Reporting of measures of accuracy in systematic reviews of diagnostic literature

BACKGROUND: There are a variety of ways in which accuracy of clinical tests can be summarised in systematic reviews. Variation in reporting of summary measures has only been assessed in a small survey restricted to meta-analyses of screening studies found in a single database. Therefore, we performed this study to assess the measures of accuracy used for reporting results of primary studies as well as their meta-analysis in systematic reviews of test accuracy studies. METHODS: Relevant reviews on test accuracy were selected from the Database of Abstracts of Reviews of Effectiveness (1994–2000), which electronically searches seven bibliographic databases and manually searches key resources. The structured abstracts of these reviews were screened and information on accuracy measures was extracted from the full texts of 90 relevant reviews, 60 of which used meta-analysis. RESULTS: Sensitivity or specificity was used for reporting the results of primary studies in 65/90 (72%) reviews, predictive values in 26/90 (28%), and likelihood ratios in 20/90 (22%). For meta-analysis, pooled sensitivity or specificity was used in 35/60 (58%) reviews, pooled predictive values in 11/60 (18%), pooled likelihood ratios in 13/60 (22%), and pooled diagnostic odds ratio in 5/60 (8%). Summary ROC was used in 44/60 (73%) of the meta-analyses. There were no significant differences in measures of test accuracy among reviews published earlier (1994–97) and those published later (1998–2000). CONCLUSIONS: There is considerable variation in ways of reporting and summarising results of test accuracy studies in systematic reviews. There is a need for consensus about the best ways of reporting results of test accuracy studies in reviews

Pseudogaps in Underdoped Cuprates

It has become clear in the past several years that the cuprates show many unusual properties, both in the normal and superconducting states, especially in the underdoped region. In particular, gap-like behavior is observed in magnetic properties, c-axis conductivity and photoemission, whereas in-plane transport properties are only slightly affected by the pseudogap. I shall argue that these experimental evidences must be viewed in the context of the physics of a doped Mott insulator and that they support the notion of spin charge separation. I shall review recent theoretical developments, concentrating on studies based on the t-J model. I shall describe a model based on quasiparticle excitations, which predicts the doping dependence of T_c and anomalous energy-gap-to-T_c ratios. Finally, I shall outline how the model may be derived from a microscopic formulation of the t-J model. After a brief review of the U(1) formulation, I shall explain some of the difficulties encountered there, and how a new SU(2) formulation can resolve some of the difficulties.Comment: 9 pages, 4 figure

Inspection and replacement models for reliability and maintenance: filling in gaps

A thesis submitted in fulfillment of the requirements for the Degree of Doctor of Philosophy, School of Statistics and Actuarial Science, Faculty of Science University of Witwatersrand, Johannesburg. February 2017.The work done in this thesis on finite planning horizon inspection models has demonstrated that with the advent of powerful computers these days it is possible to easily find an optimal inspection schedule when the lifetime distribution is known. For the case of system time to failure following a uniform distribution, a result for the maximum number of inspections for the finite planning models has been derived. If the time to failure follows an exponential distribution, it has been noted that periodically carrying out inspections may not result in maximization of expected profit. For the Weibull distributions family (of which the exponential distribution is a special case), evenly spreading the inspections over a given finite planning horizon may not lead to any serious prejudice in profit. The case of inspection models where inspections are of non-negligible duration has also been explored. The conditions necessary for inspections that are evenly spread over the entire planning horizon to be near-optimal when system time to failure either follows a uniform distribution or exponential distribution have been explored. Finite and infinite planning horizon models where inspections are imperfect have been researched on. Interesting observations on the impact of Type I and Type II errors in inspection have been made. These observations are listed on page 174. A clear and easy to implement road map on how to get an optimal inspection permutation in problems first discussed by Zuckerman (1989) and later reviewed by Qiu (1991) for both the undiscounted and discounted cases has been given. The only challenge envisaged when a system has a large number of components is that of computer memory requirements - which nowadays is fast being overcome. In particular, it has been clearly demonstrated that the impact of repair times and per unit of time repair costs on the optimal inspection permutation cannot be ignored. The ideas and procedures of determining optimal inspection permutations which have been developed in this thesis will no doubt lead to huge cost savings especially for systems where the cost of inspecting components is huge.XL201

Validation Study Of The Integral-Differential Scheme For Multi-Block Grids

This MS Thesis seeks to validate the accuracy of the Integral-Differential Scheme (IDS). In the attempts to accomplish this task, research efforts were focused on the scheme’s ability to capture the physics of known flow fields, as well as the scheme’s ability to predict the features of flow field quantities that may be derived from experimental measurements. The IDS was developed with the goal of being computationally efficient, from a programming perspective, as well as being numerically accurate, stable, and robust, from a mathematical perspective. The IDS is designed to solve the full Navier-Stokes equations in their integral forms. Unlike traditional control volume schemes, the IDS is built upon two sets of cells: spatial and temporal cells. For 2-D flows, the IDS considers an elementary control volume as a collection of four spatial cells and a single temporal cell. Similar to other explicit CFD schemes, the IDS relies on the use of the Taylor series expansion and other traditional CFD criteria. It is of interest to note that there are previous IDS validation studies which were conducted at North Carolina A&T State University. These past studies mainly focused on the qualitative aspects of the flow field physics. Furthermore, in all cases, they focused on flow field problems that can be represented by single-block grids. In this analysis, the validation studies are focused on multi-block grids in which the physics of the flow field is made complicated due to the presence of shock waves and flow separation zones. Of interest to this MS Thesis are two supersonic flow field problems that are supported by experimental data; namely, the supersonic flow over a rearward-facing step problem and the supersonic flow over a cavity problem. The validation studies conducted herein demonstrated that the IDS was able to predict the experimental data in both cases

Validation Study Of The Integral-Differential Scheme For Multi-Block Grids

This MS Thesis seeks to validate the accuracy of the Integral-Differential Scheme (IDS). In the attempts to accomplish this task, research efforts were focused on the scheme’s ability to capture the physics of known flow fields, as well as the scheme’s ability to predict the features of flow field quantities that may be derived from experimental measurements. The IDS was developed with the goal of being computationally efficient, from a programming perspective, as well as being numerically accurate, stable, and robust, from a mathematical perspective. The IDS is designed to solve the full Navier-Stokes equations in their integral forms. Unlike traditional control volume schemes, the IDS is built upon two sets of cells: spatial and temporal cells. For 2-D flows, the IDS considers an elementary control volume as a collection of four spatial cells and a single temporal cell. Similar to other explicit CFD schemes, the IDS relies on the use of the Taylor series expansion and other traditional CFD criteria. It is of interest to note that there are previous IDS validation studies which were conducted at North Carolina A&T State University. These past studies mainly focused on the qualitative aspects of the flow field physics. Furthermore, in all cases, they focused on flow field problems that can be represented by single-block grids. In this analysis, the validation studies are focused on multi-block grids in which the physics of the flow field is made complicated due to the presence of shock waves and flow separation zones. Of interest to this MS Thesis are two supersonic flow field problems that are supported by experimental data; namely, the supersonic flow over a rearward-facing step problem and the supersonic flow over a cavity problem. The validation studies conducted herein demonstrated that the IDS was able to predict the experimental data in both cases

Tanggapan Perseptual Guru Bahasa Inggris Di SD Se-surakarta Terhadap Kebijakan Pelaksanaan Mata Pelajaran Bahasa Inggris Di Sekolah Dasar

This qualitative descriptive study aims to describe how the perceptual response of teachersof English in primary schools towards the government policy related to the implementationof English subjects in elementary school. Population of this research is Englishteachers at the elementary school in Surakarta and takes a sample of English teachersfrom primary schools in partnership with UMS PGSD as many as 20 teachers ofEnglish. Methods of data collection in this study using observations, interviews anddocumentation, and analysis with interactive analysis. In this research, the elementaryteachers as research respondents divided into two groups of teachers who have educationalbackgrounds of English and non-English language. These two groups, dividedinto four categories. The first category are teachers who have a background in Englisheducation with teaching experience less than or equal to ten years. The second categoryare teachers with educational background in English with teaching experience morethan ten years. The third categoryare teachers with backgrounds non English with teachingexperience less than ten years. The fourth category are teachers with backgroundsnon English with teaching experience more than ten years. The findings found in perceptualresponse from the four categories of teachers, show that basically they comprehendthat the implementation of English subjects in elementary school is very importantdue to many reasons. The teachers agree toward the implementation of Englishsubject at elementary school as long as it is conducted seriously and in a professionalways rather than as a additional curriculum

Nurses' religious and cultural beliefs and its influences on healthcare provision for women seeking termination of pregnancy : a case study of Grey's hospital.

M.Th. University of KwaZulu-Natal, Pietermaritzburg 2014.The political liberation of South Africa in 1994 gave its people the right to freedom of expression, thought and religion. This has led to the promulgation of the Choice of Termination of Pregnancy Act of 1996 (Act No. 2 of 1996) in order to promote the freedom of women and give them agency over reproductive health. The Choice of Termination of Pregnancy Act not only promoted reproductive health among women, but it also shaped the outlook of nursing practice to ensure that the termination of pregnancy service is translated into good nursing practice at public hospitals across the country. This study, which is qualitative in nature, explores nurses’ religious and cultural beliefs and its effect on healthcare provision to women seeking termination of pregnancy services at public hospitals. Six nursing professionals involved in termination of pregnancy services at a public hospital were interviewed as research participants in the study with the aim of obtaining individual opinions regarding its provision and the significance and impact of their religious convictions in service delivery at a public hospital. The thematic analysis method was used to interpret and analyse the data received and to reach conclusions and recommendations for the study. The major themes that emerged from the research participants were as follows: (i) personal conviction and preferences in addressing issues such as an ethics of care and a human rights discourse in public health; (ii) social attitudes about termination of pregnancy, covering issues such as affirmation, acceptance or stigmatisation in regard to termination of pregnancy; (iii) the religious convictions of nurses and the termination of pregnancy and the extent to which religion is a deficit or asset in its provision at public hospitals in South Africa

Insect infestation sources in stored maize grain; what is more important resident versus incoming infestation?

Most studies targeted pest control inside stores; incognisant of the population dynamics in the store vicinity; leading to product re-infestation. Distinction between storage insect pest source and sink grain patches is important for effective pest management strategies. We examined the role of resident versus incoming insect infestation in phosphine-fumigated closed or open and unfumigated closed or open maize farm stores. Grain quality measurements were recorded over 32 weeks for two storage seasons. Whether open or closed, fumigated grain had significantly lower (p < 0.001) grain damage and lower grain weight loss (p < 0.05) than unfumigated grain. Fumigated open stores had significantly higher (p= 0.004) grain damage and weight loss than closed ones. Grain damage was higher in unfumigated-closed than fumigated-open, evidence that resident infestation inflicted higher food loss than incoming infestation. Prostephanus truncatus, Cryptolestes ferrugineus and Tribolium castaneum had significantly higher populations (p < 0.001, p = 0.018 and p = 0.001; respectively) at bottom levels of unfumigated and fumigated grain (T. castaneum). Sitotroga cerealella and Sitophilus zeamais were significantly higher (p < 0.001) at the top of closed than open unfumigated compartments. Grain suffers less infestation and quality loss when it is a sink patch than when it is a source patch. Population build-up and ‘settling’ to inflict significant food loss takes longer for incoming compared to resident infestation. These results have ecological implications on postharvest IPM.Most studies targeted pest control inside stores; incognisant of the population dynamics in the store vicinity; leading to product re-infestation. Distinction between storage insect pest source and sink grain patches is important for effective pest management strategies. We examined the role of resident versus incoming insect infestation in phosphine-fumigated closed or open and unfumigated closed or open maize farm stores. Grain quality measurements were recorded over 32 weeks for two storage seasons. Whether open or closed, fumigated grain had significantly lower (p < 0.001) grain damage and lower grain weight loss (p < 0.05) than unfumigated grain. Fumigated open stores had significantly higher (p= 0.004) grain damage and weight loss than closed ones. Grain damage was higher in unfumigated-closed than fumigated-open, evidence that resident infestation inflicted higher food loss than incoming infestation. Prostephanus truncatus, Cryptolestes ferrugineus and Tribolium castaneum had significantly higher populations (p < 0.001, p = 0.018 and p = 0.001; respectively) at bottom levels of unfumigated and fumigated grain (T. castaneum). Sitotroga cerealella and Sitophilus zeamais were significantly higher (p < 0.001) at the top of closed than open unfumigated compartments. Grain suffers less infestation and quality loss when it is a sink patch than when it is a source patch. Population build-up and ‘settling’ to inflict significant food loss takes longer for incoming compared to resident infestation. These results have ecological implications on postharvest IPM

Logistic regression to determine significant factors associated with share price change

This thesis investigates the factors that are associated with annual changes in the share price of Johannesburg Stock Exchange (JSE) listed companies. In this study, an increase in value of a share is when the share price of a company goes up by the end of the financial year as compared to the previous year. Secondary data that was sourced from McGregor BFA website was used. The data was from 2004 up to 2011. Deciding which share to buy is the biggest challenge faced by both investment companies and individuals when investing on the stock exchange. This thesis uses binary logistic regression to identify the variables that are associated with share price increase. The dependent variable was annual change in share price (ACSP) and the independent variables were assets per capital employed ratio, debt per assets ratio, debt per equity ratio, dividend yield, earnings per share, earnings yield, operating profit margin, price earnings ratio, return on assets, return on equity and return on capital employed. Different variable selection methods were used and it was established that the backward elimination method produced the best model. It was established that the probability of success of a share is higher if the shareholders are anticipating a higher return on capital employed, and high earnings/ share. It was however, noted that the share price is negatively impacted by dividend yield and earnings yield. Since the odds of an increase in share price is higher if there is a higher return on capital employed and high earning per share, investors and investment companies are encouraged to choose companies with high earnings per share and the best returns on capital employed. The final model had a classification rate of 68.3% and the validation sample produced a classification rate of 65.2%Mathematical SciencesM. Sc. (Statistics

Environmental Factors, Employee-Resourcing Strategies And Performance Of Small Restaurant Businesses In South Africa: A Structural Equation Modelling Approach

Small restaurant business sector is applauded for promoting economic growth and employment creation in developing economies. Despite the spirited efforts by developing nations to capacitate the sector to sustainably contribute to economic growth, it is often marred by a disturbing high failure rate, especially in South Africa. The failure rates have been attributed, among many other factors, to the inability of the small restaurant businesses to respond to the environmental uncertainty for increased performance. In addition, small restaurant businesses in developing economies have been found to share common characteristics with small businesses in other sectors, in terms of using ad hoc approaches to employee – resourcing. Yet, the adoption of proper employee-resourcing strategies such as doing workforce planning, formalising recruitment and staff retention are regarded as best human resource practices for optimum business performance. In addition, the contribution of environmental factors such as manager‘s expertise and experience, economic growth, and political stability in leveraging the adoption of effective employee-resourcing strategies and heightening business performance has been reported. There is however a dearth of research that explores the interplay of environmental influences, employee-resourcing strategies and performance of small businesses in a developing context. There is also a paucity of literature that explores whether a convivial relationship exists among environmental factors, employee-resourcing strategies and business performance among in South Africa. Furthermore, empirical evidence on the influence of employee-resourcing strategies on small business performance in the hospitality industry among emerging economies is disappointingly low. It is against this background that this research used the Resource Based View (RBV), the Human Capital Theory, the Flexible Firm Model, Contingency theory and reviewed literature to gain an understanding on whether the internal and external environmental factors inform the adoption of employee-resourcing strategies, culminating in increased business performance. Using Structural Equation Modelling (SEM), the research proposes that the pathway to improved business performance demands small restaurant business owner-managers to adopt systemic and holistic approaches to employee-resourcing strategies that are attuned to the internal and external environmental factors to guarantee increased business performance. The research was informed by the positivist paradigm and a quantitative research approach was adopted to test the proposed conceptual model. A structured questionnaire was administered to 221 owners/managers of small restaurant businesses in Free State Province, South Africa. Convenience sampling was employed to select the respondents. SEM was used to empirically test the hypothesised relationships in the conceptual model. The results showed that the structural model fitted the data satisfactorily and provided reasonable explanations on the nature of relationships among internal and external environmental factors, employee-resourcing strategies and small business performance in South African restaurants. The results established a positive and significant effect of the internal environmental factors on employee-resourcing strategies. Furthermore, the results also revealed a positive and significant effect of the external environment on employee-resourcing strategies. However, contrary to predictions, there were no relationships between internal and external environmental factors, employee-resourcing strategies and small restaurant performanc