Catching what we can't see: manual interception of occluded fly-ball trajectories

Control of interceptive actions may involve fine interplay between feedback-based and predictive mechanisms. These processes rely heavily on target motion information available when the target is visible. However, short-term visual memory signals as well as implicit knowledge about the environment may also contribute to elaborate a predictive representation of the target trajectory, especially when visual feedback is partially unavailable because other objects occlude the visual target. To determine how different processes and information sources are integrated in the control of the interceptive action, we manipulated a computer-generated visual environment representing a baseball game. Twenty-four subjects intercepted fly-ball trajectories by moving a mouse cursor and by indicating the interception with a button press. In two separate sessions, fly-ball trajectories were either fully visible or occluded for 750, 1000 or 1250 ms before ball landing. Natural ball motion was perturbed during the descending trajectory with effects of either weightlessness (0 g) or increased gravity (2 g) at times such that, for occluded trajectories, 500 ms of perturbed motion were visible before ball disappearance. To examine the contribution of previous visual experience with the perturbed trajectories to the interception of invisible targets, the order of visible and occluded sessions was permuted among subjects. Under these experimental conditions, we showed that, with fully visible targets, subjects combined servo-control and predictive strategies. Instead, when intercepting occluded targets, subjects relied mostly on predictive mechanisms based, however, on different type of information depending on previous visual experience. In fact, subjects without prior experience of the perturbed trajectories showed interceptive errors consistent with predictive estimates of the ball trajectory based on a-priori knowledge of gravity. Conversely, the interceptive responses of subjects previously exposed to fully visible trajectories were compatible with the fact that implicit knowledge of the perturbed motion was also taken into account for the extrapolation of occluded trajectories

Real-time monitoring of the impact of cascaded wavelength-selective switches in digital coherent receivers

A simple real-time monitoring algorithm for the impact of cascaded WSSs in elastic optical networks, which exploits the information available in a digital coherent receiver, is proposed and demonstrated through both numerical simulations and experiments

Interception of vertically approaching objects: temporal recruitment of the internal model of gravity and contribution of optical information

introduction: recent views posit that precise control of the interceptive timing can be achieved by combining on-line processing of visual information with predictions based on prior experience. Indeed, for interception of free-falling objects under gravity's effects, experimental evidence shows that time-to-contact predictions can be derived from an internal gravity representation in the vestibular cortex. however, whether the internal gravity model is fully engaged at the target motion outset or reinforced by visual motion processing at later stages of motion is not yet clear. moreover, there is no conclusive evidence about the relative contribution of internalized gravity and optical information in determining the time-to-contact estimates.methods: we sought to gain insight on this issue by asking 32 participants to intercept free falling objects approaching directly from above in virtual reality. object motion had durations comprised between 800 and 1100 ms and it could be either congruent with gravity (1 g accelerated motion) or not (constant velocity or -1 g decelerated motion). we analyzed accuracy and precision of the interceptive responses, and fitted them to bayesian regression models, which included predictors related to the recruitment of a priori gravity information at different times during the target motion, as well as based on available optical information.results: consistent with the use of internalized gravity information, interception accuracy and precision were significantly higher with 1 g motion. moreover, bayesian regression indicated that interceptive responses were predicted very closely by assuming engagement of the gravity prior 450 ms after the motion onset, and that adding a predictor related to on-line processing of optical information improved only slightly the model predictive power. discussion: thus, engagement of a priori gravity information depended critically on the processing of the first 450 ms of visual motion information, exerting a predominant influence on the interceptive timing, compared to continuously available optical information. finally, these results may support a parallel processing scheme for the control of interceptive timing

Rhythmic tapping to a moving beat motion kinematics overrules natural gravity

beat induction is the cognitive ability that allows humans to listen to a regular pulse in music and move in synchrony with it. although auditory rhythmic cues induce more consistent synchronization than flashing visual metronomes, this auditory-visual asymmetry can be canceled by visual moving stimuli. here, we investigated whether the naturalness of visual motion or its kinematics could provide a synchronization advantage over flashing metronomes. Subjects were asked to tap in sync with visual metronomes defined by vertically accelerating/decelerating motion, either congruent or not with natural gravity; horizontally accelerating/decelerating motion; or flashing stimuli. we found that motion kinematics was the predominant factor determining rhythm synchronization, as accelerating moving metronomes in any cardinal direction produced more precise and predictive tapping than decelerating or flashing conditions. our results support the notion that accelerating visual metronomes convey a strong sense of beat, as seen in the cueing movements of an orchestra director

What a difference a workplace makes. A scientometric analysis on the relationship between job crafting and healthy organizations' factors

Introduction: The transformations that have affected the labour market in recent years have required companies to adapt to fast changes and to keep the pace of global competition. Consequently, workers have been confronted with multiple challenging demands: they have been required to develop flexibility in their jobs and to work faster and better, often with evident costs in terms of performance and their workplace well-being. Given these evidence, as also shown by some of the most recent developments in the field of Positive Work and Organizational Psychology, healthy organizations are those organizations that could resist to these challenges, because they engage in creating an environment that can promote employees’ health and safety, maximising performance. Yet, healthy organizations support positive organizational behaviors through a coherent culture, a positive climate, and good practices. Healthy organizations might also create the conditions to encourage workers to perform job crafting behaviors, meant as proactive individual behaviours aimed at modifying job demands in order to adjust them to personal needs, motivations and talents, thus maximising well-being and performance. Objective: The aim of the study was to overview the state of the art of the debate about the relationship between job crafting and healthy organizations’ factors by performing a scientometric analysis of job crafting. Therefore, the study was aimed to emphasize performances of countries, journals and authors, highlighting the dominant perspectives on the topic. Method: The starting point of the analysis was data recovery from the Scopus database using the term “job crafting” as search criterion within the title, abstract or keywords of the documents retrieved. The analysis was carried out with two softwares, R and VOSviewer, in order to investigate the growth of interest on the topic over the years, the scientific production of countries, journals and authors, the social structure of collaborative network, and the network of keywords. Results: 375 documents about job crafting were retrieved, showing a growing number of publications in recent years, with a preponderance of productions and citations in USA and Netherlands (where the construct was proposed and validated). Cluster analysis performed on the most frequently used keywords showed three main groups, each of them theoretical linked to workplace health: stimulus factors; Job Demands-Resources Model; health dimensions. Discussion: The present bibliometric analysis showed an increasing scientific interest toward job crafting and the importance of specific papers (that opened the two main perspective about it) for the whole research line. Through the cluster analysis of keywords network, it was underlined the relevance of constructs that promote healthy organizations in the scientific production on job craftin

Realization of the farad from the dc quantum Hall effect with digitally-assisted impedance bridges

A new traceability chain for the derivation of the farad from dc quantum Hall effect has been implemented at INRIM. Main components of the chain are two new coaxial transformer bridges: a resistance ratio bridge, and a quadrature bridge, both operating at 1541 Hz. The bridges are energized and controlled with a polyphase direct-digital-synthesizer, which permits to achieve both main and auxiliary equilibria in an automated way; the bridges and do not include any variable inductive divider or variable impedance box. The relative uncertainty in the realization of the farad, at the level of 1000 pF, is estimated to be 64E-9. A first verification of the realization is given by a comparison with the maintained national capacitance standard, where an agreement between measurements within their relative combined uncertainty of 420E-9 is obtained.Comment: 15 pages, 11 figures, 3 table

A Simple and Effective Closed-Form GN-Model Correction Formula Accounting for Signal Non-Gaussian Distribution

The GN model of non-linear fiber propagation has been shown to overestimate the variance of non-linearity due to the signal Gaussianity approximation, leading to maximum reach predictions for realistic optical systems which may be pessimistic by about 5% to 15%, depending on fiber type and system set-up. Analytical corrections have been proposed, which however substantially increase the model complexity. In this paper we provide a simple closed-form GN model correction formula, derived from the EGN model, which we show to be quite effective in correcting for the GN model tendency to overestimate non-linearity. The formula also permits to clearly identify the correction dependence on key system parameters, such as span length and loss.Comment: This paper has been accepted for publication in the IEEE Journal of Lightwave Technolog

Performance evaluation of coherent WDM PS-QPSK (HEXA) accounting for non-linear fiber propagation effects

Coherent-detection (CoD) permits to fully exploit the fourdimensional (4D) signal space consisting of the in-phase and quadrature components of the two fiber polarizations. A well-known and successful format exploiting such 4D space is Polarization-multiplexed QPSK (PM-QPSK). Recently, new signal constellations specifically designed and optimized in 4D space have been proposed, among which polarizationswitched QPSK (PS-QPSK), consisting of a 8-point constellation at the vertices of a 4D polychoron called hexadecachoron. We call it HEXA because of its geometrical features and to avoid acronym mix-up with PM-QPSK, as well as with other similar acronyms. In this paper we investigate the performance of HEXA in direct comparison with PM-QPSK, addressing non-linear propagation over realistic links made up of 20 spans of either standard single mode fiber (SSMF) or non-zero dispersion-shifted fiber (NZDSF). We show that HEXA not only confirms its theoretical sensitivity advantage over PM-QPSK in back-to-back, but also shows a greater resilience to non-linear effects, allowing for substantially increased span loss margins. As a consequence, HEXA appears as an interesting option for dual-format transceivers capable to switch on-the-fly between PM-QPSK and HEXA when channel propagation degrades. It also appears as a possible direct competitor of PM-QPSK, especially over NZDSF fiber and uncompensated links