Thesis (M.S.)--Michigan State University. Dept. of Physics, 2008. / Adviser, Prof. Georg Bollen"--Acknowledgments. Title from PDF t.p. (viewed on Aug. 4, 2009) Includes bibliographical references (p. 71-72). Also issued in print.

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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A mamoneira (Ricinus communis) à uma oleaginosa com valor econÃmico considerÃvel devido à composiÃÃo do Ãleo de suas sementes. No entanto, hà algumas limitaÃÃes no seu uso para alimentaÃÃo humana e animal devido à presenÃa de proteÃnas tÃxicas e alergÃnicas, as quais podem ser solucionadas ou minimizadas atravÃs da engenharia genÃtica. Contudo, essa cultura à recalcitrante para tÃcnicas de cultura de tecidos limitando a geraÃÃo de plantas transformadas e os protocolos existentes nÃo sÃo bem estabelecidos. O objetivo desse trabalho foi avaliar a aplicabilidade de um protocolo de regeneraÃÃo existente na literatura à cultivar Nordestina; determinar a via de regeneraÃÃo e avaliar, atravÃs de tÃcnicas histoquÃmicas, as cÃlulas transformadas por biobalÃstica em torno do meristema. Para este propÃsito, eixos embrionÃrios foram cultivados em meio Murashig and Skoog (MS) suplementado com concentraÃÃes crescentes de tidiazuron (TDZ) (0,1; 0,5; 1,0; 2,0; 5,0 e 10,0 mg.L-1). Observou-se que entre as concentraÃÃes de TDZ avaliadas a que apresentou a melhor resposta foi 0,1 mg.L-1, apresentando, em mÃdia, apÃs 56 dias de incubaÃÃo,7,42 partes aÃreas por explante. Ãcido giberÃlico (0,1 mg.L-1) e Ãcido-indol-3 butÃrico (1,0 mg.L-1) foram utilizados na tentativa de alongar e promover o enraizamento, respectivamente, das partes aÃreas obtidas, contudo, nas concentraÃÃes utilizadas, nÃo evidenciou-se nenhum efeito com estes reguladores de crescimento. AnÃlises histolÃgicas revelaram que as partes aÃreas foram formadas de meristemas prÃ-existentes e neo-formados indicando organogÃnese direta. Observaram-se cÃlulas transformadas pelo menos atà a segunda camada celular. AnÃlises da expressÃo estÃvel do gene gus mostraram expressÃo do mesmo, 19 dias apÃs o bombardeamento. Nas anÃlises histolÃgicas foram observadas cÃlulas transformadas em divisÃo. Como conclusÃo a cultivar Nordestina foi capaz de formar mÃltiplas partes aÃreas em meio contendo TDZ e este protocolo de regeneraÃÃo foi compatÃvel com um protocolo de transformaÃÃo por biobalÃstica / Castor bean (Ricinus communis) is an oilseed crop with considerable economic value because of the composition of its oil seed. However, there are some constraints in your use for human and animal food because of the presence of toxic and allergenic proteins. This problem could be solved or reduced through genetic engineering. However, this crop is recalcitrant to tissue culture techniques, thus limiting the formation of transformed plants, and the protocols existing are not well established. The aim of this work was to test the applicability of the regeneration protocol which has been published for the Nordestina cultivar; to determine the regeneration way and to verify trough histochemical techniques, the transformed cells around the meristem. For this purpose, embryo axes were cultured on Murashig and Skoog (MS) medium supplemented with thiadiazuron (TDZ) (0,1; 0,5; 1,0; 2,0; 5,0 e 10,0 mg.L-1). Between the TDZ concentrations tested, 0,1 mg.L-1 presented the better results after 56 days of incubation with 7,42 shoots per explant. Gibberellic acid (GA3) (0,1 mg.L-1) and indole-3-butyric acid (1,0 mg.L-1) were used for elongation and rooting, respectively, of the shoots obtained, however, in the concentrations used, any effect was evidenced. Histological analysis revealed that the shoots were formed by pre existing or neo formed meristems indicating direct organogenesis. Transformed cells were viewed at least in the second cellular layer. Analysis for stable gus expression showed gus expression 19 days after bombardment. In the histological analysis transformed cells in process of division were observed. In conclusion the Nordestina cultivar formed multiple shoots on medium supplemented with TDZ and this protocol of regeneration was compatible with a protocol for biolistic-mediated transformation

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<p> This report presents a study of the sputtering of vacuum deposited thin films of cadmium sulphide on a (111) face of single crystal silicon by Rutherford backscattering (RBS) technique. Cadmium was found to be preferentially sputtered when bombarded to high fluences of 80 kV Bi+ while no significant preferential sputtering was observed in the case of 40 kV Ar+ bombardment. </p> <p> The structural study by reflection high energy electron diffraction (RHEED) revealed that the films grew epitaxially in the wurtzite structure. The epitaxial relations are (00.1) Cds || (111) Si with [10.0] II [110] Si. </p> <p> Scanning electron microscope (SID4) microphotographs showed smooth surface features with a large grain size (surface grain size was ~ 83 nm) for a film of about 60 nm thickness. </p> <p> The basic structure did not change with highest fluences of Bi+ (Sxlo16 ions/cm2 ) and Ar+ (6.7xlo16 ions/cm2). He+ beam channeling was done for unbombarded and bombarded CdS films. It was found that the critical angle of channeling for cadmium increased for bombarded samples while for sulfur the statistics were too poor for any conclusion. </p> <p> Saturation fluences for bismuth and argon retention were observed and are compared with calculated values. </p> / Thesis / Master of Engineering (MEngr)

The effects of ion bombardment on the chemical reactivity of GaAs(100) were investigated by X-ray photoelectron spectroscopy. The enhancement in reactivity was shown to be related to the energy and mass of the bombarding ion. The oxidation results were compared to chemically cleaned (1:1 HCI(conc)/H₂O) and IHT (simultaneous ion/heat treatment) prepared GaAs(100). Before ion bombardment, GaAs(100) was chemically cleaned with 1:1 HCI(conc)/H₂O to remove surface oxides. Chemically cleaned GaAs was bombarded with 0.5-3 KeV Ar⁺ ions (fluences = 10¹⁶-10¹⁷ ions/cm²) and with 3 KeV Xe⁺, Ar⁺, ²⁰Ne⁺, and ³He⁺ ions (fluence =10¹⁷ ions/cm²) to investigate the effect of ion bombardment energy and mass on chemical reactivity. Ion bombardment results in the preferential sputtering of As and the amount of As depletion is dependent upon ion bombardment energy and mass. Following chemical cleaning and ion bombardment, GaAs was exposed to 10⁷-10¹³ L O2, 10⁹-10¹³ L H₂O,10⁶-10⁸ L NO, and 10⁷-10¹¹ L N₂O (1 Langmuir (L) = 1.3x10⁻⁴ Pa•sec). Chemically cleaned GaAs produced equivalent amounts of Ga₂O₃ and As₂O₃ upon O₂ exposure. Oxygen exposure of ion bombarded GaAs resulted in the formation of Ga₂O₃, As₂O₃, and As₂O₅. Nitric oxide exposure produced Ga₂O₃ and As₂O₃, and N₂O exposure produced only Ga₂O₃. Gallium oxide was preferentially formed for ion bombarded material and the relative amount of Ga₂O₃ increased with increasing ion energy. 3 KeV Xe⁺ ion-bombarded GaAs exhibited the greatest reactivity to O₂ and NO. Exposure of ion bombarded GaAs to NO produced the greatest amounts of Ga₂O₃. Ion bombarded GaAs was the least reactive to N₂O. Exposure of ion bombarded GaAs to H₂O resulted in the formation of GaOOH and Ga(OH)₃, with Ga(OH)₃ formation occurring only on 2 KeV Ar⁺ and 3 KeV Ar⁺ and Xe⁺ ion-bombarded material at exposures above 10¹⁰ L. It was shown that defects were responsible for the increased reactivity and that preferential formation of Ga₂O₃ on ion bombarded material was not determined by the Ga/As surface ratio. Exposing IHT prepared GaAs to O₂ produced equivalent amounts of Ga₂O₃ and As₂O₃ when the Ga/As ratio was 1.23±0.07. The damage caused by ion bombardment was investigated by optical reflectivity in the visible and near-ultraviolet region (1.6-5.6 eV), Raman spectroscopy, and capacitance-voltage measurements. Ion bombardment forms a damaged layer that is amorphous. The depth of damage is proportional to the energy of the bombarding ion and inversely proportional to the mass of the bombarding ion. The shallow damage depth for 3 KeV Xe⁺ ion-bombarded GaAs offers some explanation for increased chemical reactivity. The increased reactivity of ion bombarded GaAs with O₂ and NO is attributed to surface defects (broken surface bonds). It is suggested that these broken bonds are in the form of singly occupied dangling bonds. A model for the surface and possible reaction pathways for O₂ and NO reactions are discussed. / Ph. D.

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The problem with which this investigation is concerned is that of making experimental measurements of proton-induced K-shell x-ray production cross sections and to study the dependence of these cross sections upon the energy of the incident proton. The measurements were made by detection of the characteristic x-rays emitted as a consequence of the ionization of the K-shell of the atom. The method for relating this characteristic x-ray emission to the x-ray production cross section is discussed in this work.

Experimentally measured L-shell x-ray production cross sections are presented for 8-36-MeV oxygen-ion bombardment of Ce, Pr, Sm, Eu, Dy, and Ho; for 4-32-MeV carbon-ion bombardment of La and Yb; for 6-32-MeV carbon-ion bombardment of Pr, Nd, Sm, and Dy; and for ll-29-MeV carbon-ion bombardment of Ce, Eu, Gd, and Ho. Theoretical predictions via the plane wave Born approximation (PWBA) with corrections for increased binding of target electrons and Coulomb deflection of the incident projectile tend to underestimate the experimental data; and this underestimation tends to get worse at the low- and high-energy ends of the range of energies used in this work.

Optical, electrical, and microstructural effects of Ar ion bombardment and Ar incorporation on thermally evaporated Ag and Al thin films were investigated. The results show that as the momentum supplied to the growing films by the bombarding Ar ions per arriving metal atom increases, refractive index at 632.8 nm increases and extinction coefficient decreases, lattice spacing expands, grain size decreases, electrical resistivity increases, and trapped Ar increases slightly. In Ag films, stress reverses from tensile to compressive; in AI films compressive stress increases. In both films, the change in optical constants can be explained by variation in void volume. The reversal of stress from tensile to compressive in Ag films requires a threshold level of momentum. The increase in electrical resistivity is related to the increase in the void fraction, decrease in the grain size, and increase in trapped Ar in both types of films. Many of these properties correlate well with the momentum transferred, suggesting that the momentum is an important physical parameter in describing the influence of ion beams on growing thin films and determining the characteristics of thin metal films prepared by ion-assisted deposition (IAD). With a low energy ion beam, the Ar concentration in IAD Ag films was negligible. When the bombarded film thickness was less than 5 nm, the electrical resistivity of IAD Ag films tended to decrease slightly from that of the non-IAD film. Using the Bruggeman effective medium theory, a formula for the void fraction at any given wavelength was derived. We investigated optical properties, stoichiometry, chemical bonding states, and structure of aluminum oxynitride thin films prepared by reactive ion-assisted deposition. Variations of optical constants and chemical bonding states are related to the stoichiometry. We found that our amorphous aluminum oxynitride film is not simply a mixture of aluminum oxide and nitride but a compound. A rugate filter using a step-index profile of aluminum oxynitride films was fabricated by nitrogen ion beam bombardment of a growing Al film with backfilled oxygen pressure as the sole variable. The effects of ultrasound-assisted deposition (UAD) on the optical properties of ZrO₂, Ta₂O₅, and MgF₂ films were investigated. UAD is likely to induce oxygen and fluoride deficiencies in oxide and fluoride films and increase the packing density of films.