Global ETD Search

131	Tidal and sediment dynamics of a partially mixed, micro-tidal estuary O'Callaghan, Joanne M. January 2005 (has links) [Truncated abstract] The expansion of human populations in coastal land margins has resulted in major modifcations to estuarine ecosystems. The use of numerical models as predictive tools for assessing remediation strategies is increasing. However, parameterisation of physical processes, developed mainly through field investigations, is necessary for these models to be reliable and effective management tools. The physical processes in micro–tidal diurnal tidal systems are relatively unknown and the current study examines field measurements obtained from the upper Swan River estuary (Western Australia), a diurnal, partially mixed system during the summer when the freshwater discharge is negligible. The aims of the study were to characterise, temporally and spatially, the dominant physical processes and associated sediment resuspension. Variability at three dominant time-scales were examined: 1) sub–tidal oscillations (∼5 to 10 days) resulting from local and remote forcing; 2) tidal (∼ 24 hours) due to astronomical forcing; and 3) intra-tidal (∼2 to 3 hours) resulting from the interaction between tidal constituents. Circulation in estuaries is widely accepted in the literature to be dominated, in varying proportions, by tidal range, freshwater discharge and gravitational circulation. In the upper Swan River estuary sub–tidal oscillations were responsible for the largest upstream displacement of the salt wedge in the absence of freshwater discharge. Moreover, these sub–tidal fluctuations in water level modified the ‘classic’ estuarine circulation. The dynamics of diurnal tides are largely controlled by the tropic month, which oscillates at a slightly different period to the lunar month, resulting in the spring–neap tidal cycle to be sometimes different from syzygy. The phase lag between the diurnal (O1 + K1) and semi-diurnal (M2 + S2) constituents, at the seasonal time scale cause the maximum tidal range to be near the solstice. Over a 24–hour tidal cycle this phase lag is manifested as an intra–tidal oscillation that occurs on the flood tide. Turbidity events that last ∼1 to 2 hours occur during the intra–tidal oscillation, but are not related to maximum shear stress predicted from the mean flow characteristics. The increases in turbidity during the intra–tidal oscillation is, however, correlated with the near–bed Reynolds fluxes. During the intra–tidal oscillation advection opposes the estuarine circulation in the near–bed region, promoting vertical shear that results in destratifcation of the water column. The turbulent mixing generated at the interface and in the near–bed region coincide with resuspension events. Similar turbidity data have often been disregarded and documented as being ‘spikes’ based on the premise that the mean flow was below a critical level to resuspend sediment. Resuspension events were not simply related to mean processes and may be controlled by turbulent instabilities generated when tidal currents reverse during an intra-tidal oscillation Swan River Estuary (W.A.) Estuarine dynamics Diurnal tides Sub-tidal oscillations Sediment resuspension
132	Η λειτουργία του άξονα υποθάλαμος–υπόφυση–επινεφρίδια σε νοσηλευόμενους ασθενείς της Παθολογικής Κλινικής με διαφορετικής βαρύτητας νοσήματα Μαργέλη, Θεοδώρα 03 May 2010 (has links) Ο άξονας Υποθάλαμος – Υπόφυση – Επινεφρίδια και το συμπαθητικό νευρικό σύστημα είναι τα περιφερικά σκέλη του συστήματος απάντησης στο στρες, με στόχο τη διατήρηση της ομοιόστασης του οργανισμού. Ανεπάρκεια ανταπόκρισης των επινεφριδίων στη σοβαρή νόσο μπορεί να παρουσιαστεί χωρίς προφανή βλάβη στον άξονα ΥΥΕ. Σε πολλούς ασθενείς με σοβαρή νόσο, τα επίπεδα κορτιζόλης παρά το ότι είναι αυξημένα, δεν είναι αρκετά ώστε να εκδηλώσουν επαρκή επινεφριδιακή απάντηση σε σχέση με τη σοβαρότητα της νόσου. Η βέλτιστη απάντηση του άξονα ΥΥΕ σε καταστάσεις νόσου παραμένει υπό αμφισβήτηση. Η διάγνωση της πιθανής σχετικής με τη νόσο παροδικής επινεφριδιακής ανεπάρκειας και η ανάγκη για χορήγηση κορτικοστεροειδών είναι ακόμη υπό συζήτηση. Σκοπός της μελέτης αυτής είναι η εκτίμηση της επινεφριδιακής απάντησης ανάλογα με τη σοβαρότητα της νόσου στην οξεία φάση της νόσου και η μελέτη του άξονα ΥΥΕ τόσο στην οξεία φάση, όσο και στην ανάρρωση. Για το σκοπό αυτό μελετήθηκαν 56 νοσηλευόμενοι ασθενείς με διαφορετικής βαρύτητας νόσημα (ΑΕΕ, ήπια νόσο, σήψη και σοβαρή σήψη), καθώς και 15 υγιή άτομα – μάρτυρες. Σε όλους τους συμμετέχοντες, κατά την εισαγωγή τους (1η ημέρα), μετρήθηκε η κορτιζόλη και η ACTH. Κατόπιν εφαρμόστηκε η δοκιμασία με χαμηλή δόση (1μg) κορτικοτροπίνης και δύο ώρες αργότερα η δοκιμασία με τη συνήθη δόση (250μg) κορτικοτροπίνης. Τη δεύτερη ημέρα νοσηλείας στους ασθενείς μετρήθηκε η ημερήσια διακύμανση της κορτιζόλης. Κατά την 5η -6η ημέρα νοσηλείας (φάση ανάρρωσης) έγινε επανάληψη των δοκιμασιών σε 15 ασθενείς (7 με σήψη και 8 με σοβαρή σήψη). Από την επεξεργασία των αποτελεσμάτων, στην ομάδα των ΑΕΕ και της σοβαρής σήψης παρατηρούνται οι υψηλότερες τιμές κορτιζόλης, καθώς επίσης και εξάλειψη της ημερήσιας διακύμανσης της κορτιζόλης. Παράλληλα, σε όλους τους ασθενείς παρατηρείται διαχωρισμός των επιπέδων κορτιζόλης και ACTH. Η αύξηση της κορτιζόλης (Δmax κορτιζόλης) μετά από διέγερση με 1 μg κορτικοτροπίνης δεν διέφερε μεταξύ των ομάδων νόσου, ενώ η Δmax κορτιζόλης μετά από διέγερση με 250μg κορτικοτροπίνης παρουσίασε οριακά σημαντική διαφορά με μια τάση να είναι υψηλότερη στην ομάδα των υγιών μαρτύρων. Η συχνότητα της απάντησης ή μη στη συνήθη δοκιμασία με βάση το κριτήριο Δmax κορτιζόλης <9 δεν διέφερε μεταξύ των υγιών και των ομάδων ασθενών, ενώ όλοι οι ασθενείς επιβίωσαν χωρίς τη χορήγηση κορτικοειδών, ανεξάρτητα από την απάντηση ή μη στις δοκιμασίες με ACTH. Στους ασθενείς με σήψη, η Δmax κορτιζόλης μετά από διέγερση με 250 μg κορτικοτροπίνης ήταν υψηλότερη στη φάση ανάρρωσης σε σχέση με την οξεία φάση, ενώ στους ασθενείς με σοβαρή σήψη η αντίστοιχη διαφορά δεν ανεδείχθη σε σημαντικό βαθμό. Η βασική κορτιζόλη ήταν υψηλότερη στην οξεία φάση σε σχέση με τη φάση ανάρρωσης και στις δύο ομάδες νόσου. Συμπερασματικά, διαπιστώνονται ήπιες αλλαγές στον άξονα ΥΥΕ, ανάλογα με τη σοβαρότητα του νοσήματος. Παρόλα αυτά, δεν επιβεβαιώνεται η ύπαρξη σχετικής επινεφριδιακής ανεπάρκειας σε μη βαριά νοσούντες ασθενείς. / Relative corticosteroid insufficiency maybe is common in critically ill patients, associated with poor outcome; however it is not known the response of the hypothalamic-pituitary-adrenal (HPA) axis in nursed patients. Our aim was to evaluate the response of HPA axis in non-critically ill nursed (NCIN) patients. Fifty -six nursed patients, divided into four groups (stroke, mild disease, sepsis and severe sepsis) as well as a control group (n=15) were studied. At admission (day 1), cortisol and ACTH measured and a low - dose (1mug ) corticotropin test was performed, followed two hours later by a standard-dose (250 mug). Diurnal variation of cortisol was obtained on day 2. A second identical set of low and standard set of corticotropin tests were performed on day 5 or 6 (recovery phase). In patients with stroke and severe sepsis cortisol had the highest values and its diurnal variation was abolished. Dissociation of ACTH and cortisol was found in all patients. The Deltamax of cortisol after the 1 mug corticotropin test did not differ among the groups while after the 250 mug corticotropin test was borderline higher in controls. The ratio of responders (Deltamax of cortisol >/= 9 mug/dL) to non-responders after 1 mug or 250 mug corticotrophin tests did not differ among patients and controls. All patients had a good outcome without glucocorticoid treatment. In conclusion, mild alterations of the HPA axis, depending on the severity of illness occurred. However, relative corticosteroid insufficiency in non-critically ill nursed patients did not confirm. Απάντηση στο στρες 616.450 75 Hypotalamic-pituitary-adrenal axis Relative adrenal insufficiency ACTH stimulation test Dissociation of ACTH and cortisol Stress response
133	Analyse rétrospective des relations nappe-végétation de sous-bassins versants forestiers de la rivière Leyre / Retrospective analysis of vegetation-watertable relationship in small forested watershed of Leyre river Guillot, Marie 08 December 2011 (has links) Dans les Landes de Gascogne, le fonctionnement de la nappe phréatique superficielle plio-quaternaire est très liée au fonctionnement de la végétation subjacente. Pour comprendre la variabilité à l'échelle du paysage de la productivité de ces forêts, il est important de passer de l'échelle de la parcelle à celle du bassin versant. La mise en place d'un dispositif de suivi de type bassins versants jumelés à l'échelle de petits bassins versants forestiers situés dans le Massif Landais : les bassins versants du Tagon (Biganos) et du Bouron (Belin-Beliet) a permis le suivi hydrologique et piézométrique de la nappe plio-quaternaire. Le dispositif inclut une modification du couvert végétal par l'occurrence de deux tempêtes successives à 10 ans d'intervalle. La collecte de données cartographiques, numériques et statistiques a permis une reconstitution de l'usage des terres et des classes d’âges des peuplements forestiers, pour la période 1984- 2010 sur les deux bassins versants. Cette reconstitution a ainsi permis de retrouver l'évolution des stocks de carbone et de biomasse des peuplements pour les deux sites expérimentaux et de quantifier l'impact d'une tempête sur l'organisation paysagère des peuplements (âge et variabilité). Le lien entre les forêts de Pin maritime et la nappe phréatique plio-quaternaire a été mis en évidence par : (1) l'étude de la croissance des arbres pour des sites où la profondeur de la nappe était contrastée, au travers d'une étude dendrologique et (2) l'analyse d'oscillations journalières sur les séries chronologiques des fluctuations demi-horaires du niveau phréatique, qui peuvent être attribuées à l’évapotranspiration journalière. La compréhension des liens entre variables hydroclimatiques et quantité de bois produite, i.e. largeur de cerne, de manière rétrospective, a permis d'identifier les facteurs de variabilité et les facteurs limitants pour chaque type de site, en lien avec la profondeur de la nappe superficielle. L’analyse des chroniques piézométriques a mis en lumière l'importance des prélèvements journaliers dans la vidange de l'aquifère. La dernière partie de ce travail pose les bases d'une future modélisation couplée végétation-nappe pour le bassin versant du Bouron. La reconstitution spatiale du fonctionnement de la nappe phréatique a été entreprise en régime stationnaire puis en régime dynamique avec le modèle NEWSAM de l'Ecole des Mines de Paris. Les facteurs expliquant le fonctionnement de l'aquifère et les flux d'eau à l'échelle de la petite région sont identifiés. L'effet de la recharge, issue du modèle de végétation pour le Pin maritime GRAECO, est en particulier testé, via une étude de sensibilité, en relation avec les différences de recharge induites par les différents types de couverts, et en particulier, l'âge des peuplements. Les points clefs à améliorer sont identifiés afin de perfectionner les modèles utilisés, et de reproduire de façon réaliste le fonctionnement de petits bassins versants dans la région. / In the Landes de Gascogne area, the functioning of the shallow plio-quaternary water-table is tightly linked with the functioning of the top vegetation. In order to understand the variability of forest productivity at the landscape scale, there is a need to move forward the stand scale to the watershed scale. Part of this study was to setup hydrological equipment of paired-watershed, representative of the forested plain in the Leyre watershed, considering water-table level and hydrologic measurement. The selected sites were the Bouron watershed (Belin-Beliet) and the Tagon watershed (Biganos), which were contrastingly impacted by two storms within the last 10 years. The land-cover cartography was obtained with satellite, in-situ and statistical data, on a retrospective basis, accross the 1984-2010 period. Those maps give the evolution of the land use and the Pinus pinaster stand age. The reconstitution of the age structure thought time, converted to carbon and biomass stock, are showing the impact of a storm, comparing the control watershed to the damaged one. The link between forests and water-table was explored on : (1) the growth of trees developing in sites with contrasted water-table levels, by way of dendrological measurement and (2) the analysis of diurnal oscillation on the water-table level signal, attributed to vegetation removal. The understanding of the link between hydroclimatic data and wood production, i.e., ring width, shows that limitating factors should not be the same across different sites. In particular, water-table deeper than 3 meter is not a determinant resource for growth, but nutriment may be more limitating at those sites. On the other side, discharge of the water-table cannot be dissociated to evapotranspiration reprise. Oscillations in the diurnal signal of water-table level shows that this removal can be determinant, and deeper than expected according to the vegetation cover. The last part of this work build the basis of a future model, representing the coupling between vegetation and water-table at the watershed scale. The dynamic of the aquifer was simulated in permanent and transient state with the NEWSAM hydrogeological model (Ecole des Mines, Paris). Different processes were identified as key factor to explain water-table functioning, such as recharge effect, zone vadose impact and surface drainage. The recharge effect, coming from GRAECO, was particularly tested, thought a sensitivity analysis, in relation with growing proportion of young forest stand (less than 5 years old). Points to improve and refine are identified in order to perfect the two models used here. Pinus pinaster Bassin versant Nappe plio-quaternaire Fonctionnement hydrogéologique Bilan de carbone Dendrochronologie Oscillations diurnes de nappe Modélisation Pinus pinaster Watershed Hydrogeological functioning Carbon budget Retrospective cartography of land use Dendrochonology Diurnal fluctuation of water-table level Plio-quaternary water-table Modelisation
134	Hydraulic Investigations of the Salar de Uyuni, Bolivia Sieland, Robert 12 December 2014 (has links) With a surface area of about 10,000 km², the Salar de Uyuni is the largest salt flat in the world. It is located at an altitude of 3,653 m on the Altiplano, a high plateau in the south of the Bolivian Andes. The Salar de Uyuni consists of an alternating sequence of highly porous salt layers (mainly composed of halite) and lacustrine clay sediments. The pore volume of the uppermost salt layer which has a thickness of up to 11 m is filled by brine. The brine contains high amounts of Mg, K, Li and B. The element lithium is an especially important raw material for the production of batteries. Thus, it plays an important role for the development of the electric mobility. With this background, extensive hydrogeological exploration activities were carried out at the Salar de Uyuni in the context of this dissertation. The hydraulic properties of the uppermost salt crust and the physical properties (density and viscosity) of the brine must be characterized. In order to do this, several core drillings were made, observation wells were installed, brine samples were taken and pumping tests were conducted between 2009 and 2012. The stratigraphic documentation of the obtained sediment cores provided insights about the deposit structure and the upper salt layer thickness. The determination of the salt core porosity was carried out by three different methods: (a) by using X-ray computed tomography, (b) gravimetrically by saturation with 2-octanol and (c) by completion of the core volume with plasticine and calculation of the porosity under consideration of the particle density of the salt. The laboratory investigations showed a depth-dependent porosity distribution in the upper salt layer. The uppermost 2 m were characterized by very high porosity values between 30 and 39%. However at greater depth, the total porosity decreases on average to 13.5%. Geochemical analyses of brine samples confirmed the general spatial distribution of the lithium concentrations as already published by previous studies. On the basis of the lithium distribution in the brine, the thickness of the upper salt layer and the depth-dependent porosity distribution, the total lithium deposit in the Salar de Uyuni was calculated to be about 7 million tons. The evaluation of the pumping tests under consideration of the density and viscosity of the pumped brine showed that the salt has a very high permeability in the horizontal direction. In contrast, flow-through experiments on drill cores indicated a clear vertical anisotropy of the permeability. This is caused by the inhomogeneous sediment stratification for instance by interbedded fine gypsum or clay lamina. Thus, horizontal brine movements are possible, but a deep vertical flow component can hardly be expected. This assumption is confirmed by radiocarbon dating the brine samples from different salt depths. The influence of annual floods during the rainy season could be observed by long-term brine level measurements. Throughout the time-series analysis, distinct periodic brine fluctuations of a few centimeters per day could be identified during the dry season. These daily fluctuations indicated an impermeable crust probably formed by the evaporation of near-surface brine and subsequent crystallization of salts in the pore volume. Thus, daily temperature and atmospheric pressure changes could directly affect the brine level. Due to the extensive hydrogeological investigations, this dissertation contributes to the essential understanding of the hydraulic conditions in the Salar de Uyuni. / Mit einer Fläche von rund 10.000 km² ist der Salar de Uyuni die größte Salz-Ton-Ebene der Welt. Er befindet sich in einer Höhe von 3653 m NN im Altiplano, einer Hochebene im Süden der bolivianischen Anden. Der Salar de Uyuni besteht aus einer Wechsellagerung von hochporösen Salzschichten (überwiegend aus Halit bestehend) und lakustrinen Tonsedimenten. Die Porenräume der obersten bis zu 11 m mächtigen Salzschicht sind mit einer Sole gefüllt, die hohe Gehalte an Mg, K, Li und B aufweist. Insbesondere das Element Lithium ist ein wichtiger Rohstoff u.a. für die Herstellung von Batterien und spielt damit eine bedeutende Rolle bei der Entwicklung der Elektromobilität. Vor diesem Hintergrund wurden im Rahmen der vorliegenden Dissertation umfassende hydrogeologische Erkundungsarbeiten am Salar de Uyuni durchgeführt, um die hydraulischen Eigenschaften der obersten Salzkruste sowie die physikalischen Eigenschaften (Dichte und Viskosität) der Sole zu charakterisieren. Dazu wurden zwischen 2009 und 2012 zahlreiche Kernbohrungen abgeteuft, Beobachtungsbrunnen installiert, Soleproben entnommen und Pumpversuche durchgeführt. Die stratigraphische Dokumentation der gewonnenen Bohrkerne lieferte Erkenntnisse zur Ablagerungsstruktur und zur Mächtigkeitsverteilung der obersten Salzschicht. Die Bestimmung der Porosität der Salzkerne erfolgte mit drei verschiedenen Methoden: (a) mittels Computertomographie, (b) gravimetrisch durch Aufsättigung mit 2-Oktanol und (c) durch Volumenergänzung der Kernproben mit Plastilin und Berechnung der Porosität unter Einbeziehung der Reindichte des Salzes. Die Laboruntersuchungen zeigten eine tiefenabhängige Porositätsverteilung in der obersten Salzschicht. Während die obersten 2 m durch sehr hohe Porositäten zwischen 30 und 39% gekennzeichnet sind, nimmt die Gesamtporosität in größerer Tiefe auf durchschnittlich 13.5% ab. Geochemische Analysen von Soleproben bestätigten die grundsätzliche räumliche Verteilung der Lithium-Konzentrationen, wie sie bereits durch frühere Studien veröffentlicht wurde. Auf Basis der Lithium-Verteilung in der Sole, der Mächtigkeit der oberen Salzschicht sowie der tiefenabhängigen Porositätsverteilung wurde ein Lithium-Vorkommen im Salar de Uyuni von rund 7 Millionen Tonnen berechnet. Die Auswertung der Pumpversuche unter Berücksichtigung der Dichte und Viskosität der geförderten Sole zeigte, dass das Salz eine sehr hohe Permeabilität in horizontaler Richtung aufweist. Allerdings zeigten Durchströmungsversuche an Bohrkernen eine deutliche vertikale Anisotropie der Permeabilität, was auf die inhomogene Sedimentschichtung durch z.B. eingeschaltete feine Gips- oder Tonschichten zurückzuführen ist. Somit sind zwar horizontale Solebewegungen möglich, jedoch ist kaum mit einer tiefgreifenden vertikalen Strömungskomponente in der Salzschicht zu rechnen. Diese Vermutung wird durch 14C-Altersdatierungen von Soleproben aus unterschiedlichen Tiefen des Salzes bestätigt. Der Einfluss der jährlichen Überschwemmungen während der Regenzeit konnte anhand von Langzeitmessungen des Solespiegels beobachtet werden. Im Zuge der Zeitreihen-Analyse zeigten sich zudem ausgeprägte periodische Tageschwankungen von einigen Zentimetern während der Trockenzeit. Diese deuten darauf hin, dass durch Verdunstung oberflächennaher Sole und damit einhergehender Kristallisation von Salzen im Porenraum eine undurchlässige Kruste entsteht. Dadurch haben tägliche Temperatur- und Luftdruckschwankungen direkten Einfluss auf den Solespiegel. Die vorliegende Dissertation trägt aufgrund der umfangreichen hydrogeologischen Untersuchungen wesentlich zum Verständnis der hydraulischen Verhältnisse im Salar de Uyuni bei. / Con una superficie de aproximadamente 10.000 kilómetros cuadrados el Salar de Uyuni es el mayor lago de sal en el mundo. Se encuentra a una altura de 3.653 m sobre el nivel del mar en el altiplano en el sur de los Andes bolivianos. El Salar de Uyuni consiste en una alternancia de capas de sal altamente porosa (que consiste predominantemente de halita) y lacustre sedimentos de arcilla. La capa superior de sal tiene un espesor de hasta 11 metros. Los espacios de poros del sal se llenan con una salmuera que contiene altos contenidos de Mg, K, Li y B. En particular, el elemento litio constituye una importante materia prima para la producción de baterías que son utilizadas en la construcción de vehículos eléctricos. Bajo estos antecedentes y en el contexto de la presente tesis, se han desarrollado extensas actividades de exploración hidrogeológica en el Salar de Uyuni. Las propiedades hidráulicas de la corteza de sal superior y las propiedades físicas (densidad y viscosidad) de la salmuera debían caracterizadas. Para ello, entre 2009 y 2012 se realizaron varios perforaciones con la finalidad de obtener muestras de núcleos, se instalaron pozos de supervisión, se realizaron pruebas de bombeo y se tomaron muestras de salmuera. La documentación estratigráfica de los núcleos de perforacíon proporciona conocimientos para la estructura de los depósitos y para el espesor del superior capa de sal. La porosidad de los núcleos de sal fue determinada por medio de tres métodos diferentes: (a) por tomografía computarizada (TC), (b) gravimétricamente mediante la saturación con 2-octanol y (c) mediante de compleción del volumen del núcleo con plastilina y computacíon de la porosidad en atención a la densidad real del sal. Las investigaciones de laboratorio demostraron una distribución de la porosidad dependiente de la profundidad en la capa superior de sal. Mientras que la parte superior 2 m se caracterizan por altas porosidades entre el 30 y 39%, la porosidad total decrese en una profundidad mayor a un promedio de 13,5%. Los análisis geoquímicos de muestras de salmuera confirmaron la distribución espacial fundamental de las concentraciones de litio, como ya se ha publicado por estudios anteriores. A base de la distribución de litio en la salmuera, el espesor de la capa superior de sal, y la porosidad dependiente de la profundidad determinaron que todos los recursos minerales de litio en el salar de Uyuni son alrededor de 7 millones de toneladas. La evaluación de las pruebas de bombeo en consideración de la densidad y la viscosidad de la salmuera transmitido mostró que la sal generalmente tiene una permeabilidad muy alta. Pero, las pruebas de flujo en muestras de núcleo mostró una anisotropía significativa de la permeabilidad con la profundidad, que se debe a una estratificación de sedimentos no homogénea debido las láminas finas de yeso o arcilla intercaladas. Por lo tanto, es correcto que los movimientos de salmuera horizontales son posibles, pero es poco probable que movimientos verticales de salmuera ocurran. Esta hipótesis se ve confirmada por la datación por radiocarbono de muestras de salmuera de diferentes profundidades de la sal. El impacto de las inundaciones anuales durante la estación lluviosa se puede observar a partir de las mediciones a largo plazo del nivel de salmuera. En el curso del análisis de series de tiempo también mostraron pronunciadas variaciones diarias periódicas de unos pocos centímetros en la estación seca. Esto sugiere que hay una corteza impermeable que se forma por evaporación de salmuera cerca de la superficie y la cristalización de sales en el espacio de los poros. En esta manera, las fluctuaciones diarias de temperatura y de preción de aire influyen directamente el nivel de salmuera. Gracias a las extensas investigaciones hidrogeológicas realizadas, la presente tesis contribuye significativamente a la comprensión de las condiciones hidráulicas en el Salar de Uyuni. info:eu-repo/classification/ddc/550 ddc:550
135	An SEM Study of Blastodinium Parasitism of Estuarine Calanoid Copepods: Impact on Mankind Toma, Nicholas, Kunigelis, Stan C, PhD 07 April 2022 (has links) Blastodinium, a genus of the phytoplanktonic dinoflagellates, was found to be inhabiting the gut region of the copepod species Labidocera. Copepods are ubiquitous in aquatic environments, being the most numerous multicellular organisms on planet earth. Being primary consumers, they play important ecological roles, passing energy from one trophic level to the next. As zooplankton, estuarine copepods contribute substantially to carbon cycling as they undergo diurnal migration to avoid daylight UV-B damage and surface water predation. Blastodinium are presumed to infect copepods via ingestion of zoospores by juvenile hosts, who function as microhabitats for acquiring nutrients in non-photosynthetic species or in nutrient-limited environments. Blastodinium may hinder reproduction of copepod hosts, thereby influencing local copepod populations and, by extension, food webs up to humanity. Copepod populations may also help contain disease spread, such as malaria and Dengue fever, through their consumption of mosquito larvae in standing water. Further evaluation of copepods for Blastodinium may help shed light on the limited knowledge of this species and the nature of its relationship with copepods, as well as its effects on copepod populations and the higher order consequences of its parasitism. copepods dinoflagellates blastodinium electron microscropy they play important ecological roles Parasitology
136	Intermittent hypoxia elicits a unique physiological coping strategy in Fundulus killifish Borowiec, Brittney G. January 2019 (has links) Fish encounter daily cycles of hypoxia in the wild, but the physiological strategies for coping with repeated cycles of normoxia and hypoxia (intermittent hypoxia) are poorly understood. Contrastingly, the physiological strategies for coping with continuous (constant) exposure to hypoxia have been studied extensively in fish. The main objective of this thesis was to understand how Fundulus killifish cope with a diurnal cycle of intermittent hypoxia, an ecologically relevant pattern of aquatic hypoxia in the natural environment. To do this, I characterized the effects of intermittent hypoxia on hypoxia tolerance, oxygen transport, metabolism, and the oxidative stress defense system of killifish, and compared these effects to fish exposed to normoxia, a single cycle of hypoxia-normoxia, and constant hypoxia. Specifically, I studied the following topics: (i) how acclimation to intermittent hypoxia modifies hypoxia tolerance, and the hypoxia acclimation response of Fundulus heteroclitus (Chapter 2), (ii) metabolic adjustments occurring during a hypoxia-reoxygenation cycle (Chapter 3), (iii) how acclimation to intermittent hypoxia alters O2 transport capacity and maximal aerobic metabolic rate (Chapter 4), (iv) the effects of hypoxia and reoxygenation on reactive oxygen species and oxidative stress (Chapter 5), and (v) variation in hypoxia tolerance and in the hypoxia acclimation responses across Fundulus fishes (Chapter 6). Killifish rely on a unique and effective physiological strategy to cope with intermittent hypoxia, and that this strategy is distinct from both the response to a single bout of acute hypoxia-reoxygenation (12 h hypoxia followed by 6 h reoxygenation) and to chronic exposure to constant hypoxia (24 h hypoxia per day for 28 d). Key features of the acclimation response to intermittent hypoxia include (i) maintenance of resting O2 consumption rate in hypoxia followed by a substantial increase in O2 consumption rate during recovery in normoxia, (ii) reversible increases in blood O2 carrying capacity during hypoxia bouts, (iii) minimal recruitment of anaerobic metabolism during hypoxia bouts, and (iv) protection of tissues from oxidative damage despite alterations in the homeostasis of reactive oxygen species and cellular redox status. Of these features, (i) is unique to intermittent hypoxia, (ii) also occurs in fish exposed to acute hypoxia-reoxygenation, and (iii) and (iv) are observed in both fish acclimated to intermittent hypoxia as well as those acclimated to constant hypoxia. This is the most extensive investigation to date on how fish cope with the energetic and oxidative stress challenges of intermittent hypoxia, and how these responses differ from constant hypoxia. This thesis adds substantial insight into the general mechanisms by which animals can respond to an ecologically important but poorly understood feature of the aquatic environment. / Dissertation / Doctor of Philosophy (PhD) / Oxygen levels in the aquatic environment are dynamic. Many fishes routinely encounter changes in oxygen content in their environment. However, we have very little understanding of how cycles between periods of low oxygen (hypoxia) and periods of high oxygen (normoxia) affect the physiology of fish. This thesis investigated how Fundulus killifish cope with daily cycles between hypoxia and normoxia (intermittent hypoxia) by modifying oxygen transport, metabolism, and oxidative stress defense systems. I found that killifish rely on a unique and effective physiological strategy to cope with intermittent hypoxia, and that this strategy is distinct from how they respond to a single bout of hypoxia (followed by normoxia) and to a constant pattern of only hypoxia. This is the most extensive investigation to date on how fish respond to the challenges of intermittent hypoxia, an understudied but ecologically important type of aquatic hypoxia. hypoxia tolerance respiration metabolism haematology gill morphology muscle histology respirometry metabolic depression glycolysis excess post-hypoxic oxygen consumption reoxygenation reactive oxygen species oxidative stress antioxidants diel cycles diurnal hypoxia hypoxia resistance evolutionary physiology phylogenetically independent contrasts aerobic scope fish hypoxia physiology zoology enzyme activity metabolites critical oxygen tension loss of equilibrium
137	Transport of nitrogen oxides and nitric acid pollutants over South Africa and air pollution in Cape Town Ojumu, Adefolake Mayokun 24 October 2013 (has links) The deteriorating air quality in Cape Town (CT) is a threat to the social and economic development of the city. Although previous studies have shown that most of the pollutants are emitted in the city, it is not clear how the transport of pollutants from neighbouring cities may contribute to the pollution. This thesis studies the transport of atmospheric nitrogen oxides (NOx) and nitric acid (HNO3) pollutants over South Africa and examines the role of pollutant transport from the Mpumalanga Highveld on pollution in CT. The study analysed observation data (2001 - 2008) from the CT air quality network and from regional climate model simulation (2001 - 2004) over South Africa. The model simulations account for the influences of complex topography, atmospheric conditions, and atmospheric chemistry on transport of the pollutants over South Africa. Flux budget analysis was used to examine whether the city is a net source or sink for NOx and HNO3. The results show that north-easterly flow transports pollutants (NOx and HNO3) at low level (i.e., surface to 850 hPa) from the Mpumalanga Highveld towards CT. In April, a tongue of high concentration of HNO3 extends from the Mpumalanga Highveld to CT, along the southern coast. The flux budget analysis shows that CT can be a net sink for NOx and HNO3 during extreme pollution events. The study infers that, apart from the local emission of the pollutants in CT, the accumulation of pollutants transported from other areas may contribute to pollution in the city. / Environmental Sciences / M. Sc. (Environmental Science) Air pollution Atmospheric pollution Flux budget analysis Extreme pollution events Pollutants transport Pollutants concentration Atmospheric-chemistry model Eulerian pollution model RegCM Diurnal variation 363.7392709687355 Nitric acid -- South Africa -- Cape Town
138	El mito de la Quintrala : Estructuras simbólicas en dos novelas de Gustavo Frías / The myth of La Quintrala : The symbolic structures in two novels by Gustavo Frías Belmar Shagulian, Jasmin January 2017 (has links) The purpose of this comparative study is to analyse La Quintrala’s myth as a symbolic discourse, thereby filling a gap in the previous studies about La Quintrala. The theoretical and methodological framework of this analysis consists of a hermeneutical approach based on the method of figurative structuralism: mythocriticism. This is a dual classification method of symbols: Diurnal and Nocturnal Orders that expose the symbolic structures formed by symbols and archetypes found in mythemes in a compilation of corpora. The first one is Gustavo Frías’ novels Tres Nombres para Catalina: Catrala (2008) and Tres nombres para Catalina: la doña de Campofrío (2008); the second is a historic essay (hypotext), Benjamín Vicuña Mackenna’s Los Lisperguer y la Quintrala (1944), and four novels: Magdalena Petit’s (2009) La Quintrala, Mercedes Valdivieso’s (1991) Maldita yo entre las Mujeres, Virginia Vidal’s (2002) Oro, veneno y puñal, and Gustavo Frías’ El Inquisidor (2008). Mythocriticism is employed in the analysis to show what the mythical structure of the hero’s journey (Separation, Initiation, Return) reveal. Such journey is combined structurally with the Mother archetype (White, Red and Black Goddess), the intrinsic archetype of La Quintrala’s myth. The heroic structure unveils its own mythemes, La Quintrala’s and the first corpus’s mytheme through the diachronic and synchronic flow of the hero’s journey. This method permits to identify and compare the progression of the symbolic structures. The analysis demonstrates a transformation of the symbolic structures between both corpora. This survey reveals that Vicuña Mackenna and Petit, and partially Vidal and El Inquisidor, exhibit an inclination to the diurnal symbols that strengthen, through a heterodiegetic narrator, the representations of the witch-femme fatale, counteractive attributes of the Red and Black Goddesses in the myth. Valdivieso, on the other hand, shows a propensity to the nocturnal symbols of inversion and intimacy that emphasize the Red Goddess’ features, though the novel also exposes La Quintrala as a witch-femme fatale. This exposure occurs through the use of both an autodiegetic narrator –La Quintrala– and a heterodiegetic one –the hypotext embodied in the popular voice– that appear to contrast each other. Finally, in Tres Nombres para Catalina, La Quintrala as the autodiegetic narrator dominates the whole story. She personifies the Great Goddess archetype who bestows her new positive attributes during the adventure. This novel assumes primordially the nocturnal symbolism incarnated by both the mystical and the synthetical structures and relegates the diurnal discourse of the hypotext to a secondary position in the narrative. Nonetheless, Tres Nombres para Catalina’s narrative still relies on the hypotext to reproduce and reconstruct all the mythemes in the myth of La Quintrala. Conclusively, the results of this analysis indicate that the identification of all the mythemes supports the hypothesis of a transformation in the symbolic structures which characterize La Quintrala in both corpora. This reveals the embodiment of Tres Nombres para Catalina’s own mytheme, consisting of a vindication and a recognition to her indigenous heritage, and the acceptance of her mestizaje. As a consequence, Tres nombres para Catalina, in comparison to the second corpus, diverges and expands the symbolic structures, but still shows a continuity of the myth. Quintrala myth Durand Campbell symbol symbolical structure mytheme imaginary Frías Valdivieso Vidal Vicuña Mackenna The Great Goddess Diurnal Order Nocturnal Order figurative structuralism Quintrala myt Durand Campbell symbol simbolisk struktur mytem imaginära Frías Valdivieso Vidal Vicuña Mackenna Stora Moder Dagens ordning Nattens ordning figurativ strukturalism Quintrala mito Durand Campbell símbolo estructura simbólica mitema imaginario Frías Valdivieso Petit Vidal Vicuña Mackenna Gran Diosa Régimen diurno Régimen nocturno estructuralismo figurativo Specific Literatures Litteraturstudier
139	Transport of nitrogen oxides and nitric acid pollutants over South Africa and air pollution in Cape Town Ojumu, Adefolake Mayokun 09 1900 (has links) The deteriorating air quality in Cape Town (CT) is a threat to the social and economic development of the city. Although previous studies have shown that most of the pollutants are emitted in the city, it is not clear how the transport of pollutants from neighbouring cities may contribute to the pollution. This thesis studies the transport of atmospheric nitrogen oxides (NOx) and nitric acid (HNO3) pollutants over South Africa and examines the role of pollutant transport from the Mpumalanga Highveld on pollution in CT. The study analysed observation data (2001 - 2008) from the CT air quality network and from regional climate model simulation (2001 - 2004) over South Africa. The model simulations account for the influences of complex topography, atmospheric conditions, and atmospheric chemistry on transport of the pollutants over South Africa. Flux budget analysis was used to examine whether the city is a net source or sink for NOx and HNO3. The results show that north-easterly flow transports pollutants (NOx and HNO3) at low level (i.e., surface to 850 hPa) from the Mpumalanga Highveld towards CT. In April, a tongue of high concentration of HNO3 extends from the Mpumalanga Highveld to CT, along the southern coast. The flux budget analysis shows that CT can be a net sink for NOx and HNO3 during extreme pollution events. The study infers that, apart from the local emission of the pollutants in CT, the accumulation of pollutants transported from other areas may contribute to pollution in the city. / Environmental Sciences / M. Sc. (Environmental Science) Air pollution Atmospheric pollution Flux budget analysis Extreme pollution events Pollutants transport Pollutants concentration Atmospheric-chemistry model Eulerian pollution model RegCM Diurnal variation 363.7392709687355 Nitric acid -- South Africa -- Cape Town
140	Birds, bats and arthropods in tropical agroforestry landscapes: Functional diversity, multitrophic interactions and crop yield Maas, Bea 20 November 2013 (has links) No description available. 630 birds bats arthropods multitrophic interactions agroforestry tropical landscape forest margin landscape functional diversity crop yield exclosure experiments experimental exclusion arthropod suppression avian predation ecosystem services mist netting point counts artificial plasticine caterpillar dummy experiment biological control monitoring mapping Lemon-bellied White-eye Grosbeak Starling Zosterops chloris Scissiostrum dubium Theobroma cacao cacao agroforestry cacao diseases cacao harvest cacao pests flying vertebrates aerial insectivores volant vertebrates logging breeding colony flower herbivory mesopredator release predatory insects ants spiders aphids Lepidoptera Coleoptera Lepidopteran larvae sustainable agriculture sustainable agroforestry management implications management recommendations applied managament extensive land use management landscape management conservation biodiversity-friendly dbh distance to forest forest proximity habitat conversion herbivory Indonesia insectivorous bats insectivorous birds invertebrates Central Sulawesi Napu valley leaf gleaning leaf herbivory pests insects phytophagous insects plant productivity remnant forest trees shade tree managament South-east Asia Paleotropics tropical landscape tree height landscape gradient local shade management Cacao Pod Borer Cherelle Wilt fruit abortion Helopeltis sulawesi deforestation habitat fragmentation land use intensification forest margin species critical decline predation experiment species-specific functions Southeast Asia biodiversity conservation mesopredators food security human welfare human well-being poverty alleviation poverty reduction smallholder cacao smallholder plantation cacao farmers sustainable cacao management landscape perspective landscape scale large scale field experiment long term field experiment human wellbeing economic importance economic value valuation ecosystem services landscape matrix yield quality yield quantity fruit productivity species identity species diversity species richness ecosystem functioning pesticide use chemical compounds complex food web tritrophic interactions wildlife-friendly rural livelihoods endangered bird species endangered bat species endemic endemic birds endemic bats beneficial impact IUCN Lore Lindu National Park bioindicator indicator species forest margin agricultural habitat agroforestry systems population density predation activity species activity cacao flower cacao pod Orthoptera linear mixed effect models Tukey Post Hoc Test AICc model selection generalized least squares restricted maximum likelihood model simplification species richness estimator species accumulation linear mixed-effects models Likelihood Ratio Test Maximum Likelihood nocturnal insects diurnal arthropods nocturnal arthropods diurnal insects landscape context Land- und Forstwirtschaft (PPN621302791)

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