A catalog of new Blazar candidates with Open Universe by High School students

Blazars are active galactic nuclei whose ultra-relativistic jets are coaligned with the observer direction. They emit throughout the whole e.m. spectrum, from radio waves to VHE gamma rays. Not all blazars are discovered. In this work, we propose a catalog of 54 new candidates based on the association of HE gamma ray emission and radio, X-ray an optical signatures. The relevance of this work is also that it was performed by four high school students from the Liceo Scientifico Statale Ugo Morin in Venice, Italy using the open-source platform Open Universe, in collaboration with the University of Padova. The framework of the activity is the Italian MIUR PCTO programme. The success of this citizen-science experience and results are hereafter reported and discussed.Comment: Proceedings of the 12th Cosmic Ray International Symposium (CRIS 2022), 12-16 September 2022, Naples (Italy). Send correspondence to: [email protected], [email protected]

Haptic perception of shapes and line drawings

In this thesis various aspect of haptic perception were studied. The first part of the thesis is mainly concerned with haptic perception of two-dimensional shapes and line drawings. We first studied the angular acuity of two-dimensional shapes an found that the manner of exploration as well as the local and global stimulus properties influence angular acuity. Secondly we studied identification of line drawings by touch. We found that the size of the picture influences identifiability. We also found that observers seem to use a hypothesis driven strategy: on average 23% of the total exploration time was spend on confirming the final hypothesis. In the next chapter on line drawing identification we report a finding that helped to explain why identifying a line drawing by touch is such a difficult task. We found that if observers were not able to identify a picture and were given the opportunity to sketch what they had just felled, in 30% of the cases they could identify their own sketch. A line drawing is easily processed with vision, but if the input is made sequential instead of simultaneous, identification becomes very difficult. This is because the structure of the input has changed and cannot be used to match the internal representations. Similar to sequential vision, if a line drawing is explored by touch, then the structure of the percept is what could be called `one-dimensional'; that is, a sequential description. Observers experience difficulty in mentally switching between these two structures. What can be done is restructuring the representation from sequential to simultaneous by producing a sketch. This explains the recognition-after-sketching-effect. In the second part of the thesis we aspect of haptic perception of three-dimensional curvature. First we studied real, solid shapes and virtual shapes generated by a robotic interface. One of the purposes was to study the contribution of two isolated geometric cues. We found that the surface orientation is a much more dominant cue than the position. Besides measuring the discrimination thresholds, we also measured whether a virtual stimulus would feel as curved as a real stimulus. We did not find a systematic difference and even found that it did not matter whether or not zeroth order information was available when observers compared the curvedness of real and virtual stimuli. In the last chapter, we found that if a curved shape is touched with one finger, it will induce an illusory curvature on the other finger. Interestingly, this phenomenon was present for both raised lines and solid shapes. In a subsequent experiment we wanted to investigate whether the biomechanical constraints of the hand were responsible for the effect, but we did not find evidence for this hypothesis. Whereas in a previous study we found that the surface attitude is the important cue for curvature, we propose that the curvature contrast illusion is mainly caused by a shift of dominance from the attitude cue to the positional cue

Opposite Influence of Perceptual Memory on Initial and Prolonged Perception of Sensory Ambiguity

Observers continually make unconscious inferences about the state of the world based on ambiguous sensory information. This process of perceptual decision-making may be optimized by learning from experience. We investigated the influence of previous perceptual experience on the interpretation of ambiguous visual information. Observers were pre-exposed to a perceptually stabilized sequence of an ambiguous structure-from-motion stimulus by means of intermittent presentation. At the subsequent re-appearance of the same ambiguous stimulus perception was initially biased toward the previously stabilized perceptual interpretation. However, prolonged viewing revealed a bias toward the alternative perceptual interpretation. The prevalence of the alternative percept during ongoing viewing was largely due to increased durations of this percept, as there was no reliable decrease in the durations of the pre-exposed percept. Moreover, the duration of the alternative percept was modulated by the specific characteristics of the pre-exposure, whereas the durations of the pre-exposed percept were not. The increase in duration of the alternative percept was larger when the pre-exposure had lasted longer and was larger after ambiguous pre-exposure than after unambiguous pre-exposure. Using a binocular rivalry stimulus we found analogous perceptual biases, while pre-exposure did not affect eye-bias. We conclude that previously perceived interpretations dominate at the onset of ambiguous sensory information, whereas alternative interpretations dominate prolonged viewing. Thus, at first instance ambiguous information seems to be judged using familiar percepts, while re-evaluation later on allows for alternative interpretation

Perceptual incongruence influences bistability and cortical activation

We employed a parametric psychophysical design in combination with functional imaging to examine the influence of metric changes in perceptual incongruence on perceptual alternation rates and cortical responses. Subjects viewed a bistable stimulus defined by incongruent depth cues; bistability resulted from incongruence between binocular disparity and monocular perspective cues that specify different slants (slant rivalry). Psychophysical results revealed that perceptual alternation rates were positively correlated with the degree of perceived incongruence. Functional imaging revealed systematic increases in activity that paralleled the psychophysical results within anterior intraparietal sulcus, prior to the onset of perceptual alternations. We suggest that this cortical activity predicts the frequency of subsequent alternations, implying a putative causal role for these areas in initiating bistable perception. In contrast, areas implicated in form and depth processing (LOC and V3A) were sensitive to the degree of slant, but failed to show increases in activity when these cues were in conflic

Wide distribution of external local sign in the normal population

The extent of the apparent visual Weld was determined for a group of 78 naïve visual observers. We Wnd that there exists a minority (less than 10%) that is essentially veridical, but that the majority of the population experiences an apparent visual Weld of only about 90°, thus much narrower than the dioptrics of the eye would suggest (a little over 180°). This is in good accordance with available (albeit mainly anecdotal) evidence, though formal data have been lacking thus far. The Wnding is discussed in the context of metrical calibration of the topological structure of the visual Weld, an aspect of “local sign