Coadsorption of nitric oxide and oxygen on the Ag(110) surface

The coadsorption of NO and O-2 on Ag(110) surface has been studied by X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and in situ Raman spectroscopy. The existence of oxygen enhances the adsorption of NO by forming the NOx species, that is, NO2 and NO3, and the NO in turn as a promotor facilitates the cleavage of the dioxygen bond, forming the surface atomic oxygen species having the same spectral characteristics as those produced using oxygen at high pressure. The oxygen species generated by the interaction is composed of two parts. One is produced directly by the decomposition of surface NO-O-2 complex at ca 625 K, which raised an O 1s feature at 530.5 eV and is absent at ca 800 K, while the another with an O 1s binding energy of 529.2 eV emerges at higher temperatures and shows similar properties as the reported gamma-state oxygen which bound tightly on restructured silver surface. The exposure to NO and O-2 causes noticeable changes in the morphology of the Ag(110) surface and the flat terraces superseded by small (ca 0.1 mu m) pits, and particles with typical diameters of a few micrometres were formed at elevated temperatures. (C) 1999 Elsevier Science B.V. All rights reserved.

Effects Of Preservation On Wet Weight Dry-Weight Nitrogen And Carbon Contents Of Calanus-Helgolandicus (Crustacea Copepoda)

The lengths, wet and dry weights, nitrogen and carbon contents of fresh, frozen and formaldehyde-fixed specimens of Calanus helgolandicus (Claus) were determined. Samples were collected during May 1980 in the Celtic Sea. Individual Copepodite Stages 3, 4, 5, and Adult Male and Female Stage 6 were measured and analysed, and 36 linear regression equations derived for these variables together with mean values, standard deviations and 95% confidence limits. The range of nitrogen values in the fresh material, expressed as a percentage of dry weight, ranged from 8.08%±0.80 (Copepodite Stage 3) to 10.89%±0.27 (adult female); carbon values changed from 41.6%±3.05 (mean ±95% confidence limits) for Copepodite Stage 3 to 50.97%±2.63 in Copepodite Stage 5. The adult females had a high nitrogen and relatively low carbon content, while the converse was true for Stage 5 copepodites. There was a loss of dry weight from the frozen samples (57%) and the fixed samples (38%) compared with the mean of the fresh dry weight of all stages. The material lost from the copepods was rich in nitrogen, thus, artificially high percentage carbon values were determined from the frozen and fixed samples (52.0 to 60.3% and 44.7 to 58.5%, respectively).