Diss. Naturwiss. Bern (kein Austausch). / Mit dt. Zsfg.

Diss. Phil.-Naturwiss. Bern, 1988.

Noble metal nanomaterials have numerous uses in plasmonic and surface enhanced Raman scattering (SERS) detection applications; however, upon the addition of analytes, nanomaterials often undergo uncontrolled aggregation which leads to inconsistent signal intensities. To overcome this limitation, the effect of gold nanosphere concentration, column purification, and surface chemistry functionalization using internally etched silica stabilization methods was investigated on SERS assays for small molecule detection. Nanostructure composition, size, shape, stability, surface chemistry, optical properties, and SERS-activity were monitored using localized surface plasmon resonance (LSPR or extinction) spectroscopy, transmission electron microscopy (TEM), and Raman spectroscopy. First, the behavior of citrate-stabilized gold nanospheres was monitored as a function of molecular surface coverage. Both extinction and SERS spectral intensities increased linearly below monolayer functionalization. Above this value, however, uncontrolled nanoparticle aggregation occurred and large but irreproducible SERS signal intensities were monitored. Next, gold nanoparticles were encapsulated with varying silica shell thicknesses and purified using traditional centrifugation steps and/or column chromatography. Relative to the traditionally purified (i.e. centrifuged) samples, the SERS responses from small molecules using the column purified nanoparticle samples followed a well-known SERS distance-dependence model. Thus, surface chemistry cannot form more than a 2 nm thick layer on gold nanospheres if SERS applications were targeted. To overcome these challenges, gold nanospheres encapsulated with a thick silica shell were made SERS-active by etching the internal silica layer near the metal surface. During the synthesis of these internally etched silica-coated gold nanospheres, the LSPR wavelength shift, a parameter related to the effective local refractive index near the gold core, was monitored instead of etching time, in order to produce nanostructures with more uniform internal silica etching from sample to sample. The SERS-activity of a target molecule using these nanostructures was measured as a function of LSPR wavelength shift. SERS signal intensity increased, which suggested that more analyte molecules were able to bind to the gold surface because of the larger pore size in the silica layer near the metal core. Further exploration of these findings should increase the integration of solution-phase nanoparticles in more predictable functions in future applications, resulting in more quantitative and reproducible molecular detection in complex sample matrices, including biological and environmental samples.

Universiẗat, Diss., 2002--Bonn.

Full Waveform Inversion (FWI) is a non-linear optimization problem aimed to estimating subsurface parameters by minimizing the misfit between modeled and recorded seismic data using gradient descent methods, which are the only practical choice because of the size of the problem. Due to the high non-linearity of the problem, gradient methods will converge to a local minimum if the starting model is not close to the true one. The accuracy of the long-wavelength components of the initial model controls the level of non-linearity of the inversion. In order for FWI to converge to the global minimum, we have to obtain the long wavelength components of the model before inverting for the short wavelengths. Ultra-low temporal frequencies are sensitive to the smooth (long wavelength) part of the model, and can be utilized by waveform inversion to resolve that part. Unfortunately, frequencies in this range are normally missing in field data due to data acquisition limitations. The lack of low frequencies can be compensated for by utilizing wide-aperture data, as they include arrivals that are especially sensitive to the long wavelength components of the model. The higher the scattering angle of a 5 recorded event, the higher the model wavelength it can resolve. Based on this property, a scattering-angle filtering algorithm is proposed to start the inversion process with events corresponding to the highest scattering angle available in the data, and then include lower scattering angles progressively. The large scattering angles will resolve the smooth part of the model and reduce the non-linearity of the problem, then the lower ones will enhance the resolution of the model. Recorded data is first migrated using Pre-stack Exploding Reflector Migration (PERM), then the resulting pre-stack image is transformed into angle gathers to which an angle filtering process is applied to remove events below a certain cut-off angle. The filtered pre-stack image cube is then demigrated (forward modeled) to produce filtered surface data that can be used in waveform inversion. Numerical tests confirm the feasibility of the proposed filtering algorithm. However, the accuracy of the filtered section is limited by PERM’s singularity for horizontally-traveling waves, which in turn is dependent on the velocity model used for migration and demigration

Thesis (doctoral)--Universität zu Köln, 1982. / Bibliography: p. 131-144.

The Karoo-aged basins evolved from assembly to break-up of the supercontinent Gondwana and were filled by denudating major mountain ranges accompanied by vast sedimentary recycling processes. A succession of rift episodes caused the emergence of a great number of these intra-cratonic basins throughout the Gondwana interior, e.g. the Aranos, Karasburg and Huab basins, which are scattered across today’s Namibia. This evolution may be split into a Permian to early Triassic and a Jurassic phase. The Karoo I phase is confined by ‘passive’ continental rifting and a retro-arc extension at the SW margin of Gondwana. The early Jurassic Karoo II rifting phase of east Africa eventually disintegrated Gondwana and led to the opening of the West Indian Ocean. A terminal early Cretaceous rifting phase led towards the opening of the southern Atlantic Ocean and ended the Gondwana supercontinent sedimentary regime. In the course of this evolution, the Namibian late Paleozoic to Mesozoic sedimentary record yields evidence for changing climates from icehouse towards extreme hothouse conditions. As based on sporadic datings the timeline of this evolution remains mostly unclear. The lack of data is in great contrast to the importance of determining the speed of major climate changes. In addition, sediment fluxes within such a supercontinent regime are not well studied but are key in understanding sediment dynamics during severe ecological and environmental changes. Therefore, this thesis tries to establish a timeframe of the sedimentary deposits for the Namibian Karoo Supergroup sedimentary deposits and furthermore tries to explore the laws of sediment dispersal prevailing in southern Gondwana. In order to answer these research questions a comprehensive dataset comprised of 41 samples with more than 5.700 U-Th-Pb LA-ICP-MS age determinations and over 1.000 Lu-Hf isotopic measurements on single zircon grains of siliciclastic rock material of the vast majority of all Permo- Carboniferous to early Cretaceous Karoo-aged Namibian formations was compiled. All of the investigated zircon crystals were also studied with respect to their grain morphology, including length, width, surface, and roundness, providing valuable information concerning transport distances and energies. In combination with whole-rock geochemical data of a majority of the investigated samples, they help deciphering the sedimentary deposition history during the Gondwana supercontinent cycle. A compiled set of southern African U-Th-Pb zircon age data is of great help interpreting sediment fluxes and inferring provenance areas. The onset of Karoo-aged sedimentation is recorded within the Aranos and Karasburg Basin successions and is represented by glacially induced diamictites of the Dwyka Group partially resting directly on pre-Cambrian basement complexes. In places, two distinct E-W directed ice advances are present. The deposition of these glacial diamictites was prior to 296 Ma, as two ash beds incorporated within the overlying shale successions yield Asselian deposition ages. Further hints concerning ice-induced deposition disappear at the Sakmarian-Artinskian boundary, as the lowermost succession of the Ecca Group yields a maximum deposition age of ca. 290 Ma, documenting the end of the Dwyka ice age in the southern Namibian area. The lowermost Ecca Group deposits of the Huab Basin yield a maximum deposition age of ca. 295 Ma, suggesting an earlier termination of the Dwyka ice age in the north. The uppermost strata of the Aranos and Karasburg Basins were dated ca. 265 Ma and 255 Ma, respectively, revealing a disparate depositional history. Due to a lack of datable ash beds as well as no detrital zircon grain ages near the assumed sedimentation age it was not possible to determine a detailed sedimentation history for the Huab, Kunene River, and Waterberg Basin deposits. Detrital zircon U-Th-Pb ages are routinely used in order to trace siliciclastic sedimentary rocks to their bedrock sources, deriving transport directions. This classic ‘source-to-sink’ approach is most likely obscured by several cycles of sediment homogenization processes. A majority of all investigated samples yield high portions of detrital zircon fractions of late Mesoproterozoic (950-1150 Ma) and Neoproterozoic (440-650 Ma) age. In addition, all Jurassic and Cretaceous samples yield a prominent Permian age fraction of 250-280 Ma, suggesting a Gondwanides orogen provenance. Thus, the investigated siliciclastic rocks consist of already recycled sedimentary material. This observation is supported by a high degree of zircon grain roundness. As of zircon grain hardness long transport distances are necessary to achieve latter. This suggests that one sedimentary sink is source for the next sedimentary cycle. A comparison with the detrital zircon record of other southern Gondwanan Permo-Carboniferous successions shows similar results, strongly pointing towards a supercontinent-wide sedimentary recycling regime. Therefore, detrital zircon age patterns within supercontinent scenarios reflect large-scale sedimentary processes rather than primary provenance information.:1 Introduction 1 1.1 Evolution of the Namibian landscape from Carboniferous to Cretaceous times 2 1.2 Thesis format 5 1.3 References 5 2 Methods 10 2.1 Sample preparation and zircon morphometrics 10 2.2 U-Th-Pb age determination 10 2.3 Lu-Hf model age determination via LA-(MC)-ICP-MS 12 2.4 Geochemical analysis 12 2.5 Comparative statistics 12 2.6 References 13 3 Study I: The Permo-Carboniferous Dwyka Group of the Aranos Basin (Namibia) – How detrital zircons help understanding sedimentary recycling during a major glaciation 15 3.1 Introduction 17 3.2 Regional geological setting 17 3.2.1 Geology of the Permo-Carboniferous Dwyka Group (Aranos Basin) 19 3.2.2 Paleotectonic significance of the Dwyka formations 22 3.3 Methods 24 3.4 Results 26 3.5 Discussion 30 3.5.1 Significance of zircon morphologies for sediment fluxes 32 3.5.2 Potential sedimentation rates and source areas indicated by U-Pb age data 35 3.5.3 Implications for the evolution of the Dwyka Group 42 3.6 Conclusions 46 3.7 References 47 4 Study II: The evolution of the southern Namibian Karoo-aged basins: Implications from detrital zircon geochronologic and geochemistry data 63 4.1 Introduction 64 4.2 Geology of the Aranos and Karasburg basins 66 4.3 Tectonic and structural framework of the southern African Karoo aged basins 70 4.4 Methods 71 4.5 Results 75 4.6 Discussion 80 4.6.1 Timing of the Formation of the Aranos and Karasburg basins 80 4.6.2 Provenance and evolution of the upper Paleozoic Aranos and Karasburg basins 85 4.6.3 Implications for the Karoo-aged basin sedimentary record 93 4.7 Conclusions 95 4.8 References 98 5 Study III: Mesozoic deposits of SW Gondwana (Namibia): Unravelling Gondwanan sedimentary dispersion drivers by detrital zircon 109 5.1 Introduction 110 5.2 Geological background 113 5.2.1 Evolution of the southwestern Gondwanan Mesozoic successions 113 5.2.2 Namibian Mesozoic successions 117 5.3 Methods 120 5.4 Results 123 5.5 Discussion 130 5.5.1 Protosources of the sediments 130 5.5.2 Recycling dynamics of the Mesozoic sediments 133 5.6 Conclusions 139 5.7 References 140 6 Study IV: Tracing southern Gondwanan sedimentary paths: A case study of northern Namibian Karoo-aged sedimentary rocks 153 6.1 Introduction 154 6.2 Geological setting 156 6.2.1 SW Gondwanan rifting history and sediment dispersal 156 6.2.2 The northern Namibian Karoo-aged Huab Basin and Kunene section 157 6.3 Methods 161 6.4 Results 165 6.5 Discussion 175 6.5.1 Timing of deposition of the Huab Basin strata 175 6.5.2 Protosources of the sediments 176 6.5.3 Detrital zircon grain morphology and isotope analysis 178 6.5.4 The northern Namibian Karoo-aged basins within the southern Gondwanan framework 185 6.6 Conclusions 186 6.7 References 187 7 Conclusions and outlook 199 8 Supplements 201

Effective risk communication is based on appropriate risk characterization. A reevaluation of the 1987 US EPA radon risk categorization of Unicoi County Tennessee was conducted using in-home radon concentrations, determined in a long-term monitoring study. Radon concentrations were measured in 69 homes using Electret Passive Environmental Radon Monitors (E-PERM’s), following standard methods. Radon concentrations determined in this study (avg. 4.03 ± 3.04) were significantly higher than those measured in the USEPA study (avg. 1.96 ± 1.08). Using this study’s data, the risk categorization was recalculated with the US EPA Radon Index Matrix Model. The model re-categorized Unicoi County from a moderate to a high risk zone classification. These results suggest that the health risks associated with in-home radon concentrations are inaccurately categorized and communicated to the citizens of Unicoi County, Tennessee.

This thesis is primaly focus on solving of comparison of ancient with recent coniferous forests and peat bogs in Central Europe. Discovered fossil records provide the detailed insight view to functions and interactions among individual components of former vegetation in the Carboniferous and the Early Permian compared to recent period. Another aspect is possible impacts of ancient pathogen activities to timber and foliage in analogy to recent ones.

Computertomographie (CT) ist eine nicht-destruktive bildgebende Methode, die in den letzten Jahren häufig bei fossilen Wirbeltierschädeln angewendet wird und Paläontologen ermöglicht bisher unbekannte interne Schädelmerkmale zu untersuchen. Letztere sind bedeutend um die Gehör- und Gehirnevolution, Gesichtsinnervation, den Zahnwechsel und den Ursprung von Endothermie entlang der Stammlinie der Säugetiere (Synapsida) zu verdeutlichen. Obwohl interne Schädelmerkmale in den letzten Jahren bei zahlreichen Therapsiden beschrieben wurden, sind sie bisher von der Wissenschaft weitestgehend vernachlässigt worden, verglichen mit den gut erforschten äußeren craniodentalen Merkmalen bei Synapsiden und wurden daher in phylogenetischen Analysen überwiegend vernachlässigt. In dieser Doktorarbeit stelle ich eine Neubewertung der der Phylogenie der Eutheriodontier (die Synapsidengruppe bestehend aus Cynodontia+Therocephalia) und eine Beurteilung der Merkmalsevolution innerhalb dieser Gruppe bereit. Der Ursprung der Cynodontier, die Ahnen der Säugetiere, stellt einen der bedeutendsten, bisher ungelösten Probleme in der Evolution der Therapsiden dar. Es ist bekannt, dass die Cynodontier am engsten mit den Therocephaliern verwandt sind, jedoch sind die genauen Verwandtschaftsverhältnisse bisher nicht eindeutig geklärt. Obwohl eine wesentliche Dichotomie in der abgeleiteten triassischen Subklade Eucynodontia in der Phylogenie der Cynodontia gut unterstützt wird, bleiben die Verwandtschaftsverhältnisse basalerer Cynodontier derzeit ungelöst. Anhand von CT Daten, die anhand eines ausgiebigen Datensatzes von Exemplaren der am frühesten bekannten (oberpermischen und untertriassischen) Cynodontier, sowie einiger ausgewählter Therocephalier und höherer (mitteltriassischer) Cynodontier (Eucynodontia) gewonnen wurden, konnte ich neue interne Schädelmerkmale dieser Tiere beschreiben. Diese Daten wurden anschließend in einem neuen, umfassenden phylogenetischen Datensatz dieser Gruppe integriert. / Computed tomography (CT) is a non-destructive imaging technique that has been widely used on fossil vertebrate crania in recent years and allowed paleontologists to investigate previously-obscure endocranial data. The latter have been instrumental in elucidating patterns of ear and brain evolution, facial innervation, tooth replacement and the origin of endothermy along the mammalian stem lineage (Synapsida). Although endocranial characters have been described for various synapsids in recent years, they remain understudied compared to the well-known external craniodental features in synapsids and have been largely ignored in phylogenetic analyses. In this thesis, I provide a re-evaluation of the phylogeny of Eutheriodontia (the synapsid subclade consisting of Cynodontia+Therocephalia) and an assessment of character evolution within the group. The origin of cynodonts, the group ancestral to (and including) mammals, is one of the major outstanding problems in therapsid evolution. It is well-established that cynodonts are most closely related to Therocephalia among the major synapsid groups, but the exact nature of this relationship is uncertain. Furthermore, although a fundamental dichotomy in the derived Triassic subclade Eucynodontia is well-supported in cynodont phylogeny, the relationships of more stemward cynodonts are currently unresolved. Using CT data derived from extensive sampling of the earliest known (late Permian and Early Triassic) cynodonts and selected exemplars of therocephalians and later (Middle Triassic onwards) cynodonts (eucynodonts), I described novel aspects of the endocranial anatomy of these animals. These data were incorporated into a new, taxonomically comprehensive phylogenetic dataset of the group.