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427 results on '"Liu, Xu-Feng"'

15. Entropy Production of Open Quantum System in Multi-Bath Environment

Author

Cai, Cheng-Yun, Li, Sheng-Wen, Liu, Xu-Feng, and Sun, C. P.

Subjects
Condensed Matter - Statistical Mechanics, Quantum Physics
Abstract

We study the entropy production of an open quantum system surrounded by a complex environment consisting of several heat baths at different temperatures. The detailed balance is elaborated in view of the distinguishable channels provided by the couplings to different heat baths, and a refined entropy production rate is derived accordingly. It is demonstrated that the entropy production rates can characterize the quantum statistical property of the baths: the bosonic and fermionic baths display different behaviors in the high-temperature limit while they have the same asymptotic behavior at low temperature., Comment: 5 pages, 4 figures

Published
2014

17. Kinetic behavior of the general modifier mechanism of Botts and Morales with non-equilibrium binding

Author

Jia, Chen, Liu, Xu-Feng, Qian, Min-Ping, Jiang, Da-Quan, and Zhang, Yu-Ping

Subjects
Physics - Biological Physics, Physics - Chemical Physics, Quantitative Biology - Quantitative Methods
Abstract

In this paper, we perform a complete analysis of the kinetic behavior of the general modifier mechanism of Botts and Morales in both equilibrium steady states and non-equilibrium steady states (NESS). Enlightened by the non-equilibrium theory of Markov chains, we introduce the net flux into discussion and acquire an expression of product rate in NESS, which has clear biophysical significance. Up till now, it is a general belief that being an activator or an inhibitor is an intrinsic property of the modifier. However, we reveal that this traditional point of view is based on the equilibrium assumption. A modifier may no longer be an overall activator or inhibitor when the reaction system is not in equilibrium. Based on the regulation of enzyme activity by the modifier concentration, we classify the kinetic behavior of the modifier into three categories, which are named hyperbolic behavior, bell-shaped behavior, and switching behavior, respectively. We show that the switching phenomenon, in which a modifier may convert between an activator and an inhibitor when the modifier concentration varies, occurs only in NESS. Effects of drugs on the Pgp ATPase activity, where drugs may convert from activators to inhibitors with the increase of the drug concentration, are taken as a typical example to demonstrate the occurrence of the switching phenomenon., Comment: 19 pages, 10 figures

Published
2010
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18. Preparation and Application of Multiple Synergistic Flame Retardant Containing Nitrogen, Silicon and Phosphorus.

Author

CHEN Yong, LIU Xu-feng, WEN Shui-ping, CHEN Jian, LIANG Dong, and WU Jiao-yu

Subjects
FIREPROOFING agents, GRANULATION, POLYPROPYLENE, COMBUSTION, NITROGEN, COMPATIBILIZERS
Abstract

This article aims to prepare a nitrogen, silicon, and phosphorus multiple synergistic high-efficiency flame retardant and study its application performance. Firstly, allyl substituted melamine was synthesized by melamine powder and allyl bromide. After copolymerizing it with vinyltrimethoxysilane, a nitrogen-silicon containing melamine copolymer was obtained. Using the equal volume impregnation method, a certain mass of Type I ammonium polyphosphate (I-APP) powder is mixed with an equal volume of nitrogen-silicon containing melamine copolymer solution to prepare nitrogen silicon flame retardant copolymer coated I-APP flame retardant (MAPP). Pre mix polypropylene(PP) with a certain mass fraction of I-APP or MAPP flame retardant, and then perform melt blending, extrusion, and granulation in a twin-screw extruder to prepare PP flame retardant composites. Mechanical and vertical combustion tests were conducted on PP flame-retardant composites. The results showed that when MAPP was added up to 20%, it could reach the V-0 flame retardant level, while pure I-APP, even with 30% addition, remained below the V-0 level and had lower mechanical properties. It can be seen that the compatibility of I-APP coated with nitrogen silicon copolymer is better, and the synergistic flame retardant efficiency among nitrogen, silicon, and phosphorus is higher. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Manufacture and Preliminary Prototype Test of a HTS Suspension Electromagnet for Maglevs

Author

Zou, Chunlong, Liu, Xu-Feng, Zheng, Jinxing, Fu, Shan-Qiang, Han, Weitao, and Dong, Yujun

Abstract

A high-temperature superconducting coil (HTS) has been developed for a suspension electromagnet system of a maglev train. A preliminary prototype HTS coil module has been designed to replace one-six of the normal suspension electromagnet system used to verify the HTS performance. The HTS module consists of a warm yoke, an iron core, and two HTS coils. The HTS coil was connected by two symmetric winding pancakes, each of which consisted of six double-pancake coils wound with YBCO tapes. The prototype was produced and tested under vehicle suspension conditions. The results showed that the HTS suspension electromagnet module could produce 2 kN suspension force that can counteract self-gravity under 30 kA, and work steadily under maglev vibration conditions at 42 kA. The results indicate that the HTS suspension electromagnet module can reach the level of a practical project.

Published
2024
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37. A di-iron toluene-3,4-dithioate complex with monosubstituted 1,1′-bis(diphenylphosphino)ferrocene: preparation, characterization, and electrochemistry.

Author

Liu, Xu-Feng and Li, Yu-Long

Subjects
*ELECTROCHEMISTRY, *CYCLIC voltammetry, *ACETIC acid, *SINGLE crystals, *ELEMENTAL analysis, *FERROCENE
Abstract

Herein, this work presents the preparation and characterization of a di-iron toluene-3,4-dithiolate complex with monosubstituted 1,1′-bis(diphenylphosphino)ferrocene (dppf). The reaction of complex [Fe2(CO)6{μ-SC6H3(CH3)S}] (1) with dppf in refluxing toluene gave the monosubstituted analog [Fe2(CO)5(κ1-dppf){μ-SC6H3(CH3)S}] (2) in 50% yield. Complex 2 was identified by elemental analysis, spectroscopies including FT-IR, 1H, 31P{1H}, 13C{1H} NMR and single crystal X-ray diffraction analysis. Moreover, cyclic voltammetry revealed that complex 2 can reduce the protons to dihydrogen in the presence of an acetic acid as a proton source under the electrochemical conditions. [ABSTRACT FROM AUTHOR]

Published
2024
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39. Structural and electrochemical investigations of new mononuclear nickel(II) dithiolate complexes bearing a pendant amine

Author

Chen, Fei-Yan, Li, Jian-Rong, Liu, Xu-Feng, and Zhao, Pei-Hua

Subjects
Materials Chemistry, Physical and Theoretical Chemistry
Abstract

To further develop the biomimetic chemistry of [FeFe]- and [NiFe]-hydrogenases for the catalytic reduction of protons to hydrogen (H2), two new mononuclear Ni(II) ethanedithiolate complexes [{(Ph2PCH2)2NR}Ni(SCH2CH2S)] (R = tert-butyl (But), 1 and n-butyl (Bun), 2) with pendant amine-containing diphosphines were synthesized in moderate yields from the treatments of mononickel dichlorides [{(Ph2PCH2)2NR}NiCl2] with ethanedithiol (HSCH2CH2SH) with triethylamine (Et3N) as an acid-binding agent at room temperature. The as-prepared complexes 1 and 2 have been fully characterized by means of elemental analysis, nuclear magnetic resonance (NMR) spectrum, and X-ray crystallography. Further, the electrochemical properties of 1 and 2 are investigated in the absence or presence of acetic acid (HOAc) by using cyclic voltammetry (CV), suggesting that they can be considered as the active electrocatalysts for proton reduction to H2.

Published
2022
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