Dramatic pressure-dependent quenching effects in supercritical CO2 assessed by the fluorescence of 4'-dimethylamino-3-hydroxyflavone. Thermodynamic versus kinetics control of excited-state intramolecular proton transfer

Steady-state fluorescence of 4'-dimethylamino-3-hydroxyflavone (DMA3HF) was observed in supercritical carbon dioxide (scCO(2)). Excited-state intramolecular proton transfer (ESIPT) occurs resulting in two well-separated emission bands corresponding to the normal and tautomer forms. As the scCO(2) density exceeds 0.7 g/mL, the relative intensity of the two bands tends to a constant value, comparable to that observed for organic solvents with ET(30) = 33.0 +/- 0.5 kcal/mol, such as toluene and di-n-butyl ether. At lower densities, the substantial decrease of the total fluorescence intensity (a 600-fold decrease as the pressure decreases from 100 to 80 bar) is accompanied by an even more accentuated decrease of the tautomer fluorescence. This can be explained by a shift in the equilibrium between normal and tautomer forms, concomitant with a more efficient quenching of the less solvated fluorophore, that may change the thermodynamic control of the relative population of the two emissive species to a kinetic control.     

Computer Simulation of a 5.7GHz, 110kW Transit-Time Oscillator

A high-power transit-time oscillator producing 110kW at 5.7GHz in the TM₀₁₀ cavity mode is described. The device comprises a temperature-limited diode electron gun operating at 40A in the range from 28kV to 35kV and an intermediate coaxial cavity from which the microwave power is extracted through a TEM coaxial guide. The diode serves also as a resonant cavity, where electromagnetic oscillations are grown from noise. The effect of the applied voltage on both the output microwave power and the instability saturation time has been investigated leading to an optimal diode voltage of 33kV.     

Determination of trace metal release during corrosion characterization of FeCo-based amorphous metallic materials by stripping voltammetry. New materials for GMI biosensors

The objective of this investigation has been the study of metal release during corrosion characterization of Fe_2.5Co_64.5Cr₃Si₁₅B₁₅, Fe₃Co₆₇Cr₃Si₁₅B₁₂ and Fe₅Co₇₀Si₁₅B₁₀ amorphous metallic alloys, used as based materials to create new type for giant magnetoimpedance (GMI) biosensors. Alloy samples were tested in phosphate buffered saline solutions (PBS, artificial biological solutions) at pH 7.4 and 22 °C. Individual alloy constituents (Fe, Co, Cr, B) released during the electrochemical corrosion tests, were analyzed by differential pulse stripping voltammetry (DP) using a hanging mercury drop electrode technique (HMDE). In this work, the experimental results obtained are discussed in order to study their corrosion behavior in artificial biological solutions and thus determine their possible use as GMI biosensor prototype materials.     

Sur Les Courbes Polaires D'une Courbe Plane Reduite

This paper contains results on the structure of generic localpolar curves P() of a reduced germ of a complex analytic planecurve C. We first prove a decomposition theorem of the branchesof P() into bunches. By construction, all the branches in thesame bunch have the same contact with all branches of C. Itfollows that the Puiseux expansions of all the branches of agiven bunch coincide with that of a branch of C up to an orderdepending upon the bunch. An initial part of these expansionsis therefore independant of . In the second part, we study towhat extent the contact of the branches of C with the branchesof P() determines the topological type of C. We build from thesecontacts a matrix which is determined by the topological typeof C and determines it. In an appendix, we explain how to recover,from the results of the first part, the Lê–Michel–Webertheorem on the behaviour of polar curves in an embedded resolutionof singularities of C. Cet article présente des résultatssur la structure des courbes polaires locales génériquesP() d'un germe réduit de courbe analytique complexe planeC. Nous démontrons d'abord un théorèmede déecomposition en paquets des branches de P(). Parconstruction, toutes les branches d'un même paquet ontle même contact avec chacune des branches de C. L'ensemblede ces paquets est indexé par un graphe qui ne dépendque de la topologie de la courbe C donnée. En conséquence,le développement de Puiseux de toutes les branches d'unmême paquet de P() coincide avec celui d'une branche deC jusqu'à un ordre dépendant du paquet. Une partieinitiale de ce développement est donc indépendantede . Dans la deuxième partie de ce travail, nous étudionsdans quelle mesure le contact avec les branches de C des branchesde P() détermine le type topologique de C. Nous construisonsà partir de tous ces contacts une matrice qui ne dépendque du type topologique de C et le détermine. Dans unappendice, nous montrons comment retrouver, à partirdes résultats prouvés dans la premiérepartie, le théorème de Lê–Michel–Webersur le comportement des polaires dans une résolutionplongée des singularités de C. E-mail: ergarcia{at}ull.es1991 Mathematics Subject Classification: 14H20, 32S10.     

A hard-tube pulser of 60 kV, 10 A for experiment and modeling inplasma immersion ion implantation

This paper describes an experiment and modeling in plasma immersion ion implantation using a high-voltage pulsed power system. This consists of a high-voltage pulse generator that uses a hard tube switch. The reason for using this type of circuit category in the Plasma Immersion Ion Implantation (PIII) facility rather than a previously used pulse-forming network (PFN) circuit configuration is stated. The experimental results of the application of this device to a glow discharge PIII are also discussed. In order to assess these results, a simple electrical model describes the plasma as a resistive load in parallel with a capacitance taking into account the pulse rise-time distortion caused by a long connecting coaxial cable. Plasma parameters for PIII processing, such as ion average implantation current and plasma sheath thickness, are calculated from the experimental settings     

Cladonia verticillaris (lichen) can exhibit defense mechanisms against Rn-222 under controlled conditions

Journal of Radioanalytical and Nuclear Chemistry - This study aimed to evaluate the effects of the Rn-222 progeny on the lichen Cladonia verticillaris under controlled conditions. The results...     

Analytical approach to determine biogenic amines in urine using microextraction in packed syringe and liquid chromatography coupled to electrochemical detection

The goal of this work was to develop and validate an analytical method for the detection and quantification of the biogenic amines serotonin (5‐HT), dopamine (DA) and norepinephrine (NE), using microextraction in packed syringe (MEPS) and liquid chromatography coupled to electrochemical detection (HPLC‐ED) in urine. The method was validated according to internationally accepted guidelines from the Food and Drug Administration. Linearity was established between 50 and 1000 ng/mL for 5‐HT and between 5 and 1000 ng/mL for DA and NE, with determination coefficients (R²) >0.99 for all compounds. The limits of quantification and detection were respectively 50 and 20 ng/mL for 5‐HT, and 5 and 2 ng/mL for DA and NE. Within‐ and between‐run precision ranged from 0.84 to 9.41%, while accuracy ranged from 0.79 to 12.76% for all compounds. The intermediate precision and accuracy were 1.50–8.36 and 0.54–13.51%, respectively. The method was found suitable for clinical routine analysis of the studied compounds, using a sample volume of 0.5 mL. This is the first study employing a commercially available MEPS column for the simultaneous detection and quantification of 5‐HT, DA and NE in urine by coulometric detection. Copyright © 2012 John Wiley & Sons, Ltd.