Transition from an anti-phase error-correction-mode to a synchronization mode in the mutual hand tracking

Proactive motion in hand tracking and in finger bending, in which the body motion occurs prior to the reference signal, was reported by the preceding researchers when the target signals were shown to the subjects at relatively high speed or high frequencies. These phenomena indicate that the human sensory-motor system tends to choose an anticipatory mode rather than a reactive mode, when the target motion is relatively fast. The present research was undertaken to study what kind of mode appears in the sensory-motor system when two persons were asked to track the hand position of the partner with each other at various mean tracking frequency. The experimental results showed a transition from a mutual error-correction mode to a synchronization mode occurred in the same region of the tracking frequency with that of the transition from a reactive error-correction mode to a proactive anticipatory mode in the mechanical target tracking experiments. Present research indicated that synchronization of body motion occurred only when both of the pair subjects operated in a proactive anticipatory mode. We also presented mathematical models to explain the behavior of the error-correction mode and the synchronization mode.

Influence of the Substrate and Precursor on the Magnetic and Magneto-transport Properties in Magnetite Films

We have investigated the magnetic and transport properties of nanoscaled Fe3O4 films obtained from Chemical Vapor Deposition (CVD) technique using [(FeFe2III)-Fe-II(OBut)(8)] and [Fe-2(III)(OBut)(6)] precursors. Samples were deposited on different substrates (i.e., MgO (001), MgAl2O4 (001) and Al2O3 (0001)) with thicknesses varying from 50 to 350 nm. Atomic Force Microscopy analysis indicated a granular nature of the samples, irrespective of the synthesis conditions (precursor and deposition temperature, T-pre) and substrate. Despite the similar morphology of the films, magnetic and transport properties were found to depend on the precursor used for deposition. Using [(FeFe2III)-Fe-II(OBut)(8)] as precursor resulted in lower resistivity, higher M-S and a sharper magnetization decrease at the Verwey transition (T-V). The temperature dependence of resistivity was found to depend on the precursor and T-pre. We found that the transport is dominated by the density of antiferromagnetic antiphase boundaries (AF-APB's) when [(FeFe2III)-Fe-II(OBut)(8)] precursor and T-pre = 363 K are used. On the other hand, grain boundary-scattering seems to be the main mechanism when [Fe-2(III)(OBut)(6)] is used. The Magnetoresistance (MR(H)) displayed an approximate linear behavior in the high field regime (H > 796 kA/m), with a maximum value at room-temperature of similar to 2-3 % for H = 1592 kA/m, irrespective from the transport mechanism.

Effect of architecture on the phase behavior of AB-type block copolymer melts

Equilibrium phase diagrams are calculated for a selection of two-component block copolymer architectures using self-consistent field theory (SCFT). The topology of the phase diagrams is relatively unaffected by differences in architecture, but the phase boundaries shift significantly in composition. The shifts are consistent with the decomposition of architectures into constituent units as proposed by Gido and coworkers, but there are significant quantitative deviations from this principle in the intermediate-segregation regime. Although the complex phase windows continue to be dominated by the gyroid (G) phase, the regions of the newly discovered Fddd (O^70) phase become appreciable for certain architectures and the perforated-lamellar (PL) phase becomes stable when the complex phase windows shift towards high compositional asymmetry.

The magnetic phase diagram of Gd(2)Sn(2)O(7)

Measurements of the magnetic susceptibility of the frustrated pyrochlore magnet Gd(2)Sn(2)O(7) have been performed at temperatures below T = 5 K and in magnetic fields up to H = 12 T. The phase boundaries determined from these measurements are mapped out in an H-T phase diagram. In this gadolinium compound, where the crystal-field splitting is small and the exchange and dipolar energy are comparable, the Zeeman energy overcomes these competing energies, resulting in at least four magnetic phase transitions below 1 K. These data are compared against those for Gd(2)Ti(2)O(7) and will, we hope, stimulate further studies.

Morphotropic phase boundary and electrical properties of 1-x[Bi 0.5Na0.5]TiO3 -xBa[Zr0.25Ti 0.75]O3 lead-free piezoelectric ceramics

Lead-free solid solutions (1-x)Bi0.5Na0.5TiO 3 (BNT)-xBaZr0.25Ti0.75O3 (BZT) (x=0, 0.01, 0.03, 0.05, and 0.07) were prepared by the solid state reaction method. X-ray diffraction (XRD) and Rietveld refinement analyses of 1-x(BNT)-x(BZT) solid solution ceramic were employed to study the structure of these systems. A morphotropic phase boundary (MPB) between rhombohedral and cubic structures occured at the composition x=0.05. Raman spectroscopy exhibited a splitting of the (TO3) mode at x=0.05 and confirmed the presence of MPB region. Scanning electron microcopy (SEM) images showed a change in the grain shape with the increase of BZT into the BNT matrix lattice. The temperature dependent dielectric study showed a gradual increase in dielectric constant up to x=0.05 and then decrease with further increase in BZT content. Maximum coercive field, remanent polarization and high piezoelectric constant were observed at x=0.05. Both the structural and electrical properties show that the solid solution has an MPB around x=0.05. © 2012 Elsevier Ltd and Techna Group S.r.l.

Regulation of Sticholysin II-Induced Pore Formation by Lipid Bilayer Composition, Phase State, and Interfacial Properties

Sticholysin II (StnII) is a pore-forming toxin that uses sphingomyelin (SM) as the recognition molecule in targeting membranes.After StnII monomers bind to SM, several toxin monomers act in concert to oligomerize into a functional pore. The regulation of StnII binding to SM, and the subsequent pore-formation process, is not fully understood. In this study, we examined how the biophysical properties of bilayers, originating from variations in the SM structure, from the presence of sterol species, or from the presence of increasingly polyunsaturated glycerophospholipids,affected StnII-induced pore formation. StnII-induced pore formation, as determined from calcein permeabilization, was fastest in the pure unsaturated SM bilayers. In 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/saturated SM bilayers (4:1 molar ratio), pore formation became slower as the chain length of the saturated SMs increased from 14 up to 24 carbons. In the POPC/palmitoyl-SM (16:0-SM) 4:1 bilayers, SM could not support pore formation by StnII if dimyristoyl-PC was included at 1:1 stoichiometry with 16:0-SM, suggesting that free clusters of SM were required for toxin binding and/or pore formation. Cholesterol and other sterols facilitated StnII-induced pore formation markedly, but the efficiency did not appear to correlate with the sterol structure. Benzyl alcohol was more efficient than sterols in enhancing the pore-formation process, suggesting that the effect on pore formation originated from alcohol-induced alteration of the hydrogen-bonding network in the SM-containing bilayers. Finally, we observed that pore formation by StnII was enhanced in the PC/16:0-SM 4:1 bilayers, in which the PC was increasingly unsaturated. We conclude that the physical state of bilayer lipids greatly affected pore formation by StnII. Phase boundaries were not required for pore formation, although SM in a gel state attenuated pore formation.

Miscibility and phase separation in blends of phenolphthalein poly(aryl ether ketone) and poly(ethylene oxide): a differential scanning calorimetric study

Miscibility and phase separation in the blends of phenolphthalein poly(aryl ether ketone) (PPAEK) and poly(ethylene oxide) (PEO) were investigated by means of differential scanning calorimetry (DSC). The PPAEK/PEO blends prepared by solution casting from N,N-dimethylformamide (DMF) displayed single composition-dependent glass transition temperatures (T-g), intermediate between those of the pure components, suggesting that the blend system is miscible in the amorphous state at all compositions. All the blends underwent phase separation at higher temperatures and the system exhibited a lower critical solution temperature (LCST) behavior. A step-heating thermal analysis was designed to determine the phase boundaries with DSC. The significant changes in the thermal properties of blends were utilized to judge the mixing status for the blends and the phase diagram was thus established. (C) 2004 Elsevier B.V. All rights reserved.

Mean-field phase diagrams of imbalanced Fermi gases near a Feshbach resonance

We propose phase diagrams for an imbalanced (unequal number of atoms or Fermi surface in two pairing hyperfine states) gas of atomic fermions near a broad Feshbach resonance using mean-field theory. Particularly, in the plane of interaction and polarization we determine the region for a mixed phase composed of normal and superfluid components. We compare our prediction of phase boundaries with the recent measurement and find a good qualitative agreement.

Phase behavior and far-from-equilibrium gelation in charged attractive colloids

In this Rapid Communication we demonstrate the applicability of an augmented Gibbs ensemble Monte Carlo approach for the phase behavior determination of model colloidal systems with short-ranged depletion attraction and long-ranged repulsion. This technique allows for a quantitative determination of the phase boundaries and ground states in such systems. We demonstrate that gelation may occur in systems of this type as the result of arrested microphase separation, even when the equilibrium state of the system is characterized by compact microphase structures.

Shape and chemically anisotropic colloidal particles: A theoretical study of their structure, phase behavior, and slow dynamics

A detailed non-equilibrium state diagram of shape-anisotropic particle fluids is constructed. The effects of particle shape are explored using Naive Mode Coupling Theory (NMCT), and a single particle Non-linear Langevin Equation (NLE) theory. The dynamical behavior of non-ergodic fluids are discussed. We employ a rotationally frozen approach to NMCT in order to determine a transition to center of mass (translational) localization. Both ideal and kinetic glass transitions are found to be highly shape dependent, and uniformly increase with particle dimensionality. The glass transition volume fraction of quasi 1- and 2- dimensional particles fall monotonically with the number of sites (aspect ratio), while 3-dimensional particles display a non-monotonic dependence of glassy vitrification on the number of sites. Introducing interparticle attractions results in a far more complex state diagram. The ideal non-ergodic boundary shows a glass-fluid-gel re-entrance previously predicted for spherical particle fluids. The non-ergodic region of the state diagram presents qualitatively different dynamics in different regimes. They are qualified by the different behaviors of the NLE dynamic free energy. The caging dominated, repulsive glass regime is characterized by long localization lengths and barrier locations, dictated by repulsive hard core interactions, while the bonding dominated gel region has short localization lengths (commensurate with the attraction range), and barrier locations. There exists a small region of the state diagram which is qualified by both glassy and gel localization lengths in the dynamic free energy. A much larger (high volume fraction, and high attraction strength) region of phase space is characterized by short gel-like localization lengths, and long barrier locations. The region is called the attractive glass and represents a 2-step relaxation process whereby a particle first breaks attractive physical bonds, and then escapes its topological cage. The dynamic fragility of fluids are highly particle shape dependent. It increases with particle dimensionality and falls with aspect ratio for quasi 1- and 2- dimentional particles. An ultralocal limit analysis of the NLE theory predicts universalities in the behavior of relaxation times, and elastic moduli. The equlibrium phase diagram of chemically anisotropic Janus spheres and Janus rods are calculated employing a mean field Random Phase Approximation. The calculations for Janus rods are corroborated by the full liquid state Reference Interaction Site Model theory. The Janus particles consist of attractive and repulsive regions. Both rods and spheres display rich phase behavior. The phase diagrams of these systems display fluid, macrophase separated, attraction driven microphase separated, repulsion driven microphase separated and crystalline regimes. Macrophase separation is predicted in highly attractive low volume fraction systems. Attraction driven microphase separation is charaterized by long length scale divergences, where the ordering length scale determines the microphase ordered structures. The ordering length scale of repulsion driven microphase separation is determined by the repulsive range. At the high volume fractions, particles forgo the enthalpic considerations of attractions and repulsions to satisfy hard core constraints and maximize vibrational entropy. This results in site length scale ordering in rods, and the sphere length scale ordering in Janus spheres, i.e., crystallization. A change in the Janus balance of both rods and spheres results in quantitative changes in spinodal temperatures and the position of phase boundaries. However, a change in the block sequence of Janus rods causes qualitative changes in the type of microphase ordered state, and induces prominent features (such as the Lifshitz point) in the phase diagrams of these systems. A detailed study of the number of nearest neighbors in Janus rod systems reflect a deep connection between this local measure of structure, and the structure factor which represents the most global measure of order.

Bimanual co-ordination in Parkinson's disease

The basal ganglia may be involved in bimanual co-ordination. Parkinson's disease (which impairs basal ganglia output) is clinically reported to cause difficulties in the performance of co-ordinated bimanual movements. Nevertheless, any bimanual co-ordination difficulties may be task specific, as experimental observations are equivocal. To infer the role of the basal ganglia in co-ordinating the two arms, this study investigated the bimanual co-ordination of patients with Parkinson's disease. Sixteen Parkinson's disease patients and matched control subjects performed a bimanual cranking task, at different speeds (1 and 2 Hz) and phase relationships. All subjects performed the required bimanual in-phase movement on a pair of cranks, at fast (2 Hz) and slow (1 Hz) speeds. However the Parkinson's disease patients were unable to perform the asymmetrical anti-phase movement, in which rotation of the cranks differed by 180 degrees, at either speed; but instead reverted to the in-phase symmetrical movement. For Parkinson's disease patients, performance of the in-phase movement was more accurate and stable when an external timing cue was used; however for anti-phase movement, the external cue accentuated the tendency for patients to revert to more symmetrical, in-phase movements.

Bimanual co-ordination in Huntington's disease

The ability of Huntington's disease patients to co-ordinate their two hands with and without external cueing was investigated. Twelve Huntington's disease patients and sex- and age-matched controls performed a bimanual cranking task at two speeds (0.5 Hz, 1.5 Hz) and phase relationships (in-phase, anti-phase), with and without an external metronome cue. Data were sampled at 200 Hz, and raw displacement data for each hand, mean and standard deviation measures of the relative positions of the two hands and their velocities were then calculated. All participants could perform the in-phase movement, at both speeds; however, the Huntington's disease patients were more variable and less accurate than the control participants, particularly at the fast speed. While controls could perform the anti-phase movement, in which rotation of the cranks differed by 180 degrees at both speeds, Huntington's disease patients were unable to do so at either speed, reverting to the in-phase movement at the slow speed. An external metronome cue did not improve the performance of the Huntington's disease patients, which differentiated this group from patients suffering from Parkinson's disease. The Huntington's disease patients' inability to perform the anti-phase movement may be due to damage to the basal ganglia and its output regions.

The acquisition of movement skills: Practice enhances the dynamic stability of bimanual coordination

During bimanual movements, two relatively stable inherent patterns of coordination (in-phase and anti-phase) are displayed (e.g., Kelso, Am. J. Physiol. 246 (1984) R1000). Recent research has shown that new patterns of coordination can be learned. For example, following practice a 90 degrees out-of-phase pattern can emerge as an additional, relatively stable, state (e.g., Zanone & Kelso, J. Exp. Psychol.: Human Performance and Perception 18 (1992) 403). On this basis, it has been concluded that practice leads to the evolution and stabilisation of the newly learned pattern and that this process of learning changes the entire attractor layout of the dynamic system. A general feature of such research has been to observe the changes of the targeted pattern's stability characteristics during training at a single movement frequency. The present study was designed to examine how practice affects the maintenance of a coordinated pattern as the movement frequency is scaled. Eleven volunteers were asked to perform a bimanual forearm pronation-supination task. Time to transition onset was used as an index of the subjects' ability to maintain two symmetrically opposite coordinated patterns (target task - 90 degrees out-of-phase - transfer task - 270 degrees out-of-phase). Their ability to maintain the target task and the transfer task were examined again after five practice sessions each consisting of 15 trials of only the 90 degrees out-of-phase pattern. Concurrent performance feedback (a Lissajous figure) was available to the participants during each practice trial. A comparison of the time to transition onset showed that the target task was more stable after practice (p = 0.025). These changes were still observed one week (p = 0.05) and two months (p = 0.075) after the practice period. Changes in the stability of the transfer task were not observed until two months after practice (p = 0.025). Notably, following practice, transitions from the 90 degrees pattern were generally to the anti-phase (180 degrees) pattern, whereas, transitions from the 270 degrees pattern were to the 90 degrees pattern. These results suggest that practice does improve the stability of a 90 degrees pattern, and that such improvements are transferable to the performance of the unpractised 270 degrees pattern. In addition, the anti-phase pattern remained more stable than the practised 90 degrees pattern throughout. (C) 2001 Elsevier Science B.V. All rights reserved.

Bimodal information increases spontaneous interpersonal synchronization of goal directed upper limb movements

When interacting with each other, people often synchronize spontaneously their movements, e.g. during pendulum swinging, chair rocking[5], walking [4][7], and when executing periodic forearm movements[3].Although the spatiotemporal information that establishes the coupling, leading to synchronization, might be provided by several perceptual systems, the systematic study of different sensory modalities contribution is widely neglected. Considering a) differences in the sensory dominance on the spatial and temporal dimension[5] , b) different cue combination and integration strategies [1][2], and c) that sensory information might provide different aspects of the same event, synchronization should be moderated by the type of sensory modality. Here, 9 naïve participants placed a bottle periodically between two target zones, 40 times, in 12 conditions while sitting in front of a confederate executing the same task. The participant could a) see and hear, b) see , c) hear the confederate, d) or audiovisual information about the movements of the confederate was absent. The couple started in 3 different relative positions (i.e., in-phase, anti-phase, out of phase). A retro-reflective marker was attached to the top of the bottles. Bottle displacement was captured by a motion capture system. We analyzed the variability of the continuous relative phase reflecting the degree of synchronization. Results indicate the emergence of spontaneous synchronization, an increase with bimodal information, and an influence of the initial phase relation on the particular synchronization pattern. Results have theoretical implication for studying cue combination in interpersonal coordination and are consistent with coupled oscillator models.