The rapid progress of n-type metal oxide thin film transistors (TFTs) has motivated research on p-type metal oxide TFTs in order to realise metal oxide-based CMOS circuits which enable low power consumption large-area electronics. Cuprous oxide (Cu2O) has previously been proposed as a suitable active layer for p-type metal oxide TFTs. The two most significant challenges for achieving good quality Cu2O TFTs are to overcome the low field-effect mobility and an unacceptably high off-state current that are a feature of devices that have been reported to date. This dissertation focuses on improving the carrier mobility, and identifying the main origins of the low field-effect mobility and high off-state current in Cu2O TFTs. This work has three major findings. The first major outcome is a demonstration that vacuum annealing can be used to improve the carrier mobility in Cu2O without phase conversion, such as oxidation (CuO) or oxide reduction (Cu). In order to allow an in-depth discussion on the main origins of the very low carrier mobility in as-deposited films and the mobility enhancement by annealing, a quantitative analysis of the relative dominance of the main conduction mechanisms (i.e. trap-limited and grain-boundary-limited conduction) is performed. This shows that the low carrier mobility of as-deposited Cu2O is due to significant grain-boundary-limited conduction. In contrast, after annealing, grain-boundary-limited conduction becomes insignificant due to a considerable reduction in the energy barrier height at grain boundaries, and therefore trap-limited conduction dominates. A further mobility improvement by an increase in annealing temperature is explained by a reduction in the effect of trap-limited conduction resulting from a decrease in tail state density. The second major outcome of this work is the observation that grain orientation ([111] or [100] direction) of sputter-deposited Cu2O can be varied by control of the incident ion-to-Cu flux ratio. Using this technique, a systematic investigation on the effect of grain orientation on carrier mobility in Cu2O thin films is presented, which shows that the [100] Cu2O grain orientation is more favourable for realising a high carrier mobility. In the third and final outcome of this thesis, the temperature dependence of the drain current as a function of gate voltage along with the C-V characteristics reveals that minority carriers (electrons) cause the high off-state current in Cu2O TFTs. In addition, it is observed that an abrupt lowering of the activation energy and pinning of the Fermi energy occur in the off-state, which is attributed to subgap states at 0.38 eV below the conduction band minimum. These findings provide readers with the understanding of the main origins of the low carrier mobility and high off-state current in Cu2O TFTs, and the future research direction for resolving these problems.

一氧化氮（NO）和內皮源性超極化因子（EDHFs）是內皮衍生的血管舒張因子兩大類。 EETs是構成EDHFs的主要類型，這是由花生四烯酸通過細胞色素P450 （CYP）表氧化酶的催化活性得到。雖然這兩個EET和NO誘導血管舒張，從而降低血壓，許多報告表明，NO對EET引起的血管舒張起抑製作用。然而，不管它的重要性，有關一氧化氮對EETs的抑制作用的機理尚未完全了解。 / 在本研究中，我調查了一氧化氮對EET的負調控。通過膜電位和動脈張力測量，我們發現， 11,12-EET可引起內皮剝脫豬冠狀動脈平滑肌細胞膜超極化和血管舒張。該反應被S-亞硝基-N-乙酰青黴胺（SNAP）和8-Br-cGMP，一個NO的供體和cGMP的膜穿透物類似物，分別抑制。 SNAP和8-Br-cGMP對11,12-EET引起的細胞膜超極化和血管舒張的抑製作用被羥鈷胺，一氧化氮清除劑; ODQ ，鳥苷酸環化酶抑製劑;和KT5823 ，蛋白激酶G（PKG）抑製劑逆轉。 SNAP和8-Br-cGMP對EET反應的抑製作用也被過度供應外源性激酶底物， TAT-TRPC1S¹⁷²和TAT -TRPC1T³¹³廢除。羥鈷胺，ODQ， KT5823， TAT -TRPC1，和TAT -scrambled獨自使用不影響11,12-EET引起的細胞膜超極化和血管舒張作用。然而，獨自使用14，15-EEZE（EET的拮抗劑）抑制了11,12-EET的作用。 此外，磷酸化試驗表明， PKG可以直接在Ser172和Thr313位點磷酸化TRPC1 。此外，TRPV4 ， TRPC1 ，或KCa1.1被選擇性地抑制時，11,12-EET未能引起細胞膜超極化和血管舒張。免疫共沉澱研究表明， TRPV4 ， TRPC1和KCa1.1物理上彼此相關聯。 / 以上結果表明，NO-cGMP-PKG通路可通過TRPC1的磷酸化來抑制11,12- EETs在冠狀動脈血管平滑肌細胞上的作用。此外，TRPV4，TRPC1和KCa1.1參與11,12-EET誘導平滑肌超極化和血管舒張，他們可能互相關聯。從本研究的結果表明，NO和cGMP可通過PKG-介導的TRPC1的磷酸化，抑製EET誘導的平滑肌超極化和血管舒張。 / Nitric oxide (NO) and endothelium-derived hyperpolarizing factors (EDHFs) are two main classes of endothelium-derived vascular relaxant factors. EETs constitute a major type of EDHFs, which are derived from arachidonic acids via the catalytic activity of cytochrome P450 (CYP) epoxygenases. Although both EET and NO induce vascular relaxation, thus reduce blood pressure, numerous reports demonstrated that NO exerts an inhibitory action on EET-induced vascular relaxation. However, despite of its importance, the mechanisms related to the inhibitory effects of NO on EETs are incompletely understood. / In the present study, I investigated the scheme for negative regulation of NO on EET action. Through measurements of membrane potential and arterial tension, we showed that 11,12-EET could induce membrane hyperpolarization and vascular relaxation in endothelium-denuded porcine coronary arteries. The responses were suppressed by S-nitroso-N-acetylpenicillamine (SNAP) and 8-Br-cGMP, a NO donor and a membrane-permeant analogue of cGMP, respectively. The inhibitory actions of SNAP and 8-Br-cGMP on 11,12-EET-induced membrane hyperpolarization and vascular relaxation were reversed by hydroxocobalamin, a NO scavenger; ODQ, a guanylyl cyclase inhibitor; and KT5823, a protein kinase G (PKG) inhibitor. The inhibitory actions of SNAP and 8-Br-cGMP on EET responses were also abrogated by shielding TRPC1-PKG phosphorylation sites with excessive supply of exogenous PKG substrates, TAT-TRPC1S¹⁷² and TAT-TRPC1T³¹³. Hydroxocobalamin, ODQ, KT5823, TAT-TRPC1 and TAT-scrambled alone has no effect on 11,12-EET-induced membrane hyperpolarization and vascular relaxation. However, 14,15-EEZE (a selective EET antagonist) alone inhibits the action of 11,12-EET. Furthermore, phosphorylation assay was performed and it demonstrated that PKG could directly phosphorylate TRPC1 at Ser¹⁷² and Thr³¹³. In addition, 11,12-EET failed to induce membrane hyperpolarization and vascular relaxation when TRPV4, TRPC1, or KCa1.1 was selectively inhibited. Co-immunoprecipitation studies demonstrated that TRPV4, TRPC1 and KCa1.1 physically associated with each other in smooth muscle cells. / Taking together, our findings demonstrated that the NO-cGMP-PKG pathway may act through the phosphorylation of TRPC1 to inhibit the action of 11,12-EETs in coronary arterial smooth muscle cells. Furthermore, TRPV4, TRPC1 and KCa1.1 are critically involved in the 11,12-EET-induced smooth muscle hyperpolarization and relaxation and that they may physically associate with each other. The results from this study demonstrated that NO and cGMP could lead to PKG-mediated phosphorylation of TRPC1, resulting in an inhibition of EET-induced smooth muscle hyperpolarization and vascular relaxation. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Zhang, Peng. / "Ca" on title page is subscript. / Thesis (Ph.D.) Chinese University of Hong Kong, 2014. / Includes bibliographical references (leaves 115-133). / Abstracts also in Chinese.

Thesis (M.Sc. (Physics)) -- University of Limpopo, 2015 / Nanocrystalline materials of defect free anatase and rutile SnO2 together with Ti and Y in anatase SnO2 have been modelled successfully using classical molecular dynamics simulations together with Buckingham potential. The structural properties of these SnO2 phases were analysed using radial distribution functions (RDFs). The effect of increasing temperature in pure SnO2 and doped SnO2 were studied. In both pure and doped materials, RDFs suggest phase transition at higher temperature, where anatase SnO2 transforms to rutile SnO2. Rutile SnO2 was found to be more stable than anatase SnO2. The results showed that the dopants have different effects on the SnO2 material. Ti defect is found to lower the transformation temperature of anatase to rutile SnO2. Y defect is found not to have any effect on the anatase to rutile SnO2 transformation. Thermodynamic properties such as volume thermal expansion coefficient and specific heat capacity were also calculated from above Debye temperature. Volume thermal expansion coefficient was obtained from volume versus temperature curves. Volume thermal expansion coefficient for rutile and Ti-anatase SnO2 were found to be not of the same order with the calculated results. Specific heat capacity calculated from energy versus temperature curves was found to be in agreement with the Dulong and Petit law of solids. Nanocrystalline Al/Y co-doped SnO2 powders were successfully synthesized using the sol-gel method. The samples were subjected to different temperatures 100 (as prepared) 200, 400, 600, 800 and 1000 oC. The effects of co-doping and temperature on the structural and optical properties of Al/Y co-doped SnO2 nanoparticles as well as morphology were investigated. The characterization techniques used were X-ray powder diffraction (XRD), Raman spectroscopy, Scanning electron microscopy (SEM) and UV-visible spectroscopy (UV-vis). The average particle sizes were found to be in the range between 2.5–8 nm and the strains were calculated to be 2.76–0.53 with increasing temperature for as prepared and the sample sintered at different tempe-ratures. The Raman bands were found to correspond with the literature. At a higher temperature of about 800 oC the materials were found to contain the second phase which is yttrium stannate. However no information about aluminium was found. The optical band gap were found to be between 3.3–3.99 eV in the temperature range 200–1000 oC.

Lowering the operating temperature of the high-temperature, solid oxide fuel cell (SOFC) improves both the thermodynamic efficiency and the lifetime of this energy efficient technology. Unfortunately the rate of oxygen-ion transport through the solid electrolyte is temperature dependent, and materials previously employed as electrolytes in the high-temperature SOFC perform poorly at intermediate temperatures. Therefore new oxygen-ion conductors with enhanced ionic conductivity at intermediate temperatures are required. The bulk of the existing literature on high-temperature SOFCs has focussed on zirconia-based binary systems as electrolytes, due to their high ionic conductivity and negligible electronic conductivity. Only select compositions within the zirconia-scandia system have demonstrated acceptable ionic conductivity levels at intermediate temperatures; however unstable phase assemblage and the high economic cost of scandia are clear disadvantages. Ceria-based binary systems have demonstrated improved oxygen-ion conductivity at intermediate temperature compared to many zirconia systems, however significant levels of n-type electronic conductivity are observed at low oxygen partial pressures. Consequently it was thought unlikely that significant increases in ionic conductivity would be found in existing zirconia- and ceria-based binary systems, therefore another approach was required in an attempt to improve the performance of these established fluorite systems. The fluorite systems Zr0.75Ce0.08M0.17O1.92 (M = Nd, Sm, Gd, Dy, Ho, Y, Er, Yb, Sc) were prepared and investigated as possible, intermediate-temperature SOFC electrolytes in an attempt to combine the higher conductivity found in the ceria systems with the low electronic conductivity observed in the zirconia systems. Also it was anticipated that systems containing dopants not previously observed to confer high ionic conductivity in either zirconia- and ceria-based binary systems, might exhibit enhanced ionic conductivity with expansion of the zirconia lattice resulting from the addition of ceria. All the as-fired Zr0.75Ce0.08M0.17O1.92 compositions possessed the face-centred cubic structure and lattice parameter measurements revealed the anticipated unit cell enlargement as the size of the dopant cation increased. No unusual microstructural parameters were identified that could be expected to interfere with the ionic transport properties in the as-fired compositions. The electrical conductivity was found to be influenced by the dopant-ion radius, the presence of ceria, low oxygen partial pressures and, in some compositions, the formation of poorly conducting, ordered-pyrochlore microdomains dispersed amongst the cubic defect-fluorite matrix. In a second approach to the formulation of new oxygen-ion conductors suitable for the intermediate-temperature SOFC, compounds possessing structures other than the fluorite structure were considered. An examination of the literature for oxides having the pyrochlore, scheelite and perovskite structures showed that the Sr+2- and Mg+2-doped LaGaO3 perovskites (LSGM) possessed ionic conductivity equal to the highest conducting, zirconia and ceria binary compounds. Therefore the perovskite systems La0.9Sr0.1Ga(0.8-x)InxMg0.2O2.85 (X = 0, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8) (I-LSGM) were prepared and examined, the objective being to favourably influence structural parameters believed responsible for optimal ionic conductivity, namely the unit cell symmetry and volume. It was found that In+3 systematically substituted for Ga+3 on to the B-site of LSGM at least up to the X = 0.4 composition. While In+3 was found to replace the Ga+3 as expected, Mg+2, which occupies the same crystallographic site, was also replaced by In+3. Up to the X = 0.2 composition, at least two trace level secondary phases were observed to form along with the bulk I-LSGM phase. For I-LSGM compositions with X > 0.2, significantly larger concentrations of the secondary phases were identified. Evidence of a strontium-rich, high-temperature liquid phase was observed also near the grain boundaries on as-sintered and thermally etched surfaces in LSGM and I-LSGM compositions. It is believed that the observed, high sintered density in the complex, doped-LaGaO3 systems is due to the formation of this high-temperature liquid phase. Increasing levels of diffuse scatter and superstructure formation were observed in electron diffraction patterns in the I-LSGM bulk phase (up to X = 0.2), indicating a possible decrease in vacancy concentration and reduced, localised unit cell symmetry. The electrical conductivity in the I-LSGM compositions was believed to be influenced by the distortion of the oxygen-ion conduction path, a reduction in vacancy concentration, formation of stronger dopant-vacancy associates at low temperature and the presence of ordered structures. In addition, phase instability, in the form of subtle ordering in specific crystalline planes, was observed to influence the electrical conductivity as a function of time at intermediate temperatures.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 75-77

Nuclear techniques such as perturbed angular correlation (PAC) sample the hyperfine interactions of a large number of probe atoms in specific crystallographic sites. Real crystals contain static defects producing a distribution of electric field gradients (EFGs) that add to the ideal EFG of the crystal at any given probe site. Also, dynamic defects like moving vacancies and interstitial atoms can be present in the crystal and contribute to the distribution of EFGs. The distribution of EFGs leads to line broadening and a change in the observed asymmetry parameter η since the total EFG no longer has the symmetry of the perfect crystal. When both defects are present in a material, obtaining quantitative information from the analysis of PAC spectra is usually very difficult since great care has to be taken to ensure that the source of line broadening is identified correctly. In order to relate the relationship between the static line broadening and changes in the asymmetry parameter η, a uniform random distribution of point charges was used to simulate the static defect EFG. PAC spectra collected on cubic niobium metal, cubic stabilized zirconia and Nb-doped tetragonal zirconia were fitted with this model. Although the quality of the fits is good, more work is needed to clarify the relationship between the new model parameters and the line broadening and asymmetry parameter derived from conventional model fits. The PAC spectra of Nb-doped tetragonal zirconia were fitted with a conventional static model to establish a reliable relationship between line broadening and the asymmetry parameter when only static defects are present in a sample. To account for effects of dynamic defects, a four state stochastic model for vacancy motion was adapted in order to include the line broadening and changes in the asymmetry produced by static defects. As a result, the activation energies corresponding to the rates at which a oxygen vacancy is trapped by, detraps from, and hops among equivalent sites about a PAC probe atom were calculated. The values that were found are physically reasonable, indicating that the dynamics of an oxygen vacancy around a PAC probe atom are satisfactorily described. / Graduation date: 2003

Originally presented as the author's thesis (Swiss Federal Institute of Technology), Diss. ETH No. 16228. / Summary in German and English, text in English. Includes bibliographical references (p. 123-132).

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In this study, the carbon electrode of supercapacitor was fabricated by using mesocarbon microbeads. For finding the optimal processing parameters of carbon electrode, the effects of specific surface area of activated carbon, the amount of carbon black and binder, and various electrolytes on the capacitative properties of supercapacitor are investigated. To fabricate the composite electrode of supercapacitor, NiO and WO3 thin films were deposited respectively on the carbon electrode by electron beam evaporation. The influences of various scan rates of cyclic voltammograms (CV) on the characteristic of capacitance are studied. The charge-discharge efficiency and life time of the composite electrode are also discussed. Experimental results reveal that the optimum carbon electrode can be obtained using mesocarbon microbeads with high specific surface area (2685 m2/g) and larger pore volume (0.6 cm3/g) and adding 10 wt.% carbon black and 2wt.% binder. The specific capacitances of carbon electrodes in 1 M KOH and 1 M Et4NBF4 are 230.8 F/g and 221.5 F/g, respectively. Besides, the XRD and SEM results showed that NiO and WO3 thin films on composite electrode are sheet-liked crystal structure and stone-liked amorphous structure, respectively. The composite electrode exhibits better capacitance properties than those of carbon electrode at high scan rate by CV analysis. It reveals the promotion of the capacitative property of supercapacitor at higher power density and the improving of the decay property in capacitance at high scan rate. Finally, in the test of charge-discharge efficiency and life time, the charge-discharge efficiency is near 100% after 5000 cycles and it still retains good adhesion between electrode material and substrate.

Aging is associated impaired endothelial function in the skeletal muscle vasculature which contributes to decreased ability to increase muscle blow during exercise. This endothelial dysfunction is mediated, primarily, by impairments in the nitric oxide (NO) pathway in the skeletal muscle vasculature. The major purpose of this dissertation is to determine the mechanisms that mediate age-related endothelial dysfunction in rat soleus feed artery (SFA) and determine whether exercise training ameliorates this impairment in endothelial function. Therefore in these series of studies we sought to test three major hypotheses: 1) That exercise training reverses age-related decrements in endothelium-dependent dilation in SFA and that this improved endothelium-dependent dilation is the result of increased NO bioavailability due to increased content and phosphorylation of eNOS and/or increased antioxidant enzyme content; 2) That age-related endothelial dysfunction in rat SFA is mediated in part, by NAD(P)H oxidase-derived reactive oxygen species (ROS); 3) and, that impaired endothelium-dependent dilation in senescent SFA is due to an impaired potential for p-eNOSser1177. To test these hypotheses, SFA from young (4 month) and old (24 month) Fischer 344 rats were isolated for either determination of endothelium-dependent and –independent dilations or biochemical analyses. Results from these investigations suggest that 1) exercise training reverses the detrimental effects of aging on endothelial function in skeletal muscle feed arteries by enhancing the capacity to scavenge superoxide, increasing the bioavailability of NO; 2) ROS contribute to impaired endothelium-dependent dilation in old SFA; whereas, ROS appear to play a role in ACh-mediated dilation in SFA from young rats; 3) and, that the PI3 kinase/protein kinase B (Akt)/eNOS pathway is preserved with age.