Browsing by Author "Vo, Tien"
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Item Parker spirals - A Study on the Structure of the Interplanetary Magnetic Field(2018-08) Vo, TienThe Parker spiral’s accuracy is investigated through its prediction for the angle of the interplanetary magnetic field observed by satellites near 1 AU. Simulations were run using simple solar wind parameters and results were compared with measured data from STEREO A and B. Several distribution plots are made to numerically analyze the prediction quality over a six-year period. Investigation was focused on the difference between prediction quality in the ecliptic plane and in three-dimensional space. This paper is a result of a preliminary analysis on a program written to investigate the Parker spirals. The program, a deployable Python flask application, is a major part of the URS project and is subject to further improvements as this project will continue to be carried on. The next steps will be to analyze solar energetic events using the Parker spiral in conjunction with other instruments. Additionally, this model will be compared with other existing, more complicated models for the interplanetary magnetic field to yield meaningful comparisons for the accuracy in predicting the magnetic field structure.Item Sleep Problems in Community-dwelling Older Adults in the United States(2021-07) Vo, TienSleep-disordered breathing (SDB) or sleep apnea, a common disorder, is characterized by repeated pauses or reductions in breathing during sleep. A number of studies, primarily in younger or middle-aged populations, have evaluated the association of SDB and healthcare utilization. However, previous studies were limited by use of cross-sectional or case-control study designs and inadequate control of potential confounders. Sleep efficiency, defined as the percentage of time in bed spent sleeping, is a key measure of sleep health and has been shown to decrease with advancing age along with total sleep time, another important sleep parameter, defined as total hours per night spent sleeping while in bed.While some studies have examined sleep efficiency as a predictor of adverse health outcomes and conditions, there is a paucity of research that has considered sleep efficiency as an outcome measure. To address current gaps in research presented above, the goals of the proposed study are to achieve the following expected outcomes: First, we will estimate the prevalence of sleep-disordered breathing and determine the association of SDB with subsequent measures of health care utilization and costs in U.S. community-dwelling older men. The findings will provide a clearer understanding of the impact of sleep-disordered breathing on healthcare costs and inpatient and post-acute care utilization, and possibly warrant future intervention studies that would have public health impact to determine whether treatment of sleep-disordered breathing lowers these measures of healthcare burden. Second, using standard logistic regression, we will examine and identify factors that are associated with incident reduced sleep efficiency in U.S. older community-dwelling men and women. The findings will provide insights on potential modifiable predictors of incident reduced sleep efficiency and guide design of future intervention studies. Third, we will use machine-learning methods through random forests to identify factors of importance in explaining incident reduced sleep efficiency in U.S. older community-dwelling men and women. Ultimately, this research proposal will improve our understanding of the determinants of the development of incident reduced sleep efficiency in older men and women, and quantify the impact of sleep-disordered breathing on total healthcare costs and utilization in older men.