Comparison of three sequential extraction procedures to describe metal fractionation in anaerobic granular sludges

In the last few decades, several sequential extraction procedures have been developed to quantify the chemical status of metals in the solid phase. In this study, three extraction techniques (modified [A. Tessier, P.G.C. Campbell, M. Bisson, Anal. Chem. 51 (1979) 844]; [R.C. Stover, L.E. Sommers, D.J. Silvera, J. Water Pollut. Con. F. 48 (1976) 2165]; and the Bureau Communautaire de Reference (BCR) [K.F. Mossop, C.M. Davidson, Anal. Chim. Acta 478 (2003) 111]) were applied to study the distribution of trace (Co, Ni, Zn and Cu) and major (Mn and Fe) elements in two different anaerobic granular sludges from full-scale methanogenic wastewater treatment plants. The Stover scheme displayed a higher number of fractions that induces a poor recovery compared to the other schemes. The sequential extraction scheme recommended by BCR and the modified Tessier scheme gave similar trends and are sufficiently repeatable and reproducible for application in fractionation studies. However, the BCR scheme seems to be of limited utilisation to study anaerobic matrixes because the extraction stage for its reducible fraction may release substantial amounts of trace elements bound to the organic/sulfides fraction, and consequently, the recovery of trace elements in the oxide fraction may be overestimated at the expense of the oxidisable fraction. As a final conclusion, the modified Tessier scheme seems to be the most suitable scheme to study the metal partitioning in anaerobic granular sludges.     

A Marchenko equation for complex interactions with a regular analytic continuation

Using Marchenko's own method, it is shown that three elements are required for the existence of a Marchenko fundamental equation. These are a convergent sum over the discrete spectrum, a bounded translation operator, and sometimes when there are “spectral singularities,” a domain in the complex plane of the momentum k where the representation of the regular solution as a linear combination of the two Jost solutions is meaningful. Meanwhile, we prove that for a class of complex potentials that will be called regular, a variant of Marchenko's equation exists. Clarification of the relationship between the completeness of the two sets of solutions for the unperturbed and the perturbed equation on one hand and the existence of a fundamental equation on the other hand is also achieved.     

Homotopie des foncteurs en groupes

Sans résumé     

Halogenures de tellurenyle—iii: Coupure carbone aromatique-tellure par protodetelluration et carbodetelluration intramoleculaire

In the course of electrophilic cyclisation attempts, o-phenyltellurobenzoyl-chloride did not cyclise to telluroxanthone. but isomerised to 2-chloro tellurobenzophenone through intramolecular carbodetelluration. A breaking of the same C_aromatic-Te bond is also realized by protonolysis. This last reaction leads to a preparative method of synthesis of ditellurosalicylic acid, a starting material for synthesis of benzocondensed tellurium heterocycles.     

Evaluating the profitability of advertising for heavily advertised brands: an empirical study

Even companies with large advertising budgets are sceptical of OR models in advertising—such models often appear overly complex, unrealistic and costly to use. Here a simple econometric model is proposed which utilises existing company data. The parameters are estimated for the five leading brands in a sector of the German alcoholic drinks market. Estimates of the short and long run advertising elasticities are made and optimum advertising appropriations are calculated.     

Evidence for an important 13C NMR shielding effect for carbon atoms bearing a heavy chalcogen substituent

An important ¹³C NMR shielding effect on carbons bearing a heavy chalcogen is demonstrated. This effect is parallel to that induced by iodine, but to a lesser extent. For acyclic compounds and for partially saturated heterocycles, there is an excellent linear correlation between the ¹³C chemical shifts of carbons bearing a chalcogen and carbons bearing a halogen atom in the corresponding compound. The linearity of the relationship is less satisfactory with heteroaromatic compounds.     

Horminon,Taxochinon und weitere Royleanone aus 2 abessinischen Plectranthus-Spezies (Labiatae)

Horminone, taxoquinone and other royleanones, obtained from two Abyssinian Plectranthus species (Labiatae). From the coloured glands on the leaves of two botanically unclassified Plectranthus sp. from Abyssinia, a series of royleanones has been isolated, namely royleanone ( 1 ) and 6,7-dehydroroyleanone ( 2 ) from one species, and 6,7-dehydroroyleanone, horminone ( 3 ), taxoquinone ( 4 ), 6β, 7α-dihydroxyroyleanone ( 5 ), 7α-acetoxy-6β-hydroxyroyleanone ( 6 ) and 7-oxoroyleanone ( 7 ) respectively, from the other.