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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Naturalizovaná metodologie v antropologickém výzkumu / Naturalized Methodology in Anthropological Research

Drcmánková, Karolína January 2018 (has links)
Title: Naturalized Methodology in Anthropological Research Author: Karolína Drcmánková Department: Ethnology Supervisor: doc. František Vrhel. CSc. Abstract: This paper focuses on critique of the interpretative methodology of social sciences from the position of modern philosophy of science. Our goal is to process the theoretical approaches which are discussed in the scope of philosophy of science in an interdisciplinary way. This particularly includes the arguments against epistemic relativism and postmodern theoretical approaches in anthropology. Our work is based mostly on Quin's conception of naturalised epistemology which points out the importance of applying methods commonly used in natural science. Beside this our paper is also based on Darwin's social theory and Alex Rosenberg's concept of methodological holism. Our aim is to naturalize methodology of anthropological research which will be aligned with methodology of natural science and Quin's naturalism. The conception of naturalized anthropology is based on causal explanation of human behaviour, research of standards and regularities in humans and generalization. Naturalized methodology of anthropological research will enable us to clarify the nature of human behaviour by using the methods of natural science. Keywords: naturalism,...
72

Machine learning methods for cancer immunology

Chlon, Leon January 2017 (has links)
Tumours are highly heterogeneous collections of tissues characterised by a repertoire of heavily mutated and rapidly proliferating cells. Evading immune destruction is a fundamental hallmark of cancer, and elucidating the contextual basis of tumour-infiltrating leukocytes is pivotal for improving immunotherapy initiatives. However, progress in this domain is hindered by an incomplete characterisation of the regulatory mechanisms involved in cancer immunity. Addressing this challenge, this thesis is formulated around a fundamental line of inquiry: how do we quantitatively describe the immune system with respect to tumour heterogeneity? Describing the molecular interactions between cancer cells and the immune system is a fundamental goal of cancer immunology. The first part of this thesis describes a three-stage association study to address this challenge in pancreatic ductal adenocarcinoma (PDAC). Firstly, network-based approaches are used to characterise PDAC on the basis of transcription factor regulators of an oncogenic KRAS signature. Next, gene expression tools are used to resolve the leukocyte subset mixing proportions, stromal contamination, immune checkpoint expression and immune pathway dysregulation from the data. Finally, partial correlations are used to characterise immune features in terms of KRAS master regulator activity. The results are compared across two independent cohorts for consistency. Moving beyond associations, the second part of the dissertation introduces a causal modelling approach to infer directed interactions between signaling pathway activity and immune agency. This is achieved by anchoring the analysis on somatic genomic changes. In particular, copy number profiles, transcriptomic data, image data and a protein-protein interaction network are integrated using graphical modelling approaches to infer directed relationships. Generated models are compared between independent cohorts and orthogonal datasets to evaluate consistency. Finally, proposed mechanisms are cross-referenced against literature examples to test for legitimacy. In summary, this dissertation provides methodological contributions, at the levels of associative and causal inference, for inferring the contextual basis for tumour-specific immune agency.
73

Teoria de perturbação causal para a eletrodinamica quantica em (2+1) dimensões /

Tomazelli, J. L., (Jeferson de Lima) January 1996 (has links)
Orientador: Bruto Max Pimentel Escobar. / Banca: Paulo Leal Ferreira / Banca: Francisco Caruso Neto / Banca: Walter Felipe Wreszinski / Banca: José Abdalla Helayël Neto / Doutor
74

Causality, conjugate points and singularity theorems in space-time.

January 2009 (has links)
Tong, Pun Wai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 77-78). / Abstract also in Chinese. / Chapter 1 --- Introduction --- p.6 / Chapter 2 --- Basic Terminologies --- p.8 / Chapter 3 --- Causality in space-time --- p.12 / Chapter 3.1 --- Preliminaries in space-time --- p.12 / Chapter 3.2 --- Global causality condition --- p.14 / Chapter 3.3 --- Domains of Dependence --- p.23 / Chapter 4 --- Conjugate Points --- p.29 / Chapter 4.1 --- Space of causal curves --- p.29 / Chapter 4.2 --- "Jacobi field, conjugate point and length of geodesic" --- p.35 / Chapter 4.3 --- Congruence of causal geodesics --- p.47 / Chapter 5 --- Singularity Theorems --- p.57 / Chapter 5.1 --- Definition of singularities in space-time --- p.57 / Chapter 5.2 --- A singularity theorem of R. Penrose --- p.60 / Chapter 5.3 --- A singularity theorem of S.W. Hawking and R. Penrose --- p.64 / Appendix --- p.73 / Bibliography --- p.77
75

Optical fibers with periodic structures

Haakestad, Magnus W. January 2006 (has links)
<p>This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated.</p><p>The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied.</p><p>In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated.</p><p>The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.</p>
76

On the Predictive Power of Layoffs and Vacancies : Can Advanced Notices of Dismissal and Vacancies Help Predict Unemployment?<em> A Study of the Swedish Labor Market Between 1988 and 2010</em>

Hagen, Johannes January 2010 (has links)
<p>The purpose of this paper is to investigate the predictive power of the variables advanced notice of dismissal (layoffs) and vacancies for the unemployment rate. Based on the Box Jenkins Methodology, the paper makes use of Granger causality and out-of-sample tests to compare the forecast performance of a naïve reference model and the two models extended to include either lagged values of layoffs or vacancies. It is shown that layoffs make up a significant leading variable, exhibiting particularly strong predictive power at forecast horizons of 2-6 months. It is also shown that the predictive power of vacancies is more ambiguous. Vacancies constitute a valuable explanatory variable for the unemployment rate, but does not possess the same leading, predictive qualities as layoffs.</p>
77

Expert Systems: Where Are We? And Where Do We Go from Here?

Davis, Randall 01 June 1982 (has links)
Work on Expert Systems has received extensive attention recently, prompting growing interest in a range of environments. Much has been made of the basic concept and the rule-based system approach typically used to construct the programs. Perhaps this is a good time then to review what we know, assess the current prospects, and suggest directions appropriate for the next steps of basic research. I'd like to do that today and propose to do it by taking you on a journey of sorts, a metaphorical trip through the State of the Art of Expert Systems. We'll wander about the landscape, ranging from the familiar territory of the Land of Accepted Wisdom, to the vast unknowns at the Frontiers of Knowledge. I guarantee we'll all return safely, so come along...
78

Essays on the export performance and provincial growth of China / Ran Sha

Sha, Ran January 2007 (has links)
Thesis (Ph.D. (Economics))--North-West University, Potchefstroom Campus, 2007.
79

Essays on nonlinear time series modelling och hypothesis testing

Strikholm, Birgit January 2004 (has links)
There seems to be a common understanding nowadays that the economy is nonlinear. Economic theory suggests features that can not be incorporated into linear frameworks, and over the decades a solid body of empirical evidence of nonlinearities in economic time series has been gathered. This thesis consists of four essays that have to do with various forms of nonlinear statistical inference. In the first chapter the problem of determining the number regimes in a threshold autoregressive (TAR) model is considered. Typically, the number of regimes (or thresholds) is assumed unknown and has to be determined from the data. The solution provided in the chapter first uses the smooth transition autoregressive (STAR) model with a fixed and rapid transition to approximate the TAR model. The number of thresholds is then determined using sequential misspecification tests developed for the STAR model.  The main characteristic of the proposed method is that only standard statistical inference is used, as opposed to non-standard inference or computation intensive bootstrap-based methods. In the second chapter a similar idea is employed and the structural break model is approximated with a smoothly time-varying autoregressive model. By making the smooth changes in parameters rapid, the model is able to closely approximate the corresponding model with breaks in the parameter structure. This approximation makes the misspecification tests developed for the STR modelling framework available and they can be used for sequentially determining the number of breaks. Again, the method is computationally simple as all tests rely on standard statistical inference. There exists literature suggesting that business cycle fluctuations affect the pattern of seasonality in macroeconomic series. A question asked in the third chapter is whether other factors such as changes in institutions or technological change may have this effect as well. The time-varying smooth transition autoregressive (TV- STAR) models that can incorporate both types of change are used to model the (possible) changes in seasonal patterns and shed light on the hypothesis that institutional and technological changes (proxied by time) may have a stronger effect on seasonal patterns than business cycle. The TV-STAR testing framework is applied to nine quarterly industrial production series from the G7 countries, Finland and Sweden. These series display strong seasonal patterns and also contain the business cycle fluctuations. The empirical results of the chapter suggest that seasonal patterns in these series have been changing over time and, furthermore, that the business cycle fluctuations do not seem to be the main cause for this change. The last chapter of the thesis considers the possibility of testing for Granger causality in bivariate nonlinear systems when the exact form of the nonlinear relationship between variables is not known. The idea is to linearize the testing problem by approximating the nonlinear system by its Taylor expansion. The expansion is linear in parameters and one gets round the difficulty caused by the unknown functional form of the relationship under investigation. / <p>Diss. Stockholm : Handelshögskolan, 2004</p>
80

Optical fibers with periodic structures

Haakestad, Magnus W. January 2006 (has links)
This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated. The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied. In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated. The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.

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