Chemistry of the Positive and Negative Electrical Discharges Formed in Liquid Water and Above a Gas–Liquid Surface

The physical processes and chemical reactions that take place inside different temperature plasma zones in water are only partially understood. The present study uses the emission spectroscopy and hydrogen peroxide measurements as indicators of the processes that take place on the gas–liquid boundary and inside plasma. Based on the hydrogen peroxide measurements with negative and positive high-voltage polarities as a function of solution conductivity, it was concluded that the main difference between positive polarity plasma and negative polarity plasma lies in the active radical concentration inside plasma. Data suggested that in the positive polarity electrical discharge the hydrogen peroxide concentration depends on the solution pH, whereas in the negative polarity discharge, it depends on the solution conductivity. Also, only in the negative polarity discharge do some of the electrons that are emitted from the high voltage electrode diffuse into the bulk where they react with the solutes.     

Effect of organophosphate antioxidant on the thermo-oxidative degradation of a mineral oil

This study shows the synthesis, characterization, and evaluation of the effect of organophosphate antioxidant on the thermo-oxidative degradation of a mineral oil. The organophosphate was synthesized by nucleophilic substitution (S_N2) of hydrogenated cardanol. For this study, were employed thermogravimetry, derivative thermogravimetry, differential scanning calorimetry, and differential thermal analysis techniques. The results showed that organophosphate contributed for thermo-oxidative stability of mineral oil (initial decomposition temperature (IDT) mineral oil: 91.28 °C < IDT mineral oil + organophosphate (1%): 156.42 °C). The organophosphate obtained shows significant thermal stability when compared with other compound of the same class (diphenyl phosphate).     

The effects of ZnGa2O4 formation on structural and optical properties of ZnO:Ga powders

Gallium-doped zinc oxide (ZnO:Ga 1, 2, 3, 4 and 5 at%) samples were prepared in powder form by modifying the Pechini method. The formation of zinc gallate (ZnGa₂O₄) with the spinel crystal structure was observed even in ZnO:Ga 1 at% by X-ray diffraction. The presence of ZnGa₂O₄ in ZnO:Ga samples was also evidenced by luminescence spectroscopy through its blue emission at 430 nm, assigned to charge transfer between Ga³⁺ at regular octahedral symmetry and its surrounding O²⁻ ions. The amount of ZnGa₂O₄ increases as the dopant concentration increases, as observed by the quantitative phase analysis by the Rietveld method.     

Luminescence quenching of [Ru(bpy)3] by ruthenium(II) tetraphosphite complexes with different phosphite ligands

The luminescence quenching of excited Tris(2,2-bipyridine)ruthenium(II) ions by trans-[RuCl₂{P(OR)₃}₄] complexes with different alkyl chain ligands (R=C₂H₅, C₂H₅Cl, ⁿC₄H₉, ⁱC₃H₇ o-tolyl and ^tC₄H₉) was investigated. None of the acceptor Ru(II) phosphite complexes were luminescent, and the rate constants of the bimolecular system were determined within the range of 1.15 and 0.28×10⁸ M⁻¹ s⁻¹ for R=C₂H₅ and ^tC₄H₉, respectively. The results indicate a direct effect of the alkyl chains in the rate constants, showing a decrease of k_q as a function of increased of the alkyl chains (R) in the ruthenium(II) tetraphosphite complexes. The greater the R group content in the phosphite ligand, the more difficult the electron transfer is.     

Dichloromethane alkylates a trithiolato-ruthenium complex to yield a methylene-bridged thioether core. Synthesis and structural comparison to the thiolato-ruthenium precursor

The previously reported triphosphino/trithiolato-ruthenium anion, [tris-(2-diphenylphosphinothia-phenolato)ruthenium(II)](-), [Ru(DPPBT)(3)](-), has been isolated as the PPN salt (PPN = bis(triphenylphosphoranylidene) ammonium), 1, from chlorobenzene/ether as light-orange crystalline plates, and the X-ray crystal structure has been determined. In dichloromethane, the cis positioned thiolates are alkylated by solvent yielding the methylene-bridged triphosphino/dithioether/thiolato complex [(bis-(2-diphenylphosphinothiaphenolato)methane)(2-diphenyl-phosphinothiaphenolato)ruthenium(II)]chloride, [Ru((DPPBT)(2)CH(2))(DPPBT)]Cl (2). Dichloromethane solutions of 1 layered with hexanes yield 2 as orange cubes. The ruthenium-sulfur bond distances in the alkylated, thioether product are slightly shorter than in the thiolate precursor. Within 2, the iron-thioether bond distances are comparable to the iron-thiolate distances.     

A computer model for predicting sound attenuation by barrier-buildings

This paper describes a computer technique involving a procedure for finding the performance values within the shadow zone of a barrier-building of rectangular cross-section used as a point source. Reflections from the ground are also taken into account and a control operation is designed for different source and receiver locations related to the building. Consideration is given to the combined effects of wide barriers and finite size screens. The results are confirmed by several experimental measurements carried out in an anechoic room. Some examples of the application of the technique are given.     

2S autoionizing states of lithium

The energy positions and the wavefunctions of ²S autoionizing states of the neutral lithium atom have been calculated using the derivative method with a Hylleraas-type basis set. Computed energies are in good agreement with experiment and with other theoretical results.     

Detecting naphthenic acids in waters by gas chromatography-mass spectrometry

Naphthenic acids (general formula C(n)H(2n+Z)O(2)) are water-soluble, toxic compounds found in petroleum and bitumen. Some of the current methods for detecting these acids in waters depend on measuring the presence of the carboxylic acid functional group, and therefore many of these methods also detect naturally occurring carboxylic acids that are not naphthenic acids. We report a procedure that includes liquid-liquid extraction, cleanup, and derivatization to form t-butyldimethylsilyl esters prior to gas chromatography-mass spectrometry (GC-MS) analysis. Using low- and high-resolution MS to detect the ion C(15)H(27)O(2)Si(+) (nominal m/z=267) is an excellent indicator of the presence of naphthenic acids at concentrations > or =10microgL(-1).