Removal of monocular interactions equates rivalry behavior for monocular, binocular, and stimulus rivalries

When the two eyes are presented with conflicting stimuli, perception starts to fluctuate over time (i.e., binocular rivalry). A similar fluctuation occurs when two patterns are presented to a single eye (i.e., monocular rivalry), or when they are swapped rapidly and repeatedly between the eyes (i.e., stimulus rivalry). Although all these cases lead to rivalry, in quantitative terms these modes of rivalry are generally found to differ significantly. We studied these different modes of rivalry with identical intermittently shown stimuli while varying the temporal layout of stimulation. We show that the quantitative differences between the modes of rivalry are caused by the presence of monocular interactions between the rivaling patterns; the introduction of a blank period just before a stimulus swap changed the number of rivalry reports to the extent that monocular and stimulus rivalries were inducible over ranges of spatial frequency content and contrast values that were nearly identical to binocular rivalry. Moreover when monocular interactions did not occur the perceptual dynamics of monocular, binocular, and stimulus rivalries were statistically indistinguishable. This range of identical behavior exhibited a monocular (∼50 ms) and a binocular (∼350 ms) limit. We argue that a common binocular, or pattern-based, mechanism determines the temporal constraints for these modes of rivalry

Spectral Analysis of Correlated One-Dimensional Systems with Impurities

An averaging procedure is proposed to account for spectral features of correlated one-dimensional systems in the presence of non-magnetic impurities. The dynamical spin structure factor for a corresponding random ensemble of Heisenberg chain segments is calculated by exact numerical diagonalization. It is shown that a few-pole approximation is sufficient to describe the numerical results. A similar analysis is proposed for the discussion of experimental spectra, such as obtained by inelastic neutron scattering measurements on Zn-doped CuO chains. By examination of the disorder-induced pseudo-gap, the loss of spectral weight, and the discrete peak structures due to smallest-cluster contributions, the underlying impurity distribution function can be determined.Comment: RevTex, 4 pages with 4 eps figure

Flash suppression and flash facilitation in binocular rivalry

We show that previewing one half image of a binocular rivalry pair can cause it to gain initial dominance when the other half is added, a novel phenomenon we term flash facilitation. This is the converse of a known effect called flash suppression, where the previewed image becomes suppressed upon rivalrous presentation. The exact effect of previewing an image depends on both the duration and the contrast of the prior stimulus. Brief, low-contrast prior stimuli facilitate, whereas long, high-contrast ones suppress. These effects have both an eye-based component and a pattern-based component. Our results suggest that, instead of reflecting two unrelated mechanisms, both facilitation and suppression are manifestations of a single process that occurs progressively during presentation of the prior stimulus. The distinction between the two phenomena would then lie in the extent to which the process has developed during prior stimulation. This view is consistent with a neural model previously proposed to account for perceptual stabilization of ambiguous stimuli, suggesting a relation between perceptual stabilization and the present phenomena

A Dissociation of Attention and Awareness in Phase-sensitive but Not Phase-insensitive Visual Channels

The elements most vivid in our conscious awareness are the ones to which we direct our attention. Scientific study confirms the impression of a close bond between selective attention and visual awareness, yet the nature of this association remains elusive. Using visual afterimages as an index, we investigate neural processing of stimuli as they enter awareness and as they become the object of attention. We find evidence of response enhancement accompanying both attention and awareness, both in the phase-sensitive neural channels characteristic of early processing stages and in the phase-insensitive channels typical of higher cortical areas. The effects of attention and awareness on phase-insensitive responses are positively correlated, but in the same experiments, we observe no correlation between the effects on phase-sensitive responses. This indicates independent signatures of attention and awareness in early visual areas yet a convergence of their effects at more advanced processing stages

When Better Seems Bigger: Perceived Performance of Adult Professional Football Players Is Positively Associated With Perceptions of Their Body Size

Research has shown a positive association between cues of physical formidability and perceptions of status, supporting a generic “bigger-is-better” heuristic. However, does better also lead to appraisals as bigger? Recent research suggests that the perceptual association between body size and social status can also be explained in terms of prestige. To test whether perceptions of prestige lead to higher appraisals of body size, we examined whether people apply a “better is bigger bias” (BBB) in football, where performance and body size tend to be uncorrelated. In two studies, we examined real coalitional sports groups on a national (Study 1) and team level (Study 2), and we manipulated target performance in an experimental third study. Results suggest that perceived performance significantly predicted both the perceived height (Studies 2 and 3) and perceived weight (Studies 1 and 2) of professional football players, supporting the BBB. Support for the team had a positive effect on body size estimations of the players; however, we did not find any support for winner or loser effects. We discuss these results in light of individual versus team performance and coalitional affiliation

A novel bead-based assay to detect specific antibody responses against Toxoplasma gondii and Trichinella spiralis simultaneously in sera of experimentally infected swine

<p>Abstract</p> <p>Background</p> <p>A novel, bead-based flow cytometric assay was developed for simultaneous determination of antibody responses against <it>Toxoplasma gondii </it>and <it>Trichinella spiralis </it>in pig serum. This high throughput screening assay could be an alternative for well known indirect tests like ELISA. One of the advantages of a bead-based assay over ELISA is the possibility to determine multiple specific antibody responses per single sample run facilitated by a series of antigens coupled to identifiable bead-levels. Furthermore, inclusion of a non-coupled bead-level in the same run facilitates the determination of, and correction for non-specific binding. The performance of this bead-based assay was compared to one <it>T. spiralis </it>and three <it>T. gondii </it>ELISAs. For this purpose, sera from <it>T. gondii </it>and <it>T. spiralis </it>experimentally infected pigs were used. With the experimental infection status as gold standard, the area under the curve, Youden Index, sensitivity and specificity were determined through receiver operator curve analysis. Marginal homogeneity and inter-rater agreement between bead-based assay and ELISAs were evaluated using McNemar's Test and Cohen's kappa, respectively.</p> <p>Results</p> <p>Results indicated that the areas under the curve of the bead-based assay were 0.911 and 0.885 for <it>T. gondii </it>and <it>T. spiralis</it>, respectively, while that of the <it>T. gondii </it>ELISAs ranged between 0.837 and 0.930 and the <it>T. spiralis </it>ELISA was 0.879. Bead-based <it>T. gondii </it>assay had a sensitivity of 86% and specificity of 96%, while the ELISAs ranged between 64-84% and 93-99%, respectively. The bead-based <it>T. spiralis </it>assay had a sensitivity of 68% and specificity of 100% while the ELISA scored 72% and 95%, respectively. Marginal homogeneity was found between the <it>T. gondii </it>bead-based test and one of the <it>T. gondii </it>ELISAs. Moreover, in this test combination and between <it>T. spiralis </it>bead-based assay and respective ELISA, an excellent inter-rater agreement was found. When results of samples before expected seroconversion were removed from evaluation, notably higher test specifications were found.</p> <p>Conclusions</p> <p>This new bead-based test, which detects <it>T. gondii </it>and <it>T. spiralis </it>antibodies simultaneously within each sample, can replace two indirect tests for the determination of respective antibodies separately, while performing equally well or better.</p

Aftershocks

Aftershocks was written in the midst of the deepest economic crisis since the Great Depression. Although it would be premature to presume to identify the repercussions of the crisis, it is clear that it will have profound aftershock effects in the political, economic, and social spheres. The book contains essays based on semi-structured interviews with leading scholars, European politicians and representatives from the world of business. They reflect on the origins of the crisis as well as the possible social, economic, and political transformations it may engender

Risk of Infection with Leishmania spp. in the Canine Population in the Netherlands

<p/> <p>The dog is the main reservoir of <it>Leishmania infantum</it>, the causative agent of visceral leishmaniasis (VL) in humans in Southern Europe. In order to identify the risk of dogs from a <it>Leishmania </it>non-endemic area traveling to a <it>Leishmania</it>-endemic area becoming infected and the risk of transmitting infection to humans in non-endemic areas an investigation was performed, in which the results of a questionnaire were combined with the results of a serologic survey.</p> <p>The questionnaire was sent to 1478 at random chosen families in the Netherlands. Of the 59.0% responders 28.0% had one or more dogs and 4.8% of these dogs had visited Southern Europe during the summer period of that year. On a total population of 1,200,000 dogs in the Netherlands, this means that each year some 58,000 dogs are at risk of being exposed to a <it>Leishmania </it>infection in Southern Europe.</p> <p>During the period 1990–1992 blood was collected for serology in 1911 dogs presented to the Utrecht University Clinic because of clinical problems not related to leishmaniasis, of which 434 had been in Southern Europe in the foregoing years. None was serologically positive. From these data it can be deduced that the highest chance to obtain leishmaniasis during a vacation in Southern Europe is mathematically less than 1/434 or less than 0.23%. Serology was also performed during the period 1989–1993 in 597 dogs that had been in Southern Europe and were suspected of leishmaniasis. Titers were positive in 145 of these samples. Sixty-four of these dogs were born in the Mediterranean and had been imported into the Netherlands. Excluding these imported dogs, it was calculated that at least 0.027% of the 58,000 dogs yearly taken to Southern Europe during holidays become infected with Leishmania. In order to establish the risk of disease transmission for people in close contact with an infected dog, serum samples of owners and house mates of 37 dogs with leishmaniasis were tested. All 112 sera tested negative. It was concluded that the risk to get leishmaniasis was between 0.027% and 0.23% for the dog when taken to Southern Europe during vacation, and that the risk for owners in non-endemic areas to get leishmaniasis from an infected dog is minimal.</p

Two dimensional bulge disk decomposition

We propose a two dimensional galaxy fitting algorithm to extract parameters of the bulge, disk, and a central point source from broad band images of galaxies. We use a set of realistic galaxy parameters to construct a large number of model galaxy images which we then use as input to our galaxy fitting program to test it. We find that our approach recovers all structural parameters to a fair degree of accuracy. We elucidate our procedures by extracting parameters for 3 real galaxies -- NGC 661, NGC 1381, and NGC 1427.Comment: 23 pages, LaTeX, AASTEX macros used, 7 Postscript figures, submitted to Ap