Dissertations / Theses on the topic 'Aragonite'
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Beckett, David. "Aragonite in Jurassic ooids : distribution and significance." Thesis, University of Reading, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306458.
Full textCroley, Allison L. "THE ARAGONITE TO CALCITE TRANSFORMATION: A LABORATORY STUDY." Oxford, Ohio : Miami University, 2002. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=miami1038431567.
Full textTitle from first page of PDF document. Document formatted into pages; contains vi, 78 p. : ill. Includes bibliographical references (p. 37-40).
Gérard, Yves. "Étude expérimentale des interactions entre déformation et transformation de phase : exemple de la transition calcite-aragonite /." Rennes : Centre armoricain d'étude structurale des socles, 1987. http://catalogue.bnf.fr/ark:/12148/cb349781275.
Full textBrown, Sarah Jane. "Controls on the trace metal chemistry of foraminiferal calcite and aragonite." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627090.
Full textGérard, Yves. "Etude experimentale des interactions entre deformation et transformation de phase : exemple de la transition calcite-aragonite." Rennes 1, 1987. http://www.theses.fr/1987REN10146.
Full textZadi, Daza Louis. "Mécanismes physico-chimiques impliqués dans la formation et l’évolution à l’abandon d’un matériau sédimentaire innovant généré en milieu marin par polarisation cathodique." Electronic Thesis or Diss., La Rochelle, 2022. http://www.theses.fr/2022LAROS028.
Full textThis PhD work focused on the study of a material (Geocorail) formed by cathodic polarization applied in a marine sedimentary environment and used for the reinforcement of coastal structures in the fight against coastline recession. The objective of this study is to provide answers relative to the influence of the process parameters on the physico-chemical properties of this material as well as the evolution of the material under abandonment conditions, i.e. when the polarization is stopped. This was achieved through an experimental approach coupled with numerical models. This work was carried out on a laboratory material and its diffusion anisotropy within this material, the thickness, porosity and density of which are essentially controlled by the applied current density and the polarization time. These two parameters promote the formation of a binder, consisting of brucite (Mg(OH)2) and aragonite (CaCO3), which serves to agglomerate the sediments in place. The geometry of this sediment is also a key factor in optimizing the properties of this material. With regard to its chemical stability in the absence of polarization, experimental analyses and numerical models revealed that brucite substitutes for aragonite with a relatively low mass yield, probably linked to the high diffusivity of the studied materials. The small variation in porosity and density (less than 5% in 18 months) however ensures the stability of the Geocorail, whose properties could even improve with time. Finally, numerical models of the growth and evolution in abandon condition were developed. Some ways of improvement were also proposed for a better prediction of these properties, and even for the mechanical characterization using numerical methods
Rowling, Jill. "Cave Aragonites of New South Wales." Thesis, The University of Sydney, 2004. http://hdl.handle.net/2123/694.
Full textRowling, Jill. "Cave Aragonites of New South Wales." University of Sydney. Geosciences, 2004. http://hdl.handle.net/2123/694.
Full textMiller, Caroline E. "Environmental influences on synthetic and biogenic calcium carbonate in aragonite-calcite sea conditions." Thesis, University of Glasgow, 2018. http://theses.gla.ac.uk/8665/.
Full textThis research allows comparison of how non-biogenic and biogenic CaCO3 formation is influenced by seawater chemistry and environmental parameters to determine the dominant mineralogy. Increased temperature in both formations has shown to increase the impact of magnesium on calcite enabling the facilitation of aragonite. However, magnesium has influence on biogenic aragonite in extreme combined conditions of elevated temperature and pCO2. This work indicates that CaCO3 formation is complex and requires a multi-variable approach to understanding the mechanisms that facilitate the dominant mineralogy. By including variables such as temperature, this research suggests that aragonite-calcite seas conditions do not facilitate globally homogeneous switches in mineralogy, but the mineralogy is indeed influenced on latitudinal scales by other factors that influence the mechanisms involved.
Conci, Nicola [Verfasser], and Gert [Akademischer Betreuer] Wörheide. "Molecular biomineralization of octocoral skeletons: calcite versus aragonite / Nicola Conci ; Betreuer: Gert Wörheide." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1211957616/34.
Full textOffeddu, Francesco G. "Processes affecting the efficiency of limestone, aragonite and dolostone in passive treatments for AMD." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/323891.
Full textLas aguas que proceden de minas (en ingles acid mine drainage-AMD) contienen altas concentraciones de SO4 y metales contaminantes que pueden perdurar siglos en el medio ambiente. El objetivo de los tratamientos de AMD es retener los metales y neutralizar la acidez de las AMD. Uno de los sistemas de tratamiento usado, es el drenaje anóxico a través de caliza (clz) (en inglés anoxic limestone drainage, ALD) que necesita escaso mantenimiento y bajo presupuesto. La eficiencia de los ALD está limitada por la precipitación (ppt) de minerales secundarios (yeso e Me-hydroxidos) que causa el recubrimiento de los granos de clz (pasivación, pass) y la colmatación de los poros reduciendo la reactividad de la clz y su poder tampón. Esta tesis esta enfocada en los procesos que afectan a los minerales carbonatos usados en el ALD y en la pérdida de reactividad de la calcita (cal), aragonita (arag) y dolomita (dol) debido a la pass. Con este fin se llevaron a cabo tres tipos de experimentos (25 °C, 1 atm): de columna, batch e in situ con microscopio de fuerza atómica (AFM). Experimentos de columnas: Se inyectaron soluciones ácidas sintéticas (pH2) ricas en Fe (III) o Al con flujo constante de 6x10-4 o 1x10-3 L m-2 s-1 en columnas rellenadas con granos de cal, arag o dol. Las columnas han retenido los metales durante la disolución (diss) de los carbonatos, aumentado el pH e promoviendo la ppt (ppt) de oxihidróxidos de los metales. El Ca liberado durante la diss, junto con el sulfato, ha precipitado como yeso causando el recubrimiento de la superficie de los granos. El recubrimiento impide la diss de los carbonatos y limita la eficiencia de las columnas. Altas concentraciones de sulfato y pH más ácidos produjeron tiempos de pass más rápidos. Mediante micro-tomografía de rayos X (mCT) y micro-difracción de rayos X (mXRD), se mostró que el recubrimiento de los granos de carbonatos se debe a la ppt de yeso y que los oxihidróxidos precipitan entre los granos, la cual cosa favoreció la formación de flujos preferenciales, aislando regiones donde no se producen reacciones entre solución circulante y granos. El flujo preferencial se ha visto reducido cuando se han mezclado los carbonatos con esferas de vidrio. Los resultados experimentales se han modelado con el código CrunchFlow ajustando el valor de del área reactiva de la cal en el modelo con los datos experimentales, corroborando el proceso de pass en los experimentos. Se realizaron experimentos de tipo batch para estudiar la diss de cal, dol y arag (granulometria: 100-300 mm;1-2 mm, y 1.5 x 1.2 x 0.5 cm) y la ppt de yeso sobre la superficie de los carbonatos y a pH 2 (solución de H2SO4 equilibrada respecto al CaSO4¿2H2O). A lo largo de los experimentos se han distinguido tres fases: tiempo de inducción para la nucleación del yeso; fase de diss de los carbonatos con la simultánea ppt de yeso; equilibrio alcanzado entre la solución y el mineral carbonatado. Durante la diss de carbonatos, el pH subió de 2 a ~7, ralentizando la cinética de diss y la velocidad de ppt de yeso hasta llegar a cero una vez alcanzado el equilibrio con CaCO3. Además resultó que independientemente del sustrato la velocidad de ppt del yeso fue similar. Los experimentos in situ AFM se realizaron con soluciones de Na2SO4 y CaSO4 y pH entre 2-6 para estudiar el proceso acoplado de la diss de cal o dol con la ppt de yeso. La diss de los carbonatos tuvo lugar en las superficies de exfoliación (104). Se han observado distintas formas de diss (etch pits), con estructura típica romboédrica y el redondeo de los bordes de los etch pits conforme se aproximaban a condiciones de equilibrio con respecto a la cal. El yeso precipitado recubrió rápidamente la superficie de la cal, con morfología de flecha y ejes paralelos a las orientaciones cristalográficas de los etch pits de la cal. La ppt del yeso en el caso de la diss de dol fue más lento y parcial, lo que indica que la velocidad de diss controla la velocidad de las reacciones.
Les aigües que procedeixen de l'activitat minera, conegudes com aigües àcides de mina (en anglès acid mine drainage, AMD) contenen normalment altes concentracions de sulfat, ferro i altres metalls contaminants associats. Aquests contaminants poden perdurar en el medi ambient fins a segles després del cessament de l'activitat minera. Els principals objectius dels tractaments AMD són la retenció de metalls (precipitació dels metalls contaminants) i la neutralització de l'acidesa de les aigües. Un dels possibles sistemes de tractament passiu, i dels més utilitzats, és el drenatge anòxic amb calcària (en anglès, anoxic limestone drainage, ALD), o sistemes derivats (per exemple, la reducció i els sistemes de producció d'alcalinitat), que es caracteritzen pel poc manteniment requerit i el baix cost. No obstant, l'eficiència dels sistemes d'ALD està limitada per la precipitació de minerals secundaris que causa la passivació (recobriment) dels grans de calcària i l'obstrucció dels porus entre ells, reduint així la reactivitat de la calcària i, per tant, el poder tampó. La presència de sulfat aquós indueix la precipitació de guix, que contribueix en gran mesura a la passivació de la calcària i afecta l'eficiència dels sistemes de tractament. Aquesta Tesi té com a objectiu principal millorar els nostres coneixements sobre el funcionament de minerals carbonats utilitzats en ALD i la pèrdua de la reactivitat de la calcita, aragonita i dolomita a causa del recobriment dels grans o l'obstrucció dels porus entre grans. Amb aquesta finalitat, es s’han dut a terme tres tipus d'experiments: (1) experiments de columna, (2) de tipus batch i (3) experiments in situ amb AFM. (1) Els experiments de columnes emplenades amb grans de calcita, aragonita o dolomita (de diàmetre 1-2 mm) es van realitzar per estudiar el comportament dels sistemes de tractament passiu emprats en el drenatge àcid de mines (AMD). Es van injectar solucions àcides sintètiques (principalment a pH2, H2SO4) rica en ferro (Fe (III)) o alumini. Durant els experiments, el flux de la solució d'entrada es va mantenir constant a la velocitat de Darcy de 6x10-4 a 1x10-3 L m-2 s-1. Les columnes han eliminat eficientment el ferro i l’alumini aquosos mentre que la dissolució dels carbonats ha tamponat el pH de la solució (augment del pH i inducció de la precipitació d’oxihidróxids de Fe (III) - o d'Al). No obstant, el Ca alliberat en solució pels minerals carbonats, juntament amb el sulfat aquós, va induir la precipitació de guix, que és la principal causa de recobriment (passivació) a les superfícies dels grans. Aquest recobriment ha impedit conseqüentment la dissolució de calcita limitant l'eficiència de les columnes. Concentracions més altes del sulfat d'entrada i pH més àcids van originar temps de passivació més ràpids. La caracterització de l'estructura dels porus i de la composició química dels sòlids mitjanament la per micro-tomografia de raigs X (MCT) i micro-difracció de raigs X (mXRD), va mostrar que el recobriment dels grans de carbonats és degut a la precipitació de guix i que els oxihidróxids secundaris tendeixen a precipitar entre els grans. La precipitació de minerals secundaris va afavorir la formació de fluxos preferents, aïllant regions on no es produeixen reaccions entre la solució circulant i els grans. L'efecte de la formació del flux preferent s'ha reduït utilitzant un disseny diferent a les columnes (barrejant els grans de carbonats amb esferes de vidre inerts). Els resultats experimentals s'han modelitzat amb el codi de transport reactiu CrunchFlow. Per tal que les dades experimentals i les del model coincidissin s'ha ajustat al valor de l'àrea reactiva de la calcita en el model, consistentment amb el procés de passivació en els experiments. (2) Es van dur a terme experiments de tipus batch a 25 ° C, pressió atmosfèrica i pH 2 (solució de H2SO4 equilibrada respecte al CaSO4 • 2H2O) per estudiar les reaccions de dissolució de la calcita i aragonita acoblades a la precipitació de guix. Es van utilitzar tres tipus de mostra sòlida (pols (100-300 μm), grans (1-2 mm) i fragments (1.5 x 1.2 x 0.5 cm)) que van actuar com a substrats de mineral carbonat en què va créixer el guix. Al llarg dels experiments s'han distingit tres fases: temps d'inducció de la precipitació del guix, dissolució del substrat de mineral carbonat, juntament amb la precipitació de guix, i l'assoliment de l'equilibri de la solució respecte el mineral carbonat. El temps d'inducció va ser similar durant la dissolució de calcita i aragonita, ja que tots dos minerals dissolen amb la mateixa velocitat de dissolució. Durant la dissolució de minerals carbonats, el pH va pujar de 2 a aproximadament 7, alentint tant la velocitat de dissolució dels carbonats com la taxa de precipitació de guix per arribar a zero un cop assolit l'equilibri amb CaCO3 (calcita o aragonita) va ser aconseguit. La velocitat de precipitació del guix va ser similar independentment del substrat (calcita o aragonita), tot i la morfologia del mateix substrat. 3) Es van realitzar experiments in-situ amb el microscopi de força atòmica (AFM) per estudiar el procés global de la dissolució de calcita i dolomita i la precipitació de guix en solucions Na2SO4 i CaSO4 amb valors de pH entre 2 i 6 i temperatura ambient (23 ± 1 ° C). La dissolució dels minerals carbonats va tenir lloc a les superfícies de clivatge (104) usant solucions riques en sulfat i subsaturades respecte al guix. Es va observar la formació de forats de dissolució (etch pits) amb les típiques formes romboèdriques. També s’observa l'arrodoniment de les vores dels etch pits quan les solucions s’acostaven a a les vores l'equilibri respecte de la calcita. Les velocitats de dissolució de la calcita calculades a pH 4.8 i 5.6 va coincidir amb els valors de la literatura. En solucions prèviament equilibrades amb el guix, la precipitació de guix acoblada a la dissolució de calcita s’aconseguí amb temps d'inducció més curts. El guix precipitat va recobrir ràpidament la superfície de la calcita, amb morfologia de fletxa i eixos paral·lels a les orientacions cristal·logràfiques dels etch pits de la calcita. La precipitació de guix, juntament amb la dissolució de dolomita, va ser més lenta que la de calcita, la qual cosa indica que la velocitat de dissolució va ser el procés que controla la velocitat. El revestiment de guix ha cobert parcialment la superfície de la calcita durant l’experiment.
Al-Aasm, Ihsan Shakir. "Stabilization of aragonite to low-Mg calcite trace elements and stable isotopes in rudists." Thesis, University of Ottawa (Canada), 1985. http://hdl.handle.net/10393/4677.
Full textBrent, Kaylee. "An examination of trace element concentrations across calcite/aragonite transitions in a Madagascan stalagmite." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/114099.
Full textCataloged from PDF version of thesis.
Includes bibliographical references (pages 21-23).
Calcite and aragonite speleothems have been used for the past few decades to provide paleoclimate information, but in speleothems of mixed mineralogy the signal of mineral changes can complicate understanding of climate signals also present. This mineral signal must therefore be examined and controlled for. In this work, ICP-MS (inductively-coupled plasma mass spectrometry) analysis of trace element (strontium and magnesium) incorporation into calcium carbonate provides additional evidence for a shift in CaCO3 polymorphs identified via XRD (xray diffraction) analysis of speleothem AB-2 from Anjohibe Cave, Madgascar. The ICP-MS Sr/Ca data qualitatively supports the Sr/Ca data collected by the XRF core scanner, exhibiting a sharp decrease in value across the identified mineral transition. A corresponding increase in Mg/Ca revealed by the ICP-MS provides further evidence for a change from aragonite to calcite at this location. This mineralogical change occurred between 870-880 CE (+/- 13 years) is nearly concurrent with a shift in [delta]13C isotopes that was identified in previous work on this speleothem and attributed to an ecological shift in dominant photosynthetic pathways (Bums et al 2016). A second, control section was identified as pure calcite by XRD analysis, but revealed Mg/Ca and Sr/Ca ratios characteristic of mineralogical transitions, suggesting that there may have been layers of aragonite that have recrystallized to calcite since deposition.
by Kaylee Brent.
S.B.
Wang, Dongbo. "Calcification by amorphous carbonate precursors: Towards a new paradigm for sedimentary and skeletal mineralization." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77271.
Full textPh. D.
Knuth, Jordan Marie. "The Effects of Microorganism on Carbonate Precipitation in the Ten Mile Graben Cold Springs, Utah: A Mars Analog." OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2385.
Full textGerard, Y. "Etude expérimentale des interactions entre déformation et transformation de phase.Exemple de la transition calcite - aragonite." Phd thesis, Université Rennes 1, 1987. http://tel.archives-ouvertes.fr/tel-00648807.
Full textBernstein, Whitney Nicole. "Variations in coral reef net community calcification and aragonite saturation state on local and global scales." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/84915.
Full textCataloged from PDF version of thesis.
Includes bibliographical references.
Predicting the response of net community calcification (NCC) to ocean acidification OA and declining aragonite saturation state [Omega]a requires a thorough understanding of controls on NCC. The diurnal control of light and net community production (NCP) on NCC confounds the underlying control of [Omega]a on NCC and must be averaged out in order to predict the general response of NCC to OA. I did this by generating a general NCC-[Omega]a correlation based on data from 15 field and mesocosm studies around the globe. The general relationship agrees well with results from mesocosm experiments. This general relationship implies that NCC will transition from net calcification to net dissolution at a [Omega]a of 1.0 ± 0.6 and predicts that NCC will decline by 50% from 1880 to 2100, for a reef of any percent calcifier cover and short reef water residence time. NCC will also decline if percent calcifier cover declines, as evidenced by estimates of NCC in two Caribbean reefs having declined by an estimated 50-90% since 1880. The general NCC-([Omega]a relationship determined here, along with changes in percent calcifier cover, will be useful in predicting changes in NCC in response to OA and for refining models of reef water [Omega]a.
by Whitney Nicole Bernstein.
Ph.D.
Gérard, Yves. "Etude expérimentale des interactions entre déformation et transformation de phase exemple de la transition calcite "aragonite /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb376053770.
Full textJury, Christopher P. "Aragonite saturation state and seawater PH do not predict rates of calcification in a reef-building coral." View electronic thesis, 2008. http://dl.uncw.edu/etd/2008-3/r1/juryc/christopherjury.pdf.
Full textLloyd, Ryan Allen. "Remote Sensing of Whitings in the Bahamas." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4361.
Full textZanibellato, Alaric. "Synthèse et études physico-chimiques d’un agglomérat calcomagnésien formé sur acier en milieu marin : un éco-matériau pour la protection du littoral." Thesis, La Rochelle, 2016. http://www.theses.fr/2016LAROS005/document.
Full textA new method, based on an innovative adaptation of cathodic protection principle of metal structures in marine environment, is to promote the precipitation of a calcareous agglomerate several centimeters thick. In the presence of sand and shells, this cluster could stabilize coastal areas being eroded or improve anchorage of breakwater riprap. The objective of this work is to study and understand the reaction mechanisms allowing to create a voluminous calcareous deposit away from the cathode and to optimize deposition time as well as its mechanical properties. First, it was shown in this work that the electrolytic medium could affect the growth of the deposit, with a possible inhibition of formation of calcium carbonate fot the low potential. The influence of corrosion products in the cathodic protection mechanism was also highlighted through polarizations performed in NaCl, artificial and natural sea water. Second, one month test with impressed current were conducted from laboratory to natural site, in order to get closer of real conditions. Current density and hydrodynamic conditions are key factors closely bonded to each other, affecting the mass and composition of the Ca/Mg ratio. This work has also helped to highlight the influence of the polarization time on the composition, with stable growth kinetics but a composition’s evolution after 15, 30 and 60 days. This internal variation of the Ca/Mg ratio attributed to a process of « dissolution/precipitation » is pH dependent and the distribution of these elements within the deposit could play a major role in the evolution of the mechanical strength of deposit over time
Roy, Siddhartha. "Interplay of Water Chemistry and Entrained Particulates in Erosion Corrosion of Copper and Nonleaded Alloys in Potable Water Systems." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82668.
Full textPh. D.
Pavat, Céline. "Etude du processus de biominéralisation chez les mollusques à travers trois exemples : la réparation coquillière (Haliotis tuberculata), la formation des perles (Pinctada magnaritifera) et la composition de la matrice coquillière (Helix aspersa maxima)." Caen, 2012. http://www.theses.fr/2012CAEN2033.
Full textThe mechanisms underlying the formation of shells in molluscs, especially bivalves and gastropods, are the subject of a growing number of studies in recent years. These works had enabled to highlight the existence of an intra-specific morphological plasticity of calcification in several species of molluscs. In this thesis, we chose to approach this concept of plasticity of the biomineralization process through three specific cases: the shell repair in the marine gastropod Haliotis tuberculata, transplantation of a mineralizing tissue in the pearl oyster Pinctada margaritifera, and the composition of the shell of a land snail (Helix aspersa maxima). In H. Tuberculata and P. Margaritifera, the results emphasized the existence of a rearrangement, more or less important of mineralizing tissues following stress (shell lesion / transplant), ranging from a simple change in the rate of mineralization (repair), to an important structural change of the mineralizing tissue (transplant). On Helix aspersa maxima, the matrix components of the shell in this species have "atypical" characteristics: very weak interaction (or not) with CaCO3 in vitro. In addition, partial sequences of matrix proteins obtained in this work showed no homology with sequences in current databases. The drastic change of environment could be the cause of this disparity between the matrices of marine organisms and that of our model (Helix aspersa maxima)
Lipsitz, Brian Lewis. "A Comparison of the Relative Sediment Transport of Quartz and Aragonite Sand for Use as Beach Renourishment Materials in South Florida." NSUWorks, 1987. http://nsuworks.nova.edu/occ_stuetd/365.
Full textKrauss, Christopher. "Couches polycristallines orientées d'aragonite biomimétique, synthétisées par voie électrochimique." Caen, 2009. http://www.theses.fr/2009CAEN2034.
Full textCalcium carbonate can be found in many natural materials, such as coral and shells of various crustaceans and mollusks. The growth of its various polymorphs, aragonite, calcite and vaterite, in the presence of biological molecules, affect their organization in terms of crystalline microstructure and long range order (texture and ultrastructure). Electrodeposition was chosen in this work for its growth speed and a good control of instrumental parameters. We have selected the growth of aragonite, mimicking the texture of the nacre of Haliotis tuberculata tuberculata but with a less pronounced crystal orientation. A growth of oriented pseudo-hexagonal platelets, with a double-twinning and a relative orientation of approximately 60° to each other, seems to be close to the observations on natural nacres of different molluscs. A X-ray diffraction study of the deposits obtained in the presence of chitosan and organic molecules extracted from natural nacres shows their influence on the crystalline texture but also on the lattice of aragonite and on the carbonate groups. The aplanarity of carbonate groups shows the deformation induced by the molecules during the crystal growth. This study shows that a mineral-organic synthetic approach can give new insights on the process leading to the growth of natural biogenic crystals in terms of crystalline orientation, lattice distortion, structure and crystalline microstructure
Niekawa, Natsuki. "Role of eEpitaxy-mediated transformation in Ostwald's step rule." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/188499.
Full textDi, Matteo Berardo <1985>. "Aragonite-based scaffold for the treatment of knee osteochondral defects: results of a prospective multi-center trial at 2 years' follow-up." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9098/1/tesi%20dottorato%20di%20matteo.pdf.
Full textZeyen, Nina. "Etude de microbialites lacustres actuels du Mexique : traçage de l’activité biologique et des conditions environnementales de formation." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066710/document.
Full textThe processes leading to the formation of microbialites, which are organo-sedimentary rocks, are not well understood. The main goal of this thesis is to better understand the environmental conditions allowing the development of modern microbialites. Here we performed geochemical analyses of water solutions and mineralogical analyses of microbialites in 10 Mexican volcanic lakes. We found a large diversity of microbialites in terms of mineralogical composition, with occurrence of diverse carbonate phases as well as the frequent presence of authigenic magnesium silicate phases. From this study, we infer a minimum alkalinity value for the formation of lacustrine microbialites. Moreover, we observe a positive correlation between the alkalinity and the sodium content of the lakes. This may relate to variations in evaporation intensity and/or various degrees of weathering of the surrounding silicates. The study of Mg-silicates revealed that this phase is similar to kerolite, a poorly crystalline hydrated talc phase, and has a strong potential for the fossilization of microorganisms and organic matter. These silicates are sometimes associated with iron, the origin of which remains uncertain in these alkaline and oxidized environments. By the mineralogical study of several microbialites, we found several phases bearing iron: layered double hydroxides (hydrotalcites), Mg-silicates, oxy(hydroxi)des and sulfides. We propose more specifically that hydrotalcite could be the by-product of basalts weathering by groundwater. We propose more generally that hydrotalcite could be a precursor phase of Mg-silicates abundantly observed in modern microbialites
Oukda, Mustafa. "Evolution organogénétique et phylogénétique de l'organe stato-acoustique : ontogenèse, caractérisation des principaux types de cellules sensorielles, analyses cristallographiques et chimiques des otoconies chez Pleurodeles waltl (Amphibien Urodèle)." Nancy 1, 1999. http://www.theses.fr/1999NAN10265.
Full textGomez, Carlos E. "Ecological and physiological constraints of deep-sea corals in a changing environment." Diss., Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/535228.
Full textPh.D.
Deep-water or cold-water corals are abundant and highly diverse, greatly increase habitat heterogeneity and species richness, thereby forming one of the most significant ecosystems in the deep sea. Despite this remote location, they are not removed from the different anthropogenic disturbances that commonly impact their shallow-water counterparts. The global decrease in seawater pH due to increases in atmospheric CO2 are changing the chemical properties of the seawater, decreasing the concentration of carbonate ions that are important elements for different physiological and ecological processes. Predictive models forecast a shoaling of the carbonate saturation in the water column due to OA, and suggest that cold-water corals are at high risk, since large areas of suitable habitat will experience suboptimal conditions by the end of the century. The main objective of this study was to explore the fate of the deep-water coral community in time of environmental change. To better understand the impact of climate change this study focused in two of the most important elements of deep-sea coral habitat, the reef forming coral Lophelia pertusa and the octocoral community, particularly the gorgonian Callogorgia delta. By means of controlled experiments, I examined the effects of long- and short-term exposures to seawater simulating future scenarios of ocean acidification on calcification and feeding efficiency. Finally In order to understand how the environment influences the community assembly, and ultimately how species cope with particular ecological filters, I integrated different aspects of biology such functional diversity and ecology into a more evolutionary context in the face of changing environment. My results suggest that I) deep-water corals responds negatively to future OA by lowering the calcification rates, II) not all individuals respond in the same way to OA with high intra-specific variability providing a potential for adaptation in the long-term III) there is a disruption in the balance between accretion and dissolution that in the long term can shift from net accretion to net dissolution, and IV) there is an evolutionary implication for certain morphological features in the coral community that can give an advantage under stresfull conditions. Nevertheless, the suboptimal conditions that deep-water corals will experience by the end of the century could potentially threaten their persistence, with potentially negative consequences for the future stability of this already fragile ecosystem.
Temple University--Theses
Zhong, Shaojun. "An experimental investigation of "calcite and aragonite precipitation rates in seawater as a function of salinity" and its applications to some geological problems /." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64095.
Full textDe, Caro Francesca <1981>. "Trattamento delle lesioni osteocondrali del ginocchio con un innovativo scaffold di aragonite: risultati di uno studio prospettico a due anni di follow-up." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amsdottorato.unibo.it/9134/3/decaro_francesca_tesi.pdf.
Full textIntroduction The articular cartilage is a very complex tissue that does not repair on it's own. In these last years, different bioengineered scaffolds have been developed to repair the entire osteochondral lesion. The aim of this study is to evaluate the clinical and MRI results at short term follow-up of this innovative, aragonite based, acellular scaffold. Materials and methods Twelve patients have been prospectively enrolled after approval of the University of Antwerp ethical commitee. Patients were evaluated clinically and by MRI at 6-12-18 and 24 months. The non parametric test of Wilcoxon has been conducted for the analysis of clinical results. Results In 3 patients the lesion was located on the MFC, in 4 patients on the LFC and in 5 on the throclea. 9 patients were man, 3 females. Mean age was 31.4±8.0 years. All patients reported a significant increase of all clinical scores. KOOS went from 47.3±13.6 at baseline to 85.6±11.7 at last follow-up (p=0.005). An increase of the tegner score was also reported by all patients, from a basal score of 2.75±1.6 to 4.8±1.2 at last follow-up. The MRI showed a 96.4 % filling of the lesion at two years control. Conclusions The results at short term follow-up demonstrate that this technique is safe and reproducible. Results are promising with an increase of all clinical scores. Also MRI results are unique. A randomized controlled trial is now ongoing in USA, Europe and Italy.
Lunden, James J. "Ocean Acidification and the Cold-Water Coral Lophelia pertusa in the Gulf of Mexico." Diss., Temple University Libraries, 2013. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/230387.
Full textPh.D.
Ocean acidification is the reduction in seawater pH due to the absorption of anthropogenic carbon dioxide by the oceans. Reductions in seawater pH can inhibit the precipitation of aragonite, a calcium carbonate mineral used by marine calcifiers such as corals. Lophelia pertusa is a cold-water coral that forms large reef structures which enhance local biodiversity on the seafloor, and is found commonly from 300-600 meters on hard substrata in the Gulf of Mexico. The present study sought to investigate the potential impacts of ocean acidification on L. pertusa in the Gulf of Mexico through combined field and laboratory analyses. A field component characterized the carbonate chemistry of L. pertusa habitats in the Gulf of Mexico, an important step in establishing a baseline from which future changes in seawater pH can be measured, in addition to collecting in situ data for the design and execution of perturbation experiments in the laboratory. A series of recirculating aquaria were designed and constructed for the present study, and support the maintenance and experimentation of live L. pertusa in the laboratory. Finally, experiments testing L. pertusa's mortality and growth responses to ocean acidification were conducted in the laboratory, which identified thresholds for calcification and a range of sensitivities to ocean acidification by individual genotype. The results of this study permit the monitoring of ongoing ocean acidification in the deep Gulf of Mexico, and show that ocean acidfication's impacts may not be consistent across individuals within populations of L. pertusa.
Temple University--Theses
El, Fadl Hassan. "Détermination d'éléments atomiques sous forme de traces dans un biomatériau par radioactivation neutronique et analyse de la température de transition de phase aragonite-calcite." Clermont-Ferrand 2, 1990. http://www.theses.fr/1990CLF21282.
Full textTunusoğlu, Özge Shahwan Talal. "Kinetic Morphological, and Compositional Characterization of The Uptake of Aqueous Ba2+, Mn2+, AND Cd2+ Ions By Calcite And Aragonite Over A Wide Range of Concentration/." [s.l.]: [s.n.], 2007. http://library.iyte.edu.tr/tezler/master/kimya/T000657.pdf.
Full textMahmoudi, Mounir. "Stratigraphie, sédimentologie et diagénese des dépôts tyrrhéniens du Sahel tunisien (Tunisie orientale)." Paris 11, 1986. http://www.theses.fr/1986PA112130.
Full textOuhenia, Salim. "Simulation des diagrammes de diffraction par la méthode combinée : application aux systèmes CaCO3." Caen, 2008. http://www.theses.fr/2008CAEN2080.
Full textThe tremendous development of powder diffraction techniques achieved over the last ten years even operational on strongly textured samples within good resolutions, together with the fascinating development of individual calculating capabilities, make it possible to access precise information in reasonably short times. In this work, we apply the combined analysis based on the Rietveld method to study samples of natural calcium carbonates from two living species of molluscan shells and of synthetic CaCO3 in order to understand the influence of the different parameters in the growth and shape of the crystallites of the different polymorphs of CaCO3. In natural species we clearly put into evidence the existence of distortions of crystalline cells due to the presence of the intra- and extra-crystalline macromolecules, in opposition with similar studies operated on powderised samples. In synthetic samples we studied, using a simple synthesis method and taking as a model the polyacrylic acid, the role of the soluble macromolecules in the growth of the CaCO3 polymorphs. The simulation of the anisotropic diffraction diagrams on both sample types allowed us to reach pertaining information within good precision (anisotropic sizes of the crystallites, structure, texture, volume fraction of the polymorphs
Zeyen, Nina. "Etude de microbialites lacustres actuels du Mexique : traçage de l’activité biologique et des conditions environnementales de formation." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066710.pdf.
Full textThe processes leading to the formation of microbialites, which are organo-sedimentary rocks, are not well understood. The main goal of this thesis is to better understand the environmental conditions allowing the development of modern microbialites. Here we performed geochemical analyses of water solutions and mineralogical analyses of microbialites in 10 Mexican volcanic lakes. We found a large diversity of microbialites in terms of mineralogical composition, with occurrence of diverse carbonate phases as well as the frequent presence of authigenic magnesium silicate phases. From this study, we infer a minimum alkalinity value for the formation of lacustrine microbialites. Moreover, we observe a positive correlation between the alkalinity and the sodium content of the lakes. This may relate to variations in evaporation intensity and/or various degrees of weathering of the surrounding silicates. The study of Mg-silicates revealed that this phase is similar to kerolite, a poorly crystalline hydrated talc phase, and has a strong potential for the fossilization of microorganisms and organic matter. These silicates are sometimes associated with iron, the origin of which remains uncertain in these alkaline and oxidized environments. By the mineralogical study of several microbialites, we found several phases bearing iron: layered double hydroxides (hydrotalcites), Mg-silicates, oxy(hydroxi)des and sulfides. We propose more specifically that hydrotalcite could be the by-product of basalts weathering by groundwater. We propose more generally that hydrotalcite could be a precursor phase of Mg-silicates abundantly observed in modern microbialites
Christopher, Krauss. "Couches polycristallines orientées d'aragonite biomimétique, synthétisées par voie électrochimique." Phd thesis, Université de Caen, 2009. http://tel.archives-ouvertes.fr/tel-00423427.
Full textBourrouilh-Le, Jan Françoise G. "Diagenese des carbonates de plates-formes, recifs et mangroves, en atlantique et pacifique. Controle de la diagenese par les variationsthermo-glacio-eustatiques d'emersion-submersion. Aragonite, calcite, dolomite, phosphate." Paris 6, 1990. http://www.theses.fr/1990PA066061.
Full textBoop, Liana Marie. "Characterization of the Depositional Environment of Phreatic Overgrowths on Speleothems in the Littoral Caves of Mallorca (Spain): a Physical, Geochemical, and Stable Isotopic Study." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5187.
Full textLongkaew, Khansinee. "Preparation of calcium carbonate particles for application in natural rubber composites." Electronic Thesis or Diss., Le Mans, 2024. https://cyberdoc-int.univ-lemans.fr/Theses/2024/2024LEMA1003.pdf.
Full textThis research aims to synthesize different types and shapes of calcium carbonate (CaCO3) particles at a submicrometric and nanoscale, and investigate their applications as reinforcing fillers for natural rubber (NR) composites. The study was therefore divided into two parts. Firstly, the preparation procedure of CaCO3 particles was based on the solution precipitation method between carbonate ions and calcium ions. The second part focused on investigating the mechanical properties of NR/CaCO3 composites. The first part started with the precipitation of (NH4)2CO3 and CaCl2 dissolved in 50% by weight of sucrose as the aqueous medium. This condition resulted in spherical CaCO3 with particle size of 0.42±0.14 µm with an aspect ratio of about one. When the precipitation reaction occurred in the presence of olive soap, the surface property of the CaCO3 was changed from hydrophilic (water contact angle of 28±2o) to superhydrophobic powders (water contact angle of 163±2o). The typical polymorphic phases of CaCO3 were characterized. The results revealed that both untreated and treated spherical CaCO3 were about 99% of the vaterite polymorph. In the precipitation process using Na2CO3 and CaCl2 aqueous solutions performed at 80±1C, bundle-liked CaCO3 was obtained with an aspect ratio in the range of 8–9. The superhydrophobic bundle-liked CaCO3 was also successfully synthesized by soap treatment. The water contact angle of untreated and treated bundle-liked are 29±2o, and 167±2o, respectively. Furthermore, the spherical CaCO3 dispersed in water at 80C resulted in the fiber-shaped CaCO3 nanoparticles which were achieved via the polymorph transformation from spherical vaterite to long nano-wired aragonite with the highest aspect ratio of 156.9. The untreated fiber CaCO3 was hydrophilic with a water contact angle of 31±1o, while the treated fiber CaCO3 with soap resulted in 165±5o of water contact angle, hence it was superhydrophobic similar to other synthesized CaCO3 polymorphs. The XRD revealed that the untreated and treated bundle-liked and fiber-shaped CaCO3 contained the majority of aragonite followed by vaterite and calcite polymorphs. The second part was carried out to incorporate the prepared CaCO3 (0,5,10,20,40,60 phr) in NR latex. It was found that the CaCO3 polymorphs were stable in the NR latex medium. The mechanical properties of NR/CaCO3 included tensile strength, elongation at break, tear strength, and hardness Shore A. It was found that the tensile strength of NR/CaCO3 composites increased when CaCO3 loading was increased. The tensile strength of NR improved from 22.68±2.22 MPa of neat NR up to 23.94±0.97 MPa when untreated spherical CaCO3 powders (20 phr) were added, and to 25.28±0.80 MPa of treated spherical CaCO3 (20 phr) filled NR. The maximum tensile strength of NR/untreated bundle-liked CaCO3 was 30.59±3.50 MPa at 40 phr of loading while 31.51±1.02 MPa of NR/treated bundle-liked CaCO3 at filler loading 20 phr was obtained. The treated CaCO3-filled NR vulcanizates gave higher tensile strength than the untreated ones. This was caused by better compatibility of filler dispersion between the hydrophobicity of treated CaCO3 and hydrophobic property of NR. As a result, it was found that the NR filled with untreated fiber CaCO3 particle provided the highest tensile strength of 31.66±1.80 MPa at 10 phr of filler loading, over other types of CaCO3. The nanoparticle, large surface area, and high aspect ratio of fiber/ long nano wired of CaCO3 enhanced the interfacial adhesion between CaCO3 and NR matrix which could transfer stress from rubber to filler effectively during stretching. This resulted in the reinforcing efficacy of the fiber CaCO3. In summaroze, the prepared CaCO3 powders have the potential to broaden their application not only as diluents or additives but also as reinforcing agents
TOGHRAI-SABRAS, LADIN. "Etude par spectroscpie raman et par fluorescence des sulfates et carbonates de sr, ba, et pb, de structure barytine, et aragonite et de leurs solutions solides : effet electronique du plomb." Paris 6, 1992. http://www.theses.fr/1992PA066601.
Full textMadon, Michel. "Cellules à enclumes de diamant et microscopie électronique en transmission : étude expérimentale des transformations de phase du manteau terrestre." Paris 6, 1986. http://www.theses.fr/1986PA066123.
Full textEwen, Sarah Maree. "Diagenetic evolution of some modern and ancient cold seep-carbonates from East Coast Basin, New Zealand." The University of Waikato, 2009. http://hdl.handle.net/10289/2788.
Full textYu, Dongmei [Verfasser], Jörg [Gutachter] Renner, and Ralf [Gutachter] Dohmen. "Quantitative analyses and modelling of the microstructures associated with the thermally activated aragonite-calcite transformation in single crystals, bivalve shells, and corals / Dongmei Yu ; Gutachter: Jörg Renner, Ralf Dohmen ; Fakultät für Geowissenschaften." Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1223176037/34.
Full textStella, Sofia. "Analysis of the Variability of Carbonate System Parameters in the North-East Atlantic." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Find full textMartens, Wayde Neil. "The vibrational spectroscopy of minerals." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15940/1/Wayde_Martens_Thesis.pdf.
Full textMartens, Wayde Neil. "The vibrational spectroscopy of minerals." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15940/.
Full textXaza, Abongile. "Investigating hydrogeochemical processes of groundwater, Heuningnes Catchment, South Africa." University of the Western Cape, 2020. http://hdl.handle.net/11394/7961.
Full textThis study was conducted to investigate hydrogeochemical processes controlling the evolution of groundwater chemistry and their influence on water quality in the Heuningnes Catchment. The role or influence of hydrogeochemical processes in groundwater quality in aquifer systems remains poorly understood. One of the ways of improving such understanding is to employ different techniques to explore key processes that govern groundwater quality in aquifer systems. Therefore, the present study investigated hydrogeochemical processes of groundwater resources and identified key processes that explained its quality from a spatiotemporal perspective. The quantitative approach that provides the ability to assess relationships between variables both spatially and temporally was applied. Groundwater sampling was done on four occasions during July 2017, October 2017, March 2018, and July 2018. Identification of hydrogeochemical processes controlling the evolution of groundwater chemistry and quality was done using various complementary tools. These tools included classification of the main water types, evaluation of water-rock interaction by means of stoichiometry analysis and bivariate correlation plots, inverse geochemical modelling, and statistical analysis (hierarchical cluster analysis and factor analysis). Physical parameters were measured in situ, while water samples were collected from boreholes, piezometers, springs, and artesian boreholes for laboratory analysis for major ions analysis. Descriptive and bivariate statistical methods were used to summarise and evaluate the strength of the relationship between variables, while multivariate statistical methods were applied to group similar samples based on their chemical compositions. Tri linear Piper diagrams were generated to characterize water type based on double normalizing the proportions of cations and anions, while correlation and stoichiometric analysis were applied to identify hydrogeochemical processes influencing groundwater chemistry. The results generated from the trilinear Piper diagrams confirmed the dominance of sodium and chloride ions in waters of the Heuningnes Catchment. Groundwater of a Na/Cl type is typical for a coastal aquifer characterised by saline, deep ancient groundwater. The lower parts of the Catchment were characterised by saline groundwater. The results indicated that shallow groundwater samples within the study area were more mineralised as compared to deep groundwater with EC values ranging between 20.8 and 2990 mS/m, with waters within the Table Mountain Group region (TMG), recording the lowest values. Deep groundwater for boreholes and artesian boreholes located upstream in the Catchment was fresh and yielded some of the lowest EC values recorded with an EC value below 50 mS/m. Generally, EC values increased from the upper TMG region of the Catchment towards the Bokkeveld shale region downstream and were highest during the dry season of 2018. The results indicated strong geological influences on water chemistry. Bivariate correlation and stoichiometric analysis identified cation exchange, adsorption, evaporation, weathering of carbonates, sulphates and silicate minerals as processes influencing the chemistry of groundwater in the Heuningnes Catchment. The Saturation Index (SI) results showed a change of calcite, dolomite, aragonite, gypsum, anhydrite, halite, melantinterite, siderite and sylvite from being undersaturated to oversaturated at some areas for the different seasons along the flow path. The mass-balance modelling results indicated that ion exchange and reverse ion exchange processes were more dominant at low elevations along the same flow path during the dry periods. However, at high elevations along the flow path, silicate weathering was the dominant process taking place. The findings of this study demonstrated the influence of hydrogeochemical processes in changing the water chemistry along the flow paths. In conclusion, the study showed the value of utilising various assessment tools as complementary techniques to improve the understanding about hydrogeochemical processes, and its influence on evolution of groundwater chemistry and quality. Based on the findings of the study the following recommendations were made for future studies; the sample points or sample boreholes in the study Catchment should be increased; and to have more sampling trips to enable better comparison between the possible processes