Дисертації з теми "Selective dispersion"
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Boegelein, Thomas. "Selective laser melting of a ferritic oxide dispersion strengthened steel." Thesis, University of Liverpool, 2014. http://livrepository.liverpool.ac.uk/2010620/.
Повний текст джерелаLathdavong, Lemthong. "Development of diode laser-based absorption and dispersion spectroscopic techniques for sensitive and selective detection of gaseous species and temperature." Doctoral thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-43799.
Повний текст джерелаJossent, Mathieu. "Développement de fibres optiques à dispersion contrôlée pour l'élaboration de lasers ultrarapides à 2 µm." Thesis, Limoges, 2017. http://www.theses.fr/2017LIMO0016/document.
Повний текст джерелаThe goal of this PhD thesis is to pave the way towards the demonstration of parabolic amplification at 2 μm in an all-fiber format. The physical theory on self-similar pulse amplification is first presented. The best all-fiber amplifier at 2 μm would need a special Tm-doped fiber with both high normal dispersion and large effective area. Parabolic amplification is however prohibited in silica based singlemode fiber working at 2 μm due to the large anomalous dispersion of silica. To overcome this limitation, a four-mode fiber in which the LP02 mode exhibits high normal dispersion combined with large effective area at 2 μm was designed and manufactured. A dedicated mode converter has also been designed and manufactured. Using the spatially- and spectrally-resolved imaging technique the purity of excitation of the LP02 mode in the passive fiber was evaluated to 99.9%. An ultrashort pulse (100 fs) source tunable from 1.6 μm to 2 μm was implemented to seed the amplifier. This source allowed to measure the LP02 mode dispersion of the passive fiber at the wavelength of 1.95 μm: D = -106 ps/(nm.km) in excellent quantitative agreement with the simulations. Numerical modeling of a nonlinear amplifier based on the realized active fiber shows that MW peak power class pulses centered at 1.9 μm can be obtained at the output of the parabolic amplifier
Jensen, Jordan Royce. "Development of Tau-Selective Imaging Agents for Improved Diagnosis of Alzheimer’s Disease and Other Tauopathies." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1306441097.
Повний текст джерелаKomaki, Ghorbanmohammad. "PORTFOLIO SELECTION AND RISK DISPERSION BASED ON GEOMETRIC DISPERSION THEORY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1512232304419177.
Повний текст джерелаGil-Díaz, Teba. "Comportement biogéochimique d’antimoine (Sb) et de tellure (Te) dans le milieu côtier : vers des scénarios de dispersion des radionucléides de Sb et de Te en cas de rejets accidentels de centrales nucléaires (projet AMORAD, ANR-11-RSNR-0002)." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0004/document.
Повний текст джерелаAntimony (Sb) and tellurium (Te) are relatively uncommon contaminants (stable isotopes) and may form short-lived fission products (radionuclides) released into the environment during nuclear power plants accidents. Little is known about their respective biogeochemical behaviours, necessary for general contamination studies and post-accidental radiological risk assessment.This work provides original knowledge on Sb and Te biogeochemical behaviour in highly dynamic continent-ocean transition systems: the Gironde Estuary and the Rhône River. Concentrations, spatial/temporal variations, solid/liquid partitioning (Kd), and fluxes are studied from long-term records at the watershed scale. Four estuarine sampling campaigns during contrasting hydrological conditions show higher Sb solubility and Te particle affinity in the estuary than in the upstream fluvial reaches. Historical records (1984-2017) in wild oysters from the estuary mouth do not show clear trends of past or recent contamination, but measurable bioaccumulation suggests that potential uptake of radionuclides is likely to occur. Combined adsorption experiments using isotopically-labelled (spiked) Sb and Te, and subsequent selective extractions of carrier phases from suspended particulate matter (SPM) suggest that spiked Sb and Te are more mobile and potentially bioaccessible than their environmental (inherited) equivalents. Radiotracer adsorption experiments using environmentally representative concentrations of both Gironde and Rhône systems underpin that highly soluble elements may show contrasting reactivity between inherited and spiked forms.Radionuclide dispersion will greatly depend on (i) the geographical position of the source (Rhône) and/or the maximum turbidity zone (MTZ; Gironde fluvial-estuarine system), (ii) the succession of hydrological situations during and after the accident, and (iii) the biogeochemical reactivity and half-lives of the radionuclides. First scenarios on hypothetical dissolved radionuclide dispersion in the Gironde Estuary suggest (i) low sorption of Sb to the SPM, implying a transport of radionuclides in dissolved phase towards the coast, and (ii) high retention of Te within the MTZ, especially for accidental releases during flood conditions, linking the fate of radioactive Te to long estuarine SPM residence times (1-2 years). Potential upstream migration of Te radionuclides in the MTZ towards the city of Bordeaux during the following summer season and Te decay into radioactive iodine warrants further evaluation of the associated potential radiotoxicity
Brengdahl, Martin. "Differentiation of dispersive traits under a fluctuating range distribution in Asellus aquaticus." Thesis, Linköpings universitet, Biologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-108119.
Повний текст джерелаZhong, Yuan. "Sub-grain structure in additive manufactured stainless steel 316L." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-144519.
Повний текст джерелаAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.
Gandar, Benoît. "Apprentissage actif pour l'approximation de variétés." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2012. http://tel.archives-ouvertes.fr/tel-00954409.
Повний текст джерелаPalmberger, Anna. "Regularization parameter selection methods for an inverse dispersion problem." Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-184296.
Повний текст джерелаProchazková, Zdeňka. "Numerické modelování šíření zvuku pomocí diferenčních metod." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231394.
Повний текст джерелаDonnelly, Conor Michael. "Rationalising the selection of pharmaceutical excipients for the formulation of amorphous solid dispersions." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680168.
Повний текст джерелаRae, Stuart. "Individual dispersion and productivity of ptarmigan in relation to their selection of food and cover." Thesis, University of Aberdeen, 1994. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=216420.
Повний текст джерелаAnderson, Jessica Thornley. "The Effect of Navigation State Selection on Fuel Dispersions for Powered Lunar Descent." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/2004.
Повний текст джерелаLefranc, Agnès. "Etude des facteurs determinant les comportements de dispersion et de selection de l'habitat chez drosophila melanogaster." Paris 6, 2001. http://www.theses.fr/2001PA066139.
Повний текст джерелаPachai, Kannu Arun. "Communications over noncoherent doubly selective channels." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1173887288.
Повний текст джерелаCordeiro, Erick M. G. "Patterns of infestation, dispersion, and gene flow in Rhyzopertha dominica based on population genetics and ecological modeling." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32642.
Повний текст джерелаDepartment of Entomology
James F. Campbell
Thomas W. Phillips
Movement is a fundamental feature of animals that impacts processes across multiple scales in space and time. Due to the heterogeneous and fragmented nature of habitats that make up landscapes, movement is not expected to be random in all instances, and an increase in fitness is an expected consequence for those that can optimize movement to find valuable and scarce recourses. I studied the movement of Rhyzopertha dominica (Coleoptera: Bostrichidae), one of the most important pests of stored grain worldwide, within and between resource patches. At a fine spatial scale, I identified factors that contribute to overall and upward movement in the grain mass. Three-week-old insects tented to stay closer to the surface than one or two-week-old insects. Females tended to be more active and to explore more than males. I also found that males tended to stay closer to the surface than females and that might be related to the ability to attract females from outside the patch since there was no significant difference regarding female’s attraction within the grain patch. Interaction with feeding sites or other individuals of the same sex creates positive feedback and a more clumped spatial pattern of feeding and foraging behavior. On the other hand, interaction with individuals of different sex creates negative feedback and a more random or overdispersed pattern. At a broad spatial scale, I studied the long-term consequence of R. dominica movement on the development of population structure within the U.S. To evaluate population structure, I used reduced representation of the genome followed by direct sequencing of beetles collected from different locations across the U.S where wheat or rice is produced and stored. Ecoregions were more important in explaining structure of R. dominica populations than crop type. I also found significant isolation by distance; however, model selection primarily elected grain production and movement variables to explain population differentiation and diversity. Understanding animal movement is essential to establishing relationships between distribution and surrounding landscape, and this knowledge can improve conservation and management strategies.
Thomson, R. L. (Robert L. ). "Breeding habitat selection and its consequences in boreal passerines:using the spatial dispersion of predators and heterospecifics as a source of information." Doctoral thesis, University of Oulu, 2006. http://urn.fi/urn:isbn:9514280504.
Повний текст джерелаFort, Thomas. "Effet du paysage sur la structure des communautés fongiques foliaires." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0266/document.
Повний текст джерелаPlant leaves host a large diversity of microorganisms. Among the factors shaping foliar microbial community structure, the effect of the dispersal process remain understudied. Landscape elements, such as edges or landscape heterogenity, influence migration and dispersal of many macro-organism species. However, the effect of such factors on foliar microbial communities has never been studied. We hypothesized that forests are a source of foliar fungi for adjacent vineyards. We compared foliar and airborne fungal communities in vineyard and adjacent forests along a vegetative season, we examined the effect of a forest edge on these communities in a vineyard, and weassessed the effect of landscape composition on these communities. Fungal communities were characterized with a metabarcoding method. Foliar fungal communities in vineyards and forests diverge over the course of the vegetative season. Neither the distance to the edge nor the proportion of forest in the landscape affect foliar fungal communities in vineyards, while airborne communities change with the distance to the forest edge. These results suggest that dispersal is not dominant in shaping foliar fungal communities. Instead, many selective pressures such as agricultural practices seem to shape strongly these communities. Further investigations are required in order to estimate the relative contribution of those processes, and the potential ecosystem service provided by the forest to crops
Lagrange, Paméla. "Déterminants de la survie et de la dispersion de reproduction par une approche capture-marquage-recapture chez l'Hirondelle bicolore au Québec." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS077/document.
Повний текст джерелаIn North America, monoculture areas using high inputs of fertilizers and pesticides cover 85% of agricultural lands, and as many pastures disappeared in the past 20 years to satisfy human food needs. These land-use changes have deeply transformed landscapes and altered the biodiversity of agro-ecosystems. Among farmland birds, aerial insectivores such as Tree swallow, Tachycineta bicolor, studied here show a high rate of decline in their abundance, partly reflecting the degradation of agro-ecosystems where they breed. Biological mechanisms leading to the decline and dispersal patterns in migratory passerines are still poorly known. The present work quantifies the environmental effects on Tree swallow individual traits (survival, reproductive success) and breeding dispersal (probability to disperse and occupation rates of breeding sites). Between 2004 and 2013, 2200 breeders and 8000 chicks were ringed and monitored during 10 breeding seasons on a study area composed of 40 sites and covering a mosaic of heterogeneous agricultural landscapes in southern Québec. The development of a new, flexible capture-mark-recapture model has reduced estimate bias of survival and dispersal probabilities of Tree swallows. This approach allowed to assess the effect of several variables linked to habitat quality, public information and individual characteristics on dispersal, survival and reproductive success parameters of individuals. Within intensively cultivated landscapes associated to the presence of a nest site competitor, the House sparrow, Passer domesticus, male survival is up to 19% lower. Females are affected by the cost of reproduction, especially in intensive landscapes where House sparrows and found and where food resources and nest site appear limited. Dispersal probability is not affected by environmental conditions either through the presence of House sparrows or habitat quality, and is restricted to 4% in males. Females, which disperse up to 14 times more than males, base their decision on their personal experience. Breeding failure increases up to 7 times the probability to disperse and for the first time in a short-lived species, I show that dispersal likelihood increases if the individual has dispersed in the previous year. These dispersal patterns are stable in time. Dispersal appears as a costly process compared to site fidelity and is a minority phenotype in the population. It appears an answer to unfavorable condition for reproduction. Finally, this work shows the use of public information (partners density, fledglings productivity the previous year) on the decision to settle on a site and this, after the dispersal decision has been initiated. The presence of House sparrows and the proportion of intensive areas near nestboxes are used as information to select a breeding site. Based on my findings, agricultural intensification likely plays a role in the decline of Tree swallow populations
Lagrange, Paméla. "Déterminants de la survie et de la dispersion de reproduction par une approche Capture-Marquage-Recapture chez l’Hirondelle bicolore au Québec." Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6855.
Повний текст джерелаAbstract : In North America, monoculture areas using high inputs of fertilizers and pesticides cover 85 % of agricultural lands, and as many pastures disappeared in the past 20 years to satisfy human food needs. These land-use changes have deeply transformed landscapes and altered the biodiversity of agro-ecosystems. Among farmland birds, aerial insectivores such as Tree Swallow, Tachycineta bicolor, studied here show a high rate of decline in their abundance, partly reflecting the degradation of agro-ecosystems where they breed. Biological mechanisms leading to the decline and dispersal patterns in migratory passerines are still poorly known. The present work quantifies the environmental effects on Tree Swallow individual traits (survival, reproductive success) and breeding dispersal (probability to disperse and occupation rates of breeding sites). Between 2004 and 2013, 2200 breeders and 8000 chicks were ringed and monitored during 10 breeding seasons on a study area composed of 40 sites and covering a mosaic of heterogeneous agricultural landscapes in southern Québec. The development of a new, flexible capture-mark-recapture model has reduced estimate bias of survival and dispersal probabilities of Tree Swallows. This approach allowed to assess the effect of several variables linked to habitat quality, public information and individual characteristics on dispersal, survival and reproductive success parameters of individuals. Within intensively cultivated landscapes associated to the presence of a nest site competitor, the House sparrow, Passer domesticus, male survival is up to 19 % lower. Females were affected by the cost of reproduction, especially in intensive landscapes where House sparrows and found and where food resources and nest site appear limited. Dispersal probability was not affected by environmental conditions either through the presence of House sparrows or habitat quality, and was restricted to 4 % in males. Females, which dispersed up to 14 times more than males, based their decision on their personal experience. Breeding failure increased up to 7 times the probability to disperse and for the first time in a short-lived species, I show that dispersal likelihood increased if the individual had dispersed in the previous year. These dispersal patterns were stable in time. Dispersal appeared as a costly process compared to site fidelity and was a minority phenotype in the population. It appeared an answer to unfavorable condition for reproduction. Finally, this work shows the use of public information (partners density, fledglings productivity the previous year) on the decision to settle on a site and this, after the dispersal decision had been initiated. The presence of House sparrows and the proportion of intensive areas near nest boxes were used as information to select a breeding site. Based on these findings, agricultural intensification likely plays a role in the decline of Tree swallow populations.
Varela, Susana Araújo Marreiro. "Animal decision-making for habitat and mates : the selection of breeding commodities through inadvertent social information and its consequences for the evolution of coloniality." Paris 6, 2007. http://www.theses.fr/2007PA066668.
Повний текст джерелаBaudouin, Alice. "Rôles relatifs des facteurs démographiques, sociaux et sélectifs sur la sélection de partenaires reproducteurs chez le gorille des plaines de l'ouest." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1B057/document.
Повний текст джерелаIn many species, it has been shown that strategies of choice of socio-sexual partners by an individual are related to the phenotypic or genetic quality of these partners and are likely to maximize the quality of its descendants and improve its own fitness. We investigated the partner choice in western lowland gorilla females in studying their social dispersion and the relative influence of the social environment and the characteristics of adult males in females’ decisions, to stay in a social group or to emigrate, and in their choice of the group into which immigrate. We showed that females preferentially migrated towards breeding groups rather than solitary males and towards younger rather than aging groups. Groups of 10-15 individuals were avoided. Females emigrated from groups containing a large proportion of individuals affected by skin disease. In the short term after a demographic die-off due to an Ebola epidemic, female’s emigration rates declined in large groups, suggesting better reproductive and protective value of surviving males. The influence of the genetic characteristics of the sexual partners in the choice of females, in particular the genes of the major histocompatibility complex (MHC) genes that encode proteins involved in immune defenses, may be involved in partner choice in some primates. Its possible involvement had never been studied in the gorilla. In this perspective we have sought to develop a method to study this gene complex from non-invasive DNA samples (feces), that is to say with weakly concentrated and degraded DNA. We defined a new primer and then used high throughput sequencing, denaturing gradient gel electrophoresis, and a MHC-linked microsatellite marker to determine a population-level analysis method. Eight new MHC alleles were detected by high throughput sequencing. The microsatellite marker has a complex amplification pattern and requires protocol optimization that will reduce the cost of analyzing MHC variability at the population level. Our developments open new perspectives for the study of the influence of CMH on partner choice in wild populations of primates
Acker, Paul. "Life-history decisions of larids in spatio-temporally varying habitats : where and when to breed." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30024/document.
Повний текст джерелаThroughout their lifetime, individuals face two decisions which have major consequences on the reproductive success: where and when to breed. This thesis explores the mechanisms underlying these decisions through three studies based on individual monitoring data in the black-legged kittiwake (Rissa tridactyla) and the slender-billed gull (Chroicocephalus genei). The first study addresses hypotheses on dispersal in the kittiwake. The probability of leaving the nest site is sequenced according to the hierarchical structure of habitat patches. A synthetic hypothesis that integrates the costs of dispersal and the use of information on habitat quality is suggested to explain the strategy of habitat selection. The second study uses a population integrated model in the kittiwake to estimate immigration, recruitment, and intermittent reproduction. This study investigates the relationships between social information on the habitat and the decision to breed in a population which is located at the edge of the species range. The third study focuses on recruitment and dispersal in the slender-billed gull which is characterized by a high degree of nomadic breeding. Multievent capture-recapture models are used to quantify sex- and age-dependent variations. These examples enable to address how important the constraints of habitat variability and intraspecific competition are in the process of obtaining a breeding position
Teichert, Nils. "Variabilité des traits d’histoire de vie chez les Gobiidae (Sicydiinae) amphidromes de l’île de la Réunion : Sicyopterus lagocephalus (Pallas, 1770) et Cotylopus acutipinnis (Guichenot, 1863)." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3024/document.
Повний текст джерелаAmphidromous Sicydiinae are particularly widespread among fish freshwater assemblages of the Indo-Pacific region and are vulnerable to anthropogenic pressures (i.e. fishery, degradation and fragmentation of habitats). Spawning and hatching happen in freshwater, then offspring drift downstream to the sea where they begin their growth for a few months before recruiting in the rivers. This study aims at acquire knowledge about life traits of S. lagocephalus (cosmopolite) and C. acutipinnis (endemic). Field sampling shows that the usual habitat choice is related to social interactions, whereasspawning habitat shows a strong selection for morphodynamic conditions which favor eggs oxygenation. Males select spawning sites and care for the eggs. The experimental study of freshwater survival confirms that free embryos survival and swimming capacities are enough to drift to the ocean. Marine life history analysis, based on postlarvae otoliths examination, reveals a seasonal variation of both age and size-atrecruitment related to the larval growth rate and the sea temperature. Histological examination of ovaries is used to describe the spatial and temporal variation of reproductive activity of mature females in the rivers, and to determine fecundity and size at first reproduction. Inter and intra-specific variations of life history traits are compared in relation to the respective geographical distribution of both species. This study identifies concrete prospects for management and conservation based on the features of amphidromous life history strategy
Nobre, Andrezza Bellotto. "Chuva de sementes zoocóricas em uma floresta de Mata Atlântica em processo de restauração: caracterização e fatores de influência." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11150/tde-26032013-165713/.
Повний текст джерелаThe need to reverse the current degradation of the Atlantic Forest requires urgent restoration actions aimed at reestablishing biodiversity in these areas, involving various plant and animal life forms and their interactions. The reestablishment of plant-frugivore interactions and subsequent seed dispersal are essential not only for the conservation of an existing forest, but also for the acceleration of forest restoration processes. Therefore, seed dispersal agents should be employed in restoration actions. One way to assess animals\' contribution in seed dispersion is through the study of seed rain, more specifically through results of dispersal events by fauna (zoochory). This study aimed to characterize and compare the composition of animal-dispersed seed rain in an area of the Atlantic Forest undergoing a restoration process using two different management techniques. One area comprised of tree planting and another comprising a \"capoeira\" through assisted natural regeneration. We also used an Akaike information criterion of model selection tool to evaluate whether structure and composition variables of arbustive-arboreal vegetation influenced the richness and abundance of total and immigrant animal-dispersed seed rain. The study was conducted in an area undergoing a forest restoration process with six years of age, covering 28.86 ha of the Intermontes Farm (24°11\'17\"S, 42°24\'49\"W; 24°12\'47\"S, 42°26\'15\"W), near Ribeirão Grande city, São Paulo State, Brazil. Propagules deposited in traps were removed monthly for a period of one year. We used 100 seed collectors 1 m x 1 m. To characterize the vegetation in the region, we surveyed the arbustive-arboreal species in a 5-meter radius around each seed collector. The results showed that the community composition of the animal-dispersed seed rain differed between tree planting and \"capoeira\" environments; however, the richness and abundance averages of seeds did not differ significantly between the environments. Although the community composition was different, functional categories of seeds in the rain in both areas were similar. Assessing whether there was influence of variables related to structure and composition of arbustive-arboreal species on animal-dispersed seed rain, generated and selected models indicated that these variables did not influence the richness and abundance of total and immigrant animal-dispersed seed rain. The results also showed the presence of alien propagules in the region, demonstrating great potential for the growth of new species belonging to other life forms with different ecological functions. This allows the acceleration of forest restoration processes, increased structural complexity of vegetation and contribution to heterogeneity of deployed forest, which is important for the return and increase of animal dispersers.
Weber, Alexandra. "Etude écologique et génétique du complexe d'espèces cryptiques Ophioderma longicauda (Ophiuroidea : Echinodermata) : comparaison entre lignées incubantes et lignées produisant des larves planctoniques." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4002/document.
Повний текст джерелаOphioderma longicauda (Bruzelius, 1805) is a cryptic species complex including six mitochondrial lineages (L1-L6), of which three (L2-L3-L4) brood their juveniles, whereas the other lineages most likely reproduce using lecithotrophic larvae. In order to define the species limits in the O. longicauda complex, the reproductive status of lineages L1 and L3 was studied. The morphological and genetic study showed that they were different biological species, with notably different reproductive periods. In addition, the analysis of 31 genetic markers using DAPC showed that the O. longicauda complex included six distinct genetic groups. Secondly, the influence of life-history traits on connectivity and genetic diversity was studied. To do so, 10 markers were sequenced for six sympatric populations of lineages L1 and L3 from Greece. The genetic structure was high for the brooding species, whereas the broadcasting species did not display any genetic structure at that scale. The analysis of genetic diversity for these 10 markers showed that diversity was three to four times higher in broadcasters than in brooders. In addition, the analysis of genetic diversity in the L1 and L3 transcriptomes showed that diversity was 1.5 to 2 times higher in broadcasters than in brooders. Finally, two ion channels involved in sperm motility showed an evolution under positive selection. These results suggest that sperm competition might be a mechanism of pre-zygotic isolation in Ophioderma longicauda
Personne, Arnaud. "Dynamique du modèle de Moran en environnement aléatoire." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC102.
Повний текст джерелаIn some ecosystems and more particularly in virgin tropical forests, different species having the same ecological requirements coexist in the same environment. For example, some forests have over a hundred different tree species on one hectare. To explain this incrediblediversity, scientists have built models in which the community composition isonly due to the stochastic dispersion of individuals.The mathematical model studied in this thesis follows this line. It was suggested by Mr. Kalyuzhni in an article where he justifies its relevance. It is known as the Moran model in random environment. It is therefore a question of studying a birth and death process taking into account the environmental stochasticity (climates, diseases, etc.) To study this dynamic, we use an approximation by a diffusion, on the classical scale where the acceleration in time is given by the square of the population size, moreover selective advantage and immigration are inversely proportional to thethis size. The selective advantage varies randomly and is modeled by a Markov jump process. We study the convergence in law of the processes sequence and give a quantitative estimate of the error made for a given population. We are then interested in the moments estimation of the population frequencies, motivated in particular by biodiversity indices such as the Simpson's index andbased on the approximations obtained before.In the case of a non-zero selection, the stochastic differential equation governing a moment appeals to the higher order moment. To overcome this difficulty, we create a closure method to reduce the study of the first moments to a finite system of differential equations. We give an estimation of the error made by neglecting the terms of higher degrees. Finally, in the case of two species and with constant coefficients, we give an estimate of the convergence speed of the diffusion towards the stationary measure. In a second time, we are interested in a time scale proportional to the size of the population. This leads to a convergence of the process law towards a deterministic limitcharacterized by an ordinary differential equation. The selection coefficient evolving randomly, still following a Markov jump process, this process is a PDMP.We then study the persistence of the different species and the potential coexistencethanks the persistence theory, developed by Benaïm and Schreiber. In this part, we are particularly interested in the case where all the species persist. With only two environments: we show that two species can persist but not three. With more environments,the explicit classification stay an open problem but an example of persistence with three speciesand three environments is given
Ragon, Marie. "Diversité et processus de colonisation microbienne sur des substrats minéraux." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00636619.
Повний текст джерелаBestion, Elvire. "Impact du changement climatique sur un vertébré ectotherme : de l'individu à la communauté." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30389.
Повний текст джерелаRecent global change has dramatic impacts on biodiversity, through modifications in abiotic and biotic factors. Species vulnerability to changing climates depend for instance of its habitat, its position within the community and its thermal physiology. In this respect, ectotherm species are considered particularly vulnerable as their body temperature depend directly on their environment. We experimentally studied the impact of future climate change on an ectotherm vertebrate species, the common lizard (Zootoca vivipara). We used the Metatron, a system of semi-natural enclosures in which climatic conditions can be manipulated. We studied the impact of warmer climatic conditions (+2°C) on common lizard's population dynamics and extinction risk, and on population adaptation capacity through plasticity, selection and dispersal. We further investigated the impact of climate change at the community scale. We demonstrated that future climatic conditions pose a threat to common lizard. However, possibilities of adaptation exist through changes in phenology and physiology (preferred temperature and melanism). Finally, we show that changing climatic conditions have an impact on the entire communities, from plants and insects to microbial communities
Perez, Florent. "Plasmons dans un potentiel unidimensionnelEtude par spectroscopie Raman de fils quantiques gravés." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1998. http://tel.archives-ouvertes.fr/tel-00285443.
Повний текст джерелаNous avons cherché à déterminer la contribution de la forte illumination dans les conclusions précédentes. Nous avons utilisé pour cela la spectroscopie de magnéto-transmission infra-rouge qui ne modifie pas les conditions d'équilibre du gaz d'électrons. Une largeur critique de 130 nm a été extraite, en dessous de laquelle nous n'avons plus aucun signe de la présence d'électrons libres. La comparaison des mesures Raman et infra-rouge a permis l'établissement et la validation d'un modèle microscopique du potentiel de confinement présent dans les fils. Enfin nous avons fabriqués des échantillons de géométries plus complexes. L'observation et l'analyse par diffusion Raman des plasmons dans ces fils a montré que nous pouvions contrôler la géométrie du potentiel confinant les électrons et a mis en évidence des effets nouveaux tels que le repliement et le confinement de plasmons unidimensionnels.
Matteucci, Scott Tyson 1976. "Gas transport properties of reverse selective nanocomposite materials." Thesis, 2007. http://hdl.handle.net/2152/3631.
Повний текст джерелаSin-RuHuang and 黃欣如. "Study on the alignment and selective dispersion of carbon nanotubes within polymeric liquid phases and thin film." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/67bfxf.
Повний текст джерела國立成功大學
材料科學及工程學系
105
In this research, liquid phases of Poly(9,9-di-n-octylfluorenyl-2,7-diyl)(PFO) and Poly(methyl methacrylate)(PMMA)are developed in Toluene solution. By changing the compositional ratios, concentration, length of polymer side chain in solution, the morphology and two- phase distribution of spin- coated thin films are discussed. According to the pi-pi interaction between conjugated polymer and carbon nanotubes, we have observed the selective distribution of carbon nanotubes within PFO liquid phase. On spin-coated thin film, we’ve also observed the alignment of CNTs is further influenced by the stacking of PFO crystalline lamellae. The orientational alignment of CNTs could be developed at specific temperature and specific diameter of CNTs. When PFO is replaced by Poly (9, 9-di-n-dodecylfluorenyl-2,7-diyl) (PF12), the flow of liquid phase at selected temperatures is motivated to form rectangular board-like domains. CNTs are found to align vertically in PF12 domains in order to maintain the interactions with the matrix of PF12.
Wu, Chung-Ching, and 吳重境. "The Selective Dispersion Effect of Single-wall Carbon Nanotubes with Difference Diameter and Block Polymer with Hydrophobic Segments." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/uef789.
Повний текст джерела國立臺灣科技大學
化學工程系
107
Soft electronics require not only high electronic performance but also stretchable and flexible properties. Currently used in organic materials for soft electronic components, carrier mobility is poorer than traditional solid-state components. Therefore, the development of materials with tensile properties and high carrier mobility is currently the trend of research. Single-walled carbon nanotubes have the potential to be used in soft electronic components due to their tough but flexible physical properties and excellent electronic properties. However, single-walled carbon nanotubes have different conductive properties due to their structural changes, therefore the purification of single-conductor single-walled carbon nanotubes is very important for subsequent applications. Based on the method of conjugated polymer selective dispersion of single-walled carbon nanotubes, it is hoped that a standard procedure for purifying single-walled carbon nanotubes can be established. Different diameters of single-walled carbon nanotubes and different conjugated polymers were selected as research objects. To explore the mechanism of selective dispersion of single-walled carbon nanotubes. In Chapter 2, we used the conjugate polymer, polyfluorene and polythiophene, which are commonly used to selectively disperse single-walled carbon nanotubes, For dispersing single-walled carbon nanotubes with larger diameters. The single-walled carbon nanotubes obtained after selective dispersion have diameters of 1.42 nm and 1.74 nm. After the preparation of the field effect transistor, the analysis exhibited semiconducting properties, and the obtained carrier mobility was 4.21×10-2 cm2/(s×V). We tried to explain why PFO can sort relatively larger diameter of single-wall carbon nanotubes which is comparing with the reference. In Chapter 3, the effect of van der Waals force between single-walled carbon nanotubes and conjugated polymers is the object we want to study. It is first necessary to confirm whether the established process can be applied to single-walled carbon nanotubes with smaller diameters. Similarly, a conjugated polymer such as polyfluorene or polythiophene is used to selectively disperse carbon nanotubes with smaller diameter. Several kinds of chirality of semiconducting single-walled carbon nanotubes were confirmed by the photoluminescence result. The prepared transistor on/off current ratio reached 104, and the carrier mobility reached 9.95×10-2 cm2 /(s×V). After confirming the feasibility of the process, a block polymer containing a long hydrophobic chain was introduced to study the effect of different van der Waals strength on the selective dispersion of single-walled carbon nanotubes. From the results of UV/VIS/NIR, it was found that the longer the hydrophobic segment has higher selectively dispersion of the single-walled carbon nanotube. It has also been found from the photoluminescence result that different hydrophobic segment lengths also have different dispersing ability for the same chirality of carbon nanotubes.
Wang, Po-I., and 王柏翊. "Novel Functional Conjugated Polymers and Polynorbornenes with Nanographenes: Synthesis and Applications for Photoluminescence, Electrochromism and Highly Selective Dispersion for Semiconducting Single-Walled Nanotubes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/68528002956554020979.
Повний текст джерела國立臺灣科技大學
化學工程系
104
First of all, conjugated polymers, poly(phenylene-fluorene) P1 and poly(triphenylbenzene-fluorene) P2 with hexaphenylbenzene (HPB) as pending side group were prepared through Suzuki coupling. The HPB moiety of P1 and P2 can be oxidatively cyclodehydrogenated with FeCl3, yielding polymer P3 and P4 with hexa-peri-hexabenzocoronene (i.e., nanographene) units. The cyclodehydrogenation of P3 and P4 was confirmed by FT-IR spectroscopy and X-ray powder diffraction of P3 and P4 both revealed the size of nanographene approximately 1.3 nm. The glass transition temperatures (Tg) of P1 and P2 were 202 °C and 235 °C, respectively. Both P3 and P4 with nanographenes possessed Tg higher than 300 °C. Compared to P3, P4 with triphenzlbenyene moiety in backbones can be well dispersed without aggregation in N-Cyclohexyl-2-pyrrolidone (CHP), confirmed by UV-Vis absorption spectroscopy, photoluminescence spectroscopy (PL) and photoluminescence-excitation (PLE) maps. The second section, a new triphenylamine-alt-fluorene based conjugated copolymer, HPBPYFL6, with hexaphenylbenzene (HPB) and pyrene as asymmetrical pendant groups was synthesized. HPBPYFL6 possessed a high glass transition temperature at 260 °C and a 10% weight-loss temperature at 503 °C. HPBPYFL6 bearing a pyrene moiety had a solvatochromic fluorescence shift from a green to orange emission as the polarity of the solvent increased. Conjugated polymer films exhibited reversible electrochromic behaviour with a colour change from pale yellow to deep blue upon electrochemical oxidation and high absorbance in the near-infrared (NIR) region. The strong NIR electrochromic absorbance of HPBPYFL6 was attributed to intervalence charge transfer by the incorporation of the HPB moiety. Furthermore, the electrochromic mechanism was interpreted by DFT calculation and the simulated NIR electrochromic spectra of model compound HPBPYFL are in a good agreement with experimental data. The third part, a new approach for polytriarylamine (PTAA)-assisted selective dispersion for single-walled carbon nanotubes (SWNTs) in toluene solution has been developed. The triarylamine-based conjugated polymers are able to selectively wrap the SWNTs with specific chiral indices depending on their backbone structures (e.g., PTAA12, PTAA12-P and PTAA12-BP) and side-chain functionality (e.g., PTAA6, PTAA6-alt-PTAA and PTAA12-alt-PTAA). PTAA12 exhibits highly selective wrapping for the (6,5) chirality from CoMoCAT SWNTs but low selectivity in a dispersion of HiPCO SWNTs. Therefore, the selection for HiPCO SWNTs has been further improved via PTAA12-alt-PTAA wrapping with alternating side chains, which exhibits high affinity to (6,5), (7,5) and (9,8) chiralities. The limited conformations of PTAA12-alt-PTAA were due to incorporation of alternating side chains, which enhanced the selectivity of extraction of SWNTs. Finally, the saturated polynorbornene Poly(HNBOHPB) with a hexaphenylbenzene (HPB) moiety was prepared by ring-opening metathesis polymerization (ROMP) followed by hydrogenation. The nanographene-containing Poly(HNBOHBC) was prepared from Poly(HNBOHPB) via the Scholl reaction. The glass transition temperature of Poly(HNBOHPB) was 205 °C, and that of Poly(HNBOHBC) was higher than 300 °C. The temperatures required for a 10% weight loss (Td10) for Poly(HNBOHPB) and Poly(HNBOHBC) were 428 °C and 456 °C under a nitrogen flow, respectively, indicating the great improvement in thermal properties after the cyclodehydrogenation.The exfoliation of insoluble Poly(HNBOHBC) was prepared by bath sonication in CHP. The spectroscopic features of Poly(HNBOHBC) were investigated by UV-vis spectroscopy, fluorescence spectroscopy and photoluminescence excitation (PLE) mapping.
Mweene, Levie. "Polymer-based investigations into the surface chemistry of some sulphide minerals and the beneficiation of a low grade siliceous copper ore." Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4774.
Повний текст джерелаGovernment of India (GoI) through the Ministry of Human Resource Development (MHRD)
Toews, Sergej [Verfasser]. "Corrosion protection by selective addressing of polymer dispersions to electrochemical active sites / von Sergej Toews." 2010. http://d-nb.info/100977865X/34.
Повний текст джерелаLai, Shih-Tsun, and 賴世存. "Single-Carrier Frequency Domain Equalization Joint Carrier-Selection Over Dispersive MISO Channels." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/09439983339897799915.
Повний текст джерела中原大學
電機工程研究所
97
The wireless communication systems have investigated over the recent years, the demand for data rates are more than before. Hence, the multiple input multiple output (MIMO) technique has been proposed to increase data rates by using several transmit and receive antennae. Of particular interset is multiple input single output (MISO) system where the base station (BS) equipped with multiple antennae sends its data to mobile units which possess a single receive antenna, which often employed in downlink mobile communications. However, in high data rate communications, the impacts of multipath propagation and intersymbol interference (ISI) have been increased and the resulting required equalizer. The equalizer is generally performed in time domain. However, with growing data rates the complexity of time domain equalizer (TDE) structures increases hugely. A process to overcome this problem is using single carrier frequency domain equalizer (SC-FDE). Since the convolution sequence in the time domain translate into product under frequency domain. Therefore, the FDE has lower computational complexity than TDE. Beside, in this thesis, under the MISO system, we propose a novel design, the carrier selection (CS) in the transmit-end, and the SC-FDE is applied at the receiver-end over dispersive Nakagami-m fading channels. Simulation results reveal that our proposed scheme is much greater than that without CS and other conventional coun- terparts and we find bit error rate (BER) performance limitation by various system parameters. Moreover, about the FDE, we will discuss the characterizations for two common strategies of the linear equalizer, zero-forcing (ZF) and minimum mean square error (MMSE).
Paixão, Susana Mónica Marinho. "Recolha seletiva: um balanço de energia e recursos face à dispersão geográfica - estudo caso: concelho de Coimbra e concelho da Figueira da Foz." Doctoral thesis, 2017. http://hdl.handle.net/10316/32383.
Повний текст джерелаO presente estudo desenvolveu-se através da análise dos dados acerca das ”quantidades de resíduos” provenientes da recolha seletiva dos ecopontos dos concelhos de Coimbra e Figueira da Foz do Distrito de Coimbra e dos “quilómetros percorridos” para a recolha desses resíduos e encaminhamento para a estação de triagem. Os anos em estudo foram de 2009 a 2013 e os dados anteriormente referidos foram obtidos através da consulta do sítio da internet da ERSUC, empresa gestora dos resíduos urbanos. Por outro lado, com a informação recolhida da tipologia dos camiões de recolha e do ano de matrícula, recorreu-se ao programa COPERT IV para obter as quantidades de CO2 emitidos por fluxo de resíduos, tendo conseguido fazer um balanço, recorrendo ao software do site norte americano STOPWASTE. Com esta calculadora, e fazendo as adaptações necessárias à realidade portuguesa, conseguimos calcular a quantidade de CO2 que se deixa de emitir para a atmosfera ao fazer a reciclagem das quantidades de resíduos recolhidos. De referir que foi usada a percentagem de 6% como taxa de refugo, segundo os dados obtidos através da ERSUC. Assim, verificou-se que temos um balanço muito positivo no que respeita às quantidades de CO2 que são poupadas com a reciclagem dos resíduos provenientes dos ecopontos comparativamente com a quantidade de CO2 emitido com a sua recolha e encaminhamento para a estação de triagem. É certo que no presente estudo não foram contemplados os quilómetros percorridos e as consequentes emissões de CO2 com o transporte da estação de triagem para as empresas recicladoras. Por outro lado, o presente estudo permitiu chegar à conclusão que também conseguimos poupar energia ao reciclarmos os materiais recolhidos, quando comparamos com a energia que é gasta com a recolha e transporte destes mesmos materiais. This study was developed by analyzing the data "quantities of waste" from the selective collection of waste recycling bins, for the municipalities of Coimbra and Figueira da Foz the district of Coimbra and "mileage" for such waste and referral to the station screening. The years in the study were from 2009 to 2013 and previously reported data were obtained through the Internet site of the ERSUC, company wich managing municipal waste. On the other hand, with the information collected from the type of truck collection and year of registration, he used the COPERT IV program to obtain the quantities of CO2 emitted with a waste stream and managed to take stock, using the site's software north American STOPWASTE. With this calculator, and making the necessary adjustments to the Portuguese reality, we can calculate the amount of CO2 that is allowed to emit into the atmosphere when you recycle the quantities of waste collected. Note that the percentage of 6% as scrap rate was used, according to data obtained by ERSUC. Thus it was found that we have a very positive with regard to the quantities of CO2 are saved with the recycling of waste from ecopoints compared to the amount of CO2 emitted to the collection and forwarding to the screening station. It is true that in this study the mileage and consequently CO2 emissions with transportation screening station at recycling companies were not included. Furthermore this study has lead to the conclusion that we can also save energy by recycling the collected materials, when compared to the energy that is spent on the collection and transport of these same materials. KEYWORDS: Municipal waste, selective collection, balance, Coimbra
This study was developed by analyzing the data "quantities of waste" from the selective collection of waste recycling bins, for the municipalities of Coimbra and Figueira da Foz the district of Coimbra and "mileage" for such waste and referral to the station screening. The years in the study were from 2009 to 2013 and previously reported data were obtained through the Internet site of the ERSUC, company wich managing municipal waste. On the other hand, with the information collected from the type of truck collection and year of registration, he used the COPERT IV program to obtain the quantities of CO2 emitted with a waste stream and managed to take stock, using the site's software north American STOPWASTE. With this calculator, and making the necessary adjustments to the Portuguese reality, we can calculate the amount of CO2 that is allowed to emit into the atmosphere when you recycle the quantities of waste collected. Note that the percentage of 4% as scrap rate was used, according to data obtained by ERSUC. Thus it was found that we have a very positive with regard to the quantities of CO2 are saved with the recycling of waste from ecopoints compared to the amount of CO2 emitted to the collection and forwarding to the screening station. It is true that in this study the mileage and consequently CO2 emissions with transportation screening station at recycling companies were not included. Furthermore this study has lead to the conclusion that we can also save energy by recycling the collected materials, when compared to the energy that is spent on the collection and transport of these same materials.
Rudolph, Tyler. "Spring dispersal and habitat selection of boreal caribou (Rangifer tarandus caribou) in Northern Quebec." Mémoire, 2011. http://www.archipel.uqam.ca/5272/1/M12089.pdf.
Повний текст джерелаChen, Chung-De, and 陳宗德. "Direct phase selection of initial phases from single-wavelength anomalous dispersion (SAD) for the improvement of electron density and ab initio structure determination." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/72037628454826989080.
Повний текст джерелаLawonn, Matthew James. "Breeding ecology and nest site selection of Kittlitz's murrelets on Kodiak Island, Alaska." Thesis, 2012. http://hdl.handle.net/1957/36245.
Повний текст джерелаGraduation date: 2013
Rautenbach, Helperus Ritzema. "An empirically derived system for high-speed rendering." Thesis, 2012. http://hdl.handle.net/2263/28196.
Повний текст джерелаThesis (PhD)--University of Pretoria, 2012.
Computer Science
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