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Generation of Multiple Weights in the Opportunistic Beamforming Systems  [PDF]
Guangyue LU, Lei ZHANG, Houquan YU, Chao SHAO
Wireless Sensor Network (WSN) , 2009, DOI: 10.4236/wsn.2009.13025
Abstract: A new scheme to generate multiple weights used in opportunistic beamforming (OBF) system is proposed to deal with the performance degradation due to the fewer active users in the OBF system. In the proposed scheme, only two mini-slots are employed to create effective channels, while more channel candidates can be obtained via linearly combining the two effective channels obtained during the two mini-slots, thus increas-ing the multiuser diversity and the system throughputs. The simulation results verify the effectiveness of the proposed scheme.
Investigation of airborne fungi at different altitudes in Shenzhen University  [PDF]
Li Li, Chao Lei, Zhi-Gang Liu
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.25063
Abstract: Aim: To investigate the richness of species or genera of airborne fungi, the amount of airborne fungi, and its seasonal variation at different al-titudes in Shenzhen University. The effect of meteorological factors on airborne fungi was also analyzed. Methods: Slide-exposure me- thod and open-plate method were used. Results: There were 27 genera or species of fungus spores identified. Among the identified fungal genus, Cladosporium, Ustilago, Alternaria, Helminth-sporium and Uredinales were more prevalent. There were 18 genera of fungi colonies identified. Among which Penicillium, non-sporulating fungi, Aspergillus, Saccharomyces and Cladosporium were more common. The airborne fungal spores were present in the atmosphere of Shenzhen University all year round. The peaks of airborne spores appeared during April and October, while the lowest numbers were observed during January, July and December from March 2005-Febrary 2006. The highest volumes of fungi colonies were observed during April, October and September, while the lowest numbers were de-tected during in January, July and December or May from March 2005-Febrary 2006. The meteoro-logical factors had no relationship between the total monthly spore count at 10 and 30 meter height. At 70 meter, the total spores count was negatively correlated with solar radiation. Conclusions: Most of the fungi spores decreased along with the increase of altitudes.
A new method of building permeability model in low-permeability reservoir numerical simulation  [PDF]
Yong-Chao Xue, Lin-Song Cheng, Lei Su
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.22020
Abstract: Aiming at solving the problem that big differ-ence exists between logging permeability and true permeability of micro-fractured low-permeability sand reservoir, this paper puts forward a new method to revise logging per-meability by using primiparity data of oil field. This method has been successfully applied to revise logging permeability of micro-fractured low-permeability sand reservoir in Baiyushan area of Jing’An oil field, which shows that the method is reliable because the geological model building through the permeability which has been handled by this method accords with the real reservoir significantly.
Micromixing of a Two Phase System in a Stirred Tank with Multiple Impellers  [PDF]
Lei Yang, Jingcai Cheng, Ping Fan, Chao Yang
Advances in Materials Physics and Chemistry (AMPC) , 2012, DOI: 10.4236/ampc.2012.24B039
Abstract:

The competitive iodide/iodate reaction scheme was used to ascertain the micromixing in the stirred solid-liquid systems. Two different glass beads from 450 to 1250 μm were tested. The effect of solid particles on reaction selectivity with multiple impellers at different feed points has been investigated. It was confirmed that glass beads as a second phase were suitable for the study. The segregation index has changed significantly only for the medium-sized particles at relatively high solid holdups. The cloud formation was clearly observed for the medium-sized particles at a concentration of 12.12 wt. %. When feeding into the clear liquid above the cloud, the value of the segregation index increased significantly. However, in the presence of particles of 1-1.25 mm, the influence on the selectivity was negligible when the agitation speed was increased.

 

 

 

Inferring MicroRNA Activities by Combining Gene Expression with MicroRNA Target Prediction
Chao Cheng, Lei M. Li
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0001989
Abstract: Background MicroRNAs (miRNAs) play crucial roles in a variety of biological processes via regulating expression of their target genes at the mRNA level. A number of computational approaches regarding miRNAs have been proposed, but most of them focus on miRNA gene finding or target predictions. Little computational work has been done to investigate the effective regulation of miRNAs. Methodology/Principal Findings We propose a method to infer the effective regulatory activities of miRNAs by integrating microarray expression data with miRNA target predictions. The method is based on the idea that regulatory activity changes of miRNAs could be reflected by the expression changes of their target transcripts measured by microarray. To validate this method, we apply it to the microarray data sets that measure gene expression changes in cell lines after transfection or inhibition of several specific miRNAs. The results indicate that our method can detect activity enhancement of the transfected miRNAs as well as activity reduction of the inhibited miRNAs with high sensitivity and specificity. Furthermore, we show that our inference is robust with respect to false positives of target prediction. Conclusions/Significance A huge amount of gene expression data sets are available in the literature, but miRNA regulation underlying these data sets is largely unknown. The method is easy to be implemented and can be used to investigate the miRNA effective regulation underlying the expression change profiles obtained from microarray experiments.
Systematic identification of cell cycle regulated transcription factors from microarray time series data
Chao Cheng, Lei M Li
BMC Genomics , 2008, DOI: 10.1186/1471-2164-9-116
Abstract: We propose a two-step method to identify the CCRTFs by integrating microarray cell cycle data with ChIP-chip data or motif discovery data. In S. cerevisiae, we identify 42 CCRTFs, among which 23 have been verified experimentally. The cell cycle related behaviors (e.g. at which cell cycle phase a TF achieves the highest activity) predicted by our method are consistent with the well established knowledge about them. We also find that the periodical activity fluctuation of some TFs can be perturbed by the cell synchronization treatment. Moreover, by integrating expression data with in-silico motif discovery data, we identify 8 cell cycle associated regulatory motifs, among which 7 are binding sites for well-known cell cycle related TFs.Our method is effective to identify CCRTFs by integrating microarray cell cycle data with TF-gene binding information. In S. cerevisiae, the TF-gene binding information is provided by the systematic ChIP-chip experiments. In other species where systematic ChIP-chip data is not available, in-silico motif discovery and analysis provide us with an alternative method. Therefore, our method is ready to be implemented to the microarray cell cycle data sets from different species. The C++ program for AC score calculation is available for download from URL http://leili-lab.cmb.usc.edu/yeastaging/projects/project-base/ webcite.Eukaryotic cell cycle is precisely controlled and regulated at the transcriptional, post-transcriptional, and post-translational level. To identify cell cycle regulated genes, several genome-wide analysis have been performed using microarray technologies [1-5]. In these studies, expression levels across the cell cycle were measured simultaneously for thousands of mRNA transcripts. In order to identify the subset of periodically expressed genes in the resulting microarray gene expression time series data, a number of computational approaches have been proposed, including Fourier analysis [2,6], partial least squares regressi
Compaccompact Dual-Mode Triple-Band Transversal Microstrip Bandpass Filter
Jing Li;Chao Lei Wei
PIER Letters , 2011, DOI: 10.2528/PIERL11072704
Abstract: A novel microstrip dual-mode tri-band bandpass filter is presented. The filter consists of an open stub loaded dual-mode resonator and two short stub loaded dual-mode resonators. By utilizing the odd- and even-mode resonance properties of the proposed dual-mode resonators and the introduced source-load coupling (S-L coupling), the filter is designed with two transmission zeros at both sides of each passband, which will improve the selectivity of the filter. To validate the design theory, one 100 MHz 3 dB absolute equal bandwidths dual-mode tri-band filter with three passbands located at the centre frequencies of 1.8, 2.4 and 5.0 GHz, respectively, is designed and fabricated. Both experimental results agree well with the simulations.
A probe-treatment-reference (PTR) model for the analysis of oligonucleotide expression microarrays
Huanying Ge, Chao Cheng, Lei M Li
BMC Bioinformatics , 2008, DOI: 10.1186/1471-2105-9-194
Abstract: We propose a Probe-Treatment-Reference (PTR) model to streamline normalization and summarization by allowing multiple references. We estimate parameters in the model by the Least Absolute Deviations (LAD) approach and implement the computation by median polishing. We show that the LAD estimator is robust in the sense that it has bounded influence in the three-factor PTR model. This model fitting, implicitly, defines an "optimal reference" for each probe-set. We evaluate the effectiveness of the PTR method by two Affymetrix spike-in data sets. Our method reduces the variations of non-differentially expressed genes and thereby increases the detection power of differentially expressed genes.Our results indicate that the reference effect is important and should be considered in microarray pre-processing. The proposed PTR method is a general framework to deal with the issue of reference selection and can readily be applied to existing normalization algorithms such as the invariant-set, sub-array and quantile method.Microarray is one of the most successful techniques in the field of functional genomics. As a high throughput approach, it provides a global gene expression profile of a living cell under certain conditions. The Affymetrix expression microarray is the most widely-used platform. It uses 11–20 probes which have 25 oligonucleotide bases, to represent one gene, and as a whole they are called a probe-set. Associated with each perfect match (PM) probe, a mis-match (MM) probe that differs only in the middle (13th) base is included in some expression arrays.From each array, we get fluorescence intensity of each probe after image processing. The estimation of gene expression from probe intensities is a statistical problem where much effort has been made. Among them are Affymetrix's MAS 5.0 [1], Li and Wong's dChip [2-4], and RMA [5-7]. Each method mainly consists of two modules: normalization and summarization. Normalization aims to reduce non-biological variations tha
Enthalpy-entropy compensation in protein unfolding
Lei Liu,Chao Yang,Qingxiang Guo
Chinese Science Bulletin , 2000, DOI: 10.1007/BF02898891
Abstract: Enthalpy-entropy compensation was found to be a universal law in protein unfolding based on over 3000 experimental data. Water molecular reorganization accompanying the protein unfolding was suggested as the origin of the enthalpy-entropy compensation in protein unfolding. It is indicated that the enthalpy-entropy compensation constitutes the physical foundation that satisfies the biological need of the small free energy changes in protein unfolding, without the sacrifice of the bio-diversity of proteins. The enthalpy-entropy compensation theory proposed herein also provides valuable insights into the Privalov’s puzzle of enthalpy and entropy convergence in protein unfolding.
Simulation Modeling on Dispersion Shaping and Harmonic Suppression in Helix Twt from 2 GHz to 6 GHz
Zhao-Jun Zhu;Chao Lei Wei
PIER C , 2012, DOI: 10.2528/PIERC12021504
Abstract: This paper describes the investigation of broadband interaction and harmonic suppression. A special dispersion shape used in broadband traveling-wave tubes (TWT) is obtained. The theoretical and simulation studies of negative dispersion are presented. On the basis of these studies, a broadband TWT used in microwave power module (MPM) is designed. Compared with the old TWT with flat dispersion, the new one with negative dispersion decreases the second harmonic content about 10 dB and improves the fundamental efficiency about 5% at the low end of the band. The new one operates with the beam voltage of 3600 V and current of 250 mA. The modified TWT is fabricated and the simulation results meet the measurements very well.
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