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Scanning Probe Microscopy Studies Of Petroleum Chemistry: Substrate-Dependent Catalytic Properties Of Mos2 And Automating Scanning Probe Microscopy With Machine Learning, Steven Arias

Doctoral Dissertations

With the growth of the population, society’s energy demands are mostly reliant on petroleum products that come from the refining of crude oil. Most of these refining reactions have been developed through averaging spectroscopic techniques, but scientists do not know exactly what is happening in these processes at the nano and atomic levels. This information is crucial when designing an efficient refining process that produces petroleum products that emit fewer harmful gases when combusting. Scanning probe microscopy techniques have become a powerful tool to look into the chemical structures found in petroleum products, to understand catalytic reactions in refining processes, …

Nitrogen Dynamics And Retention In The River Network Of A Tropical Forest, Luquillo Mountains, Puerto Rico, Richard Brereton

Doctoral Dissertations

This dissertation identifies gaps in the scientific understanding of nutrient cycling, particularly nitrogen (N) cycling, in streams and riparian zones of tropical montane forests, and addresses several of those gaps with original field-based research using study watersheds in the Luquillo Mountains of Puerto Rico as the model system. The Luquillo Mountains have features typical of mature montane tropical forests, such as high background N concentrations in streams and groundwater relative to streams in other biomes. As a USDA Forest Service Experimental Forest, the Luquillo Mountains are accessible to researchers and have abundant monitoring and experimental datasets from which to build …

Nmr T₁ Studies Of Colloidal Unimolecular Polymer (Cup) Surface Water, Yousef Abobaker Dawib

Doctoral Dissertations

"This dissertation is subdivided into three topics: Experimental study of colloidal unimolecular polymer (CUP) hydration; probing of polymer chain dynamics by ¹³C solid state NMR technique; and the anticorrosive effect of 5-mercapto-1, 3, 4-thiadiazole-2(3H)-thione (MTT) derivatives.

The states of water in colloidal unimolecular polymer system were investigated by low field proton NMR. Bound and free water fractions were determined using spin-lattice relaxation measurements. A model equation was used to analyze the inversion recovery data.

The proton cross polarization and the pulse sequence for total spinning sideband suppression CP-TOSS NMR method were developed to determine the chain mobility of polymers …

Design, Synthesis And Biological Evaluation Of Small Molecule Inhibitors Of The Hedgehog Signaling Pathway, Upasana Banerjee

Doctoral Dissertations

The Hedgehog (Hh) signaling is an important embryonic developmental pathway normally responsible for tissue growth, differentiation and patterning. However, aberrant activity of this signaling cascade has been implicated in several types of cancer. Therefore, inhibition of the dysregulated pathway is a promising therapeutic target for treating Hh-dependent malignancies such as basal cell carcinoma (BCC) and medulloblastoma (MB). Previous studies resulted in the FDA approval of Vismodegib, a small molecule inhibitor of the Hh pathway, for the treatment of advanced BCC. Similarly, several other small molecule Hh antagonists have progressed into clinical trials. Moreover, several components within the Hh pathway have …

First-Principles Investigations Of Iron-Based Alloys And Their Properties, Krista Renee Limmer

Doctoral Dissertations

"Fundamental understanding of the complex interactions governing structure-property relationships in iron-based alloys is necessary to advance ferrous metallurgy. Two key components of alloy design are carbide formation and stabilization and controlling the active deformation mechanism. Following a first-principles methodology, understanding on the electronic level of these components has been gained for predictive modeling of alloys.

Transition metal carbides have long played an important role in alloy design, though the complexity of their interactions with the ferrous matrix is not well understood. Bulk, surface, and interface properties of vanadium carbide, VC_x, were calculated to provide insight for the carbide …

The Versatility Of Ether-Bridged Cycloadducts Towards The Synthesis Of Complex Natural Products, Harold Deshaun Cooper

Doctoral Dissertations

The presence of a heterocyclic moiety can be observed in many of today’s bioactive natural products. One of the most commonly observed is furan, an aromatic five-membered ring containing an oxygen atom. Furan is a simple compound, yet versatile enough to be used as a synthetic synthon leading to complex structures such as the antioxidant Phelligridin G and the antibacterial agent Platensimycin. In the former, it is spiro-fused to the five-membered carbocycle of the 6-5-5 tricyclic domain while in the latter it makes up the ether-bridged cycloadduct of the hydrophobic cage. Conventionally, furan can undergo cycloadditions in the presence of …

Membrane Properties Of Intact Rock Cores Of Burlington Limestone, Jefferson Dolomite, Darrington Phyllite, And Low Permeability Concrete, Megan Hart

Doctoral Dissertations

"A number of laboratory studies have shown that clays exhibit membrane properties. However, little research has been performed on lithologies outside of pure clays. Recently, research focusing on mixed sand and clay membrane properties for engineering applications was performed. Still, literature only suggests the possibilities of membrane properties, osmotic or reverse-osmotic, associated with other naturally occurring 'tight' rock types. Therefore, the objectives of this research was to perform a series of hyperfiltration experiments using actual rock discs of Quarry Ridge Jefferson Dolomite, Darrington Phyllite, Lower Burlington Limestone, and low permeability concrete to determine if tight lithologies can function as membranes"--Abstract, …

Snow And Ice Chemistry Study Of The Greenland Ice Sheet, Qinzhao Yang

Doctoral Dissertations

The Greenland ice sheet preserves high resolution records of environmental and climate change spanning seasons to hundreds and thousands of years. In this study, we utilize major chemical species measurements of surface snowpit samples and ice cores collected at GISP2, 20D, Mount Logan, and Sentik Glacier to investigate major chemical species spatial distribution, temporal variations, and possible sources for the major chemical species in these ice cores.

A two-sided t-distribution test (a = 0.05) was applied for the study of major chemical species spatial distribution over a portion of central Greenland. The results suggest that concentrations of major chemical species …

The Hot-Atom Chemistry Of Sulfur(35) Produced By The Chlorine-35(Neutron,Proton)Sulfur-35 Reaction In Mixed Crystals Of Potassium Chloride And Potassium Bromide, John Robert Hobbs

Doctoral Dissertations

No abstract provided.