Academic literature on the topic 'Opalina'

The swimming behaviour and photoresponses of the iridescent epipelagic copepods, Sapphirina gastrica and S. opalina were investigated in the laboratory. In continuous dark conditions, both species showed no significant diel variation in their swimming activities. When stimulated with light, they exhibited spiral-swimming in which the males showed a significantly higher speed and frequency of turning than the females. Both sexes of S. gastrica and S. opalina showed positive phototaxis at intensities higher than 0·05×1014 quanta cm−2 s−1 for light sources of 430 nm and 580 nm. Sapphirina gastrica showed increased locomotion over a broad range of wavelengths from 430 nm to 580 nm, while S. opalina showed a gradual increase of activity with decreasing wavelength, with the highest value at 430 nm. The photoresponses of these two species suggest that light conditions play an important role in their daytime ascent and in determining the depth distributions that were observed in our previous study. It is suggested that the iridescence and fast spiral-swimming of males, and the species-specific photoresponses of both sexes constitute a putative mate recognition system in the open ocean.

The morphology and cytology of two new opalinid species were studied using silver impregnation and fixation, which preserves the microfibrils. Both species, commensal on Acanthixalus spinosus, are host-specific. Light microscopy showed the existence of a posterior secant system in Opalina proteus n.sp. and its absence in Cepedea couillardi n.sp. (in agreement with the differences presently recognised between the two genera). At the ultrastructural level, however, both species present a posterior fibrillar zone that seems to be homologous with the secant system. This apparent contradiction may be explained by the fact that the secant system is visible under light microscopy only in O. proteus because its fibrillar zone is more developed than in C. couillardi. The life cycle of C. couillardi spans stages from the tadpole to the adult; in contrast, O. proteus completes its cycle before metamorphosis of the host.

Tulista Rafinesque (1840: 137) is the smallest of the three haworthioid genera recognised in the Asphodelaceae subfam. Alooideae, and widely considered to include four, or five, species [depending on whether T. opalina (Hayashi 2001: 17) Breuer (2016: 7) is accepted] (Smith et al. 2017).

A new species, Metallolophia taleensis, sp. nov., is described and illustrated from Tale Wildlife Sanctuary, Lower Subansiri District, Arunachal Pradesh, India, based on male specimens. A second species, Metallolophia opalina (Warren, 1893), is recorded from India after more than a century, extending its range eastwards into Arunachal Pradesh, India.

Spectral reflectivity and transmission of the iridescent cuticle of six species of male Sapphirina (Poecilostomatoida: Copepoda) were measured by microspectrophotometry. Sapphirina angusta and S. opalina showed two spectral peaks of reflection, one at about 420 nm and the other at wavelengths longer than 750 nm. Sapphirina auronitens and S. gastrica had dominant peaks at wavelengths longer than 500 nm. Sapphirina ovatolanceolata had peaks between 430 and 600 nm, while S. metallina had various peaks along a wide range of wavelengths. The peaks at the longer wavelength in S. angusta and S. opalina may be related to the red pigments in the subcuticular layer of the species, or a result of a second-order effect of the multilayer system. The spectra of transmitted light were complementary to those of reflected light, indicating that the iridescence is caused by the interference of light by the integumental multilayer structure. The present results are also consistent with the hypothesis that the iridescence has a role in increasing the contrast of males against the ambient light conditions in the daytime distributional depth of the species.

La sûreté des installations de stockage profond des déchets radioactifs repose sur l’évaluation des propriétés de confinement de la barrière géologique et des processus qui y régissent le transport des radionucléides. La thèse est menée dans le cadre de l’expérience Deep Borehole du projet Mont Terri. Elle vise à renforcer l’évaluation de l’importance relative des phénomènes de transfert convectifs et diffusifs au sein de l’Argile à Opalines (OPA) et à apporter des éclaircissements concernant l’impact des phénomènes transitoires chimique et hydraulique sur ces transferts et la génération d’anomalies de pression. Un premier volet expérimental a permis d’acquérir les paramètres de transport advectifs, diffusifs, et les forces motrices associées, nécessaires à l’estimation des flux d’eau et de solutés entre l’OPA et les aquifères adjacents. Les données de température et de pression révèlent un gradient géothermique de 8.5°C/100 m et un excès de charge d’au moins 60 m. L’inversion du profil de chlorure par méthode Bayésienne de type Monte Carlo Markov Chain valide l’évolution paléohydrogéologique du site proposé dans la littérature en considérant un transport diffusif pur à travers la formation. La contribution des phénomènes de transport osmotique a été déterminée en interprétant le profil de pression à l’aide de simulations transitoires considérant l’évolution temporelle de la chlorinité et de la pression au cours du scénario géologique et de simulations en pseudo régime permanent. Ce profil est reproduit en évaluant le flux advectif couplé incluant l’advection de Darcy, la chemo-osmose et la thermo-osmose, avec une contribution majeure de ce dernier processus
The safety of radioactive waste disposal facilities in deep geological formation depends on the evaluation of the rock confining properties and the processes governing radionuclides transfer. The thesis is conducted in the framework of Deep Borehole experiment of the Mont Terri project. The purpose of this research is to build confidence with regard to understanding relative importance of diffusive and convective phenomena withine the Opalinus Clay (OPA) and to identify the impact of a hydraulic and chemical transient behaviour on the transfers of fluid and solutes, and anomalous pressures generation.A first experimental stage enabled to acquire the advective and diffusive transport parameters, and the associated driving forces, necessary to the evaluation of fluid and solute fluxes between the OPA and its adjacent aquifers. Temperature and pressure measurements revealed a geothermal gradient of 8.5 °C/100 m and an excess of hydraulic head of at least 60 m.The chloride profile inversion by a Bayesian method with a Monte Carlo Markov Chain algorithm validates the paleohydrological evolution proposed in the litterature, considering a pure diffusive transport through the argillaceous formation. The contribution of osmotic transport phenomena was assessed by interpreting the pressure profile, using transient simulations that takes into account the temporal evolution of chlorinity and pressure during the geological scenario, and pseudo steady-state simulations. This profile is reproduced by evaluating the coupled advective flux, including pure advection, chemo-osmosis and thermo-osmosis, with a major contribution of the latter process

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2004.
Includes bibliographical references (p. 209-213).
The sample disturbance problem for different geomaterials is reviewed in this thesis. A general discussion on the disturbance sources and complexities of the disturbance problem is followed by detailed reviews on disturbance mechanisms and effects in soil and rock. This investigation leads to the conclusions that the combination of theoretical and physical modeling is an effective way to study the disturbance problem. Following the discussion of sample disturbance in soil and rock, the main aspects of shale behavior and shale sample disturbance are introduced in order to evaluate the applicability of theoretical and physical modeling in shale. It is shown that the coupled chemical - thermal - poromechanical effects of shale behavior may be a major barrier to a successful application of these modeling methods and to a better handling of sample disturbance.
by Jianyong Pei.
S.M.

La plupart de la diversité biologique est en réalité microbienne. L'arbre phylogénétique des eucaryotes comprend plusieurs grands supergroupes monophylétiques, dont les Opisthokonta. Ce groupe comprend deux branches, les Holozoa, qui inclut les animaux, et les Holomycota, qui regroupe les champignons et leurs parents unicellulaires. Bien que les champignons multicellulaires soient bien connus, nos connaissances sur la diversité des champignons unicellulaires et de leurs parents phylogénétiques restent limitées. Cette fraction unicellulaire comprend plusieurs lignées zoosporiques (par exemple chytrids) au sein des champignons, mais aussi une variété de lignées liées aux champignons classiques : les nucleariids, les rozellids, les aphelids et les microsporidies. Cependant, les relations phylogénétiques de ces lignées entre elles et avec les champignons restent à établir solidement. Les arbres phylogénétiques des gènes d'ARNr 18S environnementaux montrent une grande diversité d'Holomycota unicellulaires dans la plupart des écosystèmes terrestres. Cependant, le signal phylogénétique de ce gène est limité et ne permet pas de résoudre la plupart des relations phylogénétiques profondes. Au cours des dernières années, les techniques à haut débit ont permis de séquencer des centaines de nouveaux génomes et transcriptomes. Cela a permis de réaliser des études phylogénomiques multi-gènes, qui augmentent le signal disponible pour résoudre les relations évolutives. Néanmoins, la plupart de ces génomes correspondent à des espèces fongiques faciles à cultiver, souvent avec un intérêt particulier pour l'homme. Actuellement, les approches de type « omique » à partir des cellules uniques se révèlent comme potentiellement utiles pour étudier les eucaryotes unicellulaires non cultivés, en permettant de reconstruire des analyses phylogénétiques robustes d'une grande diversité environnementale à l'aide de données génomiques et transcriptomiques. Au cours de mon travail de doctorat, j'ai appliqué des approches de « cellule unique » pour obtenir des informations phylogénétiques à partir de lignées Holomycota divergentes, clarifier les relations phylogénétiques entre les champignons et ses proches parents et inférer l'évolution de leurs traits. Plus précisément, j'ai utilisé cette approche pour :1) Générer des données génomiques et transcriptomiques pour les nucleariids et mieux reconstruire les relations internes dans le clade et les caractères présents dans leur ancêtre. Nos résultats confirment que les genres de protistes à thèque Pompholyxophrys et Lithocolla sont en effet des nucleariids et branchent avec Nuclearia, Parvularia et Fonticula. La reconstruction d'une phylogénie robuste de ce groupe nous a permis d’inférer les traits (par exemple pas de flagelle) ancestraux du groupe. 2) Séquencer et analyser de manière comparative le génome de Metchnikovella incurvata, pour confirmer sa position relativement basale dans Microsporidia et déterminer les synapomorphies du clade. L'analyse phylogénomique du metchnikovellid Metchnikovella incurvata a confirmé que des Metchnikovellidae branchent à la base des Core-Microsporidia. Nous avons également confirmé que leur profil métabolique était plus similaire à celui des Core-microsporidia, tous deux ayant réduit de manière similaire leurs gènes / fonctions. 3) Générer des données génomiques pour Amoeboradix gromovi et Sanchytrium tribonematis, qui forment le clade des sanchytrides, une nouvelle lignée de champignons zoosporiques identifiée récemment, et résoudre leur position phylogénétique. L'étude des deux génomes de sanchytrids a clarifié leur placement au sein des Fungi en tant que nouvelle groupe frère des Blastocladiomycota. Des analyses génomiques comparatives montrent que leur métabolisme est réduit par rapport aux lignées apparentées. En particulier, le système flagellaire est fortement réduit par rapport à d'autres Holomycota, avec 4 événements indépendants de perte de flagelle dans le clade
Despite the astonishing diversity of plants, animals and macroscopic fungi, most eukaryotic diversity is actually microbial. The eukaryotic tree comprises several large monophyletic supergroups. One of these groups is the Opisthokonta, which encompasses two branches, Holozoa, including animals, and Holomycota, grouping Fungi and their unicellular relatives. While multicellular fungi are well known, knowledge on the diversity of unicellular Fungi and their phylogenetic relatives is still poor. This unicellular fraction includes several zoosporic lineages (e.g. Chytridiomycota and Blastocladiomycota) within Fungi, but also a variety of lineages related to the classical core Fungi: nucleariids, rozellids, aphelids and Microsporidia. However, the phylogenetic relationships of these lineages among them and with classical Fungi remain to be solidly established. Molecular phylogenetic trees of 18S rRNA genes retrieved from environmental studies have showed a wide diversity of unicellular holomycotans in almost all environments on Earth. However, the phylogenetic signal of this gene is limited and does not allow robustly resolving most deep phylogenetic relationships. During past years, high-throughput techniques have allowed sequencing hundreds of new genomes and transcriptomes. This has made possible to carry out multi-gene phylogenomic studies, which increase the available signal to resolve evolutionary relationships. Nevertheless, most sequenced genomes correspond to easy-to-culture fungal species, often with particular interest for humans (e.g. parasites, plant symbionts, yeast). Recently, single-cell omics has become a potential useful approach to study uncultured unicellular eukaryotes, making it possible to reconstruct robust phylogenetic analyses of a wide environmental diversity using genomic and transcriptomic data. During my PhD work, I have applied single-cell techniques to get phylogenetic information from divergent holomycotan lineages, clarify phylogenetic relationships among fungi and their close relatives and infer trait evolution. More specifically, I have used this approach to: 1) Generate genomic and transcriptomic data for nucleariids and better reconstruct inner relationships in the clade and the characters present in the nucleariid ancestor. Our results confirm that the cover-bearing unicellular genera Pompholyxophrys and Lithocolla are indeed nucleariids and branch together with Nuclearia, Parvularia and Fonticula. The reconstruction of a robust phylogeny for the group allowed us to infer the traits (e.g. no flagellum, glycocalyx, no cover) already present in their ancestor. 2) Sequence and comparatively analyze the genome of Metchnikovella incurvata, to confirm its relatively basal position within Microsporidia, and determine synapomorphies for the clade. Phylogenomic analysis of the metchnikovellid Metchnikovella incurvata confirmed that Metchnikovellidae branch at the base of Core-Microsporidia. We also confirmed their metabolic profile to be more similar to Core-microsporidia, being both similarly reduced in genes/functions. 3) Generate genomic data for Amoeboradix gromovi and Sanchytrium tribonematis, which form the newly described zoosporic fungal clade of sanchytrids, and resolve their phylogenetic position. The study of the two sanchytrid genomes clarified their placement within Fungi as a new clade sister to Blastocladiomycota. Comparative genomics showed that their metabolic composition was reduced in comparison with related lineages. This reduction was especially important in their flagellar toolkit when compared with other Holomycota, confirming 4 independent flagellum loss events in the clade

The storage of nuclear waste in deep geological formations is discussed worldwide as the main strategy for nuclear waste management. To ensure the confinement of the nuclear waste, a multiple barrier system which consists of engineered, geo-engineered, and geological barriers will be applied. Thereby, in Germany the definition of the isolating rock zone represents an important safety function indicator. Clay rock is internationally investigated as potential host rock for a repository and represents a part of the geological barrier. In the present work, the natural clay rock Opalinus Clay from the Mont Terri rock laboratory, Switzerland, was studied. In Germany, the direct disposal of the spent nuclear fuel without the reprocessing of the spent fuel is preferred. In case of water ingress, radionuclides can be released from the nuclear waste repository into its surroundings, namely the host rock of the repository. Humic acids, ubiquitous in nature, can be found associated with the inorganic components in natural clay rock (1.5×10–3 wt.% in Opalinus Clay). They can be released under certain conditions. Due to their variety of functional groups, humic acids are very strong complexing agents for metal ions. They have inherent redox abilities and a colloidal conformation in solution. Because of these characteristics, humic acids can affect the mobility of metal ions such as actinides. Furthermore, in the near-field of a repository elevated temperatures have to be considered due to the heat production resulting from the radioactive decay of the various radionuclides in the nuclear waste. This work focuses on the interaction of uranium, as main component of spent nuclear fuel, with Opalinus Clay and studies the influence of humic acid and elevated temperature on this interaction. For investigation of the retention behavior of the clay and the mobility of U(VI) in the system, batch sorption and diffusion experiments were performed. To clarify which U(VI) and humic acid species were present under the applied conditions, aqueous speciation modeling was used. Additionally, the U(VI) speciation in solution and on the clay surface was investigated by spectroscopic methods. Prior to the investigation of the ternary system U(VI) / humic acid / clay, the applied batches of Opalinus Clay were characterized (e.g., specific surface area, carbon content, cation exchange capacity, elemental composition, particle size distribution). Leaching studies with Opalinus Clay in synthetic Opalinus Clay pore water (pH 7.6, It = 0.34 mol/L) and in NaClO4 (pH 3 – 10, I = 0.1 mol/L) were performed to identify the competing ions and their concentrations in the background electrolytes. These data were used to calculate the U(VI) and humic acid speciation in solution. Calcium and carbonate ions are present under pore water conditions as well as in 0.1 mol/L NaClO4 from pH 7 to 8.5, due to dissolution of calcite (mineral fraction in Opalinus Clay). Thus, the U(VI) speciation is dominated by the aquatic Ca2UO2(CO3)3 complex. In the case of pore water, Ca2UO2(CO3)3(aq) is also the dominant U(VI) species in the presence of humic acid, which was corroborated by time-resolved laser-induced fluorescence spectroscopic measurements. A significantly changed speciation was found in 0.1 mol/L NaClO4 in the presence of humic acid. At pH > 7, the negatively charged UO2(CO3)2HA(II)4– complex determines the U(VI) speciation, thus repressing the Ca2UO2(CO3)3(aq) complex. In addition, the speciation of humic acid is influenced from ions leached out from Opalinus Clay. The CaHA(II) complex is the dominating humic acid species in solution. Batch sorption experiments in 0.1 mol/L NaClO4 showed that Opalinus Clay has the strongest retardation effect on U(VI) in the pH range from pH 4.5 to 7. However, under environmentally relevant conditions (pH > 7), the sorption of U(VI) onto Opalinus Clay is very weak. Under pore water conditions, a distribution coefficient (Kd) of 0.0222 ± 0.0004 m3/kg was determined, which was shown to be independent of solid-to-liquid ratios ≥ 60 g/L. In addition, in pore water, the U(VI) sorption onto Opalinus Clay is not influenced by humic acid, which is supported by the speciation results. Extended X ray absorption fine-structure investigations confirmed this batch sorption result. The U(VI) diffusion experiments performed in pore water at 25 °C with Opalinus Clay bore core samples confirmed the Kd value obtained by batch sorption experiments. In the diffusion experiments at 60 °C, a change in the U(VI) speciation occurred. Beside Ca2UO2(CO3)3(aq), a colloidal U(VI) species was formed. Almost equivalent apparent diffusion coefficient (Da) values were determined for the diffusion of the aqueous U(VI) species at 25 and 60 °C through Opalinus Clay. Thus, based on the investigations in the present study the breakthrough of U(VI) through Opalinus Clay is expected to be independent of the temperature and should occur nearly at the same time. Modeling calculations showed that it would take about 10 years until a detectable amount of 233U(VI) (1×10–9 mol/L) migrates through an 11 mm thick Opalinus Clay sample. Two distinct humic acid size fractions – a large- and a small-sized colloid fraction – diffused through the Opalinus Clay samples. Within three months, the high molecular size humic acid colloids migrated only about 500 µm into the clay, whereas the low molecular size fraction diffused through the entire Opalinus Clay samples and were consequently detected in the receiving reservoirs. These findings demonstrate a filtration effect of the compacted clay. The diffusion experiments revealed that the effect of humic acid on U(VI) diffusion is negligible and, under the studied conditions, independent of temperature. The obtained results contribute to data bases used for modeling of interaction and migration processes in uranium / clay rock systems. Thus, the collected sorption and diffusion data are not only relevant for safety assessment of nuclear waste repositories but also for any clay-containing system present in the environment, where the geochemical interaction with uranium contaminated water plays a role. Concerning the suitability of Opalinus Clay as host rock for a nuclear waste repository, it can be concluded, that Opalinus Clay has a relatively high retardation potential for U(VI). In case of water ingress U(VI) as part of the nuclear waste is released into the clay formation. Under near-neutral pH conditions, it will be complexed by calcium and carbonate ions leached out from Opalinus Clay, whereby Ca2UO2(CO3)3(aq) is formed. This complex is only weakly retarded by sorption onto the clay, which can contribute to an enhanced mobility of U(VI) in the host rock. However, the U(VI) migration through the clay rock is governed by molecular diffusion. This decelerates the migration of Ca2UO2(CO3)3(aq) through Opalinus Clay and thus it represents the decisive retardation process in the investigated system. Additionally, under environmentally relevant conditions, humic acid has no significant influence on U(VI) / Opalinus Clay interaction even at an elevated temperature of 60 °C. This was shown by speciation, sorption, as well as diffusion experiments
Eine weltweit diskutierte Strategie zum Umgang mit radioaktiven Abfällen ist deren Endlagerung in tiefen geologischen Formationen. Zur Abschirmung der Umwelt vor den schädlichen Einflüssen des radioaktiven Abfalls soll ein Multibarrierensystem bestehend aus technischen, geotechnischen und geologischen Barrieren im Endlager dienen. Dabei ist in Deutschland die Definition des einschlusswirksamen Gebirgsbereichs ein wichtiger sicherheitstechnischer Indikator. Tongestein wird als potentielles Endlagerwirtsgestein und Teil der geologischen Barriere international erforscht. In der vorliegenden Arbeit wurde das natürliche Tongestein Opalinuston aus dem Mont Terri Felslabor, Schweiz, untersucht. In Deutschland wird die direkte Endlagerung des abgebrannten Kernbrennstoffes ohne Wiederaufarbeitung des Brennstoffs favorisiert. Bei Wassereinbruch können Radionuklide aus dem Abfall in die Umgebung des Endlagers freigesetzt werden, d. h. sie können in Kontakt mit dem Wirtsgestein kommen. Ubiquitär in der Natur vorkommende Huminsäuren können mit den anorganischen Komponenten des natürlichen Tongesteins vergesellschaftet sein (1.5×10–3 Gew.-% in Opalinuston). Unter bestimmten Bedingungen können die Huminsäuren freigesetzt werden. Ihre Struktur enthält eine Vielzahl von funktionellen Gruppen, was sie zu starken Komplexbildnern für Metallionen macht. Sie besitzen Redoxeigenschaften und bilden in Lösung eine kolloidale Konformation aus. Aufgrund dieser Charakteristika können sie die Mobilität von Metallionen wie den Actinoiden beeinflussen. Weiterhin sind im Nahfeld eines Endlagers erhöhte Temperaturen zu erwarten, welche aus der Wärmefreisetzung beim radioaktiven Zerfall der verschiedenen Radionuklide im radioaktiven Abfall resultieren. Die vorliegende Studie konzentriert sich auf die Untersuchung der Wechselwirkung von Uran, als Hauptkomponente des endgelagerten abgebrannten Kernbrennstoffs, mit Opalinuston und untersucht dabei den Einfluss von Huminsäure und erhöhter Temperatur. Um das Rückhaltevermögen des Tongesteins gegenüber U(VI) und die U(VI)-Mobilität im System zu ermitteln, wurden Sorptions- und Diffusionsversuche durchgeführt. Zur Klärung, welche U(VI)- und Huminsäurespezies unter den untersuchten Bedingungen vorliegen, wurde die aquatische Speziation berechnet. Zusätzlich wurde die U(VI)-Speziation in Lösung und an der Tonoberfläche mit spektroskopischen Methoden untersucht. Vor der Untersuchung des ternären Systems U(VI) / Huminsäure / Ton wurden die eingesetzten Opalinuston-Chargen charakterisiert (z. B. spezifische Oberfläche, Kohlenstoffgehalt, Kationenaustauschkapazität, elementare Zusammensetzung, Partikelgrößenverteilung). Anschließend wurden Auslaugungsversuche mit Opalinuston in synthetischem Opalinustonporenwasser (pH 7.6, It = 0.34 mol/L) und in NaClO4 (pH 3 – 10, I = 0.1 mol/L) durchgeführt, um relevante Konkurrenzionen zu identifizieren und deren Konzentration in den Hintergrundelektrolyten zu bestimmen. Die erhaltenen Daten wurden zur Berechnung der U(VI)- und Huminsäurespeziation in Lösung verwendet. Unter Porenwasserbedingungen sowie in 0.1 mol/L NaClO4 von pH 7 bis 8.5 liegen, durch die Auflösung von Calcit (Mineralphase im Opalinuston), Calcium- und Carbonationen in Lösung vor. Dadurch wird die U(VI)-Speziation von dem aquatischen Ca2UO2(CO3)3-Komplex dominiert. Im Falle des Porenwassers ist Ca2UO2(CO3)3(aq) auch in Gegenwart von Huminsäure die dominierende U(VI)-Spezies. Dies wurde durch zeitaufgelöste laserinduzierte fluoreszenzspektroskopische Messungen nachgewiesen. Eine signifikante Änderung der U(VI)-Speziation tritt in 0.1 mol/L NaClO4 in Gegenwart von Huminsäure auf. Bei pH > 7 bestimmt der negativ geladene UO2(CO3)2HA(II)4–-Komplex die U(VI)-Speziation, wobei der Anteil von Ca2UO2(CO3)3(aq) zurückgedrängt wird. Auch die Huminsäurespeziation wird durch die vom Opalinuston ausgelaugten Ionen beeinflusst. So ist der CaHA(II)-Komplex die dominierende Huminsäurespezies in Lösung. Sorptionsversuche in 0.1 mol/L NaClO4 zeigten, dass Opalinuston gegenüber U(VI) den stärksten Retardationseffekt im pH-Bereich 4.5 bis 7 aufweist. Unter umweltrelevanten Bedingungen hingegen (pH > 7) ist die U(VI)-Sorption an Opalinuston sehr schwach. Unter Porenwasserbedingungen wurde ein Verteilungskoeffizient (Kd) von 0.0222 ± 0.0004 m3/kg ermittelt, der von Fest-Flüssig-Verhältnissen ≥ 60 g/L unabhängig ist. Außerdem wird die U(VI)-Sorption an Opalinuston in Porenwasser nicht von Huminsäure beeinflusst. Dies wird durch die Ergebnisse aus den Speziations-rechnungen unterstützt. Röntgenabsorptionsspektroskopische Untersuchungen bestätigten ebenfalls dieses Sorptionsergebnis. Die U(VI)-Diffusionsexperimente in Porenwasser bei 25 °C unter Verwendung von Opalinustonbohrkernstücken bestätigten den Kd-Wert der Sorptionsexperimente. In den Diffusionsexperimenten bei 60 °C trat eine Änderung in der U(VI)-Speziation auf. Neben Ca2UO2(CO3)3(aq) wurde eine kolloidale U(VI)-Spezies gebildet. Für die Diffusion der aquatischen U(VI)-Spezies durch Opalinuston bei 25 und 60 °C wurden annähernd gleiche scheinbare (apparente) Diffusionskoeffizienten (Da) bestimmt. Das bedeutet, der Durchbruch von U(VI) durch Opalinuston ist unabhängig von den hier untersuchten Temperaturen und wird deshalb etwa zum gleichen Zeitpunkt erwartet. Modellierungen zeigten, dass es etwa zehn Jahre dauern würde, bis eine detektierbare Menge an 233U(VI) (1×10–9 mol/L) durch ein 11 mm-dickes Opalinustonbohrkernstück migrieren würde. Zwei verschiedene Huminsäuregrößenfraktionen diffundierten durch die Opalinustonproben – eine große und eine kleine kolloidale Größenfraktion. Innerhalb von drei Monaten migrierten die hochmolekularen Huminsäurekolloide nur 500 µm in den Ton, während die niedermolekularen Huminsäurekolloide durch die gesamten Opalinustonproben diffundierten und dadurch im Auffangreservoir detektiert werden konnten. Diese Resultate demonstrieren den Filtrationseffekt des Tongesteins. Die Diffusionsversuche zeigten, dass der Einfluss von Huminsäure auf die U(VI)-Diffusion, unabhängig von der in dieser Arbeit verwendeten Temperatur, vernachlässigbar ist. Die erhaltenen Ergebnisse tragen zu Datenbanken bei, die für die Modellierung von Wechselwirkungs- und Migrationsprozessen in Uran / Tongestein-Systemen genutzt werden. Das bedeutet, die gesammelten Sorptions- und Diffusionsdaten sind nicht nur für den Langzeitsicherheitsnachweis eines Endlagers für radioaktive Abfälle von Relevanz, sondern auch für jedes tonhaltige System in der Umwelt, bei dem die geochemische Wechselwirkung mit urankontaminierten Wässern eine Rolle spielt. Bezüglich der Eignung von Opalinuston als Wirtsgestein für ein Endlager radioaktiver Abfälle lässt sich schlussfolgern, dass Opalinuston ein relativ hohes Retardationspotential bezüglich U(VI) aufweist. Wenn U(VI) als Bestandteil des radioaktiven Abfalls bei Wassereinbruch im Endlager in die Umgebung freigesetzt wird, wird es unter umweltrelevanten Bedingungen von Calcium- und Carbonationen, welche aus dem Opalinuston herausgelöst werden, komplexiert. Dabei bildet sich Ca2UO2(CO3)3(aq). Dieser Komplex wird nur schwach durch Sorption am Tongestein zurückgehalten, was zu einer erhöhten U(VI)-Mobilität im Wirtsgestein führen kann. Im untersuchten System wird die U(VI)-Migration durch das Tongestein jedoch durch molekulare Diffusion bestimmt. Sie verzögert die Migration von Ca2UO2(CO3)3(aq) durch Opalinuston und stellt somit den maßgeblichen Retardationsprozess im System dar. Huminsäure hat keinen signifikanten Einfluss auf die U(VI) / Opalinuston-Wechselwirkung, sogar bei einer erhöhten Temperatur von 60 °C. Dies wurde mittels Speziationsmodellierungen sowie durch Sorptions- und Diffusionsversuche gezeigt

En 1965, Roman Opalka ouvre son nouveau programme de peindre le temps en inscrivant la progression continue des nombres. Désormais, l’artiste remplit chaque toile par des séries de nombres blancs sur fond noir qui s’éclaircît, et ceci jusqu’à la fin de sa vie. Opalka livre à nos yeux sa vie, sa durée. Le « moi » de l’artiste et le sujet représenté sont inséparables. Ce travail s’intéresse à la valeur intime et artistique du programme d’Opalka. Il analyse les possibilités de penser le temps par l’intermédiaire de l’art et questionne les conditions d’une apparition plastique du temps, ainsi que les structures de cet apparaître. Les analyses phénoménologiques de Husserl et Heidegger au sujet du temps aident à découvrir le fait que les œuvres de Roman Opalka révèlent un apparaître du temps et non pas le temps en tant que tel. Dans la démarche opalkienne, il ne s’agit pas de pénétrer la manière dont le temps est saisi, mais la façon directe selon laquelle le temps est « éprouvé». A travers l’examen de la surface monochrome, ce travail analyse la partie indicible de la peinture, c’est-à-dire le silence d’une trace artistique. Il aborde également la question de l’éphémère et de l’inapparent, pour se focaliser ensuite sur la manière dont Opalka relève la catégorie d’éphémère au rang d’une nouvelle dimension de l’art. Cela permet de développer l’idée selon laquelle cette peinture donne à voir l’apparaître même et non pas ce qui apparaît. Ces recherches se concentrent également sur la problématique de la finitude, qui est au centre de la réflexion opalkienne sur le temps. Parce que cette existence picturale révèle non seulement une mise en corps de la vie, mais aussi sa mise à mort
In 1965 Roman Opalka embarked on his new project: to depict time by the inscription of a continuous series of numbers. Ever since, the artist has filled each successive canvas with series of white figures on a black ground witch would lighten. Hence, the sequence of canvases moves inexorably towards the invisible. He intends to go on doing so for the rest of his life. Artist book to us his life, his duration. Through the poetic interplay of these luminous transparencies, the artist strives to show what cannot be seen, to conjure into existence a non-image of white. In these canvases the unbearable lightness of the colour is revealed as substance, rather than as a mere attribute or accident. It explores the possibilities of thinking time through art and questions the conditions of an artistic appearance of the time. Phenomenological analysis of Husserl and Heidegger on time, helps us to discover that the works of Roman Opalka reveal a time and not time as such. This analysis also touch upon the matter of the ephemeral and the unapparent. Finally, we shall focus on the way that Opalka raises the ephemeral to the level of a new artistic dimension. This will permit us to develop the idea of how the painting shows us the very act of appearing, and not that which appears. It is no longer to penetrate the way the time is captured, but rather the direct way that the time is « proven ». The consequence of accepting this position is the understanding of time as a major category of contemporary philosophy, and especially phenomenology. This research is also focused on the problem of finiteness that is central to the thinking of Opalka on time

Les minéraux d’altération sont des objets clefs pour comprendre l’histoire géologique de la surface des corps planétaires. Dans ce travail de thèse, j’ai étudié les propriétés spectroscopiques proche-infrarouge de la silice opaline (e.g. opale) et de la kaolinite dans l’objectif de reconstituer les conditions de surface qui régnaient au début de l’histoire géologique de Mars. L’étude géomorphologique préliminaire des dépôts de silice opaline sur mars a permis de distinguer quatre grands types de gisements : dépôts éoliens, dépôts hydrothermaux, dépôts alluviaux et/ou deltaïques, et dépôts lités. Des critères spectroscopiques, permettant de distinguer opales d’altération continentale et opales hydrothermales, appliqués sur ces détections, montrent que les dépôts éoliens dérivent de dépôts hydrothermaux riches en silice préexistants. Les autres types de dépôts ont des origines d’altération continentale, à l’exception des dépôts hydrothermaux dont la signature spectrale suggère des processus hydrothermaux de basse température. Les propriétés proche-infrarouge de la kaolinite sont des indicateurs de son degré de “cristallinité”. Les kaolinites désordonnées sont exclusivement d’altération continentale alors que les kaolinites bien ordonnées peuvent se former indifféremment par hydrothermalisme ou altération continentale
Alteration minerals are key objects to understand the geological history of the planetary bodies’ surfaces. In this work, I studied the near-infrared spectroscopic properties of opaline silica (e.g. opal) and kaolinite in order to constrain the surface paleoclimatic conditions at the surface of Mars during the past. A preliminary geomorphologic study of opaline silica-bearing deposits on Mars shows four types of deposits : aeolian deposits, hydrothermal deposits, alluvial fan and fan delta deposits, and bedrock. Spectroscopic criteria, distinguishing continental weathering opals and hydrothermal opals, show that aeolian deposits are relicts of hydrothermal deposits. Other deposits are of weathering origin, except hydrothermal deposits that have a spectral signature consistent with low-temperature hydrothermal activity. Near-infrared properties of kaolinite are proxies of its “crystalline degree”. Poorly-ordered kaolinites are exclusively of continental weathering origin while well-ordered kaolinites can form either by hydrothermal activity or continental weathering alteration processes

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 315-327).
The extraction of hydrocarbons from unconventional oil and gas reservoirs relies on a detailed understanding of the fracture processes in shale. Also, underground structures designed for nuclear waste repositories are typically constructed in shale due to its characteristic low permeability. To understand the behavior of shale it is important to know how cracks initiate, propagate and coalesce. Although there have been many studies on the cracking processes in rock, cracking in shale is not well understood mainly due to its anisotropy, which is caused by naturally formed bedding planes. Natural bedding planes are weak zones along which cracks can initiate and propagate. As a consequence, the effect of bedding planes on crack initiation and propagation has not been captured well in previous models. A series of unconfined compression tests were conducted on Opalinus shale extracted from the Mont Terri underground rock laboratory in Switzerland. These tests consisted of prismatic Opalinus shale specimens with two pre-existing flaws and various bedding plane orientations. High speed and high resolution imagery were used to capture crack initiation, -propagation and -coalescence between the flaw pairs. It was found that as the bedding plane angle increased, cracks initiating at the flaw tips tended to propagate more frequently along the bedding planes. FROCK, a model based on the Displacement Discontinuity Method (a type of Boundary Element Model) developed at MIT, was modified to incorporate the effect of bedding planes on the crack propagation patterns. A discontinuous critical strain criterion was implemented into the model, showing acceptable predictions of the crack initiation, -propagation pattern and -mode (tensile/shear) when compared to the experimental results. The results from this thesis can be used to further improve predictive crack propagation models in anisotropic rock.
by Stephen Philip Morgan.
Ph. D.