Coherent single pion production by antineutrino charged current interactions and test of PCAC

The cross section for coherent production of a single π^? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10^?40 cm²/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ ² dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.     

A SPIN TRAPPING STUDY OF THE PHOTOCHEMISTRY OF 5,5-DIMETHYL-1-PYRROLINE N-OXIDE (DMPO)

The photochemistry of 5,5-dimethyl-l-pyrroline N -oxide (DMPO) has been studied in benzene, cyclohexane and aqueous buffer solutions (pH 7.4) by means of electron paramagnetic resonance (EPR) and the spin trapping technique. Ultraviolet irradiation of DMPO in aqueous buffer with unfiltered UV radiation from a Xe arc lamp results in photoionization of the spin trap and the generation of the DMPO cation radical, DMPO⁺. The aqueous electron, e_aq⁻, was trapped by DMPO and detected as the DMPO/H adduct. The DMPO⁺- reacted with the water to yield the DMPO/OH adduct. Ultraviolet irradiation of DMPO in nitrogen-saturated benzene gave an unidentified carbon-centered DMPO adduct that was replaced by hydroperoxyl and alkoxyl adducts of DMPO when oxygen was present. Experiments employing ¹⁷O₂ gas indicated that the oxygen in the DMPO alkoxyl adduct was derived from molecular oxygen. However, UV irradiation of DMPO in cyclohexane yielded the cyclohexyl and cyclohexyloxyl adducts of DMPO in nitrogen-saturated and air-saturated solutions, respectively. These observations suggest that in aprotic solvents UV irradiation of DMPO generates a carbon-centered radical (R⁻), derived from the trap itself, which in benzene reacts with oxygen to yield an alkoxyl radical (RO⁻), possibly via a peroxyl radical (ROO⁻) intermediate. In cyclohexane R⁻ abstracts a hydrogen atom from the solvent to yield the cyclohexyl radical in the absence of oxygen and the cyclohexyloxyl radical in the presence of oxygen. These findings indicate that when DMPO is used as a spin trap in studies employing short-wavelength UV radiation (λ < 300 nm) the photochemistry of DMPO cannot be ignored.     

Charge reversal of three alkylamide ions: Free nitrenium ions

The methylnitrenium, ethylnitrenium and dimethylnitrenium ions are prepared by charge reversal collisional activation (CR CA) of the corresponding negative ions; their collisional activation mass spectra are shown to support the assigned structures. MINDO/3 energies are used to evaluate relative energies of [CH₄N]⁺ and [C₂H₆N]⁺ isomers, and to determine whether unstable forms rearrange spontaneously to stable ones. As in other examples, charge reversal here generates cations that do not exist in an energy well, but their transient existence is established because their fragmentation is more rapid than their rearrangement to a more stable form.     

The synthesis of some optically active C-methylated 2-oxohexamethyleneimines

Three new, optically active, methyl-substituted 2-oxohexamethyleneimines were prepared by cyclization of the respective optically active C-methylated 6-aminohexanoic acids. The active forms of the amino acids used for the preparation of (?)-3-methyl-2-oxohexamethyleneimine and (?)-7-methyl-2-oxohexamethyleneimine were obtained by resolution of their diastereomeric quinine salts. s-(+)-5-methyl-2-oxohexamethyleneimine was synthesized without racemization from optically pure 2-isopropylidene-5-methyleyclohexanone (pulegone).     

Detection of the pesticide compound 1080 (sodium monofluoroacetate) using fluorine-19 nuclear magnetic resonance spectroscopy

Fluorine-19 nuclear magnetic resonance (19F NMR) spectroscopic measurements were used to determine the chemical nature and amounts of organofluorine in dosed meat baits. Earlier work implied that sodium monofluoroacetate (compound 1080) in meat baits was broken down into other organofluorine compounds such as fluorocitrate. No chemical evidence was found for such compounds. Only monofluoroacetate was detected in the prepared 1080 bait samples. Once the baits have aged, aqueous extraction fails to recover all the added 1080. Analysis using 19F NMR confirmed that the 1080 present in the aqueous extracts of the bait is recovered by Kramer's liquid chromatography method. It was shown here that the aqueous extracts do not recover all the 1080 in the meat bait.     

Heat-resistant metal phthalocyanine imide copolymers

Thermally stable poly(metal phthalocyanine)imide copolymers were prepared with metal(11) 4,4′,4″,4? -phthalocyanine tetraamines, 4,4′ -diamino diphenyl ether, and 3,3′,4,4′ -benzophenone tetracarboxylic dianhydride. Variables such as molar concentrations of the reagents, solvents, and temperature were investigated to optimize the conditions of the polymerization. Inherent viscosity, and infrared (IR) spectral and thermogravimetric analysis (TGA) studies were done to characterize the polymers. These polymers are stable and thier decomposition temperatures both in air and nitrogen are greater than 500°C. Their char yields at 800°C in nitrogen varied between 60 and 76%, depending on the type and concentrations of the metal phthalocyanine tetraamines. These polymers can be used to produce heat-stable films, fibers, varnishes, and adhesives.     

A new solid-phase polymerization—metal phthalocyanine sheet polymers

The thermal reactions of pure metal(11) 4,4′,4″,4′″-phthalocyanine-tetracarboxylic acids of copper, cobalt, and nickel at 350–400°C in vacuum have been studied using Fourier transform infrared spectrometry, gas chromatography, and mass spectrometry. Based on these observations, novel in situ reactions for the synthesis of heat-resistant phthalocyanine “sheet” polymers are described. The poly(metal phthalocyanine) polymers of copper, cobalt, and nickel so synthesized have been characterized by elemental analysis, infrared spectroscopy, and dynamic thermogravimetric analysis. The most noteworthy property of these polymers is their extreme resistance to heat in an anaerobic atmosphere and their high char yields (89–93%) at 800°C in a nitrogen atmosphere.     

Mass transfer of oxygen in poly(2-hydroxyethyl methacrylate)

The diffusion coefficient of oxygen in poly(2-hydroxyethyl methacrylate) has been explicitly measured using an optical technique based on fluorescence quenching. This measurement represents the first explicit determination of D in PHEMA. A diffusion coefficient of oxygen in PHEMA of 1.36 × 10^?7 cm²/s at 20°C was obtained from this measurement. This value is shown to agree well with permeability data for PHEMA, the free volume theory of diffusion, and with values of D that have been explicitly measured in other methacrylate hydrogels.     

Preparation and properties of some α-aza-amino-acid derivatives,their possible use in peptide synthesis

Some derivatives of azaglycine and azaphenylalanine are described. Esters of acetyl- and benzoyl-aza-amino-acids rapidly cyclise to stable oxadiazolones and it is concluded that similar derivatives would be unsuitable for aza-peptide synthesis. t-Butyloxycarbonyl-azaglycine azide was too unreactive for use in peptide synthesis. Benzoyl-azaglycylphenylalanine ethyl ester and acetyl-azaphenylalanylphenylalanine ethyl ester were prepared by coupling benzoyl hydrazide and N-acetyl-N'-benzylhydrazide respectively with 2,4-dinitrophenyloxycarbonyl-phenylalanine ethyl ester.