Thesis (M.S.) University of Missouri-Columbia, 2006. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 21, 2007) Vita. Includes bibliographical references.

Researchers have recently become interested in two-dimensional materials such as graphene, hexagonal boron nitride (h-BN), Transition Metal Dichalcogenides (TMDs), etc. Their 2D hexagonal structures result in unique properties, which make these materials attractive for scientists and engineers. In this work, we investigated the electronic properties of graphene, h-BN, and MoS2 based on density functional theory (DFT). We first studied the electronic properties of monolayers of different materials. We found a zero bandgap and observed massless Dirac Hamiltonian in graphene. For h-BN, a large bandgap at K-point was observed. Also, we observed the bandgap opening in MoS2 and a strong splitting of its bands. Then, we extended these studies to graphene and h-BN bilayers. For graphene bilayer, we observed a gapless material and massive Dirac fermions. For h-BN bilayer, an indirect bandgap was observed, smaller in comparison with its monolayer. The main focus of this study was the investigation of graphene/h-BN heterostructures for different stacking configurations. The suitability of h-BN as a substrate for graphene is due to its small lattice constant mismatch with graphene and its high insulating gap (~ 5 eV). Another important aspect to be observed in graphene/h-BN heterostructures is the gap opening brought by the h-BN layer proximity to the initially gapless graphene layer. We found the effect of bandgap opening in graphene/h- BN and determined the most stable configuration which is the AB[CB]. This work supports the findings of many researchers who demonstrate that graphene/h-BN heterostructures are very useful as building blocks for nanodevices with desirable electronic properties.

Design and fabrication of three-dimensional (3D) ICs is one the newest and hottest trends in semiconductor manufacturing industry. In 3D ICs, multiple 2D silicon dies are stacked vertically, and through silicon vias (TSVs) are used to transfer power and signals between different dies. The electrical characteristic of TSVs can be modeled with equivalent circuits consisted of passive elements. In this thesis, we use “dummy” TSVs as electrical delay units in 3D SRAMs. Our results prove that dummy TSVs based delay units are as effective as conventional delay cells in performance, increase the operational frequency of SRAM up to 110%, reduce the usage of silicon area up to 88%, induce negligible power overhead, and improve robustness against voltage supply variation and fluctuation.

This recommended "time planner" has been included so that you have some idea of how much time you will need for each of the lessons. One of the aims of this package is to ensure that teachers do not have to deviate more than is necessary from their normal Std 8 lessons on the structure and function of cells. However, teachers are asked to include the following introductory exercises when they teach the section on the cell. Please emphasis strongly (to the pupils) that this is NOT extra work irrelevant to the syllabus. These lessons are to assist them to develop skills which are absolutely essential for them to succeed as biology scholars. Thereafter the teaching is left to the teacher. However, teachers are asked to incorporate the worksheets on cell organelles. and other relevant exercises, into those lessons in which they deal with those organelles. As teachers will realise. the active involvement of pupils in the learning task inevitably means that more time is spent teaching that section of work. Thus some of the tasks are for pupils to complete at home. Teachers are asked to ensure that pupils do complete these exercises, and that they have some sort of follow-up in class, even if it is merely a class display of drawings which have been done

Se comparó la estabilidad dimensional lineal de cuatro materiales para registro intermaxilar aprobados por la Asociación Dental Americana (ADA): Siliconas Occlufast y Futar D, Godiva y Cera Aluwax. Un dispositivo de acero fue fabricado según la especificación N° 19 de la ADA para obtener las muestras. En total se realizaron 80 muestras (20 por cada material) y se midieron utilizando un calibrador digital en diferentes intervalos de tiempo: al momento, a la hora, a las 24 horas, a los 7 días y a los 22 días. Los resultados fueron analizados usando análisis de varianza ANOVA no paramétrico con P≤0.05. Los resultados obtenidos mostraron que la cera Aluwax con respecto a la Godiva, Silicona Occlufast y Futar D, presentó una mayor variación dimensional lineal con un promedio de 0.22 mm al momento, 0.24 mm a los 7 días y 0.26 mm a los 22 días. La Silicona Futar D presento la mejor estabilidad dimensional lineal con respecto a los otros materiales para registro intermaxilar utilizados con un promedio de 0 mm al momento y que se mantuvo constante hasta los 22 días donde se observó una variación dimensional lineal de 0.03 mm. Se concluyó que todos los materiales utilizados varían dimensionalmente a través del tiempo. Siendo la silicona Futar D la que muestra menor distorsión con buena estabilidad dimensional a comparación con la silicona Occlufast, Godiva y cera Aluwax respectivamente. PALABRAS CLAVE Estabilidad Dimensional – Registro intermaxilar – Polivinilsiloxano / --- Lineal dimensional stability of four intermaxilar registry materials approved by American Dental Association (ADA) were compared: Occlufast silicon, Futar D silicon, impression compound, and Aluwax. An steel device was made according to the specification Nº 19 of the ADA in order to obtain the samples. A total of 80 samples were registered (20 for each material) and they were measured with a digital caliper at different time intervals: at the time, an hour after, 24 hours after, 7 days after, and 22 days after. The results were analyzed using an analysis of variance (ANOVA) not parametric with p≤0.05. The obtained results showed that the aluwax, in comparison with the other materials, presented the most lineal dimensional variation with a mean of 0.22mm at the moment, 0.24mm after 7 days, and 0.26mm after 22 days. The Futar D silicon presented the most lineal dimensional stability in comparison with the other intermaxilar registry materials used with a mean of 0mm at the moment, that kept its stability constant until the 22nd day, when a lineal dimensional variation of 0.03mm was observed. It was concluded that all the used materials vary dimensionally over time. Being the Futar D silicon the one that shows the least distortion with a good dimensional stability in comparison with Occlufast silicon, impression compound, and Aluwax respectively. KEYWORDS Dimensional Stability – Intermaxilar registry – Polyvinyl siloxane / Tesis

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Three Pt-based heterobimetallic lantern complexes of the form, [PtM(SAc)4(OH2)], M = Co (1), Ni (2), Zn (3), were prepared with thioacetate (SAc^-) bridging ligands that exhibit short Pt^...Pt interactions in the solid state. Three compounds with the form [PtM(SAc)4(3-NO2py)], M = Co (4), Ni (5), Zn (6) are formed upon reaction with 3-nitropyridine (3-NO2py) or alternatively the hydrated species 1--3 could be dehydrated to form the species [PtM(SAc)4], M = Co (7), Ni (8), Zn (9). Solid-state magnetism measurements indicate antiferromagnetic coupling of the paramagnetic 3d metal centers that can be attributed to the pathway established by the short Pt^...Pt contacts. Additional families of thiocarboxylate lantern complexes were prepared via the reaction of 1--3 or 7--9 with nitrogen or oxygen donor ligands. Reaction of 7--9 with pyridine yielded complexes with the form [PtM(SAc)4(py)2], M = Co (10), Ni (11), Zn (12). Complexes 10--12 could be thermally converted to the complexes [PtM(SAc)4(py)], M = Co (13), Ni (14), Zn (15) respectively. Reactions with the 4-aminopyridine ligand (amp) yielded exclusively monopyridyl species of the form [PtM(SAc)4(amp)], M = Co (16), Ni (17), Zn (18). O-donor solvents bind the dehydrated core [PtM(SAc)4] to give the complexes [PtCo(SAc)4(DMSO)](DMSO), 19, and [PtNi(SAc)4(DMF)](DMF), 20. Several diamagnetic complexes were prepared with the form [PtM(SOCR)4OH2], R = CH3, M = Mg (21); R = C6H5, M = Mg (22), Ca (23), and Zn (24) to examine the effect of the 3d metal on the electronic environment as determined by ^195Pt NMR. An additional family of complexes were prepared with pyrazine (pyz) linker ligands to form coordination polymers of the form [PtM(SAc)4(pyz)]n M = Co (25), Ni (26), Zn (27) and [PtM(SAc)4(pyz)0.5]2 M = Co (28), Ni (29), Zn (30). Two novel diplatinum complexes have been prepared with the 2,6-dimercaptopyridine (H2dmp) protoligand of the form [Pt2(Hdmp)4], 31, and [Pt2(phen)2(Hdmp)2], 32. Finally, a facile synthesis for ricinoleic acid, RA, coated ferrite spinel nanoparticles MFe2O4 · RA, M = Mn (33), Co (34), Ni(35), Zn(36) has been developed. The ferrite spinels were prepared hydrothermally and the synthesis and characterization of these nanoparticles will be discussed.

The competitiveness of conventional press & sinter technology mainly depends on the ability to obtain tight tolerance on sintered products. In order to maintain this strategic advantage in spite of the rapid global market changes, a continuous improvement in the dimensional accuracy of the products has to be pursued. One of the major limits in the dimensional precision of sintered products regards the anisotropic dimensional change occurring on sintering. Despite this problem is well known, an effective design procedure accounting for the anisotropic behavior of dimensional variations is far to be reached. The main reasons concern the multiphysical mechanisms involved and the effect of material, geometry and process condition on the final results. This work aims at developing a design methodology accounting for the anisotropy of dimensional changes on sintering. This study has been performed considering both the fundamental principles and the industrial application, aiming at proposing: - a solid theory considering the mechanisms which determine the anisotropic dimensional changes; - a practical and effective design tool for the industrial application. The role of uniaxial compaction on the origin of anisotropic dimensional change was firstly investigated. AISI 316L ring shaped samples were compacted at different geometries, and four different particle sizes. During single action compaction, forces acting on the tooling and powder column, and related displacements, were recorded by the press in order to derive the compaction mechanics of the powder mixes. Further, the dimensions of the samples were measured before and after sintering. A linear trend was observed correlating the deviatoric stresses occurring in compaction to the anisotropic dimensional variations on sintering. This result offers a new perspective in the prediction of the anisotropic dimensional change, and could lay the foundation of a solid model. Aiming at developing an effective design tool to predict dimensional change on sintering, the analytical design procedure previously developed by the research group at the University of Trento was validated on real parts. A Club Project was promoted by EPMA, collecting the University of Trento and five qualified industrial partners. These companies provided five different real parts characterized by different materials and geometries, whose dimensions were measured before and after sintering. The comparison of the measured and the predicted sintered dimensions demonstrated that this design approach can be an effective tool for designers. Further work could implement the promising results obtained investigating the compaction mechanics in the design procedure, aiming at defining a powerful tool to design PM parts accounting for anisotropic dimensional changes.

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Multi-dimensional functions are characterized by a large number of parameters on which the functional value depends. They are commonly used in engineering problems such as image analysis and system modeling. Multi-dimensional function spaces are very difficult to understand due to their multi-dimensional nature and the presence of a large number of data points in the functional space. A point called the focal point is selected by the user in the vast multi-dimensional parameter space. Rays called "focal rays" emanate from the focal point in all directions to the boundaries of the functional space. The focal rays contain functional data points. The focal point is mapped onto the center of the visualization with the focal rays arranged radially around it. The degree of detail decreases as we move away from the focal point toward the edges of the visualization in accordance with the focus+context technique. The functional values are mapped onto a color scheme with shades of green representing positive function values, and shades of red representing negative function values. Interactive features such as the ability to change the focal point, highlighting of functional values aid the user in exploring and analyzing the functional space. The algorithm, practical applications of the visualization approach and results of formative evaluation studies are also elaborated in this thesis. The contributions of this thesis are fourfold, namely, providing an overview of the functional space, equal treatment of all dimensions, improved scalability and a smooth blending of details with the overview. / Master of Science