[1] We investigate the longitudinal distribution of the vertical E Â B drift velocity and ion density in the lowlatitude ionosphere using the first Republic of China Satellite (ROCSAT-1) data acquired during 1999 -2004. The ROCSAT-1 observations during daytime demonstrate the presence of the longitudinally periodic patterns of the vertical E Â B drift and plasma density on the topside F region (600 km). The four longitude sectors where the peaks in the plasma density are found are coincident with the peaks in the E Â B drift. This observation may indicate the association of the large-scale longitudinal density structure with the daytime E-region dynamo electric field. The density structure exists before the occurrence of the pre-reversal enhancement (PRE) and therefore the PRE is not directly related to this phenomenon. Citation:

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Selectivity in chemical reactions is a major objective in industrial processes to minimize spurious byproducts and to save scarce resources. In homogeneous catalysis the most important factor which determines selectivity is structural symmetry. However, a transfer of the symmetry concept to heterogeneous catalysis still requires a detailed comprehension of the underlying processes. Here, we investigate a ring-closing reaction in surface-confined meso-substituted porphyrin molecules by scanning tunneling microscopy, temperature-programmed desorption, and computational modeling. The identification of reaction intermediates enables us to analyze the reaction pathway and to conclude that the symmetry of the porphyrin core is of pivotal importance regarding product yields.