Physical state of the emission-line region. Donald E. Osterbrock (Lick Observatory, University of California, Santa Cruz, California, U.S.A.). Physica Scripta (Sweden) 17, 285-292,1978.The physical properties of the ionized gas in the active nuclei of Seyfert and radio galaxies derived from their emission-line spectra, are reviewed. Mean densities and temperatures in Seyfert 2 and narrow-line radio galaxies are in the ranges < l o 3 -lo4 cm-' and 10 000" -20000" respectively, while in the narrow-line regions of Seyfert 1 and broadline radio galaxies the temperatures are similar but the densities range up to lo6 cm-'. In the broad-line regions the densities are 10' cm-' or greater. The abundances of the elements seem more or less normal. The relative strengths of the lines approximately match photoionization models with a power-law input spectrum, including the presence of high-ionization with lines such as [ F e X ] and [ F e X I ] along with great strength of neutral and low-ionization lines such as [0 I ] , [ N I ] and [S 111. The Fe I1 emission which occurs in most Seyfert 1 galaxies but is much weaker or absent in broad-line radio galaxies occurs in the broad-line highdensity region. Its excitation has been attributed to resonance fluorescence; this mechanism is at present being studied in detail observationally. The internal velocities observed in active nuclei are largely due to mass motions. The masses of ionized gas in the dense highvelocity regions are relatively small, and the structure of the gas must be highly filamentary or inhomogeneous. Dust is an important constituent of the active nuclei.
49.50.
A 64K-bit dynamic MOS-RAM organized as 16K words × 4 bits has been realized by short channel, channel doping and single-level Si-gate technologies. This 64K-bit dynamic RAM has been fabricated successfully through only four photolithography processing steps. The RAM has been designed by using 2 µm design rules. For the short channel transistor, the effective channel length (Leff) is about 2 µm and the gate oxide thickness (tox) is 400Å.
As a result, the access time and the cycle time of the RAM are 110 ns and 300 ns, respectively. These values are 20 to 30 percent smaller than those of RAM's fabricated on highly impurity concentrated substrate. The power dissipation is about 150 mW at the cycle time of 400 ns and 15 mW at standby mode.
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