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Search Results: 1 - 10 of 85888 matches for " Q. Chen "
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Identification of a Highly Expressed 3-Hydroxy-3-Methylglutaryl-CoA Reductase Gene in the Root Tissue of Taraxacum kok-saghyz  [PDF]
Grisel Ponciano, Grace Q. Chen
American Journal of Plant Sciences (AJPS) , 2014, DOI: 10.4236/ajps.2014.524376
Abstract:
Kazakh dandelion (Taraxacum kok-saghyz, Tk) is a rubber-producing plant currently being investigated as a source of natural rubber for industrial applications. Like many other isoprenoids, rubber is a downstream product of the mevalonate pathway. The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR) enzyme catalyzes the conversion of 3-hydroxy-3-methylglutaryl-CoA to mevalonic acid, a key regulatory step in the MVA pathway. Such regulated steps provide targets for increases in isoprenoid and rubber contents via genetic engineering to increase enzyme activities. In this study, we identify a TkHMGR1 gene that is highly expressed in the roots of Kazakh dandelion, the main tissue where rubber is synthesized and stored. This finding paves the way for further molecular and genetic studies of the TkHMGR1 gene, and its role in rubber biosynthesis in Tk and other rubber-producing plants.
ACTA MATHEMATICA UNIVERSITATIS COMENIANAE
G.-Q. CHEN
ACTA MATHEMATICA UNIVERSITATIS COMENIANAE , 2001,
Abstract: . Some developments and efforts in designing and analyzing shock capturing algorithms and related numerical methods in computational fluid dynamics are reviewed. The importance of numerical viscosity in shock capturing algorithms is analyzed; the convergence and stability of some shock capturing algorithms are presented; the role of shock capturing algorithms in a mathematical existence theory is exhibited, especially for the compressible Euler equations for gas dynamics in one dimension and in multi-dimensions with spherical symmetry. Applications of shock capturing ideas to the compressible Navier-Stokes equations are also discussed.
Performance Characteristics of SALiM Isolator
H. Teng,Q. Chen
Lecture Notes in Engineering and Computer Science , 2009,
Abstract:
Theoretical Analysis and Numerical Simulation of Resonances and Stability of a Piecewise Linear-Nonlinear Vibration Isolation System
X. Gao,Q. Chen
Shock and Vibration , 2014, DOI: 10.1155/2014/803275
Abstract: A methodology is presented to study the resonance and stability for a single-degree-of-freedom (SDOF) system with a piecewise linear-nonlinear stiffness term (i.e., one piece is linear and the other is weakly nonlinear). Firstly, the exact response of the linear governing equation is obtained, and a modified perturbation method is applied to finding the approximate solution of the weakly nonlinear equation. Then, the primary and 1/2 subharmonic resonances are obtained by imposing continuity conditions and periodicity conditions. Furthermore, Jacobian matrix is derived to investigate the stability of resonance responses. Finally, the results of theoretical study are compared with numerical results, and a good agreement is observed. 1. Introduction Vibration isolation and shock absorbing have always been a hot research topic in engineering practice. A solid and liquid mixture (SALiM) vibration isolator was developed to isolate vibrations and shocks induced by heavy machines [1–3]. The stiffness of the SALiM isolator is piecewise linear-nonlinear in a quasi-static test [3]. That is, the isolator exhibits linear stiffness in some displacement region, beyond which the nonlinear stiffness is observed. Therefore, the elastic restoring force is continuous, but its first-order derivative at the turning point is discontinuous. In the past two decades, the majority of researches focused on the dynamics response, stability, bifurcation, and chaos of piecewise linear systems, such as piecewise bilinear systems or piecewise trilinear systems [4–8]. However, piecewise linear-nonlinear or even nonlinear-nonlinear systems have not received much attention, but many physical systems in fields of aerospace engineering, electric circuit, and so forth appear to be piecewise linear-nonlinear systems [9–12]. For nonsmooth stiffness systems, most approaches finding their steady state responses could be sorted into three groups including harmonic balance method (HBM) and its modified form, increment harmonic balance method (IHBM) [9, 10], classical approximate analytical methods like average method [4, 13–15], and the matching method [6, 7, 11, 16]. For instance, using HBM, Jin et al. investigated the response and stability of an unsymmetrical multiple-degree-of-freedom system with piecewise linear elastic elements [9], and for a more complex oscillator possessing a periodically time-varying and piecewise binonlinear restoring force function HBM is still applicable to its periodic motion [9, 17]. But like all harmonic balance techniques, the accuracy of the results obtained by
Contact angles in the pseudopotential lattice Boltzmann modeling of wetting
Q. Li,K. H. Luo,Q. J. Kang,Q. Chen
Physics , 2014, DOI: 10.1103/PhysRevE.90.053301
Abstract: In this paper, we aim to investigate the implementation of contact angles in the pseudopotential lattice Boltzmann modeling of wetting at a large density ratio. The pseudopotential lattice Boltzmann model [X. Shan and H. Chen, Phys. Rev. E 49, 2941 (1994)] is a popular mesoscopic model for simulating multiphase flows and interfacial dynamics. In this model, the contact angle is usually realized by a fluid-solid interaction. Two widely used fluid-solid interactions: the density-based interaction and the pseudopotential-based interaction, as well as a modified pseudopotential-based interaction formulated in the present paper, are numerically investigated and compared in terms of the achievable contact angles, the maximum and the minimum densities, and the spurious currents. It is found that the pseudopotential-based interaction works well for simulating small static (liquid) contact angles, however, is unable to reproduce static contact angles close to 180 degrees. Meanwhile, it is found that the proposed modified pseudopotential-based interaction performs better in light of the maximum and the minimum densities and is overall more suitable for simulating large contact angles as compared with the other two types of fluid-solid interactions. Furthermore, the spurious currents are found to be enlarged when the fluid-solid interaction force is introduced. Increasing the kinematic viscosity ratio between the vapor and liquid phases is shown to be capable of reducing the spurious currents caused by the fluid-solid interactions.
Structural Health Monitoring Using High-Frequency Electromechanical Impedance Signatures
Wei Yan,W. Q. Chen
Advances in Civil Engineering , 2010, DOI: 10.1155/2010/429148
Abstract: An overview of recent advances in electromechanical impedance- (EMI-) based structural health monitoring is presented in this paper. The basic principle of the EMI method is to use high-frequency excitation to sense the local area of a structure. Changes in impedance indicate changes in the structure, which in turn indicate that damages appear. An accurate EMI model based on the method of reverberation-ray matrix is introduced to correlate changes in the signatures to physical parameters of structures for damage detection. Comparison with other numerical results and experimental data validates the present model. A brief remark of the feasibility of implementing the EMI method is considered and the effects of some physical parameters on EMI technique are also discussed. 1. Introduction Over the last decades, structural health monitoring (SHM) has been recognized as a useful tool for improving the safety and reliability of structures and to thereby reduce their operational cost [1]. Many SHM techniques thus have been developed in the literature [2–4] to quantify and locate the damages in the structures, based on either the global or the local interrogation of the structures [5]. Although these SHM methods have their specific advantages for detecting damages in the structures, the existent drawbacks may limit their applications on some aspects. For example, in global dynamic techniques, it is well known that the structure is subjected to low-frequency excitations and only the first few mode shapes and their corresponding natural frequencies can be accurately extracted. Because localized damages find it hard to alter global parameters such as natural frequency, curvature mode shape, and mode shape data, only large damages can be detected. Meanwhile, signals obtained using these methods are more prone to contamination by ambient vibration noise at low frequencies less than 100?Hz particularly [5]. Other typical local techniques, such as ultrasonic techniques, acoustic emission, and impact echo testing, require expensive and sophisticated hardware as well as well-trained professional operators [6]. On the other hand, electromechanical impedance (EMI) based structural health monitoring has shown promising successes in monitoring and finding minor changes in structural integrity [5–9]. A key aspect of EMI method is the use of PZT patches as collocated sensors and actuators. To apply PZT as an actuator-sensor simultaneously, a PZT patch bonded to a structure is driven by a fixed alternating electric field. A surface charge is generated in response to an applied
Tea Polyphenols and Their Roles in Cancer Prevention and Chemotherapy
Di Chen,Q. Ping Dou
International Journal of Molecular Sciences , 2008, DOI: 10.3390/ijms9071196
Abstract: Many plant-derived, dietary polyphenols have been studied for their chemopreventive and chemotherapeutic properties against human cancers, including green tea polyphenols, genistein (found in soy), apigenin (celery, parsley), luteolin (broccoli), quercetin (onions), kaempferol (broccoli, grapefruits), curcumin (turmeric), etc. The more we understand their involved molecular mechanisms and cellular targets, the better we could utilize these “natural gifts” for the prevention and treatment of human cancer. Furthermore, better understanding of their structure-activity relationships will guide synthesis of analog compounds with improved bio-availability, stability, potency and specificity. This review focuses on green tea polyphenols and seeks to summarize several reported biological effects of tea polyphenols in human cancer systems, highlight the molecular targets and pathways identified, and discuss the role of tea polyphenols in the prevention and treatment of human cancer. The review also briefly describes several other dietary polyphenols and their biological effects on cancer prevention and chemotherapy.
Gene expression regulators —MicroRNAs
Fang Chen,James Q. Yin
Chinese Science Bulletin , 2005, DOI: 10.1360/982005-573
Abstract: A large class of non-coding RNAs found in small molecule RNAs are closely associated with the regulation of gene expression, which are called microRNA (miRNA). MiRNAs are coded in intergenic or intronic regions and can be formed into foldback hairpin RNAs. These transcripts are cleaved by Dicer, generating mature miRNAs that can silence their target genes in different modes of action. Now, research on small molecule RNAs has gotten breakthrough advance in biology. To discover miRNA genes and their target genes has become hot topics in RNA research. This review attempts to look back the history of miRNA discovery, to introduce the methods of screening miRNAs, to localize miRNA loci in genome, to seek miRNA target genes and the biological function, and to discuss the working mechanisms of miRNAs. Finally, we will discuss the potential important roles of miRNAs in modulating the genesis, development, growth, and differentiation of organisms. Thus, it can be predicted that a complete understanding of miRNA functions will bring us some new concepts, approaches and strategies for the study of living beings.
New evidents of tectonic uplift and trasform of movement style along Allao Shan-Red River fault zone
W. J. Chen,Q. Li
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891395
Abstract:
The rapid cooling of gangdese batholith(GB) and it“s tectonic implication
Q. Li,W. J. Chen
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891491
Abstract:
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