Dimethylmalonoyl peroxide – the neglected lowest homologue: simple synthesis and high reactivity

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3,4-Epoxyperfluorooxolane in the synthesis of new fluorine-containing furo[3,4-b]quinoxaline derivatives

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Point classification of second order ODEs and its application to Painlevé equations

The first part of this work is a review of the point classification of second order ODEs done by Ruslan Sharipov. His works were published in 1997-1998 in the Electronic Archive at LANL. The second part is an application of this classification to Painlevé equations. In particular, it allows us to solve the equivalence problem for Painlevé equations in an algorithmic form.     

Bioactivity-Based Analysis of Sunscreens Using the Luminescent Bacteria Vibrio fischeri

JPC – Journal of Planar Chromatography – Modern TLC - Sunscreen products are meant to protect people from damaging UVA and UVB radiation. However, in some formulations the UV filters...     

Transversality of stable and unstable manifolds for parabolic problems arising in composite materials

In this paper we study one dimensional parabolic problems that arise from composite materials. We show that the eigenvalues and eigenfunctions of the associated linear unbounded operator have the Sturm-Liouville property and the nonincrease of the lap number along the solutions. These results are used to show that the stable and unstable manifolds of equilibrium points are transversal.     

Dispersive liquid–liquid microextraction of quinolones in porcine blood: Optimization of extraction procedure and CE separation using experimental design

A dispersive liquid–liquid microextraction procedure was developed to extract nine fluoroquinolones in porcine blood, six of which were quantified using a univariate calibration method. Extraction parameters including type and volume of extraction and dispersive solvent and pH, were optimized using a full factorial and a central composite designs. The optimum extraction parameters were a mixture of 250 μL dichloromethane (extract solvent) and 1250 μL ACN (dispersive solvent) in 500 μL of porcine blood reached to pH 6.80. After shaking and centrifugation, the upper phase was transferred in a glass tube and evaporated under N₂ steam. The residue was resuspended into 50 μL of water–ACN (70:30, v/v) and determined by CE method with DAD, under optimum separation conditions. Consequently, a tenfold enrichment factor can potentially be reached with the pretreatment, taking into account the relationship between initial sample volume and final extract volume. Optimum separation conditions were as follows: BGE solution containing equal amounts of sodium borate (Na₂B₄O₇) and di‐sodium hydrogen phosphate (Na₂HPO₄) with a final concentration of 23 mmol/L containing 0.2% of poly (diallyldimethylammonium chloride) and adjusted to pH 7.80. Separation was performed applying a negative potential of 25 kV, the cartridge was maintained at 25.0°C and the electropherograms were recorded at 275 nm during 4 min. The hydrodynamic injection was performed in the cathode by applying a pressure of 50 mbar for 10 s.     

Nitrile oxide cycloaddition to 4-hydroxy-2-cyclopentenone: Solvent effect and selectivity

The facial selectivity in the nitrile oxide cycloaddition reactions of 4-hydroxy-2-cyclopentenone and its bulky t-butyloxy derivative is reported. A quantitative evaluation of the solvent effect on the hydrogen bonding directing ability is given, showing the presence of some syn-stereoselectivity even in good H-bond acceptor solvents. The stereoselectivities of the O-t-butyl derivative may serve as reference data for more complex systems and point to the existence of a sole steric effect on the directivity; M(II) ions did not significantly improve the selectivity. The results are also discussed in light of the potential application of these scaffolds in the nucleoside analogue synthesis.     

The Magneto-Optical Voigt Parameter from Magneto-Optical Ellipsometry Data for Multilayer Samples with Single Ferromagnetic Layer

Physics of the Solid State - Calculations of the magneto-optical Voigt parameter Q were carried out using various models of reflecting media for thin films Fe|SiO2|Si(100) samples using the data of...