We report that the nanostructures of poly(styrene‐block‐4‐vinylpyridine) block copolymer (PS‐b‐P4VP) thin film on a wafer substrate can be re‐assembled by sequential vapor treatment using selected solvents. Metal or other inorganic nanoparticles that were randomly pre‐loaded inside or on the surface of PS‐b‐P4VP thin film could be pulled to the rim of PS and P4VP along with the movements of PS and P4VP blocks during the treatment. As a result, the patterned polymeric or inorganic/polymer composite nanoisland and nanoring arrays were fabricated.
A method is described for the simultaneous determination of paclitaxel and three related taxoids, 10-deacetylbaccatin III (10-DAB III), baccatin III, and cephalomannine, in the extracts from the needles of three Chinese yew species, Taxus cuspidata, T. chinensis, and T. media. SPE was applied as the sample preparation technique and RP-HPLC with a photodiode array detector (PAD) was used for the analysis of extract samples. The crude extracts were treated with an improved SPE cartridge packed with a combination of 1-vinyl-pyrrolidin-2-one and divinyl-benzene. The eluent was 75% methanol. The following separation was achieved with a gradient program on an HIQ SIL C18W column in a system of ACN/water within 60 min. The samples were detected by PAD at wavelengths of 232.1 nm for 10-DAB III, 229.8 nm for baccatin III and paclitaxel, and 223.9 nm for cephalomannine. The content of 10-DAB III, baccatin III, cephalomannine, and paclitaxel varied from 0.0277 to 0.0875, 0.0254 to 0.0405, 0.0715 to 0.2486, and 0.0996 to 0.1301 mg/g in fresh needles of the above yew species, respectively. The assay achieved good resolution in the separation between the four compounds, and it can be used for quality control or purity determination for those in bulk and pharmceutical dosage forms. 相似文献
To shorten scanning time and increase the feasibility of experimental results, we performed right coronary artery magnetic resonance angiography (CMRA) at 3.0 T using dual acceptance window weighting function in 25 normal subjects. We examined these subjects using conventional navigator with fixed gating window and 6 dual acceptance window weighted gating (DAWG) sequences with different central weighted ratio (CWR). Compared with the conventional navigator sequence, DAWG sequences with CWRs of 20% and 25% increased the scanning efficiency by 30% and 26% respectively (P<.05), while maintaining good image quality; further the corresponding scanning time decreased from 2.12–1.64 and 1.69 min, respectively (P<.05). However, CWRs less than 15% caused image degradation to some extent. The coronary artery lengths and diameters did not show statistically significant differences between the two techniques (P>.05). Briefly, to avoid the problems caused by low navigator efficiency and to maintain comparable image quality, the weighted gating parameters of 3 mm width central acceptance window and 15 mm width outer acceptance window with CWR between 20% and 25% are recommended for right CMRA at 3 T. 相似文献
