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961.
Tumor cells K562 were killed by the hematoporphyrin derivatives (HpD) activated by bi-frequency focal ultrasound in which a choice of irradiating parameter of ultrasound was tested by experiment. The effect of killing tumor cells was investigated by MTT method and compared with the contrast group. The results showed that the bi-frequency ultrasound exhibited an improved effect of killing tumor cells than single frequency ultrasound. It was 2-3 times higher than the single frequency ultrasound for the killing effect of tumor cells. After the irradiation of ultrasound, the cell-killing effect of hatching 16 h is better than that of hatching 4 h in the hatching tank. This might be due to delay of cell apoptosis. 相似文献
962.
** Email: gqxu{at}tju.edu.cn*** Email: Jiajg{at}mailst.xjtu.edu.cn The group property of a string system with time delay in boundaryand the Riesz basis property of eigenvectors of the system arediscussed in the present paper. It is proved that, when thefeedback with delay > 0, the system also associates a C0group, and its eigenvectors (generalized eigenvectors) forma Riesz basis in Hilbert space . This result shows that timedelay may destroy the stability of the system, but the groupand Riesz basis properties are kept. As a consequence, the exactcontrollability of the system with boundary control is given. 相似文献
963.
Gen Onodera 《Tetrahedron》2010,66(46):9021-9031
A cationic iridium complex [Ir(cod)2]SbF6 was found to be a new and efficient Lewis acid catalyst for Mukaiyama aldol and Mannich reactions. Aldehydes react smoothly with silyl enol ethers to give β-siloxy ketones in the presence of 0.5 mol % of [Ir(cod)2]SbF6. The reaction of N-alkyl arylaldimines with ketene silyl acetals in the presence of 5 mol % [Ir(cod)2]SbF6/P(OPh)3 gave β-amino esters. After Mannich reaction was complete, stirring of the reaction mixture for 24 h led to cyclization to give β-lactam. The reaction of N-aryl benzaldimine with silyl enol ether derived from acetophenone gave a tetrahydroquinoline derivative as a single diastereomer. 相似文献
964.
An approximation algorithm for multidimensional assignment problems minimizing the sum of squared errors 总被引:1,自引:0,他引:1
Given a complete k-partite graph G=(V1,V2,…,Vk;E) satisfying |V1|=|V2|=?=|Vk|=n and weights of all k-cliques of G, the k-dimensional assignment problem finds a partition of vertices of G into a set of (pairwise disjoint) n k-cliques that minimizes the sum total of weights of the chosen cliques. In this paper, we consider a case in which the weight of a clique is defined by the sum of given weights of edges induced by the clique. Additionally, we assume that vertices of G are embedded in the d-dimensional space Qd and a weight of an edge is defined by the square of the Euclidean distance between its two endpoints. We describe that these problem instances arise from a multidimensional Gaussian model of a data-association problem.We propose a second-order cone programming relaxation of the problem and a polynomial time randomized rounding procedure. We show that the expected objective value obtained by our algorithm is bounded by (5/2−3/k) times the optimal value. Our result improves the previously known bound (4−6/k) of the approximation ratio. 相似文献
965.
966.
Cu-doped sodium zincophosphate [NaZn1−x(Cu)xPO4; x=0.05, 0.10, 0.15, and 0.20] powders were prepared by a coprecipitation method for the use as a dark heat-reflective material. The weighted average of the reflectance was calculated according to the reflectivity data measured using a UV-visible and near-infrared spectrophotometer. The measurement wavelength region was 380-2500 nm. The visible and near-infrared reflective properties of NaZn1−x(Cu)xPO4 doped with different amounts of Cu at varied calcination temperatures were investigated. NaZn(Cu)PO4 was found to be the main phase that crystallized in a monoclinic system of NaZn0.9(Cu)0.1PO4 at 800 °C. The sample of NaZn0.9(Cu)0.1PO4 was black in the visible region because of its high absorption, and its weighted average reflectance reached 51% in the near-infrared region. As a result, NaZn1−x(Cu)xPO4 has potential applications as a dark heat-reflective material. 相似文献
967.
本实验采用PECVD方法在不同透明导电薄膜上沉积了p型掺杂(p-Si:H)膜.用拉曼(Raman)光谱测试了p-Si:H膜的晶化率,并用扫描电子显微镜(SEM)观察了其形貌.结果表明:在SnO2上沉积的p-Si:H膜的晶化率较其它两种衬底高,相应的SEM形貌显示颗粒尺寸也较大.通过I-V测试仪测试了ZnO:Al/p-Si:H、SnO2/p-Si:H和SnO2/ZnO:Al/p-Si:H的接触特性,结果显示ZnO:Al/p-Si:H的接触特性并不比SnO2/p-Si:H差. 相似文献
968.
We have developed a novel approach to obtain high metal sorption capacity utilizing a membrane containing chitosan and an immobilized reactive dye (i.e. Reactive Yellow-2). The composite membrane was characterized by SEM, FT-IR, swelling test, and elemental analysis. The membrane has uniform small pores distribution and the pore dimensions are between 5 and 10 μm, and the HEMA:chitosan ratio was 50:1. The reactive dye immobilized composite membrane was used in the removal of heavy metal ions [i.e., Pb(II), Hg(II) and Cd(II)] from aqueous medium containing different amounts of these ions (5-600 mg l−1) and at different pH values (2.0-7.0). The maximum adsorption capacities of heavy metal ions onto the composite membrane under non-competitive conditions were 64.3 mmol m−2 for Pb(II), 52.7 mmol m−2 for Hg(II), 39.6 mmol m−2 for Cd(II) and the affinity order was Pb(II) > Hg(II)>Cd(II). 相似文献
969.
We have successfully synthesized two kinds of novel well-defined chain-end-functionalized polystyrenes with one, two, three, and four perfluorooctyl (C8F17) groups and structurally analogous block copolymers, poly[styrene-b-4-(3-perfluoroocyl)propoxystyrene], by means of living anionic polymerization, followed by the Williamson reaction with C8F17(CH2)3Br. The surface properties and compositions of the films prepared from both C8F17-functionalized polymers have been characterized by contact angles using water and dodecane droplets and angle-dependent XPS measurement. It was observed that C8F17 groups were segregated and preferentially enriched at their topmost surfaces and the extent of the enrichment increased with the number of C8F17 group. The dependence of extent of C8F17 group enrichment on fluorine content however appears to be different between chain-end-functionalized polymer and block copolymer. 相似文献
970.
Shohei Inoue Takuzo Aida Hiroshi Sugimoto Chikara Kawamura Masakatsu Kuroki 《Macromolecular Symposia》1994,88(1):117-122
An organoaluminum compound with bulky phenoxide groups as a Lewis acid can accelerate much the living polymerization of alkylene oxide initiated with aluminum porphyrin by the coordinative activation of the monomer. This concept can be extented to the polymerization initiated with aluminum Schiff base and tetraazaannulene complexes. 相似文献