A mechanism for alkene metathesis has been proposed by Chauvin, wherein metal carbenes act as catalysts for the reaction. The use and discovery of Fischer-, Tebbe-, Grubbs- and Schrock-type metal carbenes have to a certain extent proven the general mechanism. These metal carbenes showed different activity for alkene metathesis. Only Grubbs- and Schrock-type carbenes proved to be highly active for metathesis. A lot of studies have been done on the reasons for the activity, but still the main factors are unknown. In this study a molecular modelling investigation into the mechanism of the alkene metathesis reaction is done in an attempt to identify a factor(s) that can predict activity. By defining and knowing factors that contribute to activity, new catalysts can be designed that are truly active and selective. Fischer-, Tebbe-, Grubbs- and Schrocktype metal carbenes are investigated in this regard. The results of the investigation indicate that the frontier molecular orbital theory shows a possibility for prediction of alkene metathesis activity. By observing the size and location of the atomic orbital coefficients of the molecular orbital, the site of primary overlap for formation of metathesis products could be identified. The largest atomic orbital coefficient of the LUMO should be located on the metal atom. An atomic orbital coefficient should also be present on the carbene carbon for secondary overlap for formation of the metallacyclobutane intermediate. By exchanging the ruthenium in the second generation Grubbs catalyst framework the effect of the metal could be elucidated. The results clearly showed the important influence the metal atom has on the electronic properties of the catalyst complex. The results of frontier molecular orbital calculations supported the general activity trend of the four main types of metal carbenes for the metathesis of linear alkenes. By changing the metal in known catalyst frameworks a deeper understanding can be gained for the design of new alkene metathesis catalysts. / Thesis (PhD (Chemistry))--North-West University, Potchefstroom Campus, 2013

A mechanism for alkene metathesis has been proposed by Chauvin, wherein metal carbenes act as catalysts for the reaction. The use and discovery of Fischer-, Tebbe-, Grubbs- and Schrock-type metal carbenes have to a certain extent proven the general mechanism. These metal carbenes showed different activity for alkene metathesis. Only Grubbs- and Schrock-type carbenes proved to be highly active for metathesis. A lot of studies have been done on the reasons for the activity, but still the main factors are unknown. In this study a molecular modelling investigation into the mechanism of the alkene metathesis reaction is done in an attempt to identify a factor(s) that can predict activity. By defining and knowing factors that contribute to activity, new catalysts can be designed that are truly active and selective. Fischer-, Tebbe-, Grubbs- and Schrocktype metal carbenes are investigated in this regard. The results of the investigation indicate that the frontier molecular orbital theory shows a possibility for prediction of alkene metathesis activity. By observing the size and location of the atomic orbital coefficients of the molecular orbital, the site of primary overlap for formation of metathesis products could be identified. The largest atomic orbital coefficient of the LUMO should be located on the metal atom. An atomic orbital coefficient should also be present on the carbene carbon for secondary overlap for formation of the metallacyclobutane intermediate. By exchanging the ruthenium in the second generation Grubbs catalyst framework the effect of the metal could be elucidated. The results clearly showed the important influence the metal atom has on the electronic properties of the catalyst complex. The results of frontier molecular orbital calculations supported the general activity trend of the four main types of metal carbenes for the metathesis of linear alkenes. By changing the metal in known catalyst frameworks a deeper understanding can be gained for the design of new alkene metathesis catalysts. / Thesis (PhD (Chemistry))--North-West University, Potchefstroom Campus, 2013

Density functional (DFT) methods are first used to study 22 of the most stable solution-phase UN4O12 isomers containing uranyl nitrate, UO2(NO3)2. Based on relative free energy calculations, 4 solution (a6, a5, a8, and a1) and 5 gas-phase isomers (a1, a2, a3, b1, and b2) are identified as the strongest candidates to exist and possibly predominate within their respective environments. DFT is then applied to a new form of binucleating Schiff–base polypyrrolic macrocycles containing actinyl ions [AnO2]n+ (An = U, Np, Pu; n = 1, 2) and 3d transition metals (TM): Mn, Fe, Co, and Zn. Formal bond order evidence is provided for 24 TM to actinyl–endo–oxygen partial bond formations. Special structural cases are discussed. Redox potentials for AnVIO21/AnVO21– couples closely follow the Np > Pu > U trend seen for AnO2(H2O)52+/1+. Predictions of –1.10, 0.25, and 0.01 eV are made for U, Np, and Pu redox potentials.

<p>As integrated circuits (ICs) continue to scale to smaller dimensions, long interconnects</p><p>have become the dominant contributor to circuit delay and a significant component of</p><p>power consumption. In order to reduce the length of these interconnects, 3D integration</p><p>and 3D stacked ICs (3D SICs) are active areas of research in both academia and industry.</p><p>3D SICs not only have the potential to reduce average interconnect length and alleviate</p><p>many of the problems caused by long global interconnects, but they can offer greater design</p><p>flexibility over 2D ICs, significant reductions in power consumption and footprint in</p><p>an era of mobile applications, increased on-chip data bandwidth through delay reduction,</p><p>and improved heterogeneous integration.</p><p>Compared to 2D ICs, the manufacture and test of 3D ICs is significantly more complex.</p><p>Through-silicon vias (TSVs), which constitute the dense vertical interconnects in a</p><p>die stack, are a source of additional and unique defects not seen before in ICs. At the same</p><p>time, testing these TSVs, especially before die stacking, is recognized as a major challenge.</p><p>The testing of a 3D stack is constrained by limited test access, test pin availability,</p><p>power, and thermal constraints. Therefore, efficient and optimized test architectures are</p><p>needed to ensure that pre-bond, partial, and complete stack testing are not prohibitively</p><p>expensive.</p><p>Methods of testing TSVs prior to bonding continue to be a difficult problem due to test</p><p>access and testability issues. Although some built-in self-test (BIST) techniques have been</p><p>proposed, these techniques have numerous drawbacks that render them impractical. In this dissertation, a low-cost test architecture is introduced to enable pre-bond TSV test through</p><p>TSV probing. This has the benefit of not needing large analog test components on the die,</p><p>which is a significant drawback of many BIST architectures. Coupled with an optimization</p><p>method described in this dissertation to create parallel test groups for TSVs, test time for</p><p>pre-bond TSV tests can be significantly reduced. The pre-bond probing methodology is</p><p>expanded upon to allow for pre-bond scan test as well, to enable both pre-bond TSV and</p><p>structural test to bring pre-bond known-good-die (KGD) test under a single test paradigm.</p><p>The addition of boundary registers on functional TSV paths required for pre-bond</p><p>probing results in an increase in delay on inter-die functional paths. This cost of test</p><p>architecture insertion can be a significant drawback, especially considering that one benefit</p><p>of 3D integration is that critical paths can be partitioned between dies to reduce their delay.</p><p>This dissertation derives a retiming flow that is used to recover the additional delay added</p><p>to TSV paths by test cell insertion.</p><p>Reducing the cost of test for 3D-SICs is crucial considering that more tests are necessary</p><p>during 3D-SIC manufacturing. To reduce test cost, the test architecture and test</p><p>scheduling for the stack must be optimized to reduce test time across all necessary test</p><p>insertions. This dissertation examines three paradigms for 3D integration - hard dies, firm</p><p>dies, and soft dies, that give varying degrees of control over 2D test architectures on each</p><p>die while optimizing the 3D test architecture. Integer linear programming models are developed</p><p>to provide an optimal 3D test architecture and test schedule for the dies in the 3D</p><p>stack considering any or all post-bond test insertions. Results show that the ILP models</p><p>outperform other optimization methods across a range of 3D benchmark circuits.</p><p>In summary, this dissertation targets testing and design-for-test (DFT) of 3D SICs.</p><p>The proposed techniques enable pre-bond TSV and structural test while maintaining a</p><p>relatively low test cost. Future work will continue to enable testing of 3D SICs to move</p><p>industry closer to realizing the true potential of 3D integration.</p> / Dissertation

The application of digital signal processing (DSP) for the identification of the locations of hot spots in proteins is explored. DSP provides a natural framework for analyzing biologi¬cal sequence information due to the inherently discrete nature of the biological sequences. Two new techniques for the identification of the locations of hot spots in proteins are proposed. In the first technique. the short-time discrete Fourier transform (STDFT) of the protein numerical sequence is computed and its columns are multiplied by the discrete Fourier transform (DFT) coefficients. Through this technique, hot-spot locations can be clearly identified in teens of distinct peaks in the spectrogram, thus achieving good local¬ization in the amino-acid domain. Several example protein sequences are used to illustrate the technique. The second technique is based on the use of digital filters. The criteria that determine the filter type and the filter-design specifications for the application of interest are dis¬cussed. Based on this investigation, the inverse-Chebyshev UR digital filter is found to be the most suitable filter for the application. The use of zero-phase filtering to eliminate the need of computing the phase response of the digital filter is also investigated. A control parameter that can be used to distinguish the hot-spot locations on the basis of their sig¬nificance in the protein's function is introduced. The technique is then illustrated by using the same set of example protein sequences that were used for the first technique. The two techniques are then compared in teens of their computational complexity. The filter-based technique is found to be computationally much more efficient than the transform-based technique and hence it is much more suitable for a hardware implementation. The proposed techniques are capable of identifying the known hot-spot locations with good accuracy. In addition, they also identify several new hot-spot locations that may provide new insights into the working of protein molecules.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23898号 / 工博第4985号 / 新制||工||1778(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 田中 功, 教授 邑瀬 邦明, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

In this work, Gold and Copper oxidation catalysts supported on a range of metal oxides were synthesised via 2 previously uninvestigated preparation methods. In the first chapter, Gold nanoparticle catalysts were deposited onto TiO2, CeO2 and ZrO2 nanoparticles via the non-aqueous Modified Photodeposition procedure. This method was found to produce smaller Gold particle sizes following intrinsic excitation of the support than the conventional aqueous phase method, with surface physisorbed water apparently acting as the sacrificial reductant. The as prepared catalysts were drastically more active than those prepared by the conventional method and under standardised tests were directly comparable to those prepared by the Deposition Precipitation Method. The second part of the work, explored the preparation of metal oxide supported Copper catalysts via the Flame Spray Pyrolysis process. CO Oxidation tests established the following order of activity for 4wt% Cu loaded on the various supports: Cu-CeO2 > Cu-TiO2 > Cu-ZrO2 > Cu-Al2O3 > Cu-SiO2. CO-TPD studies found that more active materials tended to adsorbed more CO and reacted higher proportions of this with lattice oxygen to form CO2 at lower temperatures. The addition of Cu to each metal oxide surface was found to induce lengthening of the average Metal-Oxygen bond length, with higher electron density on surface O. This phenomenum is proposed as being responsible for the widely reported ???synergistic effect??? reported for similar Cu catalysts. Cu-CeO2 (0-12wt%) catalysts were tested in the Preferential CO Oxidation (COPROX) reaction. Increasing Cu content, varied the Cu morphology from monomers, through to dimers and ultimately CuO crystallites. DFT simulations of the Cu dimer structure revealed higher levels of bonding ionicity in this morphology, relative to the monomeric structure. This coincided with higher levels of activity, reinforcing the earlier finding that highly ionic bonds are conducive to higher levels of activity. High levels of activity and selectivity were maintained until approximately 423 K. Surface redox properties of the 4wt% Cu-CeO2 catalyst were assessed using temperature-programmed reduction (CO, H2) and desorption (CO) experiments, as well as in situ and phase-resolved infrared spectroscopy to study the transition to nonselective conditions. For the first time, it was demonstrated that CO and H2 react at identical surface sites, with CO2 formation proceeding simultaneously via three distinct Cux+-CO carbonyl species. Under non-selective conditions, a gradual red-shift and loss of intensity in the carbonyl peak was observed, indicating reduction of Cu+ to Cu0 and the onset of an alternate non-selective redox-type oxidation mechanism. These results for Cu-CeO2 suggest that improved low temperature catalytic activity will only be achieved at the expense of reduced high temperature selectivity and vice versa. The final section of work explored the use of Cu-based catalysts for the low temperature oxidation of Acetaldehyde (ACA). Based on this work, it is concluded that the ACA oxidation activity of these materials is determined by two main factors: the basicity of the metal oxide support (and its subsequent ability to convert ACA to carboxylates) and the availability of surface oxygen during acetate decomposition. It is proposed that a high concentration of reducible sites (either by Cu addition or naturally occurring on CeO2) accelerates the activation and provision of oxygen and also potentially provides sites for the stabilization of methoxy intermediates resulting from the acetate decomposition.

Carbon-based materials have attracted great attention over past few years in hydrogen storage applications. In particular, nanofibrous carbon working as support for sodium alanate exhibits great improvement in the kinetics of H2 releasing/uptaking. Herein, we used graphene with various dopants to simulate the carbon materials and performed a periodic density functional theory study on the impact of the modifications on the hydrogen interaction in the supported sodium alanate. Our results showed that the impact of various defects and dopants can be categorized in groups: (i) Pristine graphene and pentagon-heptagon (5-7) pair defective graphene, as well as nitrogen and sulfur doped graphene do not promote H2 formation. (ii) Carbon vacancies, as well as boron and chlorine doped systems, cause instantaneous H2 formation. (iii) Oxygen, phosphor and fluorine doped graphene led to the formation of a meta-stable di-hydrogen state with a H-H distance of ~ 0.96 Å. In addition, we confirmed the importance of van der Waals interaction in our system.

In this dissertation, density functional theory (DFT) calculations were used to investigate (1)NO2 adsorption on BaO in NOx Storage Reduction (NSR) catalyst affected by the morphology of BaO and the γ-Al2O3 support, (2) energy barrier of H2 dissociative adsorption over Mg clusters affected by its electronic structure, and (3) comparison of the activities of CeO2 clusters affected by two different supports--monoclinic ZrO2 and non-spinel γ-Al2O3. Our results showed that the electronic effect caused by the non-stoichiometry of the bare BaO clusters and surfaces improves their reactivities toward NO2 adsorption greatly, whereas the geometric structure of the catalyst has only minor effect on the activity; we also found that the γ-Al2O3 substrate improves the reactivities of the supported BaO clusters and at the same time the interface between BaO and γ-Al2O3 provided a unique and highly reactive environment for NO2 adsorption. Hydrogen dissociation barrier over pure Mg clusters is greatly affected by the electronic structure of the clusters--closed shell clusters such as Mg10 and Mg92- have higher energy barrier toward H2 dissociation; however, H2 dissociation over clusters that are two electrons shy from the closed electronic shell are relatively easier. As substrates, neither ZrO2(111) nor γ-Al2O3(100) affects the reactivity of the supported Ce2O4 toward CO2 adsorption and CO physisorption significantly; whereas the reactivity of Ce2O4 toward CO reactive adsorption were found to be affected by the two substrates very differently.

Neste trabalho, estudou-se a síntese de filmes finos de BiVO4 e WO3-CuWO4 por spin coating e sputtering, respectivamente. Esses filmes foram utilizados na foto produção de corrente e hidrogênio a partir da água e luz solar (fotoeletrólise). Adicionalmente, foi preparado utilizando a reação de estado sólido o composto quaternario proposto teóricamente por Pranab Sarker como um promisor fotocatalizador para produção de hidrogênio. Finalmente, foi aplicada a teoria do funcional da densidade ao estudo das propriedades eletronicas e estruturais do e dos sistemas citados acima. / In this work, the synthesis of thin films of BiVO4 and WO3-CuWO4 by spin coating and sputtering, respectively, was studied. These films were used in the photo production of current and hydrogen from water and sunlight (photoelectrolysis). Additionally, the quaternary compound proposed theoretically by Sarker Pranab was prepared using the solid state reaction as a photocatalytic suitable for the production of hydrogen. Finally, the density functional theory was applied to the study of the electronic and structural properties of and the systems mentioned above.