Electron localization in disordered one-dimensional systems and solitary waves in Ginzburg-Landau (ø4) field theory

The formal equivalence between a Ginzburg-Landau field theory with zero field dimensionality, and the problem of an electron scattered by random potentials, suggest that, since the latter has only localized solutions, the former problem has only solitary wave solutions.     

Electrophoresis microchip fabricated by a direct-printing process with end-channel amperometric detection

We describe the development of an electrophoresis microchip fabricated by a direct-printing process, based on lamination of printed polyester films with end-channel amperometric detection. The channel structures are defined by polyester (base and cover) and by a toner layer (walls). The polyester-toner devices presented an electroosmotic flow (EOF) magnitude of approximately 10(-5) cm2 V(-1) s(-1), which is generated by a polymeric mixture of the toner and polyester composition. The microelectrodes used for detection were produced combining this laser-printer technology to compact discs. The performance of this device was evaluated by amperometric detection of iodide and ascorbate. The detection limits found were 500 nmol.L(-1) (135 amol) and 1.8 micromol.L(-1) (486 amol) for iodide and ascorbate, respectively.     

Indium(III) bromide catalyzed one-pot synthesis of trichloromethylated tetrahydropyrimidinones

One-pot condensation of ethyl trichloroacetoacetate 1 with p-substituted aromatic aldehydes (Ph, 4-Me-C₆H₄, 4-Cl-C₆H₄, 4-MeO-C₆H₄) or furfural, and urea or thiourea catalyzed by indium(III) bromide affords eight trichloromethylated tetrahydropyrimidinones, in high yields.     

Conductivity detection of aliphatic alcohols in micellar electrokinetic chromatography using an oscillometric detector

Although conductivity is usually applied to detect ionic species in capillary electrophoresis (CE), nonionic species can also be detected by their indirect effects on the conductivity of the running electrolyte. This approach was used for detection of aliphatic alcohols in micellar electrokinetic chromatography (MEKC) with an oscillometric detector. Although the detector operates at 600 kHz, for the range of electrolyte concentration used in CE, the response is mainly due to variations of conductivity. A 50 mM phosphate and 50 mM SDS solution was used as running electrolyte and as the solvent for mixtures of some isomers of propanol, butanol, and pentanol. A set of negative peaks was obtained and assigned to the components by spiking the samples. The limits of detection (LOD) ranged from 2.1 mM for 2-methyl-2-propanol to 5.3 mM for 1-pentanol. Due to the high affinity for the interior of the micelles, 1-hexanol could not be easily-detected, but by the addition of 10% methanol to the running electrolyte it was possible. For this electrolyte, the LOD was improved, ranging from 0.8 mM for 2-methyl-2-propanol to 1.5 mM for 1-pentanol. Calibration plots were linear up to 40 mM at least. These results indicate that conductivity may be useful for detection of nonionic species in CE, especially when optical methods can not be conveniently applied.     

2,2′-Bipyridine-6,6′-bis(carbothioamide) metal complexes

Complexes of 2,2-bipyridine-6,6-bis(carbothioamide), obtained with a variety of metal cations, were characterised by microanalyses, molar conductivities and by i.r. and n.m.r. (for diamagnetic compounds) spectra. The iron(II) complex was also characterised by Mössbauer spectroscopy. The spectral data indicate that, in all cases, the ligand coordinates to the metal through one pyridine nitrogen and one sulphur.     

Requirements for Efficient Raman Amplification and Dispersion Compensation Using Microstructured Optical Fibers

The design and performance of microstructured optical fibers (MOFs) for simultaneous dispersion compensation and Raman amplification is numerically investigated. We studied a lumped Raman amplifier designed to compensate the signal loss and dispersion introduced by a 100-km, 16-channel C-band WDM link. The impairments induced by the nonlinearities caused by the small mode area of the designed MOF are investigated and the analysis is extended to include non-ideal factors such as excess background losses, splice loss, and the geometry variations during the fabrication process. The results are discussed and compared to those obtained for conventional dispersion compensating fibers (DCFs).     

Chiral separation of gamma-butyrolactone derivatives by gas chromatography on 2,3-di-O-methyl-6-O-tert.-butyldimethylsilyl-beta-cyclodextrin

The chiral GC separation of 2-alkyl-2-keto-gamma-butyrolactone derivatives and their alcohol analogs using 2,3-di-O-methyl-6-O-tert.-butyldimethylsilyl-beta-cyclodextrin (DIMETBCD) as chiral selector was discussed. The results, supported by the ketone preliminary molecular modelling calculations, suggest that the chiral recognition for DIMETBCD depends more on the geometry than on the polarity of the alkyl substituents on the butyrolactones. Hydrogen bonds and alkyl group steric effects should be an important function of the alcohol chiral recognition for DIMETBCD. Comparison of the retention times of the alcohol derivatives, in achiral and chiral stationary phases, suggests a specific structural effect for the cyclodextrin selctor.