Biomedical subjects

L L He

Publications and source records attributed to L L He.

4 recordsLinked to original sources

PubMed2006

Simultaneous determination of Gastrodin and Ligustrazine hydrochloride in dog plasma by gradient high-performance liquid chromatography.

A novel reversed-phase HPLC method was developed for the simultaneous determination of Gastrodin (Gas) and Ligustrazine hydrochloride (LZH) in dog plasma after oral administration of the preparation 'Tianxiong Capsule'. The assay involves deproteinization, extraction and subsequent detection with a gradient solvent system at two different wavelengths. Retention times were 10.6 and 18.9 min for Gas and LZH, respectively. Linear responses were observed over a wide range (0.40-200.0 microg/ml for Gas and 0.0999-39.96 microg/ml for LZH) in plasma. The mean intra- and inter-assay variation coefficients were 2.7 and 3.4% for Gas and 3.4 and 4.2% for LZH, respectively. The average extract recoveries were 76.77% for Gas and 75.8% for LZH. This assay has been successfully used to provide pharmacokinetic data for Gastrodin with oral administration of Tianxiong capsules.

Administration, Oral↗

PubMed2004

HRTEM analysis of nanocrystallization during uniaxial compression of a bulk metallic glass at room temperature.

Nanocrystallization during deformation of metallic glass at room temperature has significant implications to understand its deformation mechanism. We present here direct high-resolution transmission electron microscopy (HRTEM) observations of nanocrystallization in a Zr(55)AI(10)Ni(5)Cu(30) bulk metallic glass (BMG) fractured by uniaxial compression at room temperature. The formed nanocrystallites are Zr(2)Cu, with the average diameter of less than 10nm, and are distributed within the round-like regions of localized plastic deformation. We also show direct evidence of atomic neighbor distance increases associated with the shrinkage and broadening of diffused ring pattern from local deformed areas, which may enhance atomic mobility so that nanocrystallization occurred. Our results demonstrate that the origin of the room-temperature deformation of BMG can be attributed to the local atomic spacing increases induced by localization of plastic flow under uniaxial compression test.

Journal Article↗

PubMed2002

Reversible structural transition in epitaxial manganite film.

A reversible structural transition of an epitaxial La(2/3)Sr(1/3)MnO3 film deposited on a LaAlO3 substrate has been investigated by means of in situ high-resolution transmission electron microscopy and electron diffraction, combined with image and diffraction calculations. We observe that the crystallographic symmetry of the film can be lowered via electron beam irradiation, leading to a rhombohedral-monoclinic transition. This transition can be attributed to the cooperating effect of the mismatch stress and the irradiation-induced thermal stress.

Journal Article↗

PubMed1998

Structural evolution in boron nitrides during the hexagonal-cubic phase transition under high pressure at high temperature.

Structural evolution during the phase transition from h (hexagonal)- to c (cubic)-boron nitrides (BN) under high pressure (6.5-7.7 GPa) at high temperature (1,700-2,150 degrees C) was examined by using high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). At the initial stage of the evolution, some starting h-BN plates were strongly folded, while others were slightly bent. As a result, a strong texture was formed. HRTEM revealed that the interplanar distance between sp2 sheets became slightly shortened and they were slightly sheared to each other during the folding and bending. As a result, m (monoclinic)-BN was formed near the folding plane with lattice parameters; a = 0.433 nm, b = 0.250 nm, c = 0.32-0.33 nm, and beta = 90-92 degrees. In a succeeding stage, the value of beta increased to 92-95 degrees. c-BN grains appeared with nano-scale twins and sometimes partly included wurtzite-type BN. They started to grow with secondary twins at higher temperature. EELS analysis revealed that the band structure of sp2 sheets changed during the transition from h-BN to m-BN; the density of state for the pi* bond became prominently high in m-BN as compared to that in h-BN.

Animals↗