Some Area-Diameter Inequalities for Two-Dimensional Lattices

We obtain some inequalities concerning area and diameter of planar convex sets verifying the assumptions of Minkowski's Theorem, establishing the best possible upper bounds for the ratio A/D, (0,2], and for A/D when some lattice points are included.     

Micellar-stabilized room-temperature phosphorimetric determination of the fungicide thiabendazole in canned pineapple samples

A method for the determination of the fungicide thiabendazole (TBZ) by micellar-stabilized room-temperature phosphorescence is described. It does not require any separation step and allows the direct determination of the fungicide in canned pineapple samples. The effect of various experimental conditions is discussed in detail. The analytical curve of thiabendazole gives a linear dynamic range of 23.8–500.0 ng mL^–1 and a detection limit of 23.8 ng mL^–1. Recoveries of 103.9 and 89.2% for syrup and canned pineapple pulp, respectively, were obtained for 250 ng mL^–1 thiabendazole. Received: 30 April 1997 / Revised: 18 July 1997 / Accepted: 23 July 1997     

Spectrofluorimetric Determination of Methyl Paraben in Pharmaceutical Preparations by Means of its Dansyl Chloride Derivative

 A spectrofluorimetric method for the determination of methyl paraben based on derivatization with the labelling reagent dansyl chloride (DNS-Cl), is presented. The effect of the reaction variables (pH, DNS-Cl concentration, temperature, reaction time) and instrumental parameters, has been examined. A linear calibration graph in the ng/ml range has been established. The limit of detection is 18 ng/ml with relative standard deviation less than 3%. The proposed method has been satisfactorily applied to determination of the paraben in two pharmaceutical preparations. Received May 25, 1999. Revision October 20, 1999.     

Tetrathiafulvalene derivatives as NLO-phores: synthesis, electrochemistry, Raman spectroscopy, theoretical calculations, and NLO properties of novel TTF-derived donor-pi-acceptor dyads.

Novel pi-conjugated donor-acceptor chromophores, based on the strong electron-donating tetrathiafulvalene moiety and different electron-withdrawing acceptors, exhibit large second-order optical nonlinearities. The effect of increasing the length of the polyenic spacer and the influence of the nature of the acceptor moiety on the NLO properties have been studied by using the electric field-induced second-harmonic generation (EFISH) technique as well as by semiempirical and ab initio theoretical calculations. A charge-transfer band has been observed in the absorption spectra of these D-pi-A compounds that undergoes an hypsochromic shift when increasing the number of vinylenic spacer units connecting both donor and acceptor moieties. The degree of the intramolecular charge transfer from the donor to the acceptor has also been analyzed by means of Raman spectroscopy.     

Interdiffusion process in the InSe/Pt interface studied by angle-resolved photoemission

The electronic structure of the InSe/Pt interface has been studied by angle-resolved and X-ray photoemission measurements. From these results, it has been found that Pt incorporates into the InSe lattice at initial stages of Pt deposition, acting as a surface acceptor-like which tends to turn the interface into intrinsic. Beyond certain Pt submonolayer coverage, the band-bending process appears to be controlled by localized states appearing close to the Fermi level. The appearance of these states has been attributed to a reaction-like mechanism between diffused Pt and InSe atoms. For this interface, it has been found that a final electronic barrier of ∼1.2 eV is formed, close to that expected for an abrupt InSe/Pt Schottky barrier. Nevertheless, the atomic structure of the interface is far from that expected for an ideal Schottky interface.     

Polarographic studies of complexes of cadmium with chloride and thiocyanate ions in aqueous medium

This is a polarographic study of the system Cd(II)?NaCl?NaSCN in aqueous medium of a constant ionic strength of μ=1.0 M with NaClO₄. Reduction takes place through a reversible bielectronic process. The diffusion magnitudes I_d and D have been determined, and the formation of the mixed complexes CdClSCN, [CdCl₂SCN]^? and [CdCl(SCN)₂]^?, with stability constants of β₁₁=106±101² mol^?2, β₂₁=156±101³ mol^?3 and β₁₂=484±801³ mol^?3, respectively, has been demonstrated. The values of these constants are discussed in the light of statistical aspects and Watters equations.