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Articles 1 - 9 of 9
Full-Text Articles in Physical Sciences and Mathematics
Optical Spectroscopy And The Contruction Of An Optimal Wannier Basis With Application To The Development Of Ab Initio Models, Robert Gerard Van Wesep
Optical Spectroscopy And The Contruction Of An Optimal Wannier Basis With Application To The Development Of Ab Initio Models, Robert Gerard Van Wesep
Doctoral Dissertations
Understanding the role of local orbital degrees of freedom in the behavior of solid state systems has long been understood as a key to unraveling the mysteries presented by complex transition metal compounds. A general approach to the many-body problem is density functional theory (DFT) and its time-dependent extension (TDDFT), which provide a realistic representation of the material-dependent symmetry and chemistry of a compound. Calculation of quantities in (TD)DFT are most often performed using the basis of Bloch states, which is not natural for investigating local degrees of freedom. The Wannier basis provides localized orbitals that retain all of the …
Study Of Charge Transport Mechanism In Microbial Nanowires, Ramesh Adhikari
Study Of Charge Transport Mechanism In Microbial Nanowires, Ramesh Adhikari
Doctoral Dissertations
Conductivity of an individual proteinaceous filaments, called pili or microbial nanowires, produced by wild type Geobacter sulfurreducens was measured using a low-noise electrical transport technique. It was shown that the conductivity is diminished if aromatic amino acid residues are removed from the pili. It was demonstrated that the conductivity of G. sulfurreducens pili is similar to that of synthetic organic polymers and is related to the respiration rate of the bacteria. Conductivity measurements were performed on microbial nanowires produced by other species of Geobacter with a different aromatic amino acid distribution along the wire. Also, measurements on a mutated pili …
X-Ray Characterization Of Mesophases And Phase Transitions Of Dna Analogues In Solutions, Mustafa Selcuk Yasar
X-Ray Characterization Of Mesophases And Phase Transitions Of Dna Analogues In Solutions, Mustafa Selcuk Yasar
Doctoral Dissertations
We think of DNA as double-stranded helices (duplex), but the polymer exists in many conformations. Several triplex and quadruplex DNA structures can be formed in laboratory settings and exist in nature. This thesis first provides a brief description of the nature of the order in arrays of duplex DNA under biologically relevant molecular crowding conditions. Then we compare the duplex DNA mesophases with the corresponding liquid crystalline phase behavior of the triplex and quadruplex DNA analogues. In particular, we focus on G-quadruplexes. Observed in the folds of guanine-rich oligonucleotides, G-quadruplex structures are based on G-quartets formed by hydrogen bonding and …
Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang
Evaporation Induced Self-Assembly And Characterization Of Nanoparticulate Films: A New Route To Bulk Heterojunctions, Yipeng Yang
Doctoral Dissertations
Polymer-based semiconducting materials are promising candidates for large-scale, low-cost photovoltaic devices. To date, the efficiency of these devices has been low in part because of the challenge of optimizing molecular packing while also obtaining a bicontinuous structure with a characteristic length comparable to the exciton diffusion length of 10 to 20 nm. In this dissertation we developed an innovative evaporation-induced nanoparticle self-assembly technique, which could be an effective approach to fabricate uniform, densely packed, smooth thin films with cm-scale area from home-made P3HT nanoparticles. Unlike the previous reports of nanoparticle-based film formation, we use a mixture of two solvents so …
Kinetics And Dynamics Of Electrophoretic Translocation Of Polyelectrolytes Through Nanopores, Harshwardhan Katkar
Kinetics And Dynamics Of Electrophoretic Translocation Of Polyelectrolytes Through Nanopores, Harshwardhan Katkar
Doctoral Dissertations
The idea of sequencing a DNA based on single-file translocation of the DNA through nanopores under the action of an electric field has received much attention over the past two decades due to the societal need for low cost and high-throughput sequencing. However, due to the high speed of translocation, interrogating individual bases with an acceptable signal to noise ratio as they traverse the pore has been a major problem. Experimental facts on this phenomenon are rich and the associated phenomenology is yet to be fully understood. This thesis focuses on understanding the underlying principles of polymer translocation, with an …
Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem
Doctoral Dissertations
Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …
Characterizing Local Order And Physical Properties Of Rare Earth Complex Oxides, Thomas Jacob Shamblin
Characterizing Local Order And Physical Properties Of Rare Earth Complex Oxides, Thomas Jacob Shamblin
Doctoral Dissertations
With more than 500 compositions, materials possessing the pyrochlore structure have a myriad of technological applications and physical phenomena. Three of the most noteworthy properties are the structure’s ability to resist amorphization making it a possible host matrix for spent nuclear fuel, its exotic magnetic properties arising from geometric frustration, and fast ionic conductivity for solid-oxide fuel cell applications. This work focuses on these three aspects of the pyrochlore’s many potential uses. Structural characterization revealed that pyrochlore-type oxides have a tendency to disorder from a high symmetry cubic structure to a lower symmetry orthorhombic arrangement in response to a variety …
Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins
Morphological And Material Effects In Van Der Waals Interactions, Jaime C. Hopkins
Doctoral Dissertations
Van der Waals (vdW) interactions influence a variety of mesoscale phenomena, such as surface adhesion, friction, and colloid stability, and play increasingly important roles as science seeks to design systems on increasingly smaller length scales. Using the full Lifshitz continuum formulation, this thesis investigates the effects of system materials, shapes, and configurations and presents open-source software to accurately calculate vdW interactions. In the Lifshitz formulation, the microscopic composition of a material is represented by its bulk dielectric response. Small changes in a dielectric response can result in substantial variations in the strength of vdW interactions. However, the relationship between these …
Voltage Driven Translocation Of Polyelectrolytes Through Nanopores, Byoung-Jin Jeon
Voltage Driven Translocation Of Polyelectrolytes Through Nanopores, Byoung-Jin Jeon
Doctoral Dissertations
Recently, translocations of polyelectrolyte molecules through membrane channel protein pores or solid-state nanopores have been actively studied. Although the polymer translocation researches emerged mainly due to technological demands in terms of genome sequencing, the detailed physics of the single molecule transport through a narrow channel remains fully understood. To obtain further understanding of common features of the translocation process, this thesis focuses on the effects of salt concentration, pore-polymer electrostatic interactions, and externally applied electric field on the voltage-driven polymer translocations. The study is carried out by performing a series of systematically designed experiments using alpha-hemolysin (αHL) protein pore to …