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71.
采用水热法制备了新型H6P2W9Mo9O62.24H2O催化剂,并用UV-Vis、FT-IR和TG-DTA等测试技术对催化剂进行了表征。以微波促进30%过氧化氢氧化环己酮制备己二酸合成反应为探针,考察了催化剂的催化性能。通过正交实验探讨了几种因素对反应的影响,确定了优化工艺条件为:n(环己酮)∶n(过氧化氢)∶n(草酸)∶n(催化剂)=100∶400∶1.25∶0.25,反应温度100℃,微波辐射功率400 W,反应时间3.5 h,己二酸产品的收率达87.33%,纯度可达99.7%。反应结束后,将反应后含催化剂的溶液浓缩至一定浓度,催化产率降低,重复使用5次收率降低为45.89%。 相似文献
72.
Heiko Kalpen Wolfgang Hnle Mehmet Somer Ulrich Schwarz Karl Peters Hans Georg von Schnering Roger Blachnik 《无机化学与普通化学杂志》1998,624(7):1137-1147
Bismuth(II) Chalcogenometallates(III) Bi2M4X8, Compounds with Bi24+ Dumbbells (M = Al, Ga and X = S, Se) The ternary bismuth(II) chalcogenometallates(III) Bi2M4X8 (with M = Al, Ga and X = S, Se) were synthesized from the binary chalcogenides M2X3 and Bi2X3 and elementary bismuth. All compounds are diamagnetic semiconductors with Eg (opt.) = 1.8–2.7 eV. The phases (except Bi2Al4Se8) are thermodynamically stable and decompose peritectically above 965–1020 K. Bi2Al4Se8 is metastable below 825 K and is obtained only by rapid quenching from T > 825 K. The isotypic compounds crystallize in a new tetragonal tP28 structure type (P4/nnc). The characteristic unit is the hitherto unknown clustercation Bi24+, with the mean bond length d(Bi–Bi) = 314.2 pm, the Raman frequency 102 cm–1 ≤ νs ≤ 108 cm–1, and the mean force constant of f = 0.68 N · cm–1. The Electron Localization Function, ELF, shows the covalent Bi–Bi bond, the lone electron pairs of the ψ-octahedrally coordinated Bi(II) cations, and the polar character of the Bi–X bonds. 相似文献
73.
The subsolidus phase relations of R2O3-CaO-CuO ternary systems (R=Nd, Sm, Gd, Tm) have been investigated by X-ray powder diffraction. All samples were synthesized at about 950° in air. There exists a ternary compound Ca14−xRxCu24O41 (x = 4 for R=Nd, Gd and x = 5 for R = Sm) and a ternary solid solution Ca2+xR2−xCu5O10 (R=Nd, Sm, Gd, Tm) with a wide composition range Δx of about 0.6. The compound Ca14−xRxCu24O41 possesses a layered orthorhombic structure and is isostructural to Sr14−xCaxCu24O41. The lattice parameters a and c of the compound are basically independent of the ionic radius of R, while the lattice parameter b and unit-cell volume V decrease substantially with the decrease of the ionic radii of R. The Ca2+xR2−xCu5O10 solid solution is isostructural to Ca2+xY2−xCu5O10, the structure of which is based on an orthorhombic “NaCuO2-type” subcell containing infinite one-dimensional chains of edge-shared square planar cuprate groups crosslinked by the layered cations Ca and R that locate in the inter-chain tunnels. 相似文献
74.
Kyoko TakahashiKenichiro Hashimoto Ayako FujiyamaJunko Yamada Noriko KobayashiMasuo Morisaki Sayaka NakanoNoriyuki Hara Yoshinori Fujimoto 《Tetrahedron letters》2003,44(2):341-344
Feeding of the chemically prepared [24-13C, 24-2H]desmosterol to cell-free systems derived from rat liver and silkworm gut and to cultured cells of Oryza sativa followed by deuterium-decoupled 1H, 13C shift correlation NMR analysis of the biosynthesized cholesterol revealed the stereospecific incorporation of hydrogen atoms from the re-face of the C-24 position of desmosterol. 相似文献
75.
通过基因重组技术将白介素24(IL-24)基因片段分别克隆成pc DNA3.0-OSP-1-IL-24和pc DNA3.0-IL-24载体,利用逆转录PCR(RT-PCR)测定2种载体的表达.将2种化疗药物紫杉醇(PTX)与顺铂(DDP)分别作用于正常SKOV3细胞及pc DNA3.0,pc DNA3.0-IL-24,pc DNA3.0-OSP-1和pc DNA3.0-OSP-1-IL-24稳定转染SKOV3细胞(卵巢癌细胞株),通过噻唑蓝(MTT)法检测化疗药物联合IL-24基因对细胞的杀伤效果及细胞的增殖能力,应用实时荧光定量PCR技术检测人β-微管蛋白3(TUBB3)与核苷酸切除修复交叉互补基因位1(ERCC1)基因在各组细胞中的表达.RT-PCR检测结果显示,通过基因重组技术克隆了pc DNA3.0-IL-24与pc DNA3.0-OSP-1-IL-24载体,IL-24基因能提高SKOV3细胞对化疗药物顺铂和紫杉醇的敏感性.其联合化疗药物对肿瘤药物的IC50值分别下降了10倍和6倍,TUBB3和ERCC1基因在IL-24基因转染的SKOV3细胞内的表达水平与在正常SKOV3细胞内相比,分别下降4倍和10倍多.上述结果表明,IL-24联合化疗药物可明显下调TUBB3与ERCC1基因的表达,该实验为临床治疗卵巢癌提供了重要的理论依据. 相似文献
76.
The electronic (energy gap and work function) as well as electrical properties (dipole moment, polarizability, and first hyperpolarizabilities) of the first-row transition metals decorated C24N24 cavernous nitride fullerene were explored using DFT calculations. The transition metals are decorated at N4 cavity of C24N24 fullerene. According to our spin polarized computations, the most stable spin state monotonically increases to sextet for Mn@C24N24 and thereafter dropped off gradually to singlet state for Zn@C24N24 system. The findings demonstrate that transition metals can remarkably decrease the HOMO-LUMO energy gap and work function values up to 63% and 21% of bare C24N24, respectively. As can be seen, when the Sc and Ti metals are located above the N4 cavity of fullerene, systems of enhanced static hyperpolarizabilities (β0) are delivered. These findings might provide an effective strategy to design high performance eletcro-optical materials based on carbon- nitride fullerene. 相似文献
77.
使用硫杂冠醚、穴醚[2.2.2]作气相色谱固定相制备毛细管柱,考察两种固定相的使用比例、极性、热稳定性,并对甲苯-苯、乙苯-甲苯、甲基苯酚(o/p)、二氯苯(o/p,m)、硝基氯化苯(m,o)、苯-环己烷、庚醇-辛醇、苯胺-N,N二甲基苯胺等混合样品进行色谱分离.实验结果表明:两种固定相在OV-1701中的比例均为15%时有较好的分离效果,都属于中等极性的固定相.硫杂冠醚、穴醚[2.2.2]的平均极性分别为815、832,其中硫杂冠醚固定相的热稳定性较好,有较高的使用温度(185℃),而穴醚[2.2.2]的最高使用温度为120℃,因此穴醚[2.2.2]的使用温度受到一定的限制.从它们较好的分离性能看,固定相硫杂冠醚、穴醚[2.2.2]均具有较好的应用前景. 相似文献
78.
A conductance study concerning the association of Na+, K+, Rb+, and Cs+ with 1,13-dibenzo-24-crown-8 in acetonitrile has been carried out at 35, 30, 25, 20, and 15°C. The observed molar conductivities were found to decrease significantly for mole ratios less than unity. A model involving 11 stoichiometry has been used to analyze the conductivity data. The stability constant, K, and the molar conductivity C for each 11 complex were determined from the conductivity data by using a nonlinear least squares curve fitting procedure. The binding sequence, based on the value of log K at 25°C, is found to be Rb+>Cs+>K+>Na+. Values of Ho and So are reported and their significance is discussed. 相似文献
79.
80.
简要阐述了分子器件和分子机器的相关概念,按照调控方式分类综述了基于24冠8的准轮烷、轮烷和索烃大环化合物构筑的分子器件和分子机器等在超分子领域的研究进展并对研究前景作了展望. 相似文献