Browsing by Author "Chen, Wei"
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- Epidemiological characteristics and burden of childhood and adolescent injuries: a survey of elementary and secondary students in Xiamen, ChinaFang, Ya; Zhang, Xiang; Chen, Wei; Lin, Fang; Yuan, Manqiong; Geng, Zhi; Yu, Hong; Dai, Long (2015-04-10)Background Injuries pose a considerable threat to the health of children and adolescents, and childhood injuries cause substantial economic loss for families and society. Many injuries are preventable. To provide a theoretical basis and empirical support for injury prevention interventions, we studied the epidemiological characteristics, risk factors, and burden of injuries among elementary and secondary school students in Xiamen, China. Methods Participants were enrolled through multi-stage stratified cluster random sampling of elementary and secondary students in Xiamen in 2010. Questionnaires were completed by students’ parents or guardians to assay students’ basic information, family background, occurrence of injuries in the past year, and burden of injuries. Chi-square tests and logistic regression were performed to identify the key factors of injuries. Results A total of 2,816 usable questionnaires reported 365 injury incidents in 303 students over 1 year. The incidence of injuries was 10.8%. Students who were male, extroverted, suburban, had sibling(s), studied in grades 4–9, or whose parents were divorced or separated were more likely to suffer from injuries. Most injuries occurred during the summer months (from June to August), and in the afternoon. The main affected body parts were limbs, fingers or toes. Unintentional falls, collisions/strikes, sprains, and cuts/sharp instrument injuries were the predominant causes of injury. The overall economic burden of the 365 injury incidents was 1,014,649.1 RMB (148,666.5 USD) total, 3,348.7 RMB (490.65 USD) per capita, and 2,779.9 RMB (407.31 USD) per incident. Conclusion The injury incidence among elementary and secondary students in Xiamen, China is lower than Guangdong and Zhejiang but higher than Beijing and Shanghai. Injuries caused substantial economic and family burdens and threatened students’ health and life. Childhood and adolescent injuries have become a serious public health problem that requires the urgent attention of the government, society, schools, and families. Injury control and prevention among elementary and secondary school students is essential and will help in multiple ways to reduce the burden on the family to build a harmonious family and society.
- Identification and analysis of the N-6-methyladenosine in the Saccharomyces cerevisiae transcriptomeChen, Wei; Tran, Hong T.; Liang, Zhiyong; Lin, Hao; Zhang, Liqing (Springer Nature, 2015-09-07)Knowledge of the distribution of N-6-methyladenosine (m(6)A) is invaluable for understanding RNA biological functions. However, limitation in experimental methods impedes the progress towards the identification of m(6)A site. As a complement of experimental methods, a support vector machine based-method is proposed to identify m(6)A sites in Saccharomyces cerevisiae genome. In this model, RNA sequences are encoded by their nucleotide chemical property and accumulated nucleotide frequency information. It is observed in the jackknife test that the accuracy achieved by the proposed model in identifying the m(6)A site was 78.15%. For the convenience of experimental scientists, a webserver for the proposed model is provided at http://lin.uestc.edu.cn/server/m6Apred.php.
- An improved electronic ballast for the fluorescent lampsChen, Wei (Virginia Tech, 1995-08-09)The ''charge pump" electronic ballast circuit, which employs a charging capacitor and a high frequency ac source to implement the power factor correction (PFC), has become an attractive topology for ballasting the fluorescent lamps because it eliminates the use of a bulky boost inductor. But the high voltage stress on the semiconductor devices at light load conditions, the high total harmonic distortion (THO) of the line current, and the poor crest factor ( CF) of the lamp current in this circuit make it difficult to manufacture this circuit into a cost-effective ballast product. This thesis analyzes the problems associated with the "charge pump" electronic ballast, and proposes several innovative methods to solve the problems, resulting in a high performance and cost-effective technology.
- Low Voltage High Current Power Conversion with Integrated MagneticsChen, Wei (Virginia Tech, 1998-04-27)Very low voltage, high current output requirement have necessitated improvements in power supply's density and efficiency. Existing power conversion techniques cannot meet very stringent size and efficiency requirements. By applying the proposed magnetic integration procedure, new integrated magnetic circuits featuring low loss, simple structure, and ripple cancellation technique are then developed to overcome the limitations of prior art. Both cores and windings are integrated. Consequently, the power loss and the size of the integrated magnetic device are greatly reduced. Detailed analysis and design considerations of the proposed circuits are presented. As a result of applying the proposed technique, very high density, high efficiency, low voltage, high current power modules were developed. A typical example features an isolated 3.3V/30A power module with a power density of 130W/in3 and an efficiency of 90% at 500 KHz switching frequency.
- The pattern of DNA cleavage intensity around indelsChen, Wei; Zhang, Liqing (Springer Nature, 2015-02-09)Indels (insertions and deletions) are the second most common form of genetic variations in the eukaryotic genomes and are responsible for a multitude of genetic diseases. Despite its significance, detailed molecular mechanisms for indel generation are still unclear. Here we examined 2,656,597 small human and mouse germline indels, 16,742 human somatic indels, 10,599 large human insertions, and 5,822 large chimpanzee insertions and systematically analyzed the patterns of DNA cleavage intensities in the 200 base pair regions surrounding these indels. Our results show that DNA cleavage intensities close to the start and end points of indels are significantly lower than other regions, for both small human germline and somatic indels and also for mouse small indels. Compared to small indels, the patterns of DNA cleavage intensity around large indels are more complex, and there are two low intensity regions near each end of the indels that are approximately 13 bp apart from each other. Detailed analyses of a subset of indels show that there is slight difference in cleavage intensity distribution between insertion indels and deletion indels that could be contributed by their respective enrichment of different repetitive elements. These results will provide new insight into indel generation mechanisms.
- Peptidylarginine deiminase 2-catalyzed histone H3 arginine 26 citrullination facilitates estrogen receptor alpha target gene activationZhang, Xuesen; Bolt, Michael; Guertin, Michael J.; Chen, Wei; Zhang, Sheng; Cherrington, Brian D.; Slade, Daniel J.; Dreyton, Christina J.; Subramanian, Venkataraman; Bicker, Kevin L.; Thompson, Paul R.; Mancini, Michael A.; Lis, John T.; Coonrod, Scott A. (2012-08-14)Cofactors for estrogen receptor α (ERα) can modulate gene activity by posttranslationally modifying histone tails at target promoters. Here, we found that stimulation of ERα-positive cells with 17β-estradiol (E2) promotes global citrullination of histone H3 arginine 26 (H3R26) on chromatin. Additionally, we found that the H3 citrulline 26 (H3Cit26) modification colocalizes with ERα at decondensed chromatin loci surrounding the estrogen-response elements of target promoters. Surprisingly, we also found that citrullination of H3R26 is catalyzed by peptidylarginine deiminase (PAD) 2 and not by PAD4 (which citrullinates H4R3). Further, we showed that PAD2 interacts with ERα after E2 stimulation and that inhibition of either PAD2 or ERα strongly suppresses E2-induced H3R26 citrullination and ERα recruitment at target gene promoters. Collectively, our data suggest that E2 stimulation induces the recruitment of PAD2 to target promoters by ERα, whereby PAD2 then citrullinates H3R26, which leads to local chromatin decondensation and transcriptional activation.
- Quantitative Genetic Background of the Host Influences Gut Microbiomes in ChickensZhao, Lele; Wang, Gang; Siegel, Paul B.; He, Chuan; Wang, Hezhong; Zhao, Wenjing; Zhai, Zhengxiao; Tian, Fengwei; Zhao, Jianxin; Zhang, Hao; Sun, Zikui; Chen, Wei; Zhang, Yan; Meng, He (Nature Publishing Group, 2013-01)Host genotype and gender are among the factors that influence the composition of gut microbiota. We studied the population structure of gut microbiota in two lines of chickens maintained under the same husbandry and dietary regimes. The lines, which originated from a common founder population, had undergone 54 generations of selection for high (HW) or low (LW) 56-day body weight, and now differ by more than 10-fold in body weight at selection age. Of 190 microbiome species, 68 were affected by genotype (line), gender, and genotype by gender interactions. Fifteen of the 68 species belong to Lactobacillus. Species affected by genotype, gender, and the genotype by gender interaction, were 29, 48, and 12, respectively. Species affected by gender were 30 and 17 in the HW and LW lines, respectively. Thus, under a common diet and husbandry host quantitative genotype and gender influenced gut microbiota composite.
- Three Essays on Price Analysis of Summer Flounder and China's Soybean ImportsChen, Wei (Virginia Tech, 2009-07-09)This dissertation contains three papers from two projects. The first two papers (Chapter Two and Chapter Three) are from a project entitled “Managing Flounder Openings for Maximum Revenue.” The objective of this project is to (1) estimate the monthly dockside price of summer flounder and identify seasonality in this price; and (2) set up a mathematical programming model to maximize the landing revenue by allocating the federal government quota on summer flounder across twelve months. In the first paper (Chapter Two), various forms of inverse demand equations are used to estimate the dockside price of summer flounder. These models are evaluated based on their out-of-sample forecasting performance. A structural functional form is selected. In the second paper (Chapter Three), the selected price equation for summer flounder is applied into a revenue maximization model with both the federal government quota constraint and biological constraints from twelve months. The model is solved using CONPOT Solver of GAMS 21.5. The results of the scenarios indicate that the industry should move the landing effort from the period of October – February to the period of March – August. Comparing with historical data, this method can increase $44.73 million for the industry of landing summer flounder from 1991 to 2005. The third paper (Chapter Four) investigates how China's soybean import prices and domestic prices of soybeans and soybean products affect China's soybean imports. Since 2000, soybeans have been the U.S. leading agricultural exports for bulk commodities. China is the largest importer of U.S. soybean exports. For China's soybean crushing industry, imported soybeans are inputs rather than final products and used to produce soybean meal and oil. A differential production model, which is derived from a two-stage profit maximization model in producer theory, is adopted in this research. Estimates are used to calculate conditional and unconditional price elasticities for China's soybean imports from its major source countries – the United States, Argentina, and Brazil. In addition, the Divisia index and unconditional output price elasticities are obtained for China's soybean imports. Estimation results support the hypothesis that China's soybean imports are determined by its domestic demand for soybean meal, rather than soybean oil. This implies that U.S. agribusinesses should pay attention to the dominant role of China's demand for soybean meal and animal feed. U.S. agribusinesses can also use results in this research to evaluate how China's soybean imports from different source countries will change when either international market prices or China's domestic market prices change.