Ultrasonic characterisation of rolled aluminium and steel sheet correlated with electron backscatter diffraction measurements

This thesis is based on the characterization of material properties of interest in rolled aluminium and steel sheet, both popular materials used across a wide-range of applications. The forming processes involved in producing rolled sheet metal depend on plastic deformation, inducing elastic anisotropy as a consequence. These changes result in a variation from the simple isotropic and cubic symmetry systems possessed by steel and aluminium prior to cold-working. The most significant changes include the introduction of crystallographic texture and the morphology of the crystallographic grains in size and shape to accommodate the plastic deformation. It is desirable in industries that use rolled product for manufacturing components to quantify such changes. The literature has postulated links between plastic and elastic properties, and hence any quantification of the elasticity, crystallographic texture and grain morphology can aid in the prediction of future formability behaviour. This thesis presents non-destructive, rapid ultrasonic measurements to characterize some of the changes that are evident in rolled aluminium and steel sheet. These ultrasonic results have then been correlated to crystallographic orientation measurements generated from using a microscopic technique called electron backscatter diffraction (EBSD). The level of agreement between the two contrasting methods has been analysed and is presented here. The non-destructive ultrasonic measurements include quantifying crystallographic texture utilising theory linking the S0 Lamb wave velocity and the direction of propagation in a rolled sheet with respect to the rolling direction. This leads to the determination of texture coefficients known as orientation distribution coefficients (ODC). Through-thickness linearly polarized SH waves have then been used to analyse grain morphology using attenuation data, and elasticity measurements from velocity data. EBSD datasets have been manipulated to produce predictions of the effective elastic stiffness constants, which in turn can be used to generate comparable S0 Lamb wave velocity predictions to be directly compared to the ultrasonic measurements. This process has required a novel method to generate such ultrasonic velocity predictions as a function of angle, together with predictions for the nine effective elastic stiffness constants inherent to rolled orthorhombic sheet. The facility to measure grain size and shape accurately from EBSD data has been utilized. The thesis starts with a general introduction in non-destructive testing and microscopy, with focussed discussion on ultrasound, electromagnetic acoustic transducers (EMATs), EBSD and metallurgy in the subsequent chapters. Chapter 6 introduces the development of correlation methods between the ultrasound and EBSD results, with chapters 7 and 8 displaying the empirical ultrasound and EBSD data respectively. Chapter 9 compares the data from the two methods, with the final conclusions given in chapter 10

How Hot Is Radiation?

A self-consistent approach to nonequilibrium radiation temperature is introduced using the distribution of the energy over states. We begin rigorously with ensembles of Hilbert spaces and end with practical examples based mainly on the far from equilibrium radiation of lasers. We show that very high, but not infinite, laser radiation temperatures depend on intensity and frequency. Heuristic "temperatures" derived from a misapplication of equilibrium arguments are shown to be incorrect. More general conditions for the validity of nonequilibrium temperatures are also established.Comment: 26 pages, revised, LaTeX, 3 encapsulated PostScript figure

Ultrasonic characterisation of rolled aluminium and steel sheet correlated with electron backscatter diffraction measurements

This thesis is based on the characterization of material properties of interest in rolled aluminium and steel sheet, both popular materials used across a wide-range of applications. The forming processes involved in producing rolled sheet metal depend on plastic deformation, inducing elastic anisotropy as a consequence. These changes result in a variation from the simple isotropic and cubic symmetry systems possessed by steel and aluminium prior to cold-working. The most significant changes include the introduction of crystallographic texture and the morphology of the crystallographic grains in size and shape to accommodate the plastic deformation. It is desirable in industries that use rolled product for manufacturing components to quantify such changes. The literature has postulated links between plastic and elastic properties, and hence any quantification of the elasticity, crystallographic texture and grain morphology can aid in the prediction of future formability behaviour. This thesis presents non-destructive, rapid ultrasonic measurements to characterize some of the changes that are evident in rolled aluminium and steel sheet. These ultrasonic results have then been correlated to crystallographic orientation measurements generated from using a microscopic technique called electron backscatter diffraction (EBSD). The level of agreement between the two contrasting methods has been analysed and is presented here. The non-destructive ultrasonic measurements include quantifying crystallographic texture utilising theory linking the S0 Lamb wave velocity and the direction of propagation in a rolled sheet with respect to the rolling direction. This leads to the determination of texture coefficients known as orientation distribution coefficients (ODC). Through-thickness linearly polarized SH waves have then been used to analyse grain morphology using attenuation data, and elasticity measurements from velocity data. EBSD datasets have been manipulated to produce predictions of the effective elastic stiffness constants, which in turn can be used to generate comparable S0 Lamb wave velocity predictions to be directly compared to the ultrasonic measurements. This process has required a novel method to generate such ultrasonic velocity predictions as a function of angle, together with predictions for the nine effective elastic stiffness constants inherent to rolled orthorhombic sheet. The facility to measure grain size and shape accurately from EBSD data has been utilized. The thesis starts with a general introduction in non-destructive testing and microscopy, with focussed discussion on ultrasound, electromagnetic acoustic transducers (EMATs), EBSD and metallurgy in the subsequent chapters. Chapter 6 introduces the development of correlation methods between the ultrasound and EBSD results, with chapters 7 and 8 displaying the empirical ultrasound and EBSD data respectively. Chapter 9 compares the data from the two methods, with the final conclusions given in chapter 10.EThOS - Electronic Theses Online ServiceUK Research Centre for Non-Destructive Evaluation (RCNDE)GBUnited Kingdo

HIV-1 Subtype C Phylodynamics in the Global Epidemic

The diversity of HIV-1 and its propensity to generate escape mutants present fundamental challenges to control efforts, including HIV vaccine design. Intra-host diversification of HIV is determined by immune responses elicited by an HIV-infected individual over the course of the infection. Complex and dynamic patterns of transmission of HIV lead to an even more complex population viral diversity over time, thus presenting enormous challenges to vaccine development. To address inter-patient viral evolution over time, a set of 653 unique HIV-1 subtype C gag sequences were retrieved from the LANL HIV Database, grouped by sampling year as <2000, 2000, 2001-2002, 2003, and 2004-2006, and analyzed for the site-specific frequency of translated amino acid residues. Phylogenetic analysis revealed that a total of 289 out of 653 (44.3%) analyzed sequences were found within 16 clusters defined by aLRT of more than 0.90. Median (IQR) inter-sample diversity of analyzed gag sequences was 8.7% (7.7%; 9.8%). Despite the heterogeneous origins of analyzed sequences, the gamut and frequency of amino acid residues in wild-type Gag were remarkably stable over the last decade of the HIV-1 subtype C epidemic. The vast majority of amino acid residues demonstrated minor frequency fluctuation over time, consistent with the conservative nature of the HIV-1 Gag protein. Only 4.0% (20 out of 500; HXB2 numbering) amino acid residues across Gag displayed both statistically significant (p<0.05 by both a trend test and heterogeneity test) changes in amino acid frequency over time as well as a range of at least 10% in the frequency of the major amino acid. A total of 59.2% of amino acid residues with changing frequency of 10%+ were found within previously identified CTL epitopes. The time of the most recent common ancestor of the HIV-1 subtype C was dated to around 1950 (95% HPD from 1928 to 1962). This study provides evidence for the overall stability of HIV-1 subtype C Gag among viruses circulating in the epidemic over the last decade. However selected sites across HIV-1C Gag with changing amino acid frequency are likely to be under selection pressure at the population level

Risk Factors for Symptomatic Hyperlactatemia and Lactic Acidosis Among Combination Antiretroviral Therapy-Treated Adults in Botswana: Results from a Clinical Trial

Nucleoside analogue reverse transcriptase inhibitors are an integral component of combination antiretroviral treatment regimens. However, their ability to inhibit polymerase-γ has been associated with several mitochondrial toxicities, including potentially life-threatening lactic acidosis. A total of 650 antiretroviral-naive adults (69% female) initiated combination antiretroviral therapy (cART) and were intensively screened for toxicities including lactic acidosis as part of a 3-year clinical trial in Botswana. Patients were categorized as no lactic acidosis symptoms, minor symptoms but lactate <4.4 mmol/liter, and symptoms with lactate ≥ 4.4 mmol/liter [moderate to severe symptomatic hyperlactatemia (SH) or lactic acidosis (LA)]. Of 650 participants 111 (17.1%) developed symptoms and/or laboratory results suggestive of lactic acidosis and had a serum lactate drawn; 97 (87.4%) of these were female. There were 20 events, 13 having SH and 7 with LA; all 20 (100%) were female (p<0.001). Cox proportional hazard analysis limited to the 451 females revealed that having a higher baseline BMI was predictive for the development of SH/LA [aHR=1.17 per one-unit increase (1.08-1.25), p<0.0001]. Ordered logistic regression performed among all 650 patients revealed that having a lower baseline hemoglobin [aOR=1.28 per one-unit decrease (1.1-1.49), p=0.002] and being randomized to d4T/3TC-based cART [aOR=1.76 relative to ZDV/3TC (1.03-3.01), p=0.04] were predictive of the symptoms and/or the development of SH/LA. cART-treated women in sub-Saharan Africa, especially those having higher body mass indices, should receive additional monitoring for SH/LA. Women presently receiving d4T/3TC-based cART in such settings also warrant more intensive monitoring

Genome-wide association study reveals genetic variants associated with HIV-1C infection in a Botswana study population

Although there have been many studies of gene variant association with different stages of HIV/AIDS progression in United States and European cohorts, few gene-association studies have assessed genic determinants in sub-Saharan African populations, which have the highest density of HIV infections worldwide. We carried out genome-wide association studies on 766 study participants at risk for HIV-1 subtype C (HIV-1C) infection in Botswana. Three gene associations (AP3B1, PTPRA, and NEO1) were shown to have significant association with HIV-1C acquisition. Each gene association was replicated within Botswana or in the United States–African American or United States–European American AIDS cohorts or in both. Each associated gene has a prior reported influence on HIV/AIDS pathogenesis. Thirteen previously discovered AIDS restriction genes were further replicated in the Botswana cohorts, extending our confidence in these prior AIDS restriction gene reports. This work presents an early step toward the identification of genetic variants associated with and affecting HIV acquisition or AIDS progression in the understudied HIV-1C afflicted Botswana population

Whole genome sequencing reveals population diversity and variation in HIV-1 specific host genes

HIV infection continues to be a major global public health issue. The population heterogeneity in susceptibility or resistance to HIV-1 and progression upon infection is attributable to, among other factors, host genetic variation. Therefore, identifying population-specific variation and genetic modifiers of HIV infectivity can catapult the invention of effective strategies against HIV-1 in African populations. Here, we investigated whole genome sequences of 390 unrelated HIV-positive and -negative individuals from Botswana. We report 27.7 million single nucleotide variations (SNVs) in the complete genomes of Botswana nationals, of which 2.8 million were missing in public databases. Our population structure analysis revealed a largely homogenous structure in the Botswana population. Admixture analysis showed elevated components shared between the Botswana population and the Niger-Congo (65.9%), Khoe-San (32.9%), and Europeans (1.1%) ancestries in the population of Botswana. Statistical significance of the mutational burden of deleterious and loss-of-function variants per gene against a null model was estimated. The most deleterious variants were enriched in five genes: ACTRT2 (the Actin Related Protein T2), HOXD12 (homeobox D12), ABCB5 (ATP binding cassette subfamily B member 5), ATP8B4 (ATPase phospholipid transporting 8B4) and ABCC12 (ATP Binding Cassette Subfamily C Member 12). These genes are enriched in the glycolysis and gluconeogenesis (p &lt; 2.84e-6) pathways and therefore, may contribute to the emerging field of immunometabolism in which therapy against HIV-1 infection is being evaluated. Published transcriptomic evidence supports the role of the glycolysis/gluconeogenesis pathways in the regulation of susceptibility to HIV, and that cumulative effects of genetic modifiers in glycolysis/gluconeogenesis pathways may potentially have effects on the expression and clinical variability of HIV-1. Identified genes and pathways provide novel avenues for other interventions, with the potential for informing the design of new therapeutics

Understanding travel behaviour change during mega-events: Lessons from the London 2012 Games

This paper presents results from a longitudinal study of the travel behaviour change associated with the London 2012 Olympic and Paralympic Games (the ‘Games’). The research examines commuter travel behaviour through a panel approach enabling an understanding of individual behaviour across three waves (before, during and after), with the study utilising unique access to a Transport for London panel study (n=1132). The findings indicate that a substantial amount of change occurred during the Games (54% made at least one change), with reducing or re-timing journeys being the most likely adaptations made. A key objective of this work was to advance the discussion about the theoretical constructs that are most applicable in the study of behaviour change associated with disruptive events, which was done through the application and critical evaluation of the Transtheoretical Model. The insights from the stages of change element of the model were relatively limited but the analysis shows significant differences in the underlying factors explaining change according to the type of change made (reduce, re-time, re-mode and re-route). Whilst the long-term behavioural impacts of events like the Games appear small, the study has uncovered a need to consider these behavioural choices as distinct rather than under the collective term of “travel behaviour change”, as is current practice

Chronic Maternal Depression Is Associated with Reduced Weight Gain in Latino Infants from Birth to 2 Years of Age

BACKGROUND: Latino children are at increased risk for mirconutrient deficiencies and problems of overweight and obesity. Exposures in pregnancy and early postpartum may impact future growth trajectories. OBJECTIVES: To evaluate the relationship between prenatal and postnatal maternal depressive symptoms experienced in pregnancy and infant growth from birth to 2 years of age in a cohort of Latino infants. METHODS: We recruited pregnant Latina mothers at two San Francisco hospitals and followed their healthy infants to 24 months of age. At 6, 12 and 24 months of age, infants were weighed and measured. Maternal depressive symptoms were assessed prenatally and at 4-6 weeks postpartum. Women who had high depressive symptoms at both time periods were defined as having chronic depression. Logistic mixed models were applied to compare growth curves and risk for overweight and underweight based on exposure to maternal depression. RESULTS: We followed 181 infants to 24 months. At 12 and 24 months, respectively, 27.4% and 40.5% were overweight, and 5.6% and 2.2% were underweight. Exposure to chronic maternal depression was associated with underweight (OR = 12.12, 95%CI 1.86-78.78) and with reduced weight gain in the first 2 years of life (Coef = -0.48, 95% CI -0.94-0.01) compared with unexposed infants or infants exposed to episodic depression (depression at one time point). Exposure to chronic depression was also associated with reduced risk for overweight in the first 2 years of life (OR 0.28, 95%CI 0.03-0.92). CONCLUSIONS: Exposure to chronic maternal depression in the pre- and postnatal period was associated with reduced weight gain in the first two years of life and greater risk for failure to thrive, in comparison with unexposed infants or those exposed episodically. The infants of mothers with chronic depression may need additional nutritional monitoring and intervention

Event satisfaction and behavioural intentions: examining the impact of the London 2012 Olympic Games on participation in sport

peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=resm2