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991.
Duquesne E Degée P Habimana J Dubois P 《Chemical communications (Cambridge, England)》2004,(6):640-641
A new supported catalytic system, i.e. nickel bromide catalyst ligated by triphenylphosphine (TPP) ligands immobilized onto crosslinked polystyrene resins (PS-TPP) is reported. Per se, this catalyst does not allow any control over the polymerization of methyl methacrylate (MMA) initiated by ethyl 2-bromoisobutyrate but, in the presence of a given amount of purposely added free TPP, it promotes controlled ATRP of MMA. Indeed colorless PMMA chains of low polydispersity indices are readily recovered, the molecular weight of which linearly increases with monomer conversion and agrees with the expected values. Recycling of the supported catalyst is evidenced and does not prevent the polymerization from being controlled. 相似文献
992.
A coherent anti-Stokes Raman scattering microscope based on a Ti:sapphire femtosecond oscillator and a photonic crystal fiber is demonstrated. The nonlinear response of the fiber is used to generate the additional wavelength needed in the Raman process. The applicability of the setup is demonstrated by imaging of micrometer-sized polystyrene beads. 相似文献
993.
The intracavity laser absorption spectra (ICLAS) of dideuteroacetylene, C2D2, and acetylene, C2H2, have been recorded between 1.03 and 0.99 μm with a vertical external cavity surface emitting laser (VECSEL) leading to the observation of seven and six bands, for C2D2 and C2H2 respectively, most of them newly reported. The strong ν1+3ν3 band of C2D2 at is found accompanied by the two Π-Π hot bands with v4=1 and v5=1 lower state and by the ν2+3ν3+2ν4 band near . This last band results from an intensity transfer from the ν1+3ν3 band induced by the 1/244 anharmonic interaction. The ν1+3ν3 band of , present in natural abundance in the sample, could also be detected at in full agreement with local mode model predictions. The different bands of both C2H2 and C2D2 were found mostly unperturbed and the spectroscopic parameters retrieved from the rovibrational analyses agree satisfactorily with the predictions of the respective effective Hamiltonian models. 相似文献
994.
Anderson GS Tsujino I Miyagi K Sampson R Sieber F 《Journal of photochemistry and photobiology. B, Biology》2003,69(2):87-95
Paediatric solid tumours exhibit steep dose-response curves to alkylating agents and are therefore considered candidates for high-dose chemotherapy and autologous stem cell support. There is growing evidence that autologous stem cell grafts from patients with solid tumours are frequently contaminated with live tumour cells. The objective of this study was to perform, in a preclinical purging model, an initial assessment of the safety and efficacy of a two-step purging procedure that combined Merocyanine 540-mediated photodynamic therapy (MC540-PDT) with a brief exposure to the alkyl-lysophospholipid, Edelfosine. Human and murine bone marrow cells and Neuro-2a murine neuroblastoma, SK-N-SH human neuroblastoma, SK-ES-1 and U-2 OS human osteosarcoma, G-401 and SK-NEP-1 human Wilms' tumour, and A-204 human rhabdomyosarcoma cells were exposed to a fixed dose of MC540-PDT followed by a brief incubation with graded concentrations of Edelfosine. Survival was subsequently assessed by in vitro clonal assay or, in the case of CD34-positive haematopoietic stem cells, by an immunohistochemical method. Combination purging with MC540-PDT and Edelfosine depleted all tumour cells by >4 log while preserving at least 15% of murine granulocyte/macrophage progenitors (CFU-GM), 34% of human CFU-GM, and 31% of human CD34-positive cells. The data suggest that combination purging with MC540-PDT and Edelfosine may be useful for the ex vivo purging of autologous stem cell grafts from patients with paediatric solid tumours. 相似文献
995.
Sim TB Kang SH Lee KS Lee WK Yun H Dong Y Ha HJ 《The Journal of organic chemistry》2003,68(1):104-108
5-Funtionalized enantiomerically pure oxazolidin-2-ones were prepared in one pot from commercially available chiral aziridines bearing an electron-withdrawing group at C-2 with retention of the configuration in high yields by regioselective aziridine ring-opening followed by intramolecular cyclization. 相似文献
996.
A chemometric resolution method is described for the identification of nitrogen compounds in crude oil. Prefractionation of crude oil into discrete chemical classes was performed by adsorption column chromatography using small quantities of neutral aluminum oxide and silicic acid. Subsequent high-resolution separation of individual components was achieved by using capillary column gas chromatography, and compound types were detected by mass spectrometer. In conjunction with a combined chemometric method, each principal chemical class was further resolved and separated, which made it possible to identify some nitrogen compounds in the investigated oils. To a certain extent, this method could relieve classical analysis of difficulty in identifying those species with poorly low contents or partially chromatographic overlaps, particularly in the cases where authentic standards were not available for addition into the unknown analytical systems to reveal what indeed existed in them. 相似文献
997.
Stereoselectivity of nitrile oxide cycloadditions to chiral allylic fluorides: experiment and theory
Prakesch M Grée D Grée R Carter J Washington I Houk KN 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(22):5664-5672
The cycloadditions of nitrile oxides with new and previously studied allylic fluorides were examined. The 1,3-dipolar cycloaddition reactions were also investigated theoretically with density functional theory (B3LYP) based transition-state modelling. The predictions provided reasonable agreement with experiment, indicating that both steric and electronic effects have important influences on the stereoselectivities of these reactions. 相似文献
998.
The crystal structure of a streptomycin binding RNA aptamer displays a novel bipartite fold able to clamp the antibiotic. In view of the recent findings that metabolites directly control mRNA translation, we might expect that similar structures exist in natural RNAs. 相似文献
999.
Chen YL Sinha C Chen IC Liu KL Chi Y Yu JK Chou PT Lu TH 《Chemical communications (Cambridge, England)》2003,(24):3046-3047
Octahedral Os(II) complexes 1-5 with formula [Os(CO)3X(dbm)] are prepared through utilization of both solid-state pyrolysis and ligand exchange reactions. These complexes exhibit prominent 3pi-pi* phosphorescence with unusually long lifetimes (29-64 micros) and high quantum yields (0.08-0.13). 相似文献
1000.
Shavaleev NM Moorcraft LP Pope SJ Bell ZR Faulkner S Ward MD 《Chemical communications (Cambridge, England)》2003,(10):1134-1135
In a series of heterodinuclear complexes in which a Pt(PPh3)2(catecholate) chromophore is covalently linked to a lanthanide tris(diketonate) unit, sensitised near-IR emission from Yb(III), Nd(III) and Er(III) occurs on excitation of the Pt(II) chromophore at 520 nm. 相似文献