Browsing by Author "Lopez, R"

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    Simazine dynamics in a vineyard soil at Casablanca valley, Chile
    (WILEY, 2005) Alister, C; Lopez, R; Kogan, M
    Field dissipation, soil movement and laboratory leaching studies were performed to elucidate the effect of two rainfall amounts in the behaviour and environmental fate of simazine under climatic conditions at Casablanca Valley, Chile. Dissipation and soil movement were studied in a field vineyard with a sandy loam soil (Inceptisol; 74.08% sand; 14.87% silt and 11.04% clay). Simazine was applied to bare soil at 2.0 kg AI ha(-1), and its concentration was measured using immunoassay (ELISA) at 0, 10, 20, 40 and 90 days after application under two rainfall amounts, natural field conditions (39 mm) and modified conditions (39 + 180 mm). Simazine leaching was studied using soil core PVC lysimeters (0.9 m height; 0.22m diameter). Field dissipation data were adjusted with a bi-exponential model. Half-life (DT50) values varied between 31.3 (+/- 2.5) and 19.0 (+/- 4.2) days under natural and modified conditions, respectively. Simazine K-d varied from 0.42 to 2.15 (K-oc 32.6-216.2) in the soil profile. Simazine was detected at a 90-cm soil depth in concentrations of 0.0085 (+/- 0.0043) mg kg(-1) and 0.0321 (+/- 0.001) mg kg(-1) under field and modified conditions, respectively. The maximum simazine leachate concentrations were 0.013 (+/- 0.00084) mg litre(-1) (0.012% of total applied simazine) and 0.0084 (+/- 0.00082) mg litre(-1) (0.11% of total applied simazine) for field and modified conditions respectively. These data indicate that water quantity has a significant effect on the DT50 and the amount of simazine that moved through the soil profile, but not on the soil depth reached by this herbicide. (c) 2005 Society of Chemical Industry.
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    Synthesis, crystal structure, molecular orbital calculations and electronic properties of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp)
    (ROYAL SOC CHEMISTRY, 1998) Lopez, R; Boys, D; Loeb, B; Zuloaga, F
    The synthesis, characterization and crystal structure of 2,3-di(2-pyridyl)naphtho[2,3-f]quinoxaline-7,12-quinone (Aqdpp) are reported. Molecular orbital calculations have been carried out in order to characterize its reactivity and coordination properties. surface maps for the electronegativity, hardness and Fukui functions have been generated to identify local reactivity sites and the crystal structure has been compared with the optimized geometry with good correlation among them. The acceptor properties of the Aqdpp ligand are shown by the orbital map for the LUMO level contributed mainly by the quinonic region of the ligand.