Principe local-global pour les zéro-cycles sur certaines fibrations au-dessus d’une courbe: I

Soit X une variété projective lisse sur un corps de nombres, fibrée au-dessus d’une courbe C, à fibres géométriquement intègres. On démontre que, en supposant la finitude de III(Jac(C)), si les fibres au-dessus d’un sous-ensemble hilbertien généralisé satisfont le principe de Hasse (resp. l’approximation faible), alors l’obstruction de Brauer–Manin provenant de la courbe en bas est la seule au principe de Hasse (resp. à l’approximation faible) pour les zéro-cycles de degré 1 sur X. Ceci est appliqué à l’exemple récent de Poonen.     

New Lower Bounds on the Multicolor Ramsey Numbers R r (C 2 m )

The multicolor Ramsey number R_r(H) is defined to be the smallest integer n=n(r) with the property that any r-coloring of the edges of the complete graph K_n must result in a monochromatic subgraph of K_n isomorphic to H. It is well known that 2^rm<R_r(C_2m+1)<2(r+2)!m and R_r(C_2m)≥(r−1)(m−1)+1. In this paper, we prove that R_r(C_2m)≥2(r−1)(m−1)+2. This research is supported by NSFC(60373096, 60573022) and SRFDP(20030141003)     

图的导出森林2-划分

对一个给定的简单图Ｇ，是否存在Ｖ（Ｇ）的一个２－划分（Ｖ１，Ｖ２）使得每个导出子图Ｇ［Ｖｉ］为森林？称该问题为导出森林２－划分问题．本文证明了对最大度为５的图该问题是ＮＰ－完全的，而对最大度≤４的图该问题多项式时间可解．     

钕铁硼三元系理想粉末X-射线衍射谱图的计算

本文设计一个程序,计算得到Nd-Fe-B四方晶系理想粉末X-射线衍射数据,并绘出谱图,在物相鉴定中可起标准卡片的作用。     

辐射加工(Co-60γ射线)吸收剂量测量体系研究

本研究建立的辐射加工(Co-60γ)射线)吸收剂量测量体系,包括Fricke剂量计,硫酸铈(Ce~(4 ))/硫酸铜(Cu~(2 ))剂量计,GF型辐射显色尼龙薄膜剂量计和GAC-01型定性标识剂量计。报告中叙述了各个剂量计的研制方法,适用的剂量测量范围及其各自达到的测量精度和总不确定度。     

棕色固氮菌变种UW45缺辅基钼铁蛋白的分离及性质研究(Ⅰ)

应用DEAE-11#纤维素柱层析,结合无氧制备电泳从棕色固氮菌变种uw45无细胞抽提液中分离得到了一种电泳纯蛋白质,回收率为18.4%。该蛋白与FeMoco重组可以催化乙炔还原成乙烯,比活可达5.85nM乙烯/分·毫克蛋白,比其无细胞抽提液活性提高22.7倍。该蛋白与FeMoco重组之后,电泳迁移率明显变慢,更接近棕色固氮菌钼铁蛋白,含铁量增加一倍,井含钼,分子量22万,可见光谱与棕色固氮菌钼铁蛋白的相同。因此,我们认为uw45缺辅基铜铁蛋白与FeMoco重组之后形成了类似棕色固氮菌钼铁蛋白的活性蛋白。     

HEH/EHP萃取剂中钍的反萃性能研究

研究了含钍HEH/EHP(2-乙基己基膦酸单-2-乙基己基脂)萃取剂中钍的反萃性能。采用HCl,HNO3和H2SO4三种矿物酸分别对钍进行了反萃试验研究,结果表明,当反萃酸浓度为[H+]=6 mol.L-1时,HCl和HNO3反钍率小于1%,而硫酸的反钍率接近69%,表明H2SO4是钍的有效反萃剂。以H2SO4作为反萃剂,研究了相比、反萃酸浓度、酸用量、萃取剂浓度及钍负载量对钍的反萃性能的影响。在此基础上,对钍的逆流反萃过程进行了研究,当起始酸浓度为7 mol.L-1时,分别采用1∶1和4∶1的相比进行3级逆流反萃,反萃率分别为92.10%和53.29%。     

Developing the liquid chromatography-mass spectrometry method for simultaneously quantifying five components in rat serums after oral administration of hawthorn aqueous extracts and its application to a pharmacokinetic study

Hawthorn, one of the widely-used traditional Chinese medicines, has been used to treat dyspepsia, hyperlipidemia, and cardiovascular disease in the clinic. Our previous study revealed that gallic acid, neochlorogenic acid, cryptochlorogenic acid, vitexin, and quercetin were active components of hawthorn. In this study, a simple, precise, and reliable liquid chromatography-mass spectrometry method was developed for the simultaneous quantification of five components in rat serums. The separation was achieved on the Hypersil GOLD C₁₈ column, and the mobile phases consisted of 0.1% acetic acid water and methanol at a flow rate of 0.3 mL/min. The mass spectrometry data acquisition was performed on Q-Extractive-Orbitrap mass spectrometry with an electrospray ionization source in negative ion mode. The proposed liquid chromatography-mass spectrometry method was validated in terms of linearity, intra- and inter-precision, accuracy, recoveries, matrix effects, and stability. Then this newly proposed liquid chromatography-mass spectrometry method was successfully applied to a pharmacokinetic study on rats after oral administration of hawthorn aqueous extracts. This study provided relevant information on the pharmacokinetics of active components of hawthorn and explained the underlying mechanism of their bioactivity.     

Structural,spectroscopic, and reactivity comparison of xanthene- and dibenzofuran-bridged cofacial bisporphyrins

A comparison of the structure, spectroscopy, and oxygen atom-transfer reactivity of cofacial bisporphyrins anchored by xanthene (DPX) and dibenzofuran (DPD) pillars is presented. The synthesis and characterization of dicopper(II) and dinickel(II) complexes of DPD completes a homologous series of homobimetallic zinc(II), copper(II), and nickel(II) complexes for both cofacial platforms. X-ray crystallographic analysis of the parent free-base porphyrins H(4)DPX (1) and H(4)DPD (5) confirms the face-to-face arrangement of the two porphyrin macrocycles with a large available range of vertical pocket sizes: 1 (C(80)H(92)Cl(2)N(8)O), triclinic, space group P1 macro, a = 13.5167(12) A, b = 21.7008(18) A, c = 23.808(2) A, alpha = 80.116(2) degrees, beta = 76.832(2) degrees, gamma = 80.4070(10) degrees, Z = 4; 5 (C(80)H(83)N(8)O(2)), monoclinic, space group C2/c, a = 22.666(2) A, b = 13.6749(14) A, c = 42.084(4) A, beta = 94.554(2) degrees, Z = 8. EPR spectroscopy of dicopper(II) derivatives Cu(2)DPX (3) and Cu(2)DPD (7) complements the crystallographic studies by probing intramolecular metal-metal arrangements in frozen solution. Exciton interactions between the porphyrin subunits in fluid solution are revealed by steady-state and time-resolved electronic absorption and emission spectroscopy. The resulting compilation of structural and spectroscopic data provides a benchmark for the use of these and related platforms for the activation of small-molecule substrates. A structure-function relation is developed for the photoinduced oxygen atom-transfer reactions of bisiron(III) mu-oxo derivatives of DPX and DPD. The efficiency of the photochemical process is markedly dependent (approximately 10(4)-fold) on the vertical flexibility of cofacial architecture provided by the spacer.