A Judd illusion in far-aiming: evidence of a contribution to action by vision for perception

The present study addresses the role of vision for perception in determining the location of a target in far-aiming. Participants (N = 12) slid a disk toward a distant target embedded in illusory Judd figures. Additionally, in a perception task, participants indicated when a moving pointer reached the midpoint of the Judd figures. The number of hits, the number of misses to the left and to the right of the target, the sliding error (in mm) and perceptual judgment error (in mm) served as dependent variables. Results showed an illusory bias in sliding, the magnitude of which was comparable to the bias in the perception of target location. The determination of target location in far-aiming is thus based on relative metrics. We argue that vision for perception sets the boundary constraints for action and that within these constraints vision for action autonomously controls movement execution, but alternative accounts are discussed as well

Surface science models for CoMo hydrodesulfurization catalysts: Influence of the support on hydrodesulfurization activity

Flat model systems of supported oxidic COMO hydrodesulfurization (HDS) catalysts, consisting of a conducting substrate with a thin SiO2 or Al2O3 layer on top of which the active catalytic phase is deposited by spin coating, were used to study the influence of the support and the use of chelating agents on the formation of the active CoMoS phase. On Co/Al2O3 catalysts Co can only be partially sulfided due to the strong interaction with Al2O3. In the mixed phase CoMo/Al2O3 system, the presence of Mo facilitates the sulfidation of Co. Due to the interaction of Mo with the support the Co-Al2O3 interaction is blocked. In these catalysts the sulfidation of Co and Mo proceed at the same rate. In the case Of CoMo/SiO2 catalysts the weak interaction with the SiO2 support results in the complete sulfidation of Co at low temperatures, while Mo sulfides at a slower rate. Thiophene HDS activity measurements showed that due to the stronger interaction, Al2O3 is a better support for CoMoS formation. By complexing COMO on Al2O3 to chelating agents, like ethylenediaminetetraacetic acid (EDTA), the sulfidation of Co is retarded while that of Mo is facilitated. Although Mo also forms complexes with EDTA, these complexes are less stable than those of Co. Hence, the sulfidation of Mo precedes that of Co. Due to the absence of interaction with the support of the same sulfidation behavior was observed for both supports. The activity tests showed that these catalysts have the highest activity, irrespective of support. (C) 2001 American Vacuum Societ