Ehrenfest's theorem reinterpreted and extended with Wigner's function

For a wave packet evolving quantum mechanically, the rates of change of the expectations and uncertainties of the position and momentum are exactly the same as if Wigner's function instantaneously obeyed a classical Liouville equation (whatever the Hamiltonian). This extension of Ehrenfest's theorem should be useful for dealing with the evolution and manipulation of quantum states.     

Conformations in the tetrahydropyran-2-one ring

Force-field calculations in combination with ¹H NMR spectroscopy, IR data and X-rays diffraction unambiguously delineate the conformational properties of tetrahydropyran-2-one derivatives which exhibit psychostimulant and antidepressive activity.     

Etude de la reactivite des coumarines—I : Regioselectivete des reactifs de grignard engages avec la coumarine

The various products obtained by the action of organomagnesium, compounds on coumarin result from 1.2-1.2 di-addition (phenolic alcohols) or 1.2–1.4 di-addition (ketophenols) or 1.4 mono-addition (dihydrobenzopyrones). The results show the importance of the nature of the halogen component of the Grignard reagent. A theoretical model allows regioselectivity of coumarine in relation to the group R and the halogene X to be evaluated.     

Stable attachment of redox groups for modified electrodes via cyanuric chloride

Methylaminopropylviologen (MAV) was covalently attached to glassy carbon electrodes via cyuranic chloride. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of bound MAV on the electrode surfaces. Electrochemical experiments of these electrodes indicated that the bound MAV was stable and electrochemically active for extended periods of time in aqueous media. The surface coverage of MAV was in the range, of 2.0–3.0×10^?10 mol cm^?2.     

Assignment of the EPR spectrum of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) superoxide spin adduct

[structure: see text] Spin trapping consists of using a nitrone or a nitroso compound to "trap" an unstable free radical as a long-lived nitroxide that can be characterized by electron paramagnetic resonance (EPR) spectroscopy. The formation of DMPO-OOH, the spin adduct resulting from trapping superoxide (O(2)(*)(-)) with 5,5-dimethyl-1-pyrroline N-oxide (DMPO), has been exploited to detect the generation of superoxide in a wide variety of biological and chemical systems. The 12-line EPR spectrum of DMPO-OOH has been either reported or mentioned in more than a thousand papers. It has been interpreted as resulting from the following couplings: A(N) approximately 1.42 mT, A(H)beta approximately 1.134 mT, and A(H)gamma(1H) approximately 0.125 mT. However, the DMPO-OOH EPR spectrum has an asymmetry that cannot be reproduced when the spectrum is calculated considering a single species. Recently, it was proposed that the 0.125 mT splitting was misassigned and actually results from the superimposition of two individual EPR spectra associated with different conformers of DMPO-OOH. We have prepared 5,5-dimethyl-[3,3-(2)H(2)]-1-pyrroline N-oxide (DMPO-d(2)), and we showed that the EPR spectrum of the corresponding superoxide spin adduct is composed of only six lines, in agreement with the assignment of the 0.125 mT splitting to a gamma-splitting from a hydrogen atom bonded to carbon 3 of DMPO. This result was supported by DFT calculations including water solvation, and the asymmetry of the DMPO-OOH EPR spectrum was nicely reproduced assuming a chemical exchange between two conformers.     

Metallic Particles from Complexing Microcapsules Dispersed in a Silica Gel

A new process to control the distribution of metal nanoparticles is proposed. It involves the use of complexing microcapsules obtained by interfacial polycondensation. The latter are hollow spheres constituted of a polymer membrane, containing an insoluble active ingredient, such as a polyacrylic acid, which can complex Co²⁺ ions. These capsules are dispersed in a silica sol followed by thermal treatments and reduction under H₂ which results in metallic Co nanoparticles confined in the capsules domains. The particles do not diffuse in the matrix.     

Relaxation spectroscopy on amorphous high polymers

Summary Measurements of the dynamic Youngs modulus and shear modulus of Polymethylmethacrylate (PMMA) in the frequency range from 10^–3 cps to 10^–1 cps and in the temperature range from –20°C to 100°C up to stress amplitudes of 4 kN/cm² are presented. The measured nonlinear viscoelastic behavior is discussed with regard to nonlinear elasticity and nonlinear effects caused by the shift of relaxation times due to the reaction rate theory.

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Zusammenfassung Es wird über Messungen des dynamischen Elastizitätsmoduls und Schubmodells von Polymethacrylsäuremethylester (PMMA) im Frequenzbereich von 10^–3 Hz bis 10^–1 Hz und im Temperaturbereich von –20°C bis +100°C bei Spannungsamplituden bis zu 4 kN/cm² berichtet. Das gemessene nichtlineare viskoelastische Verhalten wird hinsichtlich einer nichtlinearen Elastizität und hinsichtlich nichtlinearer Effekte, die durch eine Verschiebung der Relaxationszeiten nach der Platzwechseltheorie verursacht sind, diskutiert.

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With 21 figures     

Reusable ethanol sensor based on a NAD-dependent dehydrogenase without coenzyme addition

An amperometric sensor for the detection of ethanol has been designed. The sensing layer consists of alcohol dehydrogenase (ADH), NADH oxidase and NAD⁺-dextran, entrapped together in a matrix of poly(vinyl alcohol) bearing styrylpyridinium groups (PVA-SbQ). Measurements have been carried out at a low oxidizing potential (equivalent to 250 mV vs. SCE) to detect hexacyanoferrate(II), thus avoiding interferences due to presence of oxidizable compounds in real samples. The influence of the amount of polymer, enzymes and coenzyme in the sensing layer on the sensor sensitivity, linear range and operational stability has been studied. The sensitivity was close to 2 mA 1 mol⁻¹, with a linear range 3 × 10⁻⁷ −2 × 10⁻⁴M and a response time <2 min. Good operational stability was observed, allowing more than 40 reproducible assays without NAD⁺ addition. Alcoholic beverages were analysed with the use of sensor and the results showed good correlation with those obtained using a standard spectrophotometric procedure.     

Complex emulsion inversion pattern associated with the partitioning of nonionic surfactant mixtures in the presence of alcohol cosurfactant

Commercial ethoxylated nonionic surfactant mixtures containing alcohol cosurfactant exhibit a three-phase behavior whose formulation strongly varies with the water/oil ratio. As a consequence, a change in water/oil ratio can result in a sequence of up to three different emulsion inversion processes, through a combination of formulation and composition effects.