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Search Results: 1 - 10 of 42558 matches for " Jianhan Xu "
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The Performance Evaluation and Field Application of Low Temperature Coalbed Gas Clean Fracturing Fluid  [PDF]
Jianhan Xu, Jiao Ka, Shoucheng Wen, Bin Liu, Jidan Tang
Open Journal of Yangtze Oil and Gas (OJOGas) , 2018, DOI: 10.4236/ojogas.2018.34020
Abstract: Clean fracturing fluid has many advantages, such as strong sand carrying capacity, strong ability to high generation and low friction, etc. However, the temperature of coalbed gas in the shallow part is low (25°C to 35°C). And there are no liquid hydrocarbons or no large amount of free water in the reservoir, which can make fracturing fluid break. The difficulty to break the clean fracturing fluid could result in serious reservoir damage during fracturing. This paper introduces many breakers for cleaning fracturing fluid. And the performances of those breakers have been evaluated in the condition of low temperature. On the base of research, the breaker for clean fracturing fluid is recommended for coalbed gas in the shallow part. The breaker can break clean fracturing fluid completely in low temperature of 25°C. At the same time, the degree of damage caused by fracturing fluid is evaluated. The damage rate of fracturing fluid is only 11%. The system of cleaning fracturing fluid has been applied in Qinshui Basin of Shanxi Province. The field experiment has achieved good results.
A Proposal for Burger King to Take Further Steps in Mainland China
Jianhan Zhao
International Journal of Business and Management , 2009, DOI: 10.5539/ijbm.v4n7p31
Abstract: Through an investigation involving people’s attitude towards Burger King in mainland China, Qualitative analysis was made and some problems emerged such as the promotion deficiency. We rendered possible explanations and feasible suggestions in this paper.
Force-Induced Unfolding Simulations of the Human Notch1 Negative Regulatory Region: Possible Roles of the Heterodimerization Domain in Mechanosensing
Jianhan Chen, Anna Zolkiewska
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0022837
Abstract: Notch receptors are core components of the Notch signaling pathway and play a central role in cell fate decisions during development as well as tissue homeostasis. Upon ligand binding, Notch is sequentially cleaved at the S2 site by an ADAM protease and at the S3 site by the γ-secretase complex. Recent X-ray structures of the negative regulatory region (NRR) of the Notch receptor reveal an auto-inhibited fold where three protective Lin12/Notch repeats (LNR) of the NRR shield the S2 cleavage site housed in the heterodimerization (HD) domain. One of the models explaining how ligand binding drives the NRR conformation from a protease-resistant state to a protease-sensitive one invokes a mechanical force exerted on the NRR upon ligand endocytosis. Here, we combined physics-based atomistic simulations and topology-based coarse-grained modeling to investigate the intrinsic and force-induced folding and unfolding mechanisms of the human Notch1 NRR. The simulations support that external force applied to the termini of the NRR disengages the LNR modules from the heterodimerization (HD) domain in a well-defined, largely sequential manner. Importantly, the mechanical force can further drive local unfolding of the HD domain in a functionally relevant fashion that would provide full proteolytic access to the S2 site prior to heterodimer disassociation. We further analyzed local structural features, intrinsic folding free energy surfaces, and correlated motions of the HD domain. The results are consistent with a model in which the HD domain possesses inherent mechanosensing characteristics that could be utilized during Notch activation. This potential role of the HD domain in ligand-dependent Notch activation may have implications for understanding normal and aberrant Notch signaling.
How to be Competitive in Chinese Automobile Industry
Jianhan Zhao,Lei Gao
International Journal of Economics and Finance , 2009, DOI: 10.5539/ijef.v1n2p144
Abstract: Chinese market has a great demand for foreign cars, and a great many foreign automobile companies are competing for their market shares here. The most representative ones are Volkswagen and Honda, they adoped different market strategies and they both suffered some success and failures With so many competitions, the future of Chinese automobile industry is hard to predict.
Residual Structures, Conformational Fluctuations, and Electrostatic Interactions in the Synergistic Folding of Two Intrinsically Disordered Proteins
Weihong Zhang,Debabani Ganguly,Jianhan Chen
PLOS Computational Biology , 2012, DOI: 10.1371/journal.pcbi.1002353
Abstract: To understand the interplay of residual structures and conformational fluctuations in the interaction of intrinsically disordered proteins (IDPs), we first combined implicit solvent and replica exchange sampling to calculate atomistic disordered ensembles of the nuclear co-activator binding domain (NCBD) of transcription coactivator CBP and the activation domain of the p160 steroid receptor coactivator ACTR. The calculated ensembles are in quantitative agreement with NMR-derived residue helicity and recapitulate the experimental observation that, while free ACTR largely lacks residual secondary structures, free NCBD is a molten globule with a helical content similar to that in the folded complex. Detailed conformational analysis reveals that free NCBD has an inherent ability to substantially sample all the helix configurations that have been previously observed either unbound or in complexes. Intriguingly, further high-temperature unbinding and unfolding simulations in implicit and explicit solvents emphasize the importance of conformational fluctuations in synergistic folding of NCBD with ACTR. A balance between preformed elements and conformational fluctuations appears necessary to allow NCBD to interact with different targets and fold into alternative conformations. Together with previous topology-based modeling and existing experimental data, the current simulations strongly support an “extended conformational selection” synergistic folding mechanism that involves a key intermediate state stabilized by interaction between the C-terminal helices of NCBD and ACTR. In addition, the atomistic simulations reveal the role of long-range as well as short-range electrostatic interactions in cooperating with readily fluctuating residual structures, which might enhance the encounter rate and promote efficient folding upon encounter for facile binding and folding interactions of IDPs. Thus, the current study not only provides a consistent mechanistic understanding of the NCBD/ACTR interaction, but also helps establish a multi-scale molecular modeling framework for understanding the structure, interaction, and regulation of IDPs in general.
Intrinsically Disordered Proteins in a Physics-Based World
Timothy H. Click,Debabani Ganguly,Jianhan Chen
International Journal of Molecular Sciences , 2010, DOI: 10.3390/ijms11125292
Abstract: Intrinsically disordered proteins (IDPs) are a newly recognized class of functional proteins that rely on a lack of stable structure for function. They are highly prevalent in biology, play fundamental roles, and are extensively involved in human diseases. For signaling and regulation, IDPs often fold into stable structures upon binding to specific targets. The mechanisms of these coupled binding and folding processes are of significant importance because they underlie the organization of regulatory networks that dictate various aspects of cellular decision-making. This review first discusses the challenge in detailed experimental characterization of these heterogeneous and dynamics proteins and the unique and exciting opportunity for physics-based modeling to make crucial contributions, and then summarizes key lessons from recent de novo simulations of the structure and interactions of several regulatory IDPs.
Electrostatically Accelerated Encounter and Folding for Facile Recognition of Intrinsically Disordered Proteins
Debabani Ganguly,Weihong Zhang,Jianhan Chen
PLOS Computational Biology , 2013, DOI: 10.1371/journal.pcbi.1003363
Abstract: Achieving facile specific recognition is essential for intrinsically disordered proteins (IDPs) that are involved in cellular signaling and regulation. Consideration of the physical time scales of protein folding and diffusion-limited protein-protein encounter has suggested that the frequent requirement of protein folding for specific IDP recognition could lead to kinetic bottlenecks. How IDPs overcome such potential kinetic bottlenecks to viably function in signaling and regulation in general is poorly understood. Our recent computational and experimental study of cell-cycle regulator p27 (Ganguly et al., J. Mol. Biol. (2012)) demonstrated that long-range electrostatic forces exerted on enriched charges of IDPs could accelerate protein-protein encounter via “electrostatic steering” and at the same time promote “folding-competent” encounter topologies to enhance the efficiency of IDP folding upon encounter. Here, we further investigated the coupled binding and folding mechanisms and the roles of electrostatic forces in the formation of three IDP complexes with more complex folded topologies. The surface electrostatic potentials of these complexes lack prominent features like those observed for the p27/Cdk2/cyclin A complex to directly suggest the ability of electrostatic forces to facilitate folding upon encounter. Nonetheless, similar electrostatically accelerated encounter and folding mechanisms were consistently predicted for all three complexes using topology-based coarse-grained simulations. Together with our previous analysis of charge distributions in known IDP complexes, our results support a prevalent role of electrostatic interactions in promoting efficient coupled binding and folding for facile specific recognition. These results also suggest that there is likely a co-evolution of IDP folded topology, charge characteristics, and coupled binding and folding mechanisms, driven at least partially by the need to achieve fast association kinetics for cellular signaling and regulation.
Fabrication and photoluminiscent properties of titanium oxide nanotube arrays
Fang, Dong;Huang, Kelong;Liu, Shuqin;Huang, Jianhan;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000600002
Abstract: an array of vertically aligned titanium oxide nanotubes was successfully grown on the surface of a titanium substrate by the anodization technique. the nanotubes were characterized by scanning electron microscopy (sem), powder x-ray diffractometry (xrd), raman spectroscopy and photoluminescence spectroscopy (pl). the results indicate that the size of the titanium oxide nanotube is greatly dependent on the applied voltage, and its photoluminescence properties are strongly influenced by the crystal structure. in addition, it is shown that quantum size effects are present in the optical properties of tio2 nanotubes.
MIMO Beamforming in Millimeter-Wave Directional Wi-Fi
Keang-Po Ho,Shi Cheng,Jianhan Liu
Mathematics , 2014,
Abstract: Beamforming is indispensable in the operation of 60-GHz millimeter-wave directional multi-gigabit Wi-Fi. Simple power method and its extensions enable the transmitting and receiving antenna arrays to form a beam for single spatial stream. To further improve the spectral efficiency in future 60-GHz directional Wi-Fi, alternating least square (ALS) algorithm can form multiple beams between the transmitter and receiver for multi-input-multi-output (MIMO) operations. For both shared and split MIMO architecture, the ALS beamforming algorithm can be operated in both frequency-flat and frequency-selective channels. In the split architecture, MIMO beamforming approximately maximizes the capacity of the beam-formed MIMO channel.
A FastAlgorithm ofSnakewith theShape Factor
一种具有形状约束的快速Snake类算法

Liu Jianhan,Liang Dequn,Wang Hongguang,Tian Yuan,
刘剑函
,梁德群

中国图象图形学报 , 1999,
Abstract: 动态包络算法在希望获取目标的精确轮地是经常使用的一个算法,但在以往的Snake算法中,由于没有考虑到其总体的形状因素,加之一些干扰的影响,其包络点很可能收敛于错误的位置。
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