A First- and Second-Order Motion Energy Analysis of Peripheral Motion Illusions Leads to Further Evidence of “Feature Blur” in Peripheral Vision

Anatomical and physiological differences between the central and peripheral visual systems are well documented. Recent findings have suggested that vision in the periphery is not just a scaled version of foveal vision, but rather is relatively poor at representing spatial and temporal phase and other visual features. Shapiro, Lu, Huang, Knight, and Ennis (2010) have recently examined a motion stimulus (the “curveball illusion”) in which the shift from foveal to peripheral viewing results in a dramatic spatial/temporal discontinuity. Here, we apply a similar analysis to a range of other spatial/temporal configurations that create perceptual conflict between foveal and peripheral vision.To elucidate how the differences between foveal and peripheral vision affect super-threshold vision, we created a series of complex visual displays that contain opposing sources of motion information. The displays (referred to as the peripheral escalator illusion, peripheral acceleration and deceleration illusions, rotating reversals illusion, and disappearing squares illusion) create dramatically different perceptions when viewed foveally versus peripherally. We compute the first-order and second-order directional motion energy available in the displays using a three-dimensional Fourier analysis in the (x, y, t) space. The peripheral escalator, acceleration and deceleration illusions and rotating reversals illusion all show a similar trend: in the fovea, the first-order motion energy and second-order motion energy can be perceptually separated from each other; in the periphery, the perception seems to correspond to a combination of the multiple sources of motion information. The disappearing squares illusion shows that the ability to assemble the features of Kanisza squares becomes slower in the periphery.The results lead us to hypothesize “feature blur” in the periphery (i.e., the peripheral visual system combines features that the foveal visual system can separate). Feature blur is of general importance because humans are frequently bringing the information in the periphery to the fovea and vice versa

An Empirical Study of Extracting Multidimensional Sequential Rules for Personalization and Recommendation in Online Commerce

The application of web mining to personalization has a long tradition in electronic commerce research. In this empirical study we focus specifically on mining sequential navigation patterns from weblogs and thoroughly compare different design variants for making personalized suggestions to users. In particular we concentrate on the impact of additional product knowledge like item characteristics, different properties of the sequential pattern mining process such as closure as well as rule quality metrics such as support, confidence and lift, and evaluate the recommender’s accuracy by experimenting on historical web sessions. This paper therefore firstly demonstrates how state of the art sequence mining algorithms such as PrefixSpan and BIDE may be adapted to the specific problem of extracting sequential rules from e-commerce weblogs. Furthermore, in order to compact the resulting rule set, the ∆-closed criteria is proposed as a logical extention to closed and maximal frequent patterns to eliminate spurious sequences. Finally, our experimental findings show that using multidimensional sequential patterns and the lift metric for weighting personalization rules can boost recall to 28 % of all actual purchase transactions when using only short navigational sequences

Structural analysis of Cu(II) ligation to the 5'-GMP nucleotide by pulse EPR spectroscopy

Simple copper salts are known to denature poly d(GC). On the other hand, copper complexes of substituted 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione are able to convert the right-handed B form of the same DNA sequence to the corresponding left-handed Z form. A research program was started in order to understand why Cu(II) as an aquated ion melts DNA and induces the conformational change to Z-DNA in the form of an azamacrocyclic complex. In this paper, we present a continuous wave and pulse electron paramagnetic resonance study of the mononucleotide model system Cu(II)-guanosine 5'-monophosphate . Pulse EPR methods like electron-nuclear double resonance and hyperfine sublevel correlation spectroscopy provide unique information about the electronic and geometric structure of this model system through an elaborate mapping of the hyperfine and nuclear quadrupole interactions between the unpaired electron of the Cu(II) ion and the magnetic nuclei of the nucleotide ligand. It was found that the Cu(II) ion is directly bound to N7 of guanosine 5'-monophosphate and indirectly bound via a water of hydration to a phosphate group. This set of experiments opens the way to more detailed structural characterization of specifically bound metal ions in a variety of nucleic acids of biological interest, in particular to understand the role of the metal-(poly)nucleotide interaction