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Search Results: 1 - 10 of 78350 matches for " Xianming Chen "
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Review Article: High-Temperature Adult-Plant Resistance, Key for Sustainable Control of Stripe Rust  [PDF]
Xianming Chen
American Journal of Plant Sciences (AJPS) , 2013, DOI: 10.4236/ajps.2013.43080
Abstract:

High-temperature adult-plant (HTAP) resistance expresses when plants grow old and the weather becomes warm. This non-race specific and durable type of resistance has been used successfully in control of wheat stripe rust in the US since early 1960s. This article describes practical procedures for identification and characterization of HTAP resistance and reviews recent studies on discovery of genes conferring HTAP resistance. Recent studies providing insights to the molecular basis for the durability of HTAP resistance will be presented. Strategies for improving levels of HTAP resistance and improving control of stripe rust through combining HTAP resistance with effective all-stage resistance will be discussed.

Inference for Multivariate Normal Mixtures
Jiahua Chen,Xianming Tan
Mathematics , 2008,
Abstract: Multivariate normal mixtures provide a flexible model for high-dimensional data. They are widely used in statistical genetics, statistical finance, and other disciplines. Due to the unboundedness of the likelihood function, classical likelihood-based methods, which may have nice practical properties, are inconsistent. In this paper, we recommend a penalized likelihood method for estimating the mixing distribution. We show that the maximum penalized likelihood estimator is strongly consistent when the number of components has a known upper bound. We also explore a convenient EM-algorithm for computing the maximum penalized likelihood estimator. Extensive simulations are conducted to explore the effectiveness and the practical limitations of both the new method and the ratified maximum likelihood estimators. Guidelines are provided based on the simulation results.
Warrant Price Range Adjustment Based on Investor Sentiment  [PDF]
Xianming Fang
Journal of Service Science and Management (JSSM) , 2010, DOI: 10.4236/jssm.2010.34055
Abstract: The warrant price fluctuated in a range based on the arbitrage-free hypothesis. However, in the actual transaction, the warrant price will deviate the price range because of the investor sentiment, sometimes the deviation is too far that the actual price breaks the lower limit based on the arbitrage-free hypothesis, which make the market some arbitrage opportunities. The buyers’ strength and the sellers’ strength are the concentrated expression of the investor sentiment. According to the buyers’ strength and the sellers’ strength, a warrant price modification factor has been built with investor sentiment by function transformation. The new function adjusts the theoretical price range and identifies the arbitrage opportunities of the warrant market. The empirical test on Baotou Steel warrants shows that, after the adjustment, only a few the actual price deviates from the adjustment price range and the correction is better. So, when the warrant price trend is analyzed, the impact of the investor sentiment should be taken into account.
The Influence of Macroeconomic Environment on Australian Household Debt: An Application of Dynamic OLS  [PDF]
Xianming Meng
Open Journal of Social Sciences (JSS) , 2016, DOI: 10.4236/jss.2016.411001
Abstract:
Concerns about household debt increase with the escalating debt level in developed countries. Australia is a good example of this. This paper applies the dynamic ordinary least square (DOLS) method to explore the determinants and influences of Australian household debt. The results show that the rising Australian household debt results from the increased size of the economy, a booming housing market, a favourable macroeconomic environment and favourable government policies. Although the rising house-hold debt stimulates economic growth in the short run, it may induce economic instability in the long run.
Nipple-Areola Sparing Mastectomy Followed by Immediate Breast Reconstruction in 126 Patients  [PDF]
Xianming Wang, Min Wang, Jinkun Liu, Weicai Chen, Huisheng Wu, Shufeng Song
Journal of Cancer Therapy (JCT) , 2012, DOI: 10.4236/jct.2012.325105
Abstract: This study is to explore the indications, procedures, effectiveness, and feasibility of nipple-areola sparing mastectomy followed by immediate breast reconstruction. The nipple-areola sparing mastectomy followed by immediate breast reconstruction was performed in 126 patients with breast cancer from June 2005 to October 2011. The cosmetic outcomes of the reconstructed breasts were evaluated according to objective and subjective criteria. Meanwhile, the postoperative complications were observed and the therapeutic efficacies were followed up. All the operations were successful. Six patients experienced mild complications early after surgery and were resolved after symptomatic treatment. Both the subjective and objective evaluation for the aesthetic outcomes yielded a satisfactory rate of 97.62% during the 6-80-month follow-up. No recurrence or metastasis was found in 118 cases. Nipple-areola sparing mastectomy followed by immediate breast reconstruction is a simple and effective option for significantly improving the cosmetic outcomes and quality of life of patients, without serious complications or impact on the comprehensive treatment and long-term effect against breast cancer.
Evaluation of Pakistan wheat germplasms for stripe rust resistance using molecular markers
Tabassum Sobia,Ashraf Muhammad,XianMing Chen
Science China Life Sciences , 2010, DOI: 10.1007/s11427-010-4052-y
Abstract: Wheat production in Pakistan is seriously constrained due to rust diseases and stripe rust (yellow) caused by Puccinia striiformis f. sp. tritici, which could limit yields. Thus development and cultivation of genetically diverse and resistant varieties is the most sustainable solution to overcome these diseases. The first objective of the present study was to evaluate 100 Pakistan wheat cultivars that have been grown over the past 60 years. These cultivars were inoculated at the seedling stage with two virulent stripe rust isolates from the United States and two from Pakistan. None of the wheat cultivars were resistant to all tested stripe rust isolates, and 16% of cultivars were susceptible to the four isolates at the seedling stage. The data indicated that none of the Pakistan wheat cultivars contained either Yr5 or Yr15 genes that were considered to be effective against most P. striiformis f. sp. tritici isolates from around the world. Several Pakistan wheat cultivars may have gene Yr10, which is effective against isolate PST-127 but ineffective against PST-116. It is also possible that these cultivars may have other previously unidentified genes or gene combinations. The second objective was to evaluate the 100 Pakistan wheat cultivars for stripe rust resistance during natural epidemics in Pakistan and Washington State, USA. It was found that a higher frequency of resistance was present under field conditions compared with greenhouse conditions. Thirty genotypes (30% of germplasms) were found to have a potentially high temperature adult plant (HTAP) resistance. The third objective was to determine the genetic diversity in Pakistan wheat germplasms using molecular markers. This study was based on DNA fingerprinting using resistance gene analog polymorphism (RGAP) marker analysis. The highest polymorphism detected with RGAP primer pairs was 40%, 50% and 57% with a mean polymorphism of 36%. A total of 22 RGAP markers were obtained in this study. RGAP, simple sequence repeat (SSR) and sequence tagged site (STS) markers were used to determine the presence and absence of some important stripe rust resistance genes, such as Yr5, Yr8, Yr9, Yr15 and Yr18. Of the 60 cultivars analyzed, 17% of cultivars showed a RGAP marker band for Yr9 and 12% of cultivars exhibited the Yr18 marker band. No marker band was detected for Yr5, Yr8 and Yr15, indicating a likely absence of these genes in the tested Pakistan wheat cultivars. Cluster analysis based on molecular and stripe rust reaction data is useful in identifying considerable genetic diversity among Pakistan wheat cultivars. The resistant germplasms identified with 22 RGAP markers and from the resistance evaluations should be useful in developing new wheat cultivars with stripe rust resistance.
Association Analysis of SP-SNPs and Avirulence Genes in Puccinia striiformis f. sp. tritici, the Wheat Stripe Rust Pathogen  [PDF]
Chongjing Xia, Meinan Wang, Anmin Wan, Derick A. Jiwan, Deven R. See, Xianming Chen
American Journal of Plant Sciences (AJPS) , 2016, DOI: 10.4236/ajps.2016.71014
Abstract: Puccinia striiformis f. sp. tritici (Pst) is one of the pathogenic fungi on wheat, caused stripe rust that is a great threat for wheat production all over the world. Intensive efforts have been made to study genetics of wheat resistance to this disease, but few on avirulence of the pathogen due mainly to the nature of obligate biotrophism and the lack of systems for studying its genetics and molecular manipulations. To overcome these limitations, a natural Pst population comprising 352 isolates representative of a diverse virulence spectrum was genotyped using 97 secreted protein-single nucleotide polymorphism (SP-SNP) markers to identify candidate avirulence genes using association analysis. Among avirulence genes corresponding to 19 resistance genes, significantly associated SP-SNP markers were detected for avirulence genes AvYr1, AvYr2, AvYr6, AvYr7, AvYr8, AvYr44, AvYrExp2, AvYrSP, and AvYrTye. These results indicate that association analysis can be used to identify markers for avirulence genes. This study has laid the foundation for developing more SP-SNPs for mapping avirulence genes using segregating populations that can be generated through sexual reproduction on alternate hosts of the pathogen.
Variation in Telial Formation of Puccinia striiformis in the United States  [PDF]
Anmin Wan, Meinan Wang, Xianming Chen
American Journal of Plant Sciences (AJPS) , 2019, DOI: 10.4236/ajps.2019.105060
Abstract:

Puccinia striiformis, the causal agent of stripe rust in wheat, barley, and various wild grasses, produces urediniospores and teliospores on these primary or auxiliary hosts. Telial formation, which stops producing infectious urediniospores, is affected by various host and environmental conditions. However, it is not clear if variation exists among different isolates in the United States. To determine the differences in the pathogen population, 1423 isolates collected in the United States from 2013 to 2016 were tested for telial formation in the seedling stage at a diurnal temperature profile of 4°C - 20°C. The percentages of telial formation varied greatly among the isolates. Of the 1423 isolates, 62.97% produced telia with the percentages of telial formation ranging from 1% to 95% under the test conditions. The formation of telia was significantly affected by the year and the month when the isolates were collected. The epidemiological regions or states, host plants (wheat, barley, and grasses), and races of the isolates did not significantly affect telial formation. However, significant effects on telial formation were observed by interactions between year and region, year and race, month and region and among year, month, and region, as well as between year and month. The results showed that telial formation is a complex trait under the genetic control of the pathogen isolates for adaptation to different environments. Further studies are needed to identify genes involved in the formation of telia and the relationship of telial formation to the survival, aggressiveness, fitness, and evolution of the pathogen.

Constructing Physical and Genomic Maps for Puccinia striiformis f. sp. tritici, the Wheat Stripe Rust Pathogen, by Comparing Its EST Sequences to the Genomic Sequence of P. graminis f. sp. tritici, the Wheat Stem Rust Pathogen
Jinbiao Ma,Xianming Chen,Meinan Wang,Zhensheng Kang
Comparative and Functional Genomics , 2009, DOI: 10.1155/2009/302620
Abstract: The wheat stripe rust fungus, Puccinia striiformis f. sp. tritici (Pst), does not have a known alternate host for sexual reproduction, which makes it impossible to study gene linkages through classic genetic and molecular mapping approaches. In this study, we compared 4,219 Pst expression sequence tags (ESTs) to the genomic sequence of P. graminis f. sp. tritici (Pgt), the wheat stem rust fungus, using BLAST searches. The percentages of homologous genes varied greatly among different Pst libraries with 54.51%, 51.21%, and 13.61% for the urediniospore, germinated urediniospore, and haustorial libraries, respectively, with an average of 33.92%. The 1,432 Pst genes with significant homology with Pgt sequences were grouped into physical groups corresponding to 237 Pgt supercontigs. The physical relationship was demonstrated by 12 pairs (57%), out of 21 selected Pst gene pairs, through PCR screening of a Pst BAC library. The results indicate that the Pgt genome sequence is useful in constructing Pst physical maps.
A Broadband Circularly Polarized Stacked Probe-Fed Patch Antenna for UHF RFID Applications
Hang Leong Chung,Xianming Qing,Zhi Ning Chen
International Journal of Antennas and Propagation , 2007, DOI: 10.1155/2007/76793
Abstract: A broadband circularly polarized stacked probe-fed antenna suitable for UHF RFID applications is presented and studied. The proposed antenna is fed by two probes which are connected to a hybrid coupler. Two parasitic patches are stacked above a primary probe-fed patch to enhance the bandwidth of the antenna. The optimized antenna prototype achieves gain of more than 6.5 dBic, axial ratio of less than 3.0 dB, and return loss of less than −15 dB over the UHF band of 820–980 MHz (17.7%). Parametric studies are carried out to demonstrate the effects of antenna geometry parameters on the performance. The proposed antenna can be a good candidate for UHF RFID applications.
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