Browsing by Author "Liu, Dawei"

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    Improvement and use of radiative transfer models to assess lunar space weathering and mechanisms for swirl formation
    (2015-06-15) Liu, Dawei; Li, Lin; Jacinthe, Pierre-André; Wang, Lixin; Cheng, Ruihua; Johnson, Daniel
    This dissertation focuses on quantification of submicroscopic iron of different sizes, mineral abundance and grain size of lunar soils using Hapke's radiative transfer model. The main objective is to explore implications of these results for assessing the relative importance of solar wind implantation versus micrometeorite impacts for lunar space weathering as well as three hypotheses (solar wind deflection, comet impact and dust transport) for swirl formation on the Moon. Results from this study can help to make connections between ordinary chondritic meteorites and asteroids, and put physical and chemical constraints on heating processes in the early solar system.
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    Motor onset and diagnosis in Huntington disease using the diagnostic confidence level
    (Springer, 2015-12) Liu, Dawei; Long, Jeffrey D.; Zhang, Ying; Raymond, Lynn A.; Marder, Karen; Rosser, Anne; McCusker, Elizabeth A.; Mills, James A.; Paulsen, Jane S.; Department of Biostatistics, Richard M. Fairbanks School of Public Health
    Huntington disease (HD) is a neurodegenerative disorder characterized by motor dysfunction, cognitive deterioration, and psychiatric symptoms, with progressive motor impairments being a prominent feature. The primary objectives of this study are to delineate the disease course of motor function in HD, to provide estimates of the onset of motor impairments and motor diagnosis, and to examine the effects of genetic and demographic variables on the progression of motor impairments. Data from an international multisite, longitudinal observational study of 905 prodromal HD participants with cytosine-adenine-guanine (CAG) repeats of at least 36 and with at least two visits during the followup period from 2001 to 2012 was examined for changes in the diagnostic confidence level from the Unified Huntington's Disease Rating Scale. HD progression from unimpaired to impaired motor function, as well as the progression from motor impairment to diagnosis, was associated with the linear effect of age and CAG repeat length. Specifically, for every 1-year increase in age, the risk of transition in diagnostic confidence level increased by 11% (95% CI 7-15%) and for one repeat length increase in CAG, the risk of transition in diagnostic confidence level increased by 47% (95% CI 27-69%). Findings show that CAG repeat length and age increased the likelihood of the first onset of motor impairment as well as the age at diagnosis. Results suggest that more accurate estimates of HD onset age can be obtained by incorporating the current status of diagnostic confidence level into predictive models.