Tesi sul tema "Eels"
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1
Larkin, Brendan, e mikewood@deakin edu au. "The weaning and growth of Anguilla australis glass eels and elvers". Deakin University. School of Ecology and Environment, 2000. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20060713.113837.
Testo completoAbstract (sommario):
Anguilla australis glass eels proved to be resilient and present strong aquaculture potential. General husbandry techniques, anaesthesia and prophylactic treatments were established for glass eels between 0.1 g and 2.0 g and elvers between 2.0 g and 8.0 g, caught in rivers and estuaries along the South East Coast of Victoria. The protozoan parasites Ichthyobodo and Trichodina were found to be present on arrival to the hatchery developed during different rearing treatments, and were successfully eradicated. A. australis glass eels accepted artificial food, but it was recommended first be fed a preweaning diet of minced fish flesh. A weaning regime from minced fish flesh to commercially available eel grower mash, over 15 days was established. Growth rate proved to be highly variable, both between and within groups. The highest growth rate of 2.71%/day was found when the natural diet of minced fish and Artemia was fed. The maximum growth rate when reared on an artificial diet of 1.63%/day was observed at 25°C. Growth was affected by the presence or absence of a preweaning diet, weaning diet, weaning period, temperature, but not by size or density. Once weaned, glass eels were found to perform better on commercially available grower mash than on the minced fish flesh, which was used to aid in weaning them to artificial diets. Of the water quality parameters measured stocking density was found to affect pH, Total Ammonia Nitrogen, Total Phosphorus, and Dissolved Oxygen, through not to an extent which affected growth.
2
Birrell, Lynne M. "Osmoregulation in glass eels and elvers of the European eel, Anguilla anguilla". Thesis, University of St Andrews, 1999. http://hdl.handle.net/10023/14934.
Testo completoAbstract (sommario):
Glass eels of the European eel migrate from coastal waters inland to freshwater as part of the catadromous lifecycle. The osmotic challenge faced at this time is augmented by their large surface area to volume ratio, and by the fact that the migration may only be completed after several attempts, due to the effects of tide and river flow. Glass eels and elvers developed normally when maintained in waters of differing salinity over a six month period. Drinking rates increased with environmental acclimation salinity (from 0.072 +/- 0.023 mul/g/h to 0.698 +/- 0.099 mul/g/h in FW and SW respectively), and freshwater acclimated fish exhibited a rapid drinking response upon contact with seawater. These accounts of dipsogenic behaviour are similar to those previously reported for adult eels. Results obtained from determinations of branchial Na+K+ATPase activities were more equivocal. Only after nearly five months were activities higher in SW (508.52 +/- 99.76 nmoles/Spairs gills/h) as compared to FW fish (151.65 +/- 8.9 nmoles/5pairs gills/h). Following the transfer of FW acclimated fish to SW there was a trend towards increased Na+K+ATPase activity after seven days post-transfer, which reached a significant peak after two months post-transfer. A transient increase in whole body cortisol content was noted following the transfer of fish from freshwater (388.02 + 90.38 pg/g) to seawater (6268.44 +/- 773.14 pg/g). However, it was not possible to ascertain that this was due to a direct effect of environmental salinity change. There were no clear changes in interrenal cell morphology between salinity groups, although the cells did appear reduced in size with time, regardless of environmental salinity. Total body Na+ content increased with time, and was higher in SW (58.66 +/- 1.66 mumoles/g) as compared to FW reared fish (44.85 +/-1.01 mumoles/g).
3
Kolodzie, Annette Therese. "EELS at dislocations in diamond". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615749.
Testo completo
4
Juergensen, Lars Stephen. "Tissue enzyme changes in air-exposed American eels". Thesis, University of Ottawa (Canada), 1997. http://hdl.handle.net/10393/4280.
Testo completoAbstract (sommario):
American eels (Anguilla rostrata) are known to leave the water for excursions onto land despite lacking specialized air breathing organs. Other studies have established that the eel suffers from acidosis and hypoxemia as a result of this air exposure, but the survival of the eels despite these conditions demonstrates a large degree of tolerance to these effects. This thesis will investigate the changes in tissue enzymes of the American eel as a result of air exposure. It is the hypothesis of this experiment that conditions of air exposure eels will undergo a metabolic reorganization including an initial Pasteur effect and metabolic depression indicated by changes in enzyme activities and metabolite concentrations. Eels were air exposed for 3, 5 or 10 days in boxes ensuring constant temperature and humidity. Maximal activities were determined in white muscle, gill and posterior kidney tissues harvested immediately following the particular air exposure period; as a result of technical difficulties, liver was unavailable for study. Enzymes assayed included those key in glycolysis (PFK, PK, LDH), glycogen metabolism (GPase and GSase) and gluconeogenesis (GDH, AspAT, AlaAT, and PEPCK). In addition, kinetic analysis was undertaken for PFK and PK in harvested posterior kidney. Blood collected at the time of harvest was analyzed for glucose, lactate and cortisol to determine circulating levels. Muscle samples were also analyzed for glycogen content. Although changes in enzyme rates, enzyme kinetics and metabolites were observed to result from the air exposure, it could not be concluded that the changes were part of a concerted metabolic depression.
5
Torruella, Besa Pau. "Development of novel EELS methods to unveil nanoparticle properties". Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/666906.
Testo completoAbstract (sommario):
[eng] The aim of this thesis has been two-fold. First, to develop new processing and analysis tools and strategies for extracting information from EELS data, and second, to apply the methods to different nanoparticle systems to shed light to relevant phenomena related to their synthesis and properties. In this regard, chapter 1 presented and overview of the EELS fundamentals and of the state of the art of the technique. Chapter 2 was focused on the advanced computational methods related to EELS data analysis. Moreover, the application of cluster analysis to EELS was introduced, showing its possibilities as an image segmenting and phase identification tool. The following chapters were devoted to the investigation of different material science problems related to NPs that take advantage of the capabilities of quantitative EELS.
The results were grouped by increasing complexity of the performed analysis, with chapter 3 devoted to characterizations that were mainly carried out using EELS elemental mapping, chapter 4 being related to ELNES analysis and chapter 5 to EELS tomography.
In chapter 2, the adaptation of data clustering algorithms to the analysis of EELS data, developed within the scope of the present thesis, has been undertaken.
In chapter 3.1 the organic synthesis of FeOx@SiO2 NPs was assessed. Several findings were obtained through the HRTEM, STEM-HAADF and EELS characterization of the FeOx@SiO2 NPs at different stages of its synthesis.
In chapter 3.2, concerning Au-Ag-Se and the Au-Ag-S system cation exchange reactions several findings were made.
Chapter 4 was devoted to the characterization of different NPs with an emphasis on the direct observation the oxidation state of its constituents through EELS. In chapter 4.1, the synthesis of MnOx/Fe3O4 core/shell NPs was assessed. In chapter 4.2, the measurement of oxidation state at atomic resolution in spinel crystals was proposed as a method to assess cation inversion in the crystal. The necessary methods were developed and applied to iron oxide/manganese oxide core/shell NPs.
Chapter 5 was devoted to the combination of EELS and tomography. In chapter 5.1 the synthesis of cobalt oxide/cobalt ferrite (CoO@CFO) core/shell NPs and cobalt oxide/manganese ferrite (CoO@MFO) NPs was investigated. Chapter 5.2 was focused on the achievement of an oxidation state-sensitive tomographic reconstruction.[cat] L’adveniment de la nanotecnologia està portant amb ell l’aparició d’una gran quantitat de nous materials, compostos i aplicacions. En el seu desenvolupament, sovint té lloc fenomenologia sorprenent, o encara no ben entesa. Per omplir aquest forats en el nostre coneixement i poder desenvolupar noves aplicacions és de vital importància esbrinar la configuració estructural i química a nivell subnanomètric d’aquests components. Per la seva gran resolució espacial, la microscòpia electrònica de transmissió ha esdevingut una eina indispensable en aquest context. A més, en un microscopi electrònic es poden combinar una gran varietat de tècniques que poden donar una quantitat d’informació enorme. Una d’aquestes tècniques és l’espectroscòpia de pèrdua d’energia dels electrons (EELS). Aquesta tècnica ha permès en els últims anys el mapejat d’elements químics i ions columna atòmica per columna atòmica, arribant a uns dels nivells més íntims als que es pot conèixer la matèria en estat sòlid. L’objectiu d’aquesta tesi ha estat fer ús de l’EELS i d’altres tècniques emprades en microscòpia electrònica per entendre els processos químics que tenen lloc en diferents síntesis de nanopartícules. En aquest procés s’han desenvolupat també una sèrie d’eines enfocades al processat de les dades d’EELS ja sigui per a facilitar la seva interpretació, limitar problemes derivats de la seva adquisició (i. e. soroll) o calcular propietats concretes del material estudiat. A més aquesta tècnica s’ha combinat amb mètodes de reconstrucció 3D per obtenir una informació completa dels sistemes estudiats.
6
Harkins, Paula. "EELS and ELNES : investigation of titanate and zirconate perovskites". Thesis, University of Glasgow, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425162.
Testo completo
7
Hildebrand, Heather. "Size, age composition, and upstream migration of American eels at the Millville Dam eel ladder, Shenandoah River, West Virginia". Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4377.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains vii, 54 p. : ill. (some col.). Includes abstract. Includes bibliographical references.
8
Norton, Jeremy. "Patterns and processes in helminth communities of eels (Anguilla anguilla)". Thesis, Royal Holloway, University of London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406531.
Testo completo
9
Miners, John Steven. "Geochemical controls on heavy metal accumulation in Thames Estuary eels". Thesis, Birkbeck (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406406.
Testo completo
10
Gonzalez, Reinaldo J. "Raman, Infrared, X-ray, and EELS Studies of Nanophase Titania". Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30605.
Testo completoAbstract (sommario):
Sol-gel titania particles were investigated, primarily by optical techniques, by systematically varying synthesis, sample handling, and annealing variables. The material phases investigated were amorphous titania, anatase TiO2, and rutile TiO2. Annealing-induced phase transformations from amorphous TiO2 to anatase to rutile were studied by Raman scattering, infrared reflectivity, infrared absorption, x-ray diffraction, and electron energy-loss spectroscopy (EELS). Detailed experiments were carried out on the effects of annealing on the Raman and infrared spectra of anatase nanocrystals. The frequencies of the zone-center transverse optical (TO) and longitudinal-optical (LO) phonons of anatase were determined and were used in analyzing the results obtained on composites consisting of annealed solgel particles.
The TO and LO frequencies of anatase were obtained from polarization-dependent far-infrared reflectivity measurements on single crystals. These results, which determined the dielectric functions of anatase, were used to explain infrared (IR) reflectivity spectra of titania nanoparticles pressed into pellets, as well as the grazing-incidence IR reflectivity observed for titania thin films. Because of the polycrystalline character of the titania nanoparticles, the surface roughness of the pressed pellets, and the island-structure character of the thin films, effective-medium theories (appropriate for composites) were used, along with the anatase dielectric functions, to interpret the experimental results.
The titania nanoparticles were prepared by the hydrolysis/condensation of Ti(OC2H5)4. A polymeric steric stabilizer was used in the sol-gel synthesis in order to prevent continued agglomeration during the condensation process. This yielded particles with a relatively narrow size distribution. The amount of water used in the reaction determines the final particle size. Particles as small as 80 nm and as large as 300 nm were used throughout this work. From the colloidal suspension, loose powders, pressed pellets, and thin films were formed. These samples were subjected to different annealing processes at temperatures ranging from room temperature up to 1000 C. Two different annealing atmospheres were used: air (oxygen-containing) and argon (no oxygen).
The amorphous to anatase transformation was followed by in-situ IR transmission measurements carried out during annealing. The particles as prepared are amorphous and the anatase phase could be detected, using this sensitive IR technique, at temperatures as low as 150 C. This phase transition was shown to be particle size dependent. It was also shown that introducing the stabilizer by means of the alkoxide flask instead of the water flask (during the sol-gel synthesis) decreases the anatase to rutile transformation temperature. Loose powders were found to transform more readily than dense pellets, while island-structure films were found to be the hardest to transform. Even at 1000 C, most of these films did not transform to rutile.
X-ray diffraction experiments were used to determine nanocrystal sizes in anatase samples obtained by air and argon anneals at temperatures from 300 to 800 C. A correlation was found between Raman band shape (peak position and linewidth) and crystallite size, but this correlation was different for air anneals and for argon anneals. These experiments called for an interpretation based on a stoichiometric effect rather than a finite size effect. Based on this interpretation, the as-prepared particles are slightly oxygen-deficient, with a stoichiometry corresponding to TiO1.98.
In the electron energy-loss experiments, a special data-analysis technique was used to extract the EELS spectrum of the titania nanoparticles from the observed substrate-plus-particles signal. This technique successfully resolved the titania absorption-edge peak. Which was found to be momentum independent. For low electron momentum, the results were consistent with the reported optical absorption edge.Ph. D.
11
Monier, Etienne. "Reconstruction rapide d'images multi-bandes partiellement échantillonnées en spectromicroscopie EELS". Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0090.
Testo completoAbstract (sommario):
En spectroscopie de perte d’énergie des électrons (EELS), l’échantillon à analyser est soumis à un faisceau d’électron et une détection de l’énergie perdue au cours de la traversée du matériau renseigne sur la composition chimique du composé. Pour des échantillons particulièrement sensibles aux dégâts d'irradiation électronique, comme par exemple des matériaux organiques, on cherche à limiter la dose totale d'électrons reçue par l'échantillon tout en obtenant un rapport signal-sur-bruit satisfaisant. Avec le développement récent de modules d’échantillonnage adaptés aux microscopes en transmission à balayage (STEM), l’acquisition initialement réalisée ligne par ligne est devenue hautement paramétrable. Ainsi, il est désormais possible de visiter un ensemble de positions spatiales quelconques au cours de l’acquisition. De nombreux travaux ont proposé de s’appuyer sur ces avancées techniques pour permettre une acquisition optimisée pour des échantillons sensibles. Pour une dose d’électron globale équivalente à un échantillonnage standard, ces stratégies consistent à visiter moins de positions spatiales, et donc à procéder à un échantillonnage partiel. Par conséquent, une dose d’électron par position spatiale plus élevée est autorisée, ce qui permet d’augmenter le rapport signal-sur-bruit de chaque spectre mesuré. En contrepartie, une étape de post-traitement est nécessaire pour reconstruire l’ensemble de l’image, en particulier les spectres associés aux positions spatiales non visitées au cours de l’acquisition. Parmi les techniques de reconstruction utilisées dans la littérature, les méthodes d’interpolation sont rapides mais peu précises ; elles sont d’un intérêt tout particulier pour visualiser l’image complète au cours de l’acquisition. Au contraire, les techniques par apprentissage de dictionnaire sont très performantes, mais coûteuses tant en mémoire qu’en temps de calcul, et sont donc privilégiées pour raffiner l’image reconstruite après l’expérimentation. En définitive, peu de travaux ont cherché à combler ce fossé. L’objectif principal de cette thèse est de proposer des algorithmes de reconstruction rapides et performants en imagerie EELS. Ils devront, comme pour les méthodes d’interpolation, être suffisamment rapides pour visualiser l’image reconstruite au cours de l’acquisition. D’autre part, ces méthodes devront également afficher de meilleures performances que celles données par l’interpolation, voire proches de celles des techniques par apprentissage de dictionnaire. Pour cela, des méthodes par moindres carrés régularisés sont envisagées dans le cas d’échantillons spatialement lisses et d’échantillons cristallins périodiques. Les algorithmes proposés sont ensuite testés en s’appuyant sur des données synthétiques et réelles. L’intérêt de l’approche par acquisition partielle et les performances par rapport à d’autres méthodes de reconstruction sont étudiésIn electron energy loss spectroscopy (EELS), the sample to be analyzed is exposed to an electron beam, and the measure of the energy loss after passing through the material informs about the chemical composition. For samples particularly sensitive to electronic irradiation damages, such as organic materials, the experimenter is constrained to reduce the total electron dose received by the sample while obtaining a satisfying signal-to-noise ratio. With the recent development of sampling modules adapted to scanning transmission electron microscopes (STEM), the initial raster acquisition (i.e., line-by-line) has become highly configurable. Henceforth, it is now possible to visit any set of spatial positions during the acquisition. Based on these technical advances, a lot of works proposed optimized acquisition schemes for preserving sensitive samples. For a global electron dose equivalent to standard sampling, these strategies consist in visiting less spatial positions, i.e., to perform partial sampling. As a consequence, a higher electron dose per spatial position is allowed, which permits to increase the signal-to-noise ratio for each sampled spectrum. Yet, a post-processing step is required to infer the missing spectra. Among the reconstruction techniques used in the literature, the interpolation methods are fast but rather inaccurate ; they are particularly efficient for displaying the full image along the acquisition process. On the contrary, the dictionary learning-based methods are very performant, but are memory and computation demanding. They are chosen in priority to refine the reconstructed image after experimenting. Finally, only a few works attempt to fill this gap. The main objective of this Ph.D. thesis is to propose fast and accurate reconstruction algorithms for STEM-EELS imaging. Similarly to the interpolation methods, they should be fast enough to visualize the reconstructed image along the acquisition. Meanwhile, they should also achieve better reconstruction performances than those reached by interpolation, close to those of dictionary learning-based methods. To that end, regularized least square methods are proposed in the context of spatially smooth samples or of periodic crystalline samples. The proposed algorithms are then tested based on synthetic as well as real data experiments. The interest of partial-sampling based methods and the performances with respect to other reconstruction methods are evaluated
12
White, Edward Michael. "A study of the exploitation, migration and management of elvers and juvenile eels (Anguilla anguilla L.) in the rivers Severn and Avon, England". Thesis, University of Westminster, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296121.
Testo completo
13
Wood, Paula. "Mechanisms of visual pigment variation in teleosts". Thesis, University of Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.261282.
Testo completo
14
Eccles, James William Lesile. "An electron energy loss spectroscopy study of metallic nanoparticles of gold and silver". Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/an-electron-energy-loss-spectroscopy-study-of-metallic-nanoparticles-of-gold-and-silver(08669aaa-cdc8-4f5c-8428-4677dbc358cc).html.
Testo completoAbstract (sommario):
The application of gold and silver nanoparticles to areas such as medical research is based on unique optical properties exhibited by some metals. These properties are a direct consequence of localised excitations occurring at visible frequencies known as Surface Plasmon Resonances (SPRs). The exact frequency of an SPR induced in a nanoparticle can be 'tuned' in the optical range by, for example, changing the size of gold and silver nanoparticles, or by varying the relative concentrations of gold and silver within an alloy nanoparticle. Whatever the desired frequency, it is critical that the majority of nanoparticles exhibit the frequency within the resolution limit of the imaging system. The research presented here utilises the high resolution imaging and spectroscopy techniques of (Scanning) Transmission Electron Microscopy ((S)TEM) and Electron Energy Loss Spectroscopy (EELS). It is common practice to analyse the optical properties of alloy nanoparticles using techniques that acquire a single spectrum averaged over multiple particles such as Ultraviolet-Visible (UV-Vis) spectroscopy. However, this technique cannot detect any optical variation between the nanoparticles resulting from compositional change. In this research the author demonstrates through the use of EELS that the SPR can be determined for individual gold/silver alloy nanoparticles, for the purpose of determining the extent of their homogeneity. Importantly, the data presented here suggest dramatic variation in SPR frequency between particles and even within the same particle, indicative of large variations in alloy composition. This puts the assumption that alloying can be scaled down to the nanometre-scale to the test. In order to resolve and extract the SPR in both the pure gold and gold and silver alloy nanoparticles, the author has successfully applied multiple post acquisition techniques such as Richardson-Lucy deconvolution and Principle Component Analysis (PCA) to the EELS Spectrum Imaging (SI) acquisition method. Additionally, the valence band EELS data are supported by complementary electron microscopy techniques; Core loss EELS, Energy Dispersive X-Ray Spectroscopy (EDX) and High Angle Annular Dark Field (HAADF) imaging.
15
陳國權 e Kwok-kuen Chan. "Population genetics of the Japanese eel: anguilla japonica (temminck & schlegel)". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31234653.
Testo completo
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Lau, Yee-lan Estella. "Changes in intermediary metabolism of the eel, Anguilla japonica (Temminck & Schlegel) during artificial induction of sexual maturation /". [Hong Kong] : University of Hong Kong, 1987. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12345763.
Testo completo
17
Brown, K. J. "Origin, ecology and diversification of Lake Tanganyika mastacembelid eels (Teleostei: Synbranchiformes: Mastacembelidae)". Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1387534/.
Testo completoAbstract (sommario):
This thesis focuses on diversification in mastacembelid or spiny eels (Teleostei: Synbranchiformes: Mastacembelidae) from Lake Tanganyika (LT). LT is the oldest and deepest of the East African Rift Lakes, and is a world-renowned biodiversity hotspot. Chapter One introduces Mastacembelus and the concept of adaptive radiation theory. Chapter Two focuses on the origin and diversity of LT Mastacembelus, including 48% of the African non-LT species. A dated molecular phylogeny demonstrates the monophyly of the endemic Mastacembelus, which colonised LT 7-8 Ma and subsequently underwent rapid radiation forming five main lineages. Chapter Three is a comparative account of pectoral fin diversity within LT, and includes a description of a new species of endemic LT Mastacembelus lacking pectoral fins. Chapter Four incorporates two datasets to address whether LT Mastacembelus exhibit the signature of an adaptive radiation. Firstly, stable isotope analyses are used to estimate trophic niche utilisation and compare how trophic ecology is linked to phylogenetic history. Secondly, morphological diversity of LT Mastacembelus crania is assessed using 3D micro-computed tomography, and compared to the ecological data to test whether morphological traits are correlated to trophic niche exploitation and/or phylogenetic history. Chapter Five builds upon the molecular phylogeny of Chapter Two, by substantially increasing the taxonomic sampling of African species, which is now ~70% complete. This allows the endemic LT radiation to be viewed in the context of almost complete African Mastacembelidae diversity. Extended taxonomic sampling resolves a Congo species within the LT flock; this highlights the affinity of LT and the Congo Basin, and is potentially representative of an emigration and subsequent diversification of an endemic LT species in to the Congo River system. The Congo Basin taxa show high levels of diversity, and are not monophyletic. Chapter Six draws together conclusions about mastacembelid diversity and adaptive radiation, and raises areas for future research.
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Gentile, Laura. "Gonadal development of European eels, Anguilla anguilla, at different stages of silvering". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/24345/.
Testo completoAbstract (sommario):
The European eel (Anguilla anguilla, Linnaeus 1758) is a catadromous fish which has a great cultural, scientific, and commercial value. The protection of this species is particularly difficult because the biological eel’s life cycle remains in many aspects still unknown. The European eel (A. anguilla) population has declined alarmingly over the past 30 years, this condition has led to questions about the long-term welfare status of this species.
The objective of this thesis is to perform a histological analysis on gonad samples of European eels from 4 different lagoons of the North Adriatic at different stages of silvering and to evaluate the maturation of the gonads.
For this study were captured a total of 859 wild eels from 4 different lagoons using the “lavoriero”. Subsequently the biometric parameters were collected. A total of 79 female eels were randomly selected, dissected and the gonads were removed for histological analyzes. Sections of 4 μm were cut and labeled with hematoxylin and eosin (H&E). Histological observations of germ cells, at the level of light microscopy, allowed the characterization of six steps of oocyte maturation. Valle di Comacchio is the one with the highest levels of oocyte maturation while Valle Ca Pasta has the lowest. What needs to be stressed is that eels with silver index III have an oocyte maturation nearly equal to eels at stage IV and V of silvering.
Considering the results, we can affirm that eels from North Adriatic lagoons are eels with high levels of oocyte maturation accompanied by high indices of GSI values at silver stages III. The following experimental work showed that the levels of oocyte maturation are higher even at lower silver index levels. It can be hypothesized that in the case of North Adriatic eels the transition from yellow to silver eel occurs faster in relation to the high trophic availability in North Adriatic lagoons.
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Hssein, Khalid. "Analyse des modulations exelfs observees en spectroscopie de pertes d'energie d'electrons (eels)". Toulouse 3, 1988. http://www.theses.fr/1988TOU30121.
Testo completoAbstract (sommario):
Definition des conditions experimentales pour la mise en evidence de ces structures modulees au-dela des seuils d'excitation dans les spectres de perte d'energie des electrons. Etude de l'influence de l'energie du faisceau primaire sur la visibilite du signal en liaison avec l'epaisseur locale et la nature de l'echantillon dans des microscopes electroniques fonctionnant entre 100 et 1000 kv. Developpement d'un programme numerique de traitement des spectres et de determination de la fonction de distribution radiale des atomes. Exploitation de la technique pour des niveaux k d'atomes a z<->14; test pour bn,sic,al::(2)o::(3): les distances interatomiques peuvent etre determinees a +ou- 0,02a pres; extension a plusieurs types de materiaux binaires amorphises de structure mal connue: evaluation des deplacements atomiques induits par amorphisation
20
Laffont, Lydia. "Structure et propriétés physiques de matériaux polyaromatiques par MET, EELS, et RX". Toulouse 3, 2002. http://www.theses.fr/2002TOU30129.
Testo completo
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Tse, Ka Fai William. "Functional studies of gill epithelial cells isolated from Japanese eels (anguilla japonica)". HKBU Institutional Repository, 2008. http://repository.hkbu.edu.hk/etd_ra/879.
Testo completo
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Hssein, Khalid. "Analyse des modulations EXELFS observées en spectroscopie de pertes d'énergie d'électrons (EELS)". Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376143998.
Testo completo
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Barnard, John Cameron. "Low energy electron scattering by ordered adsorbed molecules". Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321430.
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Strickland, Patrick Andrew. "American Eel Distibution and Growth in Selected Tributaries of the James River". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35793.
Testo completoAbstract (sommario):
In July of 1999, a team of researchers from the Virginia Department of Game and Inland Fisheries (VDGIF) and the United States Forest Service (USFS) electrofished a 2-km reach of Shoe Creek, Virginia, and captured 66 American eels. Eels were weighed (g) and measured (mm) and 61 individuals were implanted with Passive Integrated Transponders (PIT). Size distribution of the tagged eels ranged from 174-775 mm total length. The team returned to Shoe Creek in October of 1999 for a recapture survey, but captured only seven eels in the same 2-km reach with no recaptures. This sparked considerable interest among the biologists of VDGIF and USFS. Goals of the biologists included identifying daily movement, seasonal distribution, relative abundance, habitat use, and growth of American eels in Virginia headwater streams. This information was needed for the protection of eel habitat and migration corridors, as well as development of restoration plans for eels.
Seasonal movement of thirty-three American eels Anguilla rostrata was monitored from July 2000 through September 2001 via radio telemetry. South Fork Piney River, South Fork Tye River, and Shoe Creek, Virginia were the streams chosen for eel research. Eels exhibited the greatest amount of movement in summer 2000 and the least amount of movement in winter 2000-01. Diel activity was significantly lowest in winter 2000-01 and highest in spring 2001. From late October 2000 through May 2001, eels appeared to be buried within the interstitial spaces of the stream bottom and under stream banks.
Habitat preference (average depth, dominant substrate, and pool vs. riffle) was also determined over multiple seasons via radio telemetry. When a preference was detected, eels always preferred pools and the deepest water available relative to each stream. Eels preferred cobble as the dominant substrate during all seasons in S.F. Tye River. Eels showed no preference for substrate in S.F. Piney River. Substrate preference varied among seasons in Shoe Creek.
Estimates of 12, 41, and 25 eels/ha were calculated for S.F. Piney River, S.F. Tye River, and Shoe Creek, respectively, in summer 2000. There was a significantly higher density of eels in S.F. Tye River when compared to S.F. Piney River in summer 2000. Estimates of 7, 54, and 15 eels/ha were calculated for S.F. Piney River, S.F. Tye River, and Shoe Creek, respectively, in summer 2001. There was a significantly higher density of eels in S.F. Tye River when compared to both S.F. Piney River and Shoe Creek in summer 2001.
Growth in total length (TL) was determined in S.F. Piney River, S.F. Tye River, and Shoe Creek from summer 2000 to summer 2001. Growth in TL for S.F. Piney River, S.F. Tye River, and Shoe Creek was 18, 23, and 21 mm/year, respectively. Growth in TL for Shoe Creek was also calculated from 1999-2000 (43 mm/year) and 1999-2001 (32 mm/year). There was a significant difference in growth between Shoe Creek 1999-2000 and Shoe Creek 2000-01 as well as Shoe Creek 1999-2000 and S.F. Tye River 2000-01.
Growth in weight was also determined in S.F. Piney River, S.F. Tye River, and Shoe Creek from summer 2000 to summer 2001. Growth in weight for S.F. Piney River, S.F. Tye River, and Shoe Creek was 24, 21, and 27 g/year, respectively. Growth in weight for Shoe Creek was also calculated from 1999-2000 (50 g/year) and 1999-2001 (40 g/year). There was a significant difference in growth between Shoe Creek 1999-2000 and Shoe Creek 2000-01 as well as Shoe Creek 1999-2000 and S.F. Tye River 2000-01.
Our results have contributed to knowledge of the biology and ecology of the American eel in the upper James River drainage, including diel activity, seasonal movements, habitat use, densities, and growth. Eels were more active during spring and summer, particularly at night. They demonstrated very little movement throughout the other seasons of the year. The majority of eels displayed a behavior similar to hibernation, burying in the substrate and under the banks of the stream from mid-fall through mid-spring. Eels showed a trend to use deep pools with large substrate throughout the majority of this study. Eel densities seemed to vary among streams, with higher growth in streams with lower eel densities and a higher average water temperature.Master of Science
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Yedra, Cardona Lluís. "Towards a new dimension in analytical TEM: EELS, Tomography and the Spectrum Volume". Doctoral thesis, Universitat de Barcelona, 2013. http://hdl.handle.net/10803/145317.
Testo completoAbstract (sommario):
The main goal of this thesis is to combine electron tomography and electron energy loss spectroscopy (EELS) in the TEM, in order to obtain chemical and electronic information in 3D in the nanoscale.
Tomography in the TEM has been discussed and the advantages and disadvantages of HAADF STEM tomography have been analyzed.
- A Fe3O4 nanocube sample has been considered to illustrate the acquisition, alignment, tilt axis assessment, reconstruction and visualization processes.
- HAADF STEM tomography has been used to reconstruct the shape of a series of Cu2O nanoparticles. For one of the samples, the facets of the Cu2O nanoparticles, octahedral in shape, have been found to correspond to {111} planes.
The physics and the data analysis methods of core-loss EELS have been briefly summarized. Two relevant contributions have been made:
- The effects of beam precession on EELS have been investigated. A signal enhancement due to electron beam precession in the TEM when in zone axis conditions has been discovered for the first time.
- A homemade software, Oxide Wizard, for valence state determination of transition metals has been developed and applied to map the Mn oxidation state of a MnOx/FeOy nanoparticle.
EELS spectrum imaging and electron tomography have been combined to recover chemical information in 3D for FexCo(3-x)O4@Co3O4 mesoporous nanoparticles.
- The samples have been first characterized by HAADF STEM tomography and EELS.
- EELS chemical information is, of course, limited to 2D maps, while only structural information is be recovered in 3D form HAADF tomography.
. An EELS-SI tilt series has been acquired at 80 kV and low acquisition times, resulting in a very noisy dataset.
- Principal component analysis (PCA) has been used to separate the noise from the signal.
- Quantifications of the O, Fe and Co signals have been reconstructed, and the shape of the particle recovered.
- From the noise clean dataset, components with physical meaning (iron oxide, cobalt oxide and thickness) have been extracted using independent component analysis (ICA), and reconstructed in 3D.
- A new kind of signal with chemical and thickness information has been obtained by combining the thickness component with the quantification results. This signal is able to properly reconstruct the chemical structure of the sample in 3D, detecting a higher presence of iron in the surface, and an even distribution of Fe inside of the particle.
. Another EELS-SI tilt series has been acquired at 80 kV and low acquisition times with enough spatial resolution to resolve the porous structure.
- The noise has been reduced using PCA.
- Four signals extracted from the spectrum have been reconstructed: the integrated edge intensities for oxygen, iron and cobalt, and the integrated background prior to the oxygen edge.
EELS-SI tomography has been applied to reconstruct CoFe2O4 (CFO) nanocolumns embedded in a BiFeO3 (BFO) matrix grown on LaNiO3 buffered LaAlO3 substrate (BFO-CFO//LNO/LAO).
- The nanocomposite sample has been prepared in a nanoneedle shape by means of focused ion beam (FIB). This preparation has the advantage of keeping the thickness of the sample constant throughout the tilting experiment. The nanoneedle contains an island of CFO in a matrix of BFO, as well as the LNO/LAO substrate.
- The noise has been discarded using PCA.
- The oxygen, iron and lanthanum edges intensities have been extracted and reconstructed.
A new kind of data hypercube, the Spectrum Volume, has been proposed. Just as a Spectrum Image contains a spectrum per pixel, a Spectrum Volume is to contain a spectrum per voxel.
EELS-SI tomography has been applied to successfully acquire a spectrum volume (SV) of the (BFO-CFO//LNO/LAO) system.
- PCA has been used to discard the noise and Bayesian linear unmixing (BLU) has been used to extract independent components (eigenspectra).
- Each eigenspectrum has a 2D weighting map for each tilt; weighting maps have been reconstructed into 3D weighting volumes.
- Full single spectra for any point in the reconstructed space can now be recovered as a weighed sum of eigenspectra, using the 3D weighting distributions. This approach is used to extract single spectra, spectrum lines and spectrum images from the inside of the sample.
In the context of this thesis, tomography and EELS-SI have been combined to successfully recover chemical information in 3D at the nanoscale, and a new kind of data hypercube, the Spectrum Volume, has been proposed and experimentally recovered.En el microscopi electrònic de transmissió (TEM), es poden obtenir imatges d’una mostra des de diferents angles i posteriorment reconstruir aquestes imatges en tres dimensions (3D). Per altra banda, les interaccions dels electrons del feix amb els electrons de la mostra poden ser analitzades mitjançant l’espectroscòpia de pèrdues d’energia dels electrons (EELS), obtenint així informació química de la mostra. L’objectiu d’aquesta tesi és la combinació de l’espectroscòpia EELS amb la tomografia electrònica per obtenir informació química en 3 dimensions a la nanoescala. S’han explicat les bases de la tomografia electrònica i el procediment de la reconstrucció ha estat il•lustrat amb una mostra de nanocubs d’òxid de ferro. Posteriorment, s’ha aplicat a una sèrie de nanopartícules de Cu2O per tal de descriure’n la forma. També s’ha explicat la física en què es basa l’EELS, fent especial atenció als llindars d’altes pèrdues d’energia. A continuació, s’ha mostrat l’augment del senyal obtingut amb precessió electrònica al TEM quan la mostra es troba en condicions d’eix de zona. Seguint amb les aplicacions d’EELS, s’ha explotat la possibilitat de caracteritzar els estats d’oxidació dels metalls de transició mitjançant un programa propi, escrit per a Digital Micrograph i anomenat Oxide Wizard. Una vegada la tomografia electrònica i l’espectroscòpia de pèrdues d’energia dels electrons han estat explicades, s’ha procedit a reconstruir informació extreta d’EELS en 3D. S’han realitzat una sèrie d’experiments amb partícules mesoporoses que han demostrat la utilitat d’aplicar l’anàlisi multivariable per tal de reduir el soroll de les dades i extreure’n els components. Finalment, s’ha dissenyat un experiment en el qual ha estat possible recuperar l’espectre corresponent a cada unitat d’espai com la combinació d’espectres propis en una mostra preparada en forma de nanoagulla. Els espectres recuperats corresponen a la contribució de cada unitat de volum als espectres projectats. Aquest nou tipus de dades permet extreure espectres de l’interior d’una mostra. Finalment, doncs, s’ha pogut combinar amb èxit la tomografia electrònica i EELS per obtenir informació química en tres dimensions a la nanoescala.
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Mohn, Michael Johannes [Verfasser]. "Energy-filtered TEM and low-loss EELS of 2D materials / Michael Johannes Mohn". Ulm : Universität Ulm, 2020. http://d-nb.info/122210931X/34.
Testo completo
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Alix, Kévin. "Développement d'une approche basée sur la microscopie électronique en transmission filtrée en énergie pour la détermination des propriétés physiques de bulles d'hélium dans le silicium". Thesis, Poitiers, 2016. http://www.theses.fr/2016POIT2266/document.
Testo completoAbstract (sommario):
Ce mémoire est consacré au développement et à l'application d'une méthode permettant de caractériser finement les propriétés physiques (densité d'hélium, pression, diamètre, morphologie) de bulles d'hélium de taille nanométrique pour in fine améliorer la compréhension du comportement de ces nano-systèmes. L'approche que nous avons choisie est basée sur la spectroscopie de pertes d'énergie des électrons et l'acquisition de spectres images en microscopie électronique en transmission filtrée en énergie. Les différentes étapes d'acquisition, de correction des aberrations, et de traitement des spectres sont détaillées. L'erreur sur la mesure est estimée, et des améliorations potentielles de la méthode sont discutées. Nous montrons de plus que cette approche permet non seulement de dépasser les limites imposées par la microscopie électronique en transmission à balayage habituellement utilisée, mais aussi d'aller au-delà, en terme de statistique notamment. Nous appliquons ensuite notre méthode pour déterminer les propriétés physiques de bulles d'hélium dans le silicium, lors de recuits thermiques in situ dans le microscope. L'évolution des caractéristiques morphologiques des bulles est mise en rapport avec la variation de la densité d'hélium qu'elles contiennent suite à ces recuits. Les valeurs de densité et de pression obtenues sont comparées aux valeurs disponibles dans la littérature par des méthodes expérimentales ou numériques. Enfin, le transfert de notre méthode pour l'étude de bulles dans d'autres matrices (germanium, carbure de silicium, euxénite) est discutéThis thesis is dedicated to the development and application of a method allowing for the fine characterization of the physical properties (density, diameter, pressure and morphology) of helium bubbles at the nanometric scale, to eventually improve the understanding of the behavior of these nano-systems. The chosen approach is based on electron energy loss spectroscopy and the acquisition of spectral images by energy-filtered transmission electron microscopy. The acquisition, aberration correction, and data analysis steps are detailed. The measurement error is estimated, and potential improvements are discussed. We additionally show that this method is not only able to overcome the limits imposed by commonly used scanning transmission electron microscopy, but also to go further, notably in a statistical way. We then apply our method to determine the physical properties of helium bubbles in silicon, during in situ thermal annealing in the microscope. The evolution of the morphological characteristics of the bubbles is put in relation with the variation of the density of the helium contained following these annealings. The density and pressure values are compared to those available in the litterature through experimental and numerical methods. Finally, the translation of this method towards the study of bubbles in other matrices (germanium, silicon carbide, euxenite) is discussed
28
Troc, Nicolas. "Étude des propriétés optiques de nanoparticules d’argent sondées par spectroscopies optique et électronique". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1194/document.
Testo completoAbstract (sommario):
Cette thèse a pour but d'étudier les effets quantiques apparaissant pour des agrégats métalliques de très petite taille en raison de l'augmentation du ratio surface/volume et de la discrétisation de la structure électronique. Mettre en avant ces effets demande une très grande qualité de fabrication des nanoparticules étudiées, monodisperse dans le cas idéal. Nous fabriquons des nanostructures en encapsulant des agrégats d'argent générés par une source magnétron dans des matrices solides, comme la silice ou l'alumine. Cette technique nous permet de contrôler indépendamment la composition des particules, leur taille, et leur concentration. Un spectre de masse quadripolaire a été mis en place et utilisé comme un filtre en taille pour obtenir une distribution plus étroite et précise.Les échantillons ont été caractérisés par deux techniques complémentaires : par spectroscopie optique à transmission avec des mesures sur des ensembles de particules, et par spectroscopie de perte d'énergie des électrons (EELS) sur des particules uniques, réalisée dans un microscope électronique à balayage par transmission. Bien qu'utilisant deux outils conceptuellement différents, ces deux méthodes mesurent les résonances plasmoniques des particules. Ce travail a donc pour objectif de relier théoriquement et expérimentalement ces deux méthodes dans le but de comprendre comment les propriétés physiques de ces petits agrégats de métaux nobles sont affectées par les effets quantiquesThe aim of this thesis is to study quantum effects appearing in very small metallic clusters caused by the increasing surface/volume ratio and the discretization of the electronic structure. Investigating effects such as size dependencies demand a very high quality of the studied nanoparticles, monodisperse in the ideal case. We fabricate nanostructures by embedding silver clusters generated in a magnetron source in solid matrices, such as silica or alumina. This technique gives us full and independent control over the particle composition, size and concentration. A quadrupole mass spectrometer is used as a size filter to obtain a more precise and narrow distribution.Samples have been characterized with two complementary methods: optical transmission spectroscopy of ensembles of particles and electron energy loss spectroscopy (EELS) on single particles using a scanning transmission electron microscope. Although these two tools are conceptually different, they both measure the plasmonic resonances of metal nanoparticles. The objective of this work is to link theory and experiment in these two methods in order to understand how the physical properties of these small noble metal clusters are affected by quantum effects
29
Barak, Najim A.-E. "Aspects of biology and heavy metal contamination of eels and roach in East Anglia rivers". Thesis, University of Essex, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328860.
Testo completo
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Carseldine, Lee. "Towards effective practical diets for the intensive aquaculture of juvenile longfinned eel, Anguilla reinhardtii (Steindachner 1867) /". [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18379.pdf.
Testo completo
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Tran, Van Chuoi Myriam. "Molecular cloning of an angiotensin II receptor isoform in the European eel, Anguilla anguilla". Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368077.
Testo completo
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劉綺蘭 e Yee-lan Estella Lau. "Changes in intermediary metabolism of the eel, Anguilla japonica (Temminck & Schlegel) during artificial induction of sexualmaturation". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31231238.
Testo completo
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Muto, Shunsuke, e Yusuke Sasano. "Energy-drift correction of electron energy-loss spectra from prolonged data accumulation of low SNR signals". Oxford University Press, 2008. http://hdl.handle.net/2237/20779.
Testo completo
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Orimo, Shin-ichi, Kazutaka Ikeda, Shunsuke Muto e Kazuyoshi Tatsumi. "Chemical Bonding of AlH3 Hydride by Al-L2,3 Electron Energy-Loss Spectra and First-Principles Calculations". MDPI, 2012. http://hdl.handle.net/2237/20829.
Testo completo
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Gu, Jie. "Characterization of in-situ Ca²⁺ -sensing mechanisms and stanniocalcin-1 target cells in gills of Japanese eels". HKBU Institutional Repository, 2014. https://repository.hkbu.edu.hk/etd_oa/74.
Testo completoAbstract (sommario):
Calcium ion has diverse beneficial roles in living organisms. Failure in Ca2+ homeostasis affects a variety of molecular and cellular processes, ultimately leading to many pathological consequences. In mammals, body Ca2+ homeostasis is maintained by the coordinated calcium (re)absorption that occurs in the small intestines, kidneys and bones, and is under tight hormonal control. In fish, two special organs, Corpuscles of Stannius (CS) glands and gills form a regulatory circuit to detect and regulate blood Ca2+ homeostasis. However, the underlying molecular mechanism in the regulation of gill Ca2+ uptake has not been fully examined. Moreover, some putative biological active substances in CS glands have not been identified. To address these research questions, a euryhaline fish, Japanese eel (Anguilla japonica) was used as an animal model for the study. Fish gill is equipped with epithelial calcium channel (ECaCl) as gatekeeper of Ca2+ entry, and membrane Ca2+-ATPase (PMCA) for Ca2+ efflux. To test if branchial ECaCl and PMCA responded to change in water Ca2+ level, we investigated the changes in fish adapted in artificial freshwater (AFW), Ca2+-deficient AFW (D-AFW) or high Ca2+-AFW (H-AFW). Our data illustrated both short-term and long-term effects on modulations of the transporters. The changes correlated with expression levels of stanniocalcin-1 (STC-1) in CS glands. This part of study supports the regulatory circuit between gills and the glands. In primary cell culture of Japanese eel gill cells, Ca2+ sensing was shown to be mediated by Ca2+ sensing receptor (CaSR) coupled to phospholipase C (PLC)-extracellular signal-regulated kinase (ERK) and PLC-inositol triphosphate (IP3)-Ca2+/calmodulin-dependent protein kinase-II (CaMK-II) pathways. And CaSR-STC-1/cyclo-oxygenase-2 (COX-2) mediated protective pathway in gill cells that exerts a possible protective mechanism against an increase in intracellular Ca2+ levels associated with transepithelial Ca2+ transport. Apparently, the protective effects against Ca2+-mediated cytotoxicity of gill cell were mediated by STC-1 binding on gill cells that led to elevations of cytosolic cAMP. In a follow-up experiment of using Ca2+-imaging system in a model of thapsigargin (TG)-induced elevation of cytosolic Ca2+, a hypocalcemic action of STC-1 was demonstrated and was found to be mediated by cAMP and COX-2 pathway. To further determine the gene expressed in CS gland responsive to changes in water salinity, the first transcriptome database of CS glands from fish adapted in freshwater or seawater condition. A de novo assembly of RNA sequencing data generated 11747 unigenes and revealed 475 genes that were differentially expressed. Three functional clusters: (1) Ca2+-metabolism, (2) blood pressure and (3) ion-osmoregulation were revealed. Gene targets, in addition to STC-1 in related to the regulation of calcium metabolism and blood pressure, like calcitonin, atrial natriuretic peptide-converting enzyme and endothelin-converting enzyme 1 were identified. Taken together this thesis described a comprehensive study on the functional circuit between gills and CS glands to decipher the regulation and functions of transporters and hormones in calcium metabolism in fish.
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Franchini, Daniele. "Artificial reproduction survey in male European eels Anguilla anguilla (Linnaeus 1758) by paternity assignment". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Cerca il testo completoAbstract (sommario):
The European eel Anguilla anguilla (Linnaeus, 1758) is a critically endangered species whose survival in the wild is largely threatened by human activity. In addition, this vertebrate's unique ecology and biology make it even more vulnerable, and the IUCN listed A. anguilla as severely endangered on the Red List of Threatened Species. In this scenario, captive breeding can represent a significative help for the species' future and many efforts have been dedicated to the artificial reproduction. Ten years ago, dedicated research programs on A. anguilla artificial reproduction started at the DIMEVET (Bologna University). In 2020, based on parentage assignment, some lights were thrown on the reproductive performance in semi-natural conditions. The present study aims to verify if the artificial mixing of male and female gametes would lead to different results in males’ fertilization rates, improving the final rate of genetic variability. We analysed six successful reproduction events. 22 adults and 258 larvae were genotyped by 10 specie-specific microsatellite loci and paternity was allocated to 250 larvae, with a rate of success in parentage assignment of 94%. Even if a locus had to be discarded from the data set for technical reasons, this high rate in allocation success accounts for the good resolution power of the remaining nine loci (mean PIC 0.812).
In each reproduction we observed a single male who contributed with 40-70% of the offspring generated, two subordinate males who contributed with 10-30% of the F1 and an “ineffective” one which contributed with 8% or less to F1. This result is homologous to the previous results in semi-natural conditions. The presence of a similar pattern of fertilization rate by different males in both studies, suggest that the behavioural component is unlikely to be the cause of the offspring generation disparity, and other explanations should be considered, like sperm quality and factors that would impact on it.
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Hambach, Ralf. "Theory and ab-initio calculations of collective excitations in nanostructures : towards spatially-resolved EELS". Palaiseau, Ecole polytechnique, 2010. http://pastel.archives-ouvertes.fr/docs/00/58/70/80/PDF/PhD_Hambach_2010.pdf.
Testo completoAbstract (sommario):
Cette thèse présente les résultats d'études théoriques et numériques des excitations collectives de systèmes de carbone de dimensionnalité différente. D'abord, une méthode combinant la théorie du milieu effectif et des calculs ab-initio a été développée pour décrire les excitations collectives de nanostructures (comme les nanotubes de carbone) à partir de la polarisabilité de leurs blocs élémentaires (graphène). Contrairement à la théorie diélectrique standard, les équations de Maxwell sont résolues pour la fonction diélectrique microscopique dépendant du temps et du moment ε(q,q',ω) du matériau massif. Cette dernière a été calculée à partir des premiers principes dans l'approximation de la phase aléatoire (RPA). Cette méthode a ensuite été appliquée pour calculer les spectres de perte d'énergie d'électrons (EELS) pour le graphène et les nanotubes de carbone monoparoi (SWCNT). L'accord avec les calculs complètement ab-initio sur ces systèmes et avec les expériences correspondantes est très bon. La dispersion du plasmon π dans le graphène et les SWCNT a été analysée et expliquée. La dépendance avec la direction du moment des spectres de perte d'énergie d'électrons des SWCNT est comprise en termes d'excitations des modes normaux. Finalement, l'utilisation des calculs ab-initio en vue de prédire le EELS résolu spatialement a été étudiée. Le facteur de forme mixte dynamique a été analysé et une discontinuité de son comportement pour certaines réflections de Bragg a été prédite. Cet effet a été expliqué par les effets de champ cristallin et a été confirmé par des expériences de IXS sur le graphite et le silicium. L'approche blocs élémentaires a été appliquée au EELS résolu spatialementIn this thesis, collective excitations of carbon systems with different dimensionality have been studied both theoretically and numerically. First, a method combining effective medium theory and ab-initio calculations has been developed which allows to describe the collective excitations of nanostructures (like carbon nanotubes) starting from the polarisability of their building blocks (graphene). In contrast to standard dielectric theory, the Maxwell equations are solved for the full frequency- and momentum-dependent microscopic dielectric function ε(q,q',ω) of the bulk material. The latter is calculated from first-principles within the Random Phase Approximation. Second, this method has been applied to calculate electron-energy loss spectra (EELS) for graphene and single-wall carbon nanotubes (SWCNT). The results are in good agreement with full ab-initio calculations of these systems and corresponding experiments. The linear dispersion of the π plasmon in graphene and SWCNTs has been analysed and explained. The directional dependence of the electron energy-loss spectra of SWCNTs is understood in terms of its normal mode excitations. Third, the use of ab-initio calculations for the prediction of spatially-resolved EELS is discussed. Therefore, the mixed dynamic form factor has been studied and a discontinuous behavior at certain Bragg reflections is predicted. This effect has been explained in terms of crystal local field effects and verified by IXS experiments on graphite and silicon. Finally, the building block approach is applied for spatially-resolved EELS
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Boniface, Maxime. "Suivi à l'échelle nanométrique de l'évolution d'une électrode de silicium dans un accumulateur Li-ion par STEM-EELS". Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAY051/document.
Testo completoAbstract (sommario):
L’accroissement des performances des accumulateurs Li-ion sur les 25 dernières années découle principalement de l’optimisation de leurs composants inactifs. Aujourd’hui, l’urgence environnementale impose de développer de nouveaux matériaux actifs d’électrode pour proposer la prochaine génération d’accumulateur qui participera à la transition énergétique. A cet effet, le silicium pourrait avantageusement remplacer le graphite des électrodes négatives à moyen terme. Cependant la rétention de capacité des électrodes de silicium est mise à mal par l’expansion volumique que le matériau subit lors sa réaction d’alliage avec le lithium, qui mène à la déconnexion des particules de Si et à une réduction continue de l’électrolyte. Une compréhension de ces phénomènes de vieillissement à l’échelle de la nanoparticule est nécessaire à la conception d’électrodes de silicium viables. Pour ce faire, la technique STEM-EELS a été optimisée de manière à s’affranchir des problèmes d’irradiation qui empêchent l’analyse des matériaux légers d’électrode négative et de la Solid electrolyte interface (SEI), grâce à l’analyse des pertes faibles EELS. Un puissant outil de cartographie de phase est obtenu et utilisé pour mettre en lumière la lithiation cœur-coquille initiale des nanoparticules de silicium cristallin, la morphologie hétérogène et la composition de la SEI, ainsi que la dégradation du silicium à l’issue de cyclages prolongés. Enfin, un modèle de vieillissement original est proposé, en s’appuyant notamment sur un effort de quantification des mesures STEM-EELS sur un grand nombre de nanoparticulesOver the last 25 years, the performance increase of lithium-ion batteries has been largely driven by the optimization of inactive components. With today’s environmental concerns, the pressure for more cost-effective and energy-dense batteries is enormous and new active materials should be developed to meet those challenges. Silicon’s great theoretical capacity makes it a promising candidate to replace graphite in negative electrodes in the mid-term. So far, Si-based electrodes have however suffered from the colossal volume changes silicon undergoes through its alloying reaction with Li. Si particles will be disconnected from the electrode’s percolating network and the solid electrolyte interface (SEI) continuously grows, causing poor capacity retention. A thorough understanding of both these phenomena, down to the scale of a single silicon nanoparticle (SiNP), is critical to the rational engineering of efficient Si-based electrodes. To this effect, we have developed STEM-EELS into a powerful and versatile toolbox for the study of sensitive materials and heterogeneous systems. Using the low-loss part of the EEL spectrum allows us to overcome the classical limitations of the technique.This is put to use to elucidate the first lithiation mechanism of crystalline SiNPs, revealing Li1.5Si @ Si core-shells which greatly differs from that of microparticles, and propose a comprehensive model to explain this size effect. The implications of that model regarding the stress that develops in the crystalline core of SiNPs are then challenged via stress measurements at the particle scale (nanobeam precession electron diffraction) for the first time, and reveal enormous compressions in excess of 4±2 GPa. Regarding the SEI, the phase-mapping capabilities of STEM-EELS are leveraged to outline the morphology of inorganic and organic components. We show that the latter contracts during electrode discharge in what is referred to as SEI breathing. As electrodes age, disconnection causes a diminishing number of SiNPs to bear the full capacity of the electrode. Overlithiated particles will in turn suffer from larger volumes changes and cause further disconnection in a self-reinforcing detrimental effect. Under extreme conditions, we show that SiNPs even spontaneously turn into a network of thin silicon filaments. Thus an increased active surface will compound the reduction of the electrolyte and the accumulation of the SEI. This can be quantified by summing and averaging STEM-EELS data on 1104 particles. In half-cells, the SEI volume is shown to increase 4-fold after 100 cycles without significant changes in its composition, whereas in full cells the limited lithiation performance understandably leads to a mere 2-fold growth. In addition, as the operating potential of the silicon electrodes increases in full cells – potential slippage – organic products in the SEI switch from being carbonate-rich to oligomer-rich. Finally, we regroup these findings into an extensive aging model of our own, based on both local STEM-EELS analyses and the macro-scale gradients we derived from them as a whole
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Bach, David [Verfasser], e D. [Akademischer Betreuer] Gerthsen. "EELS investigations of stoichiometric niobium oxides and niobium-based capacitors / David Bach. Betreuer: D. Gerthsen". Karlsruhe : KIT-Bibliothek, 2009. http://d-nb.info/1014222036/34.
Testo completo
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Knights, Brian. "Studies of European eels (Anguilla anguilla L.) in relation to warmwater aquaculture and stock management". Thesis, University of Westminster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362661.
Testo completo
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Mount, Sarah J. "Searching for silver| An examination of the physical and environmental characteristics of maturing American eels". Thesis, State University of New York Col. of Environmental Science & Forestry, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10117994.
Testo completoAbstract (sommario):
As eel populations decline worldwide, research tools for scientists and managers to better understand eel populations and dynamics will be vitally important. This research focuses on the relatively understudied silver phase eel, the sexually mature adult life stage that will make the single spawning journey to the oceanic spawning grounds. A non-lethal index of eel maturity was designed based on external measurements and was able to correctly classify individuals into one of seven maturity classes 83% of the time overall, yielding similar results to other non-lethal indices. Habitats above and below barriers to migration, at varying levels of watershed urbanization, and different distances from the ocean were compared in terms of eel maturity, size, age, and parasite parameters. Two methods of bioelectrical impedance analysis (BIA) were evaluated in their ability to estimate eel lipid concentration, a key factor in eel maturity and successful spawning.
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Ho, Cheuk Hin. "Effects of osmotic stress on molecular responses of gill cells from Japanese eels, Anguilla Japonica". HKBU Institutional Repository, 2021. https://repository.hkbu.edu.hk/etd_oa/885.
Testo completoAbstract (sommario):
Japanese eels (Anguilla japonicas) are snakelike fishes living in waters in the Asian region. In contrast to most fishes which are stenohalines that can only live in waters with a narrow range of salinity, Japanese eels are classified as euryhalines that can habitat in a broad range of salinity. As the lifecycle of Japanese eels consists of stages across fresh and seawater districts, a well-developed osmoregulation mechanism is needed to balance the intra- and extra- cellular osmolarity of the fishes throughout the seawater acclimation process. While fish gills are one of the organs that separating the ambient water and the inner body fluid of the fish, the fish gills of the Japanese eels have been studied as one of the most crucial organs for osmoregulation purposes. Yet, the osmoregulation and survival strategies of Japanese eels under hyperosmotic stress has not been fully elucidated. In chapter 2, this study has performed a transcriptome study on the ex vivo gill filament model of the Japanese eel to profile the molecular responses after a hypertonic treatment of 4 hours or 8 hours. The experiment is aimed to mimic the gill cells exposed to seawater in the seawater acclimation process of Japanese eels. A profile of differential expressed genes (DEGs) has been revealed that 577 DEGs were commonly upregulated and 711 DEGs were commonly downregulated in both 4- and 8-hours hypertonic treatment. Functional analysis and annotation have been processed with these DEGs, including Ingenuity Canonical Pathways analysis and gene ontology. These analyses have revealed that the cellular homeostasis of the gill cells has been disrupted and cell death responses has been induced by osmotic stress. The results have raises a concern that the maintenance of cellular viability and a cell death regulation mechanism are needed for the fishes to survive in the early stage of seawater acclimation. In chapter 3, this chapter demonstrated that gill cells in Japanese eels are susceptible to apoptosis when they are exposed to hyperosmotic treatments in both in vitro gill cell and the ex vivo gill filament model. To maintain the viability of the gills cells, two inhibitors of apoptosis, XIAP, and survivin, were seen to be expressed in gills cells. The expression of XIAP and survivin were upregulated by dexamethasone, which is an agonist mimicking the effect of cortisol on fishes in seawater acclimation. Meanwhile, the expression levels of the apoptosis executor, caspase 3, were downregulated. These data suggested that with the regulation of cortisol express in the fishes, XIAP and survivin are effective apoptosis regulators in the gill cells of Japanese eels. The study has demonstrated the molecular responses of the gills of Japanese eels exposed to hyperosmotic stress at the transcriptional level and post-translational level by using transcriptome studies and protein study respectively. The study has paved cell death regulation to be another the key field to study in understanding the ability of salinity tolerance in euryhalines.
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Hammond, Stephen D. "Seasonal movements of yellow-phase American eels (Anguilla rostrata) in the Shenandoah River, West Virginia". Morgantown, W. Va. : [West Virginia University Libraries], 2003. http://etd.wvu.edu/templates/showETD.cfm?recnum=3286.
Testo completoAbstract (sommario):
Thesis (M.S.)--West Virginia University, 2003.Title from document title page. Document formatted into pages; contains vii, 32 p. : ill., map (part col.) Includes abstract. Includes bibliographical references.
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Warshafsky, Zoemma Taudel. "Impact of the Parasitic Nematode Anguillicoloides Crassus on American Eels (Anguilla Rostrata) in Chesapeake Bay". W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639681.
Testo completoAbstract (sommario):
American eels are infected by the introduced parasitic nematode, Anguillicoloides crassus, which can cause significant damage to their swimbladders. Despite the high prevalence and severe damage caused by A. crassus, the population level effects on American eels are not well understood. The prevalence and swimbladder damage in young glass eels and elvers are relatively unstudied, despite the potential for this parasite to cause tissue damage. Additionally, the effects of environmental, temporal, and spatial variables have been debated in previous studies without consensus. Also, the potential for eels to recover from infection and tissue damage has been speculated but not definitively shown. Therefore this Master’s thesis sought to answer these questions through field and laboratory studies. Glass and elvers stage American eels were collected during the spring and summer of 2015 and dissected to enumerate infection intensity and estimate swimbladder condition using the swimbladder degenerative index (SDI). Data were then combined with a larger dataset for yellow eels and analyzed using zero-inflated and ordinal logistic regressions to determine the effects of season, site, and eel length on infection intensity and swimbladder condition. The relationship between infection intensity and swimbladder condition was evaluated. This dataset was then used to investigate if the force-of-infection (i.e. rate of uninfected eels becoming infected) varied by host age and if there was evidence of disease associated mortality. to investigate recovery from parasite-induced swimbladder damage, 270 wild caught (presumably infected), individually tagged yellow eels were held in a freshwater recirculating system and fed a parasite-free diet for six months. Each month eels were x-rayed, weighted, and measured. The length and area of the swimbladder of each individually tagged eel were measured on x-ray images for temporal comparisons. at the end of the experiment, all eels were euthanized and dissected to determine infection intensity, SDI, and dissected swimbladder length. The trends of average monthly length ratio index (LRI; length of swimbladder to eel total length) and area of swimbladders were determined, as well as the relationships to SDI and infection intensity. Our field study showed that glass eels have a very low prevalence compared to elvers and yellow eels. Infection intensities of elvers and yellow eels varied by season and site and increased with total length. Swimbladder damage also varied by season and increased with total length. Infection intensity and swimbladder damage were non-linearly related. Force-of-infection was highest for age 2 eels and also varied by season, with the highest values in the winter and lowest in the early spring. Parasite-associated mortality was observed, with infected eels having an annual survival rate of 0.76 that of uninfected eels. Results from our x-ray experiment showed that LRI and area increased slightly through time. SDI also increased slightly over the course of the experiment, and SDI, LRI, and swimbladder area all were in agreement of improvement in swimbladder condition, however full recovery was not observed. In conclusion, the health of American eels in the Chesapeake Bay is adversely impacted by A. crassus, though that effect varies by season, system, length of the eel and whether infection level is being measured by infection intensity or swimbladder condition. Also American eels may have the ability to recover from A. crassus infection, but more work is needed to determine if this occurs in the wild.
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Attouchi, Farah. "Études par spectroscopie EELS de nanobulles d'hélium et de nanoparticules bimétalliques or-argent (Au@Ag)". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112318/document.
Testo completoAbstract (sommario):
Ce travail de thèse porte sur l'exploitation de la spectroscopie des pertes d'énergie des électrons,(EELS) résolue spatialement pour l'étude de systèmes de dimensions nanométriques. Cette technique étant réalisée avec un microscope électronique en transmission et à balayage, on parle d'expérience STEM-EELS dont le principal avantage est de permettre à la fois une caractérisation morphologique à l'échelle nanométrique et l'accès à une grande variété d'informations sur les propriétés physiques et chimiques des systèmes étudiés. Nous présentons ainsi deux cas d'étude portant sur : des nanobulles d'hélium confinées dans des matrices à base de fer et des nanoparticules métalliques or-argent de structure coeur- coquille. Ces deux études se basent sur le couplage entre imagerie microscopique à l'échelle nanomètrique et spectroscopie EELS en perte proche (Low-loss EELS).La première étude permet de sonder les densités et les pressions des bulles d'hélium en fonction de leur tailles en s'appuyant sur la détection et l'étude, bulle par bulle, du seuil K de l'hélium. Les résultats sont globalement en accord avec d'autres études dans le domaine, mais des densités très basses en hélium (<10 at nmˉ³) ont été mesurées de façon fiable pour la première fois.la deuxième étude concerne l'exploration des propriétés plasmoniques des nanoparticules bimétalliques Au@Ag en sondant les énergies et les localisations des modes plasmon de surface. On trouve un accord excellent entre les expériences et les calculs par éléments finis pour les positions des modes plasmon. La coquille en Ag semble déterminer leurs énergies, avec le coeur en Au ayant apparemment peu d'effet.Une part importante de ce travail concerne le développement des méthodologies d'acquisition et de traitement des données. Tout particulièrement l'utilisation des techniques d'analyses mutivariés (MVA) pour améliorer la détection de l'hélium dans les bullesThis thesis describes the application of high spatial resolution electron energy-loss spectroscopy (EELS) to the nanometre scale analysis of two rather di#erent types of sam- ple. EELS performed in the scanning transmission electron microscope (STEM) is known as STEM-EELS and offers the possibility of performing morphological characterisations simultaneously with access to a wide variety of information on the physical and chemical properties of the systems under study. Our two areas of study are nano-bubbles of helium in iron-based alloys and core-shell Au-Ag nano-particles. Both systems are studied via electron microscopic imaging and low-loss EELS (i.e. the spectral range below 50 eV). In the first case the helium densities and pressures in the bubbles are measured as a function of their size and the conditions in which they are generated, via the examination of the intensity and spectral position of the He-K excitation. The results are in broad agreement with othe studies in the field, but particularly lowhelium densities (< 10 at nmˉ³) have been reliably measured here for the first time.The second case concerns the exploration of the bi-metallic nano-particles plasmonic properties via the study of the surface plasmon mode energies and spatial localisations. Excellent agreement is found between experiment and finite element calculations for the plasmon modes. The outer Ag shell essentially fixes their energies, the Au core apparently having little effect.An important part of this work concerns the application of novel acquisition and data analysis methods. In particular the use of multivariate statistical analysis (MVA) is shown to facilitate the detection and quantification of helium in the bubbles
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Alemany, y. Palmer Mathias. "Caractérisation de lacunes d’oxygène dans les diélectriques à haute permittivité à destination des transistors « High-k Metal Gate »". Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2049/document.
Testo completoAbstract (sommario):
La présence de lacunes d’oxygène dans les diélectriques est supposée dégrader les propriétés électriques des transistors « high-k metal gate ». Nous avons donc étudié les possibilités d’une nouvelle méthodologie pour analyser ces défauts dans des couches minces de HfO2. Il s’agit d’utiliser des techniques optimisées pour la caractérisation de nano-dispositifs i.e. la spectroscopie de perte d'énergie des électrons (EELS) en microscopie électronique en transmission et la cathodoluminescence (CL)calibrées par la spectroscopie d’annihilation de positons (PAS). Des films de HfO2 ont été déposés par ALD et PVD sur des substrats de silicium. Pour les besoins du PAS, des couches d’épaisseur (10 à 100nm) supérieure au standard de la nanoélectronique ont été élaborées. D’après leurs analyses par DRX,RBS/NRA, MEB, TEM. Ces couches présentent majoritairement une structure complexe et un excès d’oxygène important. Les résultats PAS dépendent de la technique de dépôt et du traitement thermique.Leur comparaison avec des caractérisations électriques sur les couches les plus minces indique la génération de champs électriques dans la couche, à l’interface avec le substrat et dans le substrat. Ces observations confirment la présence de charges évoquée dans la littérature. Ces études ont permis de mettre au point la méthodologie et les conditions d’acquisition et d’analyse des spectres EELS et CL.Ceux-ci dépendent de la technique de dépôt et du traitement thermique. Cependant la qualité des couches n’a pas permis d’isoler les effets de la stoechiométrie. Ce travail ouvre de nombreuses perspectives pour approfondir la compréhension des phénomènes se déroulant au sein des nano-dispositifsThe presence of oxygen vacancies in high-k oxides is fore seen to have detrimental effects in high-kmetal gate MOS transistors. To validate this hypothesis, we investigate the possibility of using electron energy loss spectroscopy in an electron transmission microscope (EELS) and the cathodoluminescence(CL) calibrated by the positron annihilation spectroscopy (PAS) to analyze these defects in thin HfO2 layers.To develop this methodology, HfO2 films have been deposited both by ALD and PVD on silicon substrates. To make the samples adapted to the PAS depth resolution, the layers thicknesses (10 to100 nm) are higher than those used in microelectronics. According to XRD, RBS/NRA, MEB, TEM results, these layers present a complex structure and a large excess of oxygen.PAS results depend both on the deposition technique and on the heat treatment. They evidence the presence of electric fields in the oxide layer or at the interface with the substrate. Electrical measurements in the thinnest layers, confirm the presence of charges in the oxide layer as already mentioned in the literature. The sign of these charges changes with heat treatment and is in agreement with the PAS results.EELS improved data acquisition has been developed. The EELS and CL spectra have been analyzed using a systematic methodology allowing to extracting characteristic parameters. They depend on the deposition technique and the heat treatment. However, due to the poor quality of the layers, it has not been possible to isolate the effects of the stoichiometry. This work opens many perspectives to improve knowledge on phenomena occurring in devices
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Fu, Xiaoxiao. "Mesure de propriétés magnétiques locales de dispositifs par microscopie électronique à transmission". Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30061/document.
Testo completoAbstract (sommario):
L'EMCD, Energy Loss Magnetic Chiral Dichroism, est une technique récente, mise en œuvre dans le microscope électronique à transmission (TEM), qui utilise la spectroscopie de pertes d'énergie d'électrons (EELS). Elle a pour objectif la mesure du moment magnétique local d'un élément chimique donné. Son utilisation contribue à progresser dans la compréhension des phénomènes magnétiques à l'échelle nanométrique. Cette thèse propose d'élargir les domaines d'applications de l'EMCD. Nous avons exploité l'EMCD pour l'étude de films minces de MnAs épitaxiés sur un substrat de GaAs(001). Ce travail montre l'utilité de cette technique dans le cas de structures hexagonales présentant une anisotropie magnéto-cristalline élevée. Le rapport des moments orbital et de spin du Mn dans les films de MnAs ferromagnétique de structure hexagonale a été mesuré par EMCD et comparé à des calculs DFT, ceci le long des axes magnétiques facile, difficile et intermédiaire. Une rupture de l'ordre ferromagnétique a par ailleurs été observée et mesurée in situ dans le microscope grâce à un porte-objet chauffant, lors de la transition cristallographique de a-MnAs hexagonal à ß-MnAs quasi-hexagonal. La technique EMCD a également été mise en œuvre pour sonder le moment 4f de composés de terres rares à base de dysprosium. Il s'agissait d'étudier des super-réseaux DyFe2/YFe2. Les règles de somme ont été établies pour le seuil M4,5 du Dy. En outre, le couplage antiparallèle des moments Dy et Fe a été confirmé en comparant leurs signaux dichroïques et en prenant en compte la théorie dynamique de la diffraction. Ce travail de thèse illustre pour la première fois d'une part la faisabilité de la technique EMCD pour l'étude quantitative de l'anisotropie et des transitions magnétiques, et d'autre part son potentiel pour étudier les terres rares et leur moment 4f, ainsi que le couplage avec des éléments de transitionEMCD (Energy-Loss Magnetic Chiral Dichoism) is an emerging technique based on energy-loss spectroscopy (EELS) in a transmission electron microscopy (TEM). It aims at measuring the element-specific local magnetic moment of solids at a nanometer scale, and hence improving our understanding of magnetic local magnetic phenomena. This thesis presents the exploring work on developing the EMCD technique and its applications. We have applied EMCD to epitaxial MnAs thin films grown on a GaAs(001) substrate, extending the application of this technique to hexagonal structure with high magnetocrystalline anisotropy. The 3d orbital-to-spin moment ratio of Mn in hexagonal ferromagnetic MnAs along easy, hard and intermediate magnetic axes has been respectively estimated and then compared to DFT calculations. Moreover, a breaking of the ferromagnetic order in MnAs thin film, together with the crystallographic transition from hexagonal a-MnAs to quasi-hexagonal ß-MnAs, has been locally studied in-situ by modifying the temperature of the crystal inside the electron microscope. EMCD has also been settled to probe 4f moment in rare earth compounds, by investigating Dy-M4,5 edges in DyFe2/YFe2 superlattices. We have derived sum rules which are specified for 4f moment and applied them to the obtained dichroic signal over Dy-M4,5 edges. In addition, antiparallel coupling of Dy and Fe moments has been confirmed by comparing their dichroic signals, taking into account the dynamic diffraction effect. The work in this thesis illustrates for the first time the feasibility of EMCD technique for quantitative study of magnetocrystalline anisotropy and magnetic transition, and also proves its potential as a tool to investigate 4f moment as well as moment coupling in magnetic materials
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Dalem, Anak Agung Gde Raka, University of Western Sydney e Faculty of Science and Technology. "Demography and movement patterns of a population of eastern snake-necked turtles, Chelodina longicollis (Shaw, 1794)". THESIS_FST_xxx_Dalem_A.xml, 1998. http://handle.uws.edu.au:8081/1959.7/63.
Testo completoAbstract (sommario):
With 226-343 individual/ha, population density of Chelodina longicollis in the dams of the University of Western Sydney-Hawkesbury Richmond campus were in the range of other studies around Australia. Their size extremes (24.3 -223.3 mm) were within the range of previous studies, and the overall sex ratio was skewed toward males. The annual growth rates varied and were weakly correlated with animal size. Scute shedding occurred between September and April and peaked in December. Turtles were generally in excellent condition, indicating that sufficient food resources were available in local habitats. Only 3.4% of the population were in poor condition and few animals (8.8 %) carried signs of past injury. No gross abnormalities were recorded, however, there has been low levels of recruitment to the population compared with other Australian studies. Despite a maximum distance dams sampled of 2.8 km and ample evidence of interchange between dams, there was a great variation in animal size, cohort structure, sex ratio among dams. There are a range of factors which have the potential to bias sampling results. Turtles were not influenced by a dominance hierarchy or by the presence of eels, however, they appeared to be capable of avoidance behaviour when nets are set at a specific location. Different cohorts were caught differentially and this varied with month, season and year. In addition, catchability varied among cohorts. Juveniles were least likely, and sub-adult males were most likely, to be recaptured. In some dams there was evidence that animals moved at random while in others movement did not conform to this pattern. These results could not be accounted for in terms of dam size, physical structure of the dam or the distribution and abundance of vegetation.Master of Science (Hons)
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Melong, Tresha K. "Evaluation of Bar Rack Designs to Allow for the Downstream Passage of Silver American Eels at Hydropower Facilities". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/139.
Testo completoAbstract (sommario):
Concerns regarding the decreasing population of the American eel (reported by Castonguay et al. 1994; Haro et al. 2000) have led to design restrictions for hydropower facilities in the Eastern United States. However, the effects of these restrictions on eel passage and their impacts on power generation have not been fully researched. The goal of this study was to evaluate design parameters for bar racks that have potential to prevent entrainment of silver American eels, but also have minimal impacts on power generation. Hydraulic and biological assessments were used to determine the role of bar spacing, rack angle, and approach velocity on head loss across bar racks and the effects of bar spacing and approach velocity on eel bypass efficiency. The hydraulic assessments included computational fluid dynamics (CFD) analyses and laboratory experiments conducted in a re-circulatory flume at Alden Research Laboratory (Alden) in Holden MA. The flume allowed for determination of head losses across bar racks placed at angles of 45 and 90 degrees to the flow direction, with bar spacings of 0.75, 1.0 and 1.5 inches (19, 25 and 38 mm) and approach velocities of 1.5, 2.0 and 2.5 ft/sec (0.46, 0.61 and 0.76 m/s). Biological assessment, supported by funding from the Electric Power Research Institute (EPRI), used the same flume and included experiments with a 90 degree rack angle, bar spacings of 0.75 and 1.0 inches (19 and 25 mm), and approach velocities of 1.5 and 2.0 ft/sec (0.46 and 0.61 m/s). Bypass efficiencies, defined by the percentage of eels moving through the bypass, were evaluated for eels using three 2-hour replicate trials with nighttime releases of 30 eels per trial. Eel behavior in the vicinity of the racks was observed to the extent possible using a DIDSON acoustic camera. Experiments for the 90 degree configuration showed that the guidance efficiencies for the 0.75 inch (19 mm) spacing were greater than those for the 1.0 inch (25 mm) spacing, while the head losses for the 0.75 inch (19 mm) spacing exceeded the head losses for the 1.0 inch (25 mm) spacing by more than 10 percent. Linear regression analysis indicated that 53 percent of the variations in head width are explained by changes in the length of the eel. Results of the hydraulic evaluations were used to develop a new head loss equation that has a correlation coefficient of 98.6 percent. The results of the hydraulic and biological assessments provide a basis for quantifying the impacts of bar rack design on hydropower operation and downstream passage for American eels.
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B, Lavoie Francis. "Développement de nouveaux outils statistiques pour l'analyse d'images spectrales à faibles comptes". Mémoire, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/8146.
Testo completoAbstract (sommario):
Le projet de maîtrise était axé sur l’utilisation de traitements multivariables afin d’analyser adéquatement des ensembles de données provenant d’imagerie spectrale. Ce mémoire met premièrement en relief la particularité des détecteurs utilisés dans les microscopes, ainsi que les caractéristiques du bruit dans les données acquises.
L’analyse en composantes principales est une méthode qui se trouve dans plusieurs méthodologies de traitements de données d’imagerie spectrale. Celle-ci comprend certains désavantages, dont l’impossibilité d’extraire de réels spectres et des distributions de concentrations des composés en présence dans l’échantillon.
La résolution multivariée de courbes – moindres carrés alternatifs est une méthodologie qui a été popularisée dans les années 2000. Celle-ci permet de contrer les désavantages de l’analyse en composantes principales en extrayant des spectres physiquement cohérents et en créant des cartes de concentrations associées à ces spectres.
Cependant, ce mémoire démontre que cette méthode est inefficace lorsque les données ont un très faible ratio signal sur bruit et que plusieurs composants sont à extraire. Des améliorations à la résolution multivariée de courbes – moindres carrés alternatifs sont donc apportées. Notamment, la caractéristique du bruit des données, connue et documentée à la suite de nombreuses études, est utilisée afin d’améliorer la convergence de l’algorithme vers la bonne solution.
Ce mémoire démontre que ces améliorations sont appliquées avec succès sur des ensembles de données d’imagerie spectrale provenant de spectrométrie photoélectronique X, d’analyse dispersive en énergie et de spectroscopie des pertes d’énergie.