Conformational relaxation of S-(+)-carvone and R-(+)-limonene studied by microwave Fourier transform spectroscopy and quantum chemical calculations

S-(+)-carvone (C₁₀H₁₄O, 5-isopropenyl-2-methylcyclohex-2-en-1-one) and R-(+)-limonene (C₁₀H₁₆, 4-isopropenyl-1-methylcyclohexene) have been characterized in the gas phase using a Fourier transform microwave spectrometer coupled to a supersonic molecular beam. Two conformers—with the isopropenyl group in the equatorial position—have been detected for each compound and described by a set of molecular parameters including the principal rotational constants and the quartic centrifugal distortion parameters. Quantum chemical calculations indicate that a third conformer might not be observed due to relaxation processes in the jet. The gas phase results are compared with the liquid phase IR-Raman-VCD spectra.     

A supply chain design problem with facility location and bi-objective transportation choices

A supply chain design problem based on a two-echelon single-product system is addressed. The product is distributed from plants to distribution centers and then to customers. There are several transportation channels available for each pair of facilities between echelons. These transportation channels introduce a cost?Ctime tradeoff in the problem that allows us to formulate it as a bi-objective mixed-integer program. The decisions to be taken are the location of the distribution centers, the selection of the transportation channels, and the flow between facilities. Three variations of the classic ??-constraint method for generating optimal Pareto fronts are studied in this paper. The procedures are tested over six different classes of instance sets. The three sets of smallest size were solved completely obtaining their efficient solution set. It was observed that one of the three proposed algorithms consistently outperformed the other two in terms of their execution time. Additionally, four schemes for obtaining lower bound sets are studied. These schemes are based on linear programming relaxations of the model. The contribution of this work is the introduction of a new bi-objective optimization problem, and a computational study of the ??-constraint methods for obtaining optimal efficient fronts and the lower bounding schemes.     

Pesticide analysis in toasted barley and chickpea flours

Analytical potentiality of a modified version of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) method has been studied and validated for the extraction of a group of 11 pesticides (ethoprophos, cadusafos, dimethoate, terbufos, disulfoton, chlorpyrifos‐methyl, fenitrothion, pirimiphos‐methyl, malathion, chlorpyrifos and fensulfothion) and some of their metabolites (malaoxon, disulfoton sulfoxide, terbufos sulfone and disulfoton sulfone) in toasted barley and chickpea flours. The method involves separation and quantification by gas chromatography (GC) with nitrogen phosphorus detection (NPD) using triphenylphosphate as the internal standard. Matrix‐matched calibration was carried out for both flours due to the existence of a matrix effect. Linearity, recovery, precision and accuracy studies of the proposed QuEChERS‐GC‐NPD method were evaluated in each sample matrix. Mean recovery values were in the range of 73–118% with relative standard deviation values below 10%. Limits of detection of the whole method were between 0.07 and 57.39 μg/kg. The method was finally applied for the analysis of 14 samples collected in different zones of the Tenerife island. The residues of pirimiphos‐methyl were found in 13 of them, confirming its unequivocal presence by mass spectrometry.     

Weak ac field-induced patterns in vertical deposition of colloids at various evaporation rates

The European Physical Journal Special Topics - Pattern formation in colloids by weak ac fields in vertical deposition-like configuration at different temperatures has been studied experimentally....     

Lax entwining structures,groupoid algebras and cleft extensions

For an algebra A, a coalgebra C and a lax entwining structure (A, C, ψ), in this paper we introduce the notions of lax C-Galois extension with normal basis and lax C-cleft extension and we prove that these notions are equivalent if the functor A ? — preserve coequalizers.