70048.
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Medical conditions which cause morbidity and mortality, such as chronic wounds and infection, lead to significant medical costs. Much of the world's population is dependent on alternative medicine, of which herbal medicine forms a crucial part. In Ghana and other countries around the world, an estimated 70% of the population rely on alternative treatments like herbs for management of various forms of disease. However, even though medicinal plants are widely used for treatment, most have not been scientifically proven to be safe and efficacious. Hence there is need to assess the biological activity of these plants which may be a potential lead in drug development.
This study assessed the wound-related biological activities of three commonly used medicinal plants in Ghana (Aspilia africana, Boerhavia diffusa, and Erythrina senegalensis). Sequential extracts were prepared from the three plants using hexane, ethyl acetate, methanol, and water as solvents, in increasing polarity. Also, ethnomedicinal extracts were obtained with water as solvent, in accordance with the method used by traditional healers. Extracts were screened for phytochemical components using thin layer chromatography (TLC), and phytochemical fingerprinting performed with ultra performance liquid chromatography in tandem with time-of-flight mass spectrometry (UPLC-qTOF-MS). Cytotoxic potential of the extracts in SC-1 fibroblasts, C2C12-myoblasts, and differentiated THP-1-macrophages was determined using the sulforhodamine B staining assay, and cells morphologically assessed with phase contrast, PlasDIC, and live/dead staining microscopy. Acellular antioxidant activity was conducted by exploring the 2,2'-azino-bis[3-ethylbenzothiazoline-6-sulphonic acid] (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, whilst ability to protect against cellular oxidative stress was assessed using 2',7'-dichlorofluorescin diacetate as marker. Anti-inflammatory potential of extracts was evaluated using xanthine oxidase activity. Also, the ability of extracts to alter closure of artificially generated wounds in fibroblast and myoblast monocultures was determined using the scratch assay. The extracts were also assessed for their antibacterial effect using the disk diffusion and microdilution assays. Extracts with a minimum inhibitory concentration (MIC) above or equal to 1 mg/mL were evaluated for their ability to inhibit bacterial biofilms. Analysis using TLC indicated that alkaloids, flavonoids, and phenols were the major groups present. The UPLC-qTOF-MS analysis led to the verification of previously identified, as well as tentative identification of already-described phytochemical compounds or their derivatives in the plants. In addition to the already reported ascorbic acid, quercetin was also identified in A. africana. Furthermore, kaempferol, quercetin, and rutin were identified in the extracts of B. diffusa, the latter compound being identified for the first time in this plant. Also, for the first time, kaempferol, rotenone and rutin, were identified in extracts of E. senegalensis. Apart from these three compounds, neobavaisoflavone was also detected.
All the extracts recorded a half maximal inhibitory concentration (IC50) above 100 _g/mL in all three cell-lines. The most cytotoxic extracts to the myoblasts, fibroblasts, and macrophages, were the methanol and ethnomedicinal extracts of A. africana, and the hexane extract of E. senegalensis, with a maximum of 38.8% reduction in cell density respectively. The minimal cytotoxic potential of the extracts was further confirmed by the absence of morphological differences between treated and untreated cells.
Most of the extracts exhibited good ABTS radical scavenging activity (IC50 < 100 _g/mL). The strongest effect against the free radical was observed with the ethyl acetate extract of B. diffusa (IC50 = 21.23 _g/mL). On the contrary, most of the extracts recorded poor ability to scavenge the DPPH free radical. Only the methanol extracts of A. africana (IC50 = 278 _g/mL) and E. senegalensis (IC50 = 291 _g/mL) yielded IC50 values below the maximum tested concentration (320 _g/mL). This could possibly be ascribed to the differences in the stereoselectivity between the two free radicals, and the poor DPPH scavenging ability of hydrophilic antioxidants.
The effect of the extracts against AAPH-induced oxidation in the cells correlated with the antioxidant potential of the extracts. Whilst most of the extracts with good antioxidant potential suppressed AAPH-induced oxidative stress, the most profound effect was observed with pre-treatment of macrophages with the ethyl acetate extract of A. africana. The extract caused a 1.74-fold decrease in intracellular reactive oxygen species (ROS) concentration after 120 min following pre-treatment with 100 _g/mL, when compared with the AAPH control. This was comparable to the 1.89-fold reduction caused by the positive control compound, 5 _g/mL Trolox. The ethnomedicinal extracts of B. diffusa and E. senegalensis exhibited a dose-dependent increase in intracellular ROS in fibroblasts, with intracellular ROS concentration upon treatment with the extracts at 100 _g/mL being at least 23% higher than the negative controls. This suggest that the extracts could exhibit a possible pro-oxidant effect at higher concentrations. Quercetin, a compound with pro-oxidant effects at higher concentrations, was detected in the ethyl acetate extract of B. diffusa, which may describe this effect. However, none of the extracts used in the current study demonstrated the ability to significantly inhibit xanthine oxidase activity. The strongest activity against the enzyme (maximum of 15% inhibition) was exhibited by extracts of E. senegalensis.
The hexane extract of A. africana and the water extracts of B. diffusa increased migration of myoblast cells by 44.4% and 39.4%, respectively. This indicates a possible role of the extracts in enhancing collagen deposition and wound remodelling, two processes with myoblast involvement. On the other hand, six of the extracts decreased fibroblast migration, and therefore could have negative effects on wound healing processes such as collagen and matrix metalloproteinase synthesis. Further analysis would be required to ascertain the extent to which the extracts could impact activity of the cells. Also, the methanol extract of E. senegalensis (MIC = 0.5 mg/mL in E. coli) was the most effective against the micro-organisms tested. All the other extracts had MICs above 1 mg/mL. None of the extracts showed activity against Pseudomonas aeruginosa, Staphylococcus epidermidis and bacterial biofilms.
In conclusion, this study has scientifically demonstrated that the three plants may assist wound healing at different stages in the healing process. This could be achieved through their antioxidant effects, ability to suppress oxidative stress, antibacterial activity, and ability to enhance activity of fibroblasts and myoblasts. Practitioners should be cautioned against using high concentrations because of possible cytotoxicity.Thesis (PhD)--University of Pretoria, 2018.
Pharmacology
PhD
Unrestricted
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Villeneuve, Isabelle. "Variation morpho-physiologique des plants d'épinette blanche de différentes sources génétiques et implications pour la migration assistée." Master's thesis, Université Laval, 2015. http://hdl.handle.net/20.500.11794/26054.
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Les semences forestières génétiquement améliorées pourraient ne plus être adaptées aux sites où elles sont destinées à cause des changements climatiques. La migration assistée figure parmi les stratégies d'adaptation proposées pour maintenir la productivité forestière et diminuer la vulnérabilité des écosystèmes. Les réponses morpho-physiologiques des plants d’épinette blanche (Picea glauca (Moench) Voss) issus de huit vergers à graines ont été évaluées en pépinière et sur trois sites de plantation. La modélisation des courbes de croissance a montré que la hauteur des vergers méridionaux et de deuxième génération est significativement supérieure à celle des autres vergers. Un modèle à régression multiple a montré que la hauteur finale des plants était significativement corrélée aux conditions climatiques d’origine des vergers. Le verger et le site de plantation ont affecté significativement la croissance en hauteur des plants. Les résultats de la présente étude et ceux obtenus à long terme contribueront à raffiner les règles opérationnelles de transfert des semences propres à la migration assistée.Due to climate change, genetically improved trees may no longer be adapted to the sites where they are intended to be planted. Assisted migration is a potential adaptation strategy for maintaining forest productivity and reducing vulnerability in the face of a changing climate. Morpho-physiological responses of white spruce (Picea glauca (Moench) Voss) seedlings from eight seed orchards were evaluated in a nursery and at three planting sites. The modeling of growth curves showed that the height of both the southern orchards and second generation orchards was significantly higher than the other orchards. A multiple regression model showed that the final height of the plants was significantly correlated with climatic conditions of the orchards. The orchard and the planting site significantly affected height growth of seedlings. The results of this study and those obtained over the longer term should help to refine the operational rules of seed transfer for assisted migration.
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Hu, Qing. "Migration and plant uptake of radionuclides in laboratory soil columns and field lysimeter with contaminated water tables." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287371.
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Knight, Richard Spencer, and Richard Spencer Knight. "Aspects of plant dispersal in the southwestern Cape with particular reference to the roles of birds as dispersal agents." Doctoral thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/23272.
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The dispersal of plants with particular attention to the roles birds play as dispersal agents was studied in the southwestern Cape, South Africa from 1983 to 1985. The research was organized as ten inter-related studies, each with an independent data base. Each chapter focused on a different scale of plant dispersal processes ranging from regional assemblages of plant species to individual species. At the largest scale, the seven vegetation types commonly occurring in the southwestern Cape were examined for incidence of vertebrate-dispersed plants. Coastal Thicket and Afromontane Forest were found to be the richest in these species. The colonization of vertebrate-dispersed plants was examined in an artificially cleared area of Mountain Fynbos vegetation. Enhanced densities of vertebrate-dispersed species were found in areas where perches had been provided. The seasonal availability of vertebrate-dispersed species was found to be most continuous in Coastal Thicket vegetation. Fruit displays of vertebrate-dispersed indigenous plants were found to vary from those that were sporadic and inconspicuous, to those that were conspicuous and predictable, whereas those of alien plants were usually large and conspicuous. Avian use of these fleshy fruits in Coastal Thicket was examined and found to be proportional to their availability. A study of fruit presentation in relation to leaf number and stem thickness suggested that sessile, stem attached fruits have fewer local leaves at time of ripening than fruits which are presented in panicles. This may enhance accessibility and conspicuousness of stem attached fruits for dispersal by birds. Four autecological studies tested certain predictions arising from models developed to describe fruit/frugivore interactions. The dispersal of the alien Acacia cyclops seeds by the indigenous Black Korhaan Eupodotis afra suggested that successful fruit/frugivore relationships are not necessarily the product of reciprocal evolution. The study on Chrysanthemoides monilifera found that efficient dispersal systems are not limited to plants producing small quantities of lipid-rich fruits and to dispersal by obligate frugivores. The abiotic dispersal of Quercus robur was found to be efficient in relation to vertebrate-dispersal. The study on Protasparagus aethiopicus found that the morphology of fleshy fruits may also reflect attempts to overcome the effects of non-dispersing seed predators. 1It is concluded that a gradient from a predictable to unpredictable fruit availability provides a better basis for studying fruit/frugivore interactions than the coevolutionary models. previously presented.
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Everist, Mary Patricia. "Immigrant vulnerability in high-risk industry a socio-occupational examination of counties with large meatpacking plants in Iowa and Nebraska /." [Tampa, Fla.] : University of South Florida, 2005. http://purl.fcla.edu/fcla/etd/SFE0001051.
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Bytebier, Benny (Benny Leopold Germaine). "Molecular phylogenetic relationships within the subtribe Disinae (Orchidaceae) and their taxonomic, phytogeographic and evolutionary implications." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/19441.
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Dissertation (PhD)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: Twenty five years after the last major morphological revision, phylogenetic relationships were inferred on the basis of a new DNA dataset for the African orchid subtribe Disinae, which includes the large genus Disa and the small genus Schizodium. One nuclear gene region (ITS) and two plastid gene regions (trnLF and matK) were sequenced for 136 ingroup, representing 70% of all known Disinae species, as well as for 7 outgroup taxa. The combined data matrix contained 4094 characters and was analysed using parsimony and Bayesian inference. The generic status of Schizodium can no longer be supported, as it is deeply embedded within the genus Disa. Furthermore, the currently recognised subgenera do not reflect the phylogenetic relationships. Several of the currently recognised sections are monophyletic, others contain misplaced elements, while some are polyphyletic. These results necessitate a re-classification of the Disinae. A monotypic subtribe Disinae and a subdvision of Disa into eighteen sections is formally proposed. These sections are monophyletic, well-supported, morphologically distinguishable and are delimited to maximize the congruence with the previous classification. All currently known species are enumerated and assigned to sections. Likelihood optimisation onto a dated molecular phylogeny is subsequently used to explore the historical biogeography of Disa, as well as of three other Cape lineages (Irideae p.p., the Pentaschistis clade and Restionaceae), to find out where these lineages originated and how they spread through the Afrotemperate region. Three hypotheses have been proposed: (i) a tropical origin with a southward migration towards the Cape; (ii) a Cape origin with a northward migration into tropical Africa and (iii) vicariance. None of these hypotheses, however, has been thoroughly tested. In all cases, tropical taxa are nested within a predominantly Cape clade and there is unidirectional migration from the Cape into the Drakensberg and from there northwards into tropical Africa. Dating estimates show that the migration into tropical East Africa has occurred in the last 17 million years, consistent with the Mio-Pliocene formation of the mountains in this area. The same technique is then utilised to reconstruct the temporal occurrence of ancestral ecological attributes of the genus Disa. The first appearance of species in the grassland and savanna biomes, as well as in the subalpine habitat, are in agreement with the existing, reliable geological and paleontological information. This suggests that phylogenies can be used to date events for which other information is lacking or inconclusive, such as the age of the fynbos biome and the start of the winter rainfall regime in southern Africa. The results indicate that these are much older than what is currently accepted and date back to at least the Oligocene.
AFRIKAANSE OPSOMMING: Vyf-en-twintig jaar na die laaste groot morfologiese hersiening, is die filogenetiese verwantskappe van die Afrika orgideë subtribus Disinae, wat die groot genus Disa en die klein genus Schizodium insluit, in hierdie studie op grond van ‘n nuwe DNA datastel afgelei. Daar is van 136 binnegroep, wat 70% van alle bekende Disinae spesies verteenwoordig, sowel as sewe buitegroep taksa geenopeenvolgings van een nukleêre geen streek (ITS) en twee plastiedgeen streke (trnLF en matK) bepaal. Die gekombineerde data matriks het 4094 karakters bevat en is met die parsimonie en Bayesian metodes ontleed. Die generiese status van Schizodium kan nie hieruit ondersteun word nie, en is diep ingebed binne die genus Disa. Die huidiglik aanvaarde subgenera word ook nie deur hierdie filogenie ondersteun nie. Verskeie van die huidiglik herkende seksies is bevind om monofileties te wees, ander bevat verkeerd geplaasde spesies, terwyl ander polifileties blyk te wees. ’n Monotipiese subtribus Disinae en ’n onderverdeling van Disa in agtien seksies word formeel voorgestel. Dié seksies is monofilities, goed ondersteun, morfologies onderskeibaar en omskryf om maksimaal ooreen te stem met die vorige klassifikasie. Alle huidiglik bekende spesies word gelys en toegewys aan seksies. Waarskynlikheidsoptimalisering op ’n gedateerde molekulêre filogenie is dan gebruik om die historiese biogeografie van Disa te ondersoek, tesame met drie ander Kaapse groepe (Irideae p.p., die Pentaschistis klade en Restionaceae), om te bepaal waar hierdie groepe hulle oorsprong gevind het en hoe hulle na die “Afrotemperate“ streek versprei het. Drie hipoteses word voorgestel: (i) ’n tropiese oorsprong met ’n suidwaartse migrasie na die Kaap; (ii) ’n Kaapse oorsprong met ’n noordwaartse migrasie na tropiese Afrika, en (iii) vikariansie. Geen van hierdie hipoteses is egter vantevore deeglik getoets nie. In alle gevalle is bevind dat die tropiese taksa oorwegend binne ’n Kaapse klade gesetel is, en dat daar ’n eenrigting migrasie is van die Kaap na die Drakensberge en van daar noordwaarts na tropiese Afrika. Dateringsskattings toon dat die migrasie na tropiese Oos-Afrika in die laaste 17 miljoen jaar plaasgevind het, ooreenstemmend met die Mio-Plioseen vorming van die berge in die area. Dieselfde tegniek is daarna aangewend om die temporale voorkoms van voorvaderlike ekologiese eienskappe van die genus Disa te rekonstrueer. Die eerste voorkoms van die spesies in die grasveld en savanna biome, sowel as die subalpiene habitat, is in ooreenstemming met bestaande, betroubare geologiese en paleontologiese informasie. Dit suggereer dat filogenieë gebruik kan word om gebeurtenisse te dateer waarvoor daar informasie ontbreek of nie beslissend is nie, soos die ouderdom van die Fynbos bioom en die begin van die winterreënval stelsel in suider-Afrika. Die resultate dui daarop dat dit heelwat ouer is as wat tans aanvaar word en terugdateer na ten minste die Oligoseen.
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MOLNARY, LESLIE de. "Caracterizacao de um modelo de camada limite planetaria para avaliar liberacoes de radionuclideos em instalacoes nucleares." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10355.
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Made available in DSpace on 2014-10-09T12:37:42Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:00:15Z (GMT). No. of bitstreams: 1 12905.pdf: 6893791 bytes, checksum: 505c8ae6d27e32929e2edfaa656b4e81 (MD5)
Dissertacao (Mestrado)
IEA/D
Instituto Astronomico e Geofisico, Universidade de Sao Paulo - IAG/USP
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Tremblay, Nicolas-Olivier R. "Molecular phylogeography of Dryas integrifolia : glacial refugia and postglacial recolonization." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20880.
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This thesis addresses the consequences of the last glaciation on the distribution and genetic diversity of arctic flora. The principal aim is to infer the full-glacial and postglacial migrational history of Dryas integrifolia M. Vahl. (Rosaceae) from the intraspecific phylogeny of cpDNA haplotypes along with pollen and macrofossil distribution data. The results suggest that four refugia existed during the last glaciation and that each served as significant sources of recolonization when the ice retreated. The two most important refugia are located in the northwestern Arctic (Beringia and the High Arctic), with two other refugia located southeast of the ice sheet and along the coastal regions of the eastern Arctic. High genetic substructure among populations is likely attributable to past vicariance and recent recolonization events, whereas high local diversity is probably indicative of recolonization from several sources and high gene flow in recent time.
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Holzinger, Andreas. "Exploring the cellular mechanisms that control cell shape formation, nuclear migration and chloroplast adaptations to environmental conditions in algae and higher plants." Dortmund Schwerte, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=2922989&prov=M&dok_var=1&dok_ext=htm.
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Perera, Muthukuttige. "Phytochemical analysis of two Australian native plants and their effects on chronic wound healing." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/229994/1/Muthukuttige%20Madusha%20Nuwanthi_Perera_Thesis.pdf.
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Chronic wounds are a significant burden to national health services worldwide and a potential reason for patients’ declining quality of life. As such, this project focused on assessing the therapeutic effect of two Australian native plants, Alocasia macrorrhizos and Syncarpia hillii for their potential in chronic wound healing, through investigating their antibacterial, anti-inflammatory, and regenerative properties.
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Rivinoja, Peter. "Migration problems of Atlantic salmon (Salmo salar L.) in flow regulated rivers /." Umeå : Dept. of Aquaculture, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/2005114.pdf.
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Smith, JoEtta Kaye. "Selection and Use of Aquatic Vegetation by Migratory Waterfowl in North Central Texas." Thesis, University of North Texas, 2001. https://digital.library.unt.edu/ark:/67531/metadc2779/.
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Assessment of aquatic plant selection by waterfowl has been conducted during the winters of 1997-2000 on 49 0.2-0.79 ha research ponds in north central Texas. Ponds were categorized by dominant plant species into eight habitat types. Census with waterfowl species identification were performed to investigate impacts of aquatic vegetation and water depth on waterfowl. Eighteen waterfowl species were observed. Peak migration occurred in late December/early January. Mixed native ponds and mixed native/hydrilla ponds were the most frequently selected habitat types. The study included correlation analysis between pond water levels and waterfowl use. Full ponds received greatest use followed by half full ponds, while almost empty ponds received minimal use. Time activity budgets were conducted on waterfowl utilizing mixed native and hydrilla ponds to compare waterfowl time partitioning on native aquatic vegetation versus hydrilla. Although only minor differences were found in time budgets, social status appears to be strongly related to habitat selection. Ducks on native ponds were paired (86%), conversely no ducks on hydrilla ponds were paired. Hydrilla pond although frequently utilized, were populated by lower status birds mostly single hens.
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Ross, Boulianne Michael 1982. "Assessing the effects of the Baie-des-Sables (Quebec) wind farm on the spring migratory behaviour and abundance of raptors." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116036.
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Despite their environmental benefits, wind farms, have attracted controversy with regard to their impacts on birds. These impacts include collision risks, direct and indirect habitat loss and barrier effects. The main objectives of this study were to determine whether the Baie-des-Sables wind farm, located on the south shore of the St-Lawrence River, is having an impact upon the spring migration of raptors. Emphasis was placed on comparing the differences between both behaviour and abundance of migrating raptors between the wind farm and a contr9l area. Three aspects of behaviour were recorded; altitude, change in direction and flight type. No significant differences were found between the wind, farm area and the control area with respect to migratory behaviour and abundance of any species. Low-lying topography and the fact most migratory raptors flew above blade height likely explain why no differences were found between the wind farm and control area.
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Choi, Jong-Won. "Geomechanics of subsurface sand production and gas storage." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39493.
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Improving methods of hydrocarbon production and developing new techniques for the creation of natural gas storage facilities are critically important for the petroleum industry. This dissertation focuses on two key topics: (1) mechanisms of sand production from petroleum reservoirs and (2) mechanical characterization of caverns created in carbonate rock formations for natural gas storage. Sand production is the migration of solid particles together with the hydrocarbons when extracted from petroleum reservoirs. It usually occurs from wells in sandstone formations that fail in response to stress changes caused by hydrocarbon withdrawal. Sand production is generally undesirable since it causes a variety of problems ranging from significant safety risks during high-rate gas production, to the erosion of downhole equipment and surface facilities. It is widely accepted that a better understanding of the mechanics of poorly-consolidated formations is required to manage sand production; which, in turn, enables the cost effective production of gas and oil resources. In this work, a series of large-scale laboratory experiments was conducted in fully saturated, cohesionless sand layers to model the behavior of a petroleum reservoir near a wellbore. We directly observed several key characteristics of the sand production phenomenon including the formations of a stable cavity around the wellbore and a sub-radial flow channel at the upper surface of the tested layer. The flow channel is a first-order feature that appears to be a major part of the sand production mechanism. The channel cross section is orders of magnitude larger than the particle size, and once formed, the channel becomes the dominant conduit for fluid flow and particle transport. The flow channel developed in all of our experiments, and in all experiments, sand production continued from the developing channel after the cavity around the borehole stabilized. Our laboratory results constitute a well constrained data set that can be used to test and calibrate numerical models employed by the petroleum industry for predicting the sand production phenomenon. Although important for practical applications, real field cases are typically much less constrained. We used scaling considerations to develop a simple analytical model, constrained by our experimental results. We also simulated the behavior of a sand layer around a wellbore using two- and three-dimensional discrete element methods. It appears that the main sand production features observed in the laboratory experiments, can indeed be reproduced by means of discrete element modeling. Numerical results indicate that the cavity surface of repose is a key factor in the sand production mechanism. In particular, the sand particles on this surface are not significantly constrained. This lack of confinement reduces the flow velocity required to remove a particle, by many orders of magnitude. Also, the mechanism of channel development in the upper fraction of the sample can be attributed to subsidence of the formation due to lateral extension when an unconstrained cavity slope appears near the wellbore. This is substantiated by the erosion process and continued production of particles from the flow channel. The notion of the existence of this surface channel has the potential to scale up to natural reservoirs and can give insights into real-world sand production issues. It indicates a mechanism explaining why the production of particles does not cease in many petroleum reservoirs. Although the radial character of the fluid flow eventually stops sand production from the cavity near the wellbore, the production of particles still may continue from the propagating surface (interface) flow channel. The second topic of the thesis addresses factors affecting the geometry and, hence, the mechanical stability of caverns excavated in carbonate rock formations for natural gas storage. Storage facilities are required to store gas when supply exceeds demand during the winter months. In many places (such as New England or the Great Lakes region) where no salt domes are available to create gas storage caverns, it is possible to create cavities in limestone employing the acid injection method. In this method, carbonate rock is dissolved, while CO₂ and calcium chloride brine appear as products of the carbonate dissolution reactions. Driven by the density difference, CO₂ rises towards the ceiling whereas the brine sinks to the bottom of the cavern. A zone of mixed CO₂ , acid, and brine forms near the source of acid injection, whereas the brine sinks to the bottom of the cavern. Characterization of the cavern shape is required to understand stress changes during the cavity excavation, which can destabilize the cavern. It is also important to determine the location of the mixture-brine interface to select the place of acid injection. In this work, we propose to characterize the geometry of the cavern and the location of the mixture-brine interface by generating pressure waves in a pipe extending into the cavern, and measuring the reflected waves at various locations in another adjacent pipe. Conventional governing equations describe fluid transients in pipes loaded only by internal pressure (such as in the water hammer effect). To model the pressure wave propagation for realistic geometries, we derived new governing equations for pressure transients in pipes subjected to changes in both internal and external (confining) pressures. This is important because the internal pressure (used in the measurement) is changing in response to the perturbation of the external pressure when the pipe is contained in the cavern filled with fluids. If the pressure in the cavern is perturbed, the perturbation creates an internal pressure wave in the submerged pipe that has a signature of the cavern geometry. We showed that the classic equations are included in our formulation as a particular case, but they have limited validity for some practically important combinations of the controlling parameters. We linearized the governing equations and formulated appropriate boundary and initial conditions. Using a finite element method, we solved the obtained boundary value problem for a system of pipes and a cavern filled with various characteristic fluids such as aqueous acid, calcium chloride brine, and supercritical CO₂ . We found that the pressure waves of moderate amplitudes would create measurable pressure pulses in the submerged pipe. Furthermore, we determined the wavelengths required for resolving the cavern diameter from the pressure history. Our results suggest that the pressure transients technique can indeed be used for characterizing the geometry of gas storage caverns and locations of fluid interfaces in the acid injection method.
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Dürmann, Christoph [Verfasser], and Wilhelm [Akademischer Betreuer] Kley. "Migration of Massive Planets / Christoph Dürmann ; Betreuer: Wilhelm Kley." Tübingen : Universitätsbibliothek Tübingen, 2017. http://d-nb.info/1165577682/34.
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Darras, Eric L. "Plans de migration de systèmes patrimoniaux vers des ERP." Thesis, Université Laval, 2004. http://www.theses.ulaval.ca/2004/21998/21998.pdf.
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Les progiciels de gestion intégrés (ERP) sont des applications fonctionnant à travers une organisation qui, grâce à leur intégration, automatisent les processus d’affaires de l’organisation. Les ERP se sont rapidement imposés dans l’industrie pour remplacer des applications patrimoniales. La pratique démontre que la majorité des déploiements de ERP dépassent leurs budgets et leurs échéances, par conséquent la recherche s’est mise à étudier les projets de migration pour fournir un cadre de déploiement optimal. Peu d’exemples de déploiement dans de grandes organisations sont documentés rigoureusement. Les applications ERP sont divisées en modules qui doivent être connectés à l’environnement patrimonial de l’organisation pour fournir des avantages concurrentiels. L’intégration des applications de l’entreprise (EAI) est définie comme le processus d’intégration d’applications avec l’environnement informatique. Le déploiement d’applications ERP peut être aisé lorsque les organisations possèdent une structure hiérarchique simple et réalisent des opérations dans un ou quelques lieux géographiques. Mais lorsque les organisations ont une structure hiérarchique complexe et sont géographiquement dispersés, le déploiement implique des choix, des défis techniques et de gestion uniques.
Ce mémoire résume les stratégies de migration, les meilleures pratiques de réingénierie des processus d’affaires, l’analyse des applications patrimoniales et l’influence de la centralisation du pouvoir sur les processus d’une organisation.Enterprise Resource Planning (ERP) systems are enterprise wide systems which, because of their integration, automate many business processes of a company. They have rapidly become the de facto industry standard for replacement of legacy systems. Because there is evidence that the overwhelming majority of ERP implementations exceed their budget and their time allocations, researchers have begun to analyse ERP implementation in case studies in order to provide an implementation framework which maximises efficiencies. Few examples of large organisation implementations are thoroughly documented. ERP applications are divided into modules that must be connected to an organisation's software environment to provide leverage. Enterprise Application Integration (EAI) is defined as the process of integrating enterprise systems with existing applications. Implementing ERP systems can be straightforward when organizations are simply structured and operate in one or a few locations. But when organizations are structurally complex and geographically dispersed, implementing ERP systems involves difficult, possibly unique, technical and managerial choices and challenges. This research summarises implementation strategies, best practices to reengineer business processes, analyse legacy software and the influence of centralisation of power on organisational processes.
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Winters, Dahl Moody Aaron. "Arctic plant migration by 2100 comparing predictions with observations /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2009. http://dc.lib.unc.edu/u?/etd,2337.
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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2009.Title from electronic title page (viewed Jun. 26, 2009). "... in partial fulfillment of the requirements for the degree of Master of Science in the Curriculum of Ecology." Discipline: Ecology; Department/School: Ecology.
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Al-Samman, Winkel Noura. "Quelques mécanismes contribuant au comportement pionnier de trois espèces méditerranéennes pérennes : "Dorycnium pentaphyllum Scop.", "Euphorbia nicaensis All.", et "Aphyllantes monspeliensis L."." Montpellier 2, 1992. http://www.theses.fr/1992MON20263.
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3 especes vivaces mediterraneennes sont etudiees a differents stades. L'heteromorphisme dans les graines de d. Pentaphyllum, la dormance et la durete des teguments de celles-ci chez a. Monspeliensis et la reponse germinative rapide et abondante chez e. Nicaeensis presentent differentes adequations a l'incertitude environnementale. Le taux de croissance et l'aptitude competitive dans les 3 especes etaient fonction des surfaces d'exploitation specifiques et de la plasticite dans leur ajustement. Au stade adulte, ces especes montrent des traits bien adaptes a la region et une grande plasticite dans l'effort reproductif et les modes d'allocation des ressources, de facon a survivre et augmenter les chances de survie des descendants, suivant le contexte du milieu. E. Nicaeensis presente un exemple interessant de la selection divergente operant dans les habitats marginaux et heterogenes, conduisant a une differenciation des flux polliniques et geniques, en relation avec differentes realisations phenotypiques selon la nature des mosaiques du milieu. La richesse des tactiques et la grande aptitude competitive chez e. Nicaeensis semblent se baser sur des modifications importantes dans son genome, qui peuvent faire l'hypothese d'une paleoploidie
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Ramasawmy, Lucy Jane. "Lives and plans of Polish migrant families in Edinburgh." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9850.
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This thesis takes as its subject Polish families who migrated to Edinburgh after Poland’s accession to the EU in 2004. It analyses the families’ post-migration trajectories and experiences, and investigates how these are influenced by factors relating to Polish history and culture, by features particular to the post-accession migration wave and by families’ individual characteristics. Theoretical approaches are drawn from a range of academic disciplines including, reference group theory, literature relating to gender-division of paid work and child-care, and ‘mobilities’ theory, and these approaches are all employed in exploring the factors that influence family members’ integration, employment and lifestyles and their plans for the future. This qualitative study focuses on the experiences of thirty families living in and around Edinburgh in the two years from 2009 to 2011, and combines a variety of methods in data-collection and in analysis. Families were interviewed twice with a year lapse between interviews, couples were interviewed jointly and conversational interviews were supplemented with questionnaires. These design features enable analysis of change over time, provide insight into family-dynamics and generate a range of forms of data. In analysis the combination of thematic coding of interview transcripts with Qualitative Comparative Analysis, allows in-depth exploration of experiences at the individual and family level to be positioned within the context of trends and patterns observed across the whole group. The study finds that the families fall into distinct types according to particular key characteristics and migration strategies, and that the different family types are linked to different experiences of life in Scotland and plans for the future. Younger migrants who arrived independently, decided to stay and later started families are found to be embarking on new careers and making use of the greater flexibility of the employment market in the UK to enact their preferred division of work and childcare. In line with previous research findings, for families whose oldest child is preschool age, school start date in Poland is identified as critical in limiting the period in which parents feel the decision about whether to return can be made. Parents who migrated with school-age children because of financial hardship in Poland are highlighted in this study as a previously under-researched post-accession migrant group; among these families most parents within the study group are found to have been considering permanent settlement at the time of migration and to be maintaining this intention; their decision to stay is particularly influenced by concerns about the difficulties that they anticipate their children would encounter in re-entering the school system in Poland and about their own reduced ability to re-enter the labour market there after de-skilling in employment in the UK. Parents who migrated to take up professional work in the UK are identified as possessing the highest levels of ‘motility’, that is, capacity to make use of mobility generally; among the study group these parents are found to have the most varied options and future plans and to be those who indicate the greatest likelihood of leaving the UK in the short term.
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Elder, D. L. "Carbon migration across dissimilar metal welds, related to power plant." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598798.
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This thesis deals with the changes in chemical composition and microstructure that occur when a joint between two different steels is heat treated for prolonged periods of time at a temperature below that at which austenite forms. Such joints are common place in power plant where components with different purpose are joined by welding. The aim of the work was to characterise the changes that occur at the weld junction and to quantitatively model them such that the method has predictive power. Metallographic analysis on dissimilar steel welds and bonds, heat-treated over a range of times and temperatures showed the ease of decarburised and carburised zone formation and their associated microstructures. In the low-alloy steel, rapid carbide dissolution close the dissimilar interface leaves room for grain growth that forms a decarburised zone. In the associated carburised zone, perception at and carbide coarsening occurred on grain boundaries and intra-granularly due to the associated increase in carbon concentration. In vanadium-containing low-alloy steels, stable vanadium-alloy carbides were found to complicate carbon partitioning generating wider, shallower decarburised zones compared to the smaller, almost carbide-free ones in vanadium-free steels. A model, developed for estimating the decarburised zone width in ferritic transition joints considers the carbon concentration as a function of distance from the dissimilar interface resulting from chemical potential gradients in the joint. Written in FORTRAN 77, the model uses the Crank-Nicholson implicit finite difference solution of Fick's second law, and was found to accurately predict decarburised zone widths based on measurement taken from welds and bonds from a given series of tempering tests. The existence of substantial carbon chemical potential gradients in the transition joint causes carbides to dissolve in the low-alloy steel during heat-treatment, releasing carbon to diffuse across the dissimilar interface to form a corresponding carburised zone. Naturally, the temperature and time of the heat treatment influences carbon diffusion, but the particular alloy combination in the transition joint also affects the amount of carbon partitioning.
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Li, Zhen. "Minority migration from 1985 to 2005 in China| Migration process, migration outcomes, and socioieconomic incorporation at destination places of four ethnic minority groups." Thesis, State University of New York at Albany, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10109581.
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As internal migration started to increase in the late 1970s in China, ethnic minorities have also participated in this demographic event to improve their livelihood. However, minority migration has been much neglected in the current literature. To fill the gap in the literature, the dissertation aims to: (1) examine migration selectivity and destination selection process of ethnic minorities in China; (2) investigate whether migration can lead to upward socioeconomic mobility for ethnic minorities; (3) assess the extent of socioeconomic integration of minority migrants at destination places; (4) reveal and explain differences in patterns of migration and destination adaption across ethnic groups; and (5) uncover temporal patterns of minority migration, migration outcomes, minority integration at destinations. To achieve these goals, this dissertation makes use of the micro-data of the 1990 China population census, the 1995 mini-census, the 2000 census and the 2005 mini-census.
Regarding minority migration process, model results suggest that education selectivity of minority migrants is mostly positive, but it is only consistently observed for the Zhuang. While migrant networks and co-ethnic networks does not matter much for the out-migration decision for minorities, they do weigh more on minority migrants’ decision as to where to go. Minority migrants tend to go to places with larger migrant networks. In general, they also go to places with more co-ethnics, but the effect of co-ethnic networks reveals important group-specific differences.
Minorities can mostly benefit from engaging in migration. However, what is interesting is the finding that the Uyghurs stand out as the only minority group that shows a trend of deteriorating migration outcomes. Moreover, evidence also reveals that for the Uyghurs and the Zhuang, long-distance migration is not more beneficial than short-distance migration.
Finally, very different patterns of incorporation at destination communities emerge from the analyses. The relative position of the Uyghur migrants to the Han is declining over time and in the most recent time period, they are doing significantly worse than their Han counterparts. The Hui and the Koreans are doing more successfully. Surprisingly, the Zhuang migrants are disadvantaged to the Han and this disadvantage is consistent across time.
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Delfeld, Bradley. "Movin' on Up: Mycorrhizal Mutualisms and Assisted Migration of Coastal Plant Species." OpenSIUC, 2019. https://opensiuc.lib.siu.edu/theses/2603.
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Coastal marshes are among the first ecosystems to be altered by climate change. With increasing sea-level rise, assisted migration may be necessary to establish founder populations in more favorable upslope habitats. Mycorrhizal mutualisms could play a key role in determining success of these moving populations. If the assemblages of fungal spores are well mixed across the coastal transition gradient, then landward-retreating plant species can form associations with the same fungal species in the new habitat. The objectives of this study were: (1) to identify potential mycorrhizal relationships by determining if assemblages of spores exhibit zonation mirroring that of coastal plant communities and (2) to test whether or not abundance and composition of mycorrhizae in roots of a dominant marsh species (Juncus roemerianus) differ with simulated assisted migration into upslope soils. Soil samples and seeds for trap plants were collected from the coastal coenocline at Grand Bay National Estuarine Research Reserve in coastal Mississippi, USA. A total of 1607 unique operational taxonomic units (OTUs) was found across the entire gradient and was classified into five genera: Rhizophagus, Glomus, Funneliformis, Diversispora and Scutellospora. The soil samples had an average of 196.25 OTUs per sample, while the root samples were less diverse with an average of 29.04 OTUs per sample. DNA analysis of soil samples show that Glomeromycete propagules exhibit zonation on the seaward-most end of the gradient (salt marsh), but AMF composition becomes increasingly mixed with increasing elevation in brackish marsh, fresh marsh and pine woodlands zones. Salt marsh showed isolation in its species composition, sharing only two OTUs with the other three zones. Only one OTU (Rhizophagus sp.) was present across all four vegetation zones. Species richness and abundance of mycorrhizal spores in the soil samples increased along the elevation gradient; they were highest in the pine woodlands (dry end) and lowest in the salt marsh (wet end). OTU richness and abundance significantly increased in the roots of J. roemerianus trap plants when transplanted to soils upslope of its naturally dominant zone (brackish marsh). These results indicate that, apart from the salt marsh, plant-mycorrhizae relationships can persist after upslope migration of coastal plant species. New, as well as old, fungal associations may aid in the survival of the host plant in the new habitat.
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Lufkin, Graeme. "Simulations of giant planet migration in gaseous circumstellar disks /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9698.
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Uribe, Uribe Ana Lucía [Verfasser], and Thomas [Akademischer Betreuer] Henning. "The migration of planets in protoplanetary disks / Ana Lucía Uribe Uribe ; Betreuer: Thomas Henning." Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://d-nb.info/1179783859/34.
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Uribe, Ana Lucía [Verfasser], and Thomas [Akademischer Betreuer] Henning. "The migration of planets in protoplanetary disks / Ana Lucía Uribe Uribe ; Betreuer: Thomas Henning." Heidelberg : Universitätsbibliothek Heidelberg, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-131276.
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Villedieu, Aurélien. "Epithelial folding and migration." Electronic Thesis or Diss., Sorbonne université, 2019. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2019SORUS400.pdf.
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Dans de nombreux contextes développementaux, la formation d’un pli dans un épithélium est accompagnée d’un déplacement des tissus adjacents en direction de la zone d’invagination. Afin de tester l’idée d’un couplage entre un processus d’invagination et un flux tissulaire, nous avons étudié deux mouvements morphogénétiques qui surviennent durant la métamorphose de la drosophile : l’invagination de la frontière séparant la tête du thorax et un déplacement coordonné des cellules du thorax antérieur. En utilisant des techniques d’ablation laser ou de perturbations localisées de la contractilité de la Myosine II dans la région qui se plie, nous avons découvert que l’invagination de l’interface entre la tête et le thorax est un processus actif qui fournit une force de traction qui met localement en mouvement le thorax. Nous avons également découvert que le flux directionnel de thorax est en partie autonome, et qu’il peut être à l’origine d’une force de poussée active vers la zone d’invagination. Nous avons observé que le flux de thorax dépend d’une migration collective des cellules du thorax sur la matrice extracellulaire apicale. Cette migration s’appuie sur la sécrétion de la protéine Dumpy et sur des informations de polarité planaire. Nous avons montré in vivo que les régions thoraciques migrant activement sont spécifiquement associées à de faibles déformations de la matrice extracellulaire apicale. En conclusion, mes travaux de thèse mettent en exergue l’existence d’un nouveau mécanisme de couplage entre invagination et flux de tissu et illustrent l’importance de l’interaction entre le tissu et les matrices extracellulaires dans la mécanique et la morphogenèse épithélialesIn many developmental contexts, epithelial folding is accompanied by neighboring tissue flows towards the invagination site. To assess the idea of a long-range coupling between invagination and tissue flow, we have studied two macroscopic morphogenetic events happening during Drosophila metamorphosis: the invagination of the head-to-thorax boundary and the anterior dorsal thorax flow. Using large-scale laser ablations or locally disrupting MyosinII contractility in the invaginating region, we have found that head-thorax interface invagination is an active process which is providing a pulling force locally driving thorax flow. However, we have discovered that thorax flow is also partly autonomous, and thereby can actively provide a pushing force towards the invagination site. Using forward genetic methods, we have uncovered that thorax flow rely on collective migration on the apical extracellular matrix (ECM), depending on the secretion of the ZP protein Dumpy and on planar polarity cues. We have furthermore shown in vivo that regions of active thorax migration are specifically associated with low apical ECM deformation. Taken together, my PhD work uncovers a new mechanism coordinating tissue folding and tissue flow, and emphasizes the importance of tissue-matrix interaction in epithelial mechanics and morphogenesis
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Wiechel, Björn. "”Inte en plats som smörar för en” : En kvalitativ intervjustudie med människor i åldern 25-40 om valet att bo på Holmön." Thesis, Umeå universitet, Institutionen för geografi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-178432.
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This study seeks to illuminate the reasons to and consequences of the decision to choose Holmön as place for settlement for people in the age 25-40. The Island of Holmön, outside of Umeå in northern Sweden, has for decades experienced a depopulation. But in the last years several people in the age 25-40 – a phase of life often characterized by labour market establishment and starting a family – have moved to Holmön. What are their relationship to the island and what are the implications of the move for their life situation? Previous research of rural migration and counterurbanization find that lifecycle aspects, amenities on the countryside and lifestyle are important for the movers. Their connection to the place and having a bigger city in the vicinity also influence their choice. Semistructured interviews of eight people carried out by the author were analyzed with the help of thematic method. The results show that most important to them, in choosing to live on Holmön, is the quality of life given by the beautiful nature and idyllic environment, and somewhat by the feeling of adventure. Housing, employment, connection and social network, service and infrastructure are all factors of significance to their choice. The positive community feeling was attractive and meaningful to them aswell. Furthermore, their biggest concern, and what moreover possibly could force them to move away again, is the lack of childcare and schools on Holmön. The study suggests this migration to be regarded as amenity migration within the region of Umeå since the proximity to Umeå has such importance to the movers.
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Laver, Peter Norman. "Cheetah of the Serengeti Plains: A home range analysis." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/45981.
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Cheetah (Acinonyx jubatus) persist under continued conservation threat in small populations mostly in protected areas in an historically reduced geographic range. Home range, a useful trait for threat assessment, species reintroduction, and population estimation, is plastic in cheetah with sizes ranging from 40 km2 to over 1000 km2 depending on location. Previous home range estimates for cheetah used the minimum convex polygon (MCP), assuming asymptotic home ranges and MCP insensitivity to sample size. They reported metrics of home range size and overlap based on only outline methods. I use 6 481 observations of 240 female and 315 male cheetah from > 60 matrilines over 25 years in the Serengeti Plains to investigate lifetime, core, yearly, and seasonal range size with kernel density estimation. I investigate autocorrelation using time to statistical independence of locations. I confront the assumption of asymptotic home ranges by testing the traditional and multiscaled home range predictions and provide a novel method for determining kernel asymptotes. I challenge the notion of Serengeti cheetah as a migratory carnivore with analyses of site fidelity and objectively defined core ranges. I assess year to year and seasonal location shifts, showing that yearly shifting lessens as females age. I provide quantitative evidence for philopatry in female- and juvenile dispersal in male cheetah of the Serengeti Plains. I use simple overlap metrics to show that overlap in lifetime and core ranges is greater in related than unrelated female pairs. I use multi-response permutation procedures (MRPP) to show that overlap in unrelated female pairs varies with season. I use correlation of utilization distributions to show that avoidance is apparent only in unrelated pairs of females. My results call into question previous MCP estimates of cheetah home range size, and provide guidance for future sampling of cheetah locations. My home range results will guide management of this imperiled species and my methodological findings may be general and applicable to a wide range of taxa.Master of Science
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Sarret, Yves. "Contribution à l'étude de la réépithélialisation des plaies : analyse de la migration kératinocytaire in vitro." Lyon 1, 1993. http://www.theses.fr/1993LYO1T194.
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Decante, Damien. "Répartition spatio-temporelle et migration de la cicadelle verte (Empoasca vitis Goethe) dans un agro-écosystème viticole." Bordeaux 2, 2007. http://www.theses.fr/2007BOR21405.
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L'éco-éthologie de Empoasca vitis a été étudiée dans le vignoble à différentes échelles temporelles (semaine, génération, année) et spatiales (parcelle, ilôt de production, appellation). Elle hiverne dans les abords des parcelles sur des plantes à feuillage persistant et migre vers des plantes hôtes intermédiaires (complémentation), avant de coloniser les parcelles au printemps. Le niveau des populations estivales (potentiellement nuisibles) est influencé par des migrations estivales de longue distance. Les répartitions intra-parcellaires des adultes et larves, cartographiées et comparées avec les caractéristiques agronomiques des parcelles, révèlent de fortes agrégations dans les zones vigoureuses. La présence de plantes-hôtes alternatives de E. Vitis aux abords des parcelles (supplémentation) ne semble pas augmenter les populations. L'effet régulateur des auxiliaires en provenance des abords n'a pas été démontré. Une végétation haute et dense induit l'accumulation des adultes migrantsThe eco-ethology of Empoasca vitis was studied in vineyards at different temporal (week, generation, year) and spatial (plot, production site, small region) scales. This leafhopper hibernates near the plot on evergreen plants and, in spring, migrates towards different early-budding plants before ilmmigrating into the plots (complementation). Summer population levels (sometimes harmful) depend strongly on summer migrations taking place over longer distances. The intra-plot distribution of both adults and nymphs was mapped and compared to agronomical parameters. This revealed strong aggregations in areas of high plant vigour. The presence of potential alternative host plants of E. Vitis along the plot border (supplementation) did not seem to increase population levels. No impact of natural enemies from plot borders was detected. High and dense plot borders were shown to induce accumulation of migrating adults
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Ferrandon, Mireille. "Pénétration foliaire et migration des oligoéléments Fe, Zn et Mn, au niveau de cuticules isolées et sur plantes entières (Pisum sativum L)." Grenoble 1, 1988. http://www.theses.fr/1988GRE10101.
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Boyle, Alice. "Why do Birds Migrate? The Role of Food, Habitat, Predation, and Competition." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195068.
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The ultimate causes of bird migration are largely unknown despite more than a century of research. By studying partially migratory short-distance tropical migrants and by employing comparative methods, some difficulties in testing hypotheses for evolution of migration can be overcome. Using comparative methods I tested the evolutionary precursor hypothesis, a major hypothesis for why migration evolved in some lineages and not in others. The results of this study conflicted with many assumptions and predictions of the evolutionary precursor hypothesis. Most importantly, migratory behavior was not related to diet and habitat in simple ways. The interaction between diet and habitat, as well as consistent associations between flocking behavior and migration suggested that food variability is poorly captured by the surrogates embodied in the evolutionary precursor hypothesis. I then employed comparative methods to studying tropical altitudinal migration. Comparisons of diets and fruit preferences between species pairs showed that migrants are more frugivorous, eat a broader diversity of fruits, and have diets that more strongly resemble their preferences than do residents. Although providing evidence that food limitation plays a role in altitudinal migration, these results do not support the hypothesis that interspecific competition explains variation in migratory behavior. Next, I provided the first test of a predation-based hypothesis to explain altitudinal migration. Migrants breed at higher elevations than where they spend their non-breeding season. Thus, birds may migrate uphill to escape high nest predation risk at lower elevations. Results from this experimental study are largely consistent with this hypothesis, but anomalies between predicted and observed patterns suggest that either migration of lowland birds occurs in response to other factors, or that anthropogenic change has altered the tradeoffs involved in migratory decisions. Finally, I focus on a single migrant species and evaluate (a) two food-based hypotheses to explain the destination of migration movements, and (b) mechanisms underlying intra-specific differences in migratory strategy. Food can explain why Corapipo altera migrate uphill, but not why they migrate downhill. My data on sex bias and body condition leads to a new hypothesis explaining the complete annual cycle of this tropical migrant bird.
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Lee, Eunjee. "Impacts of meteorology-driven seed dispersal on plant migration : implications for future vegetation structure under changing climates." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69469.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 164-169).
As the impacts among land cover change, future climates and ecosystems are expected to be substantial (e.g., Feddema et al., 2005), there are growing needs for improving the capability of simulating the dynamics of vegetation structure across the global landscape as accurately as possible. In order to serve these needs, Dynamic Global Vegetation Models (DGVMs) are used to describe the current status of vegetation structure and biogeography as well as estimate their future dynamics, either with prescribed climates or coupled to climate models. Yet, current DGVMs generally assume ubiquitous availability of seeds and do not generally consider seed dispersal mechanisms and plant migration processes, which may influence the impacts of vegetation structural changes on the climate system (i.e., change in albedo, runoff, and terrestrial carbon sequestration capacity). For the first time, this study incorporates time-varying winddriven seed dispersion (i.e., the SEED configuration) as a dynamic constraint to the migration of natural vegetation in the Community Land Model (CLM)-DGVM. Compared to estimates of satellite-derived tree cover, simulations by this model configuration shows significantly improved representation of boreal forests in Western Siberia and temperate forests in Eastern Europe. The prevailing wind pattern, along with the existing vegetation structure in nearby grid cells, alters the competition dynamics of the trees in these regions by filtering unrealistic plant functional types through adjustment of establishment rates. The SEED configuration was applied to project future vegetation structures under two climate mitigation scenarios (No-policy vs. 450ppm CO 2 stabilization) for the 21st century. The simulation results indicate that regional changes of vegetation structure under changing climates are expected to be significant. In the high latitudes, regions such as Alaska and Siberia are expected to experience substantial shifts of forestry structure, characterized by expansion of needle-leaf boreal forest and shrinkage of C3 grass Arctic. In the mid-latitudes, temperate trees are likely to expand in South America, South Africa, and East Asia at the expense of C3 grass during the latter part of the 21' century. In the Tropics, the most notable degree of change is in the composition of tropical trees and C4 grasses in the Amazon and in Africa.
(cont.) The vulnerability assessment suggested by this study shows that vegetation structures in Alaska, Greenland, Central America, southern part of South America, East Africa and East Asia are susceptible to changing climates, regardless of the two climate mitigation scenarios. Regions such as Greenland, Tibet, South Asia and Northern Australia, however, may substantially alleviate their risks of rapid change in vegetation structure, given a robust greenhouse gas stabilization target. The impacts of future vegetation change on radiation budget cannot be neglected. The results of this study suggest that depending upon the climate mitigation scenarios, vegetation change may enhance or mitigate the anticipated warming trend of the 21St century. Proliferation of boreal forests in the high latitudes to amplify the warming trend (i.e., a positive feedback to climate) if no mitigation policy is implemented. In contrast, under the 450ppm scenario, changes in vegetation structure may reduce the rate of warming, which is a negative feedback to climate. A series of hydrologic processes including interception of rainfall by forest canopy, evapotranspiration, and runoff are also influenced by modifications in vegetation structure. The magnitude of the runoff response by the vegetation change is not projected to exceed the direct response of hydrology to climate change (i.e., changes in precipitation); however, the spatial pattern of changes in runoff associated with vegetation changes indicates that vegetation change may in some regions offset or lessen increases in runoff due to enhanced precipitation under climate warming. Reduction of terrestrial productivity and a conservative estimate of vegetation carbon storage (-8PgC/yr and 24PgC, respectively under the no policy scenario) in the 21st century may be due to ignoring the CO₂ fertilization effect and partially applying the new SEED configuration to project future vegetation structures. The SEED configuration developed in this study may serve to more comprehensively represent future vegetation structure across the global landscape and therefore may provide a tool to better assess the impacts of natural vegetation dynamics on the climate system. This model configuration may also provide outputs that can be used to assess the impacts of climate change on the goods and services that ecosystems provide to society.
by Eunjee Lee.
Sc.D.
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Lopez, Sébastien. "Fardeau de mutation, fardeau de dérive et fardeau de migration dans des populations fragmentées de plantes : approches théoriques." Montpellier 2, 2007. http://www.theses.fr/2007MON20167.
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Hemmati, Carin. "En plats för mig : En studie om migranters väg in i församlingen i Equmeniakyrkan, Region Stockholm." Thesis, Enskilda Högskolan Stockholm, Avdelningen för religionsvetenskap och teologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ths:diva-1362.
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En inventering, analys och tolkning av de faktorer och omständigheter som är avgörande för migranter, varför de tillhör den församling de gör. Studien genomfördes med intervjuer av medlemmar i två mångkulturella församlingar inom Equmeniakyrkan i Region Stockholm.
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Yatagan, Baumeister Deniz [Verfasser], and R. [Akademischer Betreuer] Rambow. "Effects of Migration on Children’s Private and Social Places / Deniz Yatagan Baumeister ; Betreuer: R. Rambow." Karlsruhe : KIT-Bibliothek, 2021. http://d-nb.info/1238148158/34.
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Wolters, Rachel M. ""We Heard Canada Was a Free Country": African American Migration in the Great Plains, 1890-1911." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1483.
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This study uses a transnational lens to examine the migration of Black Americans from Oklahoma to Canada in the early 20th century. Although scholars have documented this movement, they have not fully explored the vital and durable transnational connections among African American immigrants themselves. The use of family histories, newspaper articles, and immigration files show how black migrants searched for land and equality in Canada and attempted to build all black communities. Encouraged by the promises of Canadian immigration recruiters, black migrants left their homes and Jim Crowism in Oklahoma to settle in a “free country” and to realize the goals of American citizenship in a foreign land. But, Canada wanted white—not black—American settlers and immigration officials closed to African Americans the once porous boundary between the U.S. and Canada. Canadian authorities recognized the power of transnational connections among black migrants in promoting migration and settlement and, ironically, by effectively sabotaging that network, they ensured that African Americans had to abandon their quest for equality and opportunity in Western Canada.
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Lardeux, Laurent. "De l'exil au retour : dispositifs de rapatriement et carrières migratoires des retournés congolais (RDC)." Thesis, Lyon 2, 2011. http://www.theses.fr/2011LYO20124.
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A l'interface de la sociologie des migrations et de la sociologie politique, la thèse porte sur les migrations de retour des réfugiés congolais à partir des principaux pays d'acceuil l'afrique centrale. loin d'être regardées dans une perspective linéaire et statique entre deux sédentarités mais analysées à partir d'observation in situ et d'entretiens biographiques réalisés pendant près de seize mois dans les espaces d'accueil et de retour, les migrations de retour son intégrées ici dans un espace migratoire dynamique fait d'oppositions et de transactions entre les dispositifs du flux migratoire qui organisent et réglementent les migrations de retour, et les multiples pratiques formelles et informelles du sujet dont les intenses jeux de tension s'inscrivent dans un contexte soutenu de limitation des flux migratoires et l'accroissement de nouvelles formes de mobilité dans l'espace migratoire d'afrique centraleIn the interface of the sociology of migration and political sociology, the thesis focuses on return migration of Congolese refugees from the main host countries of central Africa. Far from being observed in a linear and static perspective between two sedentarinesses but analyzed starting from in situ observations and from biographical interviews conducted during 16 months in host and return areas, the migrations of return are integrated in a dynamic migratory space constituted by oppositions and transactions between the biopolitic plans of retention of flows and the circulatory practices of the refugees. The accent is particularly focused on negotiating "biographical crossroads" and migratory careers of refugees from the social, spatial and political capital acquired during the refuge time. How, in these intersections between migratory careers and biopolitical plans, the returnees can define and negotiate their installations in the environment of return ?
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Gustafsson, Astrid. "Staying in Niue? : Students' spatial plans related to value systems and climate change." Thesis, Uppsala universitet, Kulturgeografiska institutionen, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387608.
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The Niuean population has been in decline since the airport opened on the island. This thesis investigates a specific aspect of the migration from the island: what final year high school students in Niue plans to do after graduation in relation to leaving or staying in Niue. The study relates this decision to place attachment, values and climate change.The study indicates that Niuean youth doesn’t want to study on the island but instead move to New Zealand to pursue their academic ambitions. The students exhibit a strong sense of place attachment that is based in their identification with the island culture and nature. They want to return to the island after getting their university degree, making them attached stayers. The risk of cyclones does not affect the students wishes to live on the island. Decisions are in large motivated by caring for family, the students want to get a degree and then return to be able to take care and give back to their parents, grandparents and other people that have cared for them during their childhood.
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Johansson, emanuel, and Petter Wikström. "Att avvika från det urbana : En studie kring flyttmotiv & känslan efter flytten till en landsbygdskommun från en urban kommun." Thesis, Karlstads universitet, Institutionen för geografi, medier och kommunikation (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-72798.
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Det urbana betraktas ofta som en norm, studien syftar till att lägga ett fokus mot landsbygden och studera berättelser från de som flyttar från stad till land. Där studien baseras på att undersöka flyttmotiv i kontext till migrantens liv före och efter flytten. Studien har ämnat att besvara vad det är som påverkar upplevelser av platser före- och efter flytt, vilka motiv som kan påverka personer att vilja flytta samt vad som kännetecknar den som flyttar till landsbygden. Den tidigare forskningen i studien bygger huvudsakligen på en bred genomgång av migrationsforskning. Forskning som behandlar ämnet migration har försökt förstå vilka faktorer som påverkar människors val att flytta. Studien utgår från ett humanistiskt perspektiv då vi vill komma åt informanternas berättelser och upplevelser av både den gamla och nya platsen. Där studien genomförts med en kvalitativ metod bestående av semistrukturerade intervjuer. Intervjuerna genomfördes i Värmland som är studiens geografiska avgränsning och informanterna kommer från fyra olika landsbygdskommuner. Sammantaget genomfördes tio intervjuer med tolv informanter. Empirin är baserad på de tre teman som ingick i intervjuguiden - bakgrund och erfarenheter, motivet och platsen. Detta för att komma åt informanterna berättelser om varför de flyttat samt hur de upplevt/upplever den gamla och den nya platsen. I diskussionsdelen sammanvävs empirin med den tidigare forskningen. Där framkommer skilda motiv till flytt samt berättelser om hur informanterna upplever det urbana och landsbygden före och efter flytt. Studiens slutsats uttrycker, övergripande, informanternas upplevelser av en bättre vardag på landsbygden med mer livskvalite såsom lägre levnadsrytm, mindre stress och större närhet till natur. Det lyfts fram hur det kan tolkas att den urbana miljön bidrar till en undanträngningseffekt och hur landsbygden som plats är socialt annorlunda jämfört med staden. Där landsbygden ses som mer välkomnande och med mer spontant umgänge.The urban area is seen as the norm today, this study aims to focus on the countryside and study the stories from those who move from the city to the countryside. Where the study is based on examining moving motives in context to the migrant's life before and after the move. The study is intended to answer what is affecting experiences of places before and after moving, which motives can affect people wanting to move and what characterizes the person who moves to the countryside. The previous research in this study is mainly based on a broad review of migration research. Research that deals with the subject of migration has tried to understand which factors affect people's choices to move. The study starts from a humanistic perspective as we want to access the informants' stories and experiences of both the old and the new place. Where the study was conducted with a qualitative method consisting of semi-structured interviews. The interviews were conducted in Värmland which is the study's geographical delimitation and the informants come from four different rural municipalities. Overall, ten interviews were conducted with twelve informants.The empirical data is based on the three themes that were included in the interview guide - background and experiences, motive and place. This is to access the informants' stories about why they moved and how they experienced/experiencing the old and the new place. In the discussion section, the empirical data is interwoven with the previous research. Where there are different motives for moving and stories about how the informants experience the urban and rural areas before and after the move. The study's conclusion expresses, overall, the informants' experiences of a better everyday life in the countryside with more quality of life such as lower life rhythm, less stress and greater proximity to nature. It is emphasized how it can be interpreted that the urban environment contributes to a displacement effect and how the rural as a place is socially different from the city. Where the countryside is seen as more welcoming and with more spontaneous interactions.
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Valença, Maria Cibele de Oliveira Ramos. "Migração entre planos de benefícios: alteração da proteção previdenciária privada." Pontifícia Universidade Católica de São Paulo, 2013. https://tede2.pucsp.br/handle/handle/6114.
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Previous issue date: 2013-05-06The focus of this study is to analyze the migration process between benefit plans managed by the closed private pension and verify the possibility of maintaining the standard of living of its participants and, consequently, for their welfare after the completion of migration. The private pension scheme is voluntary and based on reserve to ensure the benefit hired, being characterized by the intention to supplement the benefits provided by the statutory system, ensuring the maintenance of the participants standard life when they retire and stop perform paid activities. This paper consists of five parts. The first part deals with the Social Security System and its purposes. The second part assesses the main features inherent to a private pension scheme, including submission to the principles of the Social Security System and the analysis of the subjects that operationalize within the closed pension. The third part deals with the legal nature of the closed private pension, important to complete this work behold directs the purpose of the private system. The fourth section analyzes the legal technicalities of financial schemes used by closed private pension funds in the creation and management of benefit plans that aim to ensure future comfort to its participants. Finally, the fifth part, are considered the legal aspects of benefit plans, as well as the ownership of their respective assets and other aspects that must be considered in a migration process between benefit plans devised by sponsors. The research is important because it will allow conclusions about the relevance of this change specifically in relation to social security protection of participants who originally joined the benefits plan other than the one that will pay benefits in the future
O foco deste estudo é analisar o processo de migração entre planos de benefícios geridos por entidades fechadas de previdência privada e verificar a possibilidade de manutenção do padrão de vida dos seus participantes e, consequentemente, do seu bem-estar social após a concretização da migração. O regime de previdência privada é facultativo e baseado na constituição de reservas que garantam o benefício contratado, sendo caracterizado pelo propósito de complementar os benefícios oferecidos pelo regime oficial, garantindo a manutenção do padrão de vida dos participantes no momento em que se aposentam e deixam de exercer atividades remuneradas. O presente trabalho é composto por cinco partes. A primeira parte versa sobre o Sistema de Seguridade Social e suas finalidades. A segunda parte avalia as principais características inerentes ao regime de previdência privada, incluindo a submissão aos princípios do Sistema de Seguridade Social e a análise dos sujeitos que a operacionalizam no âmbito da previdência fechada. A terceira parte trata da natureza jurídica das entidades fechadas de previdência privada, aspecto importante para a conclusão deste trabalho, uma vez que direcionará a finalidade do regime privado. A quarta parte analisa os aspectos técnicos jurídicos dos regimes financeiros utilizados pelas entidades de previdência privada fechada na criação e gestão dos planos de benefícios que almejam garantir conforto futuro aos seus participantes. Por fim, na quinta parte são considerados os aspectos jurídicos dos planos de benefícios, bem como a titularidade de seus respectivos patrimônios e os demais aspectos que devem ser considerados em um processo de migração entre planos de benefícios idealizados pelos patrocinadores. A investigação é relevante pois permitirá concluir a respeito da pertinência dessa alteração especificamente em relação à proteção previdenciária dos participantes que originalmente aderiram a um plano de benefícios distinto daquele que pagará seus benefícios no futuro
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Nettleton, Benjamin. "The role of vegetation-topographic interactions in a barrier island system: island migration in a changing climate." VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5572.
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Islands have been characterized based on vegetation and topography as exhibiting different disturbance regimes - reinforcing or resisting. This study had two objectives: quantify barrier island upland migration and vegetation cover change over 32 years (1984-2016), and assess tolerance of two prevalent dune grass species, A. breviligulata, and S. patens to sand burial. Using Landsat imagery from the Virginia Coast Reserve, islands were categorized within the disturbance resistance/reinforcing framework based on dune elevation. Resistant areas were associated with woody cover and low marsh to upland migration while reinforcing areas had low vegetation cover and high rates of migration. System-wide, migration rates increased over time and large losses of upland and marsh, paired with expansions of woody cover occurred. In the field, each grass species was subject to repeated burials. S. patens was able to maintain biomass and height in high rates of burial, whereas A. breviligulata did not survive.
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Forsberg, Sverker. "Behaviour of ¹³⁷Cs and ⁹⁰Sr in agricultural soils : influence of ageing and soil type on availability, migration and plant uptake /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5735-1.pdf.
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Zakrzewski-Sharma, Karan. "PLANT MIGRATION AT THE END OF THE WEICHSELIAN GLACIATION : Macrofossil evidence of early coniferous trees at two northern Swedish sites." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160214.
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Studies of vegetation history bring a new incentive to our understanding of plant survival and migration in arctic environments. For decades, environmental research was based on palynological data and these studies created a notion that tree species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris) did not grow in northern Scandinavia at the end of Weichselian glaciation. However, findings of macro- and megafossils of these trees dating back to glacial times has been reported in the Swedish mountain range, questioning this view of a late arrival of these trees in Scandinavia. The apparent contrasting views on the composition of the first plants arriving to Scandinavia create uncertainties about the bioclimatic conditions prevailing at the end of the Weichselian glaciation. To improve our understanding about the first vegetation arriving to Scandinavia I probed the macrofossil composition of two novel sedimentary records from northern Sweden. Twelve sediment cores from material underlying Holocene peat deposits were used as archives of early Holocene plants. In these records, I found: I) larch needles dating back to 4.6 and 4.1 calibrated thousand years (cal. kyr) BP; II) pine macrofossils dating back to 9.5 and 8.7 cal. kyr BP; III) fossils from dwarf shrubs (willow and heather) dating back to 9.9 cal. kyr BP; and IV) a birch fossil dating back to 9.5 cal. kyr BP. Also found in the same depth was fragment of a spruce cone. Based on my findings, I concluded that the landscape behind the retreating Weichselian ice-sheet was surpassingly colonised by pine and larch trees, a forest that has no contemporary analogue in Scandinavia. It seems as if this early forest also contained spruce, which is enigmatic as the main spruce invasion is expected to occur across the region during the next millennia. Finally, there is an instigation for future discussion on how our present knowledge of plant behaviour in changing conditions can help minimise the impacts of ever-expanding climate change.
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Butler, Martin. "Voices of the down and out the dust bowl migration and the great depression in the songs of Woody Guthrie." Heidelberg Winter, 2006. http://d-nb.info/985228660/04.
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Duong, Hanh Bich. "The Hmong girls of Sa Pa : local places, global trajectories, hybrid identities /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6481.
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Smith, Christopher. "From the Plains to the Plateau: Indian and Emigrant Interactions During the Overland Trail Migrations." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/18365.
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American emigrants frequently encountered Native North Americans during the overland trail migrations of the 1840s-1860s. This study examines the frequency and nature of those interactions in two geographic sections: the first half of the trail, from the Missouri River to the eastern slope of the South Pass of the Rocky Mountains, and the second half, from the western slope of South Pass to Oregon City, Oregon. While the predominant historiography of these migrations has focused on a binary of hostile or non-hostile interactions between Indians and emigrants, the focus on violence has obscured the larger issue of frequent and amicable interactions between emigrants and Indian peoples along the overland route. Factors such as trade, the availability of resources, and cultural differences influenced the nature of these inter-ethnic interactions, which varied from the beginning of the trail on the Plains to the end of the trail on the Columbia Plateau.