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981.
W. Liu H.L. Xu G. Méjean Y. Kamali J.-F. Daigle A. Azarm P.T. Simard P. Mathieu G. Roy S.L. Chin 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
Remote filament-induced breakdown spectroscopy (R-FIBS) is a novel technique that could be applied at long distance up to a few kilometers. Our work demonstrates that by creating short and strong filaments in the atmosphere with a telescopic beam delivering system, continuum background in R-FIBS spectrum will be significantly reduced. This allows for a non-gated R-FIBS configuration for identifying solid targets. As an example, we used an aluminum plate located 50 m away from our detection system. The obtained fingerprint spectrum is so strong that the detection limit could reach 1.9 km in distance and ppm level in terms of minor element concentration. 相似文献
982.
Ye N Park G Przyborowska AM Sloan PE Clifford T Bauer CB Broker GA Rogers RD Ma R Torti SV Brechbiel MW Planalp RP 《Dalton transactions (Cambridge, England : 2003)》2004,(9):1304-1311
Three tripodal hexamine chelators based on cis,cis-1,3,5-triaminocyclohexane (tach) have been synthesized and their aqueous coordination chemistry with Ni(II), Cu(II) and Zn(II) is reported. The chelators have a 2-aminoethyl pendant arm attached to each nitrogen of tach, specifically 'tachen'(N,N',N'-tris(2-aminoethyl)cyclohexane-cis,cis-1,3,5-triamine), and two with S,S,S-chiral pendant arms, 'tachpn'(N,N',N'-tris(2-aminopropyl)cyclohexane-cis,cis-1,3,5-triamine) and 'tachbn'(N,N',N'-tris(2-amino-3-phenylpropyl)cyclohexane-cis,cis-1,3,5-triamine. These chelators complex Ni(II), Cu(II) and Zn(II) in aqueous or aqueous/methanolic medium. The crystalline products [M(II)L](X)2 are isolated, where M = Ni(II), Cu(II) or Zn(II), L = tachen, tachpn or tachbn, and X = ClO4-. Crystallographic study of selected tachpn and tachbn complexes shows the chelate arms are constrained in a Lambda(deltadeltadelta) configuration about M(II), which is attributed to their chirality. Solution UV-vis spectroscopy of the Ni(II) and Cu(II) complexes indicates six-coordination and little effect of the pendant arm substitution on ligand-field strength. The single exception is [Cu(tachbn)]2+, whose spectrum is consistent with five-coordination in solution. The cytotoxicities of tachen, tachpn and tachbn toward cultured cancer cells is in the order tachen < tachpn < tachbn < tachpyr, where tachpyr is the aminopyridyl chelator N,N',N'-tris(2-pyridylmethyl)cyclohexane-cis,cis-1,3,5-triamine. The cytotoxicity difference is attributed to an order of increasing lipophilicity, tachen < tachpn < tachbn. 相似文献
983.
We report herein the development of a palladium-catalyzed, multicomponent synthesis of indolizines. The reaction proceeds via the carbonylative formation of a high energy, mesoionic pyridine-based 1,3-dipole, which can undergo spontaneous cycloaddition with alkynes. Overall, this provides a route to prepare indolizines in a modular fashion from combinations of commercially available or easily generated reagents: 2-bromopyridines, imines and alkynes.A palladium catalyzed, multicomponent synthesis of indolizines is described via the carbon monoxide driven generation of reactive, pyridine-based 1,3-dipoles. 相似文献
984.
The synthesis of homogeneous hepta-antennated C-6 branched sialosyl cyclomaltoheptose derivatives (persialylated beta-cyclodextrins) has been performed in good to excellent yields, and the compounds have been fully characterized. The thioacetate N-acetylneuraminic acid derivative 6 was selectively de-S-acetylated and coupled by nucleophilic displacement in a one-pot reaction to the heptakis(chloroacetamido) beta-CDs 2 and 5, yielding multivalent sialosides 8 and 9, respectively. The thiourea-linked sialyl-CD 10 was obtained by reaction of the 4-isothiocyanatophenyl N-acetylneuraminic acid derivative 7 with the per-tert-butoxycarbonylamino beta-CD derivative 2 after suitable deprotection of the amino function. 相似文献
985.
Tenn WJ Young KJ Bhalla G Oxgaard J Goddard WA Periana RA 《Journal of the American Chemical Society》2005,127(41):14172-14173
A thermally and air stable O-donor, iridium-methoxo complex is reported that undergoes stoichiometric, intermolecular C-H activation of benzene with co-generation of methanol and the iridium-phenyl complex. 相似文献
986.
Sujata Roy 《Tetrahedron letters》2005,46(8):1325-1328
The reaction of 2-iodo- and 2-bromoindoles with silver nitrite in aqueous acetone affords the corresponding 2-nitroindoles in modest to good yields. 相似文献
987.
It was previously reported that methyl oleanonate (5) and lanost-8-en-3-one (10) give predominantly [3,2-c]isoxazoles. On the contrary, we have confirmed that both compounds 5 and 10 do not give [3,2-c]isoxazoles but rather afford regioselectively [2,3-d]isoxazoles in good yields. Consequently, a new lanostane triterpenoid with a cyano-enone functionality in ring A was synthesized in two steps from the corresponding [2,3-d]isoxazole, which is interesting from the perspective of biological activity because lanosterol is the biogenetic precursor of steroids. 相似文献
988.
Use of oxide minerals to abate fluoride from water 总被引:14,自引:0,他引:14
Mohapatra D Mishra D Mishra SP Chaudhury GR Das RP 《Journal of colloid and interface science》2004,275(2):355-359
The removal of fluoride from aqueous solutions has been investigated using various oxide ores such as refractory grade bauxite, feed bauxite, manganese ore, and hydrated oxides of manganese ores (WAD). The refractory grade bauxite showed promising results. The studies were carried out as functions of contact time, pH, concentration of adsorbents, concentration of adsorbate, and temperature. The adsorption was rapid during the initial 5 min but equilibrium was attained within 120 min. The adsorption followed first-order kinetics. The present system followed the Langmuir adsorption isotherm model. Various thermodynamic parameters such as free energy, enthalpy, entropy, and equilibrium constants were calculated. The isosteric heat calculations showed that the adsorption process followed a heterogeneous model. 相似文献
989.
Polyol Process Synthesis of Monodispersed FePt Nanoparticles 总被引:1,自引:0,他引:1
Liu C Wu X Klemmer T Shukla N Yang X Weller D Roy AG Tanase M Laughlin D 《The journal of physical chemistry. B》2004,108(20):6121-6123
Monodispersed FePt nanoparticles are synthesized by reduction of iron(II) acetylacetonate and platinum(II) acetylacetonate with 1,2-hexadecanediol as the reducing reagent in the polyol process. As-prepared FePt nanoparticles are chemically disordered with fcc phase. Transmission electron microscopy (TEM) images show a self-assembled particle array with an average particle size of 3 nm and a standard deviation about 10%. The transformation from chemically disordered fcc to chemically ordered L10 phase is achieved by annealing at 650 degrees C for 30 min in Ar atmosphere where the oxygen level is less than 1 ppm. Magnetic hysteresis measurements show a coercivity of 9.0 kOe at 293K, and 16.7 kOe at 5 K for the annealed FePt nanoparticles. 相似文献
990.
Summary A group of mixed-tris chelates of osmium(III) and osmium(IV) of type [OsAQ2]0/1 + [HA = glycine (glyH), picolinic acid (PicH) and quinaldic acid (qndH); HQ = 8-quinolinol] were prepared and characterized by physicochemical, magnetic and spectroscopic methods. The complexes exhibit several spin-allowed and spin-forbidden absorption bands and shoulders in the 200–700 nm region. The new chelates are electroactive and display nearly reversible OsIV-OsIII and OsIII-OsII couples in the ca. –1.1 to +0.3 V range versus s.c.e. The stability of metal oxidation states is discussed in terms of the electrochemical results. 相似文献