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Search Results: 1 - 10 of 44011 matches for " Feifan Wu "
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On the Yamabe Problem on contact Riemannian Manifolds
Feifan Wu,Wei Wang
Mathematics , 2015,
Abstract: Contact Riemannian manifolds, whose complex structures are not necessarily integrable, are generalization of pseudohermitian manifolds in CR geometry. The Tanaka-Webster-Tanno connection plays the role of the Tanaka-Webster connection of a pseudohermitian manifold. Conformal transformations and the Yamabe problem are also defined naturally in this setting. By constructing the special frames and the normal coordinates on a contact Riemannian manifold, we prove that if the complex structure is not integrable, its Yamabe invariant on a contact Riemannian manifold is always less than the Yamabe invariant of the Heisenberg group. So the Yamabe problem on a contact Riemannian manifold is always solvable.
The Bochner-Type Formula and The First Eigenvalue of the sub-Laplacian on a Contact Riemannian Manifold
Feifan Wu,Wei Wang
Mathematics , 2015,
Abstract: Contact Riemannian manifolds, with not necessarily integrable complex structures, are the generalization of pseudohermitian manifolds in CR geometry. The Tanaka-Webster-Tanno connection on such a manifold plays the role of Tanaka-Webster connection in the pseudohermitian case. We prove the contact Riemannian version of the pseudohermitian Bochner-type formula, and generalize the CR Lichnerowicz theorem about the sharp lower bound for the first nonzero eigenvalue of the sub-Laplacian to the contact Riemannnian case.
Branched chain amino acids and metabolic regulation
ChunXia Wang,FeiFan Guo
Chinese Science Bulletin , 2013, DOI: 10.1007/s11434-013-5681-x
Abstract: Amino acids are fundamental nutrients required for protein synthesis. The branched chain amino acids (BCAAs) leucine, isoleucine, and valine are the most abundant of the essential amino acids. BCAAs have recently been recognized as having functions in processes other than simple nutrition. For example, metabolic diseases are characterized by higher levels of circulating BCAAs. Moreover, supplementation with or deficiency in BCAAs is closely related to the regulation of metabolic homeostasis. Indeed, leucine deprivation induces increased lipolysis and thermogenesis, which result in fat loss, as well as suppressed lipogenesis and enhanced insulin sensitivity in the liver. Accumulating evidence has indicated that several amino acid sensors, including GCN2, ATF4, mTOR, and AMPK, play pivotal roles in the regulation of lipid metabolism, glucose metabolism, and energy homeostasis. Furthermore, the hypothalamus is critical for sensing amino acid levels and mediates the metabolic adaptation of the body upon limitation of essential amino acids (EAAs) through regulating expression of the S6K1, MC4R, and CRH. In this review, we highlight recent studies investigating the cellular mechanisms linking amino acids, amino acid sensors, metabolic regulation, and metabolic diseases. Amino acid sensing and metabolic regulation have become research hotspots in the metabolic field.
Non-linear forcing singular vector of a two-dimensional quasi-geostrophic model
Wansuo Duan,Feifan Zhou
Tellus A , 2013, DOI: 10.3402/tellusa.v65i0.18452
Abstract: We propose a non-linear forcing singular vector (NFSV) approach to infer the effect of non-linearity on the predictability associated with model errors. The NFSV is a generalisation of the forcing singular vector (FSV) to non-linear fields and acts as a tendency perturbation that results in a significantly large perturbation growth. In predictability studies, the NFSV, as a tendency error, may provide useful information about model errors that cause severe prediction uncertainties. In this article, a two-dimensional quasi-geostrophic (QG) model is used to study NFSVs and make a comparison between NFSVs and FSVs. We choose two basic flows: the first is a zonal steady flow (Ref-1), and the second is a meridional steady flow (Ref-2). The results demonstrate that the corresponding NFSVs contain a phase where the stream function tends to be contracted around regions of strong velocity shear. Furthermore, the NFSVs for the Ref-1 tend to have a meridional asymmetric spatial structure. Due to the absence of non-linearity, FSVs tend to have a larger spatial extension than NFSVs; in particular, the FSVs for the Ref-1 are almost symmetric in the stream function component. The prediction errors caused by FSVs in the non-linear QG model are generally smaller than those caused by FSVs in the linearised QG model; therefore, the non-linearity in the QG model would significantly saturate the perturbation growth. Nevertheless, the prediction errors caused by NFSVs (especially for the Ref-1) in the non-linear QG model are larger than those caused by FSVs, which further implies that the tendency errors of NFSV structures tend to reduce the damping effect of the non-linearity on the perturbation growth and are more applicable than those of FSV structures to describing the optimal mode of the model errors. The differences between NFSVs and FSVs demonstrate the usefulness of NFSVs in revealing the effects of non-linearity on predictability. The NFSV may be a useful non-linear technique for exploring the predictability problems introduced by model errors.
Learning to Rank Figures within a Biomedical Article
Feifan Liu, Hong Yu
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0061567
Abstract: Hundreds of millions of figures are available in biomedical literature, representing important biomedical experimental evidence. This ever-increasing sheer volume has made it difficult for scientists to effectively and accurately access figures of their interest, the process of which is crucial for validating research facts and for formulating or testing novel research hypotheses. Current figure search applications can't fully meet this challenge as the “bag of figures” assumption doesn't take into account the relationship among figures. In our previous study, hundreds of biomedical researchers have annotated articles in which they serve as corresponding authors. They ranked each figure in their paper based on a figure's importance at their discretion, referred to as “figure ranking”. Using this collection of annotated data, we investigated computational approaches to automatically rank figures. We exploited and extended the state-of-the-art listwise learning-to-rank algorithms and developed a new supervised-learning model BioFigRank. The cross-validation results show that BioFigRank yielded the best performance compared with other state-of-the-art computational models, and the greedy feature selection can further boost the ranking performance significantly. Furthermore, we carry out the evaluation by comparing BioFigRank with three-level competitive domain-specific human experts: (1) First Author, (2) Non-Author-In-Domain-Expert who is not the author nor co-author of an article but who works in the same field of the corresponding author of the article, and (3) Non-Author-Out-Domain-Expert who is not the author nor co-author of an article and who may or may not work in the same field of the corresponding author of an article. Our results show that BioFigRank outperforms Non-Author-Out-Domain-Expert and performs as well as Non-Author-In-Domain-Expert. Although BioFigRank underperforms First Author, since most biomedical researchers are either in- or out-domain-experts for an article, we conclude that BioFigRank represents an artificial intelligence system that offers expert-level intelligence to help biomedical researchers to navigate increasingly proliferated big data efficiently.
The Impact of Horizontal Resolution on the CNOP and on Its Identified Sensitive Areas for Tropical Cyclone Predictions

ZHOU Feifan,MU Mu,

大气科学进展 , 2012,
Abstract: In this study, the impacts of horizontal resolution on the conditional nonlinear optimal perturbation (CNOP) and on its identified sensitive areas were investigated for tropical cyclone predictions. Three resolutions, 30 km, 60 km, and 120 km, were studied for three tropical cyclones, TC Mindulle (2004), TC Meari (2004), and TC Matsa (2005).
The Time and Regime Dependencies of Sensitive Areas for Tropical Cyclone Prediction Using the CNOP Method

ZHOU Feifan,MU Mu,

大气科学进展 , 2012,
Abstract: This study examines the time and regime dependencies of sensitive areas identified by the conditional nonlinear optimal perturbation (CNOP) method for forecasts of two typhoons. Typhoon Meari (2004) was weakly nonlinear and is herein referred to as the linear case, while Typhoon Matsa (2005) was strongly nonlinear and is herein referred to as the nonlinear case. In the linear case, the sensitive areas identified for special forecast times when the initial time was fixed resembled those identified for other forecast times. Targeted observations deployed to improve a special time forecast would thus also benefit forecasts at other times. In the nonlinear case, the similarities among the sensitive areas identified for different forecast times were more limited. The deployment of targeted observations in the nonlinear case would therefore need to be adapted to achieve large improvements for different targeted forecasts. For both cases, the closer the forecast time, the higher the similarities of the sensitive areas. When the forecast time was fixed, the sensitive areas in the linear case diverged continuously from the verification area as the forecast period lengthened, while those in the nonlinear case were always located around the initial cyclones. The deployment of targeted observations to improve a special forecast depends strongly on the time of deployment. An examination of the efficiency gained by reducing initial errors within the identified sensitive areas confirmed these results. In general, the greatest improvement in a special time forecast was obtained by identifying the sensitive areas for the corresponding forecast time period.
The Impact of Verification Area Design on Tropical Cyclone Targeted Observations Based on the CNOP Method

ZHOU Feifan,MU Mu,

大气科学进展 , 2011,
Abstract: This study investigated the impact of different verification-area designs on the sensitive areas identified using the conditional nonlinear optimal perturbation (CNOP) method for tropical cyclone targeted observations. The sensitive areas identified using the first singular vector (FSV) method, which is the linear approximation of CNOP, were also investigated for comparison. By analyzing the validity of the sensitive areas, the proper design of a verification area was developed. Tropical cyclone Rananim, which occurred in August 2004 in the northwest Pacific Ocean, was studied. Two sets of verification areas were designed; one changed position, and the other changed both size and position. The CNOP and its identified sensitive areas were found to be less sensitive to small variations of the verification areas than those of the FSV and its sensitive areas. With larger variations of the verification area, the CNOP and the FSV as well as their identified sensitive areas changed substantially. In terms of reducing forecast errors in the verification area, the CNOP-identified sensitive areas were more beneficial than those identified using FSV. The design of the verification area is important for cyclone prediction. The verification area should be designed with a proper size according to the possible locations of the cyclone obtained from the ensemble forecast results. In addition, the development trend of the cyclone analyzed from its dynamic mechanisms was another reference. When the general position of the verification area was determined, a small variation in size or position had little influence on the results of CNOP.
Combined remediation of DDT congeners and cadmium in soil by Sphingobacterium sp. D-6 and Sedum alfredii Hance
Hua Fang,Wei Zhou,Zhengya Cao,Feifan Tang,Dandan Wang,Kailin Liu,Xiangwei Wu,Xiao''e Yang,Yongge Sun,Yunlong Yu,
Hua Fang
,Wei Zhou,Zhengya Cao,Feifan Tang,Dandan Wang,Kailin Liu,Xiangwei Wu,Xiao''e Yang,Yongge Sun,Yunlong Yu

环境科学学报(英文版) , 2012,
Abstract: Combined pollution of 1,1,1-trichloro-2,2-bis (4-chlorophenyl) ethane (DDT) and cadmium (Cd) in agricultural soils is of great concern because they present serious risk to food security and human health. In order to develop a cost-effective and safe method for the removal of DDTs and Cd in soil, combined remediation of DDTs and Cd in soil by Sphingobacterium sp. D-6 and the hyperaccumulator, Sedum alfredii Hance was investigated. After treatment for 210 days, the degradation half-lives of DDTs in soils treated by strain D-6 decreased by 8.1% to 68.0% compared with those in the controls. The inoculation of strain D-6 into soil decreased the uptake of DDTs by pak choi and S. alfredii. The shoots/roots ratios of S. alfredii for the Cd accumulation ranged from 12.32 to 21.75. The Cd concentration in soil decreased to 65.8%--71.8% for S. alfredii treatment and 14.1%--58.2% for S. alfredii and strain D-6 combined treatment, respectively, compared with that in the control. The population size of the DDTs-degrading strain, Simpson index (1/D) and soil respiratory rate decreased in the early stage of treatment and then gradually increased, ultimately recovering to or exceeding the initial level. The results indicated that synchronous incorporation of strain D-6 and S. alfredii into soil was found to significantly (p ≤ 0.05) enhance the degradation of DDTs in soil and the hyperaccumulation of Cd in S. alfredii. It was concluded that strain D-6 and S. alfredii could be used successfully to control DDTs and Cd in contaminated soil.
Automatic Figure Ranking and User Interfacing for Intelligent Figure Search
Hong Yu,Feifan Liu,Balaji Polepalli Ramesh
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0012983
Abstract: Figures are important experimental results that are typically reported in full-text bioscience articles. Bioscience researchers need to access figures to validate research facts and to formulate or to test novel research hypotheses. On the other hand, the sheer volume of bioscience literature has made it difficult to access figures. Therefore, we are developing an intelligent figure search engine (http://figuresearch.askhermes.org). Existing research in figure search treats each figure equally, but we introduce a novel concept of “figure ranking”: figures appearing in a full-text biomedical article can be ranked by their contribution to the knowledge discovery.
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