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In this paper, pure squeeze elastohydrodynamic lubrication motion of circular contacts with couple stress lubricant is explored at impact loading. On the basis of microcontinuum theory, the transient modified Reynolds equation is derived. Then it is solved simultaneously with the elasticity deformation equation and ball motion equation, thus obtaining the transient pressure profiles, film shapes, normal squeeze velocities, and accelerations. The simulation results reveal that the effect of the couple stress is equivalent to enhancing the lubricant viscosity, which would also enlarge the damper effect. Therefore, as the characteristic length of the couple stress fluid increases, the pressure spike and the dimple form earlier, the maximum pressure and the film thickness increase, and the diameter of the dimple, the rebounding velocity, the maximum value of the relative impact force, and the acceleration decrease. Furthermore, the fact that the contact central pressure for a ball impacting and rebounding from a lubricated surface reached two peaks during the total impact period is proved numerically in this analysis. As the effect of couple stress increases, the first and second peaks form earlier; as the total impact time decreases, the pressure of the first peak increases and that of the second peak decreases. Moreover, the phase shift between the time of the peak value of the squeeze acceleration and the zero value of the squeeze velocity increases with increasing the characteristic length of the couple stress fluid.

The ethanolic extract of Elephantopus mollis yielded three novel cytotoxic antitumor germacranolides, molephantin, molephantinin, and phantomolin. The extract also yielded three inactive known triterpenes, beta-amyrin acetate, lupeol acetate, and epifriedelanol, as well as stigmasterol. The structure and stereochemistry of the cytotoxic antitumor agents molephantin, molephantinin, and phantomolin were determined on the basis of chemical transformations and spectral evidence. Preliminary in vivo tumor assays indicated that molephantinin and phantomolin were potent inhibitors of Ehrlich ascites carcinoma and Walker 256 carcinosarcoma. Molephantinin also showed significant antileukemic activity in the P-388 lymphocytic leukemia screen.

Bioassay-directed isolation of the antitumor extract of Wikstroemia indica (Thymelaeaceae) has led to the characterization of tricin, kaempferol-3-O-beta-D-glucopyranoside, and (+)-nortrachelogenin as the major antileukemic constituents. In addition, daphnoretin was identified as the potent antitumor principle in vivo against the Ehrlich ascites carcinoma growth in mice.

In vivo P-388 assay-directed fractionation of an active extract of Daphne genkwa (Yuan Huā) has led to the isolation and characterization of a new antileukemic principle. genkwadaphnin.

Bioassay-directed isolation of an antileukemic extract of Aglaia odorata has led to the characterization of (−)-odorinol, a new diamide demonstra

A chloroform extract of the whole plant of Anaphalis morrisonicola HAY. showed significant antitumor activity against Ehrlich ascites carcinoma, Walker 256 carcinosarcoma, and P-388 lymphocytic leukemia. Systematic fractionation of the extract led to isolation and characterization of helenalin, a pseudoguaianolide, as the major active principle.

A new lignan, (+)-aretigenin has been isolated from the roots of Wikstroemia indica (Nan-Ling-Jao-Hua) and identified as 8(R) 8′(S)-4′-hydroxy-3, 4,3′-trimethoxylignan-olid (9, 9′) on the basis of spectral evidence as well as a direct comparison with its enantiomer, (−)-arctigenin.

A chloroform extract of the whole plant of Anaphalis morrisonicola HAY, showed significant antitumor activity against Ehrlich ascites carcinoma, Walker 256 carcinosarcoma, and P-388 lymphocytic leukemia. Systematic fractionation of the extract led to isolation and characterization of helenalin, a pseudoguaianolide, as the major active principle.

The structure and stereochemistry (exclusive of the configuration of the methyl group at C-4) of bruceoside-A, a novel antileukaemic quassinoid glycoside isolated from Brucea javanica(Linn) Merr., have been established from chemical transformations, correlations, and spectral analyses.

The structure and absolute configuration of molephantin, a novel cytotoxic germacranolide isolated from Elephantopus mollis H.S.K., have been determined on the basis of physicochemical data and X-ray crystallographic analysis.