Thesis--Ph. D., University of Hong Kong, 1978.

No description available.

No description available.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.

Το απόθεμα του Ευρωπαϊκού χελιού (Anguilla anguilla), βρίσκεται σε ιστορικό ελάχιστο και η αλιεία του δεν είναι βιώσιμη, με τα δεδομένα να δείχνουν μείωση της στρατολόγησης της τάξης του 95%. Παρόμοιες πτωτικές τάσεις ισχύουν και στην Ελλάδα. Γι’ το λόγο αυτό ο κανονισμός της Ευρωπαϊκής Ένωσης 1100/2007 αναγκάζει όλα τα κράτη μέλη να προχωρήσουν στη σύνταξη διαχειριστικών σχεδίων για το χέλι προκειμένου να αυξηθούν οι διαφυγές αργυρόχελου στο 40% των διαφυγών που θα είχαμε αν δεν υπήρχαν οι ανθρωπογενείς παρεμβάσεις. Οι λόγοι μείωσης του αποθέματος του Anguilla anguilla είναι διάφοροι, με πιο σημαντικό για την παρούσα εργασία τις τεχνητές δομές που αποκλείουν κατάλληλους βιοτόπους για το χέλι. Στην παρούσα εργασία έγινε μια πρώτη τυπολογία των φραγμάτων, με ιδιαίτερη έμφαση στα φράγματα των Διαχειριστικών μονάδων 1 και 2 για το χέλι. Για το σκοπό αυτό, δημιουργήθηκε μια βάση δεδομένων, με στοιχεία από την Ελληνική Επιτροπή Μεγάλων Φραγμάτων και έρευνα στο google earth. Καταρχάς, τα αποτελέσματα της πρώτης τυπολογίας, έδειξαν ότι φράγματα σε ποσοστό 80% έχουν ύψος 0-50 m και από αυτά το 35% έχει ύψος 10-20m και το 25% 20-30m. Το 40% των μεγάλων φραγμάτων βρίσκεται σε απόσταση από τη θάλασσα έως 20km. Τα φράγματα που βρίσκονται πιο κοντά στην ακτή είναι τα Πουρνάρι ΙΙ (27km), Πουρνάρι Ι (30km), ο Λούρος (42km), το φράγμα του Φλόκα (17km), ο Στράτος (70km) και το φράγμα Αχυρών (11km). Το 35% των φραγμάτων χρησιμοποιείται αποκλειστικά για άρδευση και 10% αποκλειστικά για ύδρευση. Το 50% των φραγμάτων βρίσκεται σε υψόμετρο 0-200m και το 45% των φραγμάτων βρίσκεται σε υψόμετρο 200-900m. Η τυπολογία των φραγμάτων βάσει του όγκου του ταμιευτήρα έδειξε ότι τα περισσότερα φράγματα (60%) έχουν όγκο ταμιευτήρα έως 1.000.000m3 και ποσοστό 20% από 1.000.000 m3 έως 5.000.000m3. Στη συνέχεια, αξιολογήθηκαν τα παραπάνω φράγματα για την επίδραση τους τόσο στην ανάδρομη, όσο και στην κατάδρομη μετανάστευση. Ως προς την ανάδρομη μετανάστευση των χελιών, σύμφωνα με τα κριτήρια του Steinbach και με βάση τη σειρά του εμποδίου στην πορεία του χελιού, σημαντικά κρίθηκαν τα φράγματα του Στράτου, Πουρναρίου ΙΙ, Φλόκα, Μόρνου και Εύηνου. Ως προς την κατάδρομη μετανάστευση, σημαντικά κρίθηκαν τα φράγματα Καστράκι, Στράτος, Πουρνάρι Ι και ΙΙ, Λάδωνα, Φλόκα, Λούρου, καθώς είναι φράγματα που χρησιμοποιούνται -είτε αποκλειστικά είτε σε συνδυασμό με άλλες χρήσεις- για παραγωγή υδροηλεκτρικής ενέργειας. Παρ’ όλα αυτά, τα παραπάνω συμπεράσματα δεν είναι απόλυτα, καθώς πρέπει να αξιολογηθεί η αφθονία του χελιού στη συνολική μεταναστευτική του οδό. Στη Ευρώπη χρησιμοποιούνται τεχνικές παρεμβάσεις για τη διευκόλυνση της μετανάστευσης, όπως σκάλες χελιών ή διακοπή της λειτουργίας των τουρμπινών των υδροηλεκτρικών εργοστασίων. Στην Ελλάδα μεγάλο ποσοστό φράγματων έχουν μεγάλο ύψος (πάνω από 10m), όταν στην Ευρώπη ύψος πάνω από 2m θεωρείται σχεδόν απροσπέλαστο από τα χέλια, σύμφωνα με τα κριτήρια του Steibach. Τεχνικές λύσεις, όπως δημιουργία ειδικών χελιοδιαδρόμων, ίσως να μην ενδείκνυται λόγω αυτής της ιδιομορφίας. / The European eel (Anguilla anguilla) fishery is considered no more sustainable. In fact, present recruitment is about 1-5% of the maximum levels recorded in the past (early 70’s). Similar downward trends are observed in the Hellenic landings. For this reason, the EU regulation 1100/2007 obliges all Member States to propose management plans for the eel. The main objective is to increase silver eel escapement to the sea in order to participate in the reproduction of the population. The escapement should reach 40% of the escapement occurring without anthropogenic influence. The reasons reducing the stock of Anguilla anguilla are various, with the most important in this study, the artificial structures which exclude suitable habitat for eel. In the present a typology of dams was developed, with special emphasis on dams in Eel Management Units 1 and. For this purpose, we created a database with data from the Greek Dams Commission and from geographical elements about the position and altitude of the dams. The results revealed that 80% of the dams have heights varying between 0 and 50 m (35% have 10-20m height and 25% 20-30m). About 40% of large dams are located at less than 20km from the sea. The dams closest to the shore is Pournari II (27km), Pournari I (30km), Louros (42km), Stratos (70km), Floka (17km) and Axyron (11km). 35% of the dams are used for irrigation and only 10% exclusively for water supply. 50% of dams are in altitudes 0-200m and 45% of dams are in altitude 200-900m. The volume of 60% of the reservoirs was up to 1.000.000 m3 and 20% have reservoir volumes up to 5.000.000m3. The dams were evaluated for their effect both on upstream, and downstream eel migration. For the upstream migration of eels, according to the criteria of Steinbach and based on their sequential position from the sea, the major dams were Stratos, Floka, Pournari II, Mornos and Evinos. As for the downstream migration, significantly important dams are Kastraki, Stratos, Floka, Pournari I and II, Ladon, Louros, because these dams are used, either alone or in combination with other uses, for hydro-energy production. Nevertheless, these hierarchy is only based on geographical and technical elements and it have to be completed by the abundance of eel in the related ecosystems.. In Europe technical measures to facilitate the migration of eels comprise fish-laddes or shutting down the turbines of hydroelectric plants. In Greece, a large percentage of the dams have great height (over 10m), when in Europe height over 2m is considered almost impassable by the eel. In these cases, technical solutions, such as creating special eel passes, may be expensive, difficult and of reduced efficiency.

<p>I want delay publication of my dissertation until April 30 2013. Thanks.</p> / <p>Strontium titanate (SrTiO₃) has a wide range of applications in the electronic industry and attracts growing world-widely interest recently because of novel discoveries at its surfaces, interfaces and with selected dopants. The understanding of some of the structural properties of SrTiO₃ and its optical properties have been lagging due to limited characterization techniques available to study single monolayers and dopants in this material.</p> <p>In the present thesis, pure SrTiO₃ single crystals with (2x1) and c(4x2) surface patterns were synthesized and samples (Pr, Al) doped SrTiO₃ were prepared through ion implantation. The atomic and electronic structures of these samples were investigated by various high-resolution imaging and spectroscopic techniques available in an aberration-corrected transmission electron microscope. Particularly, the direct imaging of individual light atoms and vacancies within a bulk material containing heavier elements was demonstrated for the first time via the STEM-annular dark-field (ADF)/annular bright-field (ABF) images. In addition, the first electron energy-loss spectroscopy (EELS) 2-dimensional maps of dopants located in a lattice were obtained. These results provided a solid foundation regarding the mechanism of red light emission in doped SrTiO₃. More importantly, a new experimental approach allowing the effective extraction of weak EELS signals from low-dimensional defects was developed and successfully applied to understand the chemical state and coordination of Ti cations within a single monolayer on a reconstructured SrTiO₃surface and the local defect configurations of injected Pr⁺ and Al⁺ ions within SrTiO₃ single crystals.</p> / Doctor of Philosophy (PhD)

This thesis presents the fabrication of Sn-doped In2O3 nanostructures on a 50 nm thick SiN membrane and their characterization using monochromated electron energy loss spectroscopy (EELS). Rapidly annealed triangular structures of varying thicknesses (71 nm and 32 nm) and lengths (between 400 nm and 1200 nm) unveil a structural crystallization, as well as a blue-shift and narrowing of surface (first and second order modes) and bulk plasmon peaks as the free carrier concentration increases. Bulk peak positions shift from 515+/-39 meV to 628+/-36 meV for 71 nm thick triangles. The second order surface plasmon modes exhibit a greater blue-shift after annealing (93 meV) than the first order modes (36 meV), consistent with the trend found in boundary element method (BEM) simulations using ellipsometry data. The Richardson-Lucy (RL) deconvolution algorithm is employed to improve the effective energy resolution and reveal these surface plasmons as well as a substrate phonon at 100+/-19 meV. Low-loss EELS spectra for 32 nm thick triangles potentially show a blue-shifting bulk plasmon from 751+/-42 meV to 912+/-42 meV with decreasing triangle size. STEM imaging of the triangle structure cross-sections may show a clustering of oxygen vacancies and indium atoms that could be responsible for this blue-shift. Core-loss EELS spectra between 380-550 eV using the oxygen K-edge signal provide evidence of a change in the bonding across the ITO/SiN interface, although its effect on the electrical properties requires further investigation. / Thesis / Master of Applied Science (MASc) / The push towards smaller, faster electronic devices and sensing equipment has accelerated research into manipulating oscillating groups of electrons, or plasmons. So far, the building blocks of these next-generation systems use metals such as gold and silver; however, new materials must be explored for them to be commercially viable. Thin continuous films of transparent conductive oxides (TCOs) such as Sn-doped Indium Oxide (ITO) are already widely used in conventional silicon-based technologies, and in this work ITO nanostructures are fabricated to visualize their plasmonic response, in the hopes that they could be tailored towards plasmonic devices. The relationships between how these plasmons evolve with varying dimensions and the application of heat are explored using electron microscopy.

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

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 nanoparticules. / Over 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.

Le nettoyage laser Nd:YAG Q-switched (1064 nm) confère souvent aux surfaces nettoyées un aspect plus jaune que les autres techniques de nettoyage. Cet effet jaune peut conduire à l’obtention de contrastes de couleur inesthétiques si différentes techniques de nettoyage sont utilisées sur un même ensemble architectural, comme c’est le cas par exemple pour le portail des Valois de la basilique Saint-Denis près de Paris. Une des hypothèses émises pour expliquer le phénomène est que le jaunissement laser serait lié à la présence de résidus d’irradiation nanométriques formés par interaction du faisceau laser avec la salissure, en particulier les croûtes noires gypseuses communément observées sur les monuments en pierre. Dans le cadre de cette thèse, une méthodologie analytique multi-échelle allant jusqu’à l’échelle nanométrique a été développée pour observer et caractériser les composés néoformés responsables de la coloration jaune. Des éprouvettes de croûtes modèles à base d’hématite et de croûtes reconstituées à partir de croûte noire naturelle ont été élaborées. La croûte noire naturelle a été caractérisée pour déterminer les composés susceptibles de réagir au faisceau laser et donc de contribuer au jaunissement. Des oxydes de fer (hématite, magnétite, maghémite) et des cendres volantes silico-alumineuses issues de la combustion du charbon ont ainsi pu être mis en évidence. La nature chimique et structurale des produits de l’irradiation laser des éprouvettes a ensuite été examinée à l’aide d’un panel de techniques incluant entre autres la microscopie électronique à transmission (MET) couplée à la diffraction électronique et aux spectroscopies de rayons X par dispersion d’énergie (EDX) et de perte d’énergie des électrons (EELS). Des nanostructures cristallisées sous forme de nano-sphères et de nano-résidus ont ainsi pu être observées. La caractérisation de la composition chimique à l’échelle nanométrique a permis de révéler la présence de fer dans toutes les nanostructures. Une étude approfondie de la couleur a en outre permis de relier les propriétés colorimétriques du processus de jaunissement à la nature des nano-composés néoformés par irradiation laser. D’autre part, le portail des Valois de la basilique Saint-Denis a été le sujet d’une étude de cas qui est venue complémenter la recherche tout en ancrant l’étude dans la réalité du monde de la conservation des monuments historiques. Enfin des essais de remédiation ont démontré les potentialités de l’utilisation d’un rayonnement UV pour atténuer ou ne pas produire de jaunissement. In fine, ce travail a permis de démontrer que le phénomène de jaunissement laser observé à l’échelle macroscopique est intimement lié à des transformations de matière à l‘échelle nanométrique, induites par l’interaction du rayonnement laser avec les oxydes de fer et les cendres volantes présents dans les encrassements. / Nd:YAG Q-Switched laser cleaning of soiled stone at 1064 nm can sometimes result in yellower appearances than other conventional cleaning techniques. This yellowing effect can lead to unsightly colour contrasts if different cleaning techniques are used on the same architectural complex, as is the case for the Valois Portal of the Saint-Denis basilica near Paris. One argument made to explain the phenomenon is that the laser yellowing is linked to the creation of nano-sized irradiation residues through the laser beam interaction with soiling matter such as black gypseous crusts. In this study, a multi-scale analytical method extending to the nanoscale has been used to observe and characterize the neo-formed compounds accountable for the yellow discoloration. Samples of model crusts containing hematite and reconstituted crusts prepared with natural black crust have been synthetized. The natural black crust has been characterized in order to identify the compounds that may react under the laser beam and thus contribute to the yellowing effect. Iron oxides (hematite, magnetite and maghemite) and aluminosilicate fly-ashes originating from coal combustion have been discovered. The chemical and structural nature of irradiation products has then been investigated by several techniques including in particular transmission electron microscopy (TEM) coupled with electronic diffraction and energy-dispersive X-ray (EDX) and electron energy-loss (EELS) spectroscopies. Iron containing nanostructures crystallized in the form of nano-spheres and nano-residues have been evidenced and characterized. By studying thoroughly the colour, the colorimetric properties of the yellowing process have been linked to the nature of the neo-formed compounds. Furthermore a case study on the Valois Portal has completed the research while setting it within the reality of the conservation world. Finally experiments with UV light have shown the promising potentiality of this tool as a remedy to the yellowing effect. In summary, this study has demonstrated that the yellowing phenomenon observed at the macroscale is intimately linked to matter transformations occurring at the nanoscale, induced by the interaction between the laser beam and the iron oxides and fly-ashes found in black crusts.