Recent studies have been done to create models that predict the response of the human visual system (HVS) based on how the HVS processes an image. The most widely known of these models is the Gabor model, since the Gabor patterns closely resemble the receptive filters in the human eye. The work of this thesis examines the use of Symlets to represent the HVS, since Symlets provide the benefit of orthogonality. One major problem with Symlets is that the energy is not stable in respective Symlet channels when the image patterns are translated spatially. This thesis addresses this problem by up sampling Symlets instead of down sampling, and thus creating shift invariant Symlets. This thesis then compares the representation of Gabor versus Symlet approach in predicting the response of the HVS to detecting print defect patterns such as banding and graining. In summary we noticed that Symlet prediction outperforms the Gabor prediction thus Symlets would be a good choice for HVS response prediction. We also concluded that for banding defect periodicity and size are important factors that affect the response of the HVS to the patterns. For graining defects we noticed that size does not greatly affect the response of the HVS to the defect patterns. We introduced our results using two set of performance metrics, the mean and median.

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This thesis presents an investigation of the phenomenon of efficient, room temperature luminescence from dislocation-engineered (DE) silicon. Previous work had demonstrated that the introduction of near-surface dislocation loops to a silicon substrate by boron ion implantation and high temperature annealing produced efficient electroluminescence at room temperature. However, the mechanism by which high efficiency luminescence is produced was not understood. A wide matrix of specimens containing dislocations was fabricated by a variety of methods, including ion implantation, and their luminescence efficiencies were correlated to their physical properties. Transmission electron microscopy was used to characterise the defect structures created by ion implantation. In the majority of specimens a band of dislocation loops in close proximity to the surface was observed. The dislocation loops were shown to be consistent with a mixture of Frank and perfect dislocation loops, the relative proportions of which were dependent upon processing conditions. The thermal evolution of the dislocation loop size distribution was investigated. For the first time, a size distribution displaying a double peak was observed. The size distribution was shown to be consistent with the Gaussian distribution of two defect populations of different mean diameter. The thermal evolution of the size distribution was investigated in silicon implanted samples. A flux of self-interstitials from Frank dislocation loops to perfect dislocation loops was deduced. The evolution of the dislocation loop sizes was found to be consistent with Ostwald ripening. Cathodoluminescence (CL) was used to investigate the luminescent properties of silicon at room temperature for the first time. A new CL system was installed for this work, initially the CL system was characterised and a routine to ensure a high degree of reproducibility was formed. The luminescence mechanism of DE-silicon was shown to be the same as in unprocessed silicon wafers; TO phonon-assisted recombination. The mechanism of enhanced luminescence from DE-silicon was unambiguously shown to be due to the gettering of electrically active impurities from the specimen bulk. A reduction in the bulk transition metal impurity concentration of up to 35 times was inferred. In samples which were implanted with boron the degree of gettering was found to show a logarithmic dependence on the dislocation density. Using a crosssectional mapping technique, implanted samples were shown to contain a lower concentration of transition metal impurities throughout the entire wafer in comparison to as-received, unprocessed specimens. Furthermore, the impurity concentration was found to be lowest in close proximity to the band of dislocation loops. The dislocation loops were found to act as non-radiative recombination centres and their strength was strongly influenced by the local carrier concentration. The high doping levels of samples implanted with boron were found to minimise the non-radiative recombination action of the dislocations. Low temperature annealing was used to improve the luminescence efficiency of DE-silicon further.

Individual, well structurally characterised dislocations present in n-type silicon have been studied using the electron beam induced current (EBIC) mode of an SEM.</p>An EBIC system has been designed and constructed which includes i) phase sensitive detection, ii) computerised control of the experimental equipment and data capture and iii) a variable temperature SEM specimen stage. With this system measurements have been made of the EBIC contrast of individual segments of deformation induced dislocations produced by two stage compressive deformation at 850°C and 420°C. An experimental and theoretical analysis of EBIC signal generation in the Schottky barrier specimens used in this work is presented. This shows that the EBIC contrast measurements made may be directly correlated to the dislocation recombination strength. Contrast measurements have been made at temperatures in the range 120K to 370K and for electron beam currents from 6 x 10^-12A to 2 x 10^-9A. Several new effects have been observed. Minority carrier diffusion length measurements have also been performed in silicon containing dislocations. These show that the value obtained may depend upon experimental parameters used in a hitherto undetected manner. A new theory describing recombination of carriers at charged dislocations has been developed and this has been extended to provide a description of the variation of the EBIC contrast of dislocations with temperature, electron beam current and also the transient response of the EBIC contrast. Comparison of the theoretical predictions with the results gained experimentally shows full agreement for low temperatures or large beam currents. At high temperatures and small beam currents the theory shows the EBIC contrast will behave differently depending on the density of dislocation states present. Interpretation of the experimental results in terms of this theory allows some new insight to be gained for recombination at dislocations, and values for some of the parameters controlling recombination have been obtained.

The Kim and Chan experiment in 2004 gave the first experimental evidence of a possible supersolid state. Even though the origin of this state is not clear yet, several experimental and theoretical investigations suggest defects are responsible for this curious phase. We have used heat pulses and thermal quenching to study pressure gradients and annealing mechanisms in solid 4He crystals. Large pressure gradients exist in crystals grown at constant volume. These can be enhanced by phase transitions, thermal quenching or by partial melting. Annealing reduces defect densities and hence pressure gradients in crystals. Our measurements show that the pressure at different points in a crystal can behave differently, even if there is little change in the crystals average pressure. We measured the activation energy that is associated with the annealing process.

Congenital heart disease is the most common form of birth defect, affecting approximately 1% of liveborn babies. Secundum atrial septal defect (ASD) is the second most common form of congenital heart disease (CHD). Most cases have no known cause. Chromosomal, syndromal and teratogenic causes account for a minority of cases. The hypothesis that mutations in the ASD genes NKX2-5 and GATA4 may cause apparently sporadic ASD was tested by sequencing them in unrelated probands with ASD. In this study, 1/102 individuals with ASD had an NKX2-5 mutation, and 1/129 had a deletion of the GATA4 gene. The cardiac transcription factor TBX20 interacts with other ASD genes but had not previously been associated with human disease. Of 352 individuals with CHD, including 175 with ASD, 2 individuals, each with a family history of CHD, had pathogenic mutations in TBX20. Phenotypes included ASD, VSD, valvular abnormalities and dilated cardiomyopathy. These studies of NKX2-5, GATA4 and TBX20 indicate that dominant ASD genes account for a small minority of cases of ASD, and emphasize the considerable genetic heterogeneity in dominant ASD (also caused by mutations in MYH6 and ACTC). A new syndrome of dominant ASD and the Marcus Gunn jaw winking phenomenon is reported. Linkage to known loci was excluded, extending this heterogeneity, but a whole genome scan did not identify a candidate locus for this disorder. Previous studies of inbred laboratory mice showed an association between patent foramen ovale (PFO) and measures of atrial septal morphology, particularly septum primum length (???flap valve length??? or FVL). In humans, PFO is associated with cryptogenic stroke and migraine, and is regarded as being in a pathological contiuum with ASD. Twelve inbred strains, including 129T2/SvEms and QSi5, were studied, with generation of [129T2/SvEms x QSi5] F1, F2 and F14 mice. Studies of atrial morphology in 3017 mice confirmed the relationship between FVL and PFO but revealed considerable complexity. An F2 mapping study identified 7 significant and 6 suggestive quantitative trait loci (QTL), affecting FVL and two other traits, foramen ovale width (FOW) and crescent width (CRW). Binary analysis of PFO supported four of these.

We have studied the introduction of defects in silicon wafers with low dose channelling ion implantation. (For complete abstract open document)

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Description based on contents viewed Feb. 11, 2009; title from PDF t.p. Includes bibliographical references (p. 49-50).

Thesis (M.S.)--University of Louisville, 1997. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.