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61.
采用SCF-X_α-MS方法, 对于C(2×2)S/Fe(001)吸附体系, 选择Fe_5S和Fe_9S两种原子簇模型, 研究了该吸附体系的电子结构、吸附成键特征及其相互作用图象。结果表明, S吸附于Fe(001)单晶表面具有较强的定域性质, S原子与底物Fe原子之间的吸附相互作用主要表现为S(3p)-Fe(4s,3d)之间的轨道相互作用。通过对表面吸附键长的优化, 其结果与X.S.Zhang等的ARPEFS的实验结果一致。 相似文献
62.
Xue Zhi-Len Tan Ming-Guang Zhang Jia-Din Bao Jin-Rong 《Journal of Radioanalytical and Nuclear Chemistry》1982,72(1-2):101-108
The determination of calcium in yttrium oxide through the40Ca(α, p)43Sc reaction was studied, using a post-irradiation radiochemical separation procedure. The half-life of43Sc was determined to be 3.87 hr. The chemical recovery was about 70%. The detection limit was about 10 ppb, for a 30 min irradiation
at an alpha-particle beam current of 1 μA (Eα=13.4 MeV) and γ−γ coincidence counting (background counts being<1, cpm), with counting starting at 4 hours after the end
of irradiation. Four samples of a batch of yttrium oxide (A.R.) were analyzed, and found to contain 13.9±1.0 ppm of calcium. 相似文献
63.
Song H Hecimovic S Goate A Hsu FF Bao S Vidavsky I Ramanadham S Turk J 《Journal of the American Society for Mass Spectrometry》2004,15(12):1780-1793
Dysregulation of proteolytic processing of the amyloid precursor protein (APP) contributes to the pathogenesis of Alzheimer's Disease, and the Group VIA phospholipase A(2) (iPLA(2)beta) is the dominant PLA(2) enzyme in the central nervous system and is subject to regulatory proteolytic processing. We have identified novel N-terminal variants of iPLA(2)beta and previously unrecognized proteolysis sites in APP constructs with a C-terminal 6-myc tag by automated identification of signature peptides in LC/MS/MS analyses of proteolytic digests. We have developed a Signature-Discovery (SD) program to characterize protein isoforms by identifying signature peptides that arise from proteolytic processing in vivo. This program analyzes MS/MS data from LC analyses of proteolytic digests of protein mixtures that can include incompletely resolved components in biological samples. This reduces requirements for purification and thereby minimizes artifactual modifications during sample processing. A new algorithm to generate the theoretical signature peptide set and to calculate similarity scores between predicted and observed mass spectra has been tested and optimized with model proteins. The program has been applied to the identification of variants of proteins of biological interest, including APP cleavage products and iPLA(2)beta, and such applications demonstrate the utility of this approach. 相似文献
64.
PU大分子单体水溶液性质 总被引:2,自引:0,他引:2
双亲聚合物一般由亲水和亲油 2种链段构成 ,有嵌段型[1,2 ] 和接枝型[3 ] 2种 ,其中通过大分子单体法合成双亲接枝聚合物备受关注[4] 。如以亲水性大分子单体和亲油性小分子单体共聚 ,大分子单体构成共聚物主链上支链 ,具有较大活动性 ,亲水效能高。采用对氯甲基苯乙烯[5] 或甲基丙烯酰氯[6] 与聚氧化乙烯大分子的一端相反应 ,可得到亲水性大分子单体 ,但其分子量及结构变化有限。本文采用常规条件 ,合成了嵌段式水溶性聚氨酯大分子单体 ,其分子量较大 ,共聚接枝的支链较长。利用该大分子单体具有非离子高分子表面活性剂的性质 ,采用无皂乳… 相似文献
65.
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67.
Ang-ran Wang Yong-zhong Bao Zhi-xue Weng Zhi-ming Huang 《高分子科学》2007,(6):573-579
An exfoliated layered double hydroxides/poly(methyl methacrylate)(LDHs/PMMA)nanocomposite was prepared by in situ solution polymerization of methyl methacrylate(MMA)in the presence of 4-vinylbenzenesulfonate intercalated LDHs(MgAl-VBS LDHs).MgAl-VBS LDHs was prepared by the ion exchange method,and the structure and composition of the MgA1-VBS LDHs were determined by X-ray diffraction(XRD),infrared spectroscopy and elemental analysis.XRD and transmission electron microscopy(TEM)were employed to examine the structure of LDHs/PMMA nanocomposite.It was indicated that the LDHs layers were well exfoliated and dispersed in the PMMA matrix.The grafting of PMMA onto LDHs was confirmed by the extraction result and the weight fraction of grafted PMMA increased as the weight fraction of LDHs in the nanocomposites increased. 相似文献
68.
[structure: see text] The first syntheses of the adducts formed in the reactions of o-quinone metabolites of carcinogenic polycyclic aromatic hydrocarbons (BPQ and BAQ) at 2'-deoxyadenosine and 2'-deoxyguanosine sites in DNA are reported. These syntheses entail Pd-catalyzed coupling of protected amine derivatives of catechols with suitably protected halopurine analogues of 2'-deoxyribonucleosides. 相似文献
69.
本文发现6~40号元素对能量为20keV的X_射线的质量吸收系数和质量相干散射系数之间呈二次幂函数关系,并据此提出了X_射线荧光定量分析校正基体效应的新方法——RhKa相干散射平方法.用国家标准物质GBW对该原理进行了验证.本法用于硅酸盐地质样品中微量元素的测定取得令人满意的结果. 相似文献
70.
镧系与二甘醇-二-(邻羟基苯基)醚配合物的合成与表征 总被引:4,自引:0,他引:4
本文合成14种镧系高氯酸盐及硝酸盐分别与二甘醇-二-(邻羟基苯基)醚(记为EO_2(HOP)_2,EO=ethylene oxide,HOP为邻羟基苯基)形成的新配合物,确证组成为Ln(ClO_4)_3·EO_2(HOP)_2·nH_2O(Ln:La-Eu,n=10,Ln:Gd,Dy-Tm,Y,n=7),La_3(NO_3)_9·(EO_2(HOP)_2)_2·3H_2O及La(ClO_4)_2·EO_2H(OP)_25H_2O。文中研究了配合物红外,紫外、~1HNMR谱及~(13)C纵向弛豫时间T_1等,并讨论了共存阴离子、溶剂及配体不同端基对成配的影响。 相似文献