Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 26 for “"chemical heterogeneity"”.
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Cloud Chemical Heterogeneity and Its Influence on Aqueous sulfur(IV) Oxidation
Differences in chemical composition among cloud and fog drops of diverse sizes were investigated at several locations across the United States. Chemical species including acidity, total sulfur (IV), hydrogen peroxide, formaldehyde, hydroxymethanesulfonate (HMS) and trace metals iron and manganese …
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Chemical heterogeneity of glaciofluvial deposits: Outcrop study and implications for reactive transport
… and dispersion when the spatial scale of the heterogeneity is similar to the scale of the problem. Overall, the outcrop study findings suggest that Pb2+ partition coefficients can be estimated from relatively simple and inexpensive measurements of permeability and dithionite-citrate …
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Exploring chemical communication and chemical heterogeneity in biological systems with mass spectrometry imaging
Chemical heterogeneity is present in all biological systems—whether caused by lipid regulation and expression between individual mammalian single cells or by dynamic chemical communication in bacterial communities. Mass spectrometry imaging (MSI) is an untargeted and unlabeled analytical tool that …
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Geochemical and fluid dynamic investigations into the nature of chemical heterogeneity in the Earth's mantle
… derived peridotites and volcanic rocks are chemical integrals over time, space, and process, which ultimately contain information about the role of convection in the earth's mantle in creating, maintaining, and destroying geochemical heterogeneities. Successful inversion of these integrals …
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Geochemical and fluid dynamic investigations into the nature of chemical heterogeneity in the Earth's mantle
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1992.
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Statistical mechanical theory of structure and miscibility of polymer nanocomposites: Effects of density, filler shape, and chemical heterogeneity
… filler length scale. The effect of nanoparticle chemical heterogeneity was briefly explored by investigation of fillers composed of two tangentially connected spheres with different polymer interfacial attraction strengths or with an added inter-nanoparticle site-site attraction. Such …
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Experimental Constraints on Silicate Perovskite Forming Reactions and Elastic Properties: Geophysical Implications for Chemical Heterogeneity in the Deep Mantle
… to understand the geophysical consequences of chemical heterogeneity in the lower mantle. Calorimetric measurements of the pyrope-majorite garnet solid solution have been made to provide essential thermodynamic data for modeling the formation reactions of both magnesium and calcium silicate …
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Statistical mechanical theory of equilibrium structure and miscibility of polymer nanocomposites: effects of polymer chemical heterogeneity and architecture, and nanoparticle surface corrugation and softness
… attraction strengths. Introducing polymer chemical heterogeneity via the use of AB copolymers offers additional control over the equilibrium structure. Specifically, two types of copolymers are considered – (1) random copolymers (RCP) of disordered sequence and (2) ordered, alternating …
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Effects of Chemical and Structural Heterogeneity on the Tribocorrosion Resistance of Metals in Aqueous Solutions
… In this work, strategies to introduce chemical and structural heterogeneity with controlled length-scale at nanometers were proposed and studied in three metallic systems (i.e., Zr-based, Al-based and Mg-based), in order to enhance their tribocorrosion resistance. In the first study, …
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Roles of surface interaction on Cryptosporidium parvum oocyst transport in subsurface environment
… composition was monitored. Surface polarity and chemical heterogeneity of oocysts surface were characterized by liquid chromatography/nanoelectrospray ionization tandem mass spectrometry (LC-MS/MS), microbial adhesion to hydrocarbon test (MATH), contact angle, and Fourier transform Infrared …
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Design of Heterogeneous Surfaces for Polymer Adsorption
… adsorption of a globular protein with intrinsic chemical heterogeneity was performed to highlight the role of the nature of adsorbates. On a chemically homogeneous surface, unlike flexible homopolymers, the adsorption kinetics of protein were strongly affected by the chemical properties of …
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The heterogeneity and volatile content of Earth’s mantle, magmas and crust
… structure of slow spreading ocean crust and the heterogeneity of Earth’s upper mantle. In Chapter 2, I directly explore the halogen (F and Cl) content of mantle minerals in situ, then use these measurements to assess the halogen content of the upper mantle. In Chapter 3, I investigate the …
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Mantle Heterogeneity Through Mid-Ocean Ridge Basalts
The chemical heterogeneity of Earth's upper mantle is often examined through mid-ocean ridge basalts (MORB), which contest the prevalent assumption of a well-mixed convecting mantle. This dissertation delves into studying mantle heterogeneity from a local to regional scale. Initially, petrological …
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Carbon based secondary metabolites in African savanna woody species in relation to anti-herbivore defense
Chemical defense in African savanna woody species have been inferred from foliar condensed tannin and total phenolic concentrations. However these measures are controversial since condensed tannin chemical heterogeneity compromises its simple quantification and total phenolics, which is a measure …
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Impact of Isotopic Heterogeneity in Shallow Systems on Modeling of Stormflow Generation
A major uncertainty in hydrologic and geochemical modeling of stormflow generation in watersheds has been quantification of the contributions of water and solutes from different sources and hydrologic pathways to streamwater. Isotopic techniques have recently gained widespread acceptance as useful …
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The X-discontinuity: Seismic signatures of a heterogeneous upper mantle
… understood of the distribution of compositional heterogeneity within the Earth. Seismic discontinuities arise from jumps in velocity and density, with global discontinuities manifesting from mineral phase transitions and large-scale changes in composition like the core-mantle boundary. Widely …
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Method development for investigating chemical distributions in the nervous system using mass spectrometry imaging
Chemical heterogeneity is a fundamental property of multicellular organisms. Multiple classes of biomolecules exhibit complex spatial and temporal variations and interactions during different biological processes. One way to investigate this chemical diversity is to visualize biomolecule …
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Microfluidic assembly and packing dynamics of colloidal granules
… methods to control granular size, shape, and chemical heterogeneity. We then investigate the packing dynamics of non-spherical granular media using X-ray micro-computed tomography. Monodisperse spheroidal granules composed of colloid-filled hydrogels are created in a sheath-flow microfluidic …
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Mass spectrometry-based investigations to characterize specific cell types within the brain
Investigations of the chemical content of the brain and its many constitutive cell types yield information regarding normal and abnormal brain function. Frequently, proteomics, peptidomics, and metabolomics experiments survey brain regions and attribute detected species to neurons. However, many …
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Global Relationships Between Intraplate Magmatism and Dynamic Topography
… and lithospheric thicknesses. These geochemical results are compared with tomographic models and a variety of geological and geophysical observations are then combined to determine the degree of dynamic support. This methodology is employed in three regional studies: North Africa, …
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