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Pages
- Title
- Estimation for the Cox Model with Various Types of Censored Data.
- Creator
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Riddlesworth, Tonya, Ren, Joan, Mohapatra, Ram, Richardson, Gary, Ni, Liqiang, Schott, James, University of Central Florida
- Abstract / Description
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In survival analysis, the Cox model is one of the most widely used tools. However, up to now there has not been any published work on the Cox model with complicated types of censored data, such as doubly censored data, partly-interval censored data, etc., while these types of censored data have been encountered in important medical studies, such as cancer, heart disease, diabetes, etc. In this dissertation, we first derive the bivariate nonparametric maximum likelihood estimator (BNPMLE) Fn(t...
Show moreIn survival analysis, the Cox model is one of the most widely used tools. However, up to now there has not been any published work on the Cox model with complicated types of censored data, such as doubly censored data, partly-interval censored data, etc., while these types of censored data have been encountered in important medical studies, such as cancer, heart disease, diabetes, etc. In this dissertation, we first derive the bivariate nonparametric maximum likelihood estimator (BNPMLE) Fn(t,z) for joint distribution function Fo(t,z) of survival time T and covariate Z, where T is subject to right censoring, noting that such BNPMLE Fn has not been studied in statistical literature. Then, based on this BNPMLE Fn we derive empirical likelihood-based (Owen, 1988) confidence interval for the conditional survival probabilities, which is an important and difficult problem in statistical analysis, and also has not been studied in literature. Finally, with this BNPMLE Fn as a starting point, we extend the weighted empirical likelihood method (Ren, 2001 and 2008a) to the multivariate case, and obtain a weighted empirical likelihood-based estimation method for the Cox model. Such estimation method is given in a unified form, and is applicable to various types of censored data aforementioned.
Show less - Date Issued
- 2011
- Identifier
- CFE0004158, ucf:49051
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004158
- Title
- Analysis of Benzopyrenes and Benzopyrene Metabolites by Fluorescence Spectroscopy Techniques.
- Creator
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Al-Farhani, Bassam, Campiglia, Andres, Harper, James, Zou, Shengli, Frazer, Andrew, Lee, Woo Hyoung, University of Central Florida
- Abstract / Description
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Polycyclic aromatic hydrocarbons (PAHs) are some of the most common and toxic pollutants encountered worldwide. Presently, monitoring is restricted to sixteen PAHs, but it is well understood that this list omits many toxic PAHs. Among the (")forgotten(") PAHs, isomers with molecular weight 302 are of particular concern due to their high toxicological properties. The chromatographic analysis of PAHs with MW 302 is challenged by similar retention times and virtually identical mass fragmentation...
Show morePolycyclic aromatic hydrocarbons (PAHs) are some of the most common and toxic pollutants encountered worldwide. Presently, monitoring is restricted to sixteen PAHs, but it is well understood that this list omits many toxic PAHs. Among the (")forgotten(") PAHs, isomers with molecular weight 302 are of particular concern due to their high toxicological properties. The chromatographic analysis of PAHs with MW 302 is challenged by similar retention times and virtually identical mass fragmentation patterns.The first original component of this dissertation evolves from a high-resolution spectroscopic approach specifically developed to fulfil this gap. Herein, 4.2 K Laser-Excited Time-Resolved Shpol'skii Spectroscopy (4.2K LETRSS) is applied to the analysis of HMW-PAHs in a complex coal tar standard reference material (SRM 1597a). The spectral and lifetime information obtained with LETRSS provide the required selectivity for the unambiguous determination of PAH isomers in the high-performance liquid chromatography (HPLC) fractions. Complete LETRSS analysis is possible with microliters of HPLC fractions and organic solvent. The excellent analytical figures of merit associated to its non-destructive nature, which provides ample opportunity for further analysis with other instrumental methods, makes this approach a unique alternative for the analysis of isomers of HMW-PAHs in complex environmental samples.The second original component of this dissertation focuses on the development of screening methodology for the routine analysis of PAH metabolites in urine samples. It explores the room-temperature fluorescence (RTF) properties of 3-hydroxy-benzo[a]pyrene, benzo[a]pyrene-trans-9,10-dihydrodiol, benzo[a]pyrene-r-7,t-8,c-9-tetrahydrotriol and benzo[a]pyrene-r-7,t-8,c-9,c-10-tetrahydrotetrol previously extracted with octadecyl-silica membranes. RTF measurements from extraction membranes are carried out with the aid of fiber optic probe that eliminates the need for manual optimization of signal intensities. Relative standard deviations varying from 2.07% (benzo[a]pyrene-r-7,t-8,c-9-tetrahydrotriol) to 8.55% (3-hydroxy-benzo[a]pyrene) were obtained with a straightforward procedure. Analytical recoveries from human urine samples varied from 87.54 (&)#177; 3.11% (3-hydroxy-benzo[a]pyrene) to 99.77 (&)#177; 2.48% (benzo[a]pyrene-r-7,t-8,c-9,c-10-tetrahydrotetrol). The excellent analytical figures of merit and the simplicity of the experimental procedure demonstrate the potential of Solid phase extraction-RTF for screening biomarkers of PAH exposure in numerous urine samples.
Show less - Date Issued
- 2016
- Identifier
- CFE0006520, ucf:51363
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006520
- Title
- CLAIMS OF MISTAKEN IDENTITY:AN EXAMINATION OF U.S. TELEVISION FOOD COMMERCIALS AND THE ADULT OBESITY ISSUE.
- Creator
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Delgado, Cristina, DeLorme, Denise, University of Central Florida
- Abstract / Description
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Obesity is one of the major public health issues in the United States, often regarded as part of a global crisis. Companies invest billions of dollars each year towards television advertising campaigns aimed at convincing audiences how their ground-breaking discovery 'battles the bulge' or somehow offers an increased health benefit. This study examined how advertisers presented health-related claims, including health and nutrient-content claims, in U.S. adult-targeted television food...
Show moreObesity is one of the major public health issues in the United States, often regarded as part of a global crisis. Companies invest billions of dollars each year towards television advertising campaigns aimed at convincing audiences how their ground-breaking discovery 'battles the bulge' or somehow offers an increased health benefit. This study examined how advertisers presented health-related claims, including health and nutrient-content claims, in U.S. adult-targeted television food commercials. The claims were compared to FTC, FDA, and USDA laws, regulations, and recommendations. A content analysis of food advertising was conducted of commercials from major and cable network programs broadcast during prime-time in the first quarter of 2009. The majority of claims match current regulations when compared to Federal references. The results show that Nutrient and Wellness claims were the most frequently cited. The type of benefit, Healthy Eating, emerged almost 3 times more than any other benefit type. This is also similar to those results which suggest advertisers' intentions were to promote overall wellness in their content delivery. As such, the Wellness Approach was identified and conceptualized, leading towards full development of a Wellness Effect theory. Implications and future research opportunities are discussed on both a theoretical and practical level.
Show less - Date Issued
- 2009
- Identifier
- CFE0002565, ucf:48260
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002565
