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131.
A highly selective method is described for the determination of 239,240Pu and 238Pu in soils by extraction chromatography with Microthene-710/tri-n-octylamine. The method is especially suitable for volcanic soils containing high concentrations of natural alpha radionuclides (Th, Po, U, etc.). The detection limit by α-spectrometry is 2.2 mBq kg?1 for 50-g soil samples. The average chemical yield, obtained by adding 242Pu as the internal standard, is 69.5 ± 17.1%. An IAEA reference soil was analyzed, with a relative error of 6.7% for 239Pu. The concentration of 2239,240Pu in thirteen analyzed soils and sediments ranged from 26.6 to 429 mBq kg?1. 相似文献
132.
Sandra Ianelli Corrado Pelizzi Giancarlo Pelizzi Pieralberto Tarasconi 《Journal of chemical crystallography》1996,26(3):195-201
Manganese(II), nickel(II), and copper(II) complexes of 2,6-diacetylpyridine bis (acetylhydrazone) (H2dapac) have been synthesized and structurally characterized by X-ray diffraction methods. [Mn(H2dapac) (OH2)2](NO3)2 crystallizes in the monoclinic space groupP21/c witha=11.145(3),b=10.723(4),c=17.189(2) Å, =92.81(2)° andZ=4; [Ni(H2dapac)(OH2)2] (NO3)2·H2O crystallizes in the monoclinic space groupP21 witha=9.994(3),b=14.423(4),c=7.697(2)Å, =100.37(2)°, andZ=2; [Cu(H2dapac)(OH2)2](NO3)2·H2O crystallizes in the orthorhombic space groupPbcn witha=20.986(5),b=14.552(3),c=6.905(1)Å andZ=4. In each case the metal atom has a slightly distorted pentagonal bipyramidal environment, the equatorial positions being occupied by three nitrogen and two oxygen atoms from the hydrazone ligand and the apices by two water molecules. The crystalline cohesion in ensured by a three-dimensional network of hydrogen bonds involving the complex cations, the nitrate anions, and, where present, the uncoordinate water molecules. 相似文献
133.
134.
Corrado Lattanzio Denis Serre 《NoDEA : Nonlinear Differential Equations and Applications》1999,6(3):319-340
We consider the interaction between shock waves in a semilinear relaxation approximation to N×N systems of conservation laws. This interaction is described by proving the existence of a particular solution to the relaxing
system, with a certain asymptotic as
Received July 1998 相似文献
135.
Corrado Sarzanini Maria Concetta Bruzzoniti Edoardo Mentasti 《Journal of chromatography. A》1999,850(1-2):197-211
A comparative study was made of the chromatographic behaviour of five haloacetic acids (mono-, dibromoacetic and mono-, di-, trichloroacetic acids). The techniques investigated included reversed-phase ion interaction chromatography with UV detection, suppressed and non-suppressed anion-exchange chromatography. The systems are discussed studying the retention as a function of the mobile phase parameters and the stationary phases used (LiChrospher 100 RP-18, IonPac AS9, AS10 and AS11). A preconcentration step, performed on different substrates, namely LiChrolut-EN and activated vegetal carbon, has been optimized in order to reduce the method detection limits. Results obtained for drinking water samples are shown. 相似文献
136.
The ortho-metallated complexes [Pd2{κ2(C,C)-C6H4(PPh2CHC(O)C6H5R}2(μ-Cl)2] (R = Ph (1a), NO2 (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph3PCHC(O)C6H5R, (R = Ph, NO2, Br) and Pd(OAc)2 in MeOH, followed by an excess of NaCl. The dinuclear complexes (1a-1c) react with silver trifluoromethylsulfonate and bidentate ligands [L = bipy (2,2′-bipyridine), phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), dppp (bis(diphenylphosphino)propane)] giving the mononuclear stabilized orthopalladated complexes in endo position [Pd{κ2(C,C)-C6H4(PPh2CHC(O)R}L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO2, L = phen (2b), bipy (3b), dppe (4b), dppp (5b); R = Br, L = phen (2c), bipy (3c), dppe (4c), dppp (5c); OTf = trifluoromethylsulfonate anion]. Orthometalation and ylidic C-coordination are demonstrated by an X-ray diffraction study of 2c and 3c. In the structures, the palladium atom shows a slightly distorted square-planar coordination geometry. 相似文献
137.
138.
139.
140.
Anthony Fucaloro Robert Pinnell Andrew Zanella Karen Conrad Yan Pu 《Journal of solution chemistry》2006,35(9):1245-1254
Both the partial molar volumes (V°
2m
refractions (R°
2m
) of the solutes at infinite dilution have been determined at 20 °C for a series of six octahedral N6-coordinated cobalt(III) species featuring five coordinated ammonia ligands along with a sixth N-coordinated organonitrile of increasing ligand size (from acetonitrile to sebaconitrile). The experimental values for V°
2m
are consistent with the relative sizes of the ligands but show larger values than those generated by computer modeling as the size of the cation increases, presumably due to the void space of the cation which increases with the size of the nitrile ligand. 相似文献