• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 595
  • 145
  • 85
  • 47
  • 31
  • 19
  • 19
  • 19
  • 19
  • 19
  • 18
  • 16
  • 16
  • 10
  • 8
  • Tagged with
  • 1158
  • 497
  • 212
  • 125
  • 111
  • 105
  • 102
  • 100
  • 98
  • 87
  • 82
  • 76
  • 71
  • 64
  • 51
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Beach sediments : a source of dissolved organic carbon and nitrogen species to the coastal ocean /

Taylor, Kelly Lynne. January 2005 (has links) (PDF)
Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: 47-48)
132

Along-coast variations of Oregon beach-sand compositions produced by the mixing of sediments from multiple sources under a transgressing sea

Clemens, Karen E. 06 January 1987 (has links)
Heavy mineral compositions of sands from Oregon beaches, rivers and sea cliffs have been determined in order to examine the causes of marked along-coast variations in the beach-sand mineralogy. The study area extends southward from the Columbia River to the Coquille River in southern Oregon. The heavy-mineral compositions were determined by standard microscopic identification with additional verification by X-ray diffraction analyses. Initially the beach-sand samples were collected as single grab samples from the mid-beachface, but significant selective sorting of the important heavy minerals prevented reasonable interpretations of the results. Factor analysis of multiple samples from the same beach yielded distinct factors which correspond with known mineral sorting patterns. The effects of local sorting were reduced by the subsequent use of large composite samples, permitting interpretations of along-coast variations in sand compositions. Four principal beach-sand sources are identified by factor analysis: the Columbia River on the north, a Coastal Range volcanic source, sands from the Umpqua River on the south-Oregon coast, and a metamorphic source from the Klamath Mountains of southern Oregon and northern California. The end members identified by factor analysis of the beach sands correspond closely to river-source compositions, the proportions in a specific beach-sand sample depending on its north to south location with respect to those sources. During lowered sea levels of the Late Pleistocene, the Columbia River supplied sand which was dispersed both to the north and south, its content decreasing southward as it mixed with sands from other sources. The distributions of minerals originating in the Klamath Mountains indicate that the net littoral drift was to the north during lowered sea levels. With a rise in sea level the longshore movement of sand was interrupted by headlands such that the Columbia River presently supplies beach sand southward only to the first headland, Tillamook Head. At that headland there is a marked change in mineralogy and in grain rounding with angular, recently-supplied sands to the north and rounded sands to the south. The results of this study indicate that the present-day central Oregon coast Consists of a series of beaches separated by headlands, the beach-sand compositions in part being relict, reflecting the along-coast mixing at lower sea levels and subsequent isolation by onshore migration of the beaches under the Holocene sea-level transgression. This pattern of relict compositions has been modified during the past several thousand years by some addition of sand to the beaches by sea-cliff erosion and contributions from the rivers draining the nearby Coastal Range. / Graduation date: 1987
133

Hydrodynamic dispersion in suspensions

Cunha, Francisco Ricardo da January 1995 (has links)
No description available.
134

Effects of multiple stresses on coral reef communities

Nugues, Maggy January 2000 (has links)
No description available.
135

Geology and palaeontology of the Telychian (Silurian), Reservoir Formation of the North Esk inlier, near Edinburgh, Scotland

Bull, Elizabeth Eleanor January 1995 (has links)
No description available.
136

Laboratory investigations of geological fluid flows

Hallworth, Mark A. January 1998 (has links)
No description available.
137

Depositional environment of the Eskridge shale (lower Permian)

Pecchioni, Loretta Lucia January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
138

Controls on the spatial and temporal evolution and distribution of depositional components in the Paleocene-Lower Eocene Succession, Kurdistan Region-Iraq

Zebari, Bahroz Gh. A. January 2018 (has links)
No description available.
139

Confocal microscopy study of colloidal sedimentation and crystallization

Beckham, Richard Edward 15 May 2009 (has links)
Colloidal crystallization in sedimenting systems is an incompletely understood process, where the influence of interparticle forces on the three-dimensional (3-D) microstructure remains to be fully elucidated. This dissertation outlines work that is intended to improve our knowledge of this subject by studying sedimentation equilibrium and phase behavior for electrostatically repulsive systems, as well as the interfacial crystallization of attractive depletion systems. Towards this end, several analytical and experimental tools have been developed to explore the thermodynamic behavior of these systems. For example, the experimental challenges necessitated the development and implementation of the following in this work: (1) core/shell silica particles incorporating molecular fluorophores or semiconductor nanocrystals; (2) modification of silica particle surfaces; (3) the design of specialized sedimentation cells; and (4) the development of a novel fluorescent intensity-based approach to quantifying colloidal sediments. Analysis of the experimental data required the use of the following tools: (1) location of particle centers from images; (2) deconvolution of intensity profiles using a novel Monte Carlo-type algorithm; and (3) prediction of colloidal phase diagrams using perturbation theory. On the basis of this work’s experimental and simulation data, it is concluded that competing orientations of crystal grains may suppress crystallization at grain boundaries, resulting in a non-uniform depth of the fluid/solid transition. Also, it was demonstrated that the grain size in depletion crystals formed from quantum dot-coated silica particles can be increased by localized annealing with the confocal microscope’s laser. Additional findings include the ability of the intensity-based approach to measure interparticle forces in colloidal sediments, as well as the inability to use perturbation theory to predict two-dimensional colloidal fluid/solid transitions. While significant progress has been achieved, work on 3-D imaging of colloidal depletion crystals in a refractive index-match medium is ongoing. This work improves our understanding of 3-D colloidal crystallization at interfaces, as well as provides new tools for future research. Also, this work demonstrates a potential route for zone refining of colloidal crystals, a technique that may be important in the search for low-defect 3-D arrays that can be used as templates for photonic bandgap materials.
140

The Seismic Stratigraphy and Sedimentation along the Ninetyeast Ridge

Eisin, Amy Elizabeth 2009 August 1900 (has links)
The Ninetyeast Ridge (NER) is a ~5000 km-long aseismic volcanic ridge trending NS in the eastern Indian Ocean basin. It is widely accepted that NER formed from the trace of a single hotspot as the Indian plate moved northward during the Late Cretaceous and Early Cenozoic due to the linear age progression from 43 Myo at the southern end to 77 Myo at the northern end. What is not fully understood is the geologic history of the ridge since its formation. This study examines the stratigraphy and sediment thickness on the ridge using new seismic data to describe the sedimentary history of NER. More than 3700 km of 2D multichannel seismic reflection profiles were collected along NER at seven sites between 5.5 degrees N and 26.1 degrees S during cruise KNOX06RR of the R/V Roger Revelle in 2007. Scientific objectives were to obtain site survey data for proposed drilling and to understand the sedimentary layers, sediment distribution, and geologic history of NER. Seismic survey sites were chosen primarily based on proximity to existing Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill holes (Sites 758, 216, 214, and 253) for interpretation and correlation with existing lithologic data. Seismic data were processed (filtered, stacked, and time-migrated) and interpreted using standard seismic stratigraphy principles. Three major horizons were interpreted, correlated with those previously recognized at the DSDP and ODP sites, and traced throughout the seismic data. Seismic data were categorized into three units based on distinct acoustic properties including changes in reflector amplitude, wavelength, continuity, and geometry. Seismic Unit I comprises a succession of pelagic sediments and sedimentary rock draped over Seismic Unit II, which consists of pelagic carbonates mixed with volcaniclastics. Seismic Unit III is volcanic basement. Sediment layer thicknesses and distribution were mapped at each site, and bathymetric data were correlated with seismic data to interpret geologic features. Seismic and core data indicate a common sedimentary history at each site: volcaniclastic-rich sediments deposited during or shortly after ridge formation topped by a thick drape of pelagic sediments. This history likely happened in three stages over the last ~77 My: 1) the initial subaerial or submarine emplacement of the volcanic ridge, 2) the deposition of shallow water sediments and volcaniclastics, and finally 3) the subsidence of the ridge followed by deep water pelagic sediment deposition.

Page generated in 0.1216 seconds