Electron Beam Chemical Vapor Deposition (EBCVD) is a process by which an electron beam is used to decompose adsorbed reagent molecules to produce a deposit. The primary electrons from the beam, and especially the secondary electrons emitted from the substrate, dissociate the adsorbed molecules. Important factors for the deposition process include the beam parameters and reagent gas composition. Simple structures are fabricated through utilization of the various scanning modes of an SEM. Fibers (pillar-like structures) can be deposited, and lines (wall-like structures) can be deposited easily. This investigation focuses on the process parameters controlling deposition rate and geometry for platinum and carbon fibers and lines in a modified SEM. Platinum deposition was performed using a system with a small diameter needle that supplied a localized flow of gas from an organometallic platinum compound. Carbon deposition was performed in the Environmental mode, in which the microscope chamber is filled with a specified pressure of reagent gas. Statistically designed experiments were performed for platinum fiber and line deposition. Analysis indicated that the beam current and deposition time were dominant factors in determining the deposition rate. The voltage also had a significant effect on fiber deposition. For platinum line deposition, the effects of the dwell time and line time were also studied. The line time had a significant effect on line height deposited per scan. Optimization analysis was performed, and results indicated that high voltage and high beam current led to higher aspect ratios. Medium voltage and low beam current were preferable for depositing minimal width lines (less than 200 nm). Low voltage and high beam current were preferable for maximum deposition rates. EDS and EELS performed for platinum deposits in a TEM indicated amorphous structure with no carbon detected. This differs significantly from previously reported results. Statistically designed experiments were performed for carbon line deposition. The voltage, beam current, and dwell/line time were studied. Increasing line time led to a significant increase in line height/scan and appeared to be a dominant factor. Lower beam currents appeared to favor higher deposition rates. TEM analysis indicated that carbon deposits were mostly amorphous.

In this study, the structures of two ultrathin Pd nanowires were predicted by the simulated annealing basin-hopping method (SABH) with the tight-binding potential. The thermal stability of the Pd wires and adsorption, dissociation and diffusion behaviors were further examined by the density functional theory (DFT) calculation and DFT molecular dynamics (DFT-MD) simulation. In terms of thermal stability, these two Pd nanowires are still very stable at temperatures as high as 400 K. The configurations and adsorption energy have been calculated for H atom and H2 molecular adsorption on Pd nanowires. The minimum energy pathways and transition states of H2 molecular dissociation and H atom diffusion process on Pd nanowires were studied by the nudged elastic band (NEB) method. For the dissociation of hydrogen molecules, results show the dissociation is almost barrierless so the dissociation is easy to occur at very low temperatures, and their catalytic reactivity is very similar to the Pd bulk material. The thermal stability of the H atom within these Pd nanowires were also investigated by DFT-MD, with results showing that the H atom can only stay within Pd nanowires at temperatures much lower than room temperature (298 K). This phenomenon is very different from that of H atoms within Pd bulk material or other reported nanomaterials, leading to hydrogen embrittlement. Our results reveal that these two ultrathin Pd nanowires not only possess the same excellent catalytic activity for hydrogen molecules as the bulk Pd materials or other Pd nanomaterials do, but also avoid the hydrogen embrittlement occur.

In this work, the doping processes of the SA type stepped Ge (100) surface by arsine (AsH3) and diborane (B2H6) gas flow have been simulated seperately by the possible adsorption and dissociation models. The most stable adsorption and dissociation models of AsH3 and B2H6 on stepped Ge(100) surface have been determined by the local minimum total energy and/or binding energy calculations based on Hartree-Fock Theory. The present calculations have shown that, the step region (both up and down terraces) of the stepped Ge (100) surface has the most attractive sites for the initial adsorption stages of the gas molecules. It has been found that the thermodynamically preferred structures in the dissociation paths of arsine and diborane are the same / AsH3 , BH3 (fragment of diborane), AsH2 and BH2 products prefer to be bounded to a single surface Ge atom, but AsH and BH prefer to be bridged between two adjacent surface Ge atoms. It has been also found that, at the first step of the adsorptions, AsH3 can only dissociate to AsH2, but BH3 can dissociate to both BH2 and BH. This remarkable result has showed that dissociation of BH3 on Ge(100) surface can be easier than AsH3&rsquo / s. According to the optimization calculations, the dissociation path has started with the adsorption of AsH3 (or BH3) on the electron deficient side (buckled down) of the Ge dimer bond and ended with the occupation of the empty Ge sites in the surface layers by As (or B) atom substitutionally. In the present work, the beginning of the n &ndash / (or p-) type doping of the stepped Ge(100) surface has been illustrated by the As (or B) electronic states obtained in the optical energy gap of Ge very close to HOMO (or LUMO) energy edge.

Thèse de doctorat : Électronique : Lille 1 : 2002. / N° d'ordre (Lille) : 3104. Résumé en français. Textes en français et en anglais. Notes bibliogr.

Tez (Doktora) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Kimya Anabilim Dalı, 2007. / Kaynakça var.

The weakly bound association products of atmospherically relevant radical species (O₂, OH, NO₂, HO₂ and NO) have been studied theoretically using quantum-chemical methods. The thermodynamic stabilities, which are crucial to determining the probability of formation in Earth's atmosphere, were calculated for the hydrotrioxy radical (HOOO) and peroxynitrous acid (HOONO, an isomer of nitric acid) relative to the radical dissociation products. In the case of HOONO, the experimentally determined values were confirmed. For HOOO, the predicted stability was significantly lower than the experimentally determined value; a conclusion that was supported by later experimental work and indicates that HOOO will not form in significant quantities in Earth's atmosphere. The fundamental and multi-quantum vibrational transitions were also predicted for both the HOONO and HOOO systems. The theoretical work on the HOONO system aided the assignment of experimental spectra and was used to correct equilibrium rotational constants. The HOOO system presented a challenge for the methods used here and work to apply other approaches in describing the vibrational modes is ongoing. Second-order vibrational perturbation theory, combined with a correlated quantum-chemical method and a moderately sized basis set, provides a method for accurately predicting fundamental and low-order multi-quantum transition energies and intensities for many systems (HOOO being an exception). Here coupled cluster theory, at a level which treats one- and two-electron correlation with a correction for three-electron correlation, and atomic natural orbitals basis sets were used in the vibrational calculations. To predict the dissociation energies of weakly bound species with the precision required (due to the small energy differences involved), high-order correlation contributions (a full treatment of three-electron correlation and a correction for four-electron correlation) are included, as is extrapolation to the basis set limit. Other contributions, such as that for the zero-point energy, were also considered. For the HOOO system, one-dimensional potential curves along the dissociation and torsional coordinates were constructed with standard single-reference and equation-of-motion coupled-cluster methods. The latter is better able to describe the nature of a system in the bond-breaking region and the complex electronic structure of a species formed from two radical fragments, one doubly degenerate in the ground state: X²[Pi] OH and X³[Sigma] O₂. A possible barrier to dissociation and the torsional potential for HOOO were investigated. / text

The surface-induced dissociation (SID) method is introduced into a Bruker matrix-assisted laser desorption/ionization time-of-flight mass spectrometer (MALDI TOF MS) as an efficient ion fragmentation method. Ion trajectory calculations using the SIMION 7.0 ion optics program are performed and results are combined with simple unimolecular decay calculations in order to study the kinetics of the SID processes. In this instrument, the observation time frame for SID fragments lies in the submicrosecond region, allowing the specific detection of submicrosecond fragmentation channels. MALDI-produced protonated peptides in the mass range of 700 - 1500 Da and radical ions produced by laser irradiation of fullerenes C60 and C70 are fragmented at a gold surface coated with a self-assembled monolayer of alkanethiol to obtain TOF SID TOF mass spectra. For the SID of peptides in the hyperthermal energy regime, a fragmentation time frame of tens to a few hundreds of nanoseconds was calculated for the observed fast fragmentation channels (Chapters 3 and 4). Theoretical and experimental peak shape comparisons assuming unimolecular decay kinetics indicated a log rate constant in the range 6 - 7 (Chapter 4). Energy and mass resolved kinetic studies are also carried out. The contribution of special structural features to peptide fragmentation and the possibility of different fragmentation mechanisms such as sequential and parallel pathways are investigated. The results indicate a unimolecular decay process for observed fast peptide fragments ruling out a surface-shattering mechanism. Fullerene ions, especially C60+., showed a fragmentation behavior producing C2n+. fragments with an even number of C units at collision energies in the range of 100 - 400 eV (Chapter 5). At around 400 eV, additional small fragments appeared that are apart by only a single C unit. According to the calculated fragmentation times and the theoretical and experimental peak shape comparisons assuming unimolecular decay kinetics, both these processes may be approximated by parallel fast unimolecular decay processes with fragmentation time frames of tens to hundreds of nanoseconds although the poor theoretical and experimental peak shape matching for example in the decay of C60+. to C19+. may suggest deviations from a one-step unimolecular decay process.

Research presented in this dissertation falls into two parts: fragmentation mechanisms of peptide and fragmentation mechanism of amino acid derivatives. The study of peptide fragmentation may help to improve protein identification by incorporating the rules governing this process into search algorithms. This study elucidates the chemical 'rules' governing peptide dissociation. It is believed that these 'rules' can be incorporated into searching algorithms to achieve better protein identification. The present study focuses on the effects of different amino acids on fragmentation. Amino acids with a wide range of different chemical and physical properties are investigated, including amino acids with hydrophilic side chains, amino acids with aliphatic side chains and amino acids without side chains. It can be concluded from the present studies that the different amino acid properties have great influence on the peptide fragmentation and spectrum appearance.The study of fragmentation mechanisms of amino acid derivatives is another focus of this dissertation. Based on the fragmentation mechanism study, a quantification method was developed. The method can distinguish glutamine with 15N-label at N-terminal amine vs the side chain even if they have same molecular weight. Ammonia metabolism was successfully monitored by feeding mosquitoes with isotope-labeled compounds and subsequently measuring the amount of the labeled amino acids. This method demonstrates the power of mass spectrometry in metabolism studies.

Awareness due to increase crime has highlighted the occurrence of immense personal and social problems. Problems resulting from disorders such as Schizophrenia, Alzheimer's and Dissociative Identity Disorder (DID) are less common but have a profound impact on all of us. Research has shown that 97% of people with severe abuse and life trauma before the age of nine, develop DID. The objective of this study was to investigate (from the perspectives of therapists) the experience of people diagnosed with Dissociative Identity Disorder (DID) in the workplace. A qualitative research design was used to capture the essence of the individual's experience thereby enabling the researcher to develop an understanding from the participant's point of view. In this study seven therapists were interviewed and each completed a questionnaire. This was the basis used to demonstrate the typical behaviour of DID in the workplace. The results indicated that DIDs cope to a certain extent but tend to switch (switching) personalities when exposed to trauma, stress or events that triggers past life trauma. Defense mechanisms and switching can have a negative influence on the organisation and its employees, but most of all on the DID. If professional treatment is available, the condition can be fully cured. Most patients treated were female, averaged 29 years of age, were single, and had experienced some kind of abuse. Patients experienced problems directly related to DID, such as lack of concentration, attention deficiency and memory loss, depression, migraine and constant headaches. Their behaviour is inconsistent and unpredictable, and they experience relationship problems. Results show that DIDs can hold relatively senior positions but tend to change jobs on a regular basis. Although this condition can be differentiated from other Psychological conditions, most DIDs have previously been misdiagnosed. A Psychological-based paradigm is mostly used to diagnose the condition. Recommendations to the organisation (especially to the HR department) and recommendations for future research were made. / Thesis (M.Com. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2004.

Laboratory tests have been performed using a stirred cell where SI and SII gas hydrates have been formed under the presence of the kinetic inhibitor Poly Vinyl Caprolactam (PVCap) and INHIBEX. The latter is a mixture containing 50wt% PVCap 2k and 50wt% butyl glycol. The effect of PVCap is enhanced by the presence of butyl glycol; the latter acts as a synergist for the former. Dissociation temperatures were obtained and compared for hydrates formed 1) in presence of PVCap and 2) in presence of INHIBEX. The effect of INHIBEX concentration on the temperature of dissociation was also investigated. Systems containing INHIBEX dissociated at lower temperatures than the corresponding systems with only PVCap present. Furthermore, 3000 ppm INHIBEX mixtures were found to have higher dissociation temperatures than 1500 ppm INHIBEX mixtures.