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156 results on '"Feng, X '

7. Steroidal Saponins from Dioscorea panthaica and Their Cytotoxic Activity

Author

Takashi Ikejima, M. Dong, B. X. Wang, X. Z. Feng, and L. J. Wu

Subjects
chemistry.chemical_classification, Ethanol, Traditional medicine, Protodioscin, Saponin, Tumor cells, General Medicine, Rhizome, carbohydrates (lipids), Dioscoreside E, chemistry.chemical_compound, chemistry, Dioscorea panthaica, Cytotoxic T cell
Abstract

A new steroidal saponin, dioscoreside E (1), and a known compound, protodioscin (2), were isolated from an ethanol extract of the rhizomes of Dioscorea panthaica. The structure of 1 was established as 3-O-[bis-alpha-L-rhamnopyranosyl-(1 --> 2 and 1 --> 4)-beta-D-glucopyranosyl]-26-O-beta-D-glucopyranosyl-20(R)-methoxy-25(R)-furosta-5,22(23)-diene-3beta,26-diol, on the basis of spectral and chemical evidence. Compounds 1 and 2 showed cytotoxic activity against a panel of tumor cell lines.

Published
2004
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8. Temperature Dependent X-Ray Diffraction Study on Gd5Sn4 Compound

Author

Zhong-Can Ou-Yang, Jinghua Liang, Hui Yang, Weifang Liu, Weiguo Chu, G. H. Rao, X. M. Feng, and Gang-yu Liu

Subjects
Diffraction, Magnetic structure, Condensed matter physics, Rietveld refinement, Chemistry, Mechanical Engineering, Cell volume, Metals and Alloys, Analytical chemistry, Crystal structure, General Medicine, Thermal expansion, Magnetization, Mechanics of Materials, X-ray crystallography, Materials Chemistry, Curie temperature, Structural transition
Abstract

The structure and the magnetic properties of the Gd5Sn4 compound have been investigated by means of X-ray diffraction (XRD) and magnetization measurements. Temperature dependent XRD investigation reveals that there is no structural transition around the temperature at which the first-order magnetic transition occurs in this compound, i.e. the compound retains the Sm5Ge4-type structure from 80 K( T-C), which is different from the Gd-5(Si, Ge)(4) system. Based on the Rietveld refinement of the XRD pattern of Gd5Sn4 compound, we show that the unit cell volume exhibits a dip near the Curie temperature, i.e. a negative coefficient of thermal expansion alpha approximate to -1.5 x 10(-4) K-1 from 82 to 90 K and a positive coefficient alpha approximate to 2.2 x 10(-4) K-1 from 90 to 98 K. The coefficient of thermal expansion from 98 to 298 K is only 2.5 x 10(-5) K-1. (C) 2003 Elsevier B.V. All rights reserved.

Published
2004
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10. Formation, Structure and Magnetic Properties of SmCo9.8V2.2

Author

X. M. Feng, G. H. Rao, Zhong-Can Ou-Yang, Hui Yang, Weifang Liu, Gang-yu Liu, and Jinghua Liang

Subjects
Diffraction, Curie–Weiss law, Magnetic structure, Magnetic domain, Condensed matter physics, Chemistry, Mechanical Engineering, Enthalpy, Metals and Alloys, General Medicine, Magnetocrystalline anisotropy, Magnetic anisotropy, Magnetization, Tetragonal crystal system, Nuclear magnetic resonance, Atomic radius, Ferromagnetism, Mechanics of Materials, Materials Chemistry, Curie temperature
Abstract

The structure and magnetic properties of the SmCo9.8V2.2 compound were investigated by means of X-ray diffraction analysis and magnetic measurement. SMCo9.8V2.2 crystallizes in a tetragonal structure with space group 14/mmm. The lattice parameters are a = 8.3802(1) Angstrom and c =4.7047(1) Angstrom. Both the atomic size effect and enthalpy effect favor a preferential occupation of V on the 8i site. Magnetic measurements indicate that the SmCo9.8V2.2 compound is ferromagnetic with a Curie temperature of 360 K. The easy magnetization direction of SmCo9.8V2.2 is perpendicular to the c-axis. The saturation magnetization and the magnetocrystalline anisotropy field of the SmCo9.8V2.2 compound at 5 K are 35.4 emu/g and 77 kOe, respectively. (C) 2003 Elsevier B.V. All rights reserved.

Published
2004
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11. Structural Transition and Atomic Ordering in the Non-Stoichiometric Double Perovskite Sr2FexMo2-xO6

Author

Gang-yu Liu, X. M. Feng, Hui Yang, Weifang Liu, G. H. Rao, Jinghua Liang, and Zhong-Can Ou-Yang

Subjects
Diffraction, Chemistry, Rietveld refinement, Mechanical Engineering, Metals and Alloys, General Medicine, Crystal structure, Crystallography, Tetragonal crystal system, Mechanics of Materials, Lattice (order), X-ray crystallography, Materials Chemistry, Double perovskite, Structural transition, Powder diffraction, Stoichiometry
Abstract

The structural transition and atomic ordering of a new series of ordered double perovskite oxides Sr2FexMo2-xO6 (0.8 less than or equal to x less than or equal to 1.5) have been studied by X-ray powder diffraction (XRD). Rietveld refinement of the powder diffraction profiles indicates that the crystal structure of the compounds Sr2FexMo2-xO6 changes from a tetragonal I4/mmm lattice to a cubic Fm(3)over-bar-m lattice around x = 1.2 and the lattice parameters decrease slightly as Fe content increases. The degree of ordering in Sr2FexMo2-xO6 exhibits a maximal at x = 0.95 and decreases as x deviates from 0.95. (C) 2002 Elsevier Science B.V. All rights reserved.

Published
2003
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