This dissertation is divided into two sections. In the first section dielectric and magnetic properties were analyzed for a series of materials: bisphenol A solutions, a poly(amideimide), and polymers filled with either carbon black, iron particles, or aluminum flake. The second section deals with the influence of volatiles and low temperature aging on the dynamic mechanical and dielectric properties of a poly(amide-imide). In the first investigation, solutions of bisphenol A in tetrahydrofuran (THF) or diglycidylether of bisphenol A (DGEBA) in either toluene or tetrahydrofuran were used to identify the influence of chemistry, solvent, and concentration (0 - 2.6M) on dielectric loss (ɛ") and storage (ɛ') at (2.45 GHz). A number of solutions were examined as a function of frequency and temperature to obtain a mechanistic explanation for the single frequency data. The results showed the relaxation time shifting to higher frequencies with increased temperature and shifting to lower frequencies after a critical concentration. A polymer derived from bisphenol A and the diglycidylether of bisphenol A was sandwiched between two microwave inactive quartz plates to show selective heating of a 0.002" film. The poly(amide-imide's) dielectric storage and loss values (ɛ', ɛ") were examined as a function of temperature. The metal filled systems showed nonlinear behavior for dielectric loss (ɛ"), magnetic loss (µ"), and normalized magnetization (Gauss), which were explained by a percolation model. A critical volume fraction (Φ_C) was identified in the 0.15 - 0.25 volume fraction range. Scaling of dielectric and magnetic properties above Φ_C was 1.2 for aluminum flake, 1.5 for iron, and 5 for carbon black. The development of structure that occurred with increased filler content was monitored by scanning electron microscopy (SEM) and showed qualitative agreement with percolation behavior. At low volume fractions, there were individual particles, then clusters, then veins of material that extended many particle lengths. The second part of this dissertation dealt with the influence of volatiles on the dynamic mechanical and dielectric values of a poly({amide-imide). Experiments were conducted in both the temperature and time domains. These data were complemented by thermogravimetry (TG), thermogravimetry-mass spectrometry (TG-MS), and thermomechanical analysis (TMA). The isothermal desorption of volatiles (150 - 165°C) could be monitored by either mechanical, dielectric, or gravimetric techniques. The mechanical experiments revealed two peaks for water: one a low temperature peak (-90 - -50°C) and the other at (100 - 190°C). The dielectric analysis revealed two peaks for as received poly(amide-imide). The first was between -50 to 0°C, the other was between 0 to 50°C. The low power dielectric analysis and volatile desorption behavior were combined to explain the structure that developed after poly(amideimide) spheres were subjected to similar thermal or microwave processing conditions. Thermal processing produced a closed cell structure and a rough surface, while microwave processing produced an open cell structure at a smooth air-surface interface. / Ph. D.

Various processes that participate in ion beam surface modification are studied using phenomenological, analytical and first principle models. The processes that are modelled phenomenologically include preferential sputtering, radiation-damage induced migration and second phase precipitation. The models are based on numerical solutions of the transport equation and include the processes of ion collection, sputtering, lattice dilation or accommodation and diffusion as well. The model for preferential sputtering takes into account the depletion of the preferentially sputtered element at the surface and the atomic transport process that results from the concentration gradients caused by the depletion. Results are presented for the case of Ta implantation into Fe. ln the radiation-damage induced migration the flux of the solute atoms is coupled to the concentration gradient of the continuously introduced defects. Examples of implantation of Sn into Fe and N into Fe are modeled to demonstrate the influence of radiation-damage induced migration. The precipitation of second phases during irradiation is modelled using thermodynamic considerations but with solubility values under irradiation obtained from experiment. In the model the solute atoms in excess of the solubility limit are assumed to precipitate out. Calculations are presented for the case of N implantation into Nb. Using first principle calculation for binary collisions in solids a computer simulation code was developed to study the collisional mixing occurring during high fluence ion implantation. It is based on the Monte Carlo code TRIM, and is capable of updating the target composition as the implantation process proceeds to high fluences. The physical basis for the dynamic simulation as well as a detailed analysis on the statistics required for obtaining the profiles with a given accuracy are presented. Vectorized results in a high computational efficiency. The predicted collisional broadening of the implantation profiles is presented for Ar bombardment into a Sn-Fe target as well as Ti implantation into C-Fe. The results are compared to those of the diffusion approximation. A semi-empiricaI model based on an analytical evaluation of ion mixing at low temperatures was developed taking into account collisional mixing and thermal spike effects, as well as the thermal spike shape. The ion beam mixing parameter for the thermal spike is derived as being proportional to different powers of the damage parameter, i.e. the damage energy scaled by the cohesive energy of the matrix, dependent on the thermal spike shape and point defect density in the thermal spike regions. Three different regions of ion beam induced mixing were recognized according to different density levels of the damage parameter. An experiment was conducted to determine the effect of chemical or thermodynamic factors in the migration of C in the presence of Fe and Ti atoms. A marker layer of C in a Fe-Ti matrix was ion beam mixed using Ar. The large mixing effect is tentatively attributed to a favorable heat of mixing values. / Ph. D.

This dissertation begins with a review of radiation chemistry and a number of important variables which can influence the chemistry occurring in irradiated polymeric materials. Following the literature review, four different studies involving the electron beam irradiation and subsequent characterization of various polymeric materials are presented. The first study describes a novel process that has been developed for producing crosslinked polymeric microspheres. With this process, it is possible to produce polymeric microspheres in an aqueous media with a solids content as high as 67 vol % by incorporating a trifunctional acrylate into a biliquid foam (known as polyaphrons) and exposing it to electron beam radiation. The second study involves characterizing the radiation response of a relatively new crystallizable polyimide, LARC-CPI, primarily in terms of its thermal properties as determined by differential scanning calorimetry (DSC), with some limited x-ray scattering experiments. The third study illustrates the effects of electron beam radiation on four different glassy polymers that have been physically aged prior to irradiation. It is shown that irradiation reduces the extent of aging present in the material and that this reduction is proportional to the absorbed dose. The last study examines the crosslinking behavior of a polystyrene - poly(vinyl methyl ether) blend as a function of absorbed dose, composition, and phase separation. It is shown that the crosslinking behavior (in terms of the gel fraction produced) is strongly dependent on all three of these factors. Furthermore, the protective nature of the aromatic groups in polystyrene that is typically displayed by this polymer was not observed in this blend system. / Ph. D.

Bibliography: leaves 267-287 / xviii, 287, [ca. 40] leaves, [10] leaves of plates : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1985

Microstructure changes in uranium and uranium/metal alloys due to radiation damage are of great interest in nuclear science and engineering. Titanium has attracted attention because of its similarity to Zr. It has been proposed for use in the second generation of fusion reactors due to its resistance to radiation-induced swelling. Aluminum can be regarded as a standard absorbing material or backing material for irradiation targets. Initial study of thin aluminum films irradiation by �������Cf fission fragments and alpha particles from source has been conducted in the Radiation Center, Oregon State University. Initial study of thin aluminum films irradiation by �������Cf fission fragments and alpha particles from source has been conducted in the Radiation Center, Oregon State University. Aluminum can be regarded as a standard absorbing material or backing material for irradiation targets. The AFM investigation of microstructure damages of thin aluminum surfaces revealed that the voids, dislocation loops and dislocation lines, formed in the thin aluminum films after bombardment by �������Cf fission fragments and alpha particles, depends on the irradiation dose. The void swelling and diameter and depth of voids increase linearly with the fluence of particles and dose; however, the areal density of voids decreased when formation of dislocation loops began. Study of deposition of uranium on titanium backing material by molecular plating and characterization of produced U/Ti film has been performed. The U/Ti film has smooth and uniform surfaces but the composition of the deposits is complex and does not include water molecules which probably involve the presence of U (VI). A possible structure for the deposits has been suggested. X-ray diffraction pattern of U/Ti films showed that The U/Ti film has an amorphous structure. Uranium films (0.500 mg/cm��) and stack of titanium foils (thickness 0.904 mg/cm��) were used to study the microstructural damage of the uranium film and its backing material. Irradiation of U/Ti film and Ti foils with 1 MeV/u (136 MeV) �������Xe�������� ions in was performed in the Positive Ion Injector (PII) unit at the Argonne Tandem Linear Accelerator System (ATLAS) Facility at Argonne National Laboratory, IL. Pre- and post- irradiation of samples was analyzed by X-ray diffraction, Scanning Electron Microscopy/Energy Dispersive Spectroscopy (SEM/EDS) and Atomic Force Microscopy (AFM). The irradiation of U/Ti films results in the formation of a crystalline U���O��� phase and polycrystalline Ti phase. Annealing of the thin uranium deposit on a titanium backing at 800��C in the air atmosphere condition for an hour produced a mixture of UO���, U���O���, Ti, TiO and TiO��� (rutile) phases; meanwhile, annealing at 800oC for an hour in the argon environment produced a mixture of ��-U���O���, Ti and TiO��� (rutile) phases. These phenomena indicate that the damage during irradiation was not due to foil heating. Microstructural damage of irradiated uranium film was dominated by void and bubble formation. The microstructure of irradiated titanium foils is characterized by hillocks, voids, polygonal ridge networks, dislocation lines and dislocation networks. Theory predicts that titanium undergoes an allotropic phase transformation at 882.5 ��C, changing from a closed-packed hexagonal crystal structure (��-phase) into a body-centered cubic crystal structure (��- phase). When the titanium foils were irradiated with 136MeV �������Xe�������� at beam intensity of 3 pnA corresponding to 966��C, it was expected that its structure can change from hexagonal-close packed (hcp) to body-centered cubic (bcc). However, in contrast to the theory, transformation from ��-Ti (hcp) phase to fcc-Ti phase was observed. This phenomenon indicates that during irradiation with high energy and elevated temperature, the fcc-Ti phase more stable than the hcp-Ti Phase. / Graduation date: 2012

PiRNAs and their Piwi family protein partners are part of a germline specific epigenetic regulatory mechanism essential for proper spermatogenesis, silencing of transposable elements, and maintaining germline genome integrity, yet their role in the response of the male germline to genotoxic stress is unknown. Ionizing radiation (IR) is known to cause transgenerational genome instability that is linked to carcinogenesis. Although the molecular etiology of IR-induced transgenerational genomic instability is not fully understood, it is believed to be an epigenetically mediated phenomenon. IR-induced alterations in the expression pattern of key regulatory proteins involved in the piRNA pathway essential for paternal germline genome stability may be directly involved in producing epigenetic alterations that can impact future generations. Here we show whole body and localized X-irradiation leads to significant altered expression of proteins that are necessary for, and intimately involved in, the proper functioning of the germline specific piRNA pathway in mice and rats. In addition we found that IR-induced alterations to piRNA pathway protein levels were time and dose dependent. / ix, 123 leaves : ill. (some col.) ; 29 cm

This thesis relates a technique for increasing the optical strength of NaCl and KCl single-crystal samples. The 1.06-μm pulsed laser damage thresholds were increased by factors as large as 4.6 for a bulk NaCl single-crystal sample. The bulk laser damage breakdown threshold (LDBT) of the crystal was measured prior to and after heat treatment at 800*C using a Nd:YAG laser operating at 1.06 μm. Bulk and surface LDBTs were also studied on samples annealed at 400° C. These samples showed differences in damage morphology on both cleaved and polished surfaces, and the cleaved surfaces had improved damage thresholds. However, neither the polished surfaces nor the bulk showed improved threshold at the lower annealing temperature.

Approximately 45% of men will develop cancer during their lifetime; some of which will be of reproductive age (Canadian Cancer Society, 2008). Current advances in treatment regimens such as radiotherapy have significantly lowered cancer-related mortality rates; however, one major quality-of-life issue in cancer survivors is the ability to produce healthy offspring. Exposure to ionizing radiation (IR) leads to genomic instability in the germline, and further to transgeneration genome instability in unexposed offspring of preconceptionally exposed parents. The results presented in this thesis define, in part, the molecular consequences of direct and indirect irradiation for the male germline. Direct exposure results in a significant accumulation of DNA damage, altered levels of global DNA methylation and microRNAome dysregulation of testis tissue. Localized cranial irradiation results in a significant accumulation of unrepaired DNA lesions and loss of global DNA methylation in the rodent (rat) germline. Biological consequences of the changes observed are discussed. / xii, 121 leaves : ill. ; 29 cm.

Silicon-germanium (SiGe) BiCMOS technology platforms have proven invaluable for implementing a wide variety of digital, RF, and mixed-signal applications in extreme environments such as space, where maintaining high levels of performance in the presence of low temperatures and background radiation is paramount. This work will focus on the investigation of the total-dose radiation tolerance of a third generation complementary SiGe:C BiCMOS technology platform. Tolerance will be quantified under proton and X-ray radiation sources for both the npn and pnp HBT, as well as for an operational amplifier built with these devices. Furthermore, a technique known as junction isolation radiation hardening will be proposed and tested with the goal of improving the SEE sensitivity of the npn in this platform by reducing the charge collected by the subcollector in the event of a direct ion strike. To the author's knowledge, this work presents the first design and measurement results for this form of RHBD.

Extreme environment applications impose stringent demands on technology platforms that are incorporated in electronic systems. Space is a classic extreme environment, encompassing both large temperature fluctuations as well as intense radiation fields. Silicon-germanium technology has emerged as a competitive platform for space-based applications, owing to its excellent low-temperature performance and total ionizing dose tolerance. This technology has however been repeatedly shown to be vulnerable to single event phenomena induced by galactic cosmic rays as well as trapped particles within the earth's geomagnetic field. To improve the radiation tolerance of systems incorporating SiGe components, modifications to fabrications steps (Radiation Hardening by Process, RHBP) and/or device/circuit topologies (Radiation Hardening by Design, RHBD) may be employed. For this thesis, two methodologies are analyzed, both RHBD techniques which come at no additional power/area penalty for implementation.