738 research outputs found

    The Second Conference on Lunar Bases and Space Activities of the 21st Century, volume 1

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    These papers comprise a peer-review selection of presentations by authors from NASA, LPI industry, and academia at the Second Conference (April 1988) on Lunar Bases and Space Activities of the 21st Century, sponsored by the NASA Office of Exploration and the Lunar Planetary Institute. These papers go into more technical depth than did those published from the first NASA-sponsored symposium on the topic, held in 1984. Session topics covered by this volume include (1) design and operation of transportation systems to, in orbit around, and on the Moon, (2) lunar base site selection, (3) design, architecture, construction, and operation of lunar bases and human habitats, and (4) lunar-based scientific research and experimentation in astronomy, exobiology, and lunar geology

    Neanderthal activity and resting areas from Stratigraphic Unit 13 at the Middle Palaeolithic site of Oscurusciuto (Ginosa - Taranto, Southern Italy).

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    open9noStratigraphic Unit 13 of Oscurusciuto Rockshelter (Ginosa, Taranto, Southern Italy) is a short Mousterian palimpsest representing the first stable occupation of the site soon after the deposition of a thick layer of tephra (Mt. Epomeo Green Tuff - Ischia datable around 55 kya BP). Different activities were identified by integrating the study of lithic finds, faunal remains, and the microarchaeology of combustion features. Additionally, geo-statistical analysis of these data has been carried out using a specifically designed geodatabase within a GIS platform. Our results produced an articulated picture of this Neanderthal site as a tripartite location made of spatially segregated and integrated activity areas. A hearths' alignment (parallel to the rockshelter wall) divides the settled area into an inner and outer part. The inner part, between the hearths and the shelter wall, displays an abrupt rarefaction of the anthropic finds and was interpreted as a possible sleeping/ resting area. In the outer part, several multipurpose activity areas have been identified, mostly associated with the combustion features. The Northern sector of the settlement appears devoted particularly to lithic production (to a lesser degree, activities related with lithic tools use and faunal processing took place). In the Southern sector the main activities carried out represent more intensive production and use of lithic tools and the butchering and consumption of animal resources. Additionally, in this sector evidence of space maintenance behaviour (cleaning up of working areas and refuse dumping) has been attestedopenSpagnolo V., MARCIANI G., Aureli D., Berna F., Toniello G.; Astudillo F.; Boscato P., Boschin F., Ronchitelli A.Spagnolo V., MARCIANI G., Aureli D., Berna F., Toniello G.; Astudillo F.; Boscato P., Boschin F., Ronchitelli A

    Proceedings of 2006 Kentucky Water Resources Annual Symposium

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    This symposium was funded in part by the U.S. Environmental Protection Agency, with Clean Water Act, Section 319(h) grant money through the Kentucky Division of Water and the Kentucky Waterways Alliance, #C9994861-00. Planning for this conference was conducted as part of the state water resources research annual program with the support and collaboration of the Department of Interior, U.S. Geological Survey and the University of Kentucky Research Foundation, under Grant Agreement No. 01HQGR0133. The views and conclusions contained in this document are those of the abstract authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government or other symposium organizers and sponsors

    Colorado Natural Heritage Program projects 2010-2012

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    With numerous projects every year, CNHP has the opportunity to work in all of Colorado's habitats including high and low elevations, wet and dry habitats, and all four corners of the state. Along with the varied terrain, we also work with a variety of subjects that include all major taxonomic groups and ecological communities. The common thread that ties all of these inventory, monitoring, and planning projects together is our commitment to providing quality conservation science

    3D Bioprinting of multi-phasic osteochondral tissue substitutes: design criteria and biological functionality in vitro

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    Osteochondral defects comprise cartilage and bone tissue in the joint region and create challenges for orthopedic surgery, also because intrinsic regeneration capacities of the articular cartilage are limited. Furthermore, tissue layer-specific characteristics regarding cell types, mechanical properties and biochemical composition need to be considered. Research questions: In this work, concepts were developed which allow mimicking of osteochondral interfacial layers in a patient-individual and zonally specified manner by 3D extrusion (bio)printing. This feature of patient specificity was proven on different levels within this project: Besides the option for application of patient-own, expanded stem cells or chondrocytes within a scaffold to support regeneration and neo-tissue formation, a workflow was implemented which enables the consideration of magnetic resonance imaging (MRI) data and zonal geometry of the defect. With the materials suitable to achieve this design and a bioprinting-compatible process, the impact of such a system on embedded cells was investigated. A zonally structured, partly mineralized construct was evaluated regarding its capability to allow or support chondrogenesis of primary human chondrocytes (hChon). Furthermore, a strategy based on core-shell bioprinting technology was developed which allows simultaneous embedding of different cell types in a zonally defined distribution with a targeted effect by incorporated growth factors while reducing the off-target effects that would be expected when applied homogeneously via the surrounding medium. In addition, hybrid multi-material scaffolds were developed to adjust the stiffness of these systems. Materials and methods: To define design and patient-specific requirements for an osteochondral implant, an anonymized MRI dataset of a patient with osteochondritis dissecans (OCD) was used. The main constituent of the developed fabrication system was a bioink based on 3% alginate and 9% methylcellulose (algMC) with hChon. Laponite was added to alg-MC-based inks in order to control the release of differentiation factors for a sustained delivery in multi-zonal osteochondral constructs. A printable calcium phosphate cement (CPC) was used as a mineral phase. For the bioprinting process, multi-channel extrusion was applied for an alternating printing of hChon-laden algMC and CPC in order to mimic a zone of mineralized cartilage. Cell fate was investigated on biochemical and gene expression level. A coaxial extrusion module was applied for the co-extrusion of a bioink (shell) – algMC or plasma-functionalized algMC loaded with hChon or human pre-osteoblasts (hOB), respectively – and a biomaterial ink (core) doped with the corresponding growth factors TGF-β3 or BMP-2 as central target-specific factor depot. By melt electrowriting technology (MEW), additional scaffolds from polycaprolactone (PCL) microfibers with a freely adjustable fiber structure were generated. To trigger the mechanical stiffness of cell-laden hydrogels, these scaffolds were manually added to the bioprinting process as an extra support. Results: Suggested strategies of 3D extrusion (bio)printing for clinically relevant dimensions (Publication I)were successfully applied on algMC-based inks, bioinks and CPC to generate multi-material cell-laden constructs of an individual, patient-specific shape. With the use of flexible and reversible software solutions, MRI data from an OCD patient were utilized for the design and later fabrication of a bi-zonal implant (Publication II). The resulting implant showed a suitable geometry fitting into a model of the lesioned femoral condyles fabricated by stereolithography. For surgical fixation of such a potential implant, an individual implantation adapter was developed. The same materials processable via multi-channel printing were compatible with bioprinting of hChon isolated from the femoral head of human hip arthroplasty patients. The majority of cells survived the printing process and cultivation conditions in monophasic scaffolds consisting of cell-laden algMC, and in biphasic scaffolds with a zonally separated or interwoven mineral zone of calcium phosphate cement. Cells in both setups, representing plain articular cartilage and calcified cartilage, were able to re-differentiate and demonstrated the characteristic ECM marker production and gene expression. The calcium-deficient CPC led to a decrease of calcium ions and an initial increase of phosphate ions in the surrounding medium. In the presence of the CPC phase, chondrogenesis was enhanced (Publication III). The core-shell bioprinting concept allowed the spatially defined differentiation of cells (hChon or hOB), encapsulated in a bioink extruded as shell compartment, adjacent to a respective factor-loaded core depot with specific differentiation factors. The biomaterial inks for the core depot were successfully adjusted regarding viscosity and release kinetics by addition of nanoclay (Laponite) nanoparticles. Optical coherence tomography (OCT) was introduced as a tool to monitor the coaxial strand pattern and the location of embedded cells in a contactless manner. The applied inks allowed adjustment of release properties of components such as growth factors BMP-2 and TGF-β3. In hChon, characteristic genes such as collagen 2 or aggrecan were upregulated, while hOB were able to express the typical genes ALP, BGLAP and IBSP. Although both incorporated differentiation factors also demonstrated enhancing effects on both compartments, respectively, the induced adverse effects of hypertrophy in the cartilage zone and collagen 2 expression in the bone zone were successfully prevented. This was done by applying the factors with a sustained release via a Laponite-supported ink as the core depots, instead of homogeneously supplementing the surrounding cell culture medium (Publication IV). By adding PCL microfiber mesh scaffolds, fabricated by MEW, with a decreasing fiber density from 1000 to 250 µm, the Young’s modulus of the algMC scaffolds increased from 10 kPa to more than 50 kPa. The resulting hybrid scaffolds were proven cytocompatible; bioprinted hChon reacted to this hybrid algMC structure with a PCL density of 750 µm with an improved release of sulphated glycosaminoglycans (Publication V). Conclusions: A fully integrated approach for a multiphasic implant design, embedding of primary cells and simultaneous application of respective growth factors was realized by 3D extrusion (bio)printing. Concepts for bioprinting of mineralized cartilage based on algMC and CPC and for local factor delivery in osteochondral tissue substitutes by core-shell bioprinting were developed. The presented approaches allow an adjustable zonal design and full control over spatial differentiation and fate of bioprinted cells. The versatility of this modular system allows addition of further features as demonstrated for the combination with PCL microfiber scaffolds to adjust mechanical properties of the cartilage zone. Another option can be the mechanical stimulation of magnetically deformable algMC-magnetite scaffolds. These valuable insights for the field will serve as basis for further applications in vitro and in vivo. They might open up new research directions with a potential translation to other material combinations and other tissue defect types.:Table of Contents List of abbreviations List of figures Legal note 1. Introduction 1.1 The osteochondral interface – function, anatomy and histology 1.2 Pathology of cartilage and osteochondral tissue 1.3 State of the art: treatment of cartilage defects and osteochondral defects 1.4 Tissue engineering for osteochondral regeneration 1.5 Biomedical additive manufacturing and bioprinting 1.6 Hydrogels for bioprinting 1.7 Multi-component and multiphasic strategies to add specific cues and features to bioprinted tissue models 1.8 Additive Manufacturing of patient-specific bone and cartilage substitutes 2. Aims of the thesis List of publications included in the thesis 3. Strategies for biofabrication of volumetric constructs with an individual shape (Publication I) Publication I: Review article 4. Workflow for an MRI-guided, bi-zonal implant design (Publication II) 41 Publication II: Article Publication II: Published supporting information 5. Chondrogenesis in 3D bioprinted constructs and its compatibility with a mineral phase (Publication III) Publication III: Article Publication III: Published supporting information 6. Concept for a zonally defined factor delivery (Publication IV) Publication IV: Article Publication IV: Published supporting information 7. Hybrid bioscaffolds for tailoring mechanical properties of cartilage tissue substitutes (Publication V) Publication V: Article 8. Discussion and outlook References SUMMARY ZUSAMMENFASSUNG Acknowledgements List of other publications (co-)authored by the candidate Scientific congress contributions during PhD phase Journal ranking in Journal Citations Report Appendix I – Erklärungen zur Eröffnung des Promotionsverfahrens Appendix 2 – Erklärung zur Einhaltung gesetzlicher BestimmungenOsteochondrale Defekte umfassen Knochen- und Knorpelgewebe innerhalb des betroffenen Gelenks und stellen die klinische Orthopädie vor Herausforderungen dar, auch da die intrinsische Regenerationsfähigkeit des Gelenkknorpels stark limitiert ist. Zudem sind in den zu unterscheidenden Gewebeschichten spezifische Charakteristika wie unterschiedliche Zelltypen, mechanische Eigenschaften und die biochemische Zusammensetzung zu berücksichtigen. Fragestellungen: In der vorliegenden Arbeit wurden Konzepte entwickelt, mit dem sich per 3D-Extrusions(bio)druck Gewebeschichten dieser osteochondralen Grenzschicht zonenspezifisch und patientenindividuell nachbilden lassen. Diese patientenindividuellen Merkmale wurden innerhalb des Projektes auf mehreren Ebenen nachgewiesen: Zum einen können patienteneigene Stammzellen oder Chondrozyten nach Vermehrung im Labor innerhalb einer Gerüststruktur (“Scaffold”) zur Unterstützung der Regeneration und Gewebeneubildung angewandt werden. Zum anderen wurde ein Workflow vorgestellt, der die Berücksichtigung einer individuellen, per Magnetresonanztomographie (MRT) detektierten, schichtweisen Geometrie einer Läsion erlaubt. Mit Hilfe von Materialien, die diese Formgebung ermöglichen, wurde in einem Biodruck-kompatiblen Prozess der Einfluss eines solchen Systems auf eingebettete Zellen untersucht: Ein zonal aufgebautes, teilweise mineralisiertes Konstrukt wurde hinsichtlich dessen Eignung, Chondrogenese humaner Knorpelzellen (hChon) zu ermöglichen oder zu unterstützen, evaluiert. Zudem wurde eine auf der Kern-Mantel-Biodrucktechnologie basierende Strategie entwickelt, die das Einbetten unterschiedlicher Zelltypen mit zonal definierter Verteilung kombiniert mit einem gezielten Effekt durch inkorporierte Wachstumsfaktoren. Hierbei sollten unerwünschte Nebeneffekte der im Kern dargebrachten Faktoren auf die jeweils andere Zellsorte, die man bei homogener Faktorengabe über das umgebende Medium erwarten würde, reduziert werden. Weiterhin sollte mittels hybrider Multi-Material-Scaffolds die Steifigkeit des Systems angepasst werden. Material und Methoden: Um ein Design und patientenindividuelle Anforderungen für ein osteochondrales Implantat zu definieren, wurde ein anonymisierter MRT-Datensatz eines Osteochondrosis dissecans(OCD)-Patienten genutzt. Hauptbestandteil des entwickelten Fabrikationssystems war eine Biotinte aus 3% Alginat und 9% Methylcellulose (algMC) mit hChon. Laponit wurde zu den auf algMC basierenden Tinten hinzugefügt, um die Freisetzung von Differenzierungsfaktoren zu kontrollieren und damit eine verzögerte Gabe in mehrschichtigen osteochondralen Konstrukten zu ermöglichen. Ein druckbarer Kalziumphosphatzement (CPC) wurde als Mineralphase genutzt. Im Biodruckprozess wurde der Mehrkanaldruck angewandt, um durch alternierende Extrusion von hChon-beladenem algMC und CPC die mineralisierte Knorpelschicht nachzubilden. Die Zellentwicklung wurde auf biochemischer Ebene und hinsichtlich der exprimierten Gene untersucht. Ein koaxiales Extrusionsmodul wurde zur Ko-Extrusion einer Biotinte (Mantel), bestehend aus algMC beladen mit hChon oder Plasma-funktionalisierter algMC beladen mit humanen Prä-Osteoblasten (hOB), und einer korrespondierenden faktorenbeladenen Biomaterialtinte (Kern) genutzt. Dieses zielspezifische Faktorendepot enthielt jeweils TGF-β3 oder BMP-2. Durch die Technik des Melt Electrowritings (MEW) wurden zusätzliche Scaffolds aus Polycaprolacton(PCL)-Mikrofasern mit einer justierbaren Faserstruktur generiert. Um die Steifigkeit von zellbeladenen Hydrogelen anzupassen, wurden diese Scaffolds als mechanischer Support manuell während des Biodruckprozesses eingebracht. Ergebnisse: Die zugrundeliegenden Strategien des 3D-Extrusions(bio)drucks in klinisch relevanten Dimensionen (Publikation I) wurden an algMC-basierten Tinten, Biotinten und CPC erfolgreich angewandt, um zellbeladene Konstrukte patientenindividueller Form aus mehreren Materialien zu generieren. Durch den Einsatz flexibler und reversibler Software-Lösungen, wurden MRT-Daten eines Patienten mit einem osteochondralen Defekt verwendet, um ein zweischichtiges Implantatdesign zu entwerfen und zu fertigen (Publikation II). Dieses Implantat wies eine adäquate Passgenauigkeit in einem Modell der Läsion in den Femurkondylen, hergestellt per Stereolithografie, auf. Zur chirurgischen Fixierung eines solchen potenziellen Implantats wurde ein individueller Adapter für einen chirurgischen Stößel entwickelt. Das gleiche Materialsystem, prozessierbar mittels Mehrkanaldrucks, erwies sich als kompatibel zum Biodruck von hChon, isoliert aus dem Femurkopf von Hüft-Totalendoprothese-Patienten. Die meisten der Zellen überlebten den Druckprozess und die Kultivierungsbedingungen in monophasigen Scaffolds bestehend aus zellbeladener algMC-Biotinte, sowie in biphasigen Scaffolds mit einer in einer getrennten Schicht verlaufenden oder verwobenen mineralisierten Zone aus CPC. Zellen waren in beiden Ansätzen, als monophasiger oberflächlichen Gelenkknorpel, sowie als kalzifizierte Knorpelschicht, in der Lage, sich zu redifferenzieren; sie zeigten die Expression charakteristischer Matrix-Komponenten und -Gene. Der Kalzium-defizitäre CPC führte zu einer Verminderung der Kalziumionenkonzentration und zu einem initialen Anstieg der Phosphationen im umgebenden Medium. In Gegenwart der CPC-Phase war die Chondrogenese verstärkt (Publikation III). Das Konzept des Kern-Mantel-Biodrucks ermöglichte die örtlich aufgelöste Differenzierung von Zellen (hChon oder hOB), eingebettet in eine Biotinte extrudiert als Mantel-Kompartment, in unmittelbarer Nähe zu einem entsprechenden Faktor-beladenen Depot mit spezifischen Differenzierungsfaktoren. Die Biomaterialtinten für das Kern-Depot wurden durch die Zugabe von Nanoclay(Laponit)-Nanopartikeln hinsichtlich Viskosität und Freisetzungskinetik erfolgreich angepasst. Optische Kohärenztomographie (OCT) wurde als eine zerstörungsfreie Methode zur Beobachtung des koaxialen Strangmusters und der Zellverteilung eingeführt. Die genutzten Tinten erlaubten die Adaption der Freisetzungskurven unterschiedlicher Moleküle wie der Wachstumsfaktoren BMP-2 und TGF-β3. In hChon war die Expression charakteristischer Gene wie Kollagen 2 oder Aggrecan verstärkt, während hOB die für die osteogene Differenzierung typischen Markergene ALP, BGLAP und IBSP exprimierten. Obwohl beide inkorporierten Faktoren auch verstärkende Effekte auf jeweils beide Kompartimente zeigten, konnte der induzierte unerwünschte Effekt der Hypertrophie innerhalb der Knorpelzone sowie die unerwünschte Kollagen Typ 2-Expression innerhalb der Knochenzone erfolgreich verhindert werden. Dies geschah, indem die Faktoren statt homogen über das umgebende Zellkulturmedium mittels Laponit-Tinte und daher freisetzungsverzögernd über die Kern-Depots dargereicht wurden (Publikation IV). Mittels der PCL-Mikrofaser-Gitter-Scaffolds, hergestellt per MEW, mit enger werdenden Fasernetzdichten von 1000 bis 250 µm konnte der E-Modul der algMC-Scaffolds von 10 kPa auf über 50 kPa erhöht werden. Die Zytokompatibilität der hybriden Scaffolds wurden nachgewiesen; auf die Struktur in hybriden algMC-Scaffolds mit einer PCL-Faserdiche von 750 µm reagierten biogedruckte hChon mit einer erhöhten Freisetzung von sulfatierten Glykosaminoglykanen (Publikation V). Schlussfolgerungen: Ein integrierter Ansatz für ein mehrphasiges Implantatdesign, das Einbetten von primären Zellen und die gleichzeitige Anwendung der entsprechenden Wachstumsfaktoren wurde mittels 3D-Extrusions(bio)druck realisiert. Konzepte zum Biodruck von mineralisiertem Knorpel basierend auf algMC und CPC und zur lokalen Faktorengabe in osteochondralen Gewebeersatzstrukturen per Kern-Mantel-Druck wurden entwickelt. Die vorgestellten Ansätze erlauben ein vielseitig adaptierbares, zonales Design, die volle Kontrolle über die örtliche Differenzierung sowie die Reifung der biogedruckten Zellen. Die Vielseitigkeit des modularen Systems ermöglicht zudem das Hinzufügen weiterer Merkmale, was anhand des Einbringens von PCL-Mikrofaser-Scaffolds zur Justierung der mechanischen Eigenschaften der Knorpelzone demonstriert wurde. Eine weitere Option stellt die mechanische Stimulation magnetisch verformbarer algMC-Magnetit-Scaffolds dar. Die wertvollen Erkenntnisse werden als Basis für weitere Anwendungen in vitro sowie in vivo dienen können. All dies kann neue Möglichkeiten und Forschungsrichtungen eröffnen und ist in vielerlei Hinsicht übertragbar auf weitere Materialkombinationen, sowie verschiedene Defekt- und Gewebearten.:Table of Contents List of abbreviations List of figures Legal note 1. Introduction 1.1 The osteochondral interface – function, anatomy and histology 1.2 Pathology of cartilage and osteochondral tissue 1.3 State of the art: treatment of cartilage defects and osteochondral defects 1.4 Tissue engineering for osteochondral regeneration 1.5 Biomedical additive manufacturing and bioprinting 1.6 Hydrogels for bioprinting 1.7 Multi-component and multiphasic strategies to add specific cues and features to bioprinted tissue models 1.8 Additive Manufacturing of patient-specific bone and cartilage substitutes 2. Aims of the thesis List of publications included in the thesis 3. Strategies for biofabrication of volumetric constructs with an individual shape (Publication I) Publication I: Review article 4. Workflow for an MRI-guided, bi-zonal implant design (Publication II) 41 Publication II: Article Publication II: Published supporting information 5. Chondrogenesis in 3D bioprinted constructs and its compatibility with a mineral phase (Publication III) Publication III: Article Publication III: Published supporting information 6. Concept for a zonally defined factor delivery (Publication IV) Publication IV: Article Publication IV: Published supporting information 7. Hybrid bioscaffolds for tailoring mechanical properties of cartilage tissue substitutes (Publication V) Publication V: Article 8. Discussion and outlook References SUMMARY ZUSAMMENFASSUNG Acknowledgements List of other publications (co-)authored by the candidate Scientific congress contributions during PhD phase Journal ranking in Journal Citations Report Appendix I – Erklärungen zur Eröffnung des Promotionsverfahrens Appendix 2 – Erklärung zur Einhaltung gesetzlicher Bestimmunge

    Annual Meeting of the Lunar Exploration Analysis Group : November 1-3, 2016, Columbia, Maryland

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    The meeting goals are three-fold: 1. Integrate the perspectives and interests of the different stakeholders (science, engineering, government, and private sector) to explore common goals of lunar exploration. 2. Use the results of recent and ongoing missions to examine how science enables exploration and exploration enables science. 3. Provide a forum for community updates and input into the issues that affect lunar science and exploration.NASA Lunar Exploration Analysis Group (LEAG) Lunar and Planetary Institute (LPI) Universities Space Research Association (USRA) National Aeronautics and Space Administration (NASA) NASA Solar System Exploration Research Virtual Institute (SSERVI)Organizing Committee, Clive Neal, Convener, University of Notre Dame, Stephen Mackwell, Convener, Universities Space Research Associatio

    2016 Abstracts Student Research Conference

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    GEOLOGIC CONTROLS ON PLIO-PLEISTOCENE DRAINAGE EVOLUTION OF THE KENTUCKY RIVER IN CENTRAL KENTUCKY

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    The primary goal of this project is to develop a relative chronology of events in the geologic history of the Kentucky River, and to consider the geologic controls on those events. This study utilized published geologic and topographic data, as well as field observations and extensive compilation and comparison of digital data, to examine the fluvial record preserved in the Kentucky River valley in central Kentucky. Numerous fluvial features including abandoned paleovalleys, fluvial terraces and deposits, bedrock benches, and relict spillways between adjacent river valleys were identified during the course of the study. The morphology of the modern valley coincides with bedrock lithology and can be used to describe the distribution and preservation of modern and ancient fluvial deposits and features in the study area. Bedrock lithology is the dominant control on valley morphology and on the distribution and preservation of fluvial deposits and features in the study area. Some stream trends are inherited from the late Paleozoic drainage of the Alleghanian orogeny. More recent inheritance of valley morphology has resulted from the erosion of the river from one lithology down into another lithology with differing erosional susceptibility, thus superposing the meander patterns of the overlying valley style onto the underlying lithology. One major drainage reorganization related to a pre-Illinoisan glacial advance disrupted the northward flow of the Old Kentucky River toward the Teays River system and led to organization of the early Ohio River. This greatly reduced the distance to baselevel, and led to abrupt incision and a change in erosional style for the Kentucky River. The successful projection of valley morphologies on the basis of bedrock stratigraphy, the history of erosion suggested by fission track data and the results of this study, as well as soil thickness and development, all argue against the existence of a midto late-Tertiary, low-relief, regional erosional surface. This study instead hypothesizes that the apparent accordance of ridge-top elevations in the study area is a reflection of a fluvially downwasted late Paleozoic depositional surface
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