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Search Results: 1 - 10 of 13643 matches for " FAN Youhua "
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Choice of the Models for the Co-operative Innovation of Industries, Universities and Research Institutes by Game Analysis
Yiyang Fan,Youhua Zhang
Asian Social Science , 2010, DOI: 10.5539/ass.v6n9p96
Abstract: This paper builds game model to analyze selection issues of IUR co-operation model through Nash bargaining theory. The result shows that, the stronger innovative capability, more economic benefits expected, less technical content of scientific research, companies more inclined to choose a higher degree of close model; otherwise, companies tend to choose more closely integrated degree lower mode.
Global environment- and space-richness ranking relationships: The effects of interaction and high-order terms of explanatory variables  [PDF]
Youhua Chen
Open Journal of Ecology (OJE) , 2013, DOI: 10.4236/oje.2013.36044
Abstract:

In the present study, the interplay and higher-order terms of environmental and spatial variables are considered to evaluate the relations of environment and space-species richness rankings at global scale. Three taxonomic groups composed of mammals, birds and amphibians were analyzed for the study. Thek-means clustering method was introduced for richness rankings detection and analysis from published digital maps; and simple regression analysis and AIC criteria were used for identifying mostimportant correlated explanatory variables.When comparing each single variable, I found that latitude was the most important one influencing global vertebrate richness rankings. When onlyconsidering environmental variables, I foundthat precipitation was the only predictor of vertebrate richness rankings. However, when the interaction and high-order terms of different independent variables were considered, it was found that the interaction between latitude and temperature could better explain the global bird richness ranking, while the second-power effectof latitude was the best predictor for amphibianand mammalian richness rankings, as evidenced by the AIC model selection and comparison among the regression models. In conclusion, the inclusion of high-order and interaction terms of environmental and spatial variables could offer more insights into the understanding of global species diversity patterns.

AGE-LDL Activates Toll Like Receptor 4 Pathway and Promotes Inflammatory Cytokines Production in Renal Tubular Epithelial Cells
Ao Cheng, Yuanyuan Dong, Fengxin Zhu, Youhua Liu, Fan Fan Hou, Jing Nie
International Journal of Biological Sciences , 2013,
Abstract: Background/Aims: Accumulation of advanced glycation end-products, the well-recognized pro-inflammatory molecules, has been detected in renal tissues including tubules. The aim of the present study was to investigate the role of advanced glycation end-products modified low density lipoprotein (AGE-LDL) in inflammatory cytokines production in human proximal tubular epithelial cells and the underlying mechanism. Methods: The Interleukin-6 (IL-6) and Interleukin-8 (IL-8) production was examined by real-time PCR and ELISA. The expression of Toll-like receptor 2 and 4 (TLR2/4) was detected by flow cytometry and western blot. The interaction of TLR2/4 with AGE-LDL was examined by co-immunoprecipitation assay. The involvement of MyD88 and the downstream molecules in inflammatory cytokines production was examined by siRNA and pharmacologic inhibitors, respectively. Results: AGE-LDL interacted with TLR2 and TLR4. TLR4 siRNA showed stronger inhibition on AGE-LDL-induced IL-6 and IL-8 production than that of TLR2 siRNA. Silencing MyD88, but not TRIF, inhibited AGE-LDL-induced IL-6 and IL-8 production. AGE-LDL stimulation led to phosphorylation of JNK, p38, Akt and the p65 subunit of nuclear factor-κB (NF-κB). Pharmacologic inhibitor of Akt suppressed AGE-LDL-induced activation of NF-κB, but the inhibitor of JNK, p38 or ERK1/2 had no effect. Blocking MyD88, p38, JNK, Akt or NF-κB attenuated AGE-LDL-triggered IL-6 production. Conclusion: AGE-LDL induced IL-6 and IL-8 production via TLR2/4-MyD88-dependent pathway in tubular epithelial cells. These data suggest that activation of TLRs signaling in tubular epithelial cells by AGE-LDL might be a novel mechanism for the tubulointerstitial inflammation.
An Overview of Talent Cultivation Models in Foreign Vocational Colleges
Youhua Wang
International Education Studies , 2010, DOI: 10.5539/ies.v3n1p170
Abstract: A talent cultivation model refers to a model of the construction and operation of the cultivation process adopted by a school to achieve its cultivation objectives. Four models, with their differences and similarities, are introduced in this paper.
Modeling species-area relationship with measurement uncertainty
Youhua Chen
Journal of Entomology and Zoology Studies , 2013,
Abstract:
Natural Selection Determines Synonymous Codon Usage Patterns of Neuraminidase (NA) Gene of the Different Subtypes of Influenza A Virus in Canada
Youhua Chen
Journal of Viruses , 2014, DOI: 10.1155/2014/329049
Abstract: Synonymous codon usage patterns of neuraminidase (NA) gene of 64 subtypes (one is a mixed subtype) of influenza A virus found in Canada were analyzed. In total, 1422 NA sequences were analyzed. Among the subtypes, H1N1 is the prevailing one with 516 NCBI accession records, followed by H3N2, H3N8, and H4N6. The year of 2009 has the highest report records for the NA sequences in Canada, corresponding to the 2009 pandemic event. Correspondence analysis on the RSCU values of the four major subtypes showed that they had distinct clustering patterns in the two-dimensional scatter plot, indicating that different subtypes of IAV utilized different preferential codons. This subtype clustering pattern implied the important influence of natural selection, which could be further evidenced by an extremely flattened regression line in the neutrality plot (GC12 versus G3s plot) and a significant phylogenetic signal on the distribution of different subtypes in the clades of the phylogenetic tree ( statistic). In conclusion, different subtypes of IAV showed an evolutionary differentiation on choosing different optimal codons. Natural selection played a deterministic role to structure IAV codon usage patterns in Canada. 1. Introduction Codon usage is not a random event [1]. Codon usage bias has been broadly observed, and different mechanisms have been proposed to explain the bias patterns, for example, mutation pressure, translational efficiency, gene length [2], dinucleotide bias [3], tRNA abundance [4], organ specificity [5], and so on. Codon usage bias patterns have been broadly studied in recent years, especially for virus genomes [3, 6, 7]. In recent years, codon usage patterns have been widely explored for influenza viruses [6, 8–12]. Among the three influenza viruses, influenza A virus (IAV) is the major concern since it has a lot of subtypes. IAV is a genus of Orthomyxoviridae family of viruses, which caused influenza in birds and mammals [6, 13]. Among the eight RNA segments of IAV, hemagglutinin and neuraminidase (NA) genes are the principal concerns. Currently, most of modeling efforts on IAV are focused on Asian regions [6, 8]; little attention is paid on the evolutionary patterns of IAV in local areas of North America. To fill such a knowledge gap, in the present study, I analyzed all the available 1436 NA ORFs for IAV found in Canada to reveal the codon usage patterns of IAV different subtypes in Canada. 2. Materials and Methods 2.1. Sequence Data 1436 NA sequences found in IAV strains of Canada were extracted from NCBI GenBank database
Modeling Extinction Risk of Endemic Birds of Mainland China
Youhua Chen
International Journal of Evolutionary Biology , 2013, DOI: 10.1155/2013/639635
Abstract: The extinction risk of endemic birds of mainland China was modeled over evolutionary time. Results showed that extinction risk of endemic birds in mainland China always tended to be similar within subclades over the evolutionary time of species divergence, and the overall evolution of extinction risk of species presented a conservatism pattern, as evidenced by the disparity-through-time plot. A constant-rate evolutionary model was the best one to quantify the evolution of extinction risk of endemic birds of mainland China. Thus, there was no rate shifting pattern for the evolution of extinction risk of Chinese endemic birds over time. In a summary, extinction risk of endemic birds of mainland China is systematically quantified under the evolutionary framework in the present work. 1. Introduction Global biodiversity crisis is emerging and increasingly recognized in recent years for biologists [1]. Terrestrial environment has been widely affected by humans [2] and habitats of terrestrial species are facing irreplaceable transformation which in term would pose great threats to the survival of these species. It is said that worldwide organisms are now facing the sixth mass extinction period [3, 4]. In such a context, ecologists have high pressures to facilitate conservation measures so as to better offer refuges for conserving species. One of these measures is to understand the evolution and drivers of extinction risk of species [5, 6]. Birds are an important vertebrate taxonomy and deserve to be allocated more conservation efforts because of their popularity for common people [7–9]. Understanding and modeling extinction risk of birds would be an important step to set up corresponding conservation strategies. There are growing interests focusing on the diversification, biogeography, conservation, and extinction risk of bird species [10–13]. In recent years, one of the trends in conservation biology is to sufficiently incorporate evolutionary information for the purpose to evaluate the impacts of species history on structuring species’ contemporary distribution [14], conservation priorities [15, 16], or threatened risk [2, 17, 18]. One rationale for modeling extinction risk of species through phylogenetic tree is that the underlying ecological variables associated with extinction risk of species are related to evolutionary history of species, for example, distributional ranges [14, 19], morphological traits [20], physiological tolerance spectrum of environmental conditions [21], and others. China is one of the megabiodiverse countries over the world [22].
Distributional Patterns of Alien Plants in China: The Relative Importance of Phylogenetic History and Functional Attributes
Youhua Chen
ISRN Ecology , 2013, DOI: 10.1155/2013/527052
Abstract: Distribution patterns of alien species in nonnative ranges might be driven by a combination of various mechanisms, including phylogenetic history, competition for resource, environmental filtering, and so on. Both phylogenetic and functional limitations might work synergistically to determine the distribution of alien species. In this report, by utilizing the information of provincial distribution, functional attributes, and phylogeny for 95 alien species of China, the corresponding phylogenetic and functional community structures are evaluated. The results show that introduction pathway, life form, and flowering time of alien plants of China processed significant phylogenetic clustering patterns, while both the origin of distribution and reproduction mode of alien species showed phylogenetic overdispersion patterns, as revealed by NRI/NTI indices. The phylogenetic signal tests using Pagel’s statistic and Blomberg et al.’s statistic further verified the previous patterns, even though there are some inconsistencies. Through partial Mantel test, it is found that compositional patterns of alien plant community were mainly affected by phylogenetic limitation but not functional limitation. Conclusively, phylogeny plays a more important role in structuring provincial distribution of alien plants in China. 1. Introduction Alien species may possess novel functional traits for successful colonization of new habitats, in addition to random events or similar traits to native species [1–3]. However, some recent studies have pointed out that phylogeny is also playing some role on influencing alien diversity and distribution patterns [4–7]. Functional attributes and phylogenetic history reflected different facets of biological diversity, and the growing trend in ecological studies nowadays is to combine both to address the questions related to the diversity [8–10], distribution [11], and ecosystem functioning [12, 13]. The application of combining both functional and phylogenetic filtering simultaneously to understand the distributional pattern of alien species in nonnative ranges has been concerned in recent studies [14]. It would be of great value to explore their interplay using alien species as the studied model. Alien species have expanded their distributional ranges in recent decades due to globalization and modernization [15], the processes of which required the rapid ecological adaptation [16, 17]. The rapid range expansion indicated the functional uniqueness or commonness of traits when compared alien and native plants [1, 3]. At another perspective, in
Distinguishing niche and neutral processes: issues in variation partitioning statistical methods and further perspectives
Youhua Chen
Quantitative Biology , 2014,
Abstract: Variance partitioning methods, which are built upon multivariate statistics, have been widely applied in different taxa and habitats in community ecology. Here, I performed a literature review on the development and application of the methods, and then discussed the limitation of available methods and the difficulties involved in sampling schemes. The central goal of the work is then to propose some potential practical methods that might help to overcome different issues of traditional least-square-based regression modeling. A variety of regression models has been considered for comparison. In initial simulations, I identified that generalized additive model (GAM) has the highest accuracy to predict variation components. Therefore, I argued that other advanced regression techniques, including the GAM and related models, could be utilized in variation partitioning for better quantifying the aggregation scenarios of species distribution.
Covariance among independent variables determines the overfitting and underfitting problems in variation partitioning methods: with a special focus on the mixed co-variation
Youhua Chen
Quantitative Biology , 2014,
Abstract: The effectiveness and validity of applying variation partitioning methods in community ecology has been questioned. Here, using mathematical deduction and numerical simulation, we made an attempt to uncover the underlying mechanisms determining the effectiveness of variation partitioning techniques. The covariance among independent variables determines the under-fitting and over-fitting problem with the variation partitioning process. Ideally, it is assumed that the covariance among independent variables will be zero (no correlation at all), however, typically there will be some colinearities. Therefore, we analyzed the role of slight covariance on influencing species variation partitioning. We concluded that when the covariance between spatial and environmental predictors is positive, all the three components-pure environmental, spatial variations and mixed covariation were over-fitted, with the sign of the true covariation being negative. In contrast, when the covariance is negative, all the three components were under-fitted with the sign of true covariation being positive. Other factors, including extra noise levels, the strengths of variable coefficients and the patterns of landscape gradients, could reduce the fitting problems caused by the covariance of variables. The conventional calculation of mixed covariation is incorrect and misleading, as the true and estimated covariations are always sign-opposite. In conclusion, I challenge the conventional three-step procedure of variation partitioning, suggesting that a full regression model with all variables together is robust enough to correctly partition variations.
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