Computer simulation of H and He effects in fusion reactor materials

Fusion power is an appealing source of clean and abundant energy. The radiation resistance of reactor materials is one of the greatest obstacles on the path towards commercial fusion power. These materials are subject to a harsh radiation environment, and cannot fail mechanically or contaminate the fusion plasma. Moreover, for a power plant to be economically viable, the reactor materials must withstand long operation times, with little maintenance. The fusion reactor materials will contain hydrogen and helium, due to deposition from the plasma and nuclear reactions because of energetic neutron irradiation. The first wall divertor materials, carbon and tungsten in existing and planned test reactors, will be subject to intense bombardment of low energy deuterium and helium, which erodes and modifies the surface. All reactor materials, including the structural steel, will suffer irradiation of high energy neutrons, causing displacement cascade damage. Molecular dynamics simulation is a valuable tool for studying irradiation phenomena, such as surface bombardment and the onset of primary damage due to displacement cascades. The governing mechanisms are on the atomic level, and hence not easily studied experimentally. In order to model materials, interatomic potentials are needed to describe the interaction between the atoms. In this thesis, new interatomic potentials were developed for the tungsten-carbon-hydrogen system and for iron-helium and chromium-helium. Thus, the study of previously inaccessible systems was made possible, in particular the effect of H and He on radiation damage. The potentials were based on experimental and ab initio data from the literature, as well as density-functional theory calculations performed in this work. As a model for ferritic steel, iron-chromium with 10% Cr was studied. The difference between Fe and FeCr was shown to be negligible for threshold displacement energies. The properties of small He and He-vacancy clusters in Fe and FeCr were also investigated. The clusters were found to be more mobile and dissociate more rapidly than previously assumed, and the effect of Cr was small. The primary damage formed by displacement cascades was found to be heavily influenced by the presence of He, both in FeCr and W. Many important issues with fusion reactor materials remain poorly understood, and will require a huge effort by the international community. The development of potential models for new materials and the simulations performed in this thesis reveal many interesting features, but also serve as a platform for further studies.

Exploring primary school sex education in Greece : policies and praxis

This study examines how sex education is currently developed and implemented in Greek primary schools. The four publications that comprise it explore the following themes: (1) the position and visibility of sex education as one of the topics for health education programme development; (2) the inhibiting and enhancing factors in the development and implementation of primary school sex education programmes; (3) how issues of sex, sexuality, the human body and romantic relationships are visually and textually represented in primary school textbooks; (4) the impact of sex education on teachers and pupils; and (5) teachers experiences as practitioners who deal with sexuality- related issues at school. -- The research was based on conducting multiple sub-studies using a mixed-methods approach. Specifically, qualitative and quantitative data were collected and analysed. The initial quantitative data that had been obtained by questionnaire was followed by the collection and analysis of qualitative data. The qualitative data were acquired by way of examining one particular case, various texts, interviews with teachers and self-reflective material. The results of the sub-studies are presented in a more detailed manner in the study s four publications. -- In general, the sub-studies found that sex education as an educational activity occupies a marginal place within the instructional practices of Greek primary school teachers, since the subject is hardly mentioned in classroom material, such as textbooks. However, engaging in the provision of sex education programmes can become a meaningful and rewarding experience for many teachers as well as pupils and their families. Further, teachers classroom experiences pointed to school settings as sexualized environments. These contextual factors and conditions nevertheless affected teachers practices and perceptions on a personal and professional level.Health indicators in Greece provide a picture of a population that faces various sexual health related problems. However, as many studies (including this work) indicate, sex education programmes that meet specific standards can have a positive impact on students overall health and well-being. Sex education teaching has always been a controversial issue. Its successful implementation in Greece demands knowledgeable educators and responsible policy-makers. The findings of this study suggest that the content of Greek primary school textbooks needs to be revised in order to include texts and pictures that deal with the human body and human sexuality, encourage pupils to become involved in designing the content and methods of programmes and give teachers the opportunity to reflect on and discuss their experiences. Keywords: sex education, primary school, Greece

Origins of the sex differences in handedness and mental rotation ability : genetic, environmental and hormonal effects

In humans, well-replicated and robust sex differences in cognitive functions exist for handedness and mental rotation ability. A common characteristic in human cognitive functions is the lateralization of language functions. Handedness is a common measure of laterality and is related to language lateralization. The prevalence of left-handedness is higher in males than in females, the male to female ratio being about 1.2. Among cognitive abilities, the largest sex difference is evident in the Vandenberg and Kuse Mental Rotation Test (MRT), which requires the ability to rotate objects in mental space. On average, males achieve scores one standard deviation higher than females in the MRT. The present thesis investigated the origins of the sex differences in laterality and spatial ability as represented by handedness and mental rotation ability, respectively. Two population-based Finnish twin cohorts were utilized in this study. Handedness was studied in 25 810 twins and 4068 singletons born before 1958 from the Older Finnish Twin Cohort, and in 4736 twins born in 1983-87 from the FinnTwin12. MRT was studied in a sub-sample of 804 young adult participants from the FinnTwin12 sample. The main findings of this study were: 1) the prevalence of left-handedness was higher among males than among females in both singletons and in twins; 2) males had significantly higher scores than females in MRT; 3) about one quarter of the variance in handedness and about half of the variance in MRT was explained by genetic effects, whereas the remainder of the variance in these traits was explained by environmental effects unique to each individual. The magnitude of the genetic effects was similar in both sexes; 4) left-handedness was significantly less common in female co-twins of a male than in female co-twins of a female, and female co-twins of a male scored significantly higher than did female co-twins of a female in the Mental Rotation Test. This dissertation discusses whether these differences between females from opposite- and same-sex twin pairs are due to the prenatal transfer of testosterone from the male fetus in females with male co-twins or whether they arise from postnatal socialization effects.

Sex steroids in Sjögren's syndrome

Sjögren s syndrome (SS) is a strongly female dominant autoimmune disease. SS targets mainly salivary and lacrimal glands and leads to loss of the secreting acinar cells of these glands. Accordingly, secretion of the affected glands is diminished and the main symptoms of SS, dryness of mouth and eyes, follow. In addition to these sicca symptoms, SS patients suffer from severe fatigue and can have various extraglandular symptoms. To date, the etiology of SS still remains unknown. Female dominance and the late onset of the disease simultaneously with remarkable hormonal changes in the body (menopause, adrenopause) encouraged us to hypothesize that sex steroids, especially androgens, are involved in the onset and progression of SS. We confirmed our hypothesis and showed that patients with SS suffer from androgen depletion both systemically and locally in the target tissue of SS, salivary glands. We especially focused on the local androgen environment in salivary glands and demonstrated that healthy salivary glands contain a complete enzymatic machinery for local synthesis of androgens and estrogens from pro-hormone dehydroepiandrosterone (DHEA). However, in SS salivary glands the enzymes catalyzing the local androgen synthesis are defective and, in a subgroup of patients, practically non-functional. Probably due to this local defect in DHEA processing, therapy with DHEA was found unbeneficial for SS patients in the treatment of fatigue. We also studied the effect of the local androgen depletion on salivary glands. We found that in salivary gland cells and healthy labial salivary glands androgens upregulate integrin subunits α1 and α2, which are important for the communication, differentiation and function of the acinar cells. On the contrary, in SS salivary glands DHEA failed to upregulate these signaling molecules, again probably due to defective processing of DHEA into active androgens. Our finding highlights the importance of the local androgen environment and local DHEA processing for the function and welfare of salivary glands. In conclusion, this study showed that patients with SS are androgen depleted both systemically and locally in salivary glands. SS patients also have a defective local sex steroid synthesizing enzymatic machinery further impairing the local androgen depletion. We also showed that the local androgen defect leads to decreased expression of acinar cell specific integrin molecules, which impairs the signaling between the acinar cells and basement membrane and might thus explain the acinar cell loss seen in SS salivary glands. By showing the importance of the local sex steroid imbalance in SS we have clarified some etiopathogenetic mechanisms of SS, which have thus far remained unknown.

ISO 13567 - The Proposed International Standard for Structuring Layers in Computer Aided Building Design

Layering is a widely used method for structuring data in CAD-models. During the last few years national standardisation organisations, professional associations, user groups for particular CAD-systems, individual companies etc. have issued numerous standards and guidelines for the naming and structuring of layers in building design. In order to increase the integration of CAD data in the industry as a whole ISO recently decided to define an international standard for layer usage. The resulting standard proposal, ISO 13567, is a rather complex framework standard which strives to be more of a union than the least common denominator of the capabilities of existing guidelines. A number of principles have been followed in the design of the proposal. The first one is the separation of the conceptual organisation of information (semantics) from the way this information is coded (syntax). The second one is orthogonality - the fact that many ways of classifying information are independent of each other and can be applied in combinations. The third overriding principle is the reuse of existing national or international standards whenever appropriate. The fourth principle allows users to apply well-defined subsets of the overall superset of possible layernames. This article describes the semantic organisation of the standard proposal as well as its default syntax. Important information categories deal with the party responsible for the information, the type of building element shown, whether a layer contains the direct graphical description of a building part or additional information needed in an output drawing etc. Non-mandatory information categories facilitate the structuring of information in rebuilding projects, use of layers for spatial grouping in large multi-storey projects, and storing multiple representations intended for different drawing scales in the same model. Pilot testing of ISO 13567 is currently being carried out in a number of countries which have been involved in the definition of the standard. In the article two implementations, which have been carried out independently in Sweden and Finland, are described. The article concludes with a discussion of the benefits and possible drawbacks of the standard. Incremental development within the industry, (where ”best practice” can become ”common practice” via a standard such as ISO 13567), is contrasted with the more idealistic scenario of building product models. The relationship between CAD-layering, document management product modelling and building element classification is also discussed.

The RATAS-project, in the Light of 25 Years of Development Towards Computer-Integrated Construction

In smaller countries where the key players in construction IT development tend to know each other personally and where public R&D funding is concentrated to a few channels, IT roadmaps and strategies would seem to have a better chance of influencing development than in the bigger industrial countries. In this paper Finland and the RATAS-project is presented as a historical case illustrating such impact. RATAS was initiated as a construction IT roadmap project in 1985, involving many of the key organisations and companies active in construction sector development. Several of the individuals who took an active part in the project have played an important role in later developments both in Finland and on the international scene. The central result of RATAS was the identification of what is nowadays called Building Information Modelling (BIM) technology as the central issue in getting IT into efficient use in the construction sector. BIM, which earlier was referred to as building product modelling, has been a key ingredient in many roadmaps since and the subject of international standardisation efforts such as STEP and IAI/IFCs. The RATAS project can in hindsight be seen as a forerunner with an impact which also transcended national borders.

The Organisation of Policy Meets the Commercialisation of Sex - Global Linkages, Policies, Technologies

During recent years the commercialisation of sex has increased and intensified both locally and globally. This thesis explores the commercialisation of bodies, sex and sexualities, particularly the sex trade, and the impact of rapidly evolving information and communication technologies on this globalising trade. The main focus of this work is on the policies, discourses and policy developments in the area especially in the Finnish context. The study is based on multidisciplinary theoretical sources through which the framework of multiple linkages relevant to the commercialisation of sex is conceptualised. The sex trade functions through a web of intersecting linkages of a substantive, economic, organisational, temporal, spatial, cultural, technological, as well as of legislative and policy nature. This framework of linkages forms the basis for the analysis of the main empirical data, namely qualitative interviews with thirty key managers and professionals, who are responsible for the preparation and implementation of policies on commercial sex. In addition, the thesis addresses the policies and policy practices on the sex trade through the analysis of national and international policy instruments. In addition to analysing the processes of the commercialisation of sex and its effects, the study also discusses their further implications for organisational policy-making, research, and society more generally. The thesis thus seeks to contribute to practice, research and theory on gender, management and organisations.

Computer simulation of multi-elemental fusion reactor materials

Thermonuclear fusion is a sustainable energy solution, in which energy is produced using similar processes as in the sun. In this technology hydrogen isotopes are fused to gain energy and consequently to produce electricity. In a fusion reactor hydrogen isotopes are confined by magnetic fields as ionized gas, the plasma. Since the core plasma is millions of degrees hot, there are special needs for the plasma-facing materials. Moreover, in the plasma the fusion of hydrogen isotopes leads to the production of high energetic neutrons which sets demanding abilities for the structural materials of the reactor. This thesis investigates the irradiation response of materials to be used in future fusion reactors. Interactions of the plasma with the reactor wall leads to the removal of surface atoms, migration of them, and formation of co-deposited layers such as tungsten carbide. Sputtering of tungsten carbide and deuterium trapping in tungsten carbide was investigated in this thesis. As the second topic the primary interaction of the neutrons in the structural material steel was examined. As model materials for steel iron chromium and iron nickel were used. This study was performed theoretically by the means of computer simulations on the atomic level. In contrast to previous studies in the field, in which simulations were limited to pure elements, in this work more complex materials were used, i.e. they were multi-elemental including two or more atom species. The results of this thesis are in the microscale. One of the results is a catalogue of atom species, which were removed from tungsten carbide by the plasma. Another result is e.g. the atomic distributions of defects in iron chromium caused by the energetic neutrons. These microscopic results are used in data bases for multiscale modelling of fusion reactor materials, which has the aim to explain the macroscopic degradation in the materials. This thesis is therefore a relevant contribution to investigate the connection of microscopic and macroscopic radiation effects, which is one objective in fusion reactor materials research.