Dioxin analysis by gas chromatography-Fourier transform ion cyclotron resonance mass spectrometry (GC-FTICRMS)

The feasibility of utilizing a gas chromatograph-tandem quadrupole-Fourier transform ion cyclotron resonance mass spectrometer (GC-MS/MS-FTICRMS) to analyze chlorinated-dioxins/furans (CDDs/CDFs) and mixed halogenated dioxins/furans (HDDs/HDFs) was investigated by operating the system in the GC-FTICRMS mode. CDDs/CDFs and mixed HDDs/HDFs could be analyzed at 50,000 to 100,000 resolving power (RP) on the capillary gas Chromatographic time scale. Initial experiments demonstrated that 1 pg of 2,3,7,8-tetrachlorodibenzop-dioxin (TCDD) and 5 pg of 2-bromo-3,7,8-trichlorodibenzo-p-dioxin (BTrCDD) could be detected. The feasibility of utilizing an FTICRMS for screening of CDDs/CDFs, HDDs/HDFs and related compounds was also investigated by analyzing an extract from vegetation exposed to fall-out from an industrial fire. CDDs/CDFs, chlorinated pyrenes and chlorinated tetracenes could be detected from a Kendrick plot analysis of the ultrahigh resolution mass spectra. Mass accuracies were of the order of 0.5 ppm on standards with external mass calibration and 1 ppm on a sample with internal mass calibration.     

Hybrid polyoxovanadates: anion-influenced formation of nanoscopic cages and supramolecular assemblies of asymmetric clusters

Two novel hybrid polyoxovanadates that are functionalized by (4-aminophenyl)arsonic acid ligands form upon the reduction of vanadates(V) in aqueous systems, whereby the underlying condensation reactions are influenced by the nature of the employed acid. In the presence of Cl(-) ions that derive from hydrochloric acid, a tetradecanuclear cage structure [V(IV)(14)O(16)(OH)(8)-(O(3)AsC(6)H(4)-4-NH(2))(10)](4-), whose cavity contains stabilizing halide ions and water molecules, is obtained. When nitric acid is used, a decanuclear [V(10)O(18)(O(3)AsC(6)H(4)-4-NH(2))(7)(DMF)(2)](5-) cluster can be isolated. The latter organizes into a hexagonal packing arrangement in the solid state.     

Synthesis and physicochemical characterization of novel 6-aminopyrido[3,4-c][1,9]phenanthrolines as aza-analogs of benzo[c]phenanthridines

Based on the 6-aminobenzo[c]phenanthridines, a compound class showing noteworthy antitumor activity, an efficient one-step synthesis consisting of a base-catalyzed condensation of 2 equiv of 4-methylpyridine-3-carbonitrile and various aldehydes causing twofold ring closure is described. The obtained 6-amino-11,12-dihydropyrido[3,4-c][1,9]phenanthrolines could be aromatized with Pd/C at high temperatures to form 6-aminopyrido[3,4-c][1,9]phenanthrolines. All compounds were systematically characterized regarding both lipophilicity and solubility and a high cytotoxic potential was evaluated in preliminary in vitro studies. Compared to formerly described 6-aminobenzo[c]phenanthridines our newly developed phenanthrolines turned out to possess improved drugability, due to significantly increased water-solubility and decreased lipophilicity.     

Concerted and stepwise proton-coupled electron transfers in aquo/hydroxo complex couples in water: oxidative electrochemistry of [Os(II)(bpy)(2)(py)(OH(2))](2+)

Successive oxidation of transition metal(II) aqua complexes (M(II)OH(2) to M(III)OH) is a domain in which proton-coupled electron transfer reactions are extremely common. The mechanism of these PCET reactions-concerted or stepwise-is an important issue in the understanding and design of natural or artificial systems catalyzing the formation of dioxygen by four-electron oxidation of water. Concerted proton-coupled electron transfer from an aqua metal(II) to a hydroxo metal(III) complex requires the close proximity of a proton-accepting group with a pK value between those of the aqua complexes. Otherwise, stepwise electron-proton or proton-electron pathways involving high-energy intermediates are followed. Concerted proton-electron pathways involving water as proton-acceptor or proton-donor group are inefficient. Cyclic voltammetry of the title complex in buffered aqueous solution and re-examination of previous results for the same complex attached to an electrode surface are used to establish these conclusions, which provide a starting point on the route to higher degrees of oxidation, such as those involved in the catalysis of water oxidation.     

Synthesis and characterization of naphth-annelated thiophene analogs

Synthesis of symmetrical and unsymmetrical naphth-annelated thienyl heterocycles has been achieved via thionation of hydroxyketones/diketones using Lawesson's reagent. Photophysical studies of 1,3-disubstituted naphtho[c]thiophene analogs are presented. Electro-oxidative behavior of these naphtha-annelated thiophenes are investigated using cyclic voltammeter.     

Immunosensor towards low-cost, rapid diagnosis of tuberculosis

A rapid, accurate tuberculosis diagnostic tool that is compatible with the needs of tuberculosis-endemic settings is a long-sought goal. An immunofluorescence microtip sensor is described that detects Mycobacterium tuberculosis complex cells in sputum in 25 minutes. Concentration mechanisms based on flow circulation and electric field are combined at different scales to concentrate target bacteria in 1 mL samples onto the surfaces of microscale tips. Specificity is conferred by genus-specific antibodies on the microtip surface. Immunofluorescence is then used to detect the captured cells on the microtip. The detection limit in sputum is 200 CFU mL(-1) with a success rate of 96%, which is comparable to PCR.     

Time-dependent MHD Couette flow in a porous annulus

This study presents the solution for the MHD transient Couette flow in an annulus formed by two concentric porous cylinders of infinite length. The fluid flow is induced by either the impulsive or the accelerated movements of the outer cylinder. A uniform magnetic field is assumed to be applied perpendicular to the direction of flow. General solution of the governing equations is obtained using a combination of Laplace transform and the Riemann-sum approximation method of Laplace inversion. The expressions for the skin friction at the two walls are obtained in both cases. The variations of the velocity and the skin friction with respect to the Hartmann number and suction/injection parameter have been discussed. It is found out that suction accelerates the flow whereas injection retards the flow.     

Advances in analytical techniques for polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like PCBs

Analytical techniques for the determination of polychorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and dioxin-like PCBs (DLPCB) are reviewed. The focus of the review is on recent advances in methodology and analytical procedures. The paper also reviews toxicology, the development of toxic equivalent factors (TEF) and the determination of toxic equivalent quantity (TEQ) values. Sources, occurrence and temporal trends of PCDD/PCDF are summarized to provide examples of levels and concentration ranges for the methods and techniques reviewed.     

Decorrelated movements of Shockley partial dislocations in the γ-phase channels of nickel-based superalloys at intermediate temperature

In nickel-based superalloys with high volume fraction of γ′ precipitates, dislocations have to experience high curvatures in order to enter narrow channels by glide in the {111} planes of the fcc γ matrix. Observations of in situ dynamic sequences performed in a transmission electron microscope on several industrial superalloys have shown the occurrence of decorrelated movements of Shockley partial dislocations, originating from perfect dislocation dissociation. By evaluating the effective stress acting on each one of these partial dislocations, as well as their respective flexibility, the possible occurrence of such movements for some particular dislocation characters and channel widths is accounted for. These movements can play an important role in the creep behaviour of these materials in the low deformation rate regime.