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271.
In the pore of a porous coordination network, Diels-Alder reactants, a diene and a dienophile, are recognized by donor-acceptor and multiple H-bond interactions, respectively, and fixed at ideal positions for the reaction. Heating the crystals promoted the Diels-Alder reactions with enhanced reactivity and controlled regioselectivity as clearly monitored by in situ X-ray crystallography. 相似文献
272.
Yamaguchi S Kobayashi H Narita T Kanehira K Sonezaki S Kudo N Kubota Y Terasaka S Houkin K 《Ultrasonics sonochemistry》2011,18(5):1197-1204
Sonodynamic therapy is expected to be a novel therapeutic strategy for malignant gliomas. The titanium dioxide (TiO(2)) nanoparticle, a photosensitizer, can be activated by ultrasound. In this study, by using water-dispersed TiO(2) nanoparticles, an in vitro comparison was made between the photodynamic and sonodynamic damages on U251 human glioblastoma cell lines. Water-dispersed TiO(2) nanoparticles were constructed by the adsorption of chemically modified polyethylene glycole (PEG) on the TiO(2) surface (TiO(2)/PEG). To evaluate cytotoxicity, U251 monolayer cells were incubated in culture medium including 100 μg/ml of TiO(2)/PEG for 3h and subsequently irradiated by ultraviolet light (5.0 mW/cm(2)) or 1.0MHz ultrasound (1.0 W/cm(2)). Cell survival was estimated by MTT assay 24h after irradiation. In the presence of TiO(2)/PEG, the photodynamic cytotoxic effect was not observed after 20 min of an ultraviolet light exposure, while the sonodynamic cytotoxicity effect was almost proportional to the time of sonication. In addition, photodynamic cytotoxicity of TiO(2)/PEG was almost completely inhibited by radical scavenger, while suppression of the sonodynamic cytotoxic effect was not significant. Results of various fluorescent stains showed that ultrasound-treated cells lost their viability immediately after irradiation, and cell membranes were especially damaged in comparison with ultraviolet-treated cells. These findings showed a potential application of TiO(2)/PEG to sonodynamic therapy as a new treatment of malignant gliomas and suggested that the mechanism of TiO(2)/PEG mediated sonodynamic cytotoxicity differs from that of photodynamic cytotoxicity. 相似文献
273.
A method for the analysis of chlorinated and brominated polycyclic aromatic hydrocarbon (Cl-/Br-PAHs) congeners in environmental samples, such as a soil extract, by comprehensive two-dimensional gas chromatography coupled to a high resolution time-of-flight mass spectrometry (GC×GC-HRTOF-MS) is described. The GC×GC-HRTOF-MS method allowed highly selective group type analysis in the two-dimensional (2D) mass chromatograms with a very narrow mass window (e.g. 0.02Da), accurate mass measurements for the full mass range (m/z 35-600) in GC×GC mode, and the calculation of the elemental composition for the detected Cl-/Br-PAH congeners in the real-world sample. Thirty Cl-/Br-PAHs including higher chlorinated 10 PAHs (e.g. penta, hexa and hepta substitution) and ClBr-PAHs (without analytical standards) were identified with high probability in the soil extract. To our knowledge, highly chlorinated PAHs, such as C(14)H(3)Cl(7) and C(16)H(3)Cl(7), and ClBr-PAHs, such as C(14)H(7)Cl(2)Br and C(16)H(8)ClBr, were found in the environmental samples for the first time. Other organohalogen compounds; e.g. polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzofurans (PCDFs) were also detected. This technique provides exhaustive analysis and powerful identification for the unknown and unconfirmed Cl-/Br-PAH congeners in environmental samples. 相似文献
274.
Haraguchi K Horii C Yoshimura Y Ariga F Tadokoro A Tanaka H 《The Journal of organic chemistry》2011,76(21):8658-8669
We have developed a novel method for the synthesis of the β-anomer of 4'-thio-C-ribonucleosides from 3,5-O-(di-tert-butylsilylene)-4-thiofuranoid glycal. Palladium-catalyzed coupling of 1-tributylstannyl-4-thiofuranoid glycal with iodobenzene or a heteroaryl halide gave 1-C-phenyl- or 1-C-heteroaryl-glycals. Hydroboration of these glycals proceeded at the α-face, and subsequent alkaline hydrogen peroxide treatment of the resulting 2'-α-borane furnished the respective β-anomer of 4'-thio-C-ribonucleosides. These results demonstrate that this synthetic method has a wider scope in terms of heterocyclic base structure. During this study, unexpected Markovnikov-oriented hydroboration has been observed to lead to the respective 1'-α-boranes. These 1'-boranes were converted into either the ring-opened structure or the 2'-deoxy derivatives depending upon their stability. 相似文献
275.
S. Horii S. Okuhira M. Yamaki M. Haruta T. Maeda J. Shimoyama 《Physica C: Superconductivity and its Applications》2011,471(21-22):867-871
We report the tri-axial grain-orientation effects under a modulated rotation magnetic field for (Y1?xErx)2Ba4Cu7Oy [(Y, Er)247]. The magnetic easy axis at room temperature was drastically changed around x ~ 0.1; however, the Er-doping levels for the conversion of magnetic easy axes from the c-axis to the ab-direction and from the a- to b-axes were quite different. Tri-axial single-ion magnetic anisotropy of Er3+ was roughly 10 times greater than tri-axial magnetic anisotropy generated by both the superconducting CuO2 plane and the blocking Cu–O chain layer. An appropriate choice of rare-earth (RE) ions in RE-based cuprate superconductors enables the reduction of the required magnetic field for the production of bulks and thick films based on the magnetic orientation technique. 相似文献
276.
Bhardwaj V Trabelsi K Singh JB Choi SK Olsen SL Adachi I Adamczyk K Asner DM Aulchenko V Aushev T Aziz T Bakich AM Barberio E Belous K Bhuyan B Bischofberger M Bondar A Bračko M Brodzicka J Browder TE Chen A Chen P Cheon BG Cho K Choi Y Dalseno J Doležal Z Eidelman S Epifanov D Gaur V Gabyshev N Golob B Haba J Hayasaka K Hayashii H Horii Y Hoshi Y Hou WS Hsiung YB Hyun HJ Iijima T Inami K Ishikawa A Iwabuchi M Iwasaki Y Iwashita T Joshi NJ Julius T Kang JH Kawasaki T Kiesling C Kim HO Kim JB 《Physical review letters》2011,107(9):091803
We report a study of B→(J/ψγ)K and B→(ψ'γ)K decay modes using 772×10? B ?B events collected at the Υ(4S) resonance with the Belle detector at the KEKB energy-asymmetric e(+)e(-) collider. We observe X(3872)→J/ψγ and report the first evidence for χ(c2)→J/ψγ in B→(X_{c ?cγ)K decays, while in a search for X(3872)→ψ'γ no significant signal is found. We measure the branching fractions, B(B(±)→X(3872)K(±))B(X(3872)→J/ψγ)=(1.78(-0.44)(+0.48)±0.12)×10(-6), B(B(±)→χ(c2)K(±))=(1.11(-0.34)(+0.36)±0.09)×10(-5), B(B(±)→X(3872)K(±))B(X(3872)→ψ'γ)<3.45×10? (upper limit at 90% C.L.), and also provide upper limits for other searches. 相似文献
277.
We show the bursting process of dioleoylphosphatidylcholine (DOPC) liposomes in response to the addition of acetonitrile, a small toxic molecule widely used in the fields of chemistry and industry. The percentage of destroyed liposomes is reduced upon decreasing the acetonitrile fraction in the aqueous solution and vesicle bursting is not observed at volume ratios of 4:6 and below. This indicates that a high fraction of acetonitrile causes the bursting of liposomes, and it is proposed that this occurs through insertion of the molecules into outer leaflet of the lipid bilayer. The elapsed time between initial addition of acetonitrile and liposome bursting at each vesicle is also measured and demonstrated to be dependent on the volume fraction of acetonitrile and the vesicle size. 相似文献
278.
Itoh T Urita K Bekyarova E Arai M Yudasaka M Iijima S Ohba T Kaneko K Kanoh H 《Journal of colloid and interface science》2008,322(1):209-214
The nanoporosities and catalytic activities of Pd nanoparticles dispersed on single wall carbon nanohorns (Pd-SWCNHs) and oxidized single wall carbon nanohorns (Pd-ox-SWCNHs) were examined. A transmission electron microscopy (TEM) observation indicated that Pd nanoparticles of 2-3 nm size were highly dispersed on both the SWCNHs. X-ray photoelectron spectra and N2 adsorption isotherms at 77 K illustrated the differences in the deposition process mechanisms of the Pd-SWCNHs and Pd-ox-SWCNHs; the deposition process depended on the surface functional groups. The supercritical H2 adsorption isotherms at 77 K suggested the relationships between the interaction of Pd-SWCNHs and Pd-ox-SWCNHs with H2 and the catalytic activities for a water formation reaction in a gas phase at 273 or 298 K. The catalytic activity measurement and TEM observation of the catalysts after the reactions demonstrated that the Pd-SWCNHs and Pd-ox-SWCNHs are promising catalysts. 相似文献
279.
Masaki Abe Masashi Eto Koki Yamaguchi Masatoshi Yamasaki Junichi Misaka Yasuyuki Yoshitake Masami Otsuka Kazunobu Harano 《Tetrahedron》2012,68(18):3566-3576
Two clathrate hosts (3a and 3b) were synthesized via the Diels–Alder reaction of phencyclone (1a) and tetracyclone (1b) with acenaphthylene (2), and the clathrate formation properties of these hosts towards a variety of organic guests were investigated. In the presence of aprotic solvents (i.e., aromatic, ketonic and etheric solvents), host 3a formed inclusion complexes with a 2:1 stoichiometric host/guest ratio, whereas 3b primarily formed 1:1 complexes. The desolvation temperatures of the 3a·guest complexes were extremely high in comparison to the boiling points of the pure guest liquids and were also much higher than those of the corresponding 3b·guest complexes, which contain the conformationally flexible stilbene moiety. Structural analyses of the 3a·guest complexes (i.e., 3a·benzene, 3a·toluene, 3a·1,4-dioxane, 3a·acetone and 3a·pentan-3-one) show that the aromatic CH/π (edge-to-face) interactions between phenanthrene and the acenaphthene ring as well as the interaction of the ‘bidentate’ CH/O hydrogen bond between the phenanthrene-ring hydrogen and the bridged carbonyl oxygen play a key role in the construction of the characteristic host ‘column’ structures. The guest molecule of the 3a·benzene complex is held between the stacking columns by aromatic CH/π interactions of the acenaphthene rings of adjacent host molecules. The stable clathrate formation of 3a is discussed based on X-ray structural analyses of six clathrates and PM6 molecular orbital calculations for the clathration model of 3a·benzene. 相似文献
280.
2,5-Bis(methoxycarbonyl)-3,4-diphenylcyclopentadienone (1a) reacts with prop-2-yn-1-ols (2) to give 3-methylene-2,3,3a,6a-tetrahydrocyclopenta[b]furan-4-one derivatives in the presence of trialkylamines. 相似文献