Synthesis and characterization of thiophene/3-alkylthiophene random cooligomers

Several random cooligomers based on thiophene and β-substituted alkyl derivatives, i.e. 3-methyl- and 3-octylthiophene, have been chemically synthesized by an oxidative coupling reaction in the presence of iron(III) chloride. The powdered samples were characterized by TGA, FTIR, UV and cyclic voltammetry measurements. The influence of the alkyl substituent on the homo/cooligomer stability, conjugation length, degree of polymerization and presence of defects is discussed. Electronic Publication     

A pyrrolo-tetrathiafulvalene belt and its TCNQ complex: syntheses and X-ray crystal structures

A general and efficient four-step synthesis of a tetrathiafulvalene-belt 6, starting from the monopyrrolo-tetrathiafulvalene building block 1, is described, together with its 7,7,8,8-tetracyano-p-quinodimethane charge transfer complex. The complexation of the electron acceptor 7,7,8,8-tetracyano-p-quinodimethane by the tetrathiafulvalene-belt 6 was investigated both in solution and in the solid state. [reaction: see text]     

Some results on Borel structures with applications to subseries convergence in abelian topological groups

We show that in an abelian topological group subseries convergence depends only on the Borel field generated by the topology. We also prove a result about measurability of a limit for a pointwise converging sequence of measurable mappings into an analytic topological space.     

The normalization of the muon-decay current

A normalization condition for the muon decay current in V-A theory with radiative corrections included is obtained by the requirement that the generalized charges corresponding to the constituents of the current should fulfil an appropriate charge algebra. It is shown that the radiative corrections in second order are uniquely fixed by this requirement. The calculation is performed without the use of a cut-off. If the corresponding current algebra is postulated, the currents which, according to Adler, describe scattering of neutrinos on charged leptons, are completely determined. It is pointed out that Adler's Lagrangian for this process must be reduced with a factor $\text{1}\text{2}$ in order to make leptonic spin symmetric the whole interaction Lagrangian for leptonic processes.     

Reduced microdeformation attenuation in large-mode-area photonic crystal fibers for visible applications

We consider large-mode-area photonic crystal fibers for visible applications in which microdeformation-induced attenuation becomes a potential problem when the effective area A(eff) is sufficiently large compared to lambda2. We argue that a slight increase in fiber diameter D can be used in screening the high-frequency components of the microdeformation spectrum mechanically, and we confirm this experimentally for both 15- and 20-microm core fibers. For typical bending radii (R approximately 16 cm) the operating bandwidth increases by approximately 3-400 nm to the low-wavelength side.     

Unusual observation of nitrogen chemical shift anisotropies in tetraalkylammonium halides by 14N MAS NMR spectroscopy

¹⁴N Magic-angle spinning (MAS) NMR spectra for a number of polycrystalline, symmetrical tetraalkylammonium halides with short alkyl chains (C₂H₅– to n-C₄H₉–) have been recorded following a careful setup of the experimental conditions. Analysis of the spectra demonstrates the presence of ¹⁴N chemical shift anisotropies (CSAs) on the order of |δ_σ|=10–30 ppm along with ¹⁴N quadrupole coupling constants in the range of 10–70 kHz. The magnitude and sign of the CSAs determined from ¹⁴N MAS NMR are confirmed by recording and analysis of the corresponding slow-speed spinning (500–650 Hz) ¹⁵N CP/MAS NMR spectra. Most interestingly, it is observed experimentally and demonstrated theoretically and by simulations, that these CSAs are reflected in the spinning sideband (ssb) intensities of the ¹⁴N MAS spectra at much higher spinning speeds than can be applied to retrieve the corresponding ¹⁵N CSAs from the ssb pattern in the ¹⁵N CP/MAS spectra.     

Divisibility in the K0‐Group of the Algebra of Operators on a Banach Space

Let Figiel's reflexive Banach space which is not isomorphic to its Cartesian square. We show that the K ₀group of the algebra of continuous, linear operators on contain a subgroup isomorphic to the group c ₀₀( ) of sequences rational numbers with z _n=0 eventually.     

A class of elliptic pseudo differential operators generating symmetric Dirichlet forms

It is shown that a special class of symmetric elliptic pseudo differential operators do generate a Feller semigroup and therefore a non-local Dirichlet form.     

Application of a fundamental parameter technique for solving peak-overlap problems in quantitative energy-dispersive x-ray fluorescence spectrometry

The procedure exploits the fundamental parameter technique for monoenergetic excitation. The algorithm describes each peak as a sum of line intensities, thus intensities from unresolved lines are included directly in the equations. The procedure includes the condition that the sum of all weight fractions equals unity, and so is valid only when all elements are measured by x-ray fluorescence spectrometry, e.g., in steel alloys. The procedure is tested with a set of theoretically calculated x-ray fluorescence intensities, and for two NBS standard steel alloys.