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RISS 인기검색어
- 검색키워드
- 저자 : Ebenstein, Avraham Yehuda (검색결과 2 건)
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Ebenstein, Donna Michelle University of California, Berkeley 2002 해외박사(DDOD)
소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.
Cardiovascular disease is the leading cause of death in the United States. Atherosclerosis is a cardiovascular disease associated with the accumulation of materials such as lipids, calcifications, hematoma, and necrotic debris in the artery wall, resulting in lesions known as plaques. Plaques may cause stenosis, or a narrowing of the blood vessel lumen, and impinge on downstream blood flow. Clinical episodes more commonly result from fracture of plaques and subsequent release of debris which blocks smaller downstream arteries. Lesions with a high propensity for fracture are known as vulnerable plaques. Plaque vulnerability is thought to be highly dependent upon lesion composition and morphology. Accurate assessment of plaque vulnerability also depends on the mechanical properties of the different tissues in the plaque. However, to date there is limited information on the structure-property relations in atherosclerotic plaque tissues. The primary goal of this thesis was therefore to investigate the relationship between mechanical properties and tissue composition in atherosclerotic plaques. Because plaque tissue is very heterogeneous and contains diverse constituents, including lipids, calcifications, and fibrous tissue, a new approach was developed using nanoindentation and Fourier transform infrared spectroscopy (FTIR). Nanoindentation was selected for mechanical property measurements due to its ability to measure local material properties on the nanoscale. Biochemical analysis was performed using FTIR to provide semiquantitative measures of tissue composition (in particular, lipid and calcification content) for correlation to mechanical properties. Using these tools together, relationships were observed between the mechanical properties and the composition of atherosclerotic plaque tissue. In particular, the reduced moduli of the tissue samples were found to increase with increasing calcification content. While FTIR is a well-established technique for analysis of tissue composition, nanoindentation has only recently emerged in the biomaterials community. Numerous studies have been performed in bones and teeth, but limited work has been performed in soft tissues. Reported here are additional nanoindentation studies of a range of biological tissues, including trabecular bone, cartilage, and soft fibrous tissues such as healthy blood vessels and myocardial tissue. These studies provide reference materials for comparison to plaque tissue properties in addition to extending the applications of nanoindentation to soft biological tissues.
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Sex preferences, sex selection, and women's labor supply
Ebenstein, Avraham Yehuda University of California, Berkeley 2007 해외박사(DDOD)
소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.
This dissertation consists of two essays. In the first essay, I investigate the causes for high sex ratios in China and India that have historically concerned researchers (Sen 1990). I identify sex selection via infanticide and abortion as the principal explanation for the sex ratio distortion, and rule out competing explanations such as biology (Oster 2005) or differential mortality rates. Consistent with recent work (Jha et al. 2006), I find that the sex ratio of first-order births is close to the natural rate and steeply rising following the birth of low-order daughters, indicating that mothers are practicing pre-natal sex selection or immediate infanticide. Sex ratios are found to be higher among those anticipating lower fertility, such as those under stricter government fertility limits. I present a model of a mother's fertility choice when she has access to a sex-selection technology and faces a mandated fertility limit. By exploiting variation in fines levied in China for unsanctioned births, I demonstrate that higher fine regimes discourage fertility but are associated with higher sex ratios among those who choose to have an additional child. I then estimate a structural model of parental preferences using China's 2000 census data that indicates that a son is worth 2.90 years of income more than a daughter, and the premium is highest among less educated mothers and rural families. I conclude with a set of simulations to model the effect on sex ratios and total fertility of a proposed subsidy to families who fail to have a son, and find that such a policy would reduce sex ratios and lower overall fertility. The second essay attempts to identify the causal link between fertility and the labor supply of married women. Economic models of home production predict a tradeoff between family size and child outcomes, as well as a tradeoff between a mother's fertility and her labor supply. Recent empirical work suggests that while family size and these outcomes are correlated, the causal impact is negligible when estimated through Instrumental Variables (sex preference, twinning). I find that in Taiwan, intense son preference produces 2SLS estimates of a mother's labor response that are larger than OLS estimates, suggesting that previous IV analyses may rely on instruments too weak for consistent estimation. My estimates indicate that for mothers in Taiwan, a child induced by sex preferences imposes a cost of roughly one year of foregone labor supply, with estimates slightly larger for better educated mothers. The analysis also identifies fertility timing as a key predictor of female labor supply, indicating that IV estimates using twin-births may understate the impact of an additional pregnancy and birth on a mother's labor force experience. I present a model of a mother's joint determination of fertility and labor supply that suggests the estimated Local Average Treatment Effect will rise in proportion to the intensity of sex preferences. Consistent with the model's predictions, I find that in Taiwan, the extra birth induced by sex preferences causes a shift in the family's consumption mix towards inferior goods and away from normal goods, but no such effect is found among American families. My results indicate that IV estimates using twinning or weak sex preferences may understate the true cost of childbearing on family outcomes.
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