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Articles 1 - 8 of 8
Full-Text Articles in Physical Sciences and Mathematics
Floodplain Forests Vegetation Dynamics Driven By Water Deficits Across Scales, Nga Thanh Nguyen
Floodplain Forests Vegetation Dynamics Driven By Water Deficits Across Scales, Nga Thanh Nguyen
LSU Doctoral Dissertations
Restoration of floodplain ecosystems relies on identifying the most crucial hydrologic process which has been altered by human and climate. Flooding is a well-known dominant hydrologic process for floodplain ecosystems, but surprisingly little is known about drought's role in structuring ecosystems. In addition, several issues remained uncertain, such as the nature of drought within floodplains and the sensitivity of floodplain species-specific growth to climate. These gaps of understanding have in common in missing observations of mechanistic pathways of vegetation response to water deficits at multiple scales in time and space.Generally, this research contributed to floodplain management by expanding our understanding …
Palynology And Paleoclimatology Of The Chicxulub Impact Crater In The Early Paleogene, Vann Smith
Palynology And Paleoclimatology Of The Chicxulub Impact Crater In The Early Paleogene, Vann Smith
LSU Doctoral Dissertations
At the end of the Cretaceous Period, a large bolide impacted the Earth and formed the Chicxulub impact crater in the Yucatán Peninsula, Mexico. In 2016, International Ocean Discovery Program (IODP) Expedition 364 Site M0077 drilled into the buried peak ring of the crater, recovering a marine Paleocene to early Eocene post-impact section deposited on top of the impact breccia. Palynological analysis of 195 samples from the post-impact section has yielded the first pre-Holocene vegetational record from inside the Chicxulub impact crater and the first palynological record of the recovery of life following the end-Cretaceous mass extinction from inside the …
Computer Simulations Of Diffusional Isotope Effects And Dynamical Properties Of Silicate Melts, Haiyang Luo
Computer Simulations Of Diffusional Isotope Effects And Dynamical Properties Of Silicate Melts, Haiyang Luo
LSU Doctoral Dissertations
Silicate melts have served as transport agents in the chemical and thermal evolution of Earth. Diffusional isotope effect in silicate melts is the key to interpret isotope variations in lots of geological samples. Isotopic mass dependence of diffusion is commonly expressed as (Di/Dj)=(mj/mi)^β, where Di and Dj are diffusion coefficients of two isotopes whose masses are mi and mj. However, how the dimensionless empirical parameter β depends on temperature, pressure, and composition remains poorly constrained. Viscosity and electrical conductivity are two fundamental dynamical properties of silicate melts needed to constrain melt distribution in Earth's interior but remain unclear for most …
Simulation Of Compound Flood Events In Low-Gradient Coastal Watershed, Felix Luis Santiago-Collazo
Simulation Of Compound Flood Events In Low-Gradient Coastal Watershed, Felix Luis Santiago-Collazo
LSU Doctoral Dissertations
Low-gradient coastal watersheds are susceptible to flooding caused by various flows such as rainfall, tides, and storm surge. Compound flooding occurs when at least two of these mechanisms happen simultaneously or in close succession. Different inundation models, observed data, and/or a combination of these are coupled through varying techniques involving one-way, loosely, tightly, or fully coupled approaches to assess compound flooding. This study presents a one-dimensional (1-D), fully coupled compound inundation model based on the Shallow Water equations. This model approach simultaneously simulates the free water surface variations in the ocean domain (i.e., tide and storm surge modeling), rainfall-runoff in …
Characterizing The Northern Hemisphere Circumpolar Vortex Through Space And Time, Nazla Bushra
Characterizing The Northern Hemisphere Circumpolar Vortex Through Space And Time, Nazla Bushra
LSU Doctoral Dissertations
This hemispheric-scale, steering atmospheric circulation represented by the circumpolar vortices (CPVs) are the middle- and upper-tropospheric wind belts circumnavigating the poles. Variability in the CPV area, shape, and position are important topics in geoenvironmental sciences because of the many links to environmental features. However, a means of characterizing the CPV has remained elusive. The goal of this research is to (i) identify the Northern Hemisphere CPV (NHCPV) and its morphometric characteristics, (ii) understand the daily characteristics of NHCPV area and circularity over time, (iii) identify and analyze spatiotemporal variability in the NHCPV’s centroid, and (iv) analyze how CPV features relate …
Modeling Hydraulic Fracturing Initiation And Propagation In Porous Rock Formationsl, Chang Huang
Modeling Hydraulic Fracturing Initiation And Propagation In Porous Rock Formationsl, Chang Huang
LSU Doctoral Dissertations
Hydraulic fracturing has long been introduced to the oil and gas industry since the early nineteenth century for both reservoir characterization and reservoir stimulation. Despite the progress made in the last two decades, many challenges still have not been tackled regarding not only the propagation problem but also the initiation problem due to its complexity. The dissertation is divided into two stages, i.e., before and after fracture initiation. The first stage of the research aimed at improving the accuracy in solving the poro-mechanical response of wellbore during fluid injection before a tensile fracture occurs, which is crucial to determine the …
Hydro-Morphodynamics Of Sandy Coastal Embayments, Shamim Murshid
Hydro-Morphodynamics Of Sandy Coastal Embayments, Shamim Murshid
LSU Doctoral Dissertations
This dissertation investigates the hydro-morphodynamics of two major components of a sandy coastal environment: tidal inlets and embayment shorelines. In the first study, I focused on the evolution of inlet geometry by compiling and analyzing a database with 226 inlets worldwide with a special attention given to their width to depth ratio (or aspect ratio). I found that the aspect ratio has a weak dependency on tidal range and wave height, and they lie in different ranges for three types of tidal inlets: engineered, natural single-thread, and natural compound. I also developed a 2D hydro-morphodynamic model of an idealized barrier-inlet …
Application Of Compound-Specific Stable Isotopes And Molecular Biomarkers To Paleoclimatic And Paleoecological Reconstructions, Mingqiu Hou
LSU Doctoral Dissertations
Compound-specific stable isotope analysis and biomarker-based paleothermometry have been increasingly applied to for paleoclimate and paleoecology studies. The first project aims to reconstruct the paleoclimate in the Qaidam Basin during the last glacial period. Qaidam Basin in the Northern Tibetan Plateau is a critical eolian factory located at a unique geographic location that links the Westerlies and the Asian summer monsoons. However, how the interactions of two climatic systems influence the paleohydrology that in turn impacts the eolian production in the Qaidam Basin has been seldom explored. Our compound-specific hydrogen isotope and UK 37 temperature data found that the …