Exudation of alcohol and aldehyde sugars from roots of defoliated Lolium perenne L. grown under sterile conditions

Root exudates were collected over a 27 day period from defoliated and non-defoliated Lolium perenne L. plants grown under sterile conditions in microlysimeters. Eleven individual sugars, including both aldehyde and alcohol sugars, were identified and quantified with a gas chromatograph-mass spectrometer (GC-MS). There was no change in the number of sugars present between 7 and 27 days, but the exudation of alcohol sugars decreased rapidly at about day 12. Xylose and glucose were present in the largest amounts. Defoliation initially increased the total amount of sugars in the exudates, but continuous defoliation reduced total sugar exudation by 16% and induced changes in the exudation patterns of individual sugars. Defoliation enhanced exudation of erythritol, threitol, and xylitol, reduced exudation of glucose and arabitol, but had little effect on the amounts of other sugars exuded. The more complex 6 C, 5 OH aldehyde sugars, especially glucose, showed changes earlier and to a greater extent (17 days), than the 5 C, 4 OH (xylose and ribose) and 6 C 4 OH (fucose) aldehyde groups. These findings confirm the general finding that repeated defoliation reduces the quantity of total sugars exuded, but the pattern of release of individual sugars is complex and variable.

Time patterns in UK demand for alcohol and tobacco: an application of the EM algorithm

Capturing the pattern of structural change is a relevant task in applied demand analysis, as consumer preferences may vary significantly over time. Filtering and smoothing techniques have recently played an increasingly relevant role. A dynamic Almost Ideal Demand System with random walk parameters is estimated in order to detect modifications in consumer habits and preferences, as well as changes in the behavioural response to prices and income. Systemwise estimation, consistent with the underlying constraints from economic theory, is achieved through the EM algorithm. The proposed model is applied to UK aggregate consumption of alcohol and tobacco, using quarterly data from 1963 to 2003. Increased alcohol consumption is explained by a preference shift, addictive behaviour and a lower price elasticity. The dynamic and time-varying specification is consistent with the theoretical requirements imposed at each sample point. (c) 2005 Elsevier B.V. All rights reserved.

Molybdenum eta(3)-allyl dicarbonyl complexes as a new class of precursors for highly reactive epoxidation catalysts with tert-butyl hydroperoxide

New Mo(II) diimine derivatives of [Mo(q (3)allyl)X(CO)(2)(CH3CN)(2)] (allyl = C3H5 and C5H5O; X = Cl, Br) were prepared, and [MO(eta(3)-C3H5)Cl(CO)(2)(BIAN)] (BIAN = 1,4-(4-chloro)phenyl-2,3-naphthalene-diazabutadiene) (7) was structurally characterized by single-crystal X-ray diffraction. This complex adopted an equatorial-axial arrangement of the bidentate ligand (axial isomer), in contrast with the precursors, found as the equatorial isomer in the solid and fluxional in solution. The new complexes of the type [Mo(eta(3)-allyl)X(CO)(2)(N-N)l (N-N is a bidentate chelating dinitrogen ligand) were tested for the catalytic epoxidation of cyclooctene using tert-butyl hydroperoxide as oxidant. All catalytic systems were 100% selective toward epoxide formation. While their turnover frequencies paralleled those of related Mo(eta) carbonyl compounds or Mo(VI) compounds bearing similar N-donor ligands, they exhibited similar olefin conversions in consecutive catalytic runs. The acetonitrile precursors were generally more active than the diimine complexes, and the chloro derivatives more active than the bromo ones. Combined vibrational and NMR spectroscopy and computational studies (DFT) were used to investigate the nature of the molybdenum species formed in the catalytic system with [Mo(eta(3)-C3H5)Cl(CO)(2){1,4-(2,6-dimethyl)phenyl-2.3-dimethyldiazabuta diene}] (4) and to propose that the resulting species may be dimeric bearing oxide bridges.