Browsing by Author "Huang, Y"

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Open Access
A Hybrid Global-local Numerical Method for Multiscale PDEs
(2017-04-23) Huang, Y; Lu, Jianfeng; Ming, P
We present a new hybrid numerical method for multiscale partial differential equations, which simultaneously captures both the global macroscopic information and resolves the local microscopic events. The convergence of the proposed method is proved for problems with bounded and measurable coefficient, while the rate of convergence is established for problems with rapidly oscillating periodic or almost-periodic coefficients. Numerical results are reported to show the efficiency and accuracy of the proposed method.
Open Access
Epithelial injury and interstitial fibrosis in the proximal alveolar regions of rats chronically exposed to a simulated pattern of urban ambient ozone.
(Toxicology and applied pharmacology, 1992-08) Chang, LY; Huang, Y; Stockstill, BL; Graham, JA; Grose, EC; Menache, MG; Miller, FJ; Costa, DL; Crapo, JD
Electron microscopic morphometry was used to study the development of lung injury during and after chronic (78 weeks) exposure to a pattern of ozone (O3) designed to simulate high urban ambient concentrations that occur in some environments. The daily exposure regimen consisted of a 13-hr background of 0.06 ppm, an exposure peak that rose from 0.06 to 0.25 ppm, and returned to the background level over a 9-hr period, and 2-hr downtime for maintenance. Rats were exposed for 1, 3, 13, and 78 weeks. Additional groups of rats exposed for 13 or 78 weeks were allowed to recover in filtered clean air for 6 or 17 weeks, respectively. Rats exposed to filtered air for the same lengths of time were used as controls. Samples from proximal alveolar regions and terminal bronchioles were obtained by microdissection. Analysis of the proximal alveolar region revealed a biphasic response. Acute tissue reactions after 1 week of exposure included epithelial inflammation, interstitial edema, interstitial cell hypertrophy, and influx of macrophages. These responses subsided after 3 weeks of exposure. Progressive epithelial and interstitial tissue responses developed with prolonged exposure and included epithelial hyperplasia, fibroblast proliferation, and interstitial matrix accumulation. The epithelial responses involved both type I and type II epithelial cells. Alveolar type I cells increased in number, became thicker, and covered a smaller average surface area. These changes persisted throughout the entire exposure and did not change during the recovery period, indicating the sensitivity of these cells to injury. The main response of type II epithelial cells was cell proliferation. The accumulation of interstitial matrix after chronic exposure consisted of deposition of both increased amounts of basement membrane and collagen fibers. Interstitial matrix accumulation underwent partial recovery during follow-up periods in air; however, the thickening of the basement membrane did not resolve. Analysis of terminal bronchioles showed that short-term exposure to O3 caused a loss of ciliated cells and differentiation of preciliated and Clara cells. The bronchiolar cell population stabilized on continued exposure; however, chronic exposure resulted in structural changes, suggesting injury to both ciliated and Clara cells. We conclude that chronic exposure to low levels of O3 causes epithelial inflammation and interstitial fibrosis in the proximal alveolar region and bronchiolar epithelial cell injury.
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Low temperature amorphization and superconductivity in FeSe single crystals at high pressures
(2010) Stemshorn, AK; Tsoi, G; Vohra, YK; Sinogeiken, S; Wu, PM; Huang, Y; Rao, SM; Wu, MK; Yen, KW; Weir, ST
In this study, we report low temperature x-ray diffraction studies combined with electrical resistance measurements on single crystals of iron-based layered superconductor FeSe to a temperature of 10 K and a pressure of 44 GPa. The low temperature high pressure x-ray diffraction studies were performed using a synchrotron source and superconductivity at high pressure was studied using designer diamond anvils. At ambient temperature, the FeSe sample shows a phase transformation from a PbO-type tetragonal phase to a NiAs-type hexagonal phase at 10 +/- 2 GPa. On cooling, a structural distortion from a PbO-type tetragonal phase to an orthorhombic Cmma phase is observed below 100 K. At a low temperature of 10 K, compression of the orthorhombic Cmma phase results in a gradual transformation to an amorphous phase above 15 GPa. The transformation to the amorphous phase is completed by 40 GPa at 10 K. A loss of superconductivity is observed in the amorphous phase and a dramatic change in the temperature behavior of electrical resistance indicates formation of a semiconducting state at high pressures and low temperatures. The formation of the amorphous phase is attributed to a kinetic hindrance to the growth of a hexagonal NiAs phase under high pressures and low temperatures.
Open Access
The scale of population structure in Arabidopsis thaliana.
(PLoS Genet, 2010-02-12) Platt, A; Horton, M; Huang, Y; Li, Y; Anastasio, A; Mulyati, W; Agren, J; Bossdorf, O; Byers, D; Donohue, K; Dunning, M; Holub, E; Hudson, A; Le Corre, V; Loudet, O; Rivero, L; Scholl, R; Nordborg, M; Bergelson, J; Borevitz, JO
The population structure of an organism reflects its evolutionary history and influences its evolutionary trajectory. It constrains the combination of genetic diversity and reveals patterns of past gene flow. Understanding it is a prerequisite for detecting genomic regions under selection, predicting the effect of population disturbances, or modeling gene flow. This paper examines the detailed global population structure of Arabidopsis thaliana. Using a set of 5,707 plants collected from around the globe and genotyped at 149 SNPs, we show that while A. thaliana as a species self-fertilizes 97% of the time, there is considerable variation among local groups. This level of outcrossing greatly limits observed heterozygosity but is sufficient to generate considerable local haplotypic diversity. We also find that in its native Eurasian range A. thaliana exhibits continuous isolation by distance at every geographic scale without natural breaks corresponding to classical notions of populations. By contrast, in North America, where it exists as an exotic species, A. thaliana exhibits little or no population structure at a continental scale but local isolation by distance that extends hundreds of km. This suggests a pattern for the development of isolation by distance that can establish itself shortly after an organism fills a new habitat range. It also raises questions about the general applicability of many standard population genetics models. Any model based on discrete clusters of interchangeable individuals will be an uneasy fit to organisms like A. thaliana which exhibit continuous isolation by distance on many scales.