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Notes: The downstream near afterglow region of a hydrogen plasma is used to decompose and convert trimethylarsine (TMAs) into methylarsine homologs [(CH3)3−xAsHx, where x=1,2,3] including that of arsine (x=3). Approximately 30%, 17%, and 10% of the TMAs is converted into dimethylarsine (DMAs), monomethylarsine (MMAs), and arsine, respectively, while 28% remains undecomposed. Hydrogen is replaced by deuterium to isotopically verify that the origin of the arsenic hydrogenation occurring during gas conversion arises from both the plasma gas and fragmented hydrogen from the TMAs. Deuterium tagging of the MMAs, DMAs, and hydrocarbon byproducts is consistent with TMAs decomposition via plasma initiated CH3 radical removal and explains why the predominant light stable hydrocarbon produced is methane while ethane and acetylene account for the main higher hydrocarbons.

Notes: Diamond films were grown on turbostratic carbon (TC) pregrown on Cu substrates by hot filament chemical vapor deposition. Auger electron spectroscopy, Raman spectroscopy, x-ray diffraction, infrared absorption spectroscopy, and scanning electron microscopy were used to characterize both the TC and the diamond films. It was shown that the TC films could form on Cu at low temperatures (≈650 °C) with the catalysis of Mo and that diamond crystallites rapidly formed on TC in less than 10 min at higher temperature (≈1000 °C). The sp3 bonds were found to coexist with sp2 bonds in TC. The sp3 bonds in TC provide nucleation sites for diamond crystals and improve the nucleation rate at the early stage of deposition of diamond on TC.

Notes: Abstract: The objective of these experiments was to determine whether the chronic administration of nicotine, at a dose regimen that increases the density of nicotine binding sites, alters the nicotine-induced release of [3H]dopamine ([3H]DA), [3H]norepinephrine ([3H]NE), [3H]serotonin ([3H]5-HT), or [3H]acetylcholine ([3H]ACh) from rat striatal slices. For these experiments, rats received subcutaneous injections of either saline or nicotine bitartrate [1.76 mg (3.6 µmol)/kg, dissolved in saline] twice daily for 10 days, and neurotransmitter release was measured following preloading of the tissues with [3H]DA, [3H]NE, [3H]5-HT, or [3H]choline. Chronic nicotine administration did not affect the accumulation of tritium by striatal slices, the basal release of radioactivity, or the 25 mM KCl-evoked release of neurotransmitter. Superfusion of striatal slices with 1, 10, and 100 µM nicotine increased [3H]DA release in a concentration-dependent manner, and release from slices from nicotine-injected animals was significantly (p 〈 0.05) greater than release from saline-injected controls; release from the former increased to 132, 191, and 172% of release from the controls following superfusion with 1, 10, and 100 µM nicotine, respectively. Similarly, [3H]5-HT release increased in a concentration-related manner following superfusion with nicotine, and release from slices from nicotine-injected rats was significantly (p 〈 0.05) greater than that from controls. [3H]5-HT release from slices from nicotine-injected rats evoked by superfusion with 1 and 10 µM nicotine increased to 453 and 217%, respectively, of release from slices from saline-injected animals. The nicotine-induced release of [3H]NE from striatal slices was also concentration dependent but was unaffected by chronic nicotine administration. [3H]ACh release from striatal slices could not be detected when samples were superfused with nicotine but was measurable when tissues were incubated with nicotine. The release of [3H]ACh from slices from nicotine-injected rats was significantly (p 〈 0.05) less than release from controls and decreased to 36, 83, and 77% of control values following incubation with 1, 10, or 100 µM nicotine, respectively. This decreased [3H]ACh release could not be attributed to methodological differences because slices from nicotine-injected rats incubated with nicotine exhibited an increased [3H]DA release, similar to results from superfusion studies. In addition, it is unlikely that the decreased release of [3H]ACh from striatal slices from nicotine-injected rats was secondary to increased DA release because [3H]ACh release from slices from hippocampus, which is not tonically inhibited by DA, also decreased significantly (p 〈 0.05) in response to nicotine; hippocampal slices from nicotine-injected rats incubated with 1 and 10 µM nicotine decreased to 42 and 70%, respectively, of release from slices from saline-injected animals. Results indicate that the chronic administration of nicotine increases the ability of nicotine to induce the release of [3H]DA and [3H]5-HT and decreases the ability of nicotine to evoke the release of [3H]ACh but does not alter the nicotine-induced release of [3H]NE from brain slices.

Notes: A wide area vacuum ultraviolet (VUV) lamp employs a ring-shaped cold cathode to produce an electron beam excited plasma of disk geometry. When excited by the soft vacuum electron beam, molecular hydrogen, nitrogen, and atomic helium emit strong atomic resonance radiation at 121.6, 120, and 58 nm, respectively. The VUV optical power emitted on the atomic resonance line is typically 6–10% of the total applied discharge power. The spatial uniformity of the VUV emission intensity at a discharge input power level of 30 W approaches 6% across the entire disk diameter, up to a maximum of 20 cm.

Notes: An experimental investigation of picosecond laser propagation in a submillimeter liquid-core waveguide is presented. It is observed that the pump is spectrally broadened towards its Stokes frequency upon passing through the waveguide and the spectral bandwidth is further extended by stimulated raman scattering. This stable ultrafast broadband radiation is shown to be enhanced due to the use of the waveguide.

Notes: The first high-resolution study of emission spectra from ZnSe-based blue-green laser diodes is reported.

Notes: Epitaxial layers of GaN on sapphire substrates have been grown by metalorganic chemical-vapor deposition at a deposition temperature as low as 400 °C, which is the lowest temperature for successful epitaxial growth of GaN by any technique. This is achieved by controlling the low flow rate of the source gases and by first depositing an AlN buffer layer at 400 °C. Low-temperature photoluminescence measurements have been employed to study the optical properties of the films deposited at different temperatures. © 1994 American Institute of Physics.