Optical characteristics of a transverse volume discharge in a helium-hydrogen chloride mixture

The emission characteristics of a transverse volume discharge in a He: HCl = 10: 1 mixture at a total pressure of 1–8 kPa were investigated. The plasma volume was 18 × 2.2 × 1 cm³, the interelectrode distance was d=2.2 cm, and the charging voltage of the main storage capacitor was 5–10 kV. The emission characteristics of the discharge were studied in the spectral range of 500–1000 nm. This type of discharge can be used in pulsed dry-etching plasmochemical reactors. The density of atomic chlorine radicals in the plasma was optimized in terms of the pressure of the initial working He-HCl mixture by measuring the relative radiation intensity of the Cl 837(5)-nm spectral line. The density of molecular radicals can be monitored indirectly by recording radiation from the excited chlorine-free decomposition products of HCl molecules (the H_α 656-nm line).     

Broadband emission spectrum of a continuous plasma jet in a mixture of noble gases with SF6 molecules

A broad band in the visible emission spectrum of a continuous Ar/Kr/SF₆ plasma jet is detected at a distance l>75 mm from the plasmatron nozzle. Experimental dependences of the maximum emission intensity on the parameters of the plasma source are presented.     

Optical characteristics of laser-produced antimony plasma

The processes occurring in expanding laser-produced antimony plasma are investigated by the emission spectroscopy method. The plasma expansion velocity, the recombination time of SbII, and the electron temperature and density are determined from the dynamics of SbI line emission. Based on the results obtained, the processes occurring during the formation and expansion of laser-produced antimony plasma are qualitatively analyzed.     

Average speaking fundamental frequency in soprano singers with and without symptoms of vocal attrition

Nineteen trained soprano singers aged 18–30 years vocalized tasks designed to assess average speaking fundamental frequency (SFF) during spontaneous speaking and reading. Vocal range and perceptual characteristics while singing with low intensity and high frequency were also assessed, and subjects completed a survey of vocal habits/symptoms. Recorded signals were digitized prior to being analyzed for SFF using the Kay Computerized Speech Lab program. Subjects were assigned to a normal voice or impaired voice group based on ratings of perceptual tasks and survey results. Data analysis showed group differences in mean SFF, no differences in vocal range, higher mean SFF values for reading than speaking, and 58% ability to perceive speaking in low pitch. The role of speaking in too low pitch as causal for vocal symptoms and need for voice classification differentiation in vocal performance studies are discussed.     

Tetrachlorosilane-Sodium Azide System in the Synthesis of Tetrazole-Containing Amino Acid Derivatives

Treatment of N-acetyl-(RS)-phenylalanine and N-acetyl-(RS)-leucine methyl esters with the system tetrachlorosilane-sodium azide leads to formation of tetrazole-containing amino acid derivatives. The latter can be converted into -substituted 5-methyl-1-tetrazolylacetic acids and the corresponding bis-tetrazoles.     

Nucleophilic Substitution of Chlorine with Hydrazine,Methylhydrazine, and 1,1-Dimethylhydrazine in 5-Aryl-2-chloromethyl-1,3,4-oxadiazoles

The reactions of 1,1-dimethylhydrazine, methylhydrazine, and hydrazine hydrate with 5-aryl-2-chloromethyl-1,3,4-oxadiazoles were studied. The structures and compositions of the final products were confirmed by ¹H NMR spectroscopy and elemental analysis.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 3, 2005, pp. 470–473.Original Russian Text Copyright © 2005 by Baranov, Tsypin, Malin, Laskin.     

Synthesis and Acidity of 5-Phenyltetrazol-2-ylalkanoic Acids and the Corresponding 5-(5-Phenyltetrazol-2-ylalkyl)tetrazoles

We have obtained 5-phenyltetrazol-2-ylalkanoic acids and their derivatives containing terminal nitrile, amide, and tetrazol-5-yl groups. Tetrazolylalkanoic acids with two (pK _a 4.93) and three (pK _a 5.45) bridging methylene groups are weaker acids than the corresponding ditetrazoles pK _a 4.68 and 5.29 respectively). However, the acidity of 5-phenyltetrazol-2-ylacetic acid (pK _a 3.12), is higher than acidity of the corresponding ditetrazole (pK _a 3.27).     

A new ligand system based on a bipyridine-functionalized calix[4]arene backbone leading to mono- and bimetallic complexes

The synthesis of a new ligand system for mono- and bimetallic complexes based on a calixarene is described. Ligand BBPC (3, bis(bipyridine)-calix[4]arene) is obtained in three steps in 40% overall yield by first brominating one of the methyl groups of the 4,4'-dimethyl-2,2'-bipyridine in two steps and subsequently reacting it with p-tert-butylcalix[4]arene under basic conditions. Reaction of BBPC (3) with 2 equiv of [Rh(NBD)(2)]BF(4) or [Rh(NBD)(CH(3)CN)(2)]BF(4) (NBD = norbornadiene) produces the bimetallic compound BBPC[Rh(NBD)BF(4)](2) (4). Treatment of the ligand with PdCl(2)(CH(3)CN)(2) leads to the isolation of the bimetallic complex BBPC[PdCl(2)](2) (5). When the nickel precursor NiBr(2)(DME) (DME = dimethoxyethane) is reacted with BBPC, the bimetallic complex BBPC[NiBr(2)](2) (6) is isolated which, upon crystallization from methanol, gives the mononuclear bis(bipyridine) complex BBPC[NiBr(OMe)] (7). Full characterization includes X-ray structural studies of complexes 4, 5, and 7. The bimetallic compounds 4 and 5 show metal to metal distances of 4.334 A (for 4) and 3.224 A (for 5). For all three complexes, unique molecular packing arrangements were found, based on hydrophobic/hydrophilic interactions.