The drug metoclopramide was found to adsorb to the unionized and ionized silica surface. The primary objective of this research was to use potentiometric titration in order to study the specificity of the interactions of benzamide analogs with the hydroxyl groups, silanols, on the Aeroperl® silica surface. Mass titration studies showed that the acidity of surface silanols increases with dissolved metoclopramide and similar compounds. The nature of the interaction was concluded to involve a physical adsorption process. A different potentiometric titration method was devised to determine the ionization of silanols in the presence of a dissolved compound with solubility limitations. This method was found to give similar results as that described in the literature. The presence of dissolved metoclopramide was found to cause a large increase in the density of the negatively charged silanols on the silica surface. The ionization of silica was dependent on the concentration of dissolved metoclopramide at low pH but was found to be constant over a wide concentration range at pH 7.0 or higher. Adsorption studies with unionized silica indicated that specific interactions with the surface silanols occur as well as non-specific interactions driven by hydrophobic bonding with the surface siloxane groups. There was an increase in the adsorption of metoclopramide with increasing ionization of the silica surface which suggested that the negatively charged silanols constituted an additional adsorption site. The mechanism of the interaction was elucidated by potentiometric titration with various probe compounds. The titration data with lidocaine suggested that the ionization of the surface silanols is influenced by specific interactions with the adsorbed compound rather than concentration effects. The ionized site density of silica was found to be related to the relative magnitude of the aromatic π-electron density of the adsorbed benzamides. A comparison of these titration data with that of triethylamine indicated that ionic interactions between the positively charged amine groups and the negatively charged silanols are likely to be occurring. Based on the difference in chemical structure, the titration data with dissolved ephedrine indicated that the other site of interaction is likely to be between the carbonyl oxygen of the adsorbed benzamides and the unionized silanols. The pH dependence of the ionization of silanols for both adsorption sites suggested that silanols interact simultaneously with several functional groups on a single adsorbed molecule.

Melvin A. Herlin and Sanborn C. Brown. / "May 3, 1948." / Army Signal Corps Contract No. W-36-039 sc-32037.

This thesis is based on studies of multiple ionization of atoms and molecules induced by the absorption of a single photon. For the experimental investigations a time-of-flight magnetic bottle spectrometer has been used to detect the emitted electrons in coincidence. The method of coincidence time-of-flight spectroscopy and the experimental setup used is described. Experimental and theoretical results on molecular double core holes (DCHs) and multiple ionization of atoms are presented. Molecular DCHs are of considerable interest, as their chemical shifts are predicted to be more sensitive than their single core hole counterparts. Using CH4 and NH3 as examples, it is shown that molecules with two vacancies in the innermost shell can be studied using synchrotron light in combination with our coincidence technique. The chemical shifts of S 2p DCHs are investigated for the molecules CS2, H2S and SO2 and the influence of relaxation effects on the shifts are estimated. In the studies of atoms, the main focus is on the processes leading to double and higher degrees of ionization, and the final state populations. In cadmium double photoionization in the photon energy region 40-200 eV occurs mainly by indirect ionization via valence ionized satellite states and through Coster-Kronig decay of inner shell hole states. In valence-valence ionization of krypton by 88 eV photons both direct and indirect ionization processes are found to be important. For the indirect pathways strong final state selectivity in the autoionization decays of the intermediate states is observed. Triple ionization of krypton via intermediate core-valence doubly ionized states is investigated. The intermediate states are observed in the energy region 120-125 eV, and their decay to states of the triply charged ion is mapped. Experimental and theoretical results on the formation of 2p double hole states in argon are presented. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>

This study on the neutron-induced fission of 234U was carried out at the 7 MV Van de Graaff accelerator of IRMM in Belgium. A Twin Frisch-Grid Ionization Chamber (TFGIC) was used to study 234U(n,f) between En = 0.2 and 5.0 MeV. The reaction is important for fission modelling of the second-chance fission in 235U(n,f). The fission fragment (FF) angular-, energy and mass distributions were determined using the 2E-method highlighting especially the region of the vibrational resonance at En = 0.77 MeV. The experiment used both conventional analogue and modern digital acquisition systems in parallel. Several advantages were found in the digital case, especially a successful pile-up correction. The shielding limitations of the Frisch-grid, called "grid-inefficiency", result in an angular-dependent energy signal. The correction of this effect has been a long-standing debate and a solution was recently proposed using the Ramo-Shockley theorem. Theoretical predictions from the latter were tested and verified in this work using two different grids. Also the neutron-emission corrections as a function of excitation energy were investigated. Neutron corrections are crucial for the determination of FF masses. Recent theoretical considerations attribute the enhancement of neutron emission to the heavier fragments exclusively, contrary to the average increase assumed earlier. Both methods were compared and the impact of the neutron multiplicities was assessed. The effects found are significant and highlight the importance of further experimental and theoretical investigation. In this work, the strong angular anisotropy of 234U(n,f ) was confirmed. In addition, and quite surprisingly, the mass distribution was found to be angular-dependent and correlated to the vibrational resonances. The anisotropy found in the mass distribution was consistent with an anisotropy in the total kinetic energy (TKE), also correlated to the resonances. The experimental data were parametrized assuming fission modes based on the Multi-Modal Random Neck-Rupture model. The resonance showed an increased yield from the Standard-1 fission mode and a consistent increased TKE. The discovered correlation between the vibrational resonances and the angular-dependent mass distributions for the asymmetric fission modes may imply different outer fission-barrier heights for the two standard modes.

We demonstrate experimentally that the multiphoton ionization rate in gallium arsenide depends on the alignment of the laser polarization with respect to the crystal axis. We show real-time modulation of 1900nm laser ionization rate, through viewing transmission, which mimics the symmetry of the semiconductor crystal. We propose that the modulation in the ionization rate arises because the varying reduced effective carrier mass, as predicted by Keldysh theory. We show direct comparison of the experimental transmission modulation depth with that predicted by Keldysh theory. This opens up a novel method for real-time non-invasive crystallography of crystalline materials.

<p>The purpose of this research was to verify experimentally the buildup region dose calculation for Pinnacle³ (version 9.0), a commercial treatment planning system, commissioned and in use at the Saskatoon Cancer Center. To achieve this, buildup dose measurements using Attix parallel-plate ionization chamber and calculations by Pinnacle³, for a variety of clinical setups, were compared. The clinical setups involved 6 MV and 15 MV photon beams, open fields, enhanced dynamic wedges, physical wedges, block tray, 85, 100 and 120 cm source-to-surface distances (SSDs), and field sizes 3 x 3, 4 x 4, 5 x 5, 8 x 8, 10 x 10, 12 x 12, 15 x 15, 20 x 20, 30 x 30 cm². The dose difference (DD) and distance-to-agreement (DTA) were used to evaluate the discrepancy between measured and calculated dose values. Significant discrepancies between measured and calculated buildup dose values were observed because the modeling in Pinnacle³ is based on measurements made using a cylindrical ionization chamber. Based on the criteria of DD less than 2% or DTA less than 2 mm, 93.7% of 1,710 dose points for the 6 MV photon beam passed while for the 15 MV photon beam, 96.1% of the 2,244 dose points passed. The dose points that did not pass these criteria were mostly for open fields, block tray fields, fields with physical wedges of 15 degrees and 30 degrees and for fields with shorter source-to-surface distances. This is attributed to the high electron contamination associated with these fields. The low levels of discrepancies between measured and calculated dose values for the 15 MV beam as compared to those of the 6 MV beam need further investigations. The good agreement between measured and calculated dose values after remodeling the Electron Contamination in Pinnacle³ based on Attix chamber measurements is an indication that the Electron Contamination equation in Pinnacle³ may be adequate for modeling of electron contamination in the buildup dose region. The disagreement between Attix chamber and EBT 2 film measured buildup dose values was less than 3% for 89.9% of the buildup dose measurements compared. It is recommended to use a good parallel plate ionization chamber, such as the Attix chamber, for measurements in the buildup region.</p>

This thesis explored "lacunarity" as a technique for measuring ionization and energy loss of charged particles in nuclear emulsion. Lacunarity is defined as the fraction of a track segment that consists of gaps. A comparison was made between lacunarity and other methods of measuring ionization, particularly the method of measuring blob density. The nuclear emulsion used was exposed to a one GeV/C K- -meson beam.produced by the accelerator at the university of California at Berkeley. Proton, K – meason, π – meson and muon tracks emanating from “stars” or sites of nuclear disintegration were used as bases of study. The procedure was to plot grain density as determined by lacunarity of a track segment as well as blob density versus residual range for the various particles. This student found that except for tracks of very heavily ionizing particles or of very lightly ionizing particles, lacunarity is a better measure of ionization and energy loss than is blob density.Ball State UniversityMuncie, IN 47306

<p>The purpose of this research was to verify experimentally the buildup region dose calculation for Pinnacle³ (version 9.0), a commercial treatment planning system, commissioned and in use at the Saskatoon Cancer Center. To achieve this, buildup dose measurements using Attix parallel-plate ionization chamber and calculations by Pinnacle³, for a variety of clinical setups, were compared. The clinical setups involved 6 MV and 15 MV photon beams, open fields, enhanced dynamic wedges, physical wedges, block tray, 85, 100 and 120 cm source-to-surface distances (SSDs), and field sizes 3 x 3, 4 x 4, 5 x 5, 8 x 8, 10 x 10, 12 x 12, 15 x 15, 20 x 20, 30 x 30 cm². The dose difference (DD) and distance-to-agreement (DTA) were used to evaluate the discrepancy between measured and calculated dose values. Significant discrepancies between measured and calculated buildup dose values were observed because the modeling in Pinnacle³ is based on measurements made using a cylindrical ionization chamber. Based on the criteria of DD less than 2% or DTA less than 2 mm, 93.7% of 1,710 dose points for the 6 MV photon beam passed while for the 15 MV photon beam, 96.1% of the 2,244 dose points passed. The dose points that did not pass these criteria were mostly for open fields, block tray fields, fields with physical wedges of 15 degrees and 30 degrees and for fields with shorter source-to-surface distances. This is attributed to the high electron contamination associated with these fields. The low levels of discrepancies between measured and calculated dose values for the 15 MV beam as compared to those of the 6 MV beam need further investigations. The good agreement between measured and calculated dose values after remodeling the Electron Contamination in Pinnacle³ based on Attix chamber measurements is an indication that the Electron Contamination equation in Pinnacle³ may be adequate for modeling of electron contamination in the buildup dose region. The disagreement between Attix chamber and EBT 2 film measured buildup dose values was less than 3% for 89.9% of the buildup dose measurements compared. It is recommended to use a good parallel plate ionization chamber, such as the Attix chamber, for measurements in the buildup region.</p>

No description available.

This thesis presents a comprehensive assessment of breakdown and operational voltage constraints in state-of-the-art silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) BiCMOS technology. Technology scaling of SiGe HBTs for high frequency performance results on lower breakdown voltages, making operating voltage constraints an increasingly vital reliability consideration in SiGe HBTs from both a device and circuits perspective.