Perceptually Uniform Motion Space

Flow data is often visualized by animated particles inserted into a flow field. The velocity of a particle on the screen is typically linearly scaled by the velocities in the data. However, the perception of velocity magnitude in animated particles is not necessarily linear. We present a study on how different parameters affect relative motion perception. We have investigated the impact of four parameters. The parameters consist of speed multiplier, direction, contrast type and the global velocity scale. In addition, we investigated if multiple motion cues, and point distribution, affect the speed estimation. Several studies were executed to investigate the impact of each parameter. In the initial results, we noticed trends in scale and multiplier. Using the trends for the significant parameters, we designed a compensation model, which adjusts the particle speed to compensate for the effect of the parameters. We then performed a second study to investigate the performance of the compensation model. From the second study we detected a constant estimation error, which we adjusted for in the last study. In addition, we connect our work to established theories in psychophysics by comparing our model to a model based on Stevens’ Power Law

Random laser from engineered nanostructures obtained by surface tension driven lithography

The random laser emission from the functionalized thienyl-S,S-dioxide quinquethiophene (T5OCx) in confined patterns with different shapes is demonstrated. Functional patterning of the light emitter organic material in well defined features is obtained by spontaneous molecular self-assembly guided by surface tension driven (STD) lithography. Such controlled supramolecular nano-aggregates act as scattering centers allowing the fabrication of one-component organic lasers with no external resonator and with desired shape and efficiency. Atomic force microscopy shows that different geometric pattern with different supramolecular organization obtained by the lithographic process tailors the coherent emission properties by controlling the distribution and the size of the random scatterers

Experimental evidence of replica symmetry breaking in random lasers

Spin-glass theory is one of the leading paradigms of complex physics and describes condensed matter, neural networks and biological systems, ultracold atoms, random photonics, and many other research fields. According to this theory, identical systems under identical conditions may reach different states and provide different values for observable quantities. This effect is known as Replica Symmetry Breaking and is revealed by the shape of the probability distribution function of an order parameter named the Parisi overlap. However, a direct experimental evidence in any field of research is still missing. Here we investigate pulse-to-pulse fluctuations in random lasers, we introduce and measure the analogue of the Parisi overlap in independent experimental realizations of the same disordered sample, and we find that the distribution function yields evidence of a transition to a glassy light phase compatible with a replica symmetry breaking.Comment: 10 pages, 5 figure

A perceptual-statistics shading model

The process of surface perception is complex and based on several influencing factors, e.g., shading, silhouettes, occluding contours, and top down cognition. The accuracy of surface perception can be measured and the influencing factors can be modified in order to decrease the error in perception. This paper presents a novel concept of how a perceptual evaluation of a visualization technique can contribute to its redesign with the aim of improving the match between the distal and the proximal stimulus. During analysis of data from previous perceptual studies, we observed that the slant of 3D surfaces visualized on 2D screens is systematically underestimated. The visible trends in the error allowed us to create a statistical model of the perceived surface slant. Based on this statistical model we obtained from user experiments, we derived a new shading model that uses adjusted surface normals and aims to reduce the error in slant perception. The result is a shape-enhancement of visualization which is driven by an experimentally-founded statistical model. To assess the efficiency of the statistical shading model, we repeated the evaluation experiment and confirmed that the error in perception was decreased. Results of both user experiments are publicly-available datasets

Dismenorrea in donne lavoratrici dell'industria

La dismenorrea è una delle più comuni indisposizioni nelle donne. La frequenza varia in differenti lavori, probabilmente ciò è dovuto alla differenza nei gruppi di popolazione studiati. In alcune industrie Norvegesi, con molto personale femminile, l’inabilità periodica al lavoro dovuto ai fastidi mestruali è stato un problema di una certa importanza e la domanda è sorta nel caso in cui l’assenza è medicalmente giustificata nella visione di un moderno trattamento ormonale. Per avvicinarci al problema abbiamo pianificato di esaminare l’evento dei fastidi mestruali, particolarmente la dismenorrea, tra il personale femminile in alcune industrie Italiane in quello che appariva essere un problema. I soggetti esaminati erano impiegati di una compagnia elettrica-tecnica e di una industria tessile. Un questionario preparato da una infermiera dell’industria, è stato compilato da donne in età mestruale che erano state visitate per esami medici periodici e di pre-assunzione tra il 2002-2003. Ogni donna assistita soffriva di dolore, e quando tutti i sintomi erano considerati il 61% aveva mensilmente disturbi che ovviamente riducevano la loro capacità sul lavoro. Visto che il 9% delle donne assumevano estroprogestinici, che riducevano o eliminavano la dismenorrea, la vera prevalenza potrebbe essere leggermente superiore. Circa il 30% delle donne erano confinate a letto. Circa il 30% si assentava dal lavoro, il che illustra la grandezza del problema sia medico che economico

Tracing the evolution in the iron content of the ICM

We present a Chandra analysis of the X-ray spectra of 56 clusters of galaxies at z>0.3, which cover a temperature range of 3>kT>15 keV. Our analysis is aimed at measuring the iron abundance in the ICM out to the highest redshift probed to date. We find that the emission-weighted iron abundance measured within (0.15-0.3)R_vir in clusters below 5 keV is, on average, a factor of ~2 higher than in hotter clusters, following Z(T)~0.88T^-(0.47)Z_o, which confirms the trend seen in local samples. We made use of combined spectral analysis performed over five redshift bins at 0.3>z>1.3 to estimate the average emission weighted iron abundance. We find a constant average iron abundance Z_Fe~0.25Z_o as a function of redshift, but only for clusters at z>0.5. The emission-weighted iron abundance is significantly higher (Z_Fe~0.4Z_o) in the redshift range z~0.3-0.5, approaching the value measured locally in the inner 0.15R_vir radii for a mix of cool-core and non cool-core clusters in the redshift range 0.1<z<0.3. The decrease in Z_Fe with redshift can be parametrized by a power law of the form ~(1+z)^(-1.25). The observed evolution implies that the average iron content of the ICM at the present epoch is a factor of ~2 larger than at z=1.2. We confirm that the ICM is already significantly enriched (Z_Fe~0.25Z_o) at a look-back time of 9 Gyr. Our data provide significant constraints on the time scales and physical processes that drive the chemical enrichment of the ICM.Comment: 6 pages, 6 figures, to appear in the Proceedings of "Heating vs. Cooling in Galaxies and Clusters of Galaxies", August 2006, Garching (Germany

Generalized Entanglement as a Natural Framework for Exploring Quantum Chaos

We demonstrate that generalized entanglement [Barnum {\em et al.}, Phys. Rev. A {\bf 68}, 032308 (2003)] provides a natural and reliable indicator of quantum chaotic behavior. Since generalized entanglement depends directly on a choice of preferred observables, exploring how generalized entanglement increases under dynamical evolution is possible without invoking an auxiliary coupled system or decomposing the system into arbitrary subsystems. We find that, in the chaotic regime, the long-time saturation value of generalized entanglement agrees with random matrix theory predictions. For our system, we provide physical intuition into generalized entanglement within a single system by invoking the notion of extent of a state. The latter, in turn, is related to other signatures of quantum chaos.Comment: clarified and expanded version accepted by Europhys. Let

Teaching in groups in grade III.

Thesis (Ed.M.)--Boston University N.B.:Pages 28, 144 and 145 are missing from original thesis

Influence of Narrative Elements on User Behaviour in Photorealistic Social VR

Social Virtual Reality (VR) applications are becoming the next big revolution in the field of remote communication. Social VR provides the possibility for participants to explore and interact with a virtual environments and objects, feelings of a full sense of immersion, and being together. Understanding how user behaviour is influenced by the shared virtual space and its elements becomes the key to design and optimize novel immersive experiences that take into account the interaction between users and virtual objects. This paper presents a behavioural analysis of user navigation trajectories in a 6 degrees of freedom, social VR movie. We analysed 48 user trajectories from a photorealistic telepresence experiment, in which subjects experience watching a crime movie together in VR. We investigate how users are affected by salient agents (i.e., virtual characters) and by the narrative elements of the VR movie (i.e., dialogues versus interactive part). We complete our assessment by conducting a statistical analysis on the collected data. Results indicate that user behaviour is affected by different narrative and interactive elements. We present our observations, and we draw conclusions on future paths for social VR experiences

Crystal Chemistry and Magnetic Properties of Gd-Substituted Aurivillius-Type Bi5FeTi3O15 Ceramics

Aurivillius-phase ferroelectrics can be turned into multiferroic materials by incorporating magnetic ions. The four-layer Aurivillius-type system Bi5FeTi3O15 is well-known to show a strong magnetoelectric effect; however, much controversy exists on its magnetic state and the possible multiferroicity at room temperature. In this paper, we report a detailed investigation on the interconnections between crystal chemistry and magnetic properties of Bi5FeTi3O15 ceramics chemically modified by the A-site gadolinium substitution. The structural studies showed that all Bi5–xGdxFeTi3O15 (0 ≤ x ≤ 1) samples adopt the polar orthorhombic space group symmetry A21am at room temperature. The unit cell volume and the orthorhombic distortion decrease alongside the reduction of octahedral tilts by increasing the amount of Gd added. The decrease in tilting distortion of the [Ti/Fe]O6 octahedra was further evidenced by the suppression of the Raman A1[111] tilt mode at 233 cm–1. By using superconducting quantum interference and vibrating sample magnetometry, it was demonstrated that all the ceramics are paramagnetic from 5 K up to 700 K. It was thus concluded that the A-site substitution of Bi5FeTi3O15 with magnetic Gd ions brings about a slight structural relaxation of the parental orthorhombic lattice, but it is not an effective way to induce multiferroic properties in the Aurivillius compound. We suggest that the room-temperature (ferri/ferro/antiferro-) magnetism in Bi5FeTi3O15 previously reported in the literature might be due to the presence of magnetic impurities or local short-range magnetic ordering formed during material processing under different conditions