764 research outputs found

    Biomarker-Based Characterization of Chemical Exposures and Physiological Responses

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    The chemisome is the chemical components of the exposome, defined as the totality of all exposures and their impact on health. Most current approaches, however, are limited in addressing this “totality” by only studying one chemical or one chemical family at a time in one exposed population. In addition, studying the links between chemical exposures and health is challenging due to an incomplete understanding of how physiological responses are associated with adverse health outcomes. This challenge is further complicated due to how chemical exposures change with demographics such as age, sex, race, and occupation. Thus, this dissertation aims to address these challenges by applying an unbiased approach to datasets of chemical biomarker levels and physiological measurements to systematically identify susceptible populations using the National Health and Nutrition Examination Survey. In the first project, I use quadratic regression models to characterize non-linear, age-based trends of chemical exposure in a sample comprised of 74,942 participants. I screen across 141 chemicals to identify those of higher concentrations in children relative to the older population. Children exhibit higher exposures to chemicals in consumer products such as phthalates, brominated flame retardants, lead, and tungsten. In contrast, restricted and highly persistent chemicals such as polychlorinated biphenyls and dioxins are higher in the older population. In the second project, I apply generalized linear models to evaluate exposure disparities by race/ethnicity for 143 chemicals in a representative sample of 38,080 US women. Compared to non-Hispanic White women, significant disparities are observed for non-Hispanic Black, Mexican American, Other Hispanic, and Other Race/Multi-Racial women. These women have higher levels of pesticides, including 2,5-dichlorophenol and 2,4-dichlorophenol, compounds in personal care products, including parabens and mono-ethyl phthalate, and heavy metals, such as mercury and arsenic. These findings are being coupled with toxicological data to prioritize chemicals to evaluate their role in health disparities. In the third project, I develop a framework using hierarchical clustering to characterize occupational exposures and physiological responses among 26,186 blue- and white-collar workers across 20 employment sectors for 108 chemicals and 27 physiological indicators. Blue-collar workers have higher levels of toxicants such as lead, cadmium, volatile organic chemicals, and polycyclic aromatic hydrocarbons compared to white-collar workers. Moreover, blue-collar workers exhibit higher levels of alkaline phosphatase (indicative of liver disease) and C-reactive proteins (indicative of inflammation). Together, these results suggest that blue-collar workers are exposed to higher levels of toxicants, which may induce physiological dysfunction. In the final project, I implement 10-fold cross-validated regression models to characterize the linear and non-linear associations between all-cause mortality and 27 physiological indicators to identify directionalities indicative of increased mortality risk in a sample of 45,032 participants. Twenty-four out of 27 indicators show non-linear associations, while height, triglycerides, and 60-second pulse show linear associations. Cholesterol-related indicators and glomerular filtration rate unexpectedly show parabolic associations, implying that higher mortality risk is associated with measurements in either extreme of the distribution instead of in one extreme. These findings highlight a need to study associations between these indicators and other health endpoints to gain insights into the physiological profiles associated with adverse health outcomes. Together, this thesis contributes to a better understanding of how chemical exposures can impact human health across multiple subpopulations. It also enables further exploration of how chemical exposures can perturb physiologic function conducive to increasing the risk for adverse health outcomes.PHDBioinformaticsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/162947/1/nguyenvy_1.pd

    Addictions, Behavioral Addictions, and Pathological Internet Use as Internet Addiction - A Literature Review

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    Excessive and pathological uses of the Internet are observed and discussed often in our modern conversations. Access to the Internet has become so convenient that these behaviors can lead to consequences in many areas of our lives from social relationships to academic and professional work performance. A common term that people use to address this pattern of behaviors is “Internet Addiction” or more specific ones, such as “Social Media Addiction” or “Online Gaming Addiction.” However, in clinical psychology, addiction has its own specific definitions. It refers to a category and set of criteria that are distinguished from other mental disorders in terms of symptoms, neurobiological processes, and treatment. Excessive use of the Internet per se is not enough to be addressed as an addiction. This literature review aims to present the established features of addiction from a behavioral level to a neurobiological level and compare them to the phenomenon of excessive and pathological Internet use. The goal is to explain why or why we should address not the problems of excessive and pathological Internet use as an addiction. For our purpose, the term “pathological Internet use” will be used in this literature review to indicate all the excessive and pathological Internet-related activities that are considered for the addiction model. After examining research on this subject, it is clear that excessive and pathological use of the Internet does share similar pattern of behavioral symptoms with typical drug addictions and gambling addiction. On the neuro-biological level, existing findings show relevant changes in a reward circuit that are responsible for addiction processes in the brain. However, more studies on the neuro-biological process are still needed to establish the enough evidence or addiction model to be applicable to pathological Internet use so that proper treatment can follow

    Urban Segregation

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    Re-Assessment of Sargassum Beds at Hon Chong Area, Nha Trang Bay, Vietnam

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    Sargassum beds play an important role in terms of ecology and economic likelihood ("ecosystem services") for coastal communities along the Hon Chong area, in the bay of Nha Trang, Vietnam. It is a matter of concern that the Sargassum beds at Hon Chong, in particular, and Vietnam, in general, have strongly decreased due to anthropogenic perturbations including land reclamation. Our research focused on a reassessment of Sargassum beds including coverage, occupied area, species composition, branch length frequencies and output (production) over the last 30 years. Remotely-obtained (satellite) information and field data processed through GIS software were used during this study. Results show that the area covered by the Sargassum beds was reduced by 49%. In 1980 the coverage of Sargassum was 75% for all the area (30 ha), but now we observed that 75% of the coverage occurred in area of only 2.2 ha. The average length of Sargassum mcclurei and S. serratum branches recorded in 2009 were reduced by 58% and 65%, respectively, compared with data recorded in 1980. Moreover, in 1980 Sargassum crassifolium was very common in this area, however, during this study it was not found

    Synthesis and characterization of polyimide membrane for carbon dioxide removal prepared by dry-wet phase inversion method

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    Currently, membrane is a separation process that is gaining lots of attention in the industry, especially membranes for gas separation processes such as removal of carbon dioxide from natural gas. Among the available materials for these membranes, cellulose acetate has always been used as the conventional membrane polymer. In this paper, the focus was on polyimide, which was proposed to be the new alternative for cellulose acetate with certain distinguished advantages. As polyimide membrane is still a new material for membrane, this study focused on the detailed synthesis procedure of a flat sheet polyimide membrane through dry-wet phase inversion method. The chosen polymer was BTDA/ODA (Biphenyl Tetracarboxylic Dianhydride/ Oleoyl Diamine), along with DMF (Dimethyl Formamide) as solvent and a mixture of water/ethanol as non-solvents in coagulation bath. An addition of binder to the synthesis procedure was also tested in this paper. Characteristic tests were conducted to study about the morphology as well as the porosity of the membrane synthesis. In addition, some variations on membrane composition were conducted to study about the effect of polymer concentration, coagulation bath composition and binder addition on polyimide membrane. Lastly, a process optimization was done to choose the most suitable conditions and composition for the membrane synthesis
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