Effects of Adsorbed Polyaniline on Redox Processes on As(2)O(3) Surfaces

Polyaniline deposited on As(2)O(3) surface resulted in a new material, which was characterized by infrared spectoscopy, thermogravimetry, differential scanning calorimetry, scanning electron microscopy, X-ray diffraction, and cyclic voltammetry. The mass percentage of polymer deposited on oxide surface is approximately 13%. The scanning electron microscopy images as well as the X-ray diffraction patterns provided conclusive evidence that the oxide surface is coated by the polymer. The cyclic voltammograms of the polyaniline adsorbed on As(2)O(3) surface showed that the adsorbate exerts remarkable effects on redox processes on this oxide. The pure oxide exhibited two oxidation/reduction peaks at 0.25/-0.06 and 0.47/-0.25 V attributed tentatively to the processes As(2)O(3)(s)+6H(+)+6e(-)=2As(s)+3H(2)O and As(s)+3H(+)+3e(-)=AsH(3)(g), respectively. The polyaniline-coated sample exhibited a better-defined voltammogram in which the first oxidation peak of the oxide had its intensity increased about four times. Copyright 2000 Academic Press.     

Anionic responses of electrochemically synthesized polypyrrole films

Conducting polypyrrole films with thickness of about 8 mum were prepared on platinum by continuous scanning in 0.1M pyrrole and 0.1M electrolyte (LiCl, LiBF(4) or NaBF(4)). Scan-rates of 10, 20 and 50 mV/sec with scan-times of 30, 45 and 60 min were used. The potentiometric response of the films was tested over a range of anions. Films were found to be anion-sensitive but very non-selective. The influence of the doping cation was also investigated.     

57Fe Mössbauer study of the Nurina–003 ordinary chondrite meteorite

Nurina–003 is a Group LL5/br Ordinary Chondrite meteorite which was recovered in the Nullarbor Desert (Australia) in 1986. The degree of weathering is classified as moderate to severe. We have characterised the Fe-bearing phases in Nurina–003 by ⁵⁷Fe Mössbauer Spectroscopy over the temperature range 5–295 K. The spectra are dominated by Olivine and also contain Pyroxene, Troilite and a Ferric component that is (super)paramagnetic at 295 K. We clearly see the effects of the magnetic ordering of the Olivine phase in the 5 K spectrum.     

Gas-Phase Pyrolysis of Tervalent Phosphorus-Oxy and -Thia Heterocycles: A new Approach to Short-Lived Pentavalent Phosphorus Compounds Having Co-Ordination Number 3

Abstract

Generation of short-lived metaphosphonates by thermal fragmentation of cyclic phosphonites and their thia-analogues in the gas phase is described, including an elaboration of the method whereby a monomeric phosphonobenzene is detected unambiguously for the first time by an intra-molecular trapping reaction which also illustrates the considerable potential of such species in the synthesis of phosphorus heterocycles.     

57Fe Mössbauer and magnetic studies of DyFe12−x Ta x compounds

Refinements of the X-ray diffraction patterns show that DyFe_12?x Ta _x compounds with x = 0.5–0.7 crystallise in the ThMn₁₂-type structure and that the Ta atoms occupy the 8i sites. Spin reorientations have been detected by ac magnetic susceptibility for all compounds below room temperature. First the moments shift direction from easy axis to easy cone at T _sr1, then to easy plane at T _sr2. Both T _sr1 and T _sr2 increase with increasing Ta content up to x = 0.65 before decreasing with further increase in Ta content. Analyses of the Mössbauer spectra indicate that the individual Fe site hyperfine fields derived at 4.5 K for DyFe_11.35Ta_0.65 are B _hf = 37.4 T, 32.2 T and 27.6 T for the 8i, 8j and 8f sites, respectively.     

Error growth in the numerical integration of periodic orbits by multistep methods, with application to reversible systems

We study the growth with time of (the coefficients of the asymptoticexpansion of) the error in the numerical integration with linearmultistep methods of periodic solutions of systems of ordinarydifferential equations. Particular attention is devoted to reversiblesystems. It turns out that symmetric linear multistep methodscannot be recommended in spite of the fact that they mimic thereversibility of the true flow. For reversible second-ordersystems, linear multistep methods without parasitic double rootsare useful.     

Measuring the top quark mass in the eµ channel: A study

We describe a simple method to measure the top quark mass in the channel that may be useful in Run II of D? detector. The method is validated by applying it to the Run Ib eμ data.     

Level structures of 95,97Mo — A comparative study

High-spin states of ^95,97Mo (Z=42, N=53,55) nuclei have been investigated through ⁸²Se(¹⁸O, xn) reaction at Eb=60 MeV. The level scheme in ⁹⁵Mo has been observed upto ≏ 10 MeV in the present experiment. The level structure shows mainly single particle character. In ⁹⁷Mo, the ground state level sequence has been extended to ≏ 4.5 MeV while the previous information had been up to 2.4 MeV. A negative parity band built on 1437 keV (11/2⁻) excited state has been extended to 5.5 MeV. The structure seems to show a coexistence of single particle and collective modes of excitation. Properties of both the nuclei have been compared with shell model calculations using OXBASH.