Nitrogen-doped TiO2 nanotubes with enhanced visible light photocatalytic activity have been synthesized using commercial titania P25 as raw material by a facile P25/urea co-hydrothermal method. Morphological and microstructual characteristics were conducted by transmission electron microscopy, powder X-ray diffraction, and nitrogen adsorption/desorption isotherms; chemical identifications were performed using X-ray photoelectron spectroscopy, and the interstitial nitrogen linkage to the TiO2 nanotubes is identified. The photocatalytic activity of all nitrogen-doped TiO2 nanotubes synthesized by different urea content, evaluated by the decomposition of rhodamine B dye solution under visible light using UV¡VVis absorption spectroscopy, is found to exhibit higher degradation rate than that of P25. Factors affecting the photocatalytic activity of RB were analyzed and a possible mechanism of photodegradation was also proposed. The high photocatalytic activity was attributed to the process of two different mechanisms, one was the direct degradation of the chromophoric system and the other was successive deethylation of the four ethyl groups.

In this study, the reactive rf magnetron sputtering was used to deposit zinc oxide (ZnO) thin films on Si substrate. The optimal sputtering parameters for film as luminescence application were found to be oxygen concentration (O2/O2+Ar) of 21%, RF power of 100W, substrate temperature of 500¢XC and sputtering pressure of 5 mtorr. Beside, the thermal treatment procedure was carried out to improve the luminescence characteristics of ZnO thin films. The physical characteristics of ZnO thin films deposited on Si substrate with different sputtering parameters were obtained by the analyses of XRD and SEM. The optical properties of ZnO thin films were discussed also. Ultraviolet (UV) visible spectrometer and photoluminescence spectrometer were used to measure the visible transmission and photoluminescence characteristics (PL), respectively. According to the experimental results, it is found that under optimal sputtering parameters, the emitted UV light intensity will be increased as the FWHM in x-ray diffraction is decreased, i.e. the grain size is larger. In addition, after post-deposition annealing at 800¢J, the strongest UV emission intensity was obtained in the nitrogen ambient and the strongest visible (green) emission intensity was obtained in the oxygen ambient.

Titanium Dioxide (TiO2) emerged as one of the most popular photocatalysts since 1970's. However, its photocatalytic activity requires UV irradiation due to its large band gap unless further functionalization or modifications are performed. Furthermore, recovery issue has always been a major drawback, if the more effective form nano particles are utilized. The key objectives of this research were synthesizing new TiO2 based photocatalyst systems that are effective with both the UV and the visible light while utilizing novel superior environmentally friendly techniques enabling development of nano-structured photocatalysts that can be easily recovered. In this dissertation research, highly porous nano-structured TiO2/WO3/Fe3+ aerogel composite photocatalyst are prepared, characterized, and tested for model photocatalytic reactions. The photocatalyst structure is tailored to capture environmental pollutants and enable their decomposition in-situ under both UV and visible light through photodecomposition to smaller benign substances. A novel and green method is applied to prepare unique surfactant templated aerogel photocatalysts with highly porous nano-structure, high surface area, and tailored pore size distribution. Sol-gel process followed by supercritical fluids extraction and drying allowed synthesis of highly porous composite TiO2/WO3 aerogel. The surfactant template was completely removed with the aid of a supercritical solvent mixture followed with heat treatment. Fe3+ ion was incorporated within the composite aerogel photocatalyst as dopant either at the sol-gel co-precipitation step or at a subsequent supercritical impregnation process. Supercritical drying followed with heat treatment results in titanium dioxide with the most profound anatase crystal structure. Neutral templates were used to further enhance retention and tuning of the nano-pore structure and the surface properties. The Nitrogen adsorption-desorption isotherms methods were used to follow the removal of solvents and templates as well as tracking the textural properties of the synthesized aerogel. Surfactant-templated aerogels, which show remarkable thermal stability and uniform pore size distribution, exhibit specific surface areas three times more than the highly optimized commercial nano-particles, industry standard TiO2 photocatalyst Degussa P-25, even after heat treatment. The synthesized catalysts were characterized by using SEM, FIB, EDS, XRD, XPS and porosimetry prior to post photocatalytic activity evaluation through a model photocatalytic reaction. The band gaps of the catalysts were also determined by using diffuse reflectance spectroscopy. The model reaction employed Methylene Blue (MB) photo-oxidation under UV and visible light. Resulting aerogel TiO2/WO3/Fe3+ photocatalyst exhibited comparable photocatalytic capability to Degussa P25 under UV light exposure and offered much superior photocatalytic capability under visible light exposure.

White LEDs (Light Emitting Diodes) in Visible Light Communication (VLC) is an emerging technology that is being researched so it can eventually be used for common communications systems. LEDs have a number of advantages, one of which is long life expectancy. However, like many emerging technologies, VLC has many technical issues that need to be addressed. We proposed an optical indoor wireless communication system that used white LEDs like plug-in devices. We developed a practical implementation of VLC and demonstrated it experimentally. In particular we focused on designing a prototype of VLC that can be used without having to make major changes to the present infrastructure with two types of protocol — namely RS-232 and USB — for data transmission.

Porphyria is a rare metabolic disease which occurs as a result of accumulation of endogenous porphyrins due to specific enzyme deficiency in the biosynthetic pathway of heme. Chloroquine is currently used in the treatment of cutaneous porphyria, although its mechanism of action is not yet well understood. It is believed that chloroquine works in porphyria by forming complexes with excess porphyrin molecules and thus enhancing their elimination from the body. Previous reports of porphyrin-chloroquine complexes have been done mostly in aqueous models. In this study, UV/Visible optical absorbance difference spectroscopy was used to study the complexation of protoporphyrin IX with chloroquine and a range of acceptor molecules in hydrophobic models. The results show that chloroquine, mefloquine, amodiaquine, quinacrine, and pyronaridine formed relatively stronger complexes compared to other molecules such as quinine, duroquinone and caffeine. Therefore, relative to chloroquine, some of the molecules with comparable or greater binding affinity to protoporphyrin IX might also be useful in the treatment of porphyria.

No description available.

The engineering of carrier dynamics in the MQW active region by modifying the p-type layers in the III-nitride based visible LEDs is described in this dissertation. It was found that the holes are preferentially injected into the QW adjacent to the p-InxGa1-xN layer with lower Indium mole fraction. Enhanced hole transport with increasing Indium mole fraction in the p-InxGa1-xN:Mg layer has been shown by analyzing the EL spectra. The improved hole transport and corresponding uniform distribution was achieved presumably by the potential barrier near the p-type layer and the MQW active region resulting in a modified kinetic energy of holes which creates a hole-transport-favorable environment in the MQW active region. At the same time, the limited hole injection due to the potential barrier for holes can be overcome under high injection conditions. The InAlN layers are widely used as an alternative high quality electron blocking layer in InGaN/GaN based visible LED structures. However, the Ga auto-incorporation of the InAlN layers has been recently reported during the growth of epitaxial layers by both MOCVD and MBE. The possible origins and a mechanism of Ga auto-incorporation of InAlN epitaxial layers were systematically investigated in this dissertation. It was found that the Ga-containing deposition on a wafer susceptor/carrier is the most dominant precursor for Ga auto-incorporation and the deposition on surrounding surfaces of quartz parts in a growth chamber is the other dominant source, while the effect of stainless-steel parts and interdiffusion of Ga atom from GaN underlayer are not critical. In addition, Mg or Cp2Mg in the growth chamber during InAl(Ga)N layer growth facilitates the auto-incorporation of Ga by modifying deposition conditions of GaN on the surrounding surfaces and the wafer susceptor/carrier. Based on experimental data of various cases, the Ga-containing deposition on any hot surfaces, which are also exposed to Indium precursor to form a liquid phase, is believed to be major origins of Ga auto-incorporation. In an effort to enhance the light extraction efficiency (LEE) in the LEDs, the direct patterning on the top surface of a LED structure, using laser interference ablation technique, has been studied in this dissertation. The 2-dimensional hexagonal lattice array of surface patterns was generated by direct irradiation of the laser source which is the interference of three laser beams onto the top p-GaN surface, without deterioration of electrical property of p-type layer and optical properties of MQW active region. The experimental results showed approximately 20 % improved LEE of the laser-patterned LED structure compared to the conventional LED structure without surface textures. Furthermore, the theoretical calculation using Monte-Carlo ray-tracing simulation confirmed the enhancement of LEE of the laser-patterned LED structure.

Porphyria is a rare metabolic disease which occurs as a result of accumulation of endogenous porphyrins due to specific enzyme deficiency in the biosynthetic pathway of heme. Chloroquine is currently used in the treatment of cutaneous porphyria, although its mechanism of action is not yet well understood. It is believed that chloroquine works in porphyria by forming complexes with excess porphyrin molecules and thus enhancing their elimination from the body. Previous reports of porphyrin-chloroquine complexes have been done mostly in aqueous models. In this study, UV/Visible optical absorbance difference spectroscopy was used to study the complexation of protoporphyrin IX with chloroquine and a range of acceptor molecules in hydrophobic models. The results show that chloroquine, mefloquine, amodiaquine, quinacrine, and pyronaridine formed relatively stronger complexes compared to other molecules such as quinine, duroquinone and caffeine. Therefore, relative to chloroquine, some of the molecules with comparable or greater binding affinity to protoporphyrin IX might also be useful in the treatment of porphyria.

Ideological shifts in Western society have transformed the process of entry into first unions including: a significant decline in legal marriage, later age marriage, and an increase in nonmarital cohabitation. Some literature has found that these trends have been further impacted by race as the decline in marriage rates has been significantly greater for racial minorities than for non-minorities. This study explores the divergence of marriage patterns on the basis of the visible minority hypothesis, which suggests that visible minority status itself, as a proxy for race will be significant in the first union process. The data were drawn from the 2006 General Social Survey (N= 19,983 men and women). The effects of visible minority status, socioeconomic factors, region, and other cultural markers are explored using Cox’s proportional hazard modeling. The findings suggest that standard economic models are insufficient in explaining differentials in the entry into the first union for visible minorities. That is, visible minority status has an independent effect on the entry into the first union. / Graduate

Dieter Schnebel's String Trio from 2007-2009 is a spatial sound composition that features unique visual components within a traditional string trio setting. This research provides performers and audiences a more thorough understanding of the String Trio and its evocative aesthetic qualities, by identifying and organizing the ways in which the visual and musical material interact. To provide context for String Trio, a brief overview of Schnebel's compositional style and influence on avant-garde musical trends of the latter half of the twentieth century is provided in chapter 2. Special consideration is given to his instrumental chamber music and works for string instruments. In chapter 3, the prior musical analysis and aesthetic context provides a basis for the many conceptual implications resulting from the incorporation of theatricality into a typically non-theatrical genre. The performers' roles within the ensemble and the ways in which they relate to one another as well as their audience, are illuminated and ultimately contribute to a deeper, enhanced experience of the piece. Expectations and traditional notions concerning formal, classical music etiquette are also explored through Schnebel's complex directional changes in orientation and unconventional utilization of the performance space.