What could an ecological dynamics rationale offer Quiet Eye research? Comment on Vickers

In this commentary, we respond to suggestions in previous Quiet Eye (QE) research that future work is needed to understand how theories of ecological psychology and nonlinear dynamics might frame empirical and practical work. We raise questions on the assumptions behind an information processing explanation for programming of parameters such as duration, onsets and offsets of QE, and we concur with previous calls for more research considering how visual search behaviours, such as QE, emerge under interacting personal, task and environmental constraints. However, initial work needs to frame a more general ecological dynamics explanation for QE, capturing how a process-oriented approach is needed to address how perceived affordances and adaptive functional variability might shape emergent coordination tendencies, including QE, in individual performers

A quasi-analytical modal approach for computing Casimir interactions in periodic nanostructures

We present an almost fully analytical technique for computing Casimir interactions between periodic lamellar gratings based on a modal approach. Our method improves on previous work on Casimir modal approaches for nanostructures by using the exact form of the eigenvectors of such structures, and computing eigenvalues by solving numerically a simple transcendental equation. In some cases eigenvalues can be solved for exactly, such as the zero frequency limit of gratings modeled by a Drude permittivity. Our technique also allows us to predict analytically the behavior of the Casimir interaction in limiting cases, such as the large separation asymptotics. The method can be generalized to more complex grating structures, and may provide a deeper understanding of the geometry-composition-temperature interplay in Casimir forces between nanostructures.Comment: 16 pages, 7 figure

Decay Rate of Triaxially-Deformed Proton Emitters

The decay rate of a triaxially-deformed proton emitter is calculated in a particle-rotor model, which is based on a deformed Woods-Saxon potential and includes a deformed spin-orbit interaction. The wave function of the $I=7/2^{-}$ ground state of the deformed proton emitter $^{141}$Ho is obtained in the adiabatic limit, and a Green's function technique is used to calculate the decay rate and branching ratio to the first excited 2$^{+}$ state of the daughter nucleus. Only for values of the triaxial angle $\gamma$ $<5^{\circ}$ is good agreement obtained for both the total decay rate and the 2$^{+}$ branching ratio.Comment: 19 pages, 4 figure

Hindrance of Heavy-ion Fusion at Extreme Sub-Barrier Energies in Open-shell Colliding Systems

The excitation function for the fusion-evaporation reaction 64Ni+100Mo has been measured down to a cross-section of ~5 nb. Extensive coupled-channels calculations have been performed, which cannot reproduce the steep fall-off of the excitation function at extreme sub-barrier energies. Thus, this system exhibits a hindrance for fusion, a phenomenon that has been discovered only recently. In the S-factor representation introduced to quantify the hindrance, a maximum is observed at E_s=120.6 MeV, which corresponds to 90% of the reference energy E_s^ref, a value expected from systematics of closed-shell systems. A systematic analysis of Ni-induced fusion reactions leading to compound nuclei with mass A=100-200 is presented in order to explore a possible dependence of the fusion hindrance on nuclear structure.Comment: 10 pages, 9 figures, Submitted to Phys. Rev.

Ecological cognition : expert decision-making behaviour in sport

Expert decision-making can be directly assessed, if sport action is understood as an expression of embedded and embodied cognition. Here, we discuss evidence for this claim, starting with a critical review of research literature on the perceptual-cognitive basis for expertise. In reviewing how performance and underlying processes are conceived and captured in extant sport psychology, we evaluate arguments in favour of a key role for actions in decision-making, situated in a performance environment. Key assumptions of an ecological dynamics perspective are also presented, highlighting how behaviours emerge from the continuous interactions in the performer-environment system. Perception is of affordances; and action, as an expression of cognition, is the realization of an affordance and emerges under constraints. We also discuss the role of knowledge and consciousness in decision-making behaviour. Finally, we elaborate on the specificities of investigating and understanding decision-making in sport from this perspective. Specifically, decision-making concerns the choice of action modes when perceiving an affordance during a course of action, as well as the selection of a particular affordance, amongst many that exist in a landscape in a sport performance environment. We conclude by pointing to some applications for the practice of sport psychology and coaching and identifying avenues for future research

Temporal and Spatial Occlusion of Advanced Visual Information Constrains Movement (Re) organization in One-Handed Catching Behaviors

Dynamic interceptive actions are performed under severe spatial and temporal constraints. Here, behavioral processes underpinning anticipation in one-handed catching were examined using novel technology to implement a spatial and temporal occlusion design. Video footage of an actor throwing a ball was manipulated to create four temporal and five spatial occlusion conditions. Data from twelve participants’ hand kinematics and gaze behaviors were recorded while attempting to catch a projected ball synchronized with the video footage. Catching performance decreased with earlier occlusion of the footage. Movement onset of the catching hand and initiation of visual ball tracking emerged earlier when footage of the thrower was occluded at a later time point in the throwing action. Spatial occlusion did not affect catching success, although movement onset emerged later when increased visual information of the actor was occluded. Later movement onset was countered by greater maximum velocity of the catching hand. Final stages of action (e.g., grasping action of the hand) remained unchanged across both spatial and temporal conditions suggesting that later phases of the action were organized using ball flight information. Findings highlighted the importance of maintaining information-movement coupling during performance of interceptive actions, since movement behaviors were continuously (re)organized using kinematic information from a thrower's actions and ball flight information. Keywords: Perception-action coupling; Informational constraints; Interceptive timing; Gaze; Adaptive behaviors; Anticipation

How players exploit variability and regularity of game actions in female volleyball teams

Variability analysis has been used to understand how competitive constraints shape different behaviours in team sports. In this study, we analysed and compared variability of tactical performance indices in players within complex I at two different competitive levels in volleyball. We also examined whether variability was influenced by set type and period. Eight matches from the 2012 Olympics competition and from the Portuguese national league in the 2014–2015 season were analysed (1496 rallies). Variability of setting conditions, attack zone, attack tempo and block opposition was assessed using Shannon entropy measures. Magnitude-based inferences were used to analyse the practical significance of compared values of selected variables. Results showed differences between elite and national teams for all variables, which were co-adapted to the competitive constraints of set type and set periods. Elite teams exploited system stability in setting conditions and block opposition, but greater unpredictability in zone and tempo of attack. These findings suggest that uncertainty in attacking actions was a key factor that could only be achieved with greater performance stability in other game actions. Data suggested how coaches could help setters develop the capacity to play at faster tempos, diversifying attack zones, especially at critical moments in competition

Sports teams as complex adaptive systems: manipulating player numbers shapes behaviours during football small-sided games

Small-sided and conditioned games (SSCGs) in sport have been modelled as complex adaptive systems. Research has shown that the relative space per player (RSP) formulated in SSCGs can impact on emergent tactical behaviours. In this study we adopted a systems orientation to analyse how different RSP values, obtained through manipulations of player numbers, influenced four measures of interpersonal coordination observed during performance in SSCGs. For this purpose we calculated positional data (GPS 15 Hz) from ten U-15 football players performing in three SSCGs varying in player numbers (3v3, 4v4 and 5v5). Key measures of SSCG system behaviours included values of (1) players’ dispersion, (2) teams’ separateness, (3) coupling strength and time delays between participants’ emerging movements, respectively. Results showed that values of participants’ dispersion increased, but the teams’ separateness remained identical across treatments. Coupling strength and time delay also showed consistent values across SSCGs. These results exemplified how complex adaptive systems, like football teams, can harness inherent degeneracy to maintain similar team spatial–temporal relations with opponents through changes in inter-individual coordination modes (i.e., players’ dispersion). The results imply that different team behaviours might emerge at different ratios of field dimension/player numbers. Therefore, sport pedagogists should carefully evaluate the effects of changing RSP in SSCGs as a way of promoting increased or decreased pressure on players

S17(0) Determined from the Coulomb Breakup of 83 MeV/nucleon 8B

A kinematically complete measurement was made of the Coulomb dissociation of 8B nuclei on a Pb target at 83 MeV/nucleon. The cross section was measured at low relative energies in order to infer the astrophysical S factor for the 7Be(p,gamma)8B reaction. A first-order perturbation theory analysis of the reaction dynamics including E1, E2, and M1 transitions was employed to extract the E1 strength relevant to neutrino-producing reactions in the solar interior. By fitting the measured cross section from Erel = 130 keV to 400 keV, we find S17(0) = 17.8 (+1.4, -1.2) eV b