Zirconia for teeth and implants

This case series reports on the use of nonsilica-based high-strength full ceramics for different prosthetic indications. Fifty-two consecutive patients received tooth- or implant-supported zirconia reconstructions during a 2-year period. The observation period for reexamination was 12 to 30 months. The most frequent indications were single crowns and short-span fixed partial dentures. A few implant superstructures were screw-retained, whereas all remaining restorations were cemented on natural teeth or zirconia implant abutments. Clinical examination included biologic (probing depths, bleeding on probing) and esthetic (Papilla Index) parameters, as well as technical complications. No implant was lost or caused any problems, but two teeth were lost after horizontal fracture. Overall, the periodontal parameters were favorable. Fractures of frameworks or implant abutments were not observed. Abutment-screw loosening occurred once for one premolar single crown. Furthermore, five implant crowns in the posterior region exhibited chipping of the porcelain veneering material. With regard to esthetics, no reconstructions were considered unacceptable, but three crowns were remade shortly after delivery. In this short-term study, it was observed that biologic, esthetic, and mechanical properties of zirconia were favorable, and the material could be used in various prosthetic indications on teeth or implants.

Performance evaluation of VIP latrines in the Upper West Region of Ghana

The prevalence of Ventilated Improved Pit (VIP) latrines in Ghana suggests that the design must have a high user acceptance. The two key factors attributed to user acceptance of a VIP latrine over an alternative latrine design, such as the basic pit latrine, are its ability to remove foul odors and maintain low fly populations; both of which are a direct result of an adequate ventilation flow rate. Adequate ventilation for odorless conditions in a VIP latrine has been defined by the United Nations Development Program (UNDP) and the World Bank, as an air flow rate equivalent to 6 air changes per hour (6 ACH) of the superstructure’s air volume. Additionally, the UNDP determined that the three primary factors that affect ventilation are: 1) wind passing over the mouth of the vent pipe, 2) wind passing into the superstructure, and 3) solar radiation on to the vent pipe. Previous studies also indicate that vent pipes with larger diameters increase flow rates, and the application of carbonaceous materials to the pit sludge reduces odor and insect prevalence. Furthermore, proper design and construction is critical for the correct functioning of VIP latrines. Under-designing could cause problems with odor and insect control; over-designing would increase costs unnecessarily, thereby making it potentially unaffordable for benefactors to independently construct, repair or replace a VIP latrine. The present study evaluated the design of VIP latrines used by rural communities in the Upper West Region of Ghana with the focus of assessing adequate ventilation for odor removal and insect control. Thirty VIP latrines from six communities in the Upper West Region of Ghana were sampled. Each VIP latrine’s ventilation flow rate and micro-environment was measured using a hot-wire anemometer probe and portable weather station for a minimum of four hours. To capture any temporal or seasonal variations in ventilation, ten of the latrines were sampled monthly over the course of three months for a minimum of 12 hours. A latrine usage survey and a cost analysis were also conducted to further assess the VIP latrine as an appropriated technology for sustainable development in the Upper West Region. It was found that the average air flow rate over the entire sample set was 11.3 m3/hr. The minimum and maximum air flow rates were 0.0 m3/hr and 48.0 m3/hr respectively. Only 1 of the 30 VIP latrines (3%) was found to have an air flow rate greater than the UNDP-defined odorless condition of 6 ACH. Furthermore, 19 VIP latrines (63%) were found to have an average air flow rate of less than half the flow rate required to achieve 6 ACH. The dominant factors affecting ventilation flow rate were wind passing over the mouth of the vent pipe and air buoyancy forces, which were the effect of differences in temperature between the substructure and the ambient environment. Of 76 usable VIP latrines found in one community, 68.4% were in actual use. The cost of a VIP latrine was found to be equivalent to approximately 12% of the mean annual household income for Upper West Region inhabitants.

Design of artificial myocardial microtissues

Cultivation technologies promoting organization of mammalian cells in three dimensions are essential for gene-function analyses as well as drug testing and represent the first step toward the design of tissue replacements and bioartificial organs. Embedded in a three-dimensional environment, cells are expected to develop tissue-like higher order intercellular structures (cell-cell contacts, extracellular matrix) that orchestrate cellular functions including proliferation, differentiation, apoptosis, and angiogenesis with unmatched quality. We have refined the hanging drop cultivation technology to pioneer beating heart microtissues derived from pure primary rat and mouse cardiomyocyte cultures as well as mixed populations reflecting the cell type composition of rodent hearts. Phenotypic characterization combined with detailed analysis of muscle-specific cell traits, extracellular matrix components, as well as endogenous vascular endothelial growth factor (VEGF) expression profiles of heart microtissues revealed (1) a linear cell number-microtissue size correlation, (2) intermicrotissue superstructures, (3) retention of key cardiomyocyte-specific cell qualities, (4) a sophisticated extracellular matrix, and (5) a high degree of self-organization exemplified by the tendency of muscle structures to assemble at the periphery of these myocardial spheroids. Furthermore (6), myocardial spheroids support endogenous VEGF expression in a size-dependent manner that will likely promote vascularization of heart microtissues produced from defined cell mixtures as well as support connection to the host vascular system after implantation. As cardiomyocytes are known to be refractory to current transfection technologies we have designed lentivirus-based transduction strategies to lead the way for genetic engineering of myocardial microtissues in a clinical setting.

Structure and thermal stability of Langmuir-Blodgett films of barium arachidate

The structures of multilayer Langmuir-Blodgett films of barium arachidate before and after heat treatment have been investigated using both atomic force microscopy (AFM) and grazing incidence synchrotron X-ray diffraction (GIXD). AFM gave information on surface morphology at molecular resolution while GIXD provided quantitative details of the lattice structures of the films with their crystal symmetries and lattice constants. As-prepared films contained three coexisting structures: two triclinic structures with the molecularchains tilted by about 20degrees from the film normal and with 3 x 1 or 2 x 2 super-lattice features arising from height modulation of the molecules in the films; a rectangular structure with molecules perpendicular to the film surface. Of these, the 3 x 1 structure is dominant with a loose correlation between the bilayers. In the film plane both superstructures are commensurate with the local structures, having different oblique symmetries. The lattice constants for the 3 x 1 structure are a(s) = 3a = 13.86 Angstrom, b(s) = b = 4.31 Angstrom and gamma(s) = gamma = 82.7degrees; for the 2 x 2 structure a(s) = 2a = 16.54 Angstrom, b(s) = 2b = 9.67 Angstrom, gamma(s) = gamma = 88degrees. For the rectangular structure the lattice constants are a = 7.39 Angstrom, b = 4.96 Angstrom and gamma = 90degrees. After annealing, the 2 x 2 and rectangular structures were not observed, while the 3 x 1 structure had developed over the entire film. For the annealed films the correlation length in the film plane is about twice that in the unheated films, and in the out-of-plane direction covers two bilayers. The above lattice parameters, determined by GIXD, differed significantly from the values obtained by AFM, due possibly to distortion of the films by the scanning action of the AFM tip. (C) 2004 Published by Elsevier B.V.

Meeting the challenge on the path to democracy: discursive strategies in governmental declarations

The communicative practice in the ex-GDR was complex and diverse, although public political discourse had been fairly ritualized. Text-types characteristic of the Communist Party discourse were full of general (superordinate) terms semantic specification was hardly possible (propositional reduction). Changes in the social world result in changes in the communicative practice as well. However, a systematic comparision of text-types across cultures and across ideological boundaries reveals both differences in the textual macro- and superstructures and overlapping as well as universal features, probably related to functional aspects (discourse of power). Six sample texts of the text-type `government declaration', two produced in the ex-GDR, four in the united Germany, are analysed. Special attention is paid to similarities and differences (i) in the textual superstructure (problem-solution schema), (ii) in the concepts that reflect the aims of political actions (simple worlds), (iii) in the agents who (are to) perform these actions (concrete vs abstract agents). Similarities are found mainly in the discursive strategies, e.g. legitimization text actions. Differences become obvious in the strategies used for legitimization, and also in the conceptual domains referred to by the problem-solution schema. The metaphors of construction, path and challenge are of particular interest in this respect.

On the microstructure, growth pattern and original porosity of belemnite rostra: insights from calcitic Jurassic belemnites

Calcitic belemnite rostra are usually employed to perform paleoenvironmental studies based on geochemical data. However, several questions, such as their original porosity and microstructure, remain open, despite they are essential to make accurate interpretations based on geochemical analyses.This paper revisits and enlightens some of these questions. Petrographic data demonstrate that calcite crystals of the rostrum solidum of belemnites grow from spherulites that successively develop along the apical line, resulting in a “regular spherulithic prismatic” microstructure. Radially arranged calcite crystals emerge and diverge from the spherulites: towards the apex, crystals grow until a new spherulite is formed; towards the external walls of the rostrum, the crystals become progressively bigger and prismatic. Adjacent crystals slightly vary in their c-axis orientation, resulting in undulose extinction. Concentric growth layering develops at different scales and is superimposed and traversed by a radial pattern, which results in the micro-fibrous texture that is observed in the calcite crystals in the rostra.Petrographic data demonstrate that single calcite crystals in the rostra have a composite nature, which strongly suggests that the belemnite rostra were originally porous. Single crystals consistently comprise two distinct zones or sectors in optical continuity: 1) the inner zone is fluorescent, has relatively low optical relief under transmitted light (TL) microscopy, a dark-grey color under backscatter electron microscopy (BSEM), a commonly triangular shape, a “patchy” appearance and relatively high Mg and Na contents; 2) the outer sector is non-fluorescent, has relatively high optical relief under TL, a light-grey color under BSEM and low Mg and Na contents. The inner and fluorescent sectors are interpreted to have formed first as a product of biologically controlled mineralization during belemnite skeletal growth and the non-fluorescent outer sectors as overgrowths of the former, filling the intra- and inter-crystalline porosity. This question has important implications for making paleoenvironmental and/or paleoclimatic interpretations based on geochemical analyses of belemnite rostra.Finally, the petrographic features of composite calcite crystals in the rostra also suggest the non-classical crystallization of belemnite rostra, as previously suggested by other authors.

State-of-the-Art Methods for Design of Integral Bridge Abutments, HR-227, 1981

The routine use of integral abutments to tie bridge superstructures to foundation piling began in this country about 30 years ago. Kansas, Missouri, Ohio, North Dakota, and Tennessee were some of the early users. This method of construction has steadily grown more popular. Today more than half of the state highway agencies have developed design criteria for bridges without expansion joint devices.

Study of Tsunami-Induced Fluid and Debris Load on Bridges using the Material Point Method

Thesis (Ph.D.)--University of Washington, 2016-08

Self-assembly of gold nanocrystals into discrete coupled plasmonic structures

Development of methodologies for the controlled chemical assembly of nanoparticles into plasmonic molecules of predictable spatial geometry is vital in order to harness novel properties arising from the combination of the individual components constituting the resulting superstructures. This paper presents a route for fabrication of gold plasmonic structures of controlled stoichiometry obtained by the use of a di-rhenium thio-isocyanide complex as linker molecule for gold nanocrystals. Correlated scanning electron microscopy (SEM)—dark-field spectroscopy was used to characterize obtained discrete monomer, dimer and trimer plasmonic molecules. Polarization-dependent scattering spectra of dimer structures showed highly polarized scattering response, due to their highly asymmetric D∞h geometry. In contrast, some trimer structures displayed symmetric geometry (D3h), which showed small polarization dependent response. Theoretical calculations were used to further understand and attribute the origin of plasmonic bands arising during linker-induced formation of plasmonic molecules. Theoretical data matched well with experimentally calculated data. These results confirm that obtained gold superstructures possess properties which are a combination of the properties arising from single components and can, therefore, be classified as plasmonic molecules