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Search Results: 1 - 10 of 28412 matches for " Qianqian Zhu "
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On the Conservative Finite Difference Scheme for the Generalized Novikov Equation  [PDF]
Wenxia Chen, Qianqian Zhu, Ping Yang
Journal of Applied Mathematics and Physics (JAMP) , 2017, DOI: 10.4236/jamp.2017.59150
Abstract: In this paper, we investigate a numerical method for the generalized Novikov equation. We propose a conservative finite difference scheme and use Brouwer fixed point theorem to obtain the existence of the solution of the corresponding difference equation. We also prove the convergence and stability of the solution by using the discrete energy method. Moreover, we obtain the truncation error of the difference scheme which is \"\".
Local Influence Analysis of Generalized Linear Model  [PDF]
Shuling Wang, Qianqian Zhu, Ting Wang, Man Liu
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.39156
Abstract: Nearly thirty years, the diagnosis and influence analysis of linear regression model has been fully developed. So far the local influence analysis of the generalized linear model has not yet seen in the literature. In this paper, local influence is discussed. Then, concise influence matrix is obtained. At last, an example is given to illustrate our results.
The Correctional Model of Population Development Equation  [PDF]
Man Liu, Daqing Liao, Qianqian Zhu, Zhengming Wang
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.34019

The problem of population development has always been the key problem of restricting the development of our country. In order to increase the prediction accuracy, we analyze the exponential model, logistic model and continuous model. Also, the improved discrete population development model is provided to control the quantity and improve the quality of population.

A Kind of Improved Susceptible-Infected Model  [PDF]
Qianqian Zhu, Man Liu, Qingzhi Yu, Zhengming Wang
Modeling and Numerical Simulation of Material Science (MNSMS) , 2013, DOI: 10.4236/mnsms.2013.34015

By analyzing the susceptible-infected model, susceptible-infected-recovered-susceptible model and susceptible infected-recovered model, we get the improved Kermachk-Mckendrick model. And by applying the controlled threshold value, we get the conditions of isolated rate for infectious disease eventually disappeared. 

Complex organizational structure of the genome revealed by genome-wide analysis of single and alternative promoters in Drosophila melanogaster
Qianqian Zhu, Marc S Halfon
BMC Genomics , 2009, DOI: 10.1186/1471-2164-10-9
Abstract: We have undertaken a systematic investigation of Drosophila promoters. We divided promoters into three groups: unique promoters, first alternative promoters (the most 5' of a gene's multiple promoters), and downstream alternative promoters (the remaining alternative promoters 3' to the first). We observed distinct nucleotide distribution and sequence motif preferences among these three classes. We also investigated the promoters of neighboring genes and found that a greater than expected number of adjacent genes have similar sequence motif profiles, which may allow the genes to be regulated in a coordinated fashion. Consistent with this, there is a positive correlation between similar promoter motifs and related gene expression profiles for these genes.Our results suggest that different regulatory mechanisms may apply to each of the three promoter classes, and provide a mechanism for "gene expression neighborhoods," local clusters of co-expressed genes. As a whole, our data reveal an unexpected complexity of genomic organization at the promoter level with respect to both alternative and neighboring promoters.Coordinated regulation of gene expression is a fundamental process that depends on the binding of transcription factors to a gene's cis-regulatory sequences. Absolutely required for transcription initiation of metazoan protein-coding genes is the core promoter, the region of DNA 35–40 bp upstream and downstream of the transcription start site (TSS) [1]. The core promoter contains sequence elements, referred to as "core promoter motifs," which interact with the basal transcription machinery, including RNA polymerase II and the TFIID complex [2]. In recent years, it has become clear that the core promoter, rather than playing a passive role in the spatial and temporal regulation of gene expression, is an important active partner in these events [3,4]. For instance, different promoter sequences are found preferentially associated with certain functional classes of
A Comparative Study of China-U.S. Tourism Characteristic Industry GVC1 Embedment Degree  [PDF]
Qianqian Wang
American Journal of Industrial and Business Management (AJIBM) , 2018, DOI: 10.4236/ajibm.2018.86104
Abstract: As the largest branch of service trade, tourism trade has contributed continuously to the global economy. Starting from the related departments of tourism trade, this article used the method of Wang et al. (2013) to conduct value-added decomposition of the global input-output table for the period 2000-2014 and measured the GVC position and GVC participation index between China and the United States for first time. The author just intends to consider the related tourism industries, but it didn’t integrate the related industries to a complete tourism industry. The comparative study found that Chinas road transportation sector has advantage over the United States’, but overall the GVC position and GVC participation index of China tourism characteristic departments are less than the United States’. For the whole embedment degree of GVC, there is still a gap between China and the United States.
Economic Cycle, Uncertainty of Economic Policy and Cash Holding of Listed Companies  [PDF]
Qianqian Wang
Modern Economy (ME) , 2019, DOI: 10.4236/me.2019.101019

Based on the systematic review and economic analysis of the theoretical literature, we consider not only the impact of the economic cycle or the economic policy uncertainty (EPU) on the cash holding ratio, but also the comprehensive impact of the two on the cash holding rate. We raise the research hypothesis by using the data from 2004-2015 in the A-share listed companies which are listed in Shanghai and Shenzhen securities exchange as research samples. The empirical results show that: 1) There are respectively negative correlation between the economic cycle and the cash holding of listed companies, and positive correlation between the EPU and the cash holding. 2) During the boom, the cash holdings are significantly positive with the current EPU and the last stage; during the recession, the cash holdings of listed companies is significantly negatively correlated with the current EPU, while positive with the last stage. 3) We further examine the role of the economic cycle and the EPU on the cash holding value, and find that EPU will reduce the cash holding value. 4) When the economy is booming, the increase in EPU will reduce the market value of corporate cash holdings, but it is not significant. During recession, the increase in EPU will increase the market value of cash holdings.

Preferred analysis methods for Affymetrix GeneChips. II. An expanded, balanced, wholly-defined spike-in dataset
Qianqian Zhu, Jeffrey C Miecznikowski, Marc S Halfon
BMC Bioinformatics , 2010, DOI: 10.1186/1471-2105-11-285
Abstract: We generated a new wholly defined Affymetrix spike-in dataset consisting of 18 microarrays. Over 5700 RNAs are spiked in at relative concentrations ranging from 1- to 4-fold, and the arrays from each condition are balanced with respect to both total RNA amount and degree of positive versus negative fold change. We use this new "Platinum Spike" dataset to evaluate microarray analysis routes and contrast the results to those achieved using our earlier Golden Spike dataset.We present updated best-route methods for Affymetrix GeneChip analysis and demonstrate that the degree of "imbalance" in gene expression has a significant effect on the performance of these methods.As a result of their ability to detect the expression levels of tens of thousands of genes simultaneously, DNA microarrays have quickly become a leading tool in diverse areas of biological and biomedical research. Given this popularity and the associated accumulation of numerous microarray analysis methods, there is a critical need to know the accuracy of microarray technology and the best ways of analyzing microarray data. Important advances toward this goal were made by the MicroArray Quality Control (MAQC) project launched by US Food and Drug Administration [1]. For the MAQC study, two distinct reference RNA samples were mixed together at specified ratios and then hybridized to different microarray platforms at multiple test sites. This design enabled the MAQC consortium to evaluate the reproducibility of microarray technology and the consistency between platforms. The study demonstrated that high levels of both intraplatform and interplatform concordance can be achieved in detecting differentially expressed genes (DEGs) when the microarray experiment is performed appropriately. However, as the exact identities of the individual RNAs in the reference samples were unknown, the MAQC project was not able to address questions regarding the overall accuracy of microarray technology and analysis methods.Spike
Erroneous attribution of relevant transcription factor binding sites despite successful prediction of cis-regulatory modules
Marc S Halfon, Qianqian Zhu, Elizabeth R Brennan, Yiyun Zhou
BMC Genomics , 2011, DOI: 10.1186/1471-2164-12-578
Abstract: We successfully predicted five new cis-regulatory modules by combining binding site identification with sequence conservation and compared these to unsuccessful predictions from a related approach not utilizing sequence conservation. Despite greatly improved predictive success, the positive set had similar degrees of sequence and binding site conservation as the negative set. We explored the reasons for this by mutagenizing putative binding sites in three cis-regulatory modules. A large proportion of the tested sites had little or no demonstrable role in mediating regulatory element activity. Examination of loss-of-function mutants also showed that some transcription factors supposedly binding to the modules are not required for their function.Our results raise important questions about interpreting regulatory module predictions obtained by finding clusters of conserved binding sites. Attribution of function to these sites and their cognate transcription factors may be incorrect even when modules are successfully identified. Our study underscores the importance of empirical validation of computational results even when these results are in line with expectation.Developmental control of gene expression depends on the activity of transcriptional enhancers, or "cis-regulatory modules" (CRMs) [reviewed by [1,2]]. These regulatory sequences coordinate the binding of sequence-specific transcription factors and can stimulate transcription of their target genes irrespective of distance, location (5' or 3'), and orientation relative to the transcription start site. A CRM typically contains one or more binding sites for several different transcription factors (TFs), both activators and repressors. Efficient discovery of CRMs in the genome has proven challenging, although significant progress has been made recently with respect to both experimental and bioinformatics approaches [3]. As with many genomic techniques, however, in silico results have accumulated much faster than t
Evolutionary relationships between miRNA genes and their activity
Zhu Yan,Skogerb? Geir,Ning Qianqian,Wang Zhen
BMC Genomics , 2012, DOI: 10.1186/1471-2164-13-718
Abstract: Background The emergence of vertebrates is characterized by a strong increase in miRNA families. MicroRNAs interact broadly with many transcripts, and the evolution of such a system is intriguing. However, evolutionary questions concerning the origin of miRNA genes and their subsequent evolution remain unexplained. Results In order to systematically understand the evolutionary relationship between miRNAs gene and their function, we classified human known miRNAs into eight groups based on their evolutionary ages estimated by maximum parsimony method. New miRNA genes with new functional sequences accumulated more dynamically in vertebrates than that observed in Drosophila. Different levels of evolutionary selection were observed over miRNA gene sequences with different time of origin. Most genic miRNAs differ from their host genes in time of origin, there is no particular relationship between the age of a miRNA and the age of its host genes, genic miRNAs are mostly younger than the corresponding host genes. MicroRNAs originated over different time-scales are often predicted/verified to target the same or overlapping sets of genes, opening the possibility of substantial functional redundancy among miRNAs of different ages. Higher degree of tissue specificity and lower expression level was found in young miRNAs. Conclusions Our data showed that compared with protein coding genes, miRNA genes are more dynamic in terms of emergence and decay. Evolution patterns are quite different between miRNAs of different ages. MicroRNAs activity is under tight control with well-regulated expression increased and targeting decreased over time. Our work calls attention to the study of miRNA activity with a consideration of their origin time.
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