Thesis--Auburn University, 2009. / Abstract. Includes bibliographic references (p.83-85).

published_or_final_version / Chemistry / Master / Master of Philosophy

Thesis (M.S.)--University of Missouri-Columbia, 2007. / 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 March 19, 2008) Includes bibliographical references.

Thesis (MTech (Mechanical Engineering))--Cape Peninsula University of Technology, 2016. / The purpose of this study is the optimisation of the stamping analysis process in order to investigate the possible reasons for the part failure. (Altan & Vasquez, 2000) have conducted similar research to optimise a forming process. However, they focussed on dies for a forging process and in this study, we are looking at cold forming and this study is also different in that we are trying to reduce the number of stages while maintaining the formability. Formability is based on the dimensional conformance of the final part with additional criteria being the thinning, appearance of wrinkling, dynamic effects leading to the localisation of strain, cracking and residual stress. A numerical modelling procedure that is close enough to the real process is used to investigate the effects of changes in the frictional contact that would correspond to lubrication and also the effect of adding draw beads to the forming tools to change the frictional contact. We also investigated the effect of using a different material in terms of meeting the design requirements. Experimental results for comparison are available for certain of the stamping processes investigated that were tested in pre-production. The finite element simulation is used to account for all residual thinning, stress and strain of the multi-stage forming process to ensure optimum thickness changes of the sheet at each stage. The variations of material and manufacturing parameters are established to accurately predict the behaviour of this specific forming process. The material model required to meet physical experiments is deduced from the results of standard tensile tests and fitted to the Hill’s 48 Law for Work Hardening. The commercial packages Ls-Dyna with Dynaform and Pam-Stamp software are used for the simulation to produce 2 results for comparison.

No description available.

Histopathology studies of metal nanoparticles (NPs) compared to traditional forms of metal in fish are scarce. Additionally, it is unclear whether metal nanoparticles cause greater or different pathologies compared to other forms of metal. The current study aimed to assess the pathological effects of Cu-NPs and TiO2 NPs on rainbow trout via various routes of exposure and, where appropriate, to compare them to either the equivalent dissolved metal salts or bulk powder forms. The first experiment showed that waterborne exposure to Cu-NPs and CuSO4 caused similar types of organ pathologies and alteration in the spleen content, however there were some material-type effects in the incidence injuries; with Cu-NPs in some organs by causing more injury in the intestine, liver, and brain when compared to effects caused by the equivalent concentration of CuSO4. Lowering water pH did have an effect on the toxicity of Cu-NPs and dissolved Cu in trout, and the results illustrated that both Cu treatments are more toxic at pH 5 than pH 7 by causing more physiological and pathological changes, although both CuSO4 and Cu-NP treatments showed similar types of organ lesions. Waterborne exposure to TiO2 NPs and bulk forms of TiO2 showed similar types of organ pathologies and alteration in the spleen contents, but there was a material-type effect in some organs (more injury with the bulk treatment than the NP form). After 96 h following intravenous injections of bulk or TiO2 NPs in trout, organs showed similar types of pathologies; except the spleen and kidney which showed a material-type effects (more injury with NPs than the bulk forms). This could be attributed to the highest Ti accumulation from the TiO2 NP treatment in the kidney and spleens, or to the role of these organs in filtrating the circulating blood. Overall, this thesis demonstrates that metal-NPs produced similar types of organ pathologies to traditional forms of metals through different routes of exposure, but there were some material-type effects on the incidence of injuries in some organs. The results have also added some understanding on the fate, and effects of NPs by identifying the target organs involved. Some of the nano-specific effects may need to be given extra consideration in environmental and human health risk assessments.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

Principles involving the electronic structure of group VI metal-metal multiple bonded complexes are examined in order to provide insights into the intramolecular and intermolecular interactions of these systems. Examination of chromium, molybdenum and tungsten tetracarboxylate thin films by ultraviolet photoelectron spectroscopy has provided the first experimental evidence for the location of the σ ionization in dimolybdenum tetracarboxylate quadruple bonded complexes. These compounds have significant intermolecular interactions as thin films which destabilizes ionization of the valence σ state, allowing it to be experimentally observed. This is supported by the observed destabilization of the σ ionization feature of the ditungsten analogue in going to the thin film. The Cr₂(O₂CCH₃)₄ comparison shows a destabilization of the leading predominantly metal ionizations consistent with the broad range of M-M bond lengths observed for Cr₂ complexes. The Group VI M₂(mhp)₄ and M₂(chp)₄ [mhp=6-methyl-2-oxo-pyridine and chp=6-chloro-2-oxo-pyridine] complexes are also examined. The geometric constraints imposed on the compounds by the ligand effectively block intermolecular interaction axial to the metal-metal bond in the solid state. Comparison of the two ligand spectra, Hmhp and Hchp, has provided a unique opportunity to assign ionizations previously attributed to the keto form of the Hmhp tautomers. The spectra of the complexes exhibit minimal relative shifting of ionization features in going to the thin films because of this constraint. A band previously believed to be due to spin orbit coupling is assigned to the σ ionization in the ditungsten complex. The overall ionization band profiles of the two series correlate well, metal by metal, with the expected shifting due to substitution of the more electronegative chlorine atoms for a methyl group. The synthesis and characterization of Mo₂(N-t-butyl-acetamide)₄, the first tetraamidodimetal compound without large rings with delocalized pi structure, is described. The single crystal X-ray structure is presented, revealing the novel (one of three examples) cis configuration of the MoN₂O₂ ligand set. The Mo-Mo bond length of 2.063 Å is one of the shortest seen to date. A preliminary gas phase He I valence spectrum is reported.

This dissertation describes the experimental study of the electronic-structural relationships of selected mononuclear transition-metal sulfur dioxide, cyclopentadienyl and carbonyl complexes and the application of the information gained from these to the study of quadruply-bonded dimetallic complexes. These pertinent observations result from the application of photoelectron spectroscopy (p.e.s.) as a probe into the bonding, charge-distribution and excited state effects which contribute to the specifics of the ground and excited state molecular structures. The first part of this discussion centers around a specific study of the exemplary bonding probe, SO₂, with the well characterized ArM(CO)₂ metal fragment, where Ar = Bz and Cp and M = Cr, Mn and Re. A comparison of the ionization information with the structural details and molecular orbital calculations reveals not only the surprising coordinating similarity of SO₂ and CO in these complexes, but also the electronic origin for the counter-intuitive SO₂ bonding configuration. This work then moves to a more dramatic example of electronic control of ground state molecular structure; the crystallographically determined distortion of the coordinated Cp ring in Cp*Rh(CO)₂. The electronic origin of this distortion is graphically shown with the aid of two and three dimensional experimental and theoretical electron density maps. The structural effects of removing bonding electrons from quadruply-bonded dimetallic complexes is then investigated. This study incorporates the use of high-resolution p.e.s. for the novel observations of metal-metal vibrational structure in the predominantly metal ionizations providing direct information of the bonding influence of specific metal electrons. Particular attention is focused on the delta-ionization process of MO₂(O₂CCH₃)₄. The final chapter presents a comprehensive study of the valence and core ionizations of the series of quadruply-bonded M₂(X₂CR)₄ complexes, where M₂ = Cr₂, Mo₂, MoW, and W₂, X = O and S, and R = H, CH₃, CD₃, CF₃, CH₂CH₃, CH₂CH₂CH₃ and C(CH₃)₃. The changes in the electronic structure in both the ground and excited states of these molecules is presented and, where appropriate, compared to structural changes. The study of this series not only demonstrates how p.e.s. can be used to monitor the electronic effects of specific chemical modifications, but also reveals surprising excited state features related to facile charge-reorganization processes.