An electrochemically synthesized sulfonated polyaniline layer for positive charge carrier injection improvement in conjugated polymer devices

We report the use of sulfonated polyaniline, SPAN, as a positive charge transporting layer in organic electronic devices, demonstrating that it can be used to significantly improve injection into conjugated polymers. The introduction of an intermediate SPAN layer improves device rectification, even when low-work-function anode materials such as tin oxide are used.     

Dissolution of copper foil in aqueous solution ofpH=2

The specific dissolution rate, expressed in mol cm^–2s^–1, and time-variation of the rest potential of copper foil in an aerated aqueous solution ofpH = 2.0 were measured.

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Die Auflösbarkeit von Kupfer-Folie in wäriger Lösung von pH 2 (Kurze Mitteilung)

Zusammenfassung Es wurde die spezifische Auflösungsgeschwindigkeit (in mol cm^–2s^–1) und die zeitliche Veränderung des Restpotentials von Kupfer-Folie in einer belüfteten wäßrigen Lösung von pH 2,0 gemessen.

     

Electrocatalytic reduction of ROOH by iron porphyrins

Electrocatalytic reduction of a series of chemical oxidants of different power (tert-butyl hydroperoxide, potassium peroxomonosulfate, peracetic acid, and m-chloroperbenzoic acid) at iron-porphyrin-modified graphite electrodes is studied in buffered aqueous solutions by rotating disk and ring-disk voltammetry. Both ferric and ferrous porphyrins are catalytically active. Turnover of ferric catalysts is slower than that of the ferrous analogues and involves competing catalytic reduction and disproportionation. The kinetic data are consistent with reactant binding being the rate-determining step in catalysis by Fe(III). In catalysis by Fe(II), the turnover is controlled by the first electron transfer. The covalently linked proximal imidazole ligand is found to be crucial for achieving the Fe(III) catalysis.     

Quantitative determination of acetylsalicylic acid and acetaminophen in tablets by FT-Raman spectroscopy

A procedure for quantitative determination of acetylsalicylic acid and acetaminophen in pharmaceuticals by PLS (partial least squares) and PCR (principal component regression) treatment of FT (Fourier transform)-Raman spectroscopic data is proposed. The proposed method was tested on powdered samples. Three chemometric models were built: the first, for samples consisting of an active substance diluted by lactose, starch and talc; the second, in which a simple inorganic salt was applied as an internal standard and additions were not taken into account; and the third, in which a model was constructed for a commercial pharmaceutical, where all constituents of the tablet were known. By utilising selected spectral ranges and by changing the chemometric conditions it is possible to carry out fast and precise analysis of the active component content in medicines on the basis of the simplified chemometric models. The proposed method was tested on five commercial tablets. The results were compared with data obtained by intensity ratio and pharmacopoeial methods. To appraise the quality of the models, the relative standard error of predictions (RSEPs) were calculated for calibration and prediction data sets. These were 0.7-2.0% and 0.8-2.3%, respectively, for the different PLS models. Application of these models to the Raman spectra of commercial tablets containing acetylsalicylic acid gave RSEP values of 1.3-2.0% and a mean accuracy of 1.2-1.7% with a standard deviation of 0.6-1.2%.     

Increased structural complexity leads to higher activity: peptides as efficient and versatile catalysts for asymmetric aldol reactions

[reaction: see text] Peptides containing a secondary amine and a carboxylic acid in a specific orientation to each other are presented as highly efficient catalysts for asymmetric aldol reactions: (1) their activity is considerably higher compared to that of proline, and (2) the enantioselectivity of the peptidic catalysts can be changed from (R)- to (S)-selectivity by simple modifications of the secondary structure.     

Coordination de la phosphine organo-fer [CpFeIIC6Me5CH2PPh2]+ au RhI et proprietes spectroscopiques,electrochimiques et catalytiques des complexes heterobinucleaires FeII-RhI

The reactions between the phosphine-organoiron [CpFe^II-η⁶-C₆Me₅CH₂PPh₂]⁺ PF₆^? (1) and [RhCl(η⁴-diolefin)(μ-Cl)]₂ in CH₂Cl₂ at reflux give the new heterobinuclear air-stable crystalline complexes [CpFe^II-η⁶-C₆Me₅CH₂)P(Ph)₂Rh(η⁴-diene)Cl]PF₆,(D'*-diene=cyclooctadiene (COD): 65%, 2; trimethylfluorobenzobicyclo[2.2.2]octadiene (Me₃TFB): 48%, 3). Complexes 2 and 3 have been studied by ¹H, ¹³C and ³¹P NMR spectroscopy and they are carbonylated (CO, 1 atm). Cyclic voltammetry experiments with addition of MeOH show electron transfer Fe^IRh^I → Fe^IIRh⁰, the presence of a catalytic wave Fe^I/Fe^II and the possible formation of Rh hydrides. Under normal conditions 2 is a catalyst for hydrogenation of cyclohexene, but it is less efficient than the known mononuclear Rh¹ analogues.     

The Inverse Scattering Method and Systems of Equations qxy = F(q,qy)

Consider equations of the form where q is in general a complex vector and the function F depends nontrivially both on q and on q_y. We show that a family S of such equations can be investigated by the inverse scattering method. If an equation (*) belongs to S, the function F depends linearly on q and algebraically on q_y. We show that the family S contains a subfamily in which each equation can be obtained from the two dimensional Toda lattice equations by a Bäcklund transformation.     

The stability of the exponential equation

We generalize the well-known Baker's superstability result for exponential mappings with values in the field of complex numbers to the case of an arbitrary commutative complex semisimple Banach algebra. It was shown by Ger that the superstability phenomenon disappears if we formulate the stability question for exponential complex-valued functions in a more natural way. We improve his result by showing that the maximal possible distance of an -approximately exponential function to the set of all exponential functions tends to zero as tends to zero. In order to get this result we have to prove a stability theorem for real-valued functions additive modulo the set of all integers .

     

Separation techniques for biotechnology in the 1990s.

Scientists are constantly looking for better and cheaper separation techniques to replace or complement the current technology. Over the past few decades, and in particular the last 10 years, new separation techniques or modifications of existing techniques have become available for separating compounds from complex sample matrices. There are many areas, however, where the separation technology is not sufficient to achieve high purity and yield while remaining cost effective. In the area of biotechnology, separation techniques are urgently needed to meet demands for ultra-high purity and yield. Thus, a variety of techniques are being developed to address these needs. Generally, biological compounds for the pharmaceutical and biotechnology industries must be obtained at greater than 99.9% purity (sometimes greater than 99.99%) while maintaining high yield. In any area of chemistry this degree of purity would cause problems; in biotechnology it is even more difficult to achieve because of the complex sample matrices. In addition, the compounds of interest may be very similar to impurities or contaminants in the sample matrix, and the compounds could be denatured (or even destroyed) by certain solvents and/or high temperature. In particular, three areas of biotechnology have presented scientists with problems in separations: cell separations, DNA-RNA separations, and protein-peptide separations. The current technology available and possible future trends in these areas are discussed, and also problems to be solved in the future.     

Calculs de complexité relatifs à une méthode de dissection emboîtée

Résumé Nous présentons une numérotation de type Nested Dissection des inconnues d'un système linéaireAX=B pour des ensembles de matricescreuses symétriques définies positives correspondant à des famille de graphes non orientés,à degré borné, et admettant un -thérème de séparation. Comparativement aux méthodes et résultats de Rose [9], l'algorithme présenté est plus simple, mais les théorèmes de complexité moins généraux, en raison de l'hypothèse restrictive de degré borné. En outre, les démonstrations font appel en permanence à la structure d'arbre sur la famille des séparateurs qui constitue, par ailleurs, une partition de l'ensemble des sommets du graphe initial. Nous présentons ensuite le schéma général d'implémentation dans le cadre du code d'éléments finis MODULEF pourdes problèmes plans d'éléments finis, et nous donnons quelques mesures comparatives avec la numérotation plus classique qui tend à minimiser le profil de la matrice.

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Complexity bounds for a nested dissection method

Summary A nested dissection ordering is given for solving any system of linear equationsAX=B, for the family ofsparse symmetric positive definite matrices corresponding to the class of undirected graphs withbounded degree, and satisfyinga -separator theorem. If we compare the methods and results presented by Rose [9], our algorithm is more simple, but the complexity results are less general because of the restriction of bounded degree. Besides, our proofs use continually the arborescent structure on the family of separators, which is, by another way, a partition of the set of vertices for the initial graph. Then, the general implementation scheme in the finite element package MODULEF, fortwo-dimensional finite element problems, is presented, and numerical comparisons between our ordering and the standard envelope method are given.