11 resultados para multi-dimensional systems

em Helda - Digital Repository of University of Helsinki


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Photosynthesis is a chemical process in which the energy of the light quanta is transformed into chemical energy. Chlorophyll (Chl) molecules play a key role in photosynthesis; they function in the antennae systems and in the photosynthetic reaction center where the primary charge separation (CS) takes place. Bio-inspired mimicry of the CS is an essential unit in dye-sensitized solar cells. Aim of this study was to design and develop electron donor-acceptor (EDA) pairs from Chls and fullerenes (C60) or carbon nanotubes (CNT). The supramolecular approach was chosen, as long synthetic sequences required by the covalent approach lead to long reaction schemes and low yields. Here, a π-interaction between soluble CNTs and Chl was used in EDA construction. Also, a beta-face selective two-point bound Chl-C60 EDA was introduced. In addition, the photophysical properties of the supramolecular EDA dyads were analyzed. In organic chemistry, nuclear magnetic resonance (NMR) spectroscopy is the most vital analytical technique in use. Multi-dimensional NMR experiments have enabled a structural analysis of complex natural products and proteins. However, in mixture analysis NMR is still facing difficulties. In many cases overlapping signals can t be resolved even with the help of multi-dimensional experiments. In this work, an NMR tool based on simple host-guest chemistry between analytes and macromolecules was developed. Diffusion ordered NMR spectroscopy (DOSY) measures the mobilities of compounds in an NMR sample. In a liquid state NMR sample, each of the analytes has a characteristic diffusion coefficient, which is proportional to the size of the analyte. With normal DOSY experiment, provided that the diffusion coefficients of the analytes differ enough, individual spectra of analytes can be extracted. When similar sized analytes differ chemically, an additive can be introduced into the sample. Since macromolecules in a liquid state NMR sample can be considered practically stationary, even faint supramolecular interaction can change the diffusion coefficient of the analyte sufficiently for a successful resolution in DOSY. In this thesis, polyvinylpyrrolidone and polyethyleneglycol enhanced DOSY NMR techniques, which enable mixture analysis of similar in size but chemically differing natural products, are introduced.

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In this thesis we study a series of multi-user resource-sharing problems for the Internet, which involve distribution of a common resource among participants of multi-user systems (servers or networks). We study concurrently accessible resources, which for end-users may be exclusively accessible or non-exclusively. For all kinds we suggest a separate algorithm or a modification of common reputation scheme. Every algorithm or method is studied from different perspectives: optimality of protocols, selfishness of end users, fairness of the protocol for end users. On the one hand the multifaceted analysis allows us to select the most suited protocols among a set of various available ones based on trade-offs of optima criteria. On the other hand, the future Internet predictions dictate new rules for the optimality we should take into account and new properties of the networks that cannot be neglected anymore. In this thesis we have studied new protocols for such resource-sharing problems as the backoff protocol, defense mechanisms against Denial-of-Service, fairness and confidentiality for users in overlay networks. For backoff protocol we present analysis of a general backoff scheme, where an optimization is applied to a general-view backoff function. It leads to an optimality condition for backoff protocols in both slot times and continuous time models. Additionally we present an extension for the backoff scheme in order to achieve fairness for the participants in an unfair environment, such as wireless signal strengths. Finally, for the backoff algorithm we suggest a reputation scheme that deals with misbehaving nodes. For the next problem -- denial-of-service attacks, we suggest two schemes that deal with the malicious behavior for two conditions: forged identities and unspoofed identities. For the first one we suggest a novel most-knocked-first-served algorithm, while for the latter we apply a reputation mechanism in order to restrict resource access for misbehaving nodes. Finally, we study the reputation scheme for the overlays and peer-to-peer networks, where resource is not placed on a common station, but spread across the network. The theoretical analysis suggests what behavior will be selected by the end station under such a reputation mechanism.

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This study reports a corpus-based study of medieval English herbals, which are texts conveying information on medicinal plants. Herbals belong to the medieval medical register. The study charts intertextual parallels within the medieval genre, and between herbals and other contemporary medical texts. It seeks to answer questions where and how herbal texts are linked to each other, and to other medical writing. The theoretical framework of the study draws on intertextuality and genre studies, manuscript studies, corpus linguistics, and multi-dimensional text analysis. The method combines qualitative and quantitative analyses of textual material from three historical special-language corpora of Middle and Early Modern English, one of which was compiled for the purposes of this study. The text material contains over 800,000 words of medical texts. The time span of the material is from c. 1330 to 1550. Text material is retrieved from the corpora by using plant name lists as search criteria. The raw data is filtered through qualitative analysis which produces input for the quantitative analysis, multi-dimensional scaling (MDS). In MDS, the textual space that parallel text passages form is observed, and the observations are explained by a qualitative analysis. This study concentrates on evidence of material and structural intertextuality. The analysis shows patterns of affinity between the texts of the herbal genre, and between herbals and other texts in the medical register. Herbals are most closely linked with recipe collections and regimens of health: they comprise over 95 per cent of the intertextual links between herbals and other medical writing. Links to surgical texts, or to specialised medical texts are very few. This can be explained by the history of the herbal genre: as herbals carry information on medical ingredients, herbs, they are relevant for genres that are related to pharmacological therapy. Conversely, herbals draw material from recipe collections in order to illustrate the medicinal properties of the herbs they describe. The study points out the close relationship between medical recipes and recipe-like passages in herbals (recipe paraphrases). The examples of recipe paraphrases show that they may have been perceived as indirect instruction. Keywords: medieval herbals, early English medicine, corpus linguistics, intertextuality, manuscript studies

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L Amour de loin: The semantics of the unattainable in Kaija Saariaho s opera Kaija Saariaho (born 1952) is one of the most internationally successful Finnish composers there has ever been. Her first opera L Amour de loin (Love from afar, 1999-2000) has been staged all over the world and has won a number of important prizes. The libretto written for L Amour de loin by Amin Malouf (born 1949) sets the work firmly in the culture of courtly love and the troubadours, which flourished in Occitania in the South of France during the Middle Ages. The male lead in the opera is the troubadour Jaufré Rudel, who lived in the twelfth century and is known to have taken part in the Second Crusade in 1147-1148. This doctoral thesis L Amour de loin: The semantics of the unattainable in Kaija Saariaho s opera, which comes within the field of musicology and opera research, examines the dimensions of meaning contained in Kaija Saariaho s opera L Amour de loin. This hermeneutic-semiotic study is the first doctoral thesis dealing with Saariaho to be completed at the University of Helsinki. It is also the first thesis-level study of Saariaho s opera to be completed anywhere in the world. The study focuses on the libretto and music of the opera, that is to say the dramatic text (L Amour de loin 1980), and examines on the one hand the dimensions of meaning produced by the dramatic text and on the other, the way in which they fix the dramatic text in a historical and cultural context. Thus the study helps to answer questions about the dimensions of meaning contained in the dramatic text of the opera and how they can be interpreted. The most important procedural viewpoint is Lawrence Kramer s hermeneutic window (1990), supplemented by Raymond Monelle s semiotic theory of musical topics (2000, 2006) and the philosophical concept of Emmanuel Levinas (1996, 2002) in which the latter acts as an instrument for semantic interpretation to build up an analysis. The analytical section of the study is built around the three characters in the opera, Jaufré Rudel, Clémence the Countess of Tripoli, and the Pilgrim. The study shows that the music of Saariaho, who belongs to the third generation of Finnish modernists, has become distanced from the post-serial aesthetic towards a more diatonic form of expression. There is diatonicity, for instance, in the sonorous individuality of the male lead, which is based on the actual melodies of the historical Jaufré Rudel. The use of outside material in this context is exceptional in the work of Saariaho. At the same time, Saariaho s opera contains a wealth of expressive devices she has used in her earlier work. It became apparent during the study that, as a piece of music, L Amour de loin is a many layered and multi-dimensional work that does not unambiguously represent any single stylistic trend or aesthetic. Despite the composer s post-serial background and its abrasive relationship with opera, L Amour de loin is firmly attached to the tradition of western opera. The analysis based on the theory of musical topics that was carried out in the study, shows that topics referring to death and resurrection, used in opera since the seventeenth century, appear in L Amour de loin. The troubadour topic, mainly identified with the harp, also emerges in the work. The study also shows that the work is firmly attached to the tradition of western opera in other aspects, too, such as the travesti or trouser role played by the Pilgrim, and the idea of deus ex machina derived from Ancient Greek theatre. The study shows that the concept of love based on the medieval practices of courtly love, and the associated longing for another defined by almost 1,000 years of western culture, are both manifested in the semantics of Kaija Saariaho s opera which takes its place in the contemporary music genre.

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There exists various suggestions for building a functional and a fault-tolerant large-scale quantum computer. Topological quantum computation is a more exotic suggestion, which makes use of the properties of quasiparticles manifest only in certain two-dimensional systems. These so called anyons exhibit topological degrees of freedom, which, in principle, can be used to execute quantum computation with intrinsic fault-tolerance. This feature is the main incentive to study topological quantum computation. The objective of this thesis is to provide an accessible introduction to the theory. In this thesis one has considered the theory of anyons arising in two-dimensional quantum mechanical systems, which are described by gauge theories based on so called quantum double symmetries. The quasiparticles are shown to exhibit interactions and carry quantum numbers, which are both of topological nature. Particularly, it is found that the addition of the quantum numbers is not unique, but that the fusion of the quasiparticles is described by a non-trivial fusion algebra. It is discussed how this property can be used to encode quantum information in a manner which is intrinsically protected from decoherence and how one could, in principle, perform quantum computation by braiding the quasiparticles. As an example of the presented general discussion, the particle spectrum and the fusion algebra of an anyon model based on the gauge group S_3 are explicitly derived. The fusion algebra is found to branch into multiple proper subalgebras and the simplest one of them is chosen as a model for an illustrative demonstration. The different steps of a topological quantum computation are outlined and the computational power of the model is assessed. It turns out that the chosen model is not universal for quantum computation. However, because the objective was a demonstration of the theory with explicit calculations, none of the other more complicated fusion subalgebras were considered. Studying their applicability for quantum computation could be a topic of further research.

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The Minimum Description Length (MDL) principle is a general, well-founded theoretical formalization of statistical modeling. The most important notion of MDL is the stochastic complexity, which can be interpreted as the shortest description length of a given sample of data relative to a model class. The exact definition of the stochastic complexity has gone through several evolutionary steps. The latest instantation is based on the so-called Normalized Maximum Likelihood (NML) distribution which has been shown to possess several important theoretical properties. However, the applications of this modern version of the MDL have been quite rare because of computational complexity problems, i.e., for discrete data, the definition of NML involves an exponential sum, and in the case of continuous data, a multi-dimensional integral usually infeasible to evaluate or even approximate accurately. In this doctoral dissertation, we present mathematical techniques for computing NML efficiently for some model families involving discrete data. We also show how these techniques can be used to apply MDL in two practical applications: histogram density estimation and clustering of multi-dimensional data.

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Individuality and the Community in the Development of K. E. Nipkow's Theory of Religious Education from 1960 to 1990 The purpose of this study was to describe and analyze the development occurred between 1960 and 1990 of the theory of religious education as proposed by K. E. Nipkow, the German Religious Education specialist, from the point of view of individuality and the community. Nipkow's methodological approach of dialectic convergence theory resulted in a dialogue between theological and educational factors, which supported the thirty-year development of Nipkow's models, theoretical foundations, and theory of religious education. Nipkow's doctoral dissertation, published in 1960, deals with individuality in the thinking of Pestalozzi, Humboldt and Schleiermacher. Nipkow regarded individuality as one of the basic concepts of education, which were to be interpreted anew as social and historical situations changed. In the late 1960s Nipkow developed the so-called experiential hermeneutically oriented context model for the needs of religious education. In this model, individuality is expressed in the attention paid to pupils' life situations and the educational reality. The multi-dimensional theoretical framework of religious education in 1975 emphasized supporting identity as a fundamental task of religious education. The concept of individuality was thus given a new form, in accordance with contemporary theories of developmental psychology. Other fundamental tasks, such as the socio-ethical task, the task of critical religious thinking, and that of ecumenical learning, meant a more specific emphasis on the community. It was an outline of a liberating education, which faced the individualistic-existential and social-ecclesiastical challenges of the time with a critical attitude. The further development of the theoretical outline in 1982 continued to uphold the perspectives of both individuality and the community, as Nipkow combined a historical-social dimension with theories of developmental psychology, especially that of life-span research. According to him, the development of the individual and communal life-reality belonged together. The fundamental task of religious education came to be learning to live and believe together. Nipkow transferred the idea of dialogue into inter-generational learning and developed elementarization as a methodology of Religious Education, which takes into account the point of departure of each age group. His theory of educational responsibility in the church (1990) contained the tasks of walking alongside the individual and the renewal of church communities as prerequisites of communicating the Christian faith in an era characterized by multifaceted Christianity. The "geisteswissenschaftliche" school and its concepts (Ger. Individualität; Bildung) were found to be the explanatory factor of the concepts of individuality and the community in the development of Nipkow's theory of religious education. The concept of education employed by Nipkow (Ger. Bildung) implies, on one hand, the individuality, autonomy, freedom and personal responsibility of people of different ages, and on the other hand, the dialogical nature of education in the community facilitated by this concept. Theologically, Nipkow associates himself in his views on individuality and the community with Schleiermacher's understanding of faith, of which openness towards the world was characteristic. The significance of individuality and the community in Nipkow's thinking was, furthermore, deepened by his participation, as a member of working parties, in the educational discussions of the World Council of Churches.

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The study Slogans of Change. Three Outlooks on Finnish Television Contents is concerned with alleged changes of television contents during the 1990s and 2000s, such as dumbing down, tabloidisation, entertainisation , and the like. Specifically, the focus is on the ways these changes might manifest in Finnish television. The aim of the study has been threefold: 1. To operationalise public and academic discussions about changes via specific slogans emerging from the debates; 2. Consequently, to study the slogans empirically and reflect on the findings with earlier research, including studies on institutional and audience-related aspects; 3. Finally, to suggest what the findings might mean regarding discussions about television s role, and what kinds of slogans or concepts might best serve future discussions and research. The empirical outlooks presented in this study offer analyses with three different sets of opposing slogans of change. The outlooks also follow three different traditions of the study of television. The first outlook focuses on quantity, as it gives a longitudinal (1993-2004), macro-level view on programme structures. The methodological approach is derived from media economic and policy studies. The claims that frame the analysis are convergence versus diversification of programme structures. The second outlook provides quantitative and qualitative views on the characteristics and quality  the term signifying essence as well as worth  of Finnish television journalism during sample weeks from the years 2002 and 2003. This outlook follows the traditions of quantitative content analysis found in journalism studies coupled with descriptive qualitative content analyses. The slogans reflected in this section are the lightening or widening of journalism. The third outlook narrows down the material and focuses at a micro-level on form; that is, communicative conventions in a small array of selected programmes in 1993, 2000 and during 2002-2004. The analyses have been inspired by the method of conversation analysis of verbal interaction, and coupled with qualitative close readings, with the focus of different communicative situations in the programmes. The catchphrases employed in this part are emotainment versus democratainment, coupled with more specific claims of discursive hybridisation and conversationalisation. The findings depict that, empirically, changes in Finnish television contents are not clear linear trends and cannot easily be moulded into neat slogans. The quantitative outlook on programme output during 1993-2004 depicts a tendency towards differentiation of channels, paving the way for the multi-channel digital system. The change in programme structures, however, is not dramatic on the level of total output. The second outlook suggests that the dualistic concepts, such as the pair information-entertainment, are not sufficient in understanding the array and changes of programmes that could be called journalism. The outlook on communicative conventions highlights hybridisation in the manner of television talk and its relation to broader debates on contents. Despite the three dissimilar empirical approaches, unifying aspects emerge. The outlooks suggest, albeit in different ways, tendencies toward distinction and polarisation. This study proposes that in order to facilitate a more nuanced understanding of the changes in television contents, dualistic slogans should be replaced with a multi-dimensional understanding of the concept of diversity.

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Regeneration ecology, diversity of native woody species and its potential for landscape restoration was studied in the remnant natural forest at the College of Forestry and Natural Resources at Wondo Genet, Ethiopia. The type of forest is Afromontane rainforest , with many valuable tree species like Aningeria adolfi-friederici, and it is an important provider of ecological, social and economical services for the population that lives in this area. The study contains two parts, natural regeneration studies (at the natural forest) and interviews with farmers in the nearby village of the remnant patch. The objective of the first part was to investigate the floristic composition, densitiy and regeneration profiles of native woody species in the forest, paying special attention to woody species that are considered the most relevant (socio-economic). The second part provided information on woody species preferred by the farmers and on multiple uses of the adjacent natural forest, it also provided information and analysed perceptions on forest degradation. Systematic plot sampling was used in the forest inventory. Twenty square plots of 20 x 20 m were assessed, with 38 identified woody species (the total number of species was 45), representing 26 families. Of these species 61% were trees, 13% shrubs, 11% lianas and 16% species that could have both life forms. An analysis of natural regeneration of five important tree species in the natural forest showed that Aningeria adolfi-friederici had the best regeneration results. An analysis of population structure (as determined by height classes) of two commercially important woody species in the forest, Aningeria adolfi-friederici and Podocarpus falcatus, showed a marked difference: Aningeria had a typical “reversed J” frequency distribution, while Podocarpus showed very low values in all height classes. Multi dimensional scaling (MDS) was used to map the sample plots according to their similarity in species composition, using the Sørensen quantitative index, coupled with indicator species analysis .Three groups were identified with respective indicator species: Group 1 – Adhatoda schimperiana, Group 2 – Olea hochstetteri , Group 3 – Acacia senegal and Aningeria adolfi-friederici. Thirty questionnaire interviews were conducted with farmers in the village of Gotu Onoma that use the nearby remant forest patch. Their tree preferences were exotic species such as Eucalyptus globulus for construction and fuelwood and Grevillea robusta for shade and fertility. Considering forest land degradation farmers were aware of the problem and suggested that the governmental institutions address the problem by planting more Eucalyptus globulus. The natural forest seemed to have moderate levels of disturbance and it was still floristically diverse. However, the low rate of natural regeneration of Podocarpus falcatus suggested that this species is threatened and must be a priority in conservation actions. Plantations and agroforestry seem to be possible solutions for rehabilitation of the surrounding degraded lands, thereby decreasing the existent pressure in the remnant natural forest.

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In this thesis I examine one commonly used class of methods for the analytic approximation of cellular automata, the so-called local cluster approximations. This class subsumes the well known mean-field and pair approximations, as well as higher order generalizations of these. While a straightforward method known as Bayesian extension exists for constructing cluster approximations of arbitrary order on one-dimensional lattices (and certain other cases), for higher-dimensional systems the construction of approximations beyond the pair level becomes more complicated due to the presence of loops. In this thesis I describe the one-dimensional construction as well as a number of approximations suggested for higher-dimensional lattices, comparing them against a number of consistency criteria that such approximations could be expected to satisfy. I also outline a general variational principle for constructing consistent cluster approximations of arbitrary order with minimal bias, and show that the one-dimensional construction indeed satisfies this principle. Finally, I apply this variational principle to derive a novel consistent expression for symmetric three cell cluster frequencies as estimated from pair frequencies, and use this expression to construct a quantitatively improved pair approximation of the well-known lattice contact process on a hexagonal lattice.

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According to the literature and statistical figures, professional drivers constitute a high-risk group in traffic and should be investigated in connection with the factors related to safe driving. However, safety-related behaviours and outcomes among professional drivers have attracted very little attention from safety researchers. In addition, comparing different professional and non-professional driver groups in terms of critical on-the-road characteristics and outcomes has been indicated in the literature as being necessary for a more comprehensive understanding of driver groups and the nature of driving itself. The aim of the present study was to investigate professional driving from a safety climate stand point in relation to predominant driving-related factors and by considering the differences between driver groups. Hence, four Sub-studies were conducted according to a framework emphasizing the relationships between safety climate, driver groups, driver stress, human factors (i.e., driver behaviour and performance) and accidents. Demographic information, as well as data for driver behaviour, performance, and driver stress was collected by questionnaire. The data was analysed using factor analysis, analysis of covariance as well as hierarchical and logistic regression analysis. The results revealed multi-dimensional factor structures for the safety climate measures. Considering the relationships between variables, differences were evidenced regarding on-the-road stress reactions, risky driver behaviours and penalties, between the various professional and non-professional driver groups. Driver stress was found to be related to accidents. The results also indicated that the safety climate has positive relationships with both driver behaviour and performance, and as well as involvement in accidents. The present study has a number of critical implications resulting from the fact that the way in which the effects of safety climate on professional driving were investigated, as well as the differences between professional and non-professional driver groups, was unique. Additionally, for the first time, a safety climate scale was developed specifically for professional drivers. According to the results of the study and to previous literature, a tentative model was proposed representing a possible route for the relationships between safety climate, human factors, driver stress, driver groups and accidents, by emphasizing the effects of safety climate.