To help contemporary couples successfully navigate the 21st Century’s individualistic, diverse, multicultural, global, postmodern relationship environment, individual, couple, and family counselors, marriage therapists, couple therapists, family psychologists, relationship coaches, marriage educators, counselor educators, and other helping professionals need to understand and promote the positive, strengths-based, holistic, and wellbeing development of couple relationships to help them succeed and flourish in the long- term. This qualitative, narrative, visual autoethnography explores the researcher’s own experience of the culture of her 27-year long soul mate relationship with her partner through the lens of Positive and Holistic Couple Relationship Development Theory (PHRDT), its 7- phase Soul Mates Model, including encounter and dating, commitment, intimacy, building a life, shadow and adversity, renewal, and completion, resulting in the metaphorical development of the philosopher’s stone or gold of the philosophers, and its 12 positive relationship development principles. The study also explores the meanings derived from 8 alchemical pictograms associated with the Soul Mates Model’s 7 phases, which of the 12 positive principles played out in her relationship, and the effectiveness of her and her partner’s deliberate efforts at positive relationship building, as well as how these experiences may inform her teaching and practice. Based on the findings, which include the recall of fourteen years of spiritual, psychic, and visionary encounters with her partner before they met, the researcher concludes that she and her partner are not only soul mates engaged in the soul mating process, but also twin souls, linked together by an unfathomable bond that has helped them develop intimacy, remain bonded through adversity, and flourish as a couple in the long-term. Additionally, the researcher concludes that the Soul Mates Model and 8 alchemical pictograms are useful mythopoeic tools to explore the positive and holistic development of the couple relationship, that all 12 positive principles played out in her relationship, and that the process of soul mating may be taught to others with help of strategic positive, holistic, and mythopoeic interventions, yet that twin- soulship cannot be taught. She thus concludes that soul mates can be grown, yet twin souls must be born.

Recent studies of fcc metals with dense twins (~10 nm spacing) have revealed impressive mechanical properties, along with improved ductility and electrical conductivity in comparison to nanocrystalline metals with similar feature sizes. Many important fcc metals could benefit from these “nanotwinned” microstructures, however, not all fcc metals readily form such twins. The tendency of fcc metals to form twin boundaries is related to the twin boundary energy; those with low twin boundary energy, such as silver (Ag), easily form twins. Increasing twin boundary energy interferes with twin formation, to the point that in metals with high twin boundary energy, like aluminum (Al), twins are quite rare. This thesis focuses on the synthesis of nanotwinned Ag and Al via physical vapor deposition. Nanotwinned Ag is readily fabricated, however, a template approach had to be developed to induce twins in Al. The microstructures and their relationships to observed mechanical properties are also discussed. Grain boundaries interfere with dislocation transmission by posing a slip system discontinuity between grains. Twin boundaries are a special class of grain boundaries in which the grains on either side of the boundary are related by mirror symmetry. Twin boundaries inhibit dislocation transmission, providing strength in the same manner as grain boundaries. However, their symmetrical structure reduces the free volume and grain boundary energy. Accordingly, coherent twin boundaries are often more energetically stable than grain boundaries, and their coherency allows plasticity mechanisms to remain active under conditions where such mechanisms may be inhibited at grain boundaries. Hence, twin boundaries may provide a metal with unique combinations of high strength and good ductility, conductivity, and thermal stability.

No description available.

This study, presented in the format of three articles, contributed to the measuring of psycho-social well-being in Afri Twin schools. The literature points to a serious lack of studies measuring the psychosocial well-being of teachers and possible interventions to alleviate their challenges. The context of the study is the Afri Twin project. The Afri Twin project is a collaboration between a British school, a South African town/city school, and/or a school from a township or rural community in South Africa. The intention of Afri Twin is to create camaraderie between school principals, teachers and learners/students in South African and British schools. As the relationships between the different schools develop, schools will have the opportunity to visit one another, exchange experiences and teaching ideas, and gain first-hand experience of the different conditions in which the individual schools function. The first article determined the psychometric properties of the Adapted and Revised Organisational Climate Description Questionnaire (AAROCDQ), and was validated for school climate as experienced by teachers. Participants were 394 school teachers (72 male and 322 female) from 40 schools in South Africa. The AAROCDQ correlated positively with other measures of optimal functioning (The Mental Health Continuum - Short Form MHCSF], the Coping Self-Efficacy Scale [CSE], and the Core Self-Evaluations Scale [CSES]). The internal consistency and factor structure were determined as well as the evidence for concurrent validity. The results of the study indicated that the AAROCDQ was reliable and also indicated construct validity in a sample of South African teachers. It was concluded that further validation and standardisation of the AAROCDQ could be done in mixed method studies as well as that future studies could further analyse the scale on item level to give a more coherent perspective on the psychosocial well-being of teachers. The second article explored the prevalence of well-being in Afri Twin and non Afri Twin teachers. A quantitative survey design was implemented and the sample consisted of 97 Afri Twin teachers (20 male and 77 female) and 297 non Afri Twin teachers (52 male and 245 female) from 40 South African schools (13 Afri Twin and 27 non Afri Twin). The MHC-SF, the CSE and CSES were used to determine the well-being of teachers. The results indicated a moderate to high level of well-being, with an almost significant difference in social well-being and core self-evaluations between Afri Twin and non Afri Twin teachers. It was concluded that the social context of the 'twinning' process in Afri Twin schools could influence the social well-being of teachers positively. The aim of the third article was two-fold. Firstly principals', teachers' and learners' experiences of the Afri Twin project were investigated, and secondly the aim was to develop an intervention for resilience in schools participating in the Afri Twin project. The sample consisted of 158 teachers (42 male and 116 female), 14 school principals (10 male and 4 female), and 65 learners (34 boys and 31 girls). The results indicated that leadership, school climate (culture), the people that are involved, and promoting optimism and self-efficacy through support and sharing are essential for the development or improvement of resilience in schools through the Afri Twin project. The main conclusion from this thesis is that teachers' experience of the school as an environment in which they work is influenced by such factors as social support and sharing that can influence the psychological well-being (specifically social well-being) of the educators. This is indicated by the correlation between the findings in article 3 which support the findings in article 2. The benefits from being involved with a project like the Afri Twin could also influence the resilience of the educators and learners/students. / Thesis (PhD (Psychology))--North-West University, Potchefstroom Campus, 2013.

This study, presented in the format of three articles, contributed to the measuring of psycho-social well-being in Afri Twin schools. The literature points to a serious lack of studies measuring the psychosocial well-being of teachers and possible interventions to alleviate their challenges. The context of the study is the Afri Twin project. The Afri Twin project is a collaboration between a British school, a South African town/city school, and/or a school from a township or rural community in South Africa. The intention of Afri Twin is to create camaraderie between school principals, teachers and learners/students in South African and British schools. As the relationships between the different schools develop, schools will have the opportunity to visit one another, exchange experiences and teaching ideas, and gain first-hand experience of the different conditions in which the individual schools function. The first article determined the psychometric properties of the Adapted and Revised Organisational Climate Description Questionnaire (AAROCDQ), and was validated for school climate as experienced by teachers. Participants were 394 school teachers (72 male and 322 female) from 40 schools in South Africa. The AAROCDQ correlated positively with other measures of optimal functioning (The Mental Health Continuum - Short Form MHCSF], the Coping Self-Efficacy Scale [CSE], and the Core Self-Evaluations Scale [CSES]). The internal consistency and factor structure were determined as well as the evidence for concurrent validity. The results of the study indicated that the AAROCDQ was reliable and also indicated construct validity in a sample of South African teachers. It was concluded that further validation and standardisation of the AAROCDQ could be done in mixed method studies as well as that future studies could further analyse the scale on item level to give a more coherent perspective on the psychosocial well-being of teachers. The second article explored the prevalence of well-being in Afri Twin and non Afri Twin teachers. A quantitative survey design was implemented and the sample consisted of 97 Afri Twin teachers (20 male and 77 female) and 297 non Afri Twin teachers (52 male and 245 female) from 40 South African schools (13 Afri Twin and 27 non Afri Twin). The MHC-SF, the CSE and CSES were used to determine the well-being of teachers. The results indicated a moderate to high level of well-being, with an almost significant difference in social well-being and core self-evaluations between Afri Twin and non Afri Twin teachers. It was concluded that the social context of the 'twinning' process in Afri Twin schools could influence the social well-being of teachers positively. The aim of the third article was two-fold. Firstly principals', teachers' and learners' experiences of the Afri Twin project were investigated, and secondly the aim was to develop an intervention for resilience in schools participating in the Afri Twin project. The sample consisted of 158 teachers (42 male and 116 female), 14 school principals (10 male and 4 female), and 65 learners (34 boys and 31 girls). The results indicated that leadership, school climate (culture), the people that are involved, and promoting optimism and self-efficacy through support and sharing are essential for the development or improvement of resilience in schools through the Afri Twin project. The main conclusion from this thesis is that teachers' experience of the school as an environment in which they work is influenced by such factors as social support and sharing that can influence the psychological well-being (specifically social well-being) of the educators. This is indicated by the correlation between the findings in article 3 which support the findings in article 2. The benefits from being involved with a project like the Afri Twin could also influence the resilience of the educators and learners/students. / Thesis (PhD (Psychology))--North-West University, Potchefstroom Campus, 2013.

One of the current problems faced by mankind is the problem of safe disposal of waste rubber. Statistics show that the number of waste tires is continuously increasing at a very rapid rate. Since rubber materials do not decompose easily (due to their crosslinked structure), they end up being a serious ???environmental problem???. An intuitive solution to prevent the accumulation of the scrap tires is to continuously reuse them. A new patented reclamation method was discovered in our laboratory, which makes use of a twin screw extruder (TSE) in order to produce reclaimed rubber (referred as devulcanized rubber (DR) from here on) of very high quality. Also, this method has proven to be more economical than other commercial reclaiming methods. Products made solely from a reclaimed material face challenges from those made by virgin materials because of relatively poor properties. However, the striking advantage of using reclaimed rubbers is the cost reduction. Hence, it is important to work on establishing methods by which these reclaimed rubbers could be efficiently used and incorporated into present day products. The deterioration of properties could be minimized by blending them with varying amounts of other materials. A possibility in this direction is manufacturing of thermoplastic vulcanizates (TPVs) using reclaimed rubber and general purpose thermoplastics. In accordance with this idea, the focus of this research is to prepare DR and polypropylene (PP) based TPVs. DR is unique as the rubber itself consists of two phases- one phase consisting of uncrosslinked (including devulcanized rubber molecules), and the other phase consisting of crosslinked (un-devulcanized) rubber. These un-devulcanized crumbs act as stress concentrators because they do not break-up easily, and lead to poor physical properties. Hence, this project tries to find out ways to increase the interfacial adhesion between the rubber and PP by using reactive and non-reactive techniques. Preliminary experiments were carried out in a batch mixer to compare DR and rubber crumb (CR). DR based TPVs showed better properties than CR based TPVs, however, the properties were not useful for commercial applications. Sulphur based dynamic vulcanization was studied in a batch mixer and found to be not effective in improving the properties of DR based blends. On the other hand, DCP/ sulphur based curing system was found to show significant improvement in properties. Therefore, DCP/sulphur based curing package was studied in detail on the blends consisting of DR and PP. The optimum ratio of DCP/sulphur was found to vary depending on the ratio of DR/PP. A hypothesis regarding the mechanism of DCP/sulphur curing has been proposed, which seem to correlate well with the experimental results observed. Additionally, it was determined that DR prepared from tire rubber (DRT) performed better than DR prepared from waste EPDM (DRE) for the curing system used. Accordingly, experiments on a TSE were carried out using DRT and a combination of compatibilizing resins and curatives. This combination showed a drastic improvement in blends properties and once again the optimum ratio of compatibilizing resins seemed to depend on the ratio of DRT/PP. As a result of the work, successful strategies based on reactive compatibilization techniques were developed in order to prepare useful TPVs having up to 70% DR. A series of compatibilization techniques has been evaluated using design of experiments and various characterization techniques such as mechanical tests, scanning electron microscopy, thermal analysis and crosslink density measurements. This led to the development of a formulation, which could improve the blend properties significantly. A tensile strength of around 10 MPa and an elongation-at-break of 150-180 % could be achieved for devulcanized rubber (70%) based TPVs, which has broadened the scope for its commercial applications. In addition to that, the process was established on a TSE that has enabled a continuous and steady production of these TPVs with reasonable throughputs.

Twin-screw pumps are positive displacement machines. Two meshing screws connected by timing gears convey the fluid trapped in the screw chambers axially from suction to discharge and force it out against the back pressure. Because of the screw geometry, the circumferential pressure field around the screws is not balanced, resulting in net dynamic and static pressures applied on the rotors. The research work presented here aims at building and verifying a model to predict both: (1) the exciting lateral hydrodynamic forces produced by the unbalanced pressure field, and (2) the rotor response due to those forces. The model rests on the screw pump hydraulic models for predicting the pressure in the screw chambers as a function of the discharge pressure. These models are extended to predict the steady state dynamic pressure field as a function of the rotational angle of the rotor. The dynamic force resulting from the dynamic pressure field is calculated and applied to the rotor as a set of super-synchronous periodic forces. The structural model of the screw, although nonsymmetrical, was found to be accurately represented by an axisymmetric equivalent structure. The rotor response to the dynamic super-synchronous forces is calculated to predict the pump rotordynamic behavior. The work in this dissertation presents: (1) the axisymmetric structural model of the rotors (2) the proposed dynamic pressure model, (3) the screw pump rotor response, (4) the experimental validation of the dynamic pressure model and rotor response. The topic of twin-screw pump rotordynamics is absent from the literature. The original contribution of the work presented in this dissertation to the field of rotordynamics includes: (1) demonstrating the adequacy of an axisymmetric model for modeling the screw section, (2) developing a model for predicting the dynamic pressure field around the screws, (3) characterization of the dynamic forces (synchronous and its harmonics) applied at the screw pump rotors, (4) predicting the dynamic response of twin-screw pump rotors due to hydrodynamic forces, (5) measuring the axial dynamic pressure in two circumferential planes around the screws to verify pressure predictions, (6) measuring the dynamic response of twin-screw pump rotor.

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / A range of epidemiological, clinical and experimental studies have demonstrated that exposure of an embryo to a suboptimal environment in vivo or ex vivo during early embryo development is associated with altered development of cardiovascular, neuroendocrine and metabolic disorders in adult life. A number of perturbations during early embryo development result in developmental adaptations by the embryo to ensure immediate survival, whilst programming the embryo for altered fetal and placental development, resulting in the eventual onset of adult disease. It has been previously shown that maternal nutrient restriction during the periconceptional period results in a hyperactivation of the pituitary - adrenal axis and increased mean arterial blood pressure in twin but not singleton pregnancies. It was therefore the first aim of this thesis to interrogate the impact of maternal undernutrition during the periconceptional period (defined as from at least 45 days prior until 7 days after conception) on fetal and placental development during early pregnancy at - day 55 of pregnancy, which coincides with the period of maximal placental growth. In Chapter 2, it has been demonstrated that there are important relationships between maternal weight gain during the periconceptional period and feto-placental growth during the first - 55 days of pregnancy and that periconceptional undernutrition has a differential effect on these relationships in singleton and twin pregnancies. In singleton pregnancies, periconceptional undernutrition disrupts the relationship between maternal weight gain during the periconceptional period and utero-placental growth and in twin pregnancies, periconceptional undernutrition results in the emergence of an inverse relationship between maternal weight gain during early pregnancy and uteroplacental growth and in a dependence of fetal growth on placental growth. (Chapter 2) In order to investigate the origins of the physiological adaptations that lead to the development of hyperactivation of the pituitary - adrenal axis and increased mean arterial blood pressure in late gestational fetuses after exposure as an embryo to periconceptional undernutrition, we investigated the development and steroidogenic capacity of the fetal adrenal gland and development of the fetal heart and kidney at - 55 days gestation (Chapter 3 and 4). The relative weight of the fetal adrenal and adrenal IGF-1, IGF-1 R, IGF-2, IGF-2R and CYP 17 mRNA expression were lower in twin compared to singleton fetuses. There was evidence that in control singletons, IGF-2R expression plays an important role in the regulation of adrenal growth and CYP 17 mRNA expression during early pregnancy. In control twins, however, whilst there was a significant positive relationship between adrenal CYP 17 and IGF-2 mRNA expression, adrenal weight was directly related to the level of adrenal IGF-1 mRNA expression. There was no effect of periconceptional undernutrition on the level of expression of any of the placental or adrenal genes in the study. In PCUN ewes, carrying singletons, however, there was a loss of the relationships between either adrenal IGF-2, IGF-2R and IGF-1 mRNA expression and adrenal growth and CYP 17 expression which were present in control singletons. Similarly in ewes carrying twins, maternal undernutrition during the periconceptional period resulted in the loss of the relationships between adrenal growth and IGF-1 expression and between _ adrenal CYP 17 and IGF-2 expression which were present in control twin fetuses. Whilst there was no effect of fetal number on fetal heart growth at - d55 in twin fetuses, there was a direct relationship between relative fetal heart and adrenal weights, which was present in both the PCUN and control groups. There was also a significant inverse relationship between maternal weight at conception and relative fetal heart weight in PCUN twin, but not PCUN singleton or control fetuses (Chapter 3). In control pregnancies maternal weight gain during the periconceptional period is inversely related to the relative weight of the fetal kidney at -55d pregnancy. In this group, relative kidney weight was also directly related to renal IGF-1 mRNA expression. In control twins maternal weight gain was inversely related to fetal kidney weight and this effect was ablated when the effects of maternal cortisol was controlled for in the analysis. In the PCUN group, whilst there was an inverse relationship between maternal weight gain during the periconceptional period and relative kidney weight, it was not possible to separate the independent effects of maternal weight loss during the periconceptional period and the subsequent weight gain during the period of refeeding. Renal IGF-1 mRNA expression was higher and renal lGF-1 R and 2R expression were lower in twin fetuses compared to singletons. After exposure to PCUN, renal IGF-1 expression was also higher than in control pregnancies independent of the fetal number (Chapter 4). Superovulation, artificial insemination, embryo transfer and in vitro embryo culture are used in a range of assisted reproductive technologies, and it has been demonstrated that varying the composition of the culture media can result in a change in pre and postnatal development. Culture of sheep embryos in media containing serum is associated with fetal overgrowth which is phenotypic of the Large Offspring Syndrome. It is not known how the combination of superovulation, artificial insemination and embryo transfer alone impacts fetoplacental development in late gestation of the sheep. There have been no studies, however, examining the differential impact of superovulation, artificial insemination and embryo transfer with or without in vitro embryo culture in the absence or presence of human serum on feto-placental development in Singleton and twin pregnancies (Chapter 5). I have therefore tested the hypothesis that superovulation, artificial insemination and embryo transfer with or without in vitro embryo culture in the presence or absence of human serum differentially alters the growth of the placenta, fetus and fetal organs during late gestation when compared to naturally conceived controls and that these effects are different in singleton and twin pregnancies. The fetal weight, CRL and abdominal circumference were significantly larger in IVCHS singleton fetuses. A novel finding in this study was lower fetal weights of twin fetuses in the ET and IVCNS groups compared to NM control twin fetuses. In addition, placental weights were lighter in twin fetuses in the ET, IVCNS and IVCHS treatment groups and this is partially due to a failure to initiate compensatory growth of placentomes in twin pregnancies (Chapter 5). The results of this thesis therefore highlight the complex interactions between the periconceptional environment (in vivo or ex vivo) and embryo or fetal number on the programming fetal and placental development. Maternal undernutrition during the periconceptional period and superovulation, artificial insemination and embryo transfer with or without in vitro culture in the absence or presence of serum alters fetal development, and I have demonstrated that these changes in fetal growth can be explained by changes in placental growth trajectory. Furthermore, a novel finding of this study is that perturbations of the periconceptional environment affect feto-placental development differently in singleton and twin pregnancies. / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2006

Title page, table of contents and abstract only. The complete thesis in print form is available from the University of Adelaide Library. / A range of epidemiological, clinical and experimental studies have demonstrated that exposure of an embryo to a suboptimal environment in vivo or ex vivo during early embryo development is associated with altered development of cardiovascular, neuroendocrine and metabolic disorders in adult life. A number of perturbations during early embryo development result in developmental adaptations by the embryo to ensure immediate survival, whilst programming the embryo for altered fetal and placental development, resulting in the eventual onset of adult disease. It has been previously shown that maternal nutrient restriction during the periconceptional period results in a hyperactivation of the pituitary - adrenal axis and increased mean arterial blood pressure in twin but not singleton pregnancies. It was therefore the first aim of this thesis to interrogate the impact of maternal undernutrition during the periconceptional period (defined as from at least 45 days prior until 7 days after conception) on fetal and placental development during early pregnancy at - day 55 of pregnancy, which coincides with the period of maximal placental growth. In Chapter 2, it has been demonstrated that there are important relationships between maternal weight gain during the periconceptional period and feto-placental growth during the first - 55 days of pregnancy and that periconceptional undernutrition has a differential effect on these relationships in singleton and twin pregnancies. In singleton pregnancies, periconceptional undernutrition disrupts the relationship between maternal weight gain during the periconceptional period and utero-placental growth and in twin pregnancies, periconceptional undernutrition results in the emergence of an inverse relationship between maternal weight gain during early pregnancy and uteroplacental growth and in a dependence of fetal growth on placental growth. (Chapter 2) In order to investigate the origins of the physiological adaptations that lead to the development of hyperactivation of the pituitary - adrenal axis and increased mean arterial blood pressure in late gestational fetuses after exposure as an embryo to periconceptional undernutrition, we investigated the development and steroidogenic capacity of the fetal adrenal gland and development of the fetal heart and kidney at - 55 days gestation (Chapter 3 and 4). The relative weight of the fetal adrenal and adrenal IGF-1, IGF-1 R, IGF-2, IGF-2R and CYP 17 mRNA expression were lower in twin compared to singleton fetuses. There was evidence that in control singletons, IGF-2R expression plays an important role in the regulation of adrenal growth and CYP 17 mRNA expression during early pregnancy. In control twins, however, whilst there was a significant positive relationship between adrenal CYP 17 and IGF-2 mRNA expression, adrenal weight was directly related to the level of adrenal IGF-1 mRNA expression. There was no effect of periconceptional undernutrition on the level of expression of any of the placental or adrenal genes in the study. In PCUN ewes, carrying singletons, however, there was a loss of the relationships between either adrenal IGF-2, IGF-2R and IGF-1 mRNA expression and adrenal growth and CYP 17 expression which were present in control singletons. Similarly in ewes carrying twins, maternal undernutrition during the periconceptional period resulted in the loss of the relationships between adrenal growth and IGF-1 expression and between _ adrenal CYP 17 and IGF-2 expression which were present in control twin fetuses. Whilst there was no effect of fetal number on fetal heart growth at - d55 in twin fetuses, there was a direct relationship between relative fetal heart and adrenal weights, which was present in both the PCUN and control groups. There was also a significant inverse relationship between maternal weight at conception and relative fetal heart weight in PCUN twin, but not PCUN singleton or control fetuses (Chapter 3). In control pregnancies maternal weight gain during the periconceptional period is inversely related to the relative weight of the fetal kidney at -55d pregnancy. In this group, relative kidney weight was also directly related to renal IGF-1 mRNA expression. In control twins maternal weight gain was inversely related to fetal kidney weight and this effect was ablated when the effects of maternal cortisol was controlled for in the analysis. In the PCUN group, whilst there was an inverse relationship between maternal weight gain during the periconceptional period and relative kidney weight, it was not possible to separate the independent effects of maternal weight loss during the periconceptional period and the subsequent weight gain during the period of refeeding. Renal IGF-1 mRNA expression was higher and renal lGF-1 R and 2R expression were lower in twin fetuses compared to singletons. After exposure to PCUN, renal IGF-1 expression was also higher than in control pregnancies independent of the fetal number (Chapter 4). Superovulation, artificial insemination, embryo transfer and in vitro embryo culture are used in a range of assisted reproductive technologies, and it has been demonstrated that varying the composition of the culture media can result in a change in pre and postnatal development. Culture of sheep embryos in media containing serum is associated with fetal overgrowth which is phenotypic of the Large Offspring Syndrome. It is not known how the combination of superovulation, artificial insemination and embryo transfer alone impacts fetoplacental development in late gestation of the sheep. There have been no studies, however, examining the differential impact of superovulation, artificial insemination and embryo transfer with or without in vitro embryo culture in the absence or presence of human serum on feto-placental development in Singleton and twin pregnancies (Chapter 5). I have therefore tested the hypothesis that superovulation, artificial insemination and embryo transfer with or without in vitro embryo culture in the presence or absence of human serum differentially alters the growth of the placenta, fetus and fetal organs during late gestation when compared to naturally conceived controls and that these effects are different in singleton and twin pregnancies. The fetal weight, CRL and abdominal circumference were significantly larger in IVCHS singleton fetuses. A novel finding in this study was lower fetal weights of twin fetuses in the ET and IVCNS groups compared to NM control twin fetuses. In addition, placental weights were lighter in twin fetuses in the ET, IVCNS and IVCHS treatment groups and this is partially due to a failure to initiate compensatory growth of placentomes in twin pregnancies (Chapter 5). The results of this thesis therefore highlight the complex interactions between the periconceptional environment (in vivo or ex vivo) and embryo or fetal number on the programming fetal and placental development. Maternal undernutrition during the periconceptional period and superovulation, artificial insemination and embryo transfer with or without in vitro culture in the absence or presence of serum alters fetal development, and I have demonstrated that these changes in fetal growth can be explained by changes in placental growth trajectory. Furthermore, a novel finding of this study is that perturbations of the periconceptional environment affect feto-placental development differently in singleton and twin pregnancies. / Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2006

Co-rotating twin-screw extruders are unique and versatile machines that are used widely in the plastics and food processing industries. Due to the large number of operating variables and design parameters available for manipulation and the complex interactions between them, it cannot be claimed that these extruders are currently being optimally utilised. The most significant improvement to the field of twin-screw extrusion would be through the provision of a generally applicable dynamic process model that is both computationally inexpensive and accurate. This would enable product design, process optimisation and process controller design to be performed cheaply and more thoroughly on a computer than can currently be achieved through experimental trials. This thesis is divided into three parts: dynamic modelling, measurement and control. The first part outlines the development of a dynamic model of the extrusion process which satisfies the above mentioned criteria. The dynamic model predicts quasi-3D spatial profiles of the degree of fill, pressure, temperature, specific mechanical energy input and concentrations of inert and reacting species in the extruder. The individual material transport models which constitute the dynamic model are examined closely for their accuracy and computational efficiency by comparing candidate models amongst themselves and against full 3D finite volume flow models. Several new modelling approaches are proposed in the course of this investigation. The dynamic model achieves a high degree of simplicity and flexibility by assuming a slight compressibility in the process material, allowing the pressure to be calculated directly from the degree of over-fill in each model element using an equation of state. Comparison of the model predictions with dynamic temperature, pressure and residence time distribution data from an extrusion cooking process indicates a good predictive capability. The model can perform dynamic step-change calculations for typical screw configurations in approximately 30 seconds on a 600 MHz Pentium 3 personal computer. The second part of this thesis relates to the measurement of product quality attributes of extruded materials. A digital image processing technique for measuring the bubble size distribution in extruded foams from cross sectional images is presented. It is recognised that this is an important product quality attribute, though difficult to measure accurately with existing techniques. The present technique is demonstrated on several different products. A simulation study of the formation mechanism of polymer foams is also performed. The measurement of product quality attributes such as bulk density and hardness in a manner suitable for automatic control is also addressed. This is achieved through the development of an acoustic sensor for inferring product attributes using the sounds emanating from the product as it leaves the extruder. This method is found to have good prediction ability on unseen data. The third and final part of this thesis relates to the automatic control of product quality attributes using multivariable model predictive controllers based on both direct and indirect control strategies. In the given case study, indirect control strategies, which seek to regulate the product quality attributes through the control of secondary process indicators such as temperature and pressure, are found to cause greater deviations in product quality than taking no corrective control action at all. Conversely, direct control strategies are shown to give tight control over the product quality attributes, provided that appropriate product quality sensors or inferential estimation techniques are available.