Latent class modelling is one method used in the evaluation of diagnostic tests when there is no gold standard test that is perfectly accurate. The technique demonstrates maximum likelihood estimates of the prevalence of a disease or a condition and the error rates of diagnostic tests or observers. This study reports the effect of departures from the latent class model assumption of independent misclassifications between observers or tests conditional on the true state of the individual being tested. It is found that estimates become biased in the presence of dependence. Most commonly the prevalence of the disease is overestimated when the true prevalence is at less than 50% and the error rates of dependent observers are underestimated. If there are also independent observers in the group, their error rates are overestimated. The most dangerous scenario in which to use latent class methods int he evaluation of tests is when the true prevalence is low and the false positive rate is high. This is common to many screening situations. / Thesis / Master of Science (MS)

High rates of medical errors are well documented within the healthcare industry. Nurses, in particular, play a critical role in the quality and safety of healthcare services. Fatigue is a factor that has been linked to stress, safety, and performance decrements in numerous work environments. Within healthcare, however, a comprehensive definition of fatigue encompassing multiple dimensions has not been considered, but is warranted since nurses perform tasks consisting of diverse physical and mental activities. As such, "total fatigue" was examined, as were interactions between its underlying dimensions and the effects of these dimensions on performance, in the context of actual and simulated nursing work. In a survey study (Chapter 2), registered nurses reported relatively high levels of mental, physical, and total fatigue, and higher levels of fatigue were associated with perceived decreases in performance. Work environment variables, such as work schedule or shift length, were also related to differences in reported fatigue levels. An experimental study investigated causal effects of mental and physical fatigue on mental and physical performance (Chapter 3). Mental fatigue affected a measure of mental performance, and physical fatigue had a negative effect on measures of physical and mental performance. A multidimensional view of fatigue that considers direct and crossover effects between mental and physical dimensions of fatigue and performance is relevant when quantifying effects of fatigue on performance. A model of the relationships between fatigue dimensions and performance in nursing was developed using structural equation modeling techniques (Chapter 4). The model supported the existence of a total fatigue construct that is directly affected by mental and physical fatigue levels. The final model also provides quantitative path coefficients defining the strength of relationships between mental and physical dimensions of fatigue, total fatigue, and mental and physical performance. The current research provides an increased understanding of fatigue levels in registered nurses across work environments, as well as the underlying causal mechanisms between dimensions of fatigue and performance decrements. The findings and the final model can aid in designing interventions to reduce or eliminate the contributions of fatigue to the occurrence of medical errors. / Ph. D.

Background: Recent research is revealing the high rate of false-positive screening results for IEMs in the NICU population. No study published to date has specifically studied the possible relationship between nutrition and newborn screening in this population. Objective: It is suspected that NICU infants who receive PN are more likely to have abnormal newborn screening results than infants who receive EN. An understanding of the role of nutrition will assist in developing protocols for screening in the NICU and decrease false-positives. Design: Infants admitted to the NICU between January 1-June 30, 2009 were included in this retrospective chart review study (n=339). The type of nutrition and timing of its initiation was recorded and compared to newborn screening results to identify correlations with false-positives. Statistical analysis included means, percentages, Fisher's exact test, Chi-square test, and the Cochran-Mantel-Haenszel test. Results: Nutrition type was significantly associated with newborn screening (p<0.001); those who received parenteral nutrition were more likely to have a false-positive. For infants who also received PN, EN of breast milk exclusively increased risk of an abnormal screen more than formula exclusively or breast milk plus formula. The timing of parenteral nutrition had no effect on screening. Premature infants who received PN exclusively had a higher percentage of false-positives than those who received EN Conclusions: Although the hypothesis could not be statistically supported, PN appears to contribute to false-positive newborn screens. More research is needed to ascertain the role of EN and GA in newborn screening and to develop standardized protocols. / Master of Science

No / There is growing demand for cost effective and reliable floating production systems to maximize marginal and new deepwater fields worldwide. Floating Production Storage and Offloading (FPSO) vessels are considered to be the most economical and viable options to meet this demand. Yet, FPSO projects are prone to significant cost and schedule growth. On average, FPSOs have been reported to experience a 20% cost growth and are delayed by six months. Overruns and delays represent uncertainties for owners, contractors and financial institutions. In-depth interviews with twenty-three practitioners about their experiences with FPSO projects revealed that rework arising from design and construction errors were major contributors to cost and schedule growth. Key latent conditions contributing to rework are classified according to people, organization and project. Using retrospective sensemaking an examination of the determinant histories in a new build and conversion FPSO that experienced rework was undertaken. The sharing of experience(s) is deemed pivotal for reducing rework in future projects, particularly through the use of communities of practice that are able to stimulate situated learning to take place. A reduction in rework will not only reduce cost and schedule growth, improve operational performance and augment safety.

Yes / Human pluripotent stem cells (PSCs) are subject to the appearance of recurrent genetic variants on prolonged culture. We have now found that, compared with isogenic differentiated cells, PSCs exhibit evidence of considerably more DNA damage during the S phase of the cell cycle, apparently as a consequence of DNA replication stress marked by slower progression of DNA replication, activation of latent origins of replication, and collapse of replication forks. As in many cancers, which, like PSCs, exhibit a shortened G1 phase and DNA replication stress, the resulting DNA damage may underlie the higher incidence of abnormal and abortive mitoses in PSCs, resulting in chromosomal non-dysjunction or cell death. However, we have found that the extent of DNA replication stress, DNA damage, and consequent aberrant mitoses can be substantially reduced by culturing PSCs in the presence of exogenous nucleosides, resulting in improved survival, clonogenicity, and population growth.

Information processing has altered the structure of the traditional office. Typewriters are no longer a necessity to prepare written business communication. As a result of a metamorphosis from manual data manipulation to electronic data processing, microcomputers and their related peripheral equipment are becoming the key link in the information system. Increased usage of microcomputers and word processing software has been linked to decreased proficiency in detecting errors and in turn to decreased office productivity. Thus a number of questions arise including: Is it better to proofread from a hardcopy or a softcopy document? Does the color and contrast configuration of a video display terminal affect the operator's ability to proofread? The effect on the operator's ability to accurately detect errors in keyboarded text from different media has not been previously determined. This study was therefore completed to ascertain if a difference does exist. Seventy-two individuals enrolled in four word processing classes at a western North Carolina community college comprised the individuals participating in this study. Participants completed a demographic questionnaire, a pretest instrument, and one of four error detection instruments. The error detection instruments were presented in either a hardcopy or softcopy format. The softcopy format consisted of three video display terminal configurations. Analyses of covariance with pretest scores used as the covariate were used to compare the quantity and types of errors detected by error detection environment configurations. Based on the findings from the analyses of data the following conclusions were derived. 1. Postsecondary word processing students have difficulty in finding errors in hardcopy and softcopy documents. 2. Postsecondary word processing students' abilities to detect errors in keyboarded text were not affected by the error detection environment–hardcopy or softcopy–during a ten-minute error detection process. Therefore, the printing of a hardcopy of keyboarded text when detecting errors for a short time period is not necessary. 3. Postsecondary word processing students' abilities to detect errors in keyboarded text were not affected by the video display terminal configurations examined in this study. A video display terminal’s color configuration is not a factor in the error detecting process for a short time period-ten minutes. Therefore, the color configuration of a video display terminal should not be a major consideration when purchasing new video display terminals for instructional use. 4. As the spelling Verification feature of word processing software does not detect all types of errors, instruction is needed in detecting errors that cannot be detected by the software’s spelling Verification feature. / Ed. D.

Sexual abstinence has become the primary response to prevention against sexually transmitted infection (STI) and unplanned pregnancies amongst young people. However, not much is known about the perceptions of young men on sexual abstinence. The central aim in this study was to explore the perceptions of sexual abstinence among young black males. The research aims to examine men’s understandings of their own sexuality and the way these might influence their decision on sexual abstinence. A total of 10 in-depth semi-structured interviews were conducted individually with young men aged between 18 and 25 years, studying at The University of the Witwatersrand. All data collected were then qualitatively analysed through the use of thematic content analysis (TCA). Findings show that in constructing their masculinities participants predominantly endorsed discourses of male hegemony. At some instances the young men retracted to subjective alternative masculinities, although there was a stronger need to fit in with their peers, to protect themselves from being ridiculed or rejected. As such conforming to the hegemonic masculinity was expected. The young men constructed women as sexual objects and as a means towards affirming their masculinity. A key conclusion drawn was that some traditional notions of manhood still held sway, and these tied in strongly with how these participants constructed their masculinity and this influenced most of them to not sexually abstain.

The high incidence of medical and surgical errors in U.S. hospitals and clinics affects patients' safety. Not enough is known about the relationship between physician characteristics and medical error rates. The purpose of this quantitative correlational study was to examine the relationship between selected physician characteristics and surgical errors in U.S. hospitals. The ecological model was used to understand personal and systemic factors that might be related to the incidence of surgical errors. Archived data from the National Practitioner Data Bank database of physician surgical errors were analyzed using bivariate and multivariate logistic regression analyses. Independent variables included physicians' home state, state of license, field of license, age group, and graduation year group. The dependent variable was surgical medical errors. Physicians' field of license and state of license were significantly associated with surgical error. Findings contribute to the knowledge base regarding the relationship between physician characteristics and surgical medical errors, and findings may be used to improve patient safety and medical care.

<p>The intention is to draw more specific connections between certain deconvolution methods and also to demonstrate the application of the statistical theory of estimation in the presence of measurement error. A parametric methodology for deconvolution when the underlying distribution is of the Pareto form is developed. Maximum likelihood estimation (MLE) of the parameters of the convolved distributions is considered. Standard errors of the estimated parameters are calculated from the inverse Fisher&rsquo / s information matrix and a jackknife method. Probability-probability (P-P) plots and Kolmogorov-Smirnov (K-S) goodnessof- fit tests are used to evaluate the fit of the posited distribution. A bootstrapping method is used to calculate the critical values of the K-S test statistic, which are not available.</p>

<p>The intention is to draw more specific connections between certain deconvolution methods and also to demonstrate the application of the statistical theory of estimation in the presence of measurement error. A parametric methodology for deconvolution when the underlying distribution is of the Pareto form is developed. Maximum likelihood estimation (MLE) of the parameters of the convolved distributions is considered. Standard errors of the estimated parameters are calculated from the inverse Fisher&rsquo / s information matrix and a jackknife method. Probability-probability (P-P) plots and Kolmogorov-Smirnov (K-S) goodnessof- fit tests are used to evaluate the fit of the posited distribution. A bootstrapping method is used to calculate the critical values of the K-S test statistic, which are not available.</p>