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Articles 2671 - 2700 of 3529
Full-Text Articles in Physical Sciences and Mathematics
Polarization Dependent Two-Photon Absorption Properties Of Chiral Molecules, Carlos Toro
Polarization Dependent Two-Photon Absorption Properties Of Chiral Molecules, Carlos Toro
Electronic Theses and Dissertations
Molecules that are non-superimposable on their mirror image are named chiral or optically active compound. Over the years, molecular chirality has played an essential role in the understanding of fundamental aspects associated the origin of life, drug and food technologies and, asymmetric catalysis, among others. Moreover, most of the groundbreaking discoveries and advances made in this field have happened due to the development of spectroscopic techniques based on the natural asymmetry of the enantiomers and their ability to preferentially absorb right or left polarized light. For instance, circular dichroism (CD), which measures the difference in absorption between these two states …
Development Of Optical Coherence Tomography For Tissue Diagnostics, Panomsak Meemon
Development Of Optical Coherence Tomography For Tissue Diagnostics, Panomsak Meemon
Electronic Theses and Dissertations
Microvasculature can be found in almost every part of the human body, including the internal organs. Importantly, abnormal changes in microvasculature are usually related to pathological development of the tissue cells. Monitoring of changes in blood flow properties in microvasculature, therefore, provides useful diagnostic information about pathological conditions in biological tissues as exemplified in glaucoma, diabetes, age related macular degeneration, port wine stains, burn-depth, and potentially skin cancer. However, the capillary network is typically only one cell in wall thickness with 5 to 10 microns in diameter and located in the dermis region of skin. Therefore, a non-invasive flow imaging …
Supported Mono And Bimetallic Platinum And Iron Nanoparticles Electronic, Structural, Catalytic, And Vibrational Properties, Jason Robert Croy
Supported Mono And Bimetallic Platinum And Iron Nanoparticles Electronic, Structural, Catalytic, And Vibrational Properties, Jason Robert Croy
Electronic Theses and Dissertations
Catalysis technologies are among the most important in the modern world. They are instrumental in the realization of a variety of products and processes including chemicals, polymers, foods, pharmaceuticals, fuels, and fuel cells. As such, interest in the catalysts that drive these processes is ongoing, and basic research has led to significant advances in the field, including the production of more environmentally friendly catalysts that can be tuned at the molecular/atomic level. However, there are many factors which influence the performance of a catalyst and many unanswered questions still remain. The first part of this work is concerned with the …
Plasmon Enhanced Near-Field Interactions In Surface Coupled Nanoparticle Arrays For Integrated Nanophotonic Devices, Amitabh Ghoshal
Plasmon Enhanced Near-Field Interactions In Surface Coupled Nanoparticle Arrays For Integrated Nanophotonic Devices, Amitabh Ghoshal
Electronic Theses and Dissertations
The current thrust towards developing silicon compatible integrated nanophotonic devices is driven by need to overcome critical challenges in electronic circuit technology related to information bandwidth and thermal management. Surface plasmon nanophotonics represents a hybrid technology at the interface of optics and electronics that could address several of the existing challenges. Surface plasmons are electronic charge density waves that can occur at a metal-dielectric interface at optical and infrared frequencies. Numerous plasmon based integrated optical devices such as waveguides, splitters, resonators and multimode interference devices have been developed, however no standard integrated device for coupling light into nanoscale optical circuits …
Species Composition And Spatiotemporal Pattern Of The Seed Bank And Vegetation In Native And Degraded Florida Rosemary Scrub, Jennifer J. Navarra
Species Composition And Spatiotemporal Pattern Of The Seed Bank And Vegetation In Native And Degraded Florida Rosemary Scrub, Jennifer J. Navarra
Electronic Theses and Dissertations
The soil seed bank plays a dynamic role in the regeneration of plant communities after natural and anthropogenic disturbance. In this thesis, I addressed how disturbances influence the vegetation and seed bank of Florida rosemary scrub. In Chapter One I evaluated changes in species composition and spatiotemporal pattern of the vegetation and seed bank along a gradient of disturbance. During the summers and winters of 2007-2009 percent ground cover and seed bank species composition were assessed among replicates of three vegetation types subjected to minimal, moderate, and extreme anthropogenic disturbance (native rosemary scrub, degraded scrub, and agriculturally improved pasture, respectively). …
New Laser Technologies Analysis Of Quantum Dot And Lithographic Laser Diodes, Abdullah Demir
New Laser Technologies Analysis Of Quantum Dot And Lithographic Laser Diodes, Abdullah Demir
Electronic Theses and Dissertations
The first part of this dissertation presents a comprehensive study of quantum dot (QD) lasers threshold characteristics. The threshold temperature dependence of a QD laser diode is studied in different limits of p-doping, hole level spacing and inhomogeneous broadening. Theoretical analysis shows that the threshold current of a QD laser in the limit of uniform QDs is not temperature independent and actually more temperature sensitive than the quantum well laser. The results also explain the experimental trends of negative characteristic temperature observed in QD lasers and clarify how the carrier distribution mechanisms inside and among the QDs affect the threshold …
Using Landscape Genetics To Assess Population Connectivity In A Habitat Generalist, Tyler Duncan Hether
Using Landscape Genetics To Assess Population Connectivity In A Habitat Generalist, Tyler Duncan Hether
Electronic Theses and Dissertations
Understanding the nature of genetic variation in natural populations is an underlying theme of population genetics. In recent years population genetics has benefited from the incorporation of landscape and environmental data into pre-existing models of isolation by distance (IBD) to elucidate features influencing spatial genetic variation. Many of these landscape genetics studies have focused on populations separated by discrete barriers (e.g., mountain ridges) or species with specific habitat requirements (i.e., habitat specialists). One difficulty in using a landscape genetics approach for taxa with less stringent habitat requirements (i.e., generalists) is the lack of obvious barriers to gene flow and preference …
Novel Improvements On The Analytical Chemistry Of Polycyclic Aromatic Hydrocarbons And Their Metabolites, Wang Huiyong
Novel Improvements On The Analytical Chemistry Of Polycyclic Aromatic Hydrocarbons And Their Metabolites, Wang Huiyong
Electronic Theses and Dissertations
Polycyclic aromatic hydrocarbons (PAH) are important environmental pollutants originating from a wide variety of natural and anthropogenic sources. Because many of them are highly suspect as etiological agents in human cancer, chemical analysis of PAH is of great environmental and toxicological importance. Current methodology for PAH follows the classical pattern of sample preparation and chromatographic analysis. Sample preparation preconcentrates PAH, simplifies matrix composition, and facilitates analytical resolution in the chromatographic column. Among the several approaches that exist to pre-concentrate PAH from water samples, the Environmental Protection Agency (EPA) recommends the use of solid-phase extraction (SPE). High-performance liquid chromatography (HPLC) and …
Application Of Antenna Synthesis And Digital Signal Processing Techniques For Active Millimeter-Wave Imaging Systems, Wilson Ariel Caba
Application Of Antenna Synthesis And Digital Signal Processing Techniques For Active Millimeter-Wave Imaging Systems, Wilson Ariel Caba
Electronic Theses and Dissertations
Millimeter-wave imaging has gathered attention in recent years for its ability to penetrate clothing, thin layers of soils, and certain construction materials. However, image quality remains a challenge that needs to be addressed. One way of improving image quality is by increasing the dimensions of the collecting aperture. A sparse array can be used to synthesize a larger aperture with a limited set of relatively small detectors. In this research we design, build, and test a test-bed having an active source at 94 GHz and an array of coherent detectors, mounted on arms that extend radially on a rotary table. …
Symmetry In The Dissociative Recombination Of Polyatomic Ions And In Ultra-Cold Few Body Collisions, Nicolas Douguet
Symmetry In The Dissociative Recombination Of Polyatomic Ions And In Ultra-Cold Few Body Collisions, Nicolas Douguet
Electronic Theses and Dissertations
We discuss the role of symmetries in the dissociative recombinations (DR) of three polyatomic ions, namely the linear HCO+ (formyl) ion and the two highly symmetric H+3 and H3O+ (hydronium) molecular ions. Regarding the HCO+ ion, we apply a quantum mechanical treatment using the Multi-channel Quantum Defect Theory (MQDT) formalism to describe the ion-electron scattering process. Our study takes into account the Renner-Teller effect in order to model the non Born-Oppenheimer vibronic coupling in linear polyatomic ions. The coupling has shown to represent the main mechanism responsible for electronic capturing in highly excited Rydberg states associated with excited vibrational levels …
Experimental And Theoretical Study Of The Optical Properties Of Semiconductor Quantum Dots, Gero Nootz
Experimental And Theoretical Study Of The Optical Properties Of Semiconductor Quantum Dots, Gero Nootz
Electronic Theses and Dissertations
The aim of this dissertation is to gain a better understanding of the unique electronic structure of lead salt quantum dots (QDs) and its influences on the nonlinear optical (NLO) properties as well as the time dynamics of the photogenerated charge carriers. A variety of optical techniques such as Z-scan, two-photon excited fluorescence and time-resolved pump probe spectroscopy are used to measure these properties. The one-photon as well as the degenerate and nondegenerate two-photon absorption (2PA) spectra are measured and the electronic wave functions from a four-band envelope function formalism are used to model the results. We observe local maxima …
Laboratory Studies To Field Evaluation : Remediation Of Polychlorinated Biphenyl Contaminated Painted Surfaces Through The Use Of Activated Metal Treatment Systems, Erin Kristen Saitta
Laboratory Studies To Field Evaluation : Remediation Of Polychlorinated Biphenyl Contaminated Painted Surfaces Through The Use Of Activated Metal Treatment Systems, Erin Kristen Saitta
Electronic Theses and Dissertations
Polychlorinated Biphenyls (PCBs) are a group of 209 congeners that are regulated under the Toxic Substance Control Act. They enter the environment as a result of industrial processes and can travel long distances. PCBs are environmentally persistent and bioaccumulate in animal populations. Painted surfaces are a common point source for PCBs and there are few options for remediating structures painted with PCB-contaminated paint. Removal of the paint can often spread contamination and disposing or burning of large structures is expensive. Experiments employing reductive dehalogenation through the use of a bimetal have shown that PCBs can be degraded in mild laboratory …
The Fabrication Of Polymer-Derived Sicn/Sibcn Ceramic Nanostructures And Investigation Of Their Structure-Property Relationship, Sourangsu Sarkar
The Fabrication Of Polymer-Derived Sicn/Sibcn Ceramic Nanostructures And Investigation Of Their Structure-Property Relationship, Sourangsu Sarkar
Electronic Theses and Dissertations
Polymer-derived Ceramics (PDCs) represent a unique class of high-temperature stable materials synthesized directly by the thermal decomposition of polymers. This research first focuses on the fabrication of high temperature stable siliconcarbonitride (SiCN) fibers by electrospinning for ceramic matrix composite (CMC) applications. Ceraset™ VL20, a commercially available liquid cyclosilazane, was functionalized with aluminum sec-butoxide in order to be electrospinnable. The surface morphology of the electrospun fibers was investigated using the fibers produced from solvents. The electrospun fibers produced from the chloroform/N,N-dimethylformamide solutions had hierarchical structures that led to superhydrophobic surfaces. A “dry skin” model was proposed to explain the formation of …
Modeling And Design Of A Photonic Crystal Chip Hosting A Quantum Network Made Of Single Spins In Quantum Dots That Interact Via Single Photons, Hubert P. Seigneur
Modeling And Design Of A Photonic Crystal Chip Hosting A Quantum Network Made Of Single Spins In Quantum Dots That Interact Via Single Photons, Hubert P. Seigneur
Electronic Theses and Dissertations
In this dissertation, the prospect of a quantum technology based on a photonic crystal chip hosting a quantum network made of quantum dot spins interacting via single photons is investigated. The mathematical procedure to deal with the Liouville-Von Neumann equation, which describes the time-evolution of the density matrix, was derived for an arbitrary system, giving general equations. Using this theoretical groundwork, a numerical model was then developed to study the spatiotemporal dynamics of entanglement between various qubits produced in a controlled way over the entire quantum network. As a result, an efficient quantum interface was engineered allowing for storage qubits …
Fabrication Of Functional Nanostructures Using Polyelectrolyte Nanocomposites And Reduced Graphene Oxide Assemblies, Anindarupa Chunder
Fabrication Of Functional Nanostructures Using Polyelectrolyte Nanocomposites And Reduced Graphene Oxide Assemblies, Anindarupa Chunder
Electronic Theses and Dissertations
A wide variety of nanomaterials ranging from polymer assemblies to organic and inorganic nanostructures (particles, wires, rods etc) have been actively pursued in recent years for various applications. The synthesis route of these nanomaterials had been driven through two fundamental approaches - 'Top down' and 'Bottom up'. The key aspect of their application remained in the ability to make the nanomaterials suitable for targeted location by manipulating their structure and functionalizing with active target groups. Functional nanomaterials like polyelectrolyte based multilayered thin films, nanofibres and graphene based composite materials are highlighted in the current research. Multilayer thin films were fabricated …
Simulation Of Photochromic Compounds Using Density Functional Theory Methods, Pansy Patel
Simulation Of Photochromic Compounds Using Density Functional Theory Methods, Pansy Patel
Electronic Theses and Dissertations
This Thesis describes the systematic theoretical study aimed at prediction of the essential properties for the functional organic molecules that belong to diarylethene (DA) family of compounds. Diarylethenes present the distinct ability to change color under the influence of light, known as photochromism. This change is due to ultrafast chemical transition from open to closed ring isomers (photocyclization). It can be used for optical data storage, photoswitching, and other photonic applications. In this work we apply Density Functional Theory methods to predict 6 of the related properties: (i) molecular geometry; (ii) resonant wavelength; (iii) thermal stability; (iv) fatigue resistance; (v) …
Dft Study Of Geometry And Energetics Of Transition Metal Systems, Satyender Goel
Dft Study Of Geometry And Energetics Of Transition Metal Systems, Satyender Goel
Electronic Theses and Dissertations
This dissertation focuses on computational study of the geometry and energetics small molecules and nanoclusters involving transition metals (TM). These clusters may be used for various industrial applications including catalysis and photonics. Specifically, in this work we have studied hydrides and carbides of 3d-transition metal systems (Sc through Cu), small nickel and gold clusters. Qualitatively correct description of the bond dissociation is ensured by allowing the spatial and spin symmetry to break. We have tested applicability of new exchange-correlation functional and alternative theoretical descriptions (spin-contamination correction in broken symmetry DFT and ensemble Kohn-Sham (EKS)) as well. We studies TM hydrides …
Architectural Support For Improving Computer Security, Jingfei Kong
Architectural Support For Improving Computer Security, Jingfei Kong
Electronic Theses and Dissertations
Computer security and privacy are becoming extremely important nowadays. The task of protecting computer systems from malicious attacks and potential subsequent catastrophic losses is, however, challenged by the ever increasing complexity and size of modern hardware and software design. We propose several methods to improve computer security and privacy from architectural point of view. They provide strong protection as well as performance efficiency. In our first approach, we propose a new dynamic information flow method to protect systems from popular software attacks such as buffer overflow and format string attacks. In our second approach, we propose to deploy encryption schemes …
Real-Time Cinematic Design Of Visual Aspects In Computer-Generated Images, Juraj Obert
Real-Time Cinematic Design Of Visual Aspects In Computer-Generated Images, Juraj Obert
Electronic Theses and Dissertations
Creation of visually-pleasing images has always been one of the main goals of computer graphics. Two important components are necessary to achieve this goal --- artists who design visual aspects of an image (such as materials or lighting) and sophisticated algorithms that render the image. Traditionally, rendering has been of greater interest to researchers, while the design part has always been deemed as secondary. This has led to many inefficiencies, as artists, in order to create a stunning image, are often forced to resort to the traditional, creativity-baring, pipelines consisting of repeated rendering and parameter tweaking. Our work shifts the …
A New Framework For Qos Provisioning In Wireless Lans Using The P-Persistent Mac Protocol, Kiran Babu Anna
A New Framework For Qos Provisioning In Wireless Lans Using The P-Persistent Mac Protocol, Kiran Babu Anna
Electronic Theses and Dissertations
The support of multimedia traffic over IEEE 802.11 wireless local area networks (WLANs) has recently received considerable attention. This dissertation has proposed a new framework that provides efficient channel access, service differentiation and statistical QoS guarantees in the enhanced distributed channel access (EDCA) protocol of IEEE 802.11e. In the first part of the dissertation, the new framework to provide QoS support in IEEE 802.11e is presented. The framework uses three independent components, namely, a core MAC layer, a scheduler, and an admission control. The core MAC layer concentrates on the channel access mechanism to improve the overall system efficiency. The …
Spatio-Temporal Maximum Average Correlation Height Templates In Action Recognition And Video Summarization, Mikel Rodriguez
Spatio-Temporal Maximum Average Correlation Height Templates In Action Recognition And Video Summarization, Mikel Rodriguez
Electronic Theses and Dissertations
Action recognition represents one of the most difficult problems in computer vision given that it embodies the combination of several uncertain attributes, such as the subtle variability associated with individual human behavior and the challenges that come with viewpoint variations, scale changes and different temporal extents. Nevertheless, action recognition solutions are critical in a great number of domains, such video surveillance, assisted living environments, video search, interfaces, and virtual reality. In this dissertation, we investigate template-based action recognition algorithms that can incorporate the information contained in a set of training examples, and we explore how these algorithms perform in action …
Synthesis Of Analogues Based On The Opioid Alkaloid Mitragynine, Marco A. Arribas
Synthesis Of Analogues Based On The Opioid Alkaloid Mitragynine, Marco A. Arribas
Electronic Theses and Dissertations
Opioid analgesics such as morphine and its derivatives are the most frequently prescribed narcotics for the treatment of severe and chronic pain. Among other side effects caused by the administration of these opioid analgesics, physical dependence and addiction are the most undesirable ones. Currently, pharmacological approaches to treat opioid dependence include mainly methadone and LAAM (mu-agonists), buprenorphine (mu-partial agonist) and clonidine (alpha2-adrenergic agonist). Considering the negative aspects of the relapsing nature correlated to opioid dependence, it is important to search for new ways to overcome this problem. The scope of this work is to study novel compounds based on the …
Development Of Reductive Metal Systems For The Degradation Of Energetic Compounds (Tatp, Tnt, And Rdx), Rebecca L. Albo
Development Of Reductive Metal Systems For The Degradation Of Energetic Compounds (Tatp, Tnt, And Rdx), Rebecca L. Albo
Electronic Theses and Dissertations
Triacetone triperoxide (TATP), a cyclic peroxide explosive, is frequently used by terrorists and amateur chemists due to the ease of synthesis and the availability of reagents. TATP is extremely sensitive to shock, heat, and friction thus a safe and rapid method for treating TATP is needed. The major objective of this dissertation was to develop in situ methodologies that could safely degrade TATP in various field situations. Initial studies focused on using zero-valent metals and mechanically alloyed metals to decompose TATP samples in both aqueous and organic solutions. The metal systems tested included zero-valent iron, magnesium, and magnesium bimetal, Mg/Pd. …
Synthesis And Applications Of Ring Opening Metathesis Polymerization Based Functional Block Copolymers, Sanchita Biswas
Synthesis And Applications Of Ring Opening Metathesis Polymerization Based Functional Block Copolymers, Sanchita Biswas
Electronic Theses and Dissertations
Ring opening metathesis polymerization (ROMP) is established as one of the efficient controlled living polymerization methods which have various applications in polymer science and technology fields. The research presented in this dissertation addresses several applications of multifunctional well-defined norbornene-based block copolymers synthesized by ROMP using ruthenium-based Grubbs catalysts. These novel block copolymers were applied to stabilize maghemite nanoparticles, creating the superparamagnetic polymeric nanocomposites. The Jaggregation properties of the porphyrin dyes were improved via self-assembly with a customized norbornene polymer. Novel multimodal copolymer probes were synthesized for two-photon fluorescence integrin-targeted bioimaging. In Chapter 1 a brief overview of ROMP along with …
Surface Plasmon Hosts For Infrared Waveguides And Biosensors, And Plasmons In Gold-Black Nano-Structured Films, Justin Cleary
Surface Plasmon Hosts For Infrared Waveguides And Biosensors, And Plasmons In Gold-Black Nano-Structured Films, Justin Cleary
Electronic Theses and Dissertations
Applications of surface plasmon polaritons (SPPs) have thus far emphasized visible and near-infrared wavelengths. Extension into the long-wave infrared (LWIR) has numerous potential advantages for biosensors and waveguides, which are explored in this work. A surface plasmon resonance (SPR) biosensor that operates deep into the infrared (3-11 µm wavelengths) is potentially capable of biomolecule recognition based on both selective binding and characteristic vibrational modes. The goal is to operate such sensors at wavelengths where biological analytes are strongly differentiated by their IR absorption spectra and where the refractive index is increased by dispersion, which will provide enhanced selectivity and sensitivity. …
Freeform Reflector Design With Extended Sources, Florian Fournier
Freeform Reflector Design With Extended Sources, Florian Fournier
Electronic Theses and Dissertations
Reflector design stemmed from the need to shape the light emitted by candles or lamps. Over 2,000 years ago people realized that a mirror shaped as a parabola can concentrate light, and thus significantly boosts its intensity, to the point where objects can be set afire. Nowadays many applications require an accurate control of light, such as automotive headlights, streetlights, projection displays, and medical illuminators. In all cases light emitted from a light source can be shaped into a desired target distribution with a reflective surface. Design methods for systems with rotational and translational symmetry were devised in the 1930s. …
Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim
Quantum Dot Based Mode-Locked Semiconductor Lasers And Applications, Jimyung Kim
Electronic Theses and Dissertations
In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-Perot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot lasers is studied. Cavity length dependent lasing via ground state and/or excited state transitions is observed from quantum dot lasers and the optical gain from both transitions is measured. Stable optical pulse trains via ground and excited state transitions are generated using a grating coupled external cavity with a curved two-section device. …
Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures, Nathan Bickel
Electro-Optical And All-Optical Switching In Multimode Interference Waveguides Incorporating Semiconductor Nanostructures, Nathan Bickel
Electronic Theses and Dissertations
The application of epitaxially grown, III-V semiconductor-based nanostructures to the development of electro-optical and all-optical switches is investigated through the fabrication and testing of integrated photonic devices designed using multimode interference (MMI) waveguides. The properties and limitations of the materials are explored with respect to the operation of those devices through electrical carrier injection and optical pumping. MMI waveguide geometry was employed as it offered advantages such as a very compact device footprint, low polarization sensitivity, large bandwidth and relaxed fabrication tolerances when compared with conventional single-mode waveguide formats. The first portion of this dissertation focuses on the characterization of …
Accelerating Optical Airy Beams, Georgios Siviloglou
Accelerating Optical Airy Beams, Georgios Siviloglou
Electronic Theses and Dissertations
Over the years, non-spreading or non-diffracting wave configurations have been systematically investigated in optics. Perhaps the best known example of a diffraction-free optical wave is the so-called Bessel beam, first suggested and observed by Durnin et al. This work sparked considerable theoretical and experimental activity and paved the way toward the discovery of other interesting non-diffracting solutions. In 1979 Berry and Balazs made an important observation within the context of quantum mechanics: they theoretically demonstrated that the Schrodinger equation describing a free particle can exhibit a non-spreading Airy wavepacket solution. This work remained largely unnoticed in the literature-partly because such …
Misalignment Induced Nodal Aberration Fields And Their Use In The Alignment Of Astronomical Telescopes, Tobias Schmid
Misalignment Induced Nodal Aberration Fields And Their Use In The Alignment Of Astronomical Telescopes, Tobias Schmid
Electronic Theses and Dissertations
Following the foundation of aberration theory for rotationally symmetric optical systems established by Seidel, Schwarzschild, Burch, Conrady, Buchdahl, and in its most useful form H.H. Hopkins, Shack, Buchroeder, Thompson, and Rogers developed a vectorial form of the wave aberration theory that enables addressing optical systems without symmetry. In this research, a vectorial theory is utilized and extended for the alignment of two- and three-mirror astronomical telescopes, including the effects of pointing changes and astigmatic figure errors. Importantly, it is demonstrated that the vectorial form of aberration theory, also referred to as nodal aberration theory, not only provides valuable insights but …