Active region, hidden

If one part of a metallic object is protected from the atmosphere so that there is insufficient O2 to build or maintain the oxide film, this protected region will often be the site at which corrosion is most active. The fact that such sites are usually hidden from view accounts for much of the difficulty in detecting and controlling corrosion. 

The "Hidden Site" Concept in Faujasite. The infrared active hydroxyl vibrations in H-faujasite absorb at two distinct frequency regions, commonly denoted as high-frequency (HF) and low-frequency (LF) hydroxyl bands (17.). In the structure of faujasite, there are four crystallographically distinct oxygen atoms. The HF band vibrating in the 3680-3625 cm--1- range is generally... 

NGC1068 is a classic example of a hidden Seyfert 1 galaxy. As part of a programme to study the spectra of nearby dusty active galaxies we have obtrdned spectra of NGC1068 in the 3-4fon region. 

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