Kinetics and mechanism of decomposition of intermediate complex during oxidation of pectate polysaccharide by potassium permanganate in alkaline solutions

The kinetics of decomposition of an [Pect·Mn^VIO₄^2?] intermediate complex have been investigated spectrophotometrically at various temperatures of 15–30°C and a constant ionic strength of 0.1 mol dm^?3. The decomposition reaction was found to be first‐order in the intermediate concentration. The results showed that the rate of reaction was base‐catalyzed. The kinetic parameters have been evaluated and found to be ΔS^≠ = ? 190.06 ± 9.84 J mol^?1 K^?1, ΔH^≠ = 19.75 ± 0.57 kJ mol^?1, and ΔG^≠ = 76.39 ± 3.50 kJ mol^?1, respectively. A reaction mechanism consistent with the results is discussed. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 35: 67–72, 2003     

Rheological study of multilayer functionalized polymers: characterization of interdiffusion and reaction at polymer/polymer interface

Rheological behavior in molten state of multilayered polymers was investigated by dynamic mechanical measurements. The competition between polymer/polymer interdiffusion and interfacial reaction of functionalized polymers in a sandwich structure was followed by oscillatory mode under small amplitudes of deformation. The systems chosen for study were polyethylene (PE) grafted with glycidyl methacrylate/polyamide (PA) 6 as a reactive system and PE/PA6 as nonreactive one. Moreover, the interphase thickness was estimated by using thermodynamical models. Experimental results of bilayer systems were compared to existing models of multiphase systems. An expression of storage modulus as a function of welding time was also suggested. Thus, the fit between this one and the experimental data was satisfactory with the different appearing phenomena.     

3-Methylpyrazolo [1,2-a] pyridazin-1-one. Selenium derivatives of 5,8-dihydropyrazolo[1,2-a]pyridazine

The dehydrogenation of the known 3-methyl-5,8-dihydropyrazolo[1,2-a]pyridazin-1-one (2) to the ten π electron heteroaromatic 3-methylpyrazolo[1,2-a]pyridazin-1-one ( 3 ) is reported. Conversions of the pyrazolone 2 to the pyrazoloselenone 6 via the chloropyrazolium chloride 7 , and of pyrazolones 2 and 3 and pyrazoloselenone 6 into the corresponding O or Se ethyl pyrazolium fluoroborates 5, 4 , and 8 by triethyloxonium fluoroborate are also described.     

On the class of almost L-weakly and almost M-weakly compact operators

In this paper, we introduce and study new concepts of almost L-weakly and almost M-weakly compact operators.     

Preparation of highly efficient Al-doped ZnO photocatalyst by combustion synthesis

Novel Al-doped ZnO (AZO) photocatalysts with different Al concentrations (0.5–6.0 mol%) were prepared through a facile combustion method and followed by calcination at 500 °C for 3 h. The obtained nanopowders were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM) combined with EDX, transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy and photoluminescence spectroscopy. The XRD patterns of AZO nanopowders were assigned to wurtzite structure of ZnO with the smallest crystallite size about 11 nm consistent with the results from TEM. The doping of Al in ZnO crystal structure successfully suppressed the growth of ZnO nanoparticles confirmed by XRD patterns. The absorption spectra analysis showed that the optical band gap energy (E_g) for the AZO nanopowders were in the range of 3.12–3.21 eV and decreased with increasing of Al dopant. The photocatalytic activities of the samples were evaluated by photocatalytic degradation of methyl orange under visible light (λ ≥ 420 nm) and sunlight irradiation. The results showed that the AZO photocatalyst doped with 4.0 mol% Al exhibited five times enhanced photocatalytic activity compared to pure ZnO. The enhanced photocatalytic activity could be attributed to extended visible light absorption, inhibition of the electron–hole pair's recombination and enhanced adsorptivity of MO dye molecule on the surface of AZO nanopowders.     

First principle calculation of the electronic and magnetic properties of Mn-doped 6H-SiC

The electronic and magnetic properties of 6H-SiC with Mn impurities have been calculated using GGA formalism. Various configurations of Mn sites were considered. It was found that 6H-SiC doped with Mn atoms possess a moment for both types of substitution. The Mn atom at Si site possesses larger magnetic moment than Mn atom at C site. The energy levels appearing in the band gap due to vacancies and due to Mn impurities are determined and the calculated densities of states (DOSs) are used to analyse the different value of the magnetic moments for different types of substitution. A model that explains the magnetic moment at Mn site is proposed.     

Estimation of background radiation levels and associated health risks in mineral rich district Chiniot,Pakistan

The mineral extraction activities may disturb the natural radioactivity, therefore current study aims to generate baseline data of natural radionuclides and anthropogenic ¹³⁷Cs before the start of industrial activities. Gamma spectrometry and gross alpha and beta counting systems were used for activity measurement in environmental samples. In soil, the mean activity of ²³²Th, ²²⁶Ra, ⁴⁰K and ¹³⁷Cs were determined as 79 (66–117), 47 (34–80), 823 (602–1159) and 1.3 (1.1–4.5) Bq kg^?1, respectively. The average annual effective dose rate (128.7 µSv h^?1) in the study area was twice higher than world’s average value. Indoor hazard index was greater than unity at two places; therefore, proper ventilation is proposed during construction.