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951.
Chow’s Theorem for Semi-abelian Varieties and Bounds for Splitting Fields of Algebraic Tori 下载免费PDF全文
A theorem of Chow concerns homomorphisms of two abelian varieties under a primary field extension base change. In this paper, we generalize Chow's theorem to semi-abelian varieties. This contributes to different proofs of a well-known result that every algebraic torus splits over a finite separable field extension. We also obtain the best bound for the degrees of splitting fields of tori. 相似文献
952.
粘性可压混合层时间稳定性对称紧致差分求解 总被引:2,自引:0,他引:2
基于可压扰动方程组的一阶改型 ,将高精度对称紧致格式引入边值法数值线性稳定性分析。对所获非线性离散特征值问题给出了一个通用形式二阶迭代局部算法 ,实现了时间模式和空间模式的统一求解 ,并将扰动特征值及其特征函数同时得到。据此分析了可压平面自由混合层时间稳定性 ,涉及二维 /三维扰动波、粘性 /无粘扰动波、第一 /第二模态、特征函数、伪特征值谱等。研究表明 ,压缩性效应和粘性效应对最不稳定扰动波数和增长率呈相似的减抑作用 ;在 Mc=1附近 ,从高波数段开始 ,粘性效应可强化二维不稳定扰动波由第一模态向第二模态的过渡 相似文献
953.
Xing Hai Li Xin Ling Yang Xiao Mei Liang Zhen Peng Kai Yun Ling Fu Heng Chen Dao Quan Wang 《中国化学快报》2007,18(12):1476-1478
α-Chlorocycloalkanones(Ⅳ) were synthesized from cycloalkanones via potassiumα-oxocycloalkylsulfonates(Ⅱ).A two-step mechanism was proposed to explain the formation ofⅣfromⅡ. 相似文献
954.
Chunhua Fu Changshun Ruan Ya Fu Yuanliang Wang 《Polymer Degradation and Stability》2010,95(4):485-490
The multi-arm star polymer (ESOPLA) was obtained by ring-opening polymerization of dl-lactide using multifunctional epoxidized soybean oil (ESO) as an initiator in the presence of a stannous actuate (SnOct2) catalyst. Gel permeation chromatography with multi-angle laser light scattering (GPC-MALLS), FTIR, 1H NMR, thermal analysis and in vitro degradation were used to qualitatively characterize the synthesized polymers. The results revealed that ESO plays an important role in increasing the molecular weight, polymerization rate and monomer conversion rate. Degradation analysis demonstrated that the decrease in molecular weight and the weight loss ratio of the star-shaped ESOPLA were lower than that of linear poly(dl-lactide) (PDLLA). The surface topography of pre- and post-degradation materials was characterized by scanning electron microscopy (SEM). These SEM images showed that the linear PDLLA films underwent water erosion more readily than the star-shaped polymer films. 相似文献
955.
W Zhu X Zhai Q Fu F Guo M Bai J Wang H Wang P Gong 《Chemical & pharmaceutical bulletin》2012,60(8):1037-1045
Three series of 4-morpholinothieno[3,2-d]pyrimidine derivatives containing arylmethylene hydrazine moiety (11a-f, 13a-k and 15a-h) were synthesized and their chemical structures as well as the relative stereochemistry were confirmed. The synthesized compounds were evaluated for their cytotoxicity against three cancer cell lines (H460, HT-29, MDA-MB-231). Most of them exhibited moderate to significant cytotoxicity and high-selectivity against one or more cell lines, especially compounds 11c, 13b, 15f and 15g possessing dramatically increased cytotoxicity as compared with the positive controls, which were further evaluated for six other cancer cell lines and one normal cell line. The most promising compound 11c, bearing 3,4-methylenedioxy phenyl group, showed remarkable cytotoxicity against H460, HT-29 and MDA-MB-231 cell lines with IC50 values of 0.003?μM, 0.42?μM and 0.74?μM, which was 1.6- to 290-fold more potent than GDC-0941. 相似文献
956.
采用新工艺路线合成高熔点磷酸酯阻燃剂———对苯二酚双(二苯基磷酸酯)(HDP).首先采用对苯二酚和三氯氧磷合成中间产物,再将中间产物与苯酚反应,经分离纯化得到产品HDP,收率达到90%以上,常温下为白色固体.采用傅里叶红外光谱、氢谱、磷谱和质谱测试确定了其结构.同时,研究了HDP的阻燃性,并与间苯二酚双(二苯基磷酸酯)(RDP)进行了比较,研究发现当HDP和RDP分别与成炭剂酚醛树脂(NP)按20/10比例添加到丙烯腈-丁二烯-苯乙烯(ABS)树脂中,增强了复合材料凝聚相阻燃作用,极限氧指数(LOI)有所提高.通过热重及锥形量热分析两种复合材料以及各种组分的热降解过程,阻燃剂的添加对ABS树脂的热稳定性和残炭量明显提高,而且ABS/HDP/NP复合材料的抑烟性更好;同时采用扫描电镜(SEM)和X射线能量色散谱(EDS),发现ABS/HDP/NP复合材料燃烧后成炭空隙均匀,其残炭中磷分布比ABS/RDP/NP复合材料残炭中的磷分布更加均匀.研究表明,HDP与NP互配添加到ABS中,在凝聚相阻燃作用优于RDP. 相似文献
957.
[reaction: see text] Photolysis of 3-(2,2,2-triphenylethoxy)-3-chlorodiazirine gives 2,2,2-triphenylethoxychlorocarbene which fragments with 1,2-phenyl migration and loss of CO and Cl(-) to yield the 1,1,2-triphenylethyl cation and thence 1,1,2-triphenylethene by proton loss. However, ps and fs laser flash photolysis provides evidence that up to 25% of the alkene product stems from carbocation that arises directly from excited diazirine rather than from the carbene. 相似文献
958.
孙福伟 《数学的实践与认识》2002,32(3):370-373
本文提出了位移和速度同时反馈的数学模型 .并给出了位移和速度反馈的实现方法 ,该方法用传统的差动变压器实现了位移和速度的同时反馈 相似文献
959.
A hydrophilic polymer, poly(N-vinyl-2-pyrrolidone), was tethered on the surface of polypropylene microfiltration membrane (PPMM) by UV photo-assisted and γ-ray pre-irradiation induced graft polymerizations. Results revealed that the γ-ray pre-irradiation graft polymerization was more efficient in view of the grafting degree. The chemical changes of the membrane surface were confirmed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Pure water contact angle on poly(N-vinyl-2-pyrrolidone)-grafted PPMM decreased with the increase of grafting degree, which indicated an enhanced hydrophilicity for the modified membrane. Both bovine serum albumin adsorption and static platelets adhesion were measured to evaluate the bio-compatibility of the poly(N-vinyl-2-pyrrolidone)-modified PPMM. The statistical amounts of adsorbed bovine serum albumin and adhered platelets on unit membrane area decreased significantly, which to a certain degree demonstrated that the hemocompatibility of PPMM was improved. The N2 permeability and the mean pore diameters of different PPMMs increased at first, then decreased after certain grafting degree. The changes of water flux followed a similar tendency. These indicated that at low grafting degree pore degradation induced by γ-ray irradiation had a major impact on permeability, while this was overcompensated by the grafted polymer at high grafting degrees. 相似文献
960.