Cyclodextrin-enhanced fluorescence and photochemically-induced fluorescence determination of five aromatic pesticides in water

The effect of β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) aqueous solutions upon the fluorescence and photochemically-induced fluorescence (PIF) properties of five pesticides, including coumatetralyl, pirimiphos-methyl, chlorpyriphos, deltamethrin and fenvalerate was investigated. A 1:1 stoichiometry was found for the β-CD and HP-β-CD complexes formed with all compounds. Binding constant values, ranging between about 90 and 830 M⁻¹ were calculated using the iterative nonlinear least-squares regression approach. Cyclodextrin-enhanced fluorescence and PIF methods were developed for the determination of these pesticides with linear dynamic ranges over two orders of magnitude, and limits of detection (LOD) between 0.2 and 54 ng ml⁻¹ according to the compound. Application to the analysis of tap water and river water samples yielded satisfactory recoveries (88–116%). The method seems to be suitable for environmental water analysis.     

The active analog approach applied to the pharmacophore identification of benzodiazepine receptor ligands

Summary Applied to seven potent benzodiazepine-receptor ligands belonging to chemically different classes, the active analog approach allowed the stepwise identification of the pharmacophoric pattern associated with the recognition by the benzodiazepine receptor.A unique pharmacophore model was derived which involves six critical zones: (a) a -electron rich aromatic (PAR) zone; (b) two electron-rich zones ₁ and ₂ placed at 5.0 and 4.5 Å respectively from the reference centroid in the PAR zone; (c) a freely rotating aromatic ring (FRA) region; (d) an out-of-plane region (OPR), strongly associated with agonist properties; and (e) an additional hydrophobic region (AHR).The model accommodates all presently known ligands of the benzodiazepine receptor, identifies sensitivity to steric hindrance close to the ₁ zone, accounts forR andS differential affinities and distinguishes requirements for agonist versus non-agonist activity profiles.Abbreviations Pyrazoloquinolines CGS (2-phenyl-2,5-dihydro pyrazolo [4,3-c] quinoline-3 (3H)-one) - Cinnolinones CIN (2-(4-methoxyphenyl)-benzo [h] 3-cinnolinone - Triazolophthalazines TZPH (3-(4-methoxyphenyl)-6 pyrrolidinotriazolo [4,3-a] phthalazine - Cyclopyrrolones RP 27267, CLO ([6-(5-chloro-2-pyridyl)-6,7-dihydro-7 oxo-5H-pyrrolo [3,4-b]pyrazin-5-yl] 4-methyl-l-piperazine carboxylate) - Phenylquinolines PK (phenyl-2 (morpholinocarbonyl methyl oxy)-4 quinoline - -Carbolines BCC (3-carboethoxy--carboline) - Benzodiazepines: Diazepam DZ (7-chloro-1,3-dihydro-1-methyl-5 phenyl-2H-1,4-benzodiazepin-2-one)     

Transmission and filtering in photonic circuits: effects of absorption and amplification

We study the effect of absorption and amplification on transmission and filtering in one-dimensional dielectric photonic structures made of dangling side branches grafted periodically along an infinite monomode waveguide with defective branches. The loss and gain are introduced by adding an imaginary part ″ to the dielectric constant. We show that for reasonable values of ″, loss and gain affect essentially the transmission at the frequencies of localized modes associated with the defect branch introduced into the periodic structure. The amplitude and the phase of the transmission and reflection coefficients associated with defect modes are discussed as function of ″ and the size of the structure. The properties of the defect modes in presence of loss and gain can be used as an on/off switching device in a demultiplexer made of the above photonic structures.     

Supramolecular control of charge-transfer dynamics on dye-sensitized nanocrystalline TiO2 films

A [Ru(dcbpy)(2)(NCS)(2)] dye has been chemically modified by the addition of a secondary electron donor moiety, N,N-(di-p-anisylamino)phenoxymethyl. Optical excitation of the modified dye adsorbed to nanocrystalline TiO(2) films shows a remarkably long-lived charge-separated state, with a decay half time of 0.7 s. Semiempirical calculations confirm that the HOMO of the modified dye molecule is localised on the electron donor group. The retardation of the recombination dynamics relative to the unmodified control dye is caused by the increase in the spatial separation of the HOMO orbital from the TiO(2) surface. The magnitude of the retardation is shown to be in agreement with that predicted from the non-adiabatic electron-tunnelling theory.     

Electrospray mass spectrometry of

There has been a substantial growth in the application of mass spectrometry (MS) methods for the analysis of inorganic materials, due to the inherent sensitivity of mass spectrometry ionization to the specific composition and structure of the analyzed materials. To date, few mass spectrometry studies have focused on metal-chalcogenide materials, an important class of semiconductor materials at the nanoscale, that exhibit interesting optical and electronic properties as a function of size. In this study, we report the application of a correlated electrospray mass spectrometry (ESMS) study between negative-ion and positive-ion mode under low-cone voltage to probe size, composition, and stability of metal-chalcogenide materials at the <1 nm scale. This correlation approach provides insight into the ionization behavior and thermodynamic stability of clusters in the <1.0 nm size domain of the form [Zn4(SPh)10][Me4N]2, [Cd4(SPh)10][Me4N]2, [E4Zn10(SPh)16][Me4N]4, [E4Cd10(SPh)16][Me4N]4 (E = S, Se). It is demonstrated that application of low-cone voltage ESMS can be a useful technique for the rapid analysis of intact solid state nanomaterials when both negative and positive ionic modes are analyzed, with a potential for extrapolation to other classes of nanoscale materials.     

High-sensitivity quantitation of cabergoline and pergolide using a triple-quadrupole mass spectrometer with enhanced mass-resolution capabilities

Quantitative analysis of pharmaceuticals with low systemic plasma levels requires the utmost in sensitivity and selectivity from the analytical method used. A recently introduced triple-quadrupole mass spectrometer with unique enhanced mass-resolution capability was evaluated in the analysis of two such drugs, cabergoline and pergolide, in plasma. Liquid chromatographic/electrospray ionization selected reaction monitoring determination of cabergoline in plasma at unit mass-resolution demonstrated improved sensitivity (50 fg on-column), coupled with suitable accuracy and precision over a broad linear dynamic range covering five orders of magnitude (50 fg to 5 ng on-column). Liquid chromatographic/atmospheric pressure chemical ionization selective reaction monitoring determination of pergolide in plasma also attained a high level of sensitivity (500 fg on-column) at unit mass-resolution, with accuracy and precision values well within pharmaceutical industry standards. Again, a linear dynamic range covering five orders of magnitude (500 fg to 50 ng on-column) was achieved for the assay. Utility of the enhanced mass-resolution feature of the triple-quadrupole mass spectrometer in the determination of pergolide resulted in an improvement in analyte sensitivity (250 fg on-column) and linear dynamic range (250 fg to 50 ng on-column).     

Surface free energy and bacterial retention to saliva-coated dental implant materials--an in vitro study

The aim of the present investigation was to compare the in vitro bacterial retention on saliva-coated implant materials (pure titanium grade 2 (cp-Ti) and a titanium alloy (Ti–6Al–4V) surfaces), presenting similar surface roughness, and to assess the influence of physico-chemical surface properties of bacterial strain and implant materials on in vitro bacterial adherence. Two bacterial strains (one hydrophilic strain and one hydrophobic strain) were used and the following were evaluated: bacterial cell adherence, SFE values as well as the Lifshitz-van-der Waals, the Lewis acid base components of SFE, the interfacial free energy and the non-dispersive interactions according to two complementary contact angle measurement methods: the sessile drop method and the captive bubble method.

Our results showed similar patterns of adherent bacterial cells on saliva-coated cp-Ti and saliva-coated Ti–6Al–4V. These findings could suggest that bacterial colonization (i.e. plaque formation) is similar on saliva-coated cp-Ti and Ti–6Al–4V surfaces and indicate that both materials could be suitable for use as transgingival abutment or healing implant components. The same physico-chemical properties exhibited by saliva-coated cp-Ti and TA6V, as shown by the sessile drop method and the captive bubble method, could explain this similar bacterial colonisation. Therefore, higher values of total surface free energy of saliva-coated cp-Ti and saliva-coated TA6V samples (γ_SV ≈65 mJ/m²) were reported using the captive bubble method indicating a less hydrophobic character of these surfaces than with the sessile drop method (γ_S ≈44.50 mJ/m²) and consequently possible differences in oral bacterial retention according the theory described by Absolom et al.

The number of adherent hydrophobic S. sanguinis cells was two-fold higher than that of hydrophilic S. constellatus cells. Our results confirm that physico-chemical surface properties of oral bacterial strains play a role in bacterial retention to implant materials in the presence of adsorbed salivary proteins.     

Variable Permeability Effects on Natural Convection in a Vertical Porous Layer with Uniform Heat Flux from the Side

Transport in Porous Media - Natural convection heat transfer in a rectangular cavity filled with a saturated porous medium with variable permeability is investigated analytically and numerically....