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961.
使用密度泛函理论B3LYP方法和6-31G(d,p)、6-31+G(d,p)、6-311G(d,p)及6-311+G(d,p)基组,分别对2-C5H10+和1-C5H10+的各种构象进行了几何构型优化,并用B3LYP/6-311G(d,p)进行了频率分析计算.计算预言1-C5H10+具有非平面构型,与以往报导的从头算计算结论相反.在两个自由基阳离子的各种构象的B3LYP几何构型上,进行了B3LYP和UMP2(full)方法的超精细偶合常数计算,得到了比以往更好的结果. 相似文献
962.
UVB irradiation of normal human skin favors the development of type-2 T-cells in vivo and in primary dermal cell cultures 总被引:1,自引:0,他引:1
Di Nuzzo S Sylva-Steenland RM Koomen CW Nakagawa S van Breemen M de Rie MA Das PK Bos JD Teunissen MB 《Photochemistry and photobiology》2002,76(3):301-309
To determine the effect of UVB exposure on the balance of type-1 or type-2 T-cells in skin, we examined the expression of key markers interferon (IFN)-gamma and interleukin (IL)-4 in cryostat sections. IFN-gamma mRNA was clearly detectable in nonirradiated control skin, and IFN-gamma protein was found in 2% of the dermal CD3pos T-cells, whereas IL-4 mRNA was hardly detectable, and no IL-4 protein was found. In contrast, IL-4 mRNA expression increased upon irradiation, and IL-4 was found in 2% of the T-cells at day 2 after UVB-exposure. Concomitantly, IFN-gamma mRNA expression decreased, and IFN-gamma protein became absent. We also analyzed T-cells present in primary dermal cell cultures, which were used as an in vitro equivalent of the in vivo situation. As compared with T-cells from control skin, T-cells in dermal cell cultures from UVB-exposed skin displayed an increased IL-4 and decreased IFN-gamma expression. No such skewing occurred when the T-cells from irradiated skin were cloned in the absence of a dermal microenvironment. Except for an occasional positive T-cell, type-1-associated cell-surface markers (CCR5, CXCR3) or type-2 markers (CCR3, CD30, CRTH2) were undetectable in situ. But these markers were expressed on cultured dermal T-cells from UVB-exposed and control skin at a comparable level, but did not correlate with the IFN-gamma and IL-4 production. Altogether, UVB-induced changes of the dermal microenvironment favor the development of type-2 T-cells. 相似文献
963.
The photostimulated reaction of halonaphthalene with a series of carbanions derived from,propionic acid derivatives in liquid ammonia led to the naphthylation at a-carbon of the carbanions inan isolated yield ranging from 25% to 86%.In all cases,the dehalonaphthalenes were found to,be by-products and the reaction was inhibited by p-dinitrobenzere.An electron transfer from thecarbanion to the halonaphthalene followed by ejection of halogen led to naphtbyl radical,as predictedby comparing the LUMOs of the carbanions and the halonaphthalenes,was involved in the process.Absence of the alkylnaphthalene and 1,2-dinaphthylalkane in the products indicates the smoothelectron transfer between(Naph-Nu)~+ and Naph-X.C-vs.O-naphthylation is fully addressed interms of MNDO calculations and acid-base principle. 相似文献
964.
The uniform transparent TiO2/SiO2 nanometer composite thin films were prepared via sol-gel method on the soda lime glass substrates, and were characterized by X-ray photoelectron spectroscopy (XPS), FTIR spectroscopy, UV-VIS spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface areas. It was found that the addition of SiO2 to TiO2 thin films could suppress the grain growth of TiO2 crystal and increase the hydroxyl content of the surface of TiO2 films. The photocatalytic activity of the as-prepared TiO2/SiO2 composite thin films increases for SiO2 content of less than 5 mol%. 相似文献
965.
Massey University is a world-leading university in remote-instruction, online and mixed teaching based on the Stream teaching platform. This paper analyzed the advantages of the Stream teaching platform, resource utilization, course format, teaching team cooperation and course evaluation in Massey University. The paper also analyzed the enlightenment of teaching experience of Massey University to undergraduate teaching. During the outbreak of COVID-19 epidemic, drawing on Massey's experience, combined with the rapid development of information technology in China, the teaching team of organic chemistry adopted the multi-teaching strategy of "teacher-centered and student-centered", and the teaching mode of "teacher-led and self-taught by students". The online teaching practice of organic chemistry was carried out in agriculture university. It has been demonstrated that this model can effectively improve teaching effects. 相似文献
966.
Uniform-sized molecularly imprinted polymer (MIP) beads were prepared using a one-step swelling and polymerization method. The obtained sulfamethazine (SMZ)-imprinted polymer showed high affinity and selectivity toward SMZ and other structurally related sulfonamides in acetonitrile or water-acetonitrile mobile phases, particularly in high aqueous systems. The column performance of the MIPs for SMZ and its analogues could be improved by elevating the column temperature and optimizing the flow rate. The hydrogen-bonding effect plays a significant role in the recognition process of SMZ-imprinted polymer systems in organic media, while the ion-exchange effect, as well as hydrophobic effect, dominates the retention mechanism in aqueous-rich media, in addition to shape recognition. 相似文献
967.
968.
用两束脉冲染料激光进行了CO的光学双共振四光子电离, 获得了转动分辩的CO A~(1Π)←X~(1Σ~+)和B~(1Σ~+)←A~(1Π)跃迁的光谱。观察到了在此2+1光子相继吸收中特有的选择定则。动力学研究表明CO基态到A~(1Π)态的双光子吸收是速率决定步骤, 其吸收截面约为1×10~(-49) cm~4 s。还测定了A~(1Π)态的单态转动传能截面。对于宇称指数e守恒、△J×±1的过程的截面约为0.05 nm; 随△J值增大而减小。对相同的△J, e正负变号的过程的截面总是小于e不变过程的截面。 相似文献
969.
970.
Bing Yang Jianfeng Zhao Zepeng Wang Zhenlin Yang Zongqiong Lin Yanni Zhang Jiewei Li Linghai Xie Zhongfu An Hongmei Zhang Jiena Weng Wei Huang 《中国化学快报》1990,30(11):1969-1973
As facile,green,low-cost as possible:One more electron-deficient azaacene (TCAF) with deep LUMO (-4.52 eV), strong electronic affinity,excellent yield,and simple purification procedure was successfully created and explored as good electron injection material.It is believed TCAF would be a promising and pervasive acceptor material and bring in more significant achievements to green and sustainable organic electronics including OLEDs,OFETs,OPVs, and perovskite solar cells,etc. 相似文献