1,720,978 research outputs found
A study of B → πℓν and Bs → Kℓν form factors using dispersive constraints
No full textThis thesis presents several approaches to improve the extrapolation of form factors for the exclusive semileptonic decays and . These decays are of interest for testing the predictions of the Standard Model. These form factors cannot be calculated perturbatively, and so we rely on techniques such as Lattice QCD (Quantum Chromodynamics) to make theoretical predictions. For these heavy-to-light decays, Lattice QCD gives form factor information in a limited region of phase space and the results must be extrapolated to cover the entire kinematically-allowed region. Model-independent approaches based on dispersion relations are now widely used. The most common is Z-fits, but recently interest has been revived in what will here be called the Dispersive matrix (DM) approach.The z-fit approach parametrizes the dispersion relations for these decays and uses lattice information to find optimal coefficients for the resulting curves. Approaches to improving the precision of this technique are explored, such as an alternative parametrization, and making use of information from multiple decays simultaneously.The Dispersive Matrix method does not require parametrizing the form factor results (and so avoids any issues with truncation of the expansion). This method finds the minimum and maximum values of the form factors allowed by unitarity using known form factor points. Modifications to the method are trialled, including using information from multiple decays simultaneously, improving numerical stability when computing the bounds, and optimising the implementation of a kinematic constraint relating the form factors.A novel method to generating form factor curves using the Dispersive matrix method is introduced, alongside several optimisations to improve computation time. This new method is tested, and the results, namely for the Cabibbo–Kobayashi–Maskawa matrix element, , are compared to those from the Z-fit approach
Form factor curves consistent with unitarity for semileptonic decays
No full textWe discuss a method to generate form factor curves consistent with dispersive constraints across the entire kinematic range for exclusive semileptonic (SL) pseudoscalar to pseudoscalar decays, for example B→πℓνB→πℓν and B_s \rightarrowK \ell \nu. The work builds on the Dispersive Matrix (DM) method which allows model-independent extrapolation to any desired q2q2value in the SL physical region using known form factor information at specific discrete q2q2 points as input. Here qq is the outgoing lepton-pair 4-momentum. An obstacle in using DM results for phenomenological predictions, such as forward-backward asymmetries,is that it is not obvious how to use the bounds over continuous ranges of q2q2 when integrating, for example, the differential decay rate over the physical q2q2 range or over bins in q2q2. We describe a method to generate a family of curves, each consistent with unitarity constraints, that can be used in the same way as aset generated from a parametrized fit (e.g. a zz-fit). This allows integration over any desired bins. We further show some techniques to increase the computational efficiency of the method. We emonstrate the application to determining ∣Vub∣∣Vub∣
Network approaches to understanding biomarker biology
Get PDF© 2017 Dr Scott Callum RitchieCommon non-communicable diseases such as cardiovascular diseases, chronic respiratory diseases, and diabetes are the leading causes of premature mortality and ill-health worldwide. These are complex diseases that take multiple decades to manifest with myriad genetic, lifestyle, and environmental risk factors. The last decade has seen rapid technological advancements and falling costs to high-throughput omic profiling platforms enabling large-scale studies into the molecular differences between healthy individuals and those that will later develop disease. Epidemiological studies of omic data in population cohorts have identified many new biomarkers of future disease risk and mortality. The end-goal of biomarker research is not only to identify individuals at increased risk of disease, but also to find ways to intervene to reduce that risk. Identification and characterisation of the biological processes these biomarkers participate in or reflect is a fundamental step in the process of clinical translation.
This thesis explores the use of network-based approaches for identification and characterisation of aberrant biological processes associated with biomarkers using population cohort multi-omic data. A scalable and efficient method for robust statistical assessment of network module preservation and reproducibility is developed: NetRep. Multi-omic data from three large population biobanks are analysed to identify and characterise biological processes associated with elevated GlycA levels; a heterogeneous NMR signal that has been of recent interest as a biomarker for long-term risk of cardiovascular disease, type II diabetes, and premature mortality. I found that elevated GlycA levels corresponded with the presence of sub-clinical inflammation and increased coordinated expression of a reproducible gene coexpression network module indicative of neutrophil activity. Accordingly, analysis of a population cohort with linked electronic health records showed that elevated GlycA levels had long-term consequences for increased risk of severe infections up to 14-years in the future. To fine-map the GlycA biomarker, I developed accurate imputation models for predicting concentrations of three of the five glycoproteins contributing to the GlycA signal from population-based serum NMR data: alpha-1-acid glycoprotein (AGP), alpha-1 antitrypsin (A1AT), and haptoglobin (HP). Imputation of these three glycoproteins in two large population cohorts with linked electronic health records revealed elevated A1AT had the most severe long-term ramifications for future disease and mortality risk over an 8-year follow-up period.
In total, this thesis shows the utility of leveraging population-based omic data for elucidating biomarker biology and provides a useful framework to guide future studies of new and established biomarkers for future disease risk
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
- …
