Alternated π‐conjugated polymers based on a 1,2‐diiminocyclohexane chiral unit for nitroaromatics sensing

The detection of 2,4‐dinitrotoluene (DNT) by fluorescence quenching of a new class of polyimines consisting in π‐conjugated segments regularly alternated with chiral C₂ symmetry units has been studied for solutions and thin films. Their photophysical properties and their sensitivity towards DNT detection has been compared to those of a small model molecule incorporating the same π‐conjugated segment. In solution, all the compounds exhibit the same photo‐physical properties and sensitivity towards DNT detection. In contrast, for thin films, better performances are observed in static conditions for this new class of polyimines compared to the small model molecule. It seems that C₂ symmetry units prevent from the stacking of the π‐conjugated segments and provide in addition to high fluorescence signal an improved diffusion of the analyte inside the films. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4141–4149, 2009     

Localization and correlation effects on the magnetoresistance of a degenerate electron gas in InAs below the quantum limit

Summary Measurements of the resistivity tensor of a range of moderately dopedn-InAs samples were carried out at low temperatures in the ionized impurity scattering regime. Analyses were performed while the electron gas was in a degenerate state and below the quantum limit. The temperature and the magnetic-field dependences of the two components of the resistivity tensor, ϱ_‖ (longitudinal) and ϱ_⊥ (transverse), were discussed in terms of localization and correlation effects.     

Polarization-insensitive cross correlation using two-photon absorption in a silicon photodiode

We present experimental measurements of the polarization dependence of two-photon absorption in silicon photodiodes at 1550 nm, and we offer a simple theory that explains our observations. Based on this theory, we propose and demonstrate that it is possible to construct an optical cross-correlation system that is polarization insensitive, provided that one of the two input polarization states can be controlled.     

Beam conditions for radiation generated by an electromagnetic Gaussian Schell-model source

It was shown recently that the basic properties of a fluctuating electromagnetic beam can be derived from knowledge of a 2 x 2 cross-spectral density matrix of the electric field in the source plane. However, not every such matrix represents a source that will generate a beamlike field. We derive conditions that the matrix must satisfy for the source to generate an electromagnetic Gaussian Schell-model beam.     

Flotation-separation of aluminum from some water samples using powdered marble waste and oleic acid.

Bench-scale experiments were conducted in the laboratory, aiming to remove aluminum from water. They were based on the use of powdered marble wastes (PMW), which are inexpensive and produced in large quantity, and thus potentially cause environmental problems, as an effective inorganic sorbent and oleic acid (HOL) as surfactant. The main parameters (solution pHs, sorbent, surfactant and aluminum concentrations, shaking time, ionic strength and the presence of foreign ions) that influence the sorptive-flotation process were examined. Good results were obtained under the optimum conditions, for which nearly 100% of aluminum at pH 7 and at room temperature (approximately 25 degrees C) was removed. The procedure was successfully applied to the recovery of aluminum spiked to some natural water samples. Moreover, a sorption and flotation mechanism is suggested.     

Über die Einwirkung von Diazomethan auf o-Chinolacetate, 6. Mitt.: Darstellung von 6-Methylindazolchinon

Zusammenfassung Es wird gezeigt, daß 6-Methyl-7-hydroxyindazol IV bei der Oxydation mit Kaliumnitrosodisulfonat in das entsprechende p-Chinon I übergeht, während bei Oxydation mit Sauerstoff oder Jod oxydative Dimerisierung zu einem Diphenochinon VI eintritt. Durch diese Versuche konnte auch die Konstitution der Verbindung, dieSpruit ² durch Einwirkung von Diazomethan auf Toluchinon erhalten hatte, gesichert werden.5. Mitt.:G. Spiteller, Mh. Chem.91, 155 (1960).     

Kinetics of the Oxidation of Tartrazine with Peroxydisulfate in the Presence and Absence of Catalysts

 The food dye tartrazine is oxidized with peroxydisulfate in the absence and in the presence of Ag(I) and Fe(III) catalysts. In the absence of these metal ions, the reaction shows second-order kinetics, first-order in each of the reacting species. With the Ag(I) ion in the medium the reaction proceeds considerably faster, but still follows second-order kinetics. The reaction rate depends on the concentration of Ag(I) and S₂O₈ ²⁻, but is independent of the concentration of the substrate. When Fe(III) acts as the catalyst, a marked enhancement in the reaction rate is observed, and the reaction proceeds through two parallel pathways, the catalyzed and the noncatalyzed. The catalyzed path follows third order kinetics, being first-order in substrate, oxidant, and catalyst concentration. Mechanisms of the noncatalyzed as well as the Ag(I) and Fe(III) catalyzed reaction systems are proposed.     

Economic and technical assessment of the desiccant wheel effect on the thermal performance of cross flow cooling towers in variable wet bulb temperature

Performance improvements of cross flow cooling towers in variable wet bulb temperature were performed. A conventional mathematical model is used to predict desiccant wheel effect on the performance of cooling tower. It is found that by using optimum parameters of desiccant wheel, the inlet air wet bulb temperature into the cooling tower would decrease more than 6 °C and outlet water temperature would decrease more than 4 °C.     

Hilbert transform and related topics associated with the differential Jacobi operator on (0, +∞)

We define Hilbert transform and conjugate Poisson integrals associated with the Jacobi differential operator on (0, +∞). We prove that these operators are bounded in the appropriate Lebesgue spaces L ^p , 1 < p < +∞. In this study, the tools used are the Littlewood–Paley g-functions associated with the Poisson semigroup and the supplementary Poisson semigroup which we introduce in this paper.