Search

BackgroundAfrican American (AA) smokers experience greater tobacco-related disease burden than Whites, despite smoking fewer cigarettes per day (CPD). Understanding factors that influence daily nicotine intake in AA smokers is an important step toward decreasing tobacco-related health disparities. One factor of interest is smoking topography, or the study of puffing behavior.Aims(i) to create a model using puff characteristics, nicotine dependence, and nicotine metabolism to predict daily nicotine exposure, and (ii) to compare puff characteristics and nicotine intake from two cigarettes smoked at different times to ensure the reliability of the puff characteristics included in our model.MethodsSixty AA smokers smoked their preferred brand of cigarette at two time points through a topography device. Plasma nicotine, expired CO, and changes in subjective measures were measured before and after each cigarette. Total nicotine equivalents (TNE) was measured from 24-hour urine collected during ad libitum smoking.ResultsIn a model predicting daily nicotine exposure, total puff volume, CPD, sex, and menthol status were significant predictors (R(2) = 0.44, P < 0.001). Total puff volume was significantly greater and inter-puff intervals were significantly shorter after ad lib smoking compared with the first cigarette of the day, but puffing behaviors for both cigarettes were highly correlated (r range = 0.69-0.89, P < 0.001) within-subjects.ConclusionThis is the first study, to our knowledge, to show that puff characteristics of individual cigarettes are predictive of daily nicotine intake.ImpactThese findings enhance our understanding of the relationship between smoking behavior and nicotine intake in AA smokers. Cancer Epidemiol Biomarkers Prev; 25(6); 936-43. ©2016 AACR.

Rate of nicotine metabolism has been identified as an important factor influencing nicotine intake and can be estimated using the nicotine metabolite ratio (NMR), a validated biomarker of CYP2A6 enzyme activity. Individuals who metabolize nicotine faster (higher NMR) may alter their smoking behavior to titrate their nicotine intake in order to maintain similar levels of nicotine in the body compared to slower nicotine metabolizers. There are known racial differences in the rate of nicotine metabolism with African Americans on average having a slower rate of nicotine metabolism compared to Whites. The goal of this study was to determine if there are racial differences in the relationship between rate of nicotine metabolism and measures of nicotine intake assessed using multiple biomarkers of nicotine and tobacco smoke exposure. Using secondary analyses of the screening data collected in a recently completed clinical trial, treatment-seeking African American and White daily smokers (10 or more cigarettes per day) were grouped into NMR quartiles so that the races could be compared at the same NMR, even though the distribution of NMR within race differed. The results indicated that rate of nicotine metabolism was a more important factor influencing nicotine intake in White smokers. Specifically, Whites were more likely to titrate their nicotine intake based on the rate at which they metabolize nicotine. However, this relationship was not found in African Americans. Overall there was a greater step-down, linear type relationship between NMR groups and cotinine or cotinine/cigarette in African Americans, which is consistent with the idea that differences in blood cotinine levels between the African American NMR groups were primarily due to differences in CYP2A6 enzyme activity without titration of nicotine intake among faster nicotine metabolizers.

Yb2Ti2O7 is one member of a series of magnetic compounds with the pyrochlore lattice structure. For specific types of single-ion anisotropy and exchange interactions, the geometry of the pyrochlore lattice frustrates near-neighbor interactions and coaxes a wide variety of unusual magnetic ground states from such compounds. Yb2Ti2O7 is unique among these compounds in that the source of the frustration is not immediately obvious when one considers the combination of single-ion anisotropy (XY-like) and the nature of the exchange interactions (ferromagnetic) present therein. A conventional magnetic transition was indeed initially expected based on the observation of specific heat anomaly near 200mK. However, many studies produced no signs of long-range magnetic order below this temperature. Intriguingly, above the transition, evidence for unusual two-dimensional correlations came in the form of rods of magnetic diffuse neutron scattering. This thesis contains four articles that detail the results of several neutron scattering studies on Yb2Ti2O7. The goal of these studies was to determine the nature of the static and dynamic spin correlations throughout the magnetic field vs. temperature phase diagram of Yb2Ti2O7. We first performed a time-of-flight neutron scattering experiment on a single crystal of Yb2Ti2O7, which we prepared using the optical floating zone method. This initial study provided a comprehensive survey of the phase diagram, including the previously unexplored response to a magnetic field. We found that the rods of diffuse scattering change qualitatively upon cooling below the temperature of the reported specific heat anomaly, showing signs for the development of short-range three-dimensional correlations. Additionally, we discovered that a relatively small magnetic field applied along the [110] direction could remove the diffuse scattering entirely, and produce sharp spin wave excitations in the inelastic channel, indicating long range spin cor, Doctor of Philosophy (PhD)