This thesis concerns optimization of structures considering various uncertainties. The overall objective is to find methods to create solutions that are optimal both in the sense of handling the typical load case and minimising the variability of the response, i.e. robust optimal designs. Traditionally optimized structures may show a tendency of being sensitive to small perturbations in the design or loading conditions, which of course are inevitable. To create robust designs, it is necessary to account for all conceivable variations (or at least the influencing ones) in the design process. The thesis is divided in two parts. The first part serves as a theoretical background to the second part, the two appended articles. This first part includes the concept of robust design, basic statistics, optimization theory and meta modelling. The first appended paper is an application of existing methods on a large industrial example problem. A sensitivity analysis is performed on a Scania truck cab subjected to impact loading in order to identify the most influencing variables on the crash responses. The second paper presents a new method that may be used in robust optimizations, that is, optimizations that account for variations and uncertainties. The method is demonstrated on both an analytical example and a Finite Element example of an aluminium extrusion subjected to axial crushing. / ROBDES

The ecotoxicological literature reveals that countless researchers worldwide rely upon informally identified commercial earthworm stocks for laboratory bioassays. The primary aim of this study was to investigate laboratory and commercial stocks of Eisenia species used in South Africa in order to confirm their taxonomy, assess their levels of genetic richness and differentiation. To do so, populations of potential Eisenia andrei and Eisenia fetida were purchased/obtained from vermiculturists and laboratories from four provinces of South Africa. DNA barcoding was used to investigate these taxonomic uncertainties. The COI gene was partially amplified and sequenced in selected earthworms from eight local populations (focal groups) and two European laboratory stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences generated. One of these haplotypes was found to belong to the Megascolecidae Perionyx excavatus. The remaining eight haplotypes belonged to the genus Eisenia although only a single Eisenia fetida haplotype, represented by six specimens, was found in one of the European populations. The other seven haplotypes, all occurring in South Africa, were Eisenia andrei. No Eisenia fetida was found in the South African based populations. One of the commercial stocks from South Africa and a laboratory culture from Europe were mixes of E. andrei - P. excavatus and E. andrei – E. fetida respectively. COI haplotype numbers were limited to two to three distinct sequences within each of the local groups. This translated into a haplotype diversity (H) lower than 0.45 in all the populations, which is very low when compared to other such earthworm studies in which COI polymorphism has been investigated. Of all the local populations investigated, only the lone field population included was genetically divergent from the other populations. This was explained by the haplotype distribution across the populations which indicated that this population was the only one not harbouring the haplotype which represented 75% or more of the COI sequences within the local populations. Because research suggests that earthworm populations with limited genetic diversity may suffer inbreeding depression which could affect traits such as reproduction and survival, the secondary aim was to test whether metal-sensitive earthworms were overly present in the populations investigated. To do so, the three most common COI haplotypes identified between the 8 local populations of E. andrei (called Hap1, Hap2 and Hap3) were paired up and exposed to cadmium. A total of six couples were exposed to 0, 25, 50 and 100 mg Cd/kg for 4 weeks at 20ºC. The survival, biomass variation, cocoon production and cocoon hatching success were assessed for all the couples. The results indicated that couple 6 (Hap3xHap3) was the most sensitive for three of the endpoints assessed whereas couple 4 (Hap1 x Hap3) was the least sensitive. Cocoon hatching success could not help differentiate the couples. The analysis of Cd tissue contents revealed that with increasing Cd concentration, Cp6 (Hap3xHap3) could accumulate significantly more Cd than any other couple (p ≤ 0.01). These findings indicate that earthworm populations may carry intrinsically metal-tolerant and metal-sensitive genotypes. In the context of ecotoxicological testing, the present results underline the importance of using genetically diverse populations in laboratory testing as Cp6 (Hap3xHap3) could have suffered from the deleterious effect of inbreeding. Because E. fetida could not be found in the local populations assessed, it is recommended that further earthworm DNA barcoding studies, covering a more representative geographical area of South Africa and including more field populations of Eisenia spp. be conducted. Because of the occurrence of genetic homogeneity in the populations studied, it is suggested that captive breeding initiatives be established using specimens obtained from several geographically distant field and reared populations. Further research investigating patterns of Cd accumulation/excretion kinetics between the Cd-tolerant and Cd-sensitive individuals reported in the present study, should be conducted to help determine whether inbreeding is the sole factor explaining the observed genotypic responses to Cd. Finally, the necessity of a standardised earthworm barcoding protocol that could help both to properly identify laboratory earthworm stocks and to select genetically diverse stocks suitable for laboratory testing, is discussed together with the relevance of the present work to ecotoxicological testing in general. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

The ecotoxicological literature reveals that countless researchers worldwide rely upon informally identified commercial earthworm stocks for laboratory bioassays. The primary aim of this study was to investigate laboratory and commercial stocks of Eisenia species used in South Africa in order to confirm their taxonomy, assess their levels of genetic richness and differentiation. To do so, populations of potential Eisenia andrei and Eisenia fetida were purchased/obtained from vermiculturists and laboratories from four provinces of South Africa. DNA barcoding was used to investigate these taxonomic uncertainties. The COI gene was partially amplified and sequenced in selected earthworms from eight local populations (focal groups) and two European laboratory stocks (non-focal groups). Only nine COI haplotypes were identified from the 224 sequences generated. One of these haplotypes was found to belong to the Megascolecidae Perionyx excavatus. The remaining eight haplotypes belonged to the genus Eisenia although only a single Eisenia fetida haplotype, represented by six specimens, was found in one of the European populations. The other seven haplotypes, all occurring in South Africa, were Eisenia andrei. No Eisenia fetida was found in the South African based populations. One of the commercial stocks from South Africa and a laboratory culture from Europe were mixes of E. andrei - P. excavatus and E. andrei – E. fetida respectively. COI haplotype numbers were limited to two to three distinct sequences within each of the local groups. This translated into a haplotype diversity (H) lower than 0.45 in all the populations, which is very low when compared to other such earthworm studies in which COI polymorphism has been investigated. Of all the local populations investigated, only the lone field population included was genetically divergent from the other populations. This was explained by the haplotype distribution across the populations which indicated that this population was the only one not harbouring the haplotype which represented 75% or more of the COI sequences within the local populations. Because research suggests that earthworm populations with limited genetic diversity may suffer inbreeding depression which could affect traits such as reproduction and survival, the secondary aim was to test whether metal-sensitive earthworms were overly present in the populations investigated. To do so, the three most common COI haplotypes identified between the 8 local populations of E. andrei (called Hap1, Hap2 and Hap3) were paired up and exposed to cadmium. A total of six couples were exposed to 0, 25, 50 and 100 mg Cd/kg for 4 weeks at 20ºC. The survival, biomass variation, cocoon production and cocoon hatching success were assessed for all the couples. The results indicated that couple 6 (Hap3xHap3) was the most sensitive for three of the endpoints assessed whereas couple 4 (Hap1 x Hap3) was the least sensitive. Cocoon hatching success could not help differentiate the couples. The analysis of Cd tissue contents revealed that with increasing Cd concentration, Cp6 (Hap3xHap3) could accumulate significantly more Cd than any other couple (p ≤ 0.01). These findings indicate that earthworm populations may carry intrinsically metal-tolerant and metal-sensitive genotypes. In the context of ecotoxicological testing, the present results underline the importance of using genetically diverse populations in laboratory testing as Cp6 (Hap3xHap3) could have suffered from the deleterious effect of inbreeding. Because E. fetida could not be found in the local populations assessed, it is recommended that further earthworm DNA barcoding studies, covering a more representative geographical area of South Africa and including more field populations of Eisenia spp. be conducted. Because of the occurrence of genetic homogeneity in the populations studied, it is suggested that captive breeding initiatives be established using specimens obtained from several geographically distant field and reared populations. Further research investigating patterns of Cd accumulation/excretion kinetics between the Cd-tolerant and Cd-sensitive individuals reported in the present study, should be conducted to help determine whether inbreeding is the sole factor explaining the observed genotypic responses to Cd. Finally, the necessity of a standardised earthworm barcoding protocol that could help both to properly identify laboratory earthworm stocks and to select genetically diverse stocks suitable for laboratory testing, is discussed together with the relevance of the present work to ecotoxicological testing in general. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Introduction. A mother’s verbal and non-verbal behaviour towards her infant is known as maternal responsiveness (MR). Positive MR is associated with better child social and emotional development (SED). A mother’s ability to accurately recognise emotions is thought to enhance MR. Method. Data from 1,122 mother-infant interactions from a longitudinal birth cohort study, was used firstly to examine whether positive MR at 12 months was associated with better child and adolescent SED, and secondly to explore whether better maternal facial and vocal expression recognition at 151 months was associated with positive MR and child SED. MR was measured using the Thorpe Interaction Measure (TIM) from observed mother-infant interactions and SED from questionnaire data adjusting for potential confounding variables. A test of facial expression recognition was used with vocal expression recognition additionally used in mothers. Results. Logistic regression revealed that positive MR was associated with positive SED outcomes in childhood but there was little effect in adolescence. Positive MR was associated with mothers having better facial and vocal expression recognition at 151 months and these recognition skills were associated with children showing less emotional problems at 158 months independent of MR. Adjustments for confounding variables had no effect on these results. Conclusion: These findings support the benefit of positive MR on a child’s SED in middle childhood. Further, the findings suggest that a mother’s facial and vocal expression recognition skills are important to both MR and a child’s SED. Limitations include subjective reporting of SED.

Assessments designed to estimate the probability of sexual offense recidivism have gained popularity due to research that suggests these instruments are psychometrically sound for this purpose. The Static-2002 (Hanson & Thornton, 2003), an actuarial instrument of sexual recidivism, has been validated in specific populations, but in the absence of multicultural populations. It is necessary to establish the validity of the Static-2002 for a multicultural population, especially considering the increasing impetus to mandate measures of sexual recidivism. This study was designed to assess the predictive validity of the Static-2002 as an actuarial instrument that estimates the probability of sexual, violent, and general recidivism within a multicultural population. Recent criminal histories and de-identified archival records of 103 adult sex offenders were used to complete demographic questionnaires and to calculate retroactive predictive accuracy scores for the Static-2002. Records were obtained from a private practice office in South Florida, which provides outpatient treatment to conditionally released offenders. Hypothesis testing utilized a receiver operating characteristic area under the curve (ROC AUC) analysis to examine the discriminating power of the Static-2002 and to identify optimal cutoff values for each risk category. These cutoff values were then compared to the established Static-2002 risk categories to evaluate the cutoff scores' congruency. For this sample population, resulting ROC AUC values indicated the predictive accuracy of the Static-2002 to be moderate for any (including general; .67) offense recidivism, and high for violent recidivism (.74). However, the Static-2002 was ineffective for predicting sexual recidivism among this sample population since the predictive accuracy of the ROC area for sexual reoffenses was not statistically significant above chance (p = .07). The four Static-2002 risk categories derived for this study are: low, moderate-low, moderate-high, and high. When compared with the established Static-2002 risk categories, this study's risk categories were found to be mostly concurrent with the established categories. Similar to previous research, this study found that when the sample population differs racially/ethnically from the normed population (60% of this study's participants were Hispanic), the Static-2002 was ineffective for accurately predicting sexual reoffending. However, the Static-2002 effectively predicted violent and general recidivism with this sample population.

<p>Our media is saturated with claims of ``facts'' made from data. Database research has in the past focused on how to answer queries, but has not devoted much attention to discerning more subtle qualities of the resulting claims, e.g., is a claim ``cherry-picking''? This paper proposes a Query Response Surface (QRS) based framework that models claims based on structured data as parameterized queries. A key insight is that we can learn a lot about a claim by perturbing its parameters and seeing how its conclusion changes. This framework lets us formulate and tackle practical fact-checking tasks --- reverse-engineering vague claims, and countering questionable claims --- as computational problems. Within the QRS based framework, we take one step further, and propose a problem along with efficient algorithms for finding high-quality claims of a given form from data, i.e. raising good questions, in the first place. This is achieved to using a limited number of high-valued claims to represent high-valued regions of the QRS. Besides the general purpose high-quality claim finding problem, lead-finding can be tailored towards specific claim quality measures, also defined within the QRS framework. An example of uniqueness-based lead-finding is presented for ``one-of-the-few'' claims, landing in interpretable high-quality claims, and an adjustable mechanism for ranking objects, e.g. NBA players, based on what claims can be made for them. Finally, we study the use of visualization as a powerful way of conveying results of a large number of claims. An efficient two stage sampling algorithm is proposed for generating input of 2d scatter plot with heatmap, evalutaing a limited amount of data, while preserving the two essential visual features, namely outliers and clusters. For all the problems, we present real-world examples and experiments that demonstrate the power of our model, efficiency of our algorithms, and usefulness of their results.</p> / Dissertation

Literature Review: Anhedonia, the loss of interest or pleasure in usually pleasurable activities, is a core symptom of depression and is associated with a reduction in positive affect (PA). Repetitive negative thought (RNT) is implicated in the development and maintenance of psychiatric disorders. It has been hypothesised that RNT causally contributes to anhedonia. The aim of this review was to explore this relationship to answer two questions: Is there a relationship between RNT and anhedonia? Does RNT causally contribute to anhedonia? Review inclusion criteria were: studies using standardised measures to report a relationship between RNT and anhedonia or reduced PA. Results suggest that cross-sectional and longitudinal studies identify a relationship between RNT and anhedonia. Preliminary evidence from experimental studies shows that RNT causally contributes to anhedonia. Limitations within the field are that anhedonia is rarely measured directly or behaviourally. Future research is warranted to explore the relationship between RNT and anhedonia with a particular focus on direct and behavioural measures of anhedonia. Empirical Paper: It is hypothesised that repetitive negative thought (RNT) causally contributes to anhedonia. There is cross-sectional and longitudinal evidence of this relationship, but it has not previously been investigated directly using experimental methods. In the present study, student participants were randomly assigned to an unresolved goal (RNT) manipulation (n = 43) or resolved goal (control) manipulation (n =41) prior to completing a reward sensitivity task. This task has been reliably found to train a response bias towards the stimuli that is differentially positively reinforced, with both depression and self-reported anhedonia associated with a reduced response bias. The unresolved goal versus resolved goal manipulation was effective, with the unresolved condition producing significantly higher levels of RNT during the reward sensitivity task relative to the resolved condition. Inconsistent with study predictions, there was no significant difference between the conditions on response bias, although there were trend findings, which tentatively suggest that RNT may influence anhedonia. Potential accounts for the null findings and future research are discussed.

Soil respiration is an important source of atmospheric CO2, with the potential for large positive feedbacks with global warming. The size of these feedbacks will depend on the relative sensitivity to temperature of very large global pools of highly stable soil organic matter (SOM), with residence times of centuries or longer. Conflicting evidence exists as to the relationships between temperature sensitivity of respiration and stability of SOM, as well as the temperature sensitivity of individual stabilisation mechanisms. This PhD considers the relationship between different stabilisation mechanisms and the temperature sensitivity of SOM decomposition. I used physical fractionation to isolate SOM pools with a variety of turnover rates, from decadal to centennially cycling SOM, in a peaty gley topsoil from Harwood Forest. Mean residence times of SOM as determined by 14C dating was most strongly affected by depth, providing stability on a millienial scale, while OM-mineral associations and physical protection of aggregates provided stability to around 500 years. Chemical characteristics of organic material in these fractions and whole soils (13C CP-MAS NMR spectroscopy, mass spectrometry, FTIR spectroscopy, thermogravimetric analysis, ICP-OES) indicated the relative contribution of different stabilisation mechanisms to the longevity of each of these fractions. Two long-term incubations of isolated physical fractions and soil horizons at different temperatures provided information about the actual resistance to decomposition in each SOM pool, as well as the temperature sensitivity of respiration from different pools. Naturally 13C-labelled labile substrate additions to the mineral and organic horizons compared the resistance to priming by labile and recalcitrant substrates. Manipulation of soil pore water was investigated as a method for isolating the respiration of SOM from physically occluded positions within the soil architecture. Contadictory lines of evidence emerged on the relative stability of different SOM pools from 14C dating, incubation experiments and chemical characterisation of indicators of stability. This led to the interpretation that physical aggregate protection primarily controls SOM stability within topsoils, while mineral and Fe oxide stability provides more lasting stability in the mineral horizon. Less humified and younger SOM was found to have a higher sensitivity to temperature than respiration from well-humified pools, in contrast to predictions from thermodynamics.

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This paper examines in a descriptive manner how two groups of variables, institutional and socio-economic, correlate with voter turnout respectively and if their magnitude have changed over time in OECD countries. Previous research is often based on data from the 70’s and 80’s. Since then, voter turnout in democratic countries has decreased and more citizens do not use their fundamental democratic right of being involved in the process of choosing their representatives. To answer the paper hypotheses i.e. analyzing what factors that correlates with voter turnout, panel data between 1980 and 2012 are used which is estimated by an OLS approach. The outcome of the empirical estimations indicates that 13 out of 19 variables have a significant relationship with turnout. Most of the variables magnitudes are a bit lower than previous literature. From the time sensitivity analysis the result indicates that voters are less influenced by the significant variables that focus on the voting cost. It seems that voters in the 21st century meet voting costs in different manner than previously.