A globally convergent algorithm for determining approximate real zeros of a class of functions

BIT Numerical Mathematics - It is shown that Newton's method can be used to define a globally convergent algorithm for approximating real zeros of a certain class of functions. Included in this...     

Demodulation of AM/FM optical signals in the picosecond domain

A frequency demodulation scheme is realized to study AM/FM optical signals of picosecond duration. Ultrashort light pulses modulated by a Raman quality monochromator are analysed and the corresponding FM function is reconstructed.     

Color Bricks: Building Highly Organized and Strongly Absorbing Multicomponent Arrays of Terpyridyl Perylenes on Metal Oxide Surfaces

Terpyridine‐substituted perylenes containing cyclic anhydrides in the peri position were synthesized. The anhydride group served as an anchor for assembly of the terpyridyl‐crowned chromophores as monomolecular layers on metal oxide surfaces. Further coordination with Zn²⁺ ions allowed for layer‐by‐layer formation of supramolecular assemblies of perylene imides on the solid substrates. With properly selected anchor and linker molecules it was possible to build high quality structures of greater than ten successive layers by a simple and straightforward procedure. The prepared films were stable and had a broad spectral coverage and high absorbance. To demonstrate their potential use, the synthesized dyes were employed in solid‐state dye‐sensitized solar cells, and electron injection from the perylene antennas to titanium dioxide was observed.     

Enantioselective determination of modafinil in pharmaceutical formulations by capillary electrophoresis, and computational calculation of their inclusion complexes

A fast capillary electrophoretic method is described for the separation and determination of the enantiomers of the novel wake-promoting agent, modafinil. Several parameters affecting the separation were studied, including the type and concentration of chiral selector, buffer pH, buffer concentration, voltage and temperature. Good chiral separation of the racemic mixture was achieved in less than 5 min with resolution factor Rs?=?2.51, using a bare fused-silica capillary and a background electrolyte (BGE) of 25 mM H₃PO₄?1 M tris solution; pH 8.0; containing 30 mg mL^?1 of sulfated-β-cyclodextrin (S-β-CD). The separation was carried out in normal polarity mode at 25 ^?C, 18 kV and using hydrostatic injection. Acceptable validation criteria for selectivity, linearity, precision, and accuracy were included. The developed method was successfully applied to the assay of enantiomers of modafinil in pharmaceutical formulations. The computational calculations for the enantiomeric inclusion complexes rationalized the reasons for the different migration times between the modafinil enantiomers.     

Convenient microwave-assisted synthesis of 1-chloroethyl phosphates

An efficient microwave-assisted synthesis of 1-chloroethyl phosphates was developed. Protected vinyl chlorophosphates undergo a fast conversion to the chloroethylidene phosphates in the presence of HCl with excellent yields up to 900 times faster than at the standard NTP conditions.     

Demonstration of the Bessel-X pulse propagating with strong lateral and longitudinal localization in a dispersive medium

We report experiments on ultrashort pulses that maintain their strong lateral and longitudinal localization in a bulk linear highly dispersive medium. The diameter of the central peak and the temporal width of the field autocorrelation function of the pulses were 20mum and 210 fs, respectively, and the spatiotemporal structure was preserved in the course of 7-cm propagation in the sample. The pulses were obtained with a computer hologram designed for generating the Bessel beam and can be applied in femtosecond laser optics.     

Effect of sample matrix on the determination of total petroleum hydrocarbons (TPH) in soil by gas chromatography–flame ionization detection

Research papers in different fields of analytics indicate that the effect of matrix-induced chromatographic response enhancement (matrix effect) is a commonly encountered problem in gas chromatography applications. In this paper, an example of the effect of sample matrix on the quantitative determination of total petroleum hydrocarbons (TPH) by GC–FID in soil is presented. Two types of soil were selected for the evaluation. Extraction and analysis of the soil samples was in accordance with CEN prEN 14039. The relative systematic error resulting from the matrix effect was obtained for three different TPH concentrations by statistical comparison of the slopes of the matrix-matched calibration lines and a pure solvent calibration line. Too high TPH concentrations were obtained when conventional solvent calibration was used for quantitation. This demonstrates that matrix-matched calibration should be exploited in the determination of petroleum hydrocarbons in soil samples. However, there was also significant enhancement of the response due to an interfering matrix with decreasing analyte concentration. Enhancement seems to be especially evident in the quantification of TPH over the concentration range encountered in polluted environments. As a result, even when matrix-matched calibration is used for quantitation, it is still necessary to establish the range over which a linear response can be expected. Otherwise too high results for sample TPH concentrations will be obtained.