Markownikoff and anti-Markownikoff hydroamination with palladium catalysts immobilized in thin films of silica supported ionic liquids

The concept of immobilising organometallic complexes in a thin film of supported ionic liquids was utilised to synthesise novel bi-functional catalysts combining soft Lewis acidic and strong Br?nsted acidic functions; the materials showed exceptional catalytic activity for the addition of aniline to styrene, providing the Markownikoff product under kinetically controlled conditions and mainly the anti-Markownikoff product in the thermodynamic regime.     

Formation of solvent cages around organometallic complexes in thin films of supported ionic liquid

The first experimental evidence for the formation of ordered three-dimensional structures in solutions of organometallic complexes in a thin film of supported ionic liquid was obtained. The ordering effect leads to drastically reduced mobility of ionic liquid and complex molecules.     

High order local linearization methods: An approach for constructing A-stable explicit schemes for stochastic differential equations with additive noise

An approach for the construction of A-stable high order explicit strong schemes for stochastic differential equations (SDEs) with additive noise is proposed. We prove that such schemes also have the dynamical property that we call Random A-stability (RA-stability), which ensures that, for linear equations with stationary solutions, the numerical scheme has a random attractor that converges to the exact one as the step size decreases. Basically, the proposed integrators are obtained by splitting, at each time step, the solution of the original equation into two parts: the solution of a linear ordinary differential equation plus the solution of an auxiliary SDE. The first one is solved by the Local Linearization scheme in such a way that A-stability is guaranteed, while the second one is approximated by any extant scheme, preferably an explicit one that yields high order of convergence with low computational cost. Numerical integrators constructed in this way are called High Order Local Linearization (HOLL) methods. Various efficient HOLL schemes are elaborated in detail, and their performance is illustrated through computer simulations. Furthermore, mean-square convergence of the introduced methods is studied.     

Determination of the pesticides fenthion and fenitrothion by flow injection with amperometric detection

The response of a glassy carbon amperometric detector in a flow system was studied. The values of the hydrodynamic variables were optimized. The detector functioned as a “thin-layer” cell. Methods are proposed for the determination of 1.6 × 10^?7?1.6 × 10^?5 Fenthion and 8 × 10^?6? 8× 10^?5 M Fenitrothion in a methanolic acetate-buffered carrier stream. The detection limits were 0.15 and 0.52 μM, respectively.     

Dendrimer effects upon the reaction between (acetonitrile)pentacyano-ferrate(II) and pentaamminepyrazine-ruthenium(II)

Kinetics of the forward and reverse processes of the title ligand substitution reaction have been studied in the presence of the SB4.5G dendrimer. Results are in agreement with expectation, according to a two-state model. These results are the consequence, for the forward process, of the negative charge of one of the reactants, (iron complex), and the positive charge of the other (ruthenium complex). This produces a spatial separation of the reactants in the presence of the negatively charged dendrimer. The reverse process becomes slower in the presence of the dendrimer because of the dielectric saturation in the close vicinity of the dendrimer. This hinders the charge separation implicit in the reverse process.     

Chemical composition and antifungal activity of essential oils from Senecio nutans,Senecio viridis,Tagetes terniflora and Aloysia gratissima against toxigenic Aspergillus and Fusarium species

Abstract

Essential oils from aerial parts of Senecio nutans, Senecio viridis, Tagetes terniflora and Aloysia gratissima were analysed by GC-MS and their antifungal activities were assayed on toxigenic Fusarium and Aspergillus species. Sabinene (27.6?±?0.1%), α-phellandrene (15.7?±?0.3%), o-cymene (9.6?±?0.2%) and β-pinene (6.1?±?0.2%) in S. nutans, 9,10-dehydrofukinone (92.7?±?0.2%) in S. viridis, β-thujone (36.1?±?0.1%), α-thujone (32.2?±?0.2%), 1,8-cineol (10.7?±?0.1%) and sabinene (6.2?±?0.2%) in A. gratissima, and cis-tagetone (33.6?±?0.2%), cis-β-ocimene (17.1?±?0.2%), trans-tagetone (17.0?±?0.1%), cis-ocimenone (8.0?±?0.2%) and trans-ocimenone (8.2?±?0.1%) in T. terniflora. The oils showed moderate antifungal activity (1.2?mg/mL?>?MIC >0.6?mg/mL) on the Fusarium species and a weak effect on Aspergillus species. The antifungal activity was associated on F. verticillioides to the high content of cis-tagetone, trans-tagetone, cis-β-ocimene, cis-ocimenone, trans-ocimenone and on F. graminearum due to the total content of oxygenated sesquiterpenes and 9,10- dehydrofukinone. The oil of S. viridis synergized the effect of fungicides and food preservatives on F. verticillioides.

     

Effect of alkali metal ions on the catalytic of Pd/SiO2?AlPO4 systems

The effect of different alkali metal hydroxides on the metallic dispersity and catalytic activity of SiO₂–AlPO₄ (8020, by mass) supported palladium catalysts has been studied. The reduction by hydrogen transfer of benzylideneacetone and styrene (using cyclohexene and n-octanol, respectively, as hydrogen donors) and the liquid phase reduction of cyclohexene at low pressure (5 bar) in a Parr type reactor have been used as test reactions to follow changes in the catalytic activity.

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(SiO₂–AlPO₄/8020 ). ( n-, , , (5 ) .

     

Optimization of a heart-cutting multidimensional gas chromatography-based method for the assessment of enantiomeric fractions of o,p′-DDT in environmental samples

The enantiomeric fractions present in soil samples may provide information useful in distinguishing recent inputs of DDT from past DDT pollution. In this study, a chromatographic procedure for the determination of the enantiomeric fractions of o,p′-DDT based on heart-cutting multidimensional gas chromatography was developed. The optimization carried out achieved low ratios of DDT degradation (<15%) in the chromatographic system. High selectivity and sensitivity in the detection of the target compounds, with a limit of detection as low as 2.1 pg μL⁻¹, was reached. In addition, high degrees of repeatability (RSD < 2.0%) and reproducibility (RSD < 3.2%) were obtained for the enantiomeric fractions measured in analytical standards and soil samples.     

The Local Linearization Method for Numerical Integration of Random Differential Equations

A Local Linearization (LL) method for the numerical integration of Random Differential Equations (RDE) is introduced. The classical LL approach is adapted to this type of equations, which are defined by random vector fields that are typically at most Hölder continuous with respect to the time argument. The order of strong convergence of the method is studied. It turns out that the LL method improves the order of convergence of conventional numerical methods that have been applied to RDEs. Additionally, the performance of the LL method is illustrated by means of numerical simulations, which show that it behaves well even in those equations with complicated noisy dynamics where conventional methods fail.AMS subject classification (2000) 34F05, 34K28, 60H25.H. Cruz: This work was partially supported by the Research Grant 03-059 RG/MATHS/LA from the Third World Academic of Science (TWAS).Received July 2004. Accepted October 2004. Communicated by Anders Szepessy.     

Mazur Intersection Properties and Differentiability of Convex Functions in Banach Spaces

It is proved that the dual of a Banach space with the Mazurintersection property is almost weak* Asplund. Analogously,the predual of a dual space with the weak* Mazur intersectionproperty is almost Asplund. Through the use of these arguments,it is found that, in particular, almost all (in the Baire sense)equivalent norms on l₁() and l() are Fréchet differentiableon a dense G subset. Necessary conditions for Mazur intersectionproperties in terms of convex sets satisfying a Krein–Milmantype condition are also discussed. It is also shown that, ifa Banach space has the Mazur intersection property, then everysubspace of countable codimension can be equivalently renormedto satisfy this property.