962,616 research outputs found

    Predicting IELTS ratings using vocabulary measures

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    This thesis addresses the relationship between vocabulary measures and IELTS ratings. The research questions focus on the relationship between measures of lexical richness and teacher ratings. The specific question the thesis seeks to address is: Which measures of lexical richness are the best for predicting the ratings? This question has been considered central in vocabulary measurement research for the last decades particularly in relation to IELTS, one of the most popular exams in the world. Therefore, if a model can predict IELTS scores by using vocabulary measures it could be used as a predictive tool by teachers and researchers worldwide. The research was carried out through two studies, Study 1 and Study 2 and then the model was tested through a third smaller study. Study 1 was a small pilot study which looked at both oral and written data. Study 2 focused on written data only. Measures of both lexical diversity and sophistication were chosen for both studies. Both studies followed similar methodologies with the addition of an extra variable in the second study. For the first study data was collected from 42 IELTS learners whereas for the second study an existing corpus was used. The measures investigated in both studies were: Tokens, TTR, D, Guiraud, Types, Guiraud Advanced and P_Lex. The first four are measures of lexical diversity, the other three measures of lexical sophistication. However, all of the previous measures are measures of breadth of vocabulary. For the second study, a measure of formulaic count was added. This is an aspect of depth of vocabulary used to check if results would improve with this addition. Formulaic sequences were counted in each essay by using Martinez and Schmitt’s (2012) PHRASE List of the 505 most frequent non-transparent multiword expressions in English. The main findings show that all the measures correlate with the ratings but Tokens has the highest correlation of all lexical diversity measures, and Types has the highest correlation of all lexical sophistication measures. TTR, Guiraud and P_Lex can explain 52.8% of the variability in the Lexical ratings. In addition, holistic ratings can be predicted by the same two lexical diversity measures (TTR and Guiraud) but with a different measure of lexical sophistication, Guiraud Advanced. The model consisting of these three measures can explain 49.2% of the variability in the holistic ratings. The formulaic count did not seem to improve the model’s predictive validity, but further analysis from a qualitative angle seemed to explain this behaviour. In Study 3, the holistic ratings model was tested using a small sample of real IELTS data and the examiners comments’ were used for a more qualitative analysis. This revealed that the model underestimated the scores since the range of ratings from the IELTS data was wider than the range of the data from Study 2 which were used as the basis for the model. This proved to be a major hindrance to the study. However, the qualitative analysis confirmed the argument that vocabulary accounts for a high percentage of variance in ratings and provided insights to other aspects that may influence raters which could be added to the model in future research. The issues and limitations of the study and the current findings contribute to the field by stimulating further research into producing a predictive tool that could inform students of their predicted rating before they decide to take the IELTS exam. This could have potential financial benefits for students

    Is There Anything to the Authority Thesis?

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    Many philosophical theories of self-knowledge can be understood as attempts to explain why self-ascriptions enjoy a certain kind of authority that other-ascriptions lack (the Authority Thesis). The aim of this paper is not to expand the stock of existing explanations but to ask whether the Authority Thesis can be adequately specified. To this end, I identify three requirements that must be met by any satisfactory specification. I conclude that the search for an adequate specification of the Authority Thesis leads to a dilemma: it either yields an interpretation under which the thesis is philosophically interesting but false, or it produces an interpretation under which the thesis is actually true but of minor philosophical interest

    Deformations of zero-dimensional schemes and applications

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    In this thesis we consider the geometry of the Hilbert scheme of points in P^n, concentrating on the locus of points corresponding to the Gorenstein subschemes of P^n. New results are given, most importantly we provide tools for constructing flat families and analysis of finite Gorenstein algebras and expose their efficiency by proving smoothability of certain families of algebras. Much of the existing theory and folklore is reviewed, providing a micro-encyclopaedic reference.Comment: v2: some minor corrections made. 29 pages. This is an MSc thesis done on the University of Warsaw; my adviser is Jaros{\l}aw Buczy\'nsk

    Slices, slabs, and sections of the unit hypercube

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    Using combinatorial methods, we derive several formulas for the volume of convex bodies obtained by intersecting a unit hypercube with a halfspace, or with a hyperplane of codimension 1, or with a flat defined by two parallel hyperplanes. We also describe some of the history of these problems, dating to Polya's Ph.D. thesis, and we discuss several applications of these formulas.Comment: 11 pages; minor corrections to reference

    Understanding the patient experience of stiffness, and developing a stiffness patient-recorded outcome measure in rheumatoid arthritis

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    Rheumatoid arthritis (RA) is a chronic, systemic, inflammatory disease. Stiffness is a major symptom of RA which is commonly reported by patients, affects patients’ daily life, and is relevant to patients in relation to fluctuating aspects of RA such as flare and low disease activity. Morning stiffness is also frequently used as an outcome measure both clinically and in research. Despite the relevance and uses of stiffness, it remains poorly understood and was omitted from the RA core set because of poor measurement properties. A pragmatic, mixed methods approach was used to better understand the patient experience of stiffness in people with RA and to develop and test a new RA stiffness patient reported outcome measure (PROM). It involved a systematic literature review, semi-structured interviews, focus groups, cognitive interviews, the development of appropriate candidate items to characterise stiffness and multivariate analysis of a survey using these items.The systematic literature review found that current stiffness assessment is based on items that capture the duration or severity of morning stiffness. However, items were often poorly defined, highly variable in wording and format, had limited measurement property evidence and had not been developed according to current standards including collaboration with patients. Overall, there was no evidence regarding the most appropriate way to assess stiffness in RA, indicating the need for a new measure developed according to best practice PROM guidelines. Semi-structured interviews with RA patients provided an improved understanding of their experience of stiffness, demonstrated its relevance to patients and enabled the development of a conceptual model. These data also highlighted inconsistencies between current stiffness assessment and the patient perspective of this symptom. Focus groups with RA patients reinforced the stiffness conceptual model in a new sample, using a different method of data collection. They also provided information specifically addressing stiffness assessment from the patient perspective, including a number of concepts for measurement instrument development. These patient-driven concepts and qualitative data were tempered with measurement theory to develop a conceptually sound yet practically appropriate preliminary set of items for a new RA stiffness PROM. Preliminary items were reviewed and modified by RA patients in cognitive interviews. Following refinement, 45 candidate items (39 new items and 6 traditional stiffness items) were taken forward to a postal survey to develop and test the structure of a new RA stiffness PROM. Analysis of the survey responses involved rigorous statistical testing including a series of iterative principal component analyses (undertaken initially with two different approaches), balancing Cronbach’s alpha for internal consistency, bootstrapping for stability, and expert judgement for clinical appropriateness. The emergent structure was the Rheumatoid Arthritis Stiffness (RAST) questionnaire with 21 items in 3-components capturing ‘stiffness severity’, ‘physical impact’ and ‘psychosocial impact’. The initial qualitative work enhanced its content validity and statistical testing for appropriate relationships with other measures of disease demonstrated good construct validity. These results provide support for RAST as an appropriate tool for use in future stiffness assessment. The development of the RAST is important in recognising stiffness as a relevant patient symptom and is a significant step towards standardised stiffness assessment. Further testing in a fresh population will generate additional evidence of reliability and sensitivity to change to support its use. The RAST provides a measure for use in new investigations of disease mechanisms and response to therapy

    Arcs on Determinantal Varieties

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    We study arc spaces and jet schemes of generic determinantal varieties. Using the natural group action, we decompose the arc spaces into orbits, and analyze their structure. This allows us to compute the number of irreducible components of jet schemes, log canonical thresholds, and topological zeta functions.Comment: 27 pages. This is part of the author's PhD thesis at the University of Illinois at Chicago. v2: Minor changes. To appear in Transactions of the American Mathematical Societ

    On Breakdown Criteria for Nonvacuum Einstein Equations

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    The recent "breakdown criterion" result of S. Klainerman and I. Rodnianski stated roughly that an Einstein-vacuum spacetime, given as a CMC foliation, can be further extended in time if the second fundamental form and the derivative of the lapse of the foliation are uniformly bounded. This theorem and its proof were extended to Einstein-scalar and Einstein-Maxwell spacetimes in the author's Ph.D. thesis. In this paper, we state the main results of the thesis, and we summarize and discuss their proofs. In particular, we will discuss the various issues resulting from nontrivial Ricci curvature and the coupling between the Einstein and the field equations.Comment: 62 pages This version: corrected minor typos, expanded Section 6 (geometry of null cones
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