Formation studies on N-nitrosodimethylamine (NDMA) in natural waters

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on August 3, 2007)Vita.Thesis (Ph. D.) University of Missouri-Columbia 2006.N-nitrosodimethylamine (NDMA) is a chloramines disinfection by-product and probable carcinogen to human. The California state established a 10 ng/L action level for NDMA in drinking water. Analytical method of NDMA in waters at the trace level was developed using gas chromatography/mass spectrum with chemical ionization in the mode of selected ion storage coupled with solid phase extraction. It was found that 4 utilities in Missouri using monochloramine as disinfectant had NDMA higher than 10 ng/L in drinking water. Natural organic matter (NOM), especially the hydrophilic fraction of the NOM, was found to be a predominant NDMA precursors. Basic conditions and bromide ions favor NDMA formation in natural waters. The findings reported in this dissertation provide data on NDMA occurrences in drinking water and natural waters in Missouri. The results provide valuable information about NDMA precursors in natural waters and this information could be used in the further study of mitigating NDMA formation or removing NDMA precursors in drinking water utilities. The results on factors affecting on NDMA formation provide more information for water utilities to determine operation conditions to reduce and control NDMA formation

RECURRENT EVENT MODELS IN THE PRESENCE OF A TERMINAL EVENT: COMPARISON, INFERENCE AND DATA ANALYSIS

This article focuses on statistical implications of proportional rate models for recurrent event data in the presence of a terminal event. In such circumstances, various definitions of the recurrent rate function have been adopted in the proportional rate models. Although these rate functions have quite different interpretations, recognition of the differences has been lacking theoretically and practically. We compare three types of rate functions from both conceptual and quantitative perspectives; conclude that the inappropriate choice of a rate function may lead to misleading scientific conclusions. Simulations are conducted for comparisons of the focused models. Analysis of data from an AIDS clinical trial is presented to illustrate the analytical results

Semiparametric regression analysis for alternating recurrent event data

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142558/1/sim7563_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142558/2/sim7563.pd

Effects of Very Low Nicotine Content Cigarettes on Smoking Behavior and Biomarkers of Exposure in Menthol and Non-menthol Smokers.

IntroductionBecause 30% of cigarettes sold in the United States are characterized as menthol cigarettes, it is important to understand how menthol preference may affect the impact of a nicotine reduction policy.MethodsIn a recent trial, non-treatment-seeking smokers were randomly assigned to receive very low nicotine cigarettes (VLNC; 0.4 mg nicotine/g tobacco) or normal nicotine cigarettes (NNC; 15.5 mg/g) for 20 weeks. On the basis of preference, participants received menthol or non-menthol cigarettes. We conducted multivariable regression analyses to examine whether menthol preference moderated the effects of nicotine content on cigarettes per day (CPD), breath carbon monoxide (CO), urinary total nicotine equivalents (TNE), urinary 2-cyanoethylmercapturic acid (CEMA), and abstinence.ResultsAt baseline, menthol smokers (n = 346) reported smoking fewer CPD (14.9 vs. 19.2) and had lower TNE (52.8 vs. 71.6 nmol/mg) and CO (17.7 vs. 20.5 ppm) levels than non-menthol smokers (n = 406; ps < .05). At week 20, significant interactions indicated that menthol smokers had smaller treatment effects than non-menthol smokers for CPD (-6.4 vs. -9.3), TNE (ratio of geometric means, 0.22 vs. 0.10) and CEMA (ratio, 0.56 vs. 0.37; ps < .05), and trended toward a smaller treatment effect for CO (-4.5 vs. -7.3 ppm; p = .06). Odds ratios for abstinence at week 20 were 1.88 (95% confidence interval [CI] = 0.8 to 4.4) for menthol and 9.11 (95% CI = 3.3 to 25.2) for non-menthol VLNC smokers (p = .02) relative to the NNC condition.ConclusionsAlthough menthol smokers experienced reductions in smoking, toxicant exposure, and increases in quitting when using VLNC cigarettes, the magnitude of change was smaller than that observed for non-menthol smokers.ImplicationsResults of this analysis suggest that smokers of menthol cigarettes may respond to a nicotine reduction policy with smaller reductions in smoking rates and toxicant exposure than would smokers of non-menthol cigarettes

Designing for and Reflecting upon Resilience in Health and Wellbeing

Resilience has been a long-standing theme in HCI research and design. However, prior work has different conceptualizations of resilience, tackles resilience at different scales, and focuses on resilience as the ability to adapt to adversity. This one-day workshop will bring together HCI researchers, interaction designers, healthcare professionals, healthcare service users, and carepartners to critically reflect upon the epistemological stances on resilience and foreground the notion of resilience in health and wellbeing research. Our workshop themes include: 1) reflecting upon the diverse conceptualizations of resilience; 2) designing for resilience from a social justice perspective; 3) designing for multi-stakeholder resilience for individuals, families, communities, and society

Analysis of recurrent event data under the case-crossover design with applications to elderly falls

SUMMARY The case-crossover design is useful for studying the effects of transient exposures on short-term risk of diseases or injuries when only data on cases are available. The crossover nature of this design allows each subject to serve as his own control. While the original design was proposed for univariate event data, in many applications recurrent events are often encountered (e.g., elderly falls, gout attacks, and sexually transmitted infections). In such situations, the within-subject dependence among recurrent events needs to be taken into account in the analysis. We review three existing conditional logistic regression-based approaches for analyzing recurrent event data under the case-crossover design. A simple approach is to use only one (e.g. the first) event for each subject, such that no assumption on the correlation among multiple events is needed, while we would expect loss of efficiency in estimation. events, conditionally on a subject-level latent variable and a set of observed time-varying covariates. In this paper, we propose to adjust the conditional logistic regression using either a within-subject pairwise resampling technique or a weighted estimating equation. No specific dependency structure among the recurrent events is needed for these two methods. We also propose a weighted MantelHaenszel estimator for situations with a binary exposure. Simulation studies are conducted to evaluate the performance of the discussed methods. We present the analysis of a study of the effect of medication changes on falls among the elderly

Near-infrared emission of Yb3+ through energy transfer from ZnO to Yb3+ in glass ceramic containing ZnO nanocrystals.

International audienceYb(3+)-doped glass and glass ceramic containing ZnO nanocrystals were prepared by the melting-quenching method and subsequent heat treatment. Intense near-IR emission around 1000 nm that originated from the transition of Yb(3+):(2)F(5/2)→(2)F(7/2) was generated as a result of energy transfer from oxygen interstitials in ZnO nanocrystals to Yb(3+) with energy transfer efficiency of about 10%. The quantum yield for the near-IR emission of Yb(3+) under the excitation of 390 nm was about 16.7%. These materials have potential application in achieving high-efficiency Si solar cells via spectrum modification