This thesis investigated reading and related skills in Chinese children learning English as a second language (ESL) in 279 Chinese twin pairs aged from 3 to 11 years. Children were tested twice, a year apart, with measures of visual word recognition, receptive vocabulary, phonological awareness, phonological memory and speech perception in both Chinese and English and Chinese tone awareness. The thesis was divided into two sections with the first section exploring the phenotypic relationships and the second section estimating the genetic and environmental influences. In the first section, the causal relationships among the five ESL skills were modelled (chapter 4) and the relationships between Chinese and ESL skills were sought (chapter 4). In section two, the univariate heritability (chapter 6), the cross-linguistic genetic overlap (chapter 7) and the stability and instability of heritability estimates (chapter 8) for all skills were examined. Findings have shown that ESL speech perception is important to the development of ESL phonological awareness, phonological memory and receptive vocabulary, in turn, has an impact on ESL reading development. Genes play an important role in ESL and Chinese reading development. The differential environmental effects may be due to the differences in the ESL and Chinese acquisition ecologies.

Although previous research has shown a significant association between bulimia nervosa (BN) and drug use disorders (DUD), our knowledge of the underlying causes for this comorbidity remains limited. The purpose of the present study was to investigate possible influences on the comorbidity between BN and DUD. Subjects included 490 monozygotic and 354 dizygotic female twin pairs from the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders. Multiple logistic regression analyses were used to test where putative shared correlates mediated the comorbidity between BN and DUD. Bivariate twin analyses were used to investigate the contribution of genes and environment to the correlation between BN and DUD. Regression analyses indicated a lifetime history of major depression, the personality trait of neuroticism, and childhood sexual abuse significantly mediated the associated between BN and DUD (using BN as the independent variable), while major depression, conduct disorder diagnosis, and childhood sexual abuse most significantly impacted the association when DUD was used as the independent variable. Bivariate twin analyses indicated there is additive genetic and nonshared environmental overlap between BN and DUD with genetic and unique environmental correlations of 0.39 and 0.10, respectively. Results show the reason for the association between BN and DUD is due mostly to overlapping genes with a smaller contribution from nonshared environmental influences. Major depression, the personality trait of neuroticism, and childhood sexual abuse are likely important shared correlates between BN and DUD.

The purpose of this study was to examine the heritability, stability, and outcomes of antisocial behavior from adolescence into adulthood in a longitudinal twin sample. Specifically, the genetic and environmental influences on conduct disorder, adult antisocial behavior, and alcohol dependence were examined. The influence of genes and environment on the relationship between these disorders was also examined. The study utilized a subset of FinnTwin12, a population-based twin study that consists of five consecutive birth cohorts. The subsample consisted of 1035 twin pairs (N = 2070) and of that 2070, 1854 completed the intensive interview at age 14. At age 22, 1345 twins completed the interview. Participants in the study completed age-appropriate variations of the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA). Analyses were run separately by gender. Results provide support for the significant influence of genetic factors on the development and persistence of antisocial behavior. For both males and females, model fitting indicated that genetic influences are the most influential contributor to the association between conduct disorder and adult antisocial behavior and its stability across time. Additionally, there were no age specific genetic effects suggesting that the genes influencing conduct disorder are the same as those influencing adult antisocial behavior. Results for the relationship between conduct disorder and alcohol dependence differed by gender. For females, insufficient power made it difficult for the model to discriminate between the effects of genetics and shared environment, but the full model suggested that shared environmental influences explained the greatest proportion of variance in the relationship. For males, genetic influences were primarily responsible for the relationship between conduct disorder and alcohol dependence. Similar results were found for males when the relationship between alcohol dependence and adult antisocial behavior was explored. For females, genetic and nonshared environmental influences were the primary source of covariation between these two disorders. The data suggest that the etiology of conduct disorder, adult antisocial behavior, and alcohol dependence vary by gender.

The etiological connection between internalizing and externalizing disorders is poorly understood. This manuscript aims to investigate the roles of genes and then environment in the development of Major Depressive Disorder (MDD) and Antisocial Personality Disorder (ASPD) and the nature of their comorbidity in young adults. Data from a sample of 2,291 young adult male and female twins from the Young Adult Follow Up Study (YAFU) of the Virginia Twin Study of Adolescent Behavioral Development (VTSABD) were used to estimate the proportion of variation in these traits that can be accounted for by additive genetic, shared environmental, and unique environmental factors. In addition to traditional methods of measurement of psychiatric disorders (symptom sum scores), a more novel approach to measurement through item response theory (IRT) was employed. Through both measurement methods, variation in depression was found to be influenced almost entirely by environmental factors, however IRT analysis revealed genetic influences related to specific symptoms that cannot be gleaned from a traditional univariate analysis. While the symptoms of MDD appear to work well together to define the latent construct, symptoms of ASPD are less cohesive. ASPD item loadings are more disparate and the item response models are somewhat unstable compared with the MDD item analyses. Consistent with the literature, results using traditional sum score data indicated that ASPD was influenced by additive genetic and unique environmental effects. IRT analysis, however, did indicate a role for the shared environment in ASPD variation.ASPD/MDD comorbidity analyses suggest that more than one mechanism may reasonably explain the relationship between the disorders. It appears to be more likely that common genetic factors account for some of the observed comorbidity in females than in males. Conversely, the shared environment is that the most likely link between the two disorders in males. The etiological nature of these disorders is complex and analysis may be further complicated in a population spanning a critical developmental period, such as young adulthood. The item response approach has the potential to provide new insight into how these disorders develop and differ between the sexes and different age groups.

The aim of this master thesis is to empirically validate "hypothesis of twin deficits", resulting from Mundell-Fleming model, in the Czech Republic in years 1999-2010. The econometric method used was VAR models and Impulse Response Functions based on these models. Analysis proved that as a result of government deficit increase, through exchange rate appreciation, the balance of foreign trade deteriorates. Another fact discovered is that people are partially behaving as described by Ricardo-Barro equivalence. Their reaction on increased government deficit is increase of their personal savings as well as consumption. But increase of personal savings is not sufficiently compensating the deficit in government budget. Similar results were achieved also in analysis of government spendings.

The automotive industry is constantly being challenged by customers and authorities to enhance the efficiency of the internal combustion engine (ICE) in order to achieve improved fuel consumption and reduced emissions. There are several interfaces within the design of an ICE that causes frictional losses, one of them is the valvetrain. An approach to reducing the friction in the valvetrain of modern engines is to implement cam-follower rollers, resulting in a rolling rather than sliding contact when interacting with the camshaft. The prominent type of wear in rolling contacts is surface fatigue, and specifically a phenomenon called micropitting. The company in collaboration with this project is Applied Nano Surfaces Sweden AB (ANS), located in Uppsala, Sweden. The company have specialized in surface treatment methods of mechanical components. ANS has developed a mechano-chemical treatment method called ANS Triboconditioning, which have shown beneficial friction and wear reducing properties when applied to metal surfaces. This thesis was conducted to investigate how the ANS Triboconditioning would affect the frictional behaviour compared to established surface treatment methods and the occurrence of micropitting in rolling contact configurations. Two types of test programs was implemented into a Wazau UTM 2000 Twin-Disc Tribometer. No clear trend could be established from the micropitting tests and therefore no conclusion regarding if ANS Triboconditioning affects the occurrence of micropitting damage in a positive or negative manner could be stated. The results from the friction test indicated an overall reduction in friction for the test specimens that had been treated with ANS Triboconditioning when compared to specimens that only had been treated with already established surface treatment methods. Summarized, additional tests and analyses are necessary in order to statistically confirm the observed results and determine their respective trends.

Some stars with similar properties to our sun (solar twins) have differ- ent chemical composition than the rest of the solar twins. One explanation might be planet engulfment. Therefore we did a large number of simu- lations where a disturbing star passed a sun and a planet at a distance closer than 100 AU to see how often the planet was engulfed. The result was that the planet in most cases was thrown out of the system, but it was engulfed in about 10 − 30% of the simulations when the planet was close to its star. The conclusion was that planet engulfment indeed can be a good explanation for the different chemical compositions of solar twins, at least in dense stellar clusters where such close passages should be quite common. / Vissa solliknande stja ̈rnor (s ̊a kallade soltvillingar) har en annorlunda kemisk sammansa ̈ttning ja ̈mfo ̈rt med resten av soltvillingarna. En mo ̈jlig fo ̈rklaring kan vara att dessa stja ̈rnor har slukat planeter. Da ̈rf ̈or gjorde vi ett stort antal simuleringar d ̈ar en sto ̈rande stja ̈rna passerade ett sys- tem best ̊aende av solen och en planet. Stj ̈arnan passerade p ̊a ett avst ̊and under 100 AU och vi observerade hur ofta planeten slukades. Resultatet var att planeten oftast slungades ut i rymden, men den slukades i 10-30% av simuleringarna da ̈r planeten kretsade na ̈ra sin stja ̈rna. Slutsatsen vara att planetslukning kan vara en rimlig f ̈orklaring till de annorlunda kemiska sammansa ̈ttningarna hos soltvillingar, ̊atminstone i ta ̈ta stja ̈rnhopar da ̈r na ̈ra stja ̈rnpassager bo ̈r vara ganska vanliga.

Ce projet vise à développer un nouveau procédé de fabrication de nanofibrilles de cellulose (NFC) à fort taux de matière sèche et en consommant peu d’énergie. L’extrusion bi-vis, technique industrielle, efficace énergétiquement et facilement adaptable fut ainsi utilisée pour produire des NFC à 20%. En diminuant considérablement la teneur en eau, cette nouvelle stratégie permet de diminuer le coût du transport, d’améliorer le stockage et d’élargir leur domaine d’application. Ce travail a consisté (i) à développer de nouveaux prétraitements chimiques des fibres de celluloses, respectueux de l’environnement pour faciliter la fibrillation de la cellulose et produire des NFC fonctionnelles de qualité, (ii) à optimiser les conditions d’extrusion ainsi que le profil de vis et (iii) à préparer des matériaux à partir de cette nouvelle matière. Quatre prétraitements chimiques ont été identifiés comme facilement industrialisables et ensuite optimisés. La nanofibrillation par extrusion a été ensuite simulée par un logiciel pour obtenir des conditions d’extrusion optimisées. La production de NFC de qualité à l’échelle semi-industrielle a été validée. Différentes applications ont été envisagées pour ces nouvelles NFC à fort taux de matière sèche. / This project aims at developing a new process to produce high solid content cellulose nanofibrils (CNF) decreasing the energy consumption and preserving the high quality compared to classic processes. Twin screw extrusion (TSE), industrially well-known, energy efficient and highly adaptable technique, was optimized to produce CNF at 20 wt% solid content. By decreasing considerably the water content, this new strategy improves the transport cost, the storage and widening the field of application and formulation. The objectives were to (i) develop new green pretreatments of cellulose fibers to facilitate the fibrillation and produce high quality functionalized CNF, (ii) optimize TSE screw profile and conditions to produce CNF and (iii) prepare new materials made of this new type of CNF. Four chemical pretreatments of cellulose fibers have been identified as industrially feasible, leading to high quality functionalized CNF and were widely studied and optimized. The nanofibrillation by TSE was simulated using a simulation software and TSE conditions were then successfully optimized. This cost-effective approach was validated at semi-industrial scale. Finally, different new applications with this new grade of CNF were considered.

Purpose – The purpose of this study is to enhance the understanding of how to successfully collaborate on digital platforms in the manufacturing industry by developing a contingency framework. To fulfill this purpose, the following research questions were derived: RQ1: Which challenges arise when collaborating on digital platforms in the manufacturing industry? and RQ2: How can collaboration challenges on digital platforms in the manufacturing industry be managed? Method – The study was conducted as an explorative, inductive single case study of a digital platform. More specifically, the study examined the development process of a digital twin platform created by a large high-technological company and its collaborative actors. In total, 21 interviews were conducted at eight different companies. The respondents all had experience of digital twin platforms, where some were working with digital twins sporadically and others on a daily basis. The data were analyzed through a thematic analysis. Findings – The analysis reveals that actors on digital platforms can face five types of challenges that hinder a successful collaboration: disadvantages of dependency, uncertainty regarding data management, varying customer needs, insufficient work methods, and unsuitable payment models. The analysis also reveals four strategies that can be used to address the challenges: transparency strategy, incentive model strategy, servitization strategy, and control strategy. Moreover, these findings are summarized in a contingency framework that explains which types of challenges that can be addressed with which strategies based on the specific prerequisites of each collaboration. Theoretical and practical implications – The study extends the digital platform literature by providing empirical evidence for several collaboration challenges among the actors on a digital platform, which has previously bee not been studied. Additionally, the study provides evidence of how these challenges can be addressed. Our framework helps manufacturing companies to successfully adopt digital platforms by providing managers with the tools to handle the required collaboration. Limitations and further research – The study is limited by a single case study of a specific digital platform. Thus, to extend the findings, further research that examines other contexts are recommended. Moreover, the establishment of the studied platform is currently in an early phase which limits the study to hypothetical challenges and management methods. To validate the findings, further research that examines a fully developed and implemented platform is recommended.

A principal motivação para o desenvolvimento do presente projeto de doutorado foi comparar as microestruturas e texturas resultantes da liga de alumínio 3003 obtida por lingotamento contínuo e semicontínuo. O processo “roll caster" (lingotamento contínuo em cilindros) tem sido crescentemente utilizado na indústria de laminação de alumínio. Produtos que antes sofriam altos graus de deformação durante seu processamento são hoje obtidos nas dimensões próximas da espessura final. Com o intuito de entender este processo relativamente novo, as microestruturas e as texturas (macrotextura e microtextura), ao longo da espessura, das chapas produzidas por lingotamento contínuo e por lingotamento semicontínuo (placas fundidas com 250 mm de espessura, seguido de homogeneização e laminação a quente) foram analisadas. Foi possível constatar que os materiais provenientes dos dois processos diferem bastante e que ao longo da espessura também há grandes diferenças. Foi possível observar que durante o processamento “roll caster" há considerável deformação plástica, com a formação de células de discordâncias e subgrãos. Foi possível observar, também, que a microestrutura, a morfologia e o tamanho de grão, da amostra “caster" bruta de fundição são mais homogêneos que na amostra laminada a quente. As duas chapas, a laminada a quente e a obtida por lingotamento contínuo, exibem forte gradiente de textura ao longo da espessura. A textura predominante nos dois processos, ao longo da espessura, é a do tipo latão {011}. A evolução da textura do material proveniente do processo “roll caster" também foi caracterizada após laminação e posterior recristalização, revelando a presença de componentes típicas de laminação e de recristalização de alumínio. Após laminação a frio com redução de 91% e posterior tratamento térmico de 400°C por 1 h, a chapa proveniente do processo “caster" apresentou uma textura de recristalização caracterizada pela presença da componente cubo (recristalização) somada à parcela de textura de deformação. No caso do alumínio e suas ligas, sabe-se que esta textura proporciona os melhores resultados para minimizar o efeito de orelhamento durante a estampagem. Outro ponto relevante do trabalho foi o aperfeiçoamento da técnica de extração de precipitados para a liga 3003, uma vez que, a extração de precipitados em ligas de alumínio é especialmente problemática, pois a maioria das partículas presentes dissolve-se até mais facilmente que a matriz de alumínio. Algumas técnicas foram testadas: 1. dissolução química em solução de iodo em metanol; 2. dissolução eletrolítica em solução de ácido benzóico e hidroxiquinolina em clorofórmio e metanol; 3. dissolução eletrolítica em solução de ácido perclórico, butil glicol, álcool etílico e água; 4. dissolução química em solução de fenol. A técnica que apresentou melhores resultados foi a dissolução química com fenol, onde foi possível separar os precipitados da matriz alumínio. Com o auxílio desta técnica foi possível analisar as transformações de fase do composto intermetálico Al6Mn durante tratamentos térmicos. Obtiveram-se dados da completa transformação da fase Al6Mn em alfa-AlMnSi, também conhecida na literatura como, transformação "six to alfa". A precipitação e os precipitados desempenham um papel importante na cinética de recristalização e no tamanho de grão final. Para se entender este comportamento, comparou-se uma chapa que sofreu tratamento térmico antes da laminação com outra chapa que foi laminada no estado bruto de fundição. Os resultados revelaram que a recristalização foi retardada na amostra, inicialmente, bruta de fundição. A precipitação ocorreu simultaneamente com a recristalização, com isso, os dispersóides precipitaram preferencialmente na microestrutura deformada, em subcontornos ou nas discordâncias isoladas, levando a um considerável atraso no rearranjo das discordâncias e na nucleação da recristalização. / The main reason for the development of this PhD Thesis was to compare the microstructures and textures of the 3003 aluminum alloy produced from continuous and semi-continuous casting processes. The roll caster process (continuous casting) has been increasingly used in the aluminum industry. Products usually obtained by means of heavy rolling operations in the past are nowadays obtained with dimensions close to the final ones using the roll caster technology. To understand this new process, microstructures and textures (macrotexture and microtexture) along the thickness of the sheet produced by continuos casting and semi-continuous casting (plates with 250 mm thickness, followed by homogenization and hot rolling) have been investigated. It was possible to verify that materials coming from these two processes did differ each other a lot mainly across the thickness. During roll casting the plastic deformation was large enough to promote the formation of dislocation cells and subgrains. It was also possible to notice that the microstructure, morphology, and grain size from as-cast sample are more homogenous than the ones found in hot rolled samples. Both the sheets obtained by hot rolling and continuous casting have shown a strong texture gradient across the thickness. The predominant texture in both processes is the Brass component {011} . The texture evolution from sheets obtained by roll casting was also determined after rolling and subsequent recrystallization. It shows the presence of typical components of rolling and recrystallization of aluminum. After 91% cold rolling and subsequent recrystallization at 400°C for 1 h, the cube component (recrystallization texture) and the deformation texture were observed. It is well known that this texture minimizes earing effects during deep drawing of aluminum products. Another relevant point in this work was the development of the technique for the extraction of precipitates for the aluminum 3003 alloy. The extraction of precipitates extraction is particularly problematic in aluminum because most of the particles tend to dissolve more readily than the aluminum matrix. Some of the techniques performed are the following: 1. chemical dissolution with iodine in methanol solution; 2. electrolytic dissolution with benzoic acid and hydroxyquinoline in chloroform and methanol; 3. electrolytic dissolution with perchloric acid, butyl-glycol and ethanol; 4. chemical dissolution with phenol solution. Chemical dissolution with the phenol solution was the technique that provided the best results. It was possible to separate precipitates from the aluminum matrix. With this extraction technique it was possible to analyze phase transformations of the intermetallic compound Al6Mn during heat treating of this alloy. The phase transformation of the Al6Mn compound into alfa-AlMnSi, also known as 6-to-alfa transformation, could be followed in detail by means of this technique. Precipitation plays an important role in the recrystallization kinetics and final grain size. Therefore, to understand this behavior, the roll cast aluminum alloy was cold rolled from two distinct starting conditions: as-cast and heat-treated (homogeneized) conditions. It was shown that recrystallization was delayed in the sheet rolled from the as-cast condition. Precipitation has occurred simultaneously with recrystallization, in such a manner that dispersoids did precipitate in the deformed microstructure, preferentially, at subgrain boundaries or at free dislocations. As a result, the rearrangement of the dislocations and further recrystallization nucleation has been significantly retarded.