Organic and inorganic ion-exchange beads as indicators in redox and precipitation titrations

Resin beads in the Fe(III) or p-dimethylaminobenzylidene-rhodanine form are used as indicators in precipitation titrations with K(3)Fe(CN)(6), and Ag(+). Resin beads with dipheny lamine adsorbed on them can be used as indicators in cerimetric titrations. They have some advantages over conventional indicators.     

Synthesis and optimization of permselective polymer (polyindoline) film

A polyindoline permselective polymer film was readily synthesized by an electrochemical polymerization of indoline in an aqueous solution of KCl at a potential of 0.4 V vs Ag/AgCl. The amperometric responses of the polyindoline film-coated platinum electrodes to electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) substances were measured at a potential of 0.7 V. Effects of various variables such as film thickness, concentrations of monomer and electrolyte, and pH on the permselective behavior of the polymeric membrane were systematically investigated and the optimal values were determined. It was found that permselective polyindoline-coated electrodes prepared in this one-step procedure permitted hydrogen peroxide oxidation while it prevented interference due to oxidizable species such as ascorbic acid and oxalic acid. As a result, it is believed that this polymeric membrane, owing to its permselective character, can be used as the protective material in the construction of hydrogen peroxide-based biosensors. Received: 10 November 1997 / Accepted: 27 January 1998     

Lifetime-Based Oxygen Sensing Properties of palladium(II) and platinum(II) <Emphasis Type="Italic">meso</Emphasis>-tetrakis(4-phenylethynyl)phenylporphyrin

High oxygen permeable [poly(TMSP)] nanofibers incorporating porphyrin macrocycle as luminescence indicators were prepared by electrospinning technique. The porphyrins involves were modified by i) introducing phenylacetylide substituents on the para position of the phenyl moieties and ii) varying the metal centers [Pt(II) or Pd(II)] of the meso-tetrakisphenylporphyrins. A set of nanofibers; (Pt-TPP)NF, (Pd-TPP)NF, (Pt-TPA)NF and (Pd-TPA)NF were obtained to study their structure-activity relationship toward oxygen. The lifetime-based technique was privileged to take advantage of their long-lived phosphorescent properties. A two-fold enhancement was observed for (Pt-TPA)NF and (Pd-TPA)NF compared to (Pt-TPP)NF and (Pd-TPP)NF demonstrating the positive effect of the phenylacetylide moieties on the lifetime. Also, Silver nanoparticles were included in nanofibers to investigate their influence on lifetime-based oxygen sensitivity, showing that the presence of AgNPs only affects (Pd-TPA)NF.     

On closed timelike and spacelike ruled surfaces

In this study, by using the concepts and results on spherical curves in dual Lorentzian space, we give the criterions for ruled surfaces with non‐lightlike ruling to be closed (periodic). Moreover, we obtain the necessary and sufficient conditions to guarantee that a timelike or a spacelike ruled surface is closed (periodic). Copyright © 2016 John Wiley & Sons, Ltd.     

Attractors for the strongly damped wave equation with p‐Laplacian

This paper is concerned with the initial‐boundary value problem for one‐dimensional strongly damped wave equation involving p‐Laplacian. For p > 2 , we establish the existence of weak local attractors for this problem in . Under restriction 2 < p < 4, we prove that the semigroup, generated by the considered problem, possesses a strong global attractor in , and this attractor is a bounded subset of . Copyright © 2017 John Wiley & Sons, Ltd.     

Substituted 2,2′-azoquinoxaline palladium(II) complexes

2,2′-Azobis(5,6-dimethylquinoxaline) was prepared by reacting 5,6-dimethylquinoxalinone-2(1 H)-one oxime with CoCl₂. Binuclear cyclopalladated azoquinoxaline complexes were prepared from the corresponding quinoxalin-2(1 H)-one oxime and Pd(OAc)₂. This revised version was published online in June 2006 with corrections to the Cover Date.     

Application of Single‐use Electrode Based on Nano‐clay and MWCNT for Simultaneous Determination of Acetaminophen,Ascorbic Acid and Acetylsalicylic Acid in Pharmaceutical Dosage

In this study, a highly sensitive, selective and cost‐effective electrochemical nano‐sensor has been developed for the first time so as to facilitate the simultaneous and low‐level detection of acetaminophen (paracetamol, PAR), ascorbic acid (A) and acetylsalicylic acid (ASA) ternary mixture. The sensor is based on nano‐sepiolite clay (SEP) with multiwall carbon nanotubes (MWCNTs) onto electrochemically pretreated pencil graphite electrode (pPGE). The surface properties of the sensor were examined by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques. The pH effect, composition of modifiers, immobilization time, deposition potential and deposition time values were optimized to reach the best response of PAR, A and ASA. Moreover, in optimum analytical conditions, adsorptive stripping differential pulse voltammmetric (AdsDPV) method was developed for the simultaneous analysis of the ternary mixtures concerned by using SEP/MWCNTs/pPGE sensor. This sensor exhibited the low detection limits of 0.018, 0.042 and 0.047 μM for PAR, A and ASA ternary mixture, respectively. The developed AdsDPV method was applied for quantitative determination of PAR, A and ASA in the pharmaceutical formulation. The recovery experiments were carried out to control the accuracy and precision of the method. The obtained voltammetric recoveries were comparable with the HPLC data given in the literature.     

Porous superhydrophobic membranes: hydrodynamic anomaly in oscillating flows

We have fabricated and characterized a novel superhydrophobic system, a meshlike porous superhydrophobic membrane with solid area fraction Φ(s), which can maintain intimate contact with outside air and water reservoirs simultaneously. Oscillatory hydrodynamic measurements on porous superhydrophobic membranes as a function of Φ(s) reveal surprising effects. The hydrodynamic mass oscillating in phase with the membranes stays constant for 0.9?Φ(s)≤1, but drops precipitously for Φ(s)<0.9. The viscous friction shows a similar drop after a slow initial decrease proportional to Φ(s). We attribute these effects to the percolation of a stable Knudsen layer of air at the interface.