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Sample records for dynamic visuomotor rotations

  1. Eye-hand coordination during dynamic visuomotor rotations.

    Directory of Open Access Journals (Sweden)

    Lorenzo Masia

    Full Text Available BACKGROUND: for many technology-driven visuomotor tasks such as tele-surgery, human operators face situations in which the frames of reference for vision and action are misaligned and need to be compensated in order to perform the tasks with the necessary precision. The cognitive mechanisms for the selection of appropriate frames of reference are still not fully understood. This study investigated the effect of changing visual and kinesthetic frames of reference during wrist pointing, simulating activities typical for tele-operations. METHODS: using a robotic manipulandum, subjects had to perform center-out pointing movements to visual targets presented on a computer screen, by coordinating wrist flexion/extension with abduction/adduction. We compared movements in which the frames of reference were aligned (unperturbed condition with movements performed under different combinations of visual/kinesthetic dynamic perturbations. The visual frame of reference was centered to the computer screen, while the kinesthetic frame was centered around the wrist joint. Both frames changed their orientation dynamically (angular velocity = 36 degrees /s with respect to the head-centered frame of reference (the eyes. Perturbations were either unimodal (visual or kinesthetic, or bimodal (visual+kinesthetic. As expected, pointing performance was best in the unperturbed condition. The spatial pointing error dramatically worsened during both unimodal and most bimodal conditions. However, in the bimodal condition, in which both disturbances were in phase, adaptation was very fast and kinematic performance indicators approached the values of the unperturbed condition. CONCLUSIONS: this result suggests that subjects learned to exploit an "affordance" made available by the invariant phase relation between the visual and kinesthetic frames. It seems that after detecting such invariance, subjects used the kinesthetic input as an informative signal rather than a

  2. Generalization of stochastic visuomotor rotations.

    Directory of Open Access Journals (Sweden)

    Hugo L Fernandes

    Full Text Available Generalization studies examine the influence of perturbations imposed on one movement onto other movements. The strength of generalization is traditionally interpreted as a reflection of the similarity of the underlying neural representations. Uncertainty fundamentally affects both sensory integration and learning and is at the heart of many theories of neural representation. However, little is known about how uncertainty, resulting from variability in the environment, affects generalization curves. Here we extend standard movement generalization experiments to ask how uncertainty affects the generalization of visuomotor rotations. We find that although uncertainty affects how fast subjects learn, the perturbation generalizes independently of uncertainty.

  3. Enhancing consolidation of a rotational visuomotor adaptation task through acute exercise

    Science.gov (United States)

    Busquets, Albert; Lopez-Alonso, Virginia; Fernandez-del-Olmo, Miguel; Angulo-Barroso, Rosa

    2017-01-01

    We assessed the effect of a single bout of intense exercise on the adaptation and consolidation of a rotational visuomotor task, together with the effect of the order of exercise presentation relative to the learning task. Healthy adult participants (n = 29) were randomly allocated to one of three experimental groups: (1) exercise before task practice, (2) exercise after task practice, and (3) task practice only. After familiarization with the learning task, participants undertook a baseline practice set. Then, four 60° clockwise rotational sets were performed, comprising an adaptation set and three retention sets at 1 h, 24 h, and 7 days after the adaptation set. Depending on the experimental group, exercise was presented before or after the adaptation sets. We found that error reduction during adaptation was similar regardless of when exercise was presented. During retention, significant error reduction was found in the retention set at 1 h for both exercise groups, but this enhancement was not present during subsequent retention sets, with no differences present between exercise groups. We conclude that an acute bout of intense exercise could positively affect retention, although the order in which exercise is presented does not appear to influence its benefits during the early stages of consolidation. PMID:28406936

  4. Structural dynamics in rotating systems

    Science.gov (United States)

    Kiraly, Louis J.

    1993-01-01

    Major issues and recent advances in the structural dynamics of rotating systems are summarized. The objectives and benefits of such systems are briefly discussed. Directions for future research are suggested.

  5. Multiple representations and mechanisms for visuomotor adaptation in young children.

    Science.gov (United States)

    Tahej, Pierre-Karim; Ferrel-Chapus, Carole; Olivier, Isabelle; Ginhac, Dominique; Rolland, Jean-Pierre

    2012-12-01

    In this study, we utilized transformed spatial mappings to perturb visuomotor integration in 5-yr-old children and adults. The participants were asked to perform pointing movements under five different conditions of visuomotor rotation (from 0° to 180°), which were designed to reveal explicit vs. implicit representations as well as the mechanisms underlying the visual-motor mapping. Several tests allowed us to separately evaluate sensorimotor (i.e., the dynamic dimension of movement) and cognitive (i.e., the explicit representations of target position and the strategies used by the participants) representations of visuo-proprioceptive distortion. Our results indicate that children do not establish representations in the same manner as adults and that children exhibit multiple visuomotor representations. Sensorimotor representations were relatively precise, presumably due to the recovery of proprioceptive information and efferent copy. Furthermore, a bidirectional mechanism was used to re-map visual and motor spaces. In contrast, cognitive representations were supplied with visual information and followed a unidirectional visual-motor mapping. Therefore, it appears that sensorimotor mechanisms develop before the use of explicit strategies during development, and young children showed impaired visuomotor adaptation when confronted with large distortions.

  6. Dynamics of Rotating, Magnetized Neutron Stars

    OpenAIRE

    Liebling, Steven L.

    2010-01-01

    Using a fully general relativistic implementation of ideal magnetohydrodynamics with no assumed symmetries in three spatial dimensions, the dynamics of magnetized, rigidly rotating neutron stars are studied. Beginning with fully consistent initial data constructed with Magstar, part of the Lorene project, we study the dynamics and stability of rotating, magnetized polytropic stars as models of neutron stars. Evolutions suggest that some of these rotating, magnetized stars may be minimally uns...

  7. Dynamic rotation and stretch tensors from a dynamic polar decomposition

    Science.gov (United States)

    Haller, George

    2016-01-01

    The local rigid-body component of continuum deformation is typically characterized by the rotation tensor, obtained from the polar decomposition of the deformation gradient. Beyond its well-known merits, the polar rotation tensor also has a lesser known dynamical inconsistency: it does not satisfy the fundamental superposition principle of rigid-body rotations over adjacent time intervals. As a consequence, the polar rotation diverts from the observed mean material rotation of fibers in fluids, and introduces a purely kinematic memory effect into computed material rotation. Here we derive a generalized polar decomposition for linear processes that yields a unique, dynamically consistent rotation component, the dynamic rotation tensor, for the deformation gradient. The left dynamic stretch tensor is objective, and shares the principal strain values and axes with its classic polar counterpart. Unlike its classic polar counterpart, however, the dynamic stretch tensor evolves in time without spin. The dynamic rotation tensor further decomposes into a spatially constant mean rotation tensor and a dynamically consistent relative rotation tensor that is objective for planar deformations. We also obtain simple expressions for dynamic analogues of Cauchy's mean rotation angle that characterize a deforming body objectively.

  8. Dynamic rotating-shield brachytherapy.

    Science.gov (United States)

    Liu, Yunlong; Flynn, Ryan T; Kim, Yusung; Yang, Wenjun; Wu, Xiaodong

    2013-12-01

    To present dynamic rotating shield brachytherapy (D-RSBT), a novel form of high-dose-rate brachytherapy (HDR-BT) with electronic brachytherapy source, where the radiation shield is capable of changing emission angles during the radiation delivery process. A D-RSBT system uses two layers of independently rotating tungsten alloy shields, each with a 180° azimuthal emission angle. The D-RSBT planning is separated into two stages: anchor plan optimization and optimal sequencing. In the anchor plan optimization, anchor plans are generated by maximizing the D90 for the high-risk clinical-tumor-volume (HR-CTV) assuming a fixed azimuthal emission angle of 11.25°. In the optimal sequencing, treatment plans that most closely approximate the anchor plans under the delivery-time constraint will be efficiently computed. Treatment plans for five cervical cancer patients were generated for D-RSBT, single-shield RSBT (S-RSBT), and (192)Ir-based intracavitary brachytherapy with supplementary interstitial brachytherapy (IS + ICBT) assuming five treatment fractions. External beam radiotherapy doses of 45 Gy in 25 fractions of 1.8 Gy each were accounted for. The high-risk clinical target volume (HR-CTV) doses were escalated such that the D2cc of the rectum, sigmoid colon, or bladder reached its tolerance equivalent dose in 2 Gy fractions (EQD2 with α∕β = 3 Gy) of 75 Gy, 75 Gy, or 90 Gy, respectively. For the patients considered, IS + ICBT had an average total dwell time of 5.7 minutes∕fraction (min∕fx) assuming a 10 Ci(192)Ir source, and the average HR-CTV D90 was 78.9 Gy. In order to match the HR-CTV D90 of IS + ICBT, D-RSBT required an average of 10.1 min∕fx more delivery time, and S-RSBT required 6.7 min∕fx more. If an additional 20 min∕fx of delivery time is allowed beyond that of the IS + ICBT case, D-RSBT and S-RSBT increased the HR-CTV D90 above IS + ICBT by an average of 16.3 Gy and 9.1 Gy, respectively. For cervical cancer patients, D-RSBT can boost HR-CTV D90

  9. Dynamics of Rotationally Fissioned Asteroids

    Science.gov (United States)

    Jacobson, Seth A.; Scheeres, D. J.

    2010-10-01

    We present a model for near-Earth asteroid (NEA) rotational fission that results in the evolution of all observed types of NEA systems: synchronous binaries, asteroid pairs, doubly synchronous binaries, high-e binaries, ternary systems, and contact binaries. The model consists of "rubble pile” asteroid geophysics, the YORP and binary YORP effects, and mutual gravitational interactions. An NEA can be modeled as a ``rubble pile"--a collection of gravitationally bound boulders with a distribution of size scales and very little tensile strength between them. The YORP effect torques a "rubble pile” asteroid until the asteroid reaches its disruption spin limit, and then two collections of boulders will enter into orbit about each other determined by the largest distance between mass centers. This binary system dynamically evolves under the effects of non-spherical gravitational potentials, solar gravitational perturbations, and mutual body tides. The coupling between the spin states and orbit state chaotically drives the system into the observed asteroid classes with mass ratio, q, distinguishing two evolutionary tracks. High mass ratio systems, q>0.2, evolve tidally into doubly synchronous binaries and then continued to be evolved by BYORP. Low mass ratio systems, qfission, creating a chaotic ternary system. We call this new process secondary fission. The resulting triple system may eject one body or, more often, send one into a slow speed impact with the primary. These processes tend to stabilize the initially chaotic binaries to create synchronous binaries. These results emphasize the importance of the initial component size distribution and configuration within the parent body. This work is supported by NASA's PGG and OPR programs through grants: NNX08AL51G and NNX09AU23G.

  10. Statics and rotational dynamics of composite beams

    CERN Document Server

    Ghorashi, Mehrdaad

    2016-01-01

    This book presents a comprehensive study of the nonlinear statics and dynamics of composite beams and consists of solutions with and without active elements embedded in the beams. The static solution provides the initial conditions for the dynamic analysis. The dynamic problems considered include the analyses of clamped (hingeless) and articulated (hinged) accelerating rotating beams. Two independent numerical solutions for the steady state and the transient responses are presented. The author illustrates that the transient solution of the nonlinear formulation of accelerating rotating beam converges to the steady state solution obtained by the shooting method. Other key areas considered include calculation of the effect of perturbing the steady state solution, coupled nonlinear flap-lag dynamics of a rotating articulated beam with hinge offset and aerodynamic damping, and static and dynamic responses of nonlinear composite beams with embedded anisotropic piezo-composite actuators. The book is intended as a t...

  11. Dynamics of Rotation of Super-Earths

    CERN Document Server

    Callegari, Nelson

    2012-01-01

    We numerically investigate the dynamics of rotation of several close-in terrestrial exoplanets candidates. In our model, the rotation of the planet is disturbed by the torque of the central star due to the asymmetric equilibrium figure of the planet. We use surfaces of section to explore numerically the rotation phase space of the systems adopting different sets of parameters and initial conditions close to the main spin-orbit resonant states. We show that, depending on some parameters of the system like the radius and mass of the planet, orbital eccentricity etc, the rotation can be strongly perturbed and a chaotic layer around the synchronous state may occupy a significant region of the phase space. 55 Cnc e is an example.

  12. History of rotating machinery dynamics

    CERN Document Server

    Rao, JS

    2011-01-01

    This book starts with the invention of the wheel nearly 5000 years ago, and via Archimedes, Aristotle and Hero describes the first practical applications such as water wheels and grinding wheels, pushing on to more rigorous scientific research by inquiring minds such as Leonardo da Vinci and Copernicus in later ages. Newton and Leibniz followed, and beam structures received maximum attention three centuries ago. As focus shifts and related disciplines such as mathematics and physics also develop, slowly turbomachines and rotor and blade dynamics as we know the subject now take shape. While the

  13. Robustness of muscle synergies during visuomotor adaptation

    Directory of Open Access Journals (Sweden)

    Reinhard eGentner

    2013-09-01

    Full Text Available During visuomotor adaptation a novel mapping between visual targets and motor commands is gradually acquired. How muscle activation patterns are affected by this process is an open question. We tested whether the structure of muscle synergies is preserved during adaptation to a visuomotor rotation. Eight subjects applied targeted isometric forces on a handle instrumented with a force transducer while electromyographic (EMG activity was recorded from 13 shoulder and elbow muscles. The recorded forces were mapped into horizontal displacements of a virtual sphere with simulated mass, elasticity, and damping. The task consisted of moving the sphere to a target at one of eight equally spaced directions. Subjects performed three baseline blocks of 32 trials, followed by six blocks with a 45° CW rotation applied to the planar force, and finally three wash-out blocks without the perturbation. The sphere position at 100 ms after movement onset revealed significant directional error at the beginning of the rotation, a gradual learning in subsequent blocks, and aftereffects at the beginning of the wash-out. The change in initial force direction was closely related to the change in directional tuning of the initial EMG activity of most muscles. Throughout the experiment muscle synergies extracted using a non-negative matrix factorization algorithm from the muscle patterns recorded during the baseline blocks could reconstruct the muscle patterns of all other blocks with an accuracy significantly higher than chance indicating structural robustness. In addition, the synergies extracted from individual blocks remained similar to the baseline synergies throughout the experiment. Thus synergy structure is robust during visuomotor adaptation suggesting that changes in muscle patterns are obtained by rotating the directional tuning of the synergy recruitment.

  14. Finite Element Computational Dynamics of Rotating Systems

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    Jaroslav Mackerle

    1999-01-01

    Full Text Available This bibliography lists references to papers, conference proceedings and theses/dissertations dealing with finite element analysis of rotor dynamics problems that were published in 1994–1998. It contains 319 citations. Also included, as separate subsections, are finite element analyses of rotor elements – discs, shafts, spindles, and blades. Topics dealing with fracture mechanics, contact and stability problems of rotating machinery are also considered in specific sections. The last part of the bibliography presents papers dealing with specific industrial applications.

  15. Modulation of gamma and theta spectral amplitude and phase synchronization is associated with the development of visuo-motor learning.

    Science.gov (United States)

    Perfetti, Bernardo; Moisello, Clara; Landsness, Eric Carl; Kvint, Svetlana; Lanzafame, Simona; Onofrj, Marco; Di Rocco, Alessandro; Tononi, Giulio; Ghilardi, M Felice

    2011-10-12

    The formation of new motor memories, which is fundamental for efficient performance during adaptation to a visuo-motor rotation, occurs when accurate planning is achieved mostly with feedforward mechanisms. The dynamics of brain activity underlying the switch from feedback to feedforward control is still matter of debate. Based on the results of studies in declarative learning, it is likely that phase synchronization of low and high frequencies as well as their temporal modulation in power amplitude underlie the formation of new motor memories during visuo-motor adaptation. High-density EEG (256 electrodes) was recorded in 17 normal human subjects during adaptation to a visuo-motor rotation of 60° in four incremental steps of 15°. We found that initial learning is associated with enhancement of gamma power in a right parietal region during movement execution as well as gamma/theta phase coherence during movement planning. Late stages of learning are instead accompanied by an increase of theta power over that same right parietal region during movement planning, which is correlated with the degree of learning and retention. Altogether, these results suggest that the formation of new motor memories and, thus, the switch from feedback to feedforward control is associated with the modulation of gamma and theta spectral activities, with respect to their amplitude and phase, during movement planning and execution. Specifically, we propose that gamma/theta phase coupling plays a pivotal role in the integration of a new representation into motor memories.

  16. Rotation dynamics with & without Internal Transport Barriers

    Science.gov (United States)

    Dif-Pradalier, Guilhem; Diamond, Patrick H.; Chang, C. S.; Ku, S.; Sarazin, Y.; Grandgirard, V.; Abiteboul, J.; Garbet, X.; Ghendrih, Ph.; Strugarek, A.

    2009-11-01

    We investigate the dynamics of both poloidal and toroidal flows in the presence (or absence) of a reversed safety factor profile through a scan in the incoming heat power applied to the plasma. Doing so, it incidentally also addresses the question of a power threshold for a self-consistent ITB formation in gyrokinetic modeling. As a prime candidate to drive the system away from its neoclassical prediction, we recently showed evidence of turbulence-generated poloidal rotation, consistently with earlier theories. Accurate calculation of the radial electric field is central. Accordingly, description of the mean profile dynamics, as done in full--f flux-driven models is shown to take on a very prominent role. The study is performed using both the Gysela and Xgc--1 gyrokinetic codes with Enhanced Reverse Shear (ERS)-like parameters.

  17. Dynamic Instability of Rapidly Rotating Protostars

    Science.gov (United States)

    Pickett, B. K.; Durisen, R. H.; Johnson, M. S.; Davis, G. A.

    1994-12-01

    Modern studies of collapse and fragmentation of protostellar clouds suggest a wide variety of outcomes, depending on the assumed initial conditions. Individual equilibrium objects which result from collapse are likely to be in rapid rotation and can have a wide range of structures. We have undertaken a survey of parameter space in order to examine the role of dynamic instabilities in the subsequent evolution of these objects. For the purposes of conducting a systematic study, we so far have considered only the n = 3/2 polytropic equilibrium states that might form from the collapse of uniformly rotating spherical clouds. By varying the central concentration of the assumed initial cloud, we obtain equilibrium states distinguished primarily by their different specific angular momentum distributions. These equilibrium states span the range between starlike objects with angular momentum distributions analogous to the Maclaurin spheroids and objects more accurately described as massive Keplerian disks around stars. Using a new SCF code to generate the n = 3/2 axisymmetric equilibrium states and an improved 3D hydrodynamics code, we have investigated the the onset and nature of global dynamic instabilities in these objects. The starlike objects are unstable to barlike instabilities at T/|W| gtorder 0.27, where T/|W| is the ratio of total rotational kinetic energy to gravitational potential energy. These instabilities are vigorous and lead to violent ejection of mass and angular momentum. As the angular momentum distribution shifts to the other extreme, one- and two-armed spiral instabilities begin to dominate at considerably lower T/|W|. These instabilities appear to be driven by the SLING and swing mechanisms. In extremely flattened disks, one-armed spirals dominate all other disturbances but eventually saturate at nonlinear amplitude without producing fragmentation. We conclude that the nature of the global instabilities encountered during the process of star formation

  18. Rotation and internal dynamics of terrestrial planets

    Science.gov (United States)

    Dehant, V.

    2009-04-01

    the state and dimension of the core. Length-of-day variations are deviations from the uniform rotation rate of the planet. They are mainly related to the dynamics of the geophysical fluids of the system, mainly the atmosphere of Mars. The seasonal condensation/sublimation of the icecaps induces a large change in the length-of-day at the seasonal periods. These measurements at Mars will be compared with those of the Earth. The BepiColombo mission to Mercury will also allow measuring the rotation of this small planet and in particular the libration, which will also bring insight on the interior of Mercury.

  19. Visuomotor control of neck surface electromyography in Parkinson's disease.

    Science.gov (United States)

    Malloy, Jessica R; Valentin, Juliana C; Hands, Gabrielle L; Stevens, Christina A; Langmore, Susan E; Noordzij, J Pieter; Stepp, Cara E

    2014-01-01

    To compare performance of individuals with Parkinson's disease (PD) and age-matched controls on a visuomotor tracking task controlled via surface electromyography (sEMG). Twenty-seven adults with PD and twenty-four older controls produced dry swallows and completed a visuomotor tracking task utilizing both static and dynamic targets. sEMG was recorded at the anterior neck and submental surface during both tasks. There was no significant difference in visuomotor tracking ability between cohorts. Post hoc analyses indicated that there was no significant difference between participant groups in the strength or duration of swallows as measured by sEMG but that participants with PD showed a trend for decreased swallow durations at the anterior neck (padj = 0.067) whereas controls showed a trend for increased durations at the anterior neck (padj = 0.112), compared to the submental surface. However, there were no significant correlations between swallowing behavior and visuomotor tracking ability. There were no significant differences in visuomotor tracking performance between individuals with PD and controls. Furthermore, there was no relationship between tracking ability and swallowing behavior. We conclude that sEMG-mediated biofeedback may have limited promise as a tool for treating PD-related dysphagia.

  20. Generalization of visuomotor adaptation depends on the spatial characteristic of visual workspace

    OpenAIRE

    2012-01-01

    The present study aims to address a novel aspect of visuomotor adaptation and its generalization. It is based on the assumption that the spatial structure of the distal action space is crucial for generalization. In the experiments, the distal action spaces could manifest either a symmetric or parallel structure. The imposed visuomotor rotations in the adaptation and the following generalization were either the same or opposing each other. In the generalization phase, motor bias resulting fro...

  1. Dynamic behaviour of a rotating cracked beam

    Science.gov (United States)

    Yashar, Ahmed; Ghandchi-Tehrani, Maryam; Ferguson, Neil

    2016-09-01

    This paper presents a new approach to investigate and analyse the vibrational behaviour of cracked rotating cantilever beams, which can for example represent helicopter or wind turbine blades. The analytical Hamiltonian method is used in modelling the rotating beam and two numerical methods, the Rayleigh-Ritz and FEM, are used to study the natural frequencies and the mode shapes of the intact rotating beams. Subsequently, a crack is introduced into the FE model and simulations are performed to identify the modal characteristics for an open cracked rotating beam. The effect of various parameters such as non-dimensional rotating speed, hub ratio and slenderness ratio are investigated for both the intact and the cracked rotating beam, and in both directions of chordwise and flapwise motion. The veering phenomena in the natural frequencies as a function of the rotational speed and the buckling speed are considered with respect to the slenderness ratio. In addition, the mode shapes obtained for the flapwise vibration are compared using the modal assurance criterion (MAC). Finally, a new three dimensional design chart is produced, showing the effect of crack location and depth on the natural frequencies of the rotating beam. This chart will be subsequently important in identifying crack defects in rotating blades.

  2. Some dynamic problems of rotating windmill systems

    Science.gov (United States)

    Dugundji, J.

    1976-01-01

    The basic whirl stability of a rotating windmill on a flexible tower is reviewed. Effects of unbalance, gravity force, gyroscopic moments, and aerodynamics are discussed. Some experimental results on a small model windmill are given.

  3. Coherent spin-rotational dynamics of oxygen super rotors

    CERN Document Server

    Milner, Alexander A; Milner, Valery

    2014-01-01

    We use state- and time-resolved coherent Raman spectroscopy to study the rotational dynamics of oxygen molecules in ultra-high rotational states. While it is possible to reach rotational quantum numbers up to $N \\approx 50$ by increasing the gas temperature to 1500 K, low population levels and gas densities result in correspondingly weak optical response. By spinning O$_2$ molecules with an optical centrifuge, we efficiently excite extreme rotational states with $N\\leqslant 109$ in high-density room temperature ensembles. Fast molecular rotation results in the enhanced robustness of the created rotational wave packets against collisions, enabling us to observe the effects of weak spin-rotation coupling in the coherent rotational dynamics of oxygen. The decay rate of spin-rotation coherence due to collisions is measured as a function of the molecular angular momentum and explained in terms of the general scaling law. We find that at high values of $N$, the rotational decoherence of oxygen is much faster than t...

  4. Rotational control of asymmetric molecules: dipole- vs. polarizability- driven rotational dynamics

    CERN Document Server

    Damari, Ran; Fleischer, Sharly

    2016-01-01

    We experimentally study the optical- and terahertz- induced rotational dynamics of asymmetric molecules in the gas phase. Terahertz and optical fields are identified as two distinct control handles over asymmetric molecules, as they couple to the rotational degrees of freedom via the molecular- dipole and polarizability selectively. The distinction between those two rotational handles is highlighted by different types of quantum revivals observed in long duration (>100ps) field-free rotational evolution. The experimental results are in excellent agreement with Random Phase Wave Function simulations [Phys. Rev. A 91, 063420 (2015)] and provide verification of the RPWF as an efficient method for calculating asymmetric molecular dynamics at ambient temperatures, where exact calculation methods are practically not feasible. Our observations and analysis pave the way for orchestrated excitations by both optical and THz fields as complementary rotational handles, that enable a plethora of new possibilities in three...

  5. Dynamical analysis of sea-breeze hodograph rotation in Sardinia

    Directory of Open Access Journals (Sweden)

    N. Moisseeva

    2014-09-01

    Full Text Available This study investigates the diurnal evolution of sea-breeze rotation over an island in the mid-latitudes. Earlier research on sea-breezes in Sardinia shows that the onshore winds around various coasts of the island exhibit both the theoretically predicted clockwise rotation as well as seemingly anomalous anti-clockwise rotation. A non-hydrostatic fully compressible numerical model (WRF is used to simulate wind fields on and around the island on previously-studied sea-breeze days and is shown to accurately capture the circulation on all coasts. Diurnal rotation of wind is examined and patterns of clockwise and anti-clockwise rotation are identified. A dynamical analysis is performed by extracting individual forcing terms from the horizontal momentum equations. Analysis of several regions around the island shows that the direction of rotation is a result of a complex interaction between near-surface and synoptic pressure gradient, Coriolis and advection forcings. An idealized simulation is performed over an artificial island with dramatically simplified topography, yet similar dimensions and latitude to Sardinia. Dynamical analysis of the idealized case reveals a rather different pattern of hodograph rotation to the real Sardinia, yet similar underlying dynamics. The research provides new insights into the dynamics underlying sea-breeze hodograph rotation, especially in coastal zones with complex topography and/or coastline.

  6. Rotational dynamics of propylene inside Na-Y zeolite cages

    Indian Academy of Sciences (India)

    V K Sharma; Mala N Rao; Siddharth Gautam; A K Tripathi; V S Kamble; S L Chaplot; R Mukhopadhyay

    2008-11-01

    We report here the quasielastic neutron scattering (QENS) studies on the dynamics of propylene inside Na-Y zeolite using triple axis spectrometer (TAS) at Dhruva reactor, Trombay. Molecular dynamics (MD) simulations performed on the system had shown that the rotational motion involves energy larger than that involved in the translational motion. Therefore, rotational motion was not observed in our earlier QENS studies on propylene adsorbed Na-Y zeolite using a higher resolution spectrometer at Dhruva. Analysis of the TAS spectra revealed that the quasielastic broadening observed in propylene-loaded zeolite spectra is due to the rotational motion of the propylene molecules. This is consistent with our simulation result. Further, the rotational motion is found to be isotropic. The rotational diffusion coefficient has been obtained.

  7. Assessing visuospatial abilities in healthy aging: A novel visuomotor task

    Directory of Open Access Journals (Sweden)

    Natalie eDe Bruin

    2016-02-01

    Full Text Available This study examined the efficacy of a novel reaching-and-grasping task in determining visuospatial abilities across adulthood. The task required male and female young (18-25 years and older adults (60-82 years to replicate a series of complex models by locating and retrieving the appropriate building blocks from an array. The task allows visuospatial complexity to be manipulated independently from the visuomotor demands. Mental rotation and spatial visualisation abilities were assessed. The results showed that the time taken to complete the tasks increased with increased mental rotation complexity. Patterns of hand use were also influenced by the complexity of the models being constructed with right hand use being greater for the less complex models. In addition, although older adults consistently performed the visuomotor tasks slower than the younger adults, their performance was comparable when expressed as the percent change in task demands. This is suggestive that spatial abilities are preserved in older adults. Given the ecologically validity, the described task is an excellent candidate for investigating (1 developmental, (2 sex-based and (3 pathology-based differences in spatial abilities in the visuomotor domain.

  8. Dynamic balancing with rotating radial electromagnetic force

    Institute of Scientific and Technical Information of China (English)

    李勇; 陆永平

    2004-01-01

    A method of producing rotating radial electromagnetic force with a separable structure is proposed,and an experimental model was designed on which open loop vibration control experiments were carried out. Experimental results prove that the electromagnetic force designed has a constant magnitude and an uniform speed,and the idea of using an electromagnetic force as an active control in automatic balancing is correct in principle,and practicable in engineering.

  9. Rotational Brownian Dynamics simulations of clathrin cage formation

    Energy Technology Data Exchange (ETDEWEB)

    Ilie, Ioana M.; Briels, Wim J. [Computational BioPhysics, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Otter, Wouter K. den, E-mail: w.k.denotter@utwente.nl [Computational BioPhysics, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Multi Scale Mechanics, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2014-08-14

    The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the assembly dynamics. However, Brownian Dynamics of rotating anisotropic particles gives rise to a number of complications not encountered in translational Brownian Dynamics. We thoroughly test the Rotational Brownian Dynamics scheme proposed by Naess and Elsgaeter [Macromol. Theory Simul. 13, 419 (2004); Naess and Elsgaeter Macromol. Theory Simul. 14, 300 (2005)], confirming its validity. We then apply the algorithm to simulate a patchy particle model of clathrin, a three-legged protein involved in vesicle production from lipid membranes during endocytosis. Using this algorithm we recover time scales for cage assembly comparable to those from experiments. We also briefly discuss the undulatory dynamics of the polyhedral cage.

  10. Rotational Brownian dynamics simulations of clathrin cage formation.

    Science.gov (United States)

    Ilie, Ioana M; den Otter, Wouter K; Briels, Wim J

    2014-08-14

    The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the assembly dynamics. However, Brownian Dynamics of rotating anisotropic particles gives rise to a number of complications not encountered in translational Brownian Dynamics. We thoroughly test the Rotational Brownian Dynamics scheme proposed by Naess and Elsgaeter [Macromol. Theory Simul. 13, 419 (2004); Naess and Elsgaeter Macromol. Theory Simul. 14, 300 (2005)], confirming its validity. We then apply the algorithm to simulate a patchy particle model of clathrin, a three-legged protein involved in vesicle production from lipid membranes during endocytosis. Using this algorithm we recover time scales for cage assembly comparable to those from experiments. We also briefly discuss the undulatory dynamics of the polyhedral cage.

  11. Dynamical Tides in Compact White Dwarf Binaries: Influence of Rotation

    CERN Document Server

    Fuller, Jim

    2014-01-01

    Tidal interactions play an important role in the evolution and ultimate fate of compact white dwarf (WD) binaries. Not only do tides affect the pre-merger state (such as temperature and rotation rate) of the WDs, but they may also determine which systems merge and which undergo stable mass transfer. In this paper, we attempt to quantify the effects of rotation on tidal angular momentum transport in binary stars, with specific calculations applied to WD stellar models. We incorporate the effect of rotation using the traditional approximation, in which the dynamically excited gravity waves within the WDs are transformed into gravito-inertial Hough waves. The Coriolis force has only a minor effect on prograde gravity waves, and previous results predicting the tidal spin-up and heating of inspiraling WDs are not significantly modified. However, rotation strongly alters retrograde gravity waves and inertial waves, with important consequences for the tidal spin-down of accreting WDs. We identify new dynamical tidal...

  12. Faraday resonance in dynamical bar instability of differentially rotating stars

    CERN Document Server

    Saijo, Motoyuki

    2008-01-01

    We investigate the nonlinear behaviour of the dynamically unstable rotating star for the bar mode by three-dimensional hydrodynamics in Newtonian gravity. We find that an oscillation along the rotation axis is induced throughout the growth of the unstable bar mode, and that its characteristic frequency is twice as that of the bar mode, which oscillates mainly along the equatorial plane. A possibility to observe Faraday resonance in gravitational waves is demonstrated and discussed.

  13. Impaired visuomotor adaptation in adults with ADHD.

    Science.gov (United States)

    Kurdziel, Laura B F; Dempsey, Katherine; Zahara, Mackenzie; Valera, Eve; Spencer, Rebecca M C

    2015-04-01

    Attention-deficit hyperactivity disorder (ADHD) is a prevalent psychiatric disorder in children that often continues into adulthood. It has been suggested that motor impairments in ADHD are associated with underlying cerebellar pathology. If such is the case, individuals with ADHD should be impaired on motor tasks requiring healthy cerebellar function. To test this, we compared performance of individuals with ADHD and ADHD-like symptoms with non-ADHD controls on a visuomotor adaptation task known to be impaired following cerebellar lesions. Participants adapted reaching movements to a visual representation that was rotated by 30°. Individuals with ADHD and those with ADHD-like symptoms took longer to correct the angle of movement once the rotation was applied relative to controls. However, post-adaptation residual effect did not differ for individuals with ADHD and ADHD-like symptoms compared to the control group. These results are consistent with the hypothesis that mild cerebellar deficits are evident in the motor performance of adults with ADHD.

  14. Studying rotational dynamics with a smartphone—accelerometer versus gyroscope

    Science.gov (United States)

    Braskén, Mats; Pörn, Ray

    2017-07-01

    The wide-spread availability of smartphones makes them a valuable addition to the measurement equipment of both the physics classroom and the instructional physics laboratory, encouraging an active interaction between measurements and modeling activities. Two useful sensors, available in most modern smartphones and tablets, are the 3-axis acceleration sensor and the 3-axis gyroscope. We explore the strengths and weaknesses of each type of sensor and use them to study the rotational dynamics of objects rotating about a fixed axis. Care has to be taken when interpreting acceleration sensor data, and in some cases the gyroscope will allow for rotational measurements not easily replicated using the acceleration sensor.

  15. Rotational dynamics of simple asymmetric molecules

    Science.gov (United States)

    Fragiadakis, D.; Roland, C. M.

    2015-02-01

    Molecular dynamic simulations were carried out on rigid diatomic molecules, which exhibit both α (structural) and β (secondary) dynamics. The relaxation scenarios range from onset behavior, in which a distinct α process emerges on cooling, to merging behavior, associated with two relaxation peaks that converge at higher temperature. These properties, as well as the manifestation of the β peak as an excess wing, depend not only on thermodynamic conditions, but also on both the symmetry of the molecule and the correlation function (odd or even) used to analyze its dynamics. These observations help to reconcile divergent results obtained from different experiments. For example, the β process is more intense and the α-relaxation peak is narrower in dielectric relaxation spectra than in dynamic light scattering or NMR measurements. In the simulations herein, this follows from the weaker contribution of the secondary relaxation to even-order correlation functions, related to the magnitude of the relevant angular jumps.

  16. The dynamics of a rotating ellipsoid

    CERN Document Server

    Martins, Laysa G

    2013-01-01

    An interesting physical phenomenon, which contradicts our common sense, is concerned with the dynamics of motion of a spinning ellipsoid in a non smooth surface. A hard-boiled egg spinning on a table with a rough surface is an example. In this article, we present a theoretical explanation, of the dynamics of motion of this ellipsoid, that describes the axis raising phenomenon, from the horizontal to the vertical. The equations of motion were obtained with Lagrangian formalism.

  17. The impact of augmented information on visuo-motor adaptation in younger and older adults.

    Directory of Open Access Journals (Sweden)

    Mathias Hegele

    Full Text Available BACKGROUND: Adjustment to a visuo-motor rotation is known to be affected by ageing. According to previous studies, the age-related differences primarily pertain to the use of strategic corrections and the generation of explicit knowledge on which strategic corrections are based, whereas the acquisition of an (implicit internal model of the novel visuo-motor transformation is unaffected. The present study aimed to assess the impact of augmented information on the age-related variation of visuo-motor adjustments. METHODOLOGY/PRINCIPAL FINDINGS: Participants performed aiming movements controlling a cursor on a computer screen. Visual feedback of direction of cursor motion was rotated 75 degrees relative to the direction of hand motion. Participants had to adjust to this rotation in the presence and absence of an additional hand-movement target that explicitly depicted the input-output relations of the visuo-motor transformation. An extensive set of tests was employed in order to disentangle the contributions of different processes to visuo-motor adjustment. Results show that the augmented information failed to affect the age-related variations of explicit knowledge, adaptive shifts, and aftereffects in a substantial way, whereas it clearly affected initial direction errors during practice and proprioceptive realignment. CONCLUSIONS: Contrary to expectations, older participants apparently made no use of the augmented information, whereas younger participants used the additional movement target to reduce initial direction errors early during practice. However, after a first block of trials errors increased, indicating a neglect of the augmented information, and only slowly declined thereafter. A hypothetical dual-task account of these findings is discussed. The use of the augmented information also led to a selective impairment of proprioceptive realignment in the younger group. The mere finding of proprioceptive realignment in adaptation to a visuo-motor

  18. Estimation of the Rotational Terms of the Dynamic Response Matrix

    Directory of Open Access Journals (Sweden)

    D. Montalvão

    2004-01-01

    Full Text Available The dynamic response of a structure can be described by both its translational and rotational receptances. The latter ones are frequently not considered because of the difficulties in applying a pure moment excitation or in measuring rotations. However, in general, this implies a reduction up to 75% of the complete model. On the other hand, if a modification includes a rotational inertia, the rotational receptances of the unmodified system are needed. In one method, more commonly found in the literature, a so called T-block is attached to the structure. Then, a force, applied to an arm of the T-block, generates a moment together with a force at the connection point. The T-block also allows for angular displacement measurements. Nevertheless, the results are often not quite satisfactory. In this work, an alternative method based upon coupling techniques is developed, in which rotational receptances are estimated without the need of applying a moment excitation. This is accomplished by introducing a rotational inertia modification when rotating the T-block. The force is then applied in its centroid. Several numerical and experimental examples are discussed so that the methodology can be clearly described. The advantages and limitations are identified within the practical application of the method.

  19. Generalization of visuomotor adaptation depends on the spatial characteristic of visual workspace.

    Science.gov (United States)

    Wang, Lei; Müsseler, Jochen

    2012-11-01

    The present study aims to address a novel aspect of visuomotor adaptation and its generalization. It is based on the assumption that the spatial structure of the distal action space is crucial for generalization. In the experiments, the distal action spaces could manifest either a symmetric or parallel structure. The imposed visuomotor rotations in the adaptation and the following generalization were either the same or opposing each other. In the generalization phase, motor bias resulting from prior adaptation was observed, and it turned out to substantially depend on the property of the workspace. In Experiment 1 with a parallel workspace, preceding adaptation to the same rotation was more advantageous than adaptation to an opposing rotation. This observation was reversed in Experiment 2 with the symmetrical workspace: prior adaptation to an opposing rotation was more advantageous for the generalization than prior adaptation to the same rotation. Mechanisms possibly underlying the observed influence of the workspace configuration were discussed.

  20. Abnormal visuomotor processing in schizophrenia

    Directory of Open Access Journals (Sweden)

    Siân E. Robson

    2016-01-01

    Full Text Available Subtle disturbances of visual and motor function are known features of schizophrenia and can greatly impact quality of life; however, few studies investigate these abnormalities using simple visuomotor stimuli. In healthy people, electrophysiological data show that beta band oscillations in sensorimotor cortex decrease during movement execution (event-related beta desynchronisation (ERBD, then increase above baseline for a short time after the movement (post-movement beta rebound (PMBR; whilst in visual cortex, gamma oscillations are increased throughout stimulus presentation. In this study, we used a self-paced visuomotor paradigm and magnetoencephalography (MEG to contrast these responses in patients with schizophrenia and control volunteers. We found significant reductions in the peak-to-peak change in amplitude from ERBD to PMBR in schizophrenia compared with controls. This effect was strongest in patients who made fewer movements, whereas beta was not modulated by movement in controls. There was no significant difference in the amplitude of visual gamma between patients and controls. These data demonstrate that clear abnormalities in basic sensorimotor processing in schizophrenia can be observed using a very simple MEG paradigm.

  1. EEG Theta Dynamics within Frontal and Parietal Cortices for Error Processing during Reaching Movements in a Prism Adaptation Study Altering Visuo-Motor Predictive Planning.

    Science.gov (United States)

    Arrighi, Pieranna; Bonfiglio, Luca; Minichilli, Fabrizio; Cantore, Nicoletta; Carboncini, Maria Chiara; Piccotti, Emily; Rossi, Bruno; Andre, Paolo

    2016-01-01

    Modulation of frontal midline theta (fmθ) is observed during error commission, but little is known about the role of theta oscillations in correcting motor behaviours. We investigate EEG activity of healthy partipants executing a reaching task under variable degrees of prism-induced visuo-motor distortion and visual occlusion of the initial arm trajectory. This task introduces directional errors of different magnitudes. The discrepancy between predicted and actual movement directions (i.e. the error), at the time when visual feedback (hand appearance) became available, elicits a signal that triggers on-line movement correction. Analysis were performed on 25 EEG channels. For each participant, the median value of the angular error of all reaching trials was used to partition the EEG epochs into high- and low-error conditions. We computed event-related spectral perturbations (ERSP) time-locked either to visual feedback or to the onset of movement correction. ERSP time-locked to the onset of visual feedback showed that fmθ increased in the high- but not in the low-error condition with an approximate time lag of 200 ms. Moreover, when single epochs were sorted by the degree of motor error, fmθ started to increase when a certain level of error was exceeded and, then, scaled with error magnitude. When ERSP were time-locked to the onset of movement correction, the fmθ increase anticipated this event with an approximate time lead of 50 ms. During successive trials, an error reduction was observed which was associated with indices of adaptations (i.e., aftereffects) suggesting the need to explore if theta oscillations may facilitate learning. To our knowledge this is the first study where the EEG signal recorded during reaching movements was time-locked to the onset of the error visual feedback. This allowed us to conclude that theta oscillations putatively generated by anterior cingulate cortex activation are implicated in error processing in semi-naturalistic motor

  2. Unified rotational dynamics of molecular crystals with orientational phase transition

    NARCIS (Netherlands)

    Michel, K.H.; Raedt, H. De

    1976-01-01

    A unified theory for the rotational dynamics of molecular crystals with orientational phase transitions is given. As basic secular variables one takes symmetry adapted functions, which describe the molecular orientations, and the angular momenta of the molecules. Using Mori’s projection operator tec

  3. Dynamical quorum sensing and clustering dynamics in a population of spatially distributed active rotators

    Science.gov (United States)

    Sakaguchi, Hidetsugu; Maeyama, Satomi

    2013-02-01

    A model of clustering dynamics is proposed for a population of spatially distributed active rotators. A transition from excitable to oscillatory dynamics is induced by the increase of the local density of active rotators. It is interpreted as dynamical quorum sensing. In the oscillation regime, phase waves propagate without decay, which generates an effectively long-range interaction in the clustering dynamics. The clustering process becomes facilitated and only one dominant cluster appears rapidly as a result of the dynamical quorum sensing. An exact localized solution is found to a simplified model equation, and the competitive dynamics between two localized states is studied numerically.

  4. Dynamics of ferromagnetic nanowires in a rotating magnetic field

    Directory of Open Access Journals (Sweden)

    Lixin Yang

    2015-07-01

    Full Text Available Manipulating nanowires with external magnetic fields has emerged as a powerful tool in various engineering applications, which prompts an urgent need to better understand the dynamics of nanowire rotation under different control conditions. In this article, the motion of ferromagnetic nickel (Ni nanowires under a rotating magnetic field was investigated both theoretically and experimentally. The synchronous and asynchronous rotations were characterized in detail. Analytical models were developed for the major modes of motion by solving the governing equations of rotation. Particularly, a selection of theoretical formula for fluid viscous torque on nanowires of large aspect ratios was made based on the computational fluid dynamics simulation results. The comparisons of the theoretical prediction and the experimental data showed very good agreement. The effects of various system variables, such as the strength and rotating frequency of the magnetic field and the nanowire aspect ratio, were examined. Hence, the insights gained from this work can be applied to future exploration of magnetic manipulation of nanowires.

  5. Dynamics of a bacterial flagellum under reverse rotation

    CERN Document Server

    Adhyapak, Tapan Chandra

    2016-01-01

    To initiate tumbling of an E. coli, one of the helical flagella reverses its sense of rotation. It then transforms from its normal form first to the transient semicoiled state and subsequently to the curly-I state. The dynamics of polymorphism is effectively modeled by describing flagellar elasticity through an extended Kirchhoff free energy. However, the complete landscape of the free energy remains undetermined because the ground state energies of the polymorphic forms are not known. We investigate how variations in these ground state energies affect the dynamics of a reversely rotated flagellum of a swimming bacterium. We find that the flagellum exhibits a number of distinct dynamical states and comprehensively summarize them in a state diagram. As a result, we conclude that tuning the landscape of the extended Kirchhoff free energy alone cannot generate the intermediate full-length semicoiled state. However, our model suggests an ad hoc method to realize the sequence of polymorphic states as observed for ...

  6. Translational and rotational dynamic analysis of a superconducting levitation system

    Science.gov (United States)

    Cansiz, A.; Hull, J. R.; Gundogdu, Ö.

    2005-07-01

    The rotational dynamics of a disc-shaped permanent magnet rotor levitated over a high temperature superconductor was studied experimentally and theoretically. The interaction between the rotor magnet and the superconductor was modelled by assuming the magnet to be a magnetic dipole and the superconductor a diamagnet. In the magnetomechanical analysis of the superconductor part, the frozen image concept was combined with the diamagnetic image, and the damping in the system was neglected. The interaction potential of the system is the combination of magnetic and gravitational potentials. From the dynamical analysis the equations of motion of the permanent magnet were stated as a function of lateral, vertical, tilt, precision and rotating angles. The vibration behaviour and correlation of the vibration of one direction with that of another were determined with a numerical calculation based on the Runge-Kutta method. The various vibrational frequencies identified were vertical, radial, tilt, precession and rotation. The tests performed for experimental verifications were translational and rotational. The permanent magnet was 'spun up' under vacuum conditions to analyse the dynamics of the free 'spin down' behaviour of the permanent magnet.

  7. Nonlinear dynamics of rotating shallow water methods and advances

    CERN Document Server

    Zeitlin, Vladimir

    2007-01-01

    The rotating shallow water (RSW) model is of wide use as a conceptual tool in geophysical fluid dynamics (GFD), because, in spite of its simplicity, it contains all essential ingredients of atmosphere and ocean dynamics at the synoptic scale, especially in its two- (or multi-) layer version. The book describes recent advances in understanding (in the framework of RSW and related models) of some fundamental GFD problems, such as existence of the slow manifold, dynamical splitting of fast (inertia-gravity waves) and slow (vortices, Rossby waves) motions, nonlinear geostrophic adjustment and wa

  8. EEG Theta Dynamics within Frontal and Parietal Cortices for Error Processing during Reaching Movements in a Prism Adaptation Study Altering Visuo-Motor Predictive Planning.

    Directory of Open Access Journals (Sweden)

    Pieranna Arrighi

    Full Text Available Modulation of frontal midline theta (fmθ is observed during error commission, but little is known about the role of theta oscillations in correcting motor behaviours. We investigate EEG activity of healthy partipants executing a reaching task under variable degrees of prism-induced visuo-motor distortion and visual occlusion of the initial arm trajectory. This task introduces directional errors of different magnitudes. The discrepancy between predicted and actual movement directions (i.e. the error, at the time when visual feedback (hand appearance became available, elicits a signal that triggers on-line movement correction. Analysis were performed on 25 EEG channels. For each participant, the median value of the angular error of all reaching trials was used to partition the EEG epochs into high- and low-error conditions. We computed event-related spectral perturbations (ERSP time-locked either to visual feedback or to the onset of movement correction. ERSP time-locked to the onset of visual feedback showed that fmθ increased in the high- but not in the low-error condition with an approximate time lag of 200 ms. Moreover, when single epochs were sorted by the degree of motor error, fmθ started to increase when a certain level of error was exceeded and, then, scaled with error magnitude. When ERSP were time-locked to the onset of movement correction, the fmθ increase anticipated this event with an approximate time lead of 50 ms. During successive trials, an error reduction was observed which was associated with indices of adaptations (i.e., aftereffects suggesting the need to explore if theta oscillations may facilitate learning. To our knowledge this is the first study where the EEG signal recorded during reaching movements was time-locked to the onset of the error visual feedback. This allowed us to conclude that theta oscillations putatively generated by anterior cingulate cortex activation are implicated in error processing in semi

  9. The rotational dynamics of Titan from Cassini RADAR images

    Science.gov (United States)

    Meriggiola, Rachele; Iess, Luciano; Stiles, Bryan. W.; Lunine, Jonathan. I.; Mitri, Giuseppe

    2016-09-01

    Between 2004 and 2009 the RADAR instrument of the Cassini mission provided 31 SAR images of Titan. We tracked the position of 160 surface landmarks as a function of time in order to monitor the rotational dynamics of Titan. We generated and processed RADAR observables using a least squares fit to determine the updated values of the rotational parameters. We provide a new rotational model of Titan, which includes updated values for spin pole location, spin rate, precession and nutation terms. The estimated pole location is compatible with the occupancy of a Cassini state 1. We found a synchronous value of the spin rate (22.57693 deg/day), compatible at a 3-σ level with IAU predictions. The estimated obliquity is equal to 0.31°, incompatible with the assumption of a rigid body with fully-damped pole and a moment of inertia factor of 0.34, as determined by gravity measurements.

  10. Real-time error detection but not error correction drives automatic visuomotor adaptation.

    Science.gov (United States)

    Hinder, Mark R; Riek, Stephan; Tresilian, James R; de Rugy, Aymar; Carson, Richard G

    2010-03-01

    We investigated the role of visual feedback of task performance in visuomotor adaptation. Participants produced novel two degrees of freedom movements (elbow flexion-extension, forearm pronation-supination) to move a cursor towards visual targets. Following trials with no rotation, participants were exposed to a 60 degrees visuomotor rotation, before returning to the non-rotated condition. A colour cue on each trial permitted identification of the rotated/non-rotated contexts. Participants could not see their arm but received continuous and concurrent visual feedback (CF) of a cursor representing limb position or post-trial visual feedback (PF) representing the movement trajectory. Separate groups of participants who received CF were instructed that online modifications of their movements either were, or were not, permissible as a means of improving performance. Feedforward-mediated performance improvements occurred for both CF and PF groups in the rotated environment. Furthermore, for CF participants this adaptation occurred regardless of whether feedback modifications of motor commands were permissible. Upon re-exposure to the non-rotated environment participants in the CF, but not PF, groups exhibited post-training aftereffects, manifested as greater angular deviations from a straight initial trajectory, with respect to the pre-rotation trials. Accordingly, the nature of the performance improvements that occurred was dependent upon the timing of the visual feedback of task performance. Continuous visual feedback of task performance during task execution appears critical in realising automatic visuomotor adaptation through a recalibration of the visuomotor mapping that transforms visual inputs into appropriate motor commands.

  11. Playing Action Video Games Improves Visuomotor Control.

    Science.gov (United States)

    Li, Li; Chen, Rongrong; Chen, Jing

    2016-08-01

    Can playing action video games improve visuomotor control? If so, can these games be used in training people to perform daily visuomotor-control tasks, such as driving? We found that action gamers have better lane-keeping and visuomotor-control skills than do non-action gamers. We then trained non-action gamers with action or nonaction video games. After they played a driving or first-person-shooter video game for 5 or 10 hr, their visuomotor control improved significantly. In contrast, non-action gamers showed no such improvement after they played a nonaction video game. Our model-driven analysis revealed that although different action video games have different effects on the sensorimotor system underlying visuomotor control, action gaming in general improves the responsiveness of the sensorimotor system to input error signals. The findings support a causal link between action gaming (for as little as 5 hr) and enhancement in visuomotor control, and suggest that action video games can be beneficial training tools for driving.

  12. DYNAMIC SIMULATION OF ROTATING SHELLS COUPLED WITH LIQUID

    Institute of Scientific and Technical Information of China (English)

    Wei Fayuan; Li Shiqi; Zhong Yifang; Huang Yuying

    2001-01-01

    The dynamic behaviors of rotating shells coupled with liquid are shown. The shell under consideration has arbitrary boundary conditions and a complex shape. A modified boundary element method and finite strip technique are used to improve the computing efficiency and to guarantee the continuity conditions on the liquid-shell interaction plane. The effects of various parameters such as shell's thickness and liquid depth are investigated. Dynamic simulations are applied to several typical shell-liquid systems, and the natural frequencies, mode shapes and response of vibration are calculated numerically.

  13. Dynamics of immiscible liquids in a rotating horizontal cylinder

    Science.gov (United States)

    Kozlov, N. V.; Kozlova, A. N.; Shuvalova, D. A.

    2016-11-01

    The dynamics of an interface between two immiscible liquids of different density is studied experimentally in a horizontal cylinder at rotation in the gravity field. Two liquids entirely fill the cavity volume, and the container is rotated sufficiently fast so that the liquids are centrifuged. The light liquid forms a column extended along the rotation axis, and the heavy liquid forms an annular layer. Under the action of gravity, the light liquid column displaces steadily along the radius, downwards in the laboratory frame. As a result, fluid oscillations in the cavity frame are excited at the interface, which lead to the generation of a steady streaming, and the fluid comes into a slow lagging rotation with respect to the cylinder walls. The dynamics of the studied system is determined by the ratio of the gravity acceleration to the centrifugal one—the dimensionless acceleration. In experiments, the system is controlled by the means of variation of the rotation rate, i.e., of the centrifugal force. At a critical value of the dimensionless acceleration the circular interface looses stability, and an azimuthal wave is excited. This leads to a strong increase in the interface differential velocity. A theoretical analysis is done based on the theory of centrifugal waves and a frequency equation is obtained. Experimental results are in good agreement with the theory at the condition of small wave amplitudes. Mechanism of steady streaming generation is analyzed based on previously published theoretical results obtained for the limiting case when the light phase is a solid cylinder. A qualitative agreement is found.

  14. Rotational coherence spectroscopy at FLASH. Toward dynamic studies in nanosuperfluids

    Energy Technology Data Exchange (ETDEWEB)

    Kickermann, Andreas

    2013-07-15

    The field of molecular physics, which is focusing on molecular motion in the transition states of physical, chemical, and biological changes, is a wide-spread research area. It strives to reveal the structural and functional properties of molecules, the chemical bonds between atoms and the time evolution. Many processes occurring in nature upon electronic excitation proceed on the ultrafast femtosecond timescale and can be triggered by modern ultrashort femtosecond-laser sources under laboratory conditions. In the present thesis pump-probe studies were performed to follow molecular motion using ultrashort light pulses in the nanometer wavelength range provided by an XUV freeelectron laser (FEL). In detail, alignment of molecular species in space under field-free conditions was investigated. In the specific case of rotational wave packets in molecules the rotational dynamics shows characteristic temporal features, which contain a wealth of information on molecular structure and give insight into molecular coupling mechanisms, i.e. rotational constants and transition frequencies. Within this thesis, Rotational Coherence Spectroscopy (RCS) reveals wave-packet motion observed by subsequent Coulomb explosion of Raman excited carbon monoxide, which results in a time-dependent asymmetry of spatial fragmentation patterns. With the method presented here, the time resolution to elucidate the fast dynamics of strong couplings can be pushed toward a single rotational period even for the fastest rotors. This is due to large pump-probe delays with small subpicosecond step size. This kind of spectroscopy can also be expanded to molecular species, which are not accessible by other powerful spectroscopic methods, such as Fourier-transform microwave spectroscopy (FTMW). Furthermore, it allows to measure weak molecular couplings on a long timescale (large pump-probe delays), e.g. couplings of molecules in a solution or molecules dissolved in quantum fluids. This is valuable to

  15. A Simple and Efficient Numerical Method for Computing the Dynamics of Rotating Bose--Einstein Condensates via Rotating Lagrangian Coordinates

    KAUST Repository

    Bao, Weizhu

    2013-01-01

    We propose a simple, efficient, and accurate numerical method for simulating the dynamics of rotating Bose-Einstein condensates (BECs) in a rotational frame with or without longrange dipole-dipole interaction (DDI). We begin with the three-dimensional (3D) Gross-Pitaevskii equation (GPE) with an angular momentum rotation term and/or long-range DDI, state the twodimensional (2D) GPE obtained from the 3D GPE via dimension reduction under anisotropic external potential, and review some dynamical laws related to the 2D and 3D GPEs. By introducing a rotating Lagrangian coordinate system, the original GPEs are reformulated to GPEs without the angular momentum rotation, which is replaced by a time-dependent potential in the new coordinate system. We then cast the conserved quantities and dynamical laws in the new rotating Lagrangian coordinates. Based on the new formulation of the GPE for rotating BECs in the rotating Lagrangian coordinates, a time-splitting spectral method is presented for computing the dynamics of rotating BECs. The new numerical method is explicit, simple to implement, unconditionally stable, and very efficient in computation. It is spectral-order accurate in space and second-order accurate in time and conserves the mass on the discrete level. We compare our method with some representative methods in the literature to demonstrate its efficiency and accuracy. In addition, the numerical method is applied to test the dynamical laws of rotating BECs such as the dynamics of condensate width, angular momentum expectation, and center of mass, and to investigate numerically the dynamics and interaction of quantized vortex lattices in rotating BECs without or with the long-range DDI.Copyright © by SIAM.

  16. Dynamical Tidal Response of a Rotating Neutron Star

    Science.gov (United States)

    Landry, Philippe; Poisson, Eric

    2017-01-01

    The gravitational wave phase of a neutron star (NS) binary is sensitive to the deformation of the NS that results from its companion's tidal influence. In a perturbative treatment, the tidal deformation can be characterized by a set of dimensionless constants, called Love numbers, which depend on the NS equation of state. For static NSs, one type of Love number encodes the response to gravitoelectric tidal fields (associated with mass multipole moments), while another does likewise for gravitomagnetic fields (associated with mass currents). A NS subject to a gravitomagnetic tidal field develops internal fluid motions through gravitomagnetic induction; the fluid motions are irrotational, provided the star is non-rotating. When the NS is allowed to rotate, the situation is complicated by couplings between the tidal field and the star's spin. The problem becomes tractable in the slow-rotation limit. In this case, the fluid motions induced by an external gravitomagnetic field are fully dynamical, even if the tidal field is stationary: interior metric and fluid variables are time-dependent, and vary on the timescale of the rotation period. Remarkably, the exterior geometry of the NS remains time-independent.

  17. Visuomotor control of neck surface electromyography in Parkinson’s disease

    Science.gov (United States)

    Malloy, Jessica R.; Valentin, Juliana C.; Hands, Gabrielle L.; Stevens, Christina A.; Langmore, Susan E.; Noordzij, J. Pieter; Stepp, Cara E.

    2015-01-01

    OBJECTIVE To compare performance of individuals with Parkinson’s disease (PD) and age-matched controls on a visuomotor tracking task controlled via surface electromyography (sEMG). METHODS Twenty-seven adults with PD and twenty-four older controls produced dry swallows and completed a visuomotor tracking task utilizing both static and dynamic targets. sEMG was recorded at the anterior neck and submental surface during both tasks. RESULTS There was no significant difference in visuomotor tracking ability between cohorts. Post hoc analyses indicated that there was no significant difference between participant groups in the strength or duration of swallows as measured by sEMG but that participants with PD showed a trend for decreased swallow durations at the anterior neck (padj=0.067) whereas controls showed a trend for increased durations at the anterior neck (padj=0.112), compared to the submental surface. However, there were no significant correlations between swallowing behavior and visuomotor tracking ability. CONCLUSION There were no significant differences in visuomotor tracking performance between individuals with PD and controls. Furthermore, there was no relationship between tracking ability and swallowing behavior. We conclude that sEMG-mediated biofeedback may have limited promise as a tool for treating PD-related dysphagia. PMID:25318778

  18. Rotational and frictional dynamics of the slamming of a door

    Science.gov (United States)

    Klein, Pascal; Müller, Andreas; Gröber, Sebastian; Molz, Alexander; Kuhn, Jochen

    2017-01-01

    A theoretical and experimental investigation of the rotational dynamics, including friction, of a slamming door is presented. Based on existing work regarding different damping models for rotational and oscillatory motions, we examine different forms for the (angular) velocity dependence (ωn, n = 0, 1, 2) of the frictional force. An analytic solution is given when all three friction terms are present and several solutions for specific cases known from the literature are reproduced. The motion of a door is investigated experimentally using a smartphone, and the data are compared with the theoretical results. A laboratory experiment under more controlled conditions is conducted to gain a deeper understanding of the movement of a slammed door. Our findings provide quantitative evidence that damping models involving quadratic air drag are most appropriate for the slamming of a door. Examining this everyday example of a physical phenomenon increases student motivation, because they can relate it to their own personal experience.

  19. The dynamic rotation of Langer's lines on facial expression.

    Science.gov (United States)

    Bush, James; Ferguson, Mark W J; Mason, Tracey; McGrouther, Gus

    2007-01-01

    Karl Langer investigated directional variations in the mechanical and physical properties of skin [Gibson T. Editorial. Karl Langer (1819-1887) and his lines. Br J Plast Surg 1978;31:1-2]. He produced a series of diagrams depicting lines of cleavage in the skin [Langer K. On the anatomy and physiology of the skin I. The cleavability of the cutis. Br J Plast Surg 1978;31:3-8] and showed that the orientation of these lines coincided with the dominant axis of mechanical tension in the skin [Langer K. On the anatomy and physiology of the skin II. Skin tension. Br J Plast Surg 1978;31:93-106]. Previously these lines have been considered as a static feature. We set out to determine whether Langer's lines have a dynamic element and to define any rotation of the orientation of Langer's lines on the face with facial movement. One hundred and seventy-five naevi were excised from the face and neck of 72 volunteers using circular dermal punch biopsies. Prior to surgery a vertical line was marked on the skin through the centre of each naevus. After excision distortions of the resulting wounds were observed. The orientation of the long axis of each wound, in relation to the previously marked vertical line, was measured with a goniometer with the volunteer at rest and holding their face in five standardised facial expressions: mouth open, smiling, eyes tightly shut, frowning and eyebrows raised. The aim was to measure the orientation of the long axis of the wound with the face at rest and subsequent rotation of the wound with facial movement. After excision elliptical distortion was seen in 171 of the 175 wounds at rest. Twenty-nine wounds maintained the same orientation of distortion in all of the facial expressions. In the remaining wounds the long axis of the wound rotated by up to 90 degrees . The amount of rotation varied between sites (p>0.0001). We conclude that Langer's lines are not a static feature but are dynamic with rotation of up to 90 degrees . It is possible that

  20. Neural Correlates of Visuomotor Learning in Autism.

    Science.gov (United States)

    Sharer, Elizabeth; Crocetti, Deana; Muschelli, John; Barber, Anita D; Nebel, Mary Beth; Caffo, Brian S; Pekar, Jim J; Mostofsky, Stewart H

    2015-12-01

    Motor impairments are prevalent in children with autism spectrum disorder. The Serial Reaction Time Task, a well-established visuomotor sequence learning probe, has produced inconsistent behavioral findings in individuals with autism. Moreover, it remains unclear how underlying neural processes for visuomotor learning in children with autism compare to processes for typically developing children. Neural activity differences were assessed using functional magnetic resonance imaging during a modified version of the Serial Reaction Time Task in children with and without autism. Though there was no group difference in visuomotor sequence learning, underlying patterns of neural activation significantly differed when comparing sequence (i.e., learning) to random (i.e., nonlearning) blocks. Children with autism demonstrated decreased activity in brain regions implicated in visuomotor sequence learning: superior temporal sulcus and posterior cingulate cortex. The findings implicate differences in brain mechanisms that support initial sequence learning in autism and can help explain behavioral observations of autism-associated impairments in skill development (motor, social, communicative) reliant on visuomotor integration.

  1. Vibration-rotation-tunneling dynamics in small water clusters

    Energy Technology Data Exchange (ETDEWEB)

    Pugliano, N.

    1992-11-01

    The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm{sup {minus}1} intermolecular vibration of the water dimer-d{sub 4}. Each of the VRT subbands originate from K{sub a}{double_prime}=0 and terminate in either K{sub a}{prime}=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A{prime} rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K{sub a}{prime} quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a{prime} symmetry, and the vibration is assigned as the {nu}{sub 12} acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D{sub 2}O-DOH isotopomer.

  2. Vibration-rotation-tunneling dynamics in small water clusters

    Energy Technology Data Exchange (ETDEWEB)

    Pugliano, N.

    1992-11-01

    The goal of this work is to characterize the intermolecular vibrations of small water clusters. Using tunable far infrared laser absorption spectroscopy, large amplitude vibration-rotation-tunneling (VRT) dynamics in vibrationally excited states of the water dimer and the water trimer are investigated. This study begins with the measurement of 12 VRT subbands, consisting of approximately 230 transitions, which are assigned to an 82.6 cm[sup [minus]1] intermolecular vibration of the water dimer-d[sub 4]. Each of the VRT subbands originate from K[sub a][double prime]=0 and terminate in either K[sub a][prime]=0 or 1. These data provide a complete characterization of the tunneling dynamics in the vibrationally excited state as well as definitive symmetry labels for all VRT energy levels. Furthermore, an accurate value for the A[prime] rotational constant is found to agree well with its corresponding ground state value. All other excited state rotational constants are fitted, and discussed in terms of the corresponding ground state constants. In this vibration, the quantum tunneling motions are determined to exhibit large dependencies with both the K[sub a][prime] quantum number and the vibrational coordinate, as is evidenced by the measured tunneling splittings. The generalized internal-axis-method treatment which has been developed to model the tunneling dynamics, is considered for the qualitative description of each tunneling pathway, however, the variation of tunneling splittings with vibrational excitation indicate that the high barrier approximation does not appear to be applicable for this vibrational coordinate. The data are consistent with a motion possessing a[prime] symmetry, and the vibration is assigned as the [nu][sub 12] acceptor bending coordinate. This assignment is in agreement with the vibrational symmetry, the resultsof high level ab initio calculations, and preliminary data assigned to the analogous vibration in the D[sub 2]O-DOH isotopomer.

  3. Visuomotor resonance in autism spectrum disorders

    Directory of Open Access Journals (Sweden)

    Cristina eBecchio

    2012-11-01

    Full Text Available When we observe the actions performed by others, our motor system ‘resonates' along with that of the observed agent. Is a similar visuomotor resonant response observed in autism spectrum disorders (ASD? Studies investigating action observation in ASD have yielded inconsistent findings. In this perspective article we examine behavioral and neuroscientific evidence in favor of visuomotor resonance in ASD, and consider the possible role of action-perception coupling in social cognition. We distinguish between different aspects of visuomotor resonance and conclude that while some aspects may be preserved in ASD, abnormalities exist in the way individuals with ASD convert visual information from observed actions into a program for motor execution. Such abnormalities, we surmise, may contribute to but also depend on the difficulties that individuals with ASD encounter during social interaction.

  4. Dynamics of rotationally fissioned asteroids: non-planar case

    Science.gov (United States)

    Boldrin, L. A. G.; Scheeres, D. J.; Winter, O. C.

    2016-10-01

    The rotational fission of asteroids has been studied previously with simplified models restricted to planar motion. However, the observed physical configuration of contact binaries leads one to conclude that most of them are not in a planar configuration and hence would not be restricted to planar motion once they undergo rotational fission. This motivated a study of the evolution of initially non-planar binaries created by fission. Using a two-ellipsoid model, we performed simulations taking only gravitational interactions between components into account. We simulate 91 different initial inclinations of the equator of the secondary body for 19 different mass ratios. After disruption, the binary system dynamics are chaotic, as predicted from theory. Starting the system in a non-planar configuration leads to a larger energy and enhanced coupling between the rotation state of the smaller fissioned body and the evolving orbital system, and enables re-impact to occur. This leads to differences with previous planar studies, with collisions and secondary spin fission occurring for all mass ratios with inclinations θ0 ≥ 40o, and mimics a Lidov-Kozai mechanism. Out of 1729 studied cases, we found that ˜14 per cent result in secondary fission, ˜25 per cent result in collisions and ˜6 per cent have lifetimes longer than 200 yr. In Jacobson & Scheeres stable binaries only formed in cases with mass ratios q system should start in a non-planar configuration.

  5. Dynamics of resonant magnetic field penetration and plasma rotation

    Science.gov (United States)

    Ivanov, N. V.; Kakurin, A. M.

    2017-01-01

    Results of calculations and analysis of the penetration of resonant magnetic perturbations (RMP) into tokamak plasma are presented. The TEAR code used for the calculations is based on a two-fluid magnetohydrodynamics approximation that gives coupled diffusion-type equations for the magnetic flux perturbation and for plasma rotation velocities in toroidal and poloidal directions. The radial distribution of the magnetic flux perturbation is calculated taking account of an externally applied RMP and magnetic perturbation generated by an eddy current in the resistive-vacuum vessel. The decoupling of magnetic-island velocity from the velocity of plasma rotation is employed in the calculations according to available experimental evidence and corresponding theoretical understanding. The account of this decoupling, as well as of plasma rotation in the poloidal direction in addition to the toroidal one, reduces the RMP penetration threshold and accelerates the penetration process. The main attention is paid to the dependences of the RMP penetration dynamics on the simulation conditions. The simulation findings are compared with available experimental data. Some predictions of the penetration threshold values for ITER conditions are presented.

  6. Nanoparticles at liquid interfaces: Rotational dynamics and angular locking

    Energy Technology Data Exchange (ETDEWEB)

    Razavi, Sepideh; Kretzschmar, Ilona [Department of Chemical Engineering, City College of City University of New York, New York, New York 10031 (United States); Koplik, Joel [Department of Physics and The Benjamin Levich Institute for Physico-chemical Hydrodynamics, City College of City University of New York, New York, New York 10031 (United States); Colosqui, Carlos E., E-mail: carlos.colosqui@stonybrook.edu [Department of Mechanical Engineering, Stony Brook University, Stony Brook, New York 11794 (United States)

    2014-01-07

    Nanoparticles with different surface morphologies that straddle the interface between two immiscible liquids are studied via molecular dynamics simulations. The methodology employed allows us to compute the interfacial free energy at different angular orientations of the nanoparticle. Due to their atomistic nature, the studied nanoparticles present both microscale and macroscale geometrical features and cannot be accurately modeled as a perfectly smooth body (e.g., spheres and cylinders). Under certain physical conditions, microscale features can produce free energy barriers that are much larger than the thermal energy of the surrounding media. The presence of these energy barriers can effectively “lock” the particle at specific angular orientations with respect to the liquid-liquid interface. This work provides new insights on the rotational dynamics of Brownian particles at liquid interfaces and suggests possible strategies to exploit the effects of microscale features with given geometric characteristics.

  7. Nanoparticles at liquid interfaces: rotational dynamics and angular locking.

    Science.gov (United States)

    Razavi, Sepideh; Kretzschmar, Ilona; Koplik, Joel; Colosqui, Carlos E

    2014-01-07

    Nanoparticles with different surface morphologies that straddle the interface between two immiscible liquids are studied via molecular dynamics simulations. The methodology employed allows us to compute the interfacial free energy at different angular orientations of the nanoparticle. Due to their atomistic nature, the studied nanoparticles present both microscale and macroscale geometrical features and cannot be accurately modeled as a perfectly smooth body (e.g., spheres and cylinders). Under certain physical conditions, microscale features can produce free energy barriers that are much larger than the thermal energy of the surrounding media. The presence of these energy barriers can effectively "lock" the particle at specific angular orientations with respect to the liquid-liquid interface. This work provides new insights on the rotational dynamics of Brownian particles at liquid interfaces and suggests possible strategies to exploit the effects of microscale features with given geometric characteristics.

  8. Simple Models for the Dynamic Modeling of Rotating Tires

    Directory of Open Access Journals (Sweden)

    J.C. Delamotte

    2008-01-01

    Full Text Available Large Finite Element (FE models of tires are currently used to predict low frequency behavior and to obtain dynamic model coefficients used in multi-body models for riding and comfort. However, to predict higher frequency behavior, which may explain irregular wear, critical rotating speeds and noise radiation, FE models are not practical. Detailed FE models are not adequate for optimization and uncertainty predictions either, as in such applications the dynamic solution must be computed a number of times. Therefore, there is a need for simpler models that can capture the physics of the tire and be used to compute the dynamic response with a low computational cost. In this paper, the spectral (or continuous element approach is used to derive such a model. A circular beam spectral element that takes into account the string effect is derived, and a method to simulate the response to a rotating force is implemented in the frequency domain. The behavior of a circular ring under different internal pressures is investigated using modal and frequency/wavenumber representations. Experimental results obtained with a real untreaded truck tire are presented and qualitatively compared with the simple model predictions with good agreement. No attempt is made to obtain equivalent parameters for the simple model from the real tire results. On the other hand, the simple model fails to represent the correct variation of the quotient of the natural frequency by the number of circumferential wavelengths with the mode count. Nevertheless, some important features of the real tire dynamic behavior, such as the generation of standing waves and part of the frequency/wavenumber behavior, can be investigated using the proposed simplified model.

  9. Visuomotor adaptation in head-mounted virtual reality versus conventional training

    Science.gov (United States)

    Anglin, J. M.; Sugiyama, T.; Liew, S.-L.

    2017-01-01

    Immersive, head-mounted virtual reality (HMD-VR) provides a unique opportunity to understand how changes in sensory environments affect motor learning. However, potential differences in mechanisms of motor learning and adaptation in HMD-VR versus a conventional training (CT) environment have not been extensively explored. Here, we investigated whether adaptation on a visuomotor rotation task in HMD-VR yields similar adaptation effects in CT and whether these effects are achieved through similar mechanisms. Specifically, recent work has shown that visuomotor adaptation may occur via both an implicit, error-based internal model and a more cognitive, explicit strategic component. We sought to measure both overall adaptation and balance between implicit and explicit mechanisms in HMD-VR versus CT. Twenty-four healthy individuals were placed in either HMD-VR or CT and trained on an identical visuomotor adaptation task that measured both implicit and explicit components. Our results showed that the overall timecourse of adaption was similar in both HMD-VR and CT. However, HMD-VR participants utilized a greater cognitive strategy than CT, while CT participants engaged in greater implicit learning. These results suggest that while both conditions produce similar results in overall adaptation, the mechanisms by which visuomotor adaption occurs in HMD-VR appear to be more reliant on cognitive strategies. PMID:28374808

  10. Compact sensor for measuring nonlinear rotational dynamics of driven magnetic microspheres with biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    McNaughton, Brandon H. [Department of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Applied Physics Program, University of Michigan, Ann Arbor, MI 48109-1040 (United States)], E-mail: bmcnaugh@umich.edu; Kinnunen, Paivo [Applied Physics Program, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Smith, Ron G.; Pei, S.N. [Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Torres-Isea, Ramon [Department of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Kopelman, Raoul [Department of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Applied Physics Program, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055 (United States); Clarke, Roy [Department of Physics, University of Michigan, Ann Arbor, MI 48109-1040 (United States); Applied Physics Program, University of Michigan, Ann Arbor, MI 48109-1040 (United States)

    2009-05-15

    The nonlinear rotation response of a magnetic particle occurs when a driving magnetic field, used to rotate the magnetic particle, exceeds a critical frequency. This type of nonlinear rotational dynamic depends on several physical parameters, such as the rotational drag that the particle experiences. Shifts in this nonlinear rotational frequency offer a dynamic approach for the detection of bacteria, measurement of their growth, their response to chemical agents, and other biomedical applications. Therefore, we have developed a stand-alone prototype device that utilizes an elegant combination of a laser diode and photodiode to monitor particle rotation.

  11. Atypical visuomotor performance in children with PDD

    NARCIS (Netherlands)

    Schlooz, W.A.J.M.; Hulstijn, W.

    2012-01-01

    Children with autism spectrum disorders (ASD) frequently encounter difficulties in visuomotor tasks, which are possibly caused by atypical visuoperceptual processing. This was tested in children (aged 9–12 years) with pervasive developmental disorder (PDD; including PDD-NOS and Asperger syndrome),

  12. Visuomotor Dissociation in Cerebral Scaling of Size

    NARCIS (Netherlands)

    Potgieser, Adriaan R. E.; de Jong, Bauke M.

    2016-01-01

    Estimating size and distance is crucial in effective visuomotor control. The concept of an internal coordinate system implies that visual and motor size parameters are scaled onto a common template. To dissociate perceptual and motor components in such scaling, we performed an fMRI experiment in whi

  13. Visuomotor Dissociation in Cerebral Scaling of Size

    NARCIS (Netherlands)

    Potgieser, Adriaan R. E.; de Jong, Bauke M.

    2016-01-01

    Estimating size and distance is crucial in effective visuomotor control. The concept of an internal coordinate system implies that visual and motor size parameters are scaled onto a common template. To dissociate perceptual and motor components in such scaling, we performed an fMRI experiment in

  14. Atypical visuomotor performance in children with PDD

    NARCIS (Netherlands)

    Schlooz, W.A.J.M.; Hulstijn, W.

    2012-01-01

    Children with autism spectrum disorders (ASD) frequently encounter difficulties in visuomotor tasks, which are possibly caused by atypical visuoperceptual processing. This was tested in children (aged 9–12 years) with pervasive developmental disorder (PDD; including PDD-NOS and Asperger syndrome), a

  15. Rotational dynamics in ammonia borane: Evidence of strong isotope effects

    Energy Technology Data Exchange (ETDEWEB)

    Cantelli, Rosario; Paolone, Annalisa; Palumbo, Oriele; Leardini, F.; Autrey, Thomas; Karkamkar, Abhijeet J.; Luedtke, Avery T.

    2013-12-15

    This work reports anelastic spectroscopy measurements on the partially deuterated (ND3BH3 and NH3BD3) and perdeuterated (ND3BD3) ammonia borane (NH3BH3) compounds. The relaxations previously reported in NH3BH3 are observed in all the samples, and are ascribed to the rotational and torsional dynamics of NH(D)3BH(D)3 complexes. A new thermally activated peak appears at 70 K (for a vibration frequency of 1 kHz) in the spectrum of NH3BD3 and ND3BD3. The peak is practically a single-time Debye process, indicating absence of interaction between the relaxing units, and has a strikingly high intensity. A secondary relaxation process is also detected around 55 K. The anelastic spectrum of the ND3BH3 only displays this less intense process at 55 K. The analysis of the peaks supplies information about the dynamics of the relaxing species, and the obtained results provide indications on the effect of partial and selective deuteration on the hydrogen (deuterium) dynamics.

  16. Dynamic Modeling and Simulation of a Rotational Inverted Pendulum

    Science.gov (United States)

    Duart, J. L.; Montero, B.; Ospina, P. A.; González, E.

    2017-01-01

    This paper presents an alternative way to the dynamic modeling of a rotational inverted pendulum using the classic mechanics known as Euler-Lagrange allows to find motion equations that describe our model. It also has a design of the basic model of the system in SolidWorks software, which based on the material and dimensions of the model provides some physical variables necessary for modeling. In order to verify the theoretical results, It was made a contrast between the solutions obtained by simulation SimMechanics-Matlab and the system of equations Euler-Lagrange, solved through ODE23tb method included in Matlab bookstores for solving equations systems of the type and order obtained. This article comprises a pendulum trajectory analysis by a phase space diagram that allows the identification of stable and unstable regions of the system.

  17. The effects of smooth pursuit adaptation on the gain of visuomotor transmission in monkeys

    Directory of Open Access Journals (Sweden)

    Seiji eOno

    2013-12-01

    Full Text Available Smooth pursuit eye movements are supported by visual-motor systems, where visual motion information is transformed into eye movement commands. Adaptation of the visuomotor systems for smooth pursuit is an important factor to maintain pursuit accuracy and high acuity vision. Short-term adaptation of initial pursuit gain can be produced experimentally using by repeated trials of a step-ramp tracking with two different velocities (double-step paradigm that step-up (10–30 °/s or step-down (20–5 °/s. It is also known that visuomotor gain during smooth pursuit is regulated by a dynamic gain control mechanism by showing that eye velocity evoked by a target perturbation during pursuit increases bidirectionally when ongoing pursuit velocity is higher. However, it remains uncertain how smooth pursuit adaptation alters the gain of visuomotor transmission. Therefore, a single cycle of sinusoidal motion (2.5 Hz, ± 10 °/s was introduced during step-ramp tracking pre- and post-adaptation to determine whether smooth pursuit adaptation affects the perturbation response. The results showed that pursuit adaptation had a significant effect on the perturbation response that was specific to the adapted direction. These results indicate that there might be different visuomotor mechanisms between adaptation and dynamic gain control. Furthermore, smooth pursuit adaptation altered not only the gain of the perturbation response, but also the gain slope (regression curve at different target velocities (5, 10 and 15 °/s. Therefore, pursuit adaptation could affect the dynamic regulation of the visuomotor gain at different pursuit velocities.

  18. Weed populations and crop rotations: exploring dynamics of a structured periodic system

    NARCIS (Netherlands)

    Mertens, S.K.; Bosch, F. van den; Heesterbeek, J.A.P.

    2002-01-01

    The periodic growing of a certain set of crops in a prescribed order, called a crop rotation, is considered to be an important tool for managing weed populations. Nevertheless, the effects of crop rotations on weed population dynamics are not well understood. Explanations for rotation effects on

  19. DYNAMIC ANALYSIS OF A SPATIAL COUPLED TIMOSHENKO ROTATING SHAFT WITH LARGE DISPLACEMENTS

    Institute of Scientific and Technical Information of China (English)

    朱怀亮

    2002-01-01

    The dynamic simulation is presented for an axial moving flexible rotating shafts,which have large rigid motions and small elastic deformation. The effects of the axial inertia,shear deformation, rotating inertia, gyroscopic moment, and dynamic unbalance areconsidered based on the Timoshenko rotating shaft theory. The equations of motion andboundary conditions are derived by Hamilton principle, and the solution is obtained by usingthe perturbation approach and cssuming mode method. This study confirms that the influenceof the axial rigid motion, shear deformation, slenderness ratio and rotating speed on thedynamic behavior of Timoshenko rotating shaft is evident, especially to a high-angularvelocity rotor.

  20. Macroscopic Dynamical Description of Rotating au + au System

    Science.gov (United States)

    Cârjan, N.; Siwek-Wilczyńska, K.; Skwira-Chalot, I.; Wilczyński, J.

    Events with more than two heavy fragments have been abundantly observed in heavy-ion semi-peripheral (fission-like) reaction 197Au+197Au at 15 MeV/nucleon. This raised interesting questions about their origin and about the time-scale at which they occur. As a possible explanation of this process, the surface instability of the cylindrical neck that is formed along the path from contact to reseparation of the rotating Au+Au system is investigated in the present paper. For this purpose the Los Alamos finite-range macroscopic dynamical model was used. The calculations were performed at relatively high angular momenta, L = 100 to 300 ħ, for two types of dissipation mechanisms: two-body viscosity and one-body dissipation. Various initial nuclear deformations and initial kinetic energies in the fission direction were considered. The resulting dynamical evolution in the multidimensional deformation space always led to multifragment scission configurations suggesting that ternary and quaternary break-up can occur during the heavy-ion reaction studied.

  1. Edge localized mode rotation and the nonlinear dynamics of filaments

    Energy Technology Data Exchange (ETDEWEB)

    Morales, J. A.; Bécoulet, M.; Garbet, X.; Dif-Pradalier, G.; Huijsmans, G. T. A.; Fil, A.; Nardon, E.; Passeron, C.; Latu, G. [CEA, IRFM, 13108 St. Paul-Lez-Durance (France); Orain, F.; Hoelzl, M. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany); Pamela, S. [CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB (United Kingdom); Cahyna, P. [Institute of Plasma Physics ASCR, Za Slovankou 1782/3, 182 00 Prague 8 (Czech Republic)

    2016-04-15

    Edge Localized Modes (ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filaments rotation at the ELM crash. Linear ballooning theory is used to establish a formula estimating the rotation velocity of ELM precursors. The linear study together with nonlinear magnetohydrodynamic simulations give an explanation to the rotations observed experimentally. Unstable ballooning modes, localized at the pedestal, grow and rotate in the electron diamagnetic direction in the laboratory reference frame. Approaching the ELM crash, this rotation decreases corresponding to the moment when the magnetic reconnection occurs. During the highly nonlinear ELM crash, the ELM filaments are cut from the main plasma due to the strong sheared mean flow that is nonlinearly generated via the Maxwell stress tensor.

  2. Edge localized mode rotation and the nonlinear dynamics of filaments

    Science.gov (United States)

    Morales, J. A.; Bécoulet, M.; Garbet, X.; Orain, F.; Dif-Pradalier, G.; Hoelzl, M.; Pamela, S.; Huijsmans, G. T. A.; Cahyna, P.; Fil, A.; Nardon, E.; Passeron, C.; Latu, G.

    2016-04-01

    Edge Localized Modes (ELMs) rotating precursors were reported few milliseconds before an ELM crash in several tokamak experiments. Also, the reversal of the filaments rotation at the ELM crash is commonly observed. In this article, we present a mathematical model that reproduces the rotation of the ELM precursors as well as the reversal of the filaments rotation at the ELM crash. Linear ballooning theory is used to establish a formula estimating the rotation velocity of ELM precursors. The linear study together with nonlinear magnetohydrodynamic simulations give an explanation to the rotations observed experimentally. Unstable ballooning modes, localized at the pedestal, grow and rotate in the electron diamagnetic direction in the laboratory reference frame. Approaching the ELM crash, this rotation decreases corresponding to the moment when the magnetic reconnection occurs. During the highly nonlinear ELM crash, the ELM filaments are cut from the main plasma due to the strong sheared mean flow that is nonlinearly generated via the Maxwell stress tensor.

  3. Visuomotor learning enhanced by augmenting instantaneous trajectory error feedback during reaching.

    Directory of Open Access Journals (Sweden)

    James L Patton

    Full Text Available We studied reach adaptation to a 30° visuomotor rotation to determine whether augmented error feedback can promote faster and more complete motor learning. Four groups of healthy adults reached with their unseen arm to visual targets surrounding a central starting point. A manipulandum tracked hand motion and projected a cursor onto a display immediately above the horizontal plane of movement. For one group, deviations from the ideal movement were amplified with a gain of 2 whereas another group experienced a gain of 3.1. The third group experienced an offset equal to the average error seen in the initial perturbations, while a fourth group served as controls. Learning in the gain 2 and offset groups was nearly twice as fast as controls. Moreover, the offset group averaged more reduction in error. Such error augmentation techniques may be useful for training novel visuomotor transformations as required of robotic teleoperators or in movement rehabilitation of the neurologically impaired.

  4. Visuomotor learning enhanced by augmenting instantaneous trajectory error feedback during reaching.

    Science.gov (United States)

    Patton, James L; Wei, Yejun John; Bajaj, Preeti; Scheidt, Robert A

    2013-01-01

    We studied reach adaptation to a 30° visuomotor rotation to determine whether augmented error feedback can promote faster and more complete motor learning. Four groups of healthy adults reached with their unseen arm to visual targets surrounding a central starting point. A manipulandum tracked hand motion and projected a cursor onto a display immediately above the horizontal plane of movement. For one group, deviations from the ideal movement were amplified with a gain of 2 whereas another group experienced a gain of 3.1. The third group experienced an offset equal to the average error seen in the initial perturbations, while a fourth group served as controls. Learning in the gain 2 and offset groups was nearly twice as fast as controls. Moreover, the offset group averaged more reduction in error. Such error augmentation techniques may be useful for training novel visuomotor transformations as required of robotic teleoperators or in movement rehabilitation of the neurologically impaired.

  5. Contributions of microtubule dynamic instability and rotational diffusion to kinetochore capture

    CERN Document Server

    Blackwell, Robert; Edelmaier, Christopher; Gergely, Zachary R; Flynn, Patrick J; Montes, Salvador; Crapo, Ammon; Doostan, Alireza; McIntosh, J Richard; Glaser, Matthew A; Betterton, Meredith D

    2016-01-01

    Microtubule dynamic instability allows search and capture of kinetochores during spindle formation, an important process for accurate chromosome segregation during cell division. Recent work has found that microtubule rotational diffusion about minus-end attachment points contributes to kinetochore capture in fission yeast, but the relative contributions of dynamic instability and rotational diffusion are not well understood. We have developed a biophysical model of kinetochore capture in small fission-yeast nuclei using hybrid Brownian dynamics/kinetic Monte Carlo simulation techniques. With this model, we have studied the importance of dynamic instability and microtubule rotational diffusion for kinetochore capture, both to the lateral surface of a microtubule and at or near its end. Over a range of biologically relevant parameters, microtubule rotational diffusion decreased capture time, but made a relatively small contribution compared to dynamic instability. At most, rotational diffusion reduced capture ...

  6. Stochastic Circumplanetary Dynamics of Rotating Non-Spherical Dust Particles

    Science.gov (United States)

    Makuch, Martin; Brilliantov, N. V.; Sremcevic, M.; Spahn, F.; Krivov, A. V.

    2006-12-01

    Influence of stochastically fluctuating radiation pressure on the dynamics of dust grains on circumplanetary orbits was studied. Stochasticity stems from the permanent change of the particle cross-section due to rotation of nonspherical grains, exposed to the solar radiation. We found that stochasticity depends on the characteristic angular velocity of particles which, according to our estimates, spins very fast on the time scale of the orbital motion. According to this we modelled the stochastic part of the radiation pressure by a Gaussian white noise. Gauss perturbation equations with the radiation pressure being a sum of the deterministic and stochastic component have been used. We observed monotonous increasing standard deviation of the orbital elements, that is, the diffusive-like behaviour of the ensemble, which results in a spatial spreading of initially confined set of particles. By linear approximation we obtained expression for the effective diffusion coefficients and estimate their dependence on the geometrical characteristics of particles and their spin. Teoretical results were compared with numerical simulations performed for the putative dust tori of Mars. Our theory agrees fairly well with simulations for the initial period of the system evolution. The agreement however deteriorates with increasing time where impact of the non-linear terms of the perturbation equations becomes important. Analysis shows that the theoretical results may estimate the low boundary of the time-dependent standard deviation of the orbital elements. In the case of dust ejected from Martian moon Deimos we observed a change of orbital elements up to 10% of their initial values during the first 1000 years of orbital evolution. Our results indicate that the stochastic modulation of the radiation pressure can play an important role in the circumplanetary dynamics of dust and may, together with further noise sources (shadow, planetary bowshock, charge fluctuations, etc

  7. An elementary singularity-free Rotational Brownian Dynamics algorithm for anisotropic particles

    Energy Technology Data Exchange (ETDEWEB)

    Ilie, Ioana M.; Briels, Wim J. [Computational Biophysics, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Otter, Wouter K. den, E-mail: w.k.denotter@utwente.nl [Computational Biophysics, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Multi Scale Mechanics, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

    2015-03-21

    Brownian Dynamics is the designated technique to simulate the collective dynamics of colloidal particles suspended in a solution, e.g., the self-assembly of patchy particles. Simulating the rotational dynamics of anisotropic particles by a first-order Langevin equation, however, gives rise to a number of complications, ranging from singularities when using a set of three rotational coordinates to subtle metric and drift corrections. Here, we derive and numerically validate a quaternion-based Rotational Brownian Dynamics algorithm that handles these complications in a simple and elegant way. The extension to hydrodynamic interactions is also discussed.

  8. Stochastic Rotation Dynamics simulations of wetting multi-phase flows

    Science.gov (United States)

    Hiller, Thomas; Sanchez de La Lama, Marta; Brinkmann, Martin

    2016-06-01

    Multi-color Stochastic Rotation Dynamics (SRDmc) has been introduced by Inoue et al. [1,2] as a particle based simulation method to study the flow of emulsion droplets in non-wetting microchannels. In this work, we extend the multi-color method to also account for different wetting conditions. This is achieved by assigning the color information not only to fluid particles but also to virtual wall particles that are required to enforce proper no-slip boundary conditions. To extend the scope of the original SRDmc algorithm to e.g. immiscible two-phase flow with viscosity contrast we implement an angular momentum conserving scheme (SRD+mc). We perform extensive benchmark simulations to show that a mono-phase SRDmc fluid exhibits bulk properties identical to a standard SRD fluid and that SRDmc fluids are applicable to a wide range of immiscible two-phase flows. To quantify the adhesion of a SRD+mc fluid in contact to the walls we measure the apparent contact angle from sessile droplets in mechanical equilibrium. For a further verification of our wettability implementation we compare the dewetting of a liquid film from a wetting stripe to experimental and numerical studies of interfacial morphologies on chemically structured surfaces.

  9. Dynamics and thermodynamics of a tornado: Rotation effects

    Science.gov (United States)

    Ben-Amots, N.

    2016-09-01

    This paper investigates the relevant processes in the tornado including the dynamics of rotation and thermodynamics as well as condensation. The main novelty of this paper is the explanation of the phenomena occurring in the central downflow. The reduced pressure in the tornado's funnel sucks air and water vapor from the cloud above the tornado. The latent heat of condensation is released in the funnel. The centrifugal force drives the generated water drops out of the funnel. The latent heat of condensation released is also transferred out of the funnel, and supplies the helically ascending air flow surrounding the tornado with additional buoyancy energy. This process gives the tornado increased strength compared to the dust devil type of flow, thus explaining why tornadoes occur always under a cloud, and why the tornado pipe can reach a height of a kilometer and more. To sustain a tornado, the temperature of water vapor at the cloud's base should be higher than the surroundings by a certain minimal value. Remote infrared temperature measurements of clouds' bases may provide indications of the probability that a cloud can spawn a tornado, which may increase the lead time.

  10. On the rotational dynamics of Prometheus and Pandora

    CERN Document Server

    Melnikov, A V; 10.1007/s10569-008-9131-z

    2013-01-01

    Possible rotation states of two satellites of Saturn, Prometheus (S16) and Pandora (S17), are studied by means of numerical experiments. The attitude stability of all possible modes of synchronous rotation and the motion close to these modes is analyzed by means of computation of the Lyapunov spectra of the motion. The stability analysis confirms that the rotation of Prometheus and Pandora might be chaotic, though the possibility of regular behaviour is not excluded. For the both satellites, the attitude instability zones form series of concentric belts enclosing the main synchronous resonance center in the phase space sections. A hypothesis is put forward that these belts might form "barriers" for capturing the satellites in synchronous rotation. The satellites in chaotic rotation can mimic ordinary regular synchronous behaviour: they preserve preferred orientation for long periods of time, the largest axis of satellite's figure being directed approximately towards Saturn.

  11. Dynamic-angle spinning and double rotation of quadrupolar nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, K.T. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Chemistry)

    1991-07-01

    Nuclear magnetic resonance (NMR) spectroscopy of quadrupolar nuclei is complicated by the coupling of the electric quadrupole moment of the nucleus to local variations in the electric field. The quadrupolar interaction is a useful source of information about local molecular structure in solids, but it tends to broaden resonance lines causing crowding and overlap in NMR spectra. Magic- angle spinning, which is routinely used to produce high resolution spectra of spin-{1/2} nuclei like carbon-13 and silicon-29, is incapable of fully narrowing resonances from quadrupolar nuclei when anisotropic second-order quadrupolar interactions are present. Two new sample-spinning techniques are introduced here that completely average the second-order quadrupolar coupling. Narrow resonance lines are obtained and individual resonances from distinct nuclear sites are identified. In dynamic-angle spinning (DAS) a rotor containing a powdered sample is reoriented between discrete angles with respect to high magnetic field. Evolution under anisotropic interactions at the different angles cancels, leaving only the isotropic evolution of the spin system. In the second technique, double rotation (DOR), a small rotor spins within a larger rotor so that the sample traces out a complicated trajectory in space. The relative orientation of the rotors and the orientation of the larger rotor within the magnetic field are selected to average both first- and second-order anisotropic broadening. The theory of quadrupolar interactions, coherent averaging theory, and motional narrowing by sample reorientation are reviewed with emphasis on the chemical shift anisotropy and second-order quadrupolar interactions experienced by half-odd integer spin quadrupolar nuclei. The DAS and DOR techniques are introduced and illustrated with application to common quadrupolar systems such as sodium-23 and oxygen-17 nuclei in solids.

  12. Stochastic rotation dynamics simulation of electro-osmosis

    Science.gov (United States)

    Ceratti, Davide R.; Obliger, Amaël; Jardat, Marie; Rotenberg, Benjamin; Dahirel, Vincent

    2015-09-01

    Stochastic Rotation Dynamics (SRD) is a mesoscale simulation technique that captures hydrodynamic couplings in simple and complex fluids. It can be used in various hydrodynamic regimes and it is not restricted to specific geometries. We show here that SRD using the collisional coupling approach to capture momentum transfer between the semi-implicit solvent and the explicit counterions, is able to describe electro-kinetic effects, i.e. coupled electrostatic and hydrodynamic phenomena occurring at charged solid-liquid interfaces. The method is first validated for electro-osmosis in the simple case of a slit pore without added salt, for which an analytical solution of the Helmholtz-Smoluchowski theory is known, in a physical regime where this mean-field theory is valid. We then discuss the predictions of SRD for electro-osmosis beyond the range of validity of the Helmholtz-Smoluchowski (or Poisson-Nernst-Planck) theory, in particular due to ion-ion correlations at the surface, to charge localisation on discrete sites at the solid surface and to surface charge heterogeneity, that all contribute to a reduction of the electro-osmotic flow. In order to disentangle these last two aspects, we also investigate at the mean-field level a simple system with alternate charged and neutral stripes, using lattice-Boltzmann electro-kinetics simulations. Overall, this work opens new perspectives for the use of SRD as a generic mesoscopic simulation method for soft matter problems, in particular under confinement, since in practice many interfaces between fluids and solids are charged.

  13. Influence of divergent and convergent thinking on visuomotor adaptation in young and older adults.

    Science.gov (United States)

    Simon, Anja; Bock, Otmar

    2016-04-01

    Visuomotor adaptation declines in older age. This has been attributed to cognitive impairments. One relevant cognitive function could be creativity, since creativity is implicated as mediator of early learning. The present study therefore evaluates whether two aspects of creativity, divergent and convergent thinking, are differentially involved in the age-dependent decline of visuomotor adaptation. In 25 young and 24 older volunteers, divergent thinking was assessed by the alternative-uses-task (AUT), convergent thinking by the Intelligenz-Struktur-Test-2000 (IST), and sensorimotor-adaptation by a pointing task with 60° rotated visual feedback. Young participants outperformed older participants in all three tasks. AUT scores were positively associated with young but not older participants' adaptive performance, whereas IST scores were negatively associated with older but not young participants' adaptive performance. This pattern of findings could be attributed to a consistent relationship between AUT, IST and adaptation; taking this into account, adaptation deficits of older participants were no longer significant. We conclude that divergent thinking supports workaround-strategies during adaptation, but doesn't influence visuomotor recalibration. Furthermore, the decay of divergent thinking in older adults may explain most of age-related decline of adaptive strategies. When the age-related decay of divergent thinking coincides with well-preserved convergent thinking, adaptation suffers most.

  14. Is rotating between static and dynamic work beneficial for our fatigue state?

    NARCIS (Netherlands)

    Luger, T.; Bosch, T.; Hoozemans, M.J.M.; Veeger,D.H.E.J.; Looze, M.P. de

    2016-01-01

    Shoulder disorders comprise a large part of work-related musculoskeletal disorders. Risk factors, such as repetitiveness and monotony, may cause muscle fatigue and be attenuated by task rotation. We investigated rotation between a dynamic box-lifting task and a relatively static pick-and-place task

  15. Neurodynamical modeling of arbitrary visuomotor tasks

    OpenAIRE

    Loh, Marco

    2008-01-01

    El aprendizaje visuomotor condicional es un paradigma en el que las asociaciones estímulo-respuesta se aprenden a través de una recompensa. Un experimento típico se desarrolla de la siguiente forma: cuando se presenta un estímulo a un sujeto, éste debe decidir qué acción realizar de entre un conjunto. Una vez seleccionada la acción, el sujeto recibirá una recompensa en el caso de que la acción escogida sea correcta. En este tipo de tareas interactúan distintas regiones cerebrales, entre las q...

  16. Rotational dynamics and heating of trapped nanovaterite particles

    Science.gov (United States)

    Arita, Yoshihiko; Richards, Joseph M.; Mazilu, Michael; Spalding, Gabriel C.; Skelton Spesyvtseva, Susan E.; Craig, Derek; Dholakia, Kishan

    2017-04-01

    We synthesize, optically trap, and rotate individual nanovaterite crystals with a mean particle radius of 423 nm. Rotation rates of up to 4.9 kHz in heavy water are recorded [1]. Laser-induced heating due to residual absorption of the nanovaterite particle results in the superlinear behavior of the rotation rate as a function of trap power. A finite element method based on the Navier-Stokes model for the system allows us to determine the residual optical absorption coefficient for a trapped nanovaterite particle. This is further confirmed by the theoretical model. Our data reveal that the nanoparticle experiences a different Stokes drag torque or force depending on whether we consider rotational or translational motion, which is in a good agreement with the theoretical prediction of the rotational hot Brownian motion [2]. The data allow us to determine the correction factors for the local viscosity for both the rotational and translational motion of the nanoparticle. The use of nanovaterite particles opens up new studies for levitated optomechanics in vacuum [3-6] as well as microrheological properties of cells or biological media [7]. For these latter studies, nanovaterite offers prospects of microviscosity measurements in ultrasmall volumes and, due to its size, potentially simpler uptake by cellular media [8].

  17. Dynamics and Statistical Mechanics of Rotating and non-Rotating Vortical Flows

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Chjan [RPI

    2013-12-18

    Three projects were analyzed with the overall aim of developing a computational/analytical model for estimating values of the energy, angular momentum, enstrophy and total variation of fluid height at phase transitions between disordered and self-organized flow states in planetary atmospheres. It is believed that these transitions in equilibrium statistical mechanics models play a role in the construction of large-scale, stable structures including super-rotation in the Venusian atmosphere and the formation of the Great Red Spot on Jupiter. Exact solutions of the spherical energy-enstrophy models for rotating planetary atmospheres by Kac's method of steepest descent predicted phase transitions to super-rotating solid-body flows at high energy to enstrophy ratio for all planetary spins and to sub-rotating modes if the planetary spin is large enough. These canonical statistical ensembles are well-defined for the long-range energy interactions that arise from 2D fluid flows on compact oriented manifolds such as the surface of the sphere and torus. This is because in Fourier space available through Hodge theory, the energy terms are exactly diagonalizable and hence has zero range, leading to well-defined heat baths.

  18. Dynamic Characteristics of Rotating Stall in Mixed Flow Pump

    Directory of Open Access Journals (Sweden)

    Xiaojun Li

    2013-01-01

    Full Text Available Rotating stall, a phenomenon that causes flow instabilities and pressure hysteresis by propagating at some fraction of the impeller rotational speed, can occur in centrifugal impellers, mixed impellers, radial diffusers, or axial diffusers. Despite considerable efforts devoted to the study of rotating stall in pumps, the mechanics of this phenomenon are not sufficiently understood. The propagation mechanism and onset of rotating stall are not only affected by inlet flow but also by outlet flow as well as the pressure gradient in the flow passage. As such, the complexity of these concepts is not covered by the classical explanation. To bridge this research gap, the current study investigated prerotation generated at the upstream of the impeller, leakage flow at the tip clearance between the casing and the impeller, and strong reserve flow at the inlet of the diffuser. Understanding these areas will clarify the origin of the positive slope of the head-flow performance curve for a mixed flow pump. Nonuniform pressure distribution and adverse pressure gradient were also introduced to evaluate the onset and development of rotating stall within the diffuser.

  19. Flexible explicit but rigid implicit learning in a visuomotor adaptation task.

    Science.gov (United States)

    Bond, Krista M; Taylor, Jordan A

    2015-06-01

    There is mounting evidence for the idea that performance in a visuomotor rotation task can be supported by both implicit and explicit forms of learning. The implicit component of learning has been well characterized in previous experiments and is thought to arise from the adaptation of an internal model driven by sensorimotor prediction errors. However, the role of explicit learning is less clear, and previous investigations aimed at characterizing the explicit component have relied on indirect measures such as dual-task manipulations, posttests, and descriptive computational models. To address this problem, we developed a new method for directly assaying explicit learning by having participants verbally report their intended aiming direction on each trial. While our previous research employing this method has demonstrated the possibility of measuring explicit learning over the course of training, it was only tested over a limited scope of manipulations common to visuomotor rotation tasks. In the present study, we sought to better characterize explicit and implicit learning over a wider range of task conditions. We tested how explicit and implicit learning change as a function of the specific visual landmarks used to probe explicit learning, the number of training targets, and the size of the rotation. We found that explicit learning was remarkably flexible, responding appropriately to task demands. In contrast, implicit learning was strikingly rigid, with each task condition producing a similar degree of implicit learning. These results suggest that explicit learning is a fundamental component of motor learning and has been overlooked or conflated in previous visuomotor tasks. Copyright © 2015 the American Physiological Society.

  20. Visuomotor Dissociation in Cerebral Scaling of Size.

    Science.gov (United States)

    Potgieser, Adriaan R E; de Jong, Bauke M

    2016-01-01

    Estimating size and distance is crucial in effective visuomotor control. The concept of an internal coordinate system implies that visual and motor size parameters are scaled onto a common template. To dissociate perceptual and motor components in such scaling, we performed an fMRI experiment in which 16 right-handed subjects copied geometric figures while the result of drawing remained out of sight. Either the size of the example figure varied while maintaining a constant size of drawing (visual incongruity) or the size of the examples remained constant while subjects were instructed to make changes in size (motor incongruity). These incongruent were compared to congruent conditions. Statistical Parametric Mapping (SPM8) revealed brain activations related to size incongruity in the dorsolateral prefrontal and inferior parietal cortex, pre-SMA / anterior cingulate and anterior insula, dominant in the right hemisphere. This pattern represented simultaneous use of a 'resized' virtual template and actual picture information requiring spatial working memory, early-stage attention shifting and inhibitory control. Activations were strongest in motor incongruity while right pre-dorsal premotor activation specifically occurred in this condition. Visual incongruity additionally relied on a ventral visual pathway. Left ventral premotor activation occurred in all variably sized drawing while constant visuomotor size, compared to congruent size variation, uniquely activated the lateral occipital cortex additional to superior parietal regions. These results highlight size as a fundamental parameter in both general hand movement and movement guided by objects perceived in the context of surrounding 3D space.

  1. Visuomotor Dissociation in Cerebral Scaling of Size.

    Directory of Open Access Journals (Sweden)

    Adriaan R E Potgieser

    Full Text Available Estimating size and distance is crucial in effective visuomotor control. The concept of an internal coordinate system implies that visual and motor size parameters are scaled onto a common template. To dissociate perceptual and motor components in such scaling, we performed an fMRI experiment in which 16 right-handed subjects copied geometric figures while the result of drawing remained out of sight. Either the size of the example figure varied while maintaining a constant size of drawing (visual incongruity or the size of the examples remained constant while subjects were instructed to make changes in size (motor incongruity. These incongruent were compared to congruent conditions. Statistical Parametric Mapping (SPM8 revealed brain activations related to size incongruity in the dorsolateral prefrontal and inferior parietal cortex, pre-SMA / anterior cingulate and anterior insula, dominant in the right hemisphere. This pattern represented simultaneous use of a 'resized' virtual template and actual picture information requiring spatial working memory, early-stage attention shifting and inhibitory control. Activations were strongest in motor incongruity while right pre-dorsal premotor activation specifically occurred in this condition. Visual incongruity additionally relied on a ventral visual pathway. Left ventral premotor activation occurred in all variably sized drawing while constant visuomotor size, compared to congruent size variation, uniquely activated the lateral occipital cortex additional to superior parietal regions. These results highlight size as a fundamental parameter in both general hand movement and movement guided by objects perceived in the context of surrounding 3D space.

  2. Mass Distribution in Rotating Thin-Disk Galaxies According to Newtonian Dynamics

    Directory of Open Access Journals (Sweden)

    James Q. Feng

    2014-04-01

    Full Text Available An accurate computational method is presented for determining the mass distribution in a mature spiral galaxy from a given rotation curve by applying Newtonian dynamics for an axisymmetrically rotating thin disk of finite size with or without a central spherical bulge. The governing integral equation for mass distribution is transformed via a boundary-element method into a linear algebra matrix equation that can be solved numerically for rotation curves with a wide range of shapes. To illustrate the effectiveness of this computational method, mass distributions in several mature spiral galaxies are determined from their measured rotation curves. All the surface mass density profiles predicted by our model exhibit approximately a common exponential law of decay, quantitatively consistent with the observed surface brightness distributions. When a central spherical bulge is present, the mass distribution in the galaxy is altered in such a way that the periphery mass density is reduced, while more mass appears toward the galactic center. By extending the computational domain beyond the galactic edge, we can determine the rotation velocity outside the cut-off radius, which appears to continuously decrease and to gradually approach the Keplerian rotation velocity out over twice the cut-off radius. An examination of circular orbit stability suggests that galaxies with flat or rising rotation velocities are more stable than those with declining rotation velocities especially in the region near the galactic edge. Our results demonstrate the fact that Newtonian dynamics can be adequate for describing the observed rotation behavior of mature spiral galaxies.

  3. Rotational spectrum and dynamics of tetrahydrofuran-argon

    Energy Technology Data Exchange (ETDEWEB)

    Melandri, S.; Favero, P.G.; Caminati, W. [Dipartimento di Chimica ' G. Ciamician' dell' Universita, Via Selmi 2, I-40126 Bologna (Italy); Lopez, J.C.; Alonso, J.L. [Departamento de Quimica-Fisica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid (Spain)

    1998-12-15

    The jet-cooled rotational spectrum of the tetrahydrofuran-argon molecular complex has been investigated by millimeter-wave absorption and Fourier transform microwave spectroscopies. The argon atom is located nearly over the oxygen atom, almost perpendicularly to the COC plane. Each rotational transition is split in two component lines due to the residual pseudorotational effects of the ring in the complex. The splitting between the two vibrational sublevels has been calculated to be 111.345(44) MHz. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved000.

  4. Dynamic analysis on generalized linear elastic body subjected to large scale rigid rotations

    Institute of Scientific and Technical Information of China (English)

    刘占芳; 颜世军; 符志

    2013-01-01

    The dynamic analysis of a generalized linear elastic body undergoing large rigid rotations is investigated. The generalized linear elastic body is described in kine-matics through translational and rotational deformations, and a modified constitutive relation for the rotational deformation is proposed between the couple stress and the curvature tensor. Thus, the balance equations of momentum and moment are used for the motion equations of the body. The floating frame of reference formulation is applied to the elastic body that conducts rotations about a fixed axis. The motion-deformation coupled model is developed in which three types of inertia forces along with their incre-ments are elucidated. The finite element governing equations for the dynamic analysis of the elastic body under large rotations are subsequently formulated with the aid of the constrained variational principle. A penalty parameter is introduced, and the rotational angles at element nodes are treated as independent variables to meet the requirement of C1 continuity. The elastic body is discretized through the isoparametric element with 8 nodes and 48 degrees-of-freedom. As an example with an application of the motion-deformation coupled model, the dynamic analysis on a rotating cantilever with two spatial layouts relative to the rotational axis is numerically implemented. Dynamic frequencies of the rotating cantilever are presented at prescribed constant spin velocities. The maximal rigid rotational velocity is extended for ensuring the applicability of the linear model. A complete set of dynamical response of the rotating cantilever in the case of spin-up maneuver is examined, it is shown that, under the ultimate rigid rotational velocities less than the maximal rigid rotational velocity, the stress strength may exceed the material strength tolerance even though the displacement and rotational angle responses are both convergent. The influence of the cantilever layouts on their responses and

  5. Enhanced active dynamic balancing of the planar robots using a three-rotating-bar balancer

    Directory of Open Access Journals (Sweden)

    Kun Wang

    2016-04-01

    Full Text Available The concept of full compensation against the resultant shaking forces and moments for arbitrary robots using a single active dynamic balancing mechanism is first addressed. And the application principle and general balancing conditions of the active dynamic balancing mechanism are presented. With the purpose of providing detailed description of these problems, a compact planar 3-degree-of-freedom active dynamic balancing mechanism is proposed. The active balancer is composed of three independent rotating bars with their respective actuators. The rotations of the three bars could change their center of gravity positions and then generate balancing forces for the unbalanced robots. Moreover, the changing of the angular acceleration of the bars can also generate a dynamic torque to balance the shaking moment. In order to present more detail of the balancing theory, the structure and kinematic and dynamic analysis of the proposed balancing mechanism are given. Finally, numerical examples illustrate the effectiveness of the proposed three-rotating-bar balancer.

  6. Dynamic Modeling of the SMAP Rotating Flexible Antenna

    Science.gov (United States)

    Nayeri, Reza D.

    2012-01-01

    Dynamic model development in ADAMS for the SMAP project is explained: The main objective of the dynamic models are for pointing error assessment, and the control/stability margin requirement verifications

  7. Dynamic Modeling of the SMAP Rotating Flexible Antenna

    Science.gov (United States)

    Nayeri, Reza D.

    2012-01-01

    Dynamic model development in ADAMS for the SMAP project is explained: The main objective of the dynamic models are for pointing error assessment, and the control/stability margin requirement verifications

  8. Coriolis Effects in the Dynamics of a Rotating Elastic Structure

    DEFF Research Database (Denmark)

    Brøns, Morten; Hjorth, Poul G.; Kliem, Wolfhard

    1996-01-01

    Small oscillations of a rotating elasticum with a mass at the free end are investigated with Poincare-Lindstedt series. It is shown that the mass moves on a figure-eight shaped curve in a direction determined by the sign of the angular velocity and hence that the Coriolis force influences...

  9. Dynamics of a rotating flat ellipsoid with a stochastic oblateness

    CERN Document Server

    Behar, Etienne; Pierret, Frédéric

    2014-01-01

    We derive a model for the motion of a rotating flat ellispoid with a stochastic flattening based on an invariance theorem for stochastic differential equations. A numerical study of a toy-model is performed leading to an intriguing coincidence with observational data.

  10. Fluid dynamics analysis of a rotating axisymmetric part using FIDAP

    Science.gov (United States)

    Giles, G. E.; Kirkpatrick, J. R.; Wendel, M. W.; Bullock, J. S., IV

    1990-03-01

    The effect of fluid flow on electrochemical plating on a rotating axisymmetric part was investigated by using a finite element computer code, FIDAP. The results from these investigations compare well with analytical results for laminar flow conditions. The addition of a nonrotating shield was also investigated for laminar flow conditions. An attempt to extend these analyses to turbulent conditions was unsuccessful.

  11. Dynamics of granular flows down rotating semi-cylindrical chutes

    NARCIS (Netherlands)

    Shirsath, S.S.; Padding, J.T.; Clercx, H.J.H.; Kuipers, J.A.M.; Han, Yongshen; Ge, Wei; Wang, Junwu; Wang, Limin; Liu, Xinhua

    2015-01-01

    The behavior of spherical particles flowing down a three-dimensional chute, inclined at fixed angle, is commonly simulated by a discrete element method (DEM). DEM is nowadays a standard tool for numerical studies of e.g. gas-solid fluidized beds. We have modified DEM for the simulation of rotating g

  12. New Dynamic Spin Rig Capabilities Used to Determine Rotating Blade Dynamics

    Science.gov (United States)

    Provenza, Andrew J.

    2004-01-01

    The Dynamic Spin Rig Facility at the NASA Glenn Research Center is used to determine the structural response of rotating engine components without the effects of aerodynamic loading. Recently, this rig's capabilities were enhanced through the replacement of grease-lubricated ball bearings with magnetic bearings. Magnetic bearings offer a number of advantages--the most important here being that they not only fully support the rotor system, but excite it as well. Three magnetic bearings support the rotor and provide five axes of controlled motion: an x- and y-axis translation at each of two radial bearings and a z-axis translation in the vertical or axial direction. Sinusoidal excitation (most commonly used) can be imparted on the rotor through the radial magnetic bearings in either a fixed or rotating frame of reference. This excitation is added directly to the magnetic bearing control output. Since the rotor is fully levitated, large translations and rotations of the rotor system can be achieved. Some of the capabilities of this excitation system were determined and reported. The accelerations obtained at the tip of a titanium flat plate test article versus the swept sine excitation sent to both radial bearings in phase and perpendicular to the plane containing the two blades are shown. Recent tests required the excitation of fundamental bending and torsional blade resonances at rotor speeds up to 10,000 rpm. Successful fixed synchronous rotation of the excitation signal provided the best detectable blade resonant vibrations at excitation frequencies up to 1100 Hz for the particular blades of interest. A noncontacting laser measurement system was used to collect blade-tip motions. From these data, the amplitude and frequency of the motion could be determined as well as the blade damping properties. Damping could be determined using two methods: (1) free decay and (2) curve fitting the vibration amplitude as a function of frequency in and around the resonance of

  13. Spinning Up Interest: Classroom Demonstrations of Rotating Fluid Dynamics

    Science.gov (United States)

    Aurnou, J.

    2005-12-01

    The complex relationship between rotation and its effect on fluid motions presents some of the most difficult and vexing concepts for both undergraduate and graduate level students to learn. We have found that student comprehension is greatly increased by the presentation of in-class fluid mechanics experiments. A relatively inexpensive experimental set-up consists of the following components: a record player, a wireless camera placed in the rotating frame, a tank of fluid, and food coloring. At my poster, I will use this set-up to carry out demonstrations that illustrate the Taylor-Proudman theorem, flow within the Ekman layer, columnar convection, and flow around high and low pressure centers. By sending the output of the wireless camera through an LCD projection system, such demonstrations can be carried out even for classes in large lecture halls.

  14. Rotating magnetic particle microrheometry in biopolymer fluid dynamics: mucus microrheology.

    Science.gov (United States)

    Besseris, George J; Yeates, Donovan B

    2007-09-14

    The polymer properties of canine mucus were investigated through the method of rotating magnetic particle microrheometry. Mucus is visualized as a physically entangled biopolymer of low polydispersity in a water-based solution. Mucus was modeled according to the constitutive law of a Doi-Edwards fluid. The magnetic-particle equation of rotational motion is analytically solved in the linear viscoelastic limit rendering theoretical flow profiles which are used to fit the experimental trace signals of the particle remanent-magnetic-field decay. The zero-shear-rate viscosity was found to be 18,000 P and the relaxation time at about 42 s. The molecular weight between entanglements for mucins was estimated at 1.7 MDa rendering an estimation of about seven physical cross-links per molecule. Rheological investigations were extended also to diluted and concentrated rations of the normal mucus simulating the conditions found in more physiological extremes.

  15. Ageing dynamics of translational and rotational diffusion in a colloidal glass

    Energy Technology Data Exchange (ETDEWEB)

    Jabbari-Farouji, Sara [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018XE Amsterdam (Netherlands); Eiser, Erika [van' t Hoff Institute for Molecular Sciences, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam (Netherlands); Wegdam, Gerard H [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018XE Amsterdam (Netherlands); Bonn, Daniel [Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65, 1018XE Amsterdam (Netherlands)

    2004-10-20

    We study the dynamics of translational and rotational diffusion during the ageing of a colloidal glass of Laponite using polarized and depolarized dynamic light scattering. The dynamics are qualitatively similar between the two degrees of freedom. The short-time diffusion is independent of the time elapsed since the sample preparation. The intermediate- and long-time diffusion, on the other hand, slows down by several orders of magnitude during the ageing. The slowing down of the rotational diffusion is found to be much faster than that of the translational diffusion. (letter to the editor)

  16. Neurodynamics of the prefrontal cortex during conditional visuomotor associations.

    Science.gov (United States)

    Loh, Marco; Pasupathy, Anitha; Miller, Earl K; Deco, Gustavo

    2008-03-01

    The prefrontal cortex is believed to be important for cognitive control, working memory, and learning. It is known to play an important role in the learning and execution of conditional visuomotor associations, a cognitive task in which stimuli have to be associated with actions by trial-and-error learning. In our modeling study, we sought to integrate several hypotheses on the function of the prefrontal cortex using a computational model, and compare the results to experimental data. We constructed a module of prefrontal cortex neurons exposed to two different inputs, which we envision to originate from the inferotemporal cortex and the basal ganglia. We found that working memory properties do not describe the dominant dynamics in the prefrontal cortex, but the activation seems to be transient, probably progressing along a pathway from sensory to motor areas. During the presentation of the cue, the dynamics of the prefrontal cortex is bistable, yielding a distinct activation for correct and error trails. We find that a linear change in network parameters relates to the changes in neural activity in consecutive correct trials during learning, which is important evidence for the underlying learning mechanisms.

  17. Bifurcation suppression of nonlinear systems via dynamic output feedback and its applications to rotating stall control

    Institute of Scientific and Technical Information of China (English)

    Pengnian CHEN; Huashu QIN; Shengwei MEI

    2005-01-01

    This paper deals with the problems of bifurcation suppression and bifurcation suppression with stability of nonlinear systems. Necessary conditions and sufficient conditions for bifurcation suppression via dynamic output feedback are presented;Sufficient conditions for bifurcation suppression with stability via dynamic output feedback are obtained. As an application, a dynamic compensator, which guarantees that the bifurcation point of rotating stall in axial flow compressors is stably suppressed, is constructed.

  18. Remarks on stability of the rotating shallow-water vortices in the frontal dynamics regime

    Energy Technology Data Exchange (ETDEWEB)

    Jelloul, M.B.; Zeitlin, V. [P. et M. Curie Univ., Paris (France). Lab. de Meteorologie Dynamique

    1999-12-01

    Stability properties of large-scale strongly nonlinear isolated vortices in the rotating shallow water on the f-plane are analysed. Working first in the framework of the balanced frontal dynamics equations, the authors demonstrate that vortices of arbitrary sign with monotonous profiles of the free-surface elevation are formally stable and establish criteria for nonlinear stability. Stability in the framework of the full rotating shallow-water equations is also discussed and a conditional stability criterion is obtained.

  19. Statistical and dynamical aspects in fission process: The rotational degrees of freedom

    Indian Academy of Sciences (India)

    Bency John

    2015-08-01

    In the final phases of fission process, there are fast collective rotational degrees of freedom, which can exert a force on the slower tilting rotational degree. Experimental observations that lead to this realization and theoretical studies that account for dynamics of the processes are discussed briefly. Supported by these studies, and by assuming a conditional equilibrium of the collective rotational modes at a pre-scission point, a new statistical model for fission fragment angular and spin distributions has been developed. This model gives a consistent description of the fragment angular and spin distributions for a wide variety of heavy- and light-ion-induced fission reactions.

  20. Rotation of single live mammalian cells using dynamic holographic optical tweezers

    Science.gov (United States)

    Bin Cao; Kelbauskas, Laimonas; Chan, Samantha; Shetty, Rishabh M.; Smith, Dean; Meldrum, Deirdre R.

    2017-05-01

    We report on a method for rotating single mammalian cells about an axis perpendicular to the optical system axis through the imaging plane using dynamic holographic optical tweezers (HOTs). Two optical traps are created on the opposite edges of a mammalian cell and are continuously transitioned through the imaging plane along the circumference of the cell in opposite directions, thus providing the torque to rotate the cell in a controlled fashion. The method enables a complete 360° rotation of live single mammalian cells with spherical or near-to spherical shape in 3D space, and represents a useful tool suitable for the single cell analysis field, including tomographic imaging.

  1. Controlled Activation of Protein Rotational Dynamics Using Smart Hydrogel Tethering

    Energy Technology Data Exchange (ETDEWEB)

    Beech, Brenda M.; Xiong, Yijia; Boschek, Curt B.; Baird, Cheryl L.; Bigelow, Diana J.; Mcateer, Kathleen; Squier, Thomas C.

    2014-09-05

    Stimulus-responsive hydrogel materials that stabilize and control protein dynamics have the potential to enable a range of applications to take advantage of the inherent specificity and catalytic efficiencies of proteins. Here we describe the modular construction of a hydrogel using an engineered calmodulin (CaM) within a polyethylene glycol (PEG) matrix that involves the reversible tethering of proteins through an engineered CaM-binding sequence. For these measurements, maltose binding protein (MBP) was isotopically labeled with [13C] and [15N], permitting dynamic structural measurements using TROSY-HSQC NMR spectroscopy. Upon initial formation of hydrogels protein dynamics are suppressed, with concomitant increases in protein stability. Relaxation of the hydrogel matrix following transient heating results in the activation of protein dynamics and restoration of substrate-induced large-amplitude domain motions necessary for substrate binding.

  2. The relationship between trunk rotation, upper quarter dynamic stability and pitch velocity.

    Science.gov (United States)

    Bullock, Garrett S; Schmitt, Abigail C; Chasse, Patrick; Little, Barrett A; Diehl, Lee H; Butler, Robert J

    2017-02-21

    Understanding the relationship between upper quarter mobility, dynamic stability and pitching velocity may be beneficial in elucidating underlying factors that affect pitching performance. The purpose of this study was to investigate upper trunk rotation mobility and upper quarter dynamic stability and their correlation to pitch velocity in NCAA Division I collegiate pitchers. We hypothesized that collegiate pitchers with greater upper trunk rotation mobility and upper extremity dynamic stability would exhibit higher pitching velocity. Trunk rotation and the Upper Quarter Y-Balance Test (YBT-UQ) were measured utilizing standardized protocols. Collegiate pitchers (n=30) then proceeded to complete their team prescribed dynamic and throwing warm up followed by a pitching session from regulation distance at 100% effort. Each pitch was recorded for velocity and pitch type, only fastballs were utilized in analysis. The relationships between trunk rotation and fastball velocity, and YBT-UQ scores and fastball velocity were assessed using a series of two-tail Pearsons Correlations (p<.05). Throwing and non-throwing sides (69.6± 9.5 deg., 70.7± 9.4 deg.) had similar trunk rotation mobility. No statistically significant correlation between upper trunk rotation mobility and pitch velocity was found (throwing arm: r=.131, p<.491; non-throwing arm: r=.135, p<.478). There was also no correlation between the YBT-UQ and fastball velocity. In this study of Division I baseball pitchers, we found no relationship between trunk rotational mobility, upper quarter dynamic stability and pitching velocity. This suggests that increased upper extremity stability and trunk mobility are not directly related to fastball velocity. Understanding factors that associate to velocity may be helpful in predicting pitching performance.

  3. A Detailed Study of the Rotational Augmentation and Dynamic Stall Phenomena for Wind Turbines

    DEFF Research Database (Denmark)

    Guntur, Srinivas

    ), using rotationally augmented steady state polars as the input instead of the typically used 2D (stationary) data. The aim of this part of the work has been to investigate the differences between the stall phenomenon on harmonically pitching blades on a rotating wind turbine and the classic dynamic stall......This thesis presents investigations into the aerodynamics of wind turbine rotors, with a focus on the in-board sections of the rotor. Two important aerodynamic phenomena that have challenged scientists over nearly the last half a century are the so-called rotational augmentation and dynamic stall...... on wind turbine blades using the N-sequence data of the NREL UAE Phase VI experiment. The experimental data is compared with the results from unsteady Delayed Detached Eddy Simulations (DDES). The same conditions are also modelled using a Beddoes-Leishman type dynamic stall model by Hansen et al. (2004...

  4. Elastic dynamic research of high speed multi-link precision press considering structural stiffness of rotation joints

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Feng Feng; Sun, Yu; Peng, Bin Bin [School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing (China)

    2016-10-15

    An elastic dynamic model of high-speed multi-link precision press considering structural stiffness of rotation joints was established by the finite element method. In the finite element model, rotation joint was established by four bar elements with equivalent stiffness, and connected link was established by beam element. Then, the elastic dynamics equation of the system was established, and modal superposition method was used to solve the dynamic response. Compared with the traditional elastic dynamic model with perfect constraint of the rotation joints, the elastic dynamic response value of the improved model is larger. To validate the presented new method of elastic dynamics analysis with stiffness of rotation joints, a related test of slider Bottom dead center (BDC) position in different speed was designed. The test shows that the model with stiffness of rotation joints is more reasonable. So it provides a reasonable theory and method for dynamic characteristics research of such a multi-link machine.

  5. Rotational Brownian Dynamics simulations of clathrin cage formation

    NARCIS (Netherlands)

    Ilie, I.M.; Otter, den W.K.; Briels, W.J.

    2014-01-01

    The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the assem

  6. Rotational Brownian Dynamics simulations of clathrin cage formation

    NARCIS (Netherlands)

    Ilie, Ioana Mariuca; den Otter, Wouter K.; Briels, Willem J.

    2014-01-01

    The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the

  7. Characterization of Cortical Networks and Corticocortical Functional Connectivity Mediating Arbitrary Visuomotor Mapping.

    Science.gov (United States)

    Brovelli, Andrea; Chicharro, Daniel; Badier, Jean-Michel; Wang, Huifang; Jirsa, Viktor

    2015-09-16

    Adaptive behaviors are built on the arbitrary linkage of sensory inputs to actions and goals. Although the sensorimotor and associative frontostriatal circuits are known to mediate arbitrary visuomotor mappings, the underlying corticocortico dynamics remain elusive. Here, we take a novel approach exploiting gamma-band neural activity to study the human cortical networks and corticocortical functional connectivity mediating arbitrary visuomotor mapping. Single-trial gamma-power time courses were estimated for all Brodmann areas by combing magnetoencephalographic and MRI data with spectral analysis and beam-forming techniques. Linear correlation and Granger causality analyses were performed to investigate functional connectivity between cortical regions. The performance of visuomotor associations was characterized by an increase in gamma-power and functional connectivity over the sensorimotor and frontoparietal network, in addition to medial prefrontal areas. The superior parietal area played a driving role in the network, exerting Granger causality on the dorsal premotor area. Premotor areas acted as relay from parietal to medial prefrontal cortices, which played a receiving role in the network. Link community analysis further revealed that visuomotor mappings reflect the coordination of multiple subnetworks with strong overlap over motor and frontoparietal areas. We put forward an associative account of the underlying cognitive processes and corticocortical functional connectivity. Overall, our approach and results provide novel perspectives toward a better understanding of how distributed brain activity coordinates adaptive behaviors. In everyday life, most of our behaviors are based on the arbitrary linkage of sensory information to actions and goals, such as stopping at a red traffic light. Despite their automaticity, such behaviors rely on the activity of a large brain network and elusive interareal functional connectivity. We take a novel approach exploiting

  8. Translational, rotational and vibrational relaxation dynamics of a solute molecule in a non-interacting solvent

    Science.gov (United States)

    Grubb, Michael P.; Coulter, Philip M.; Marroux, Hugo J. B.; Hornung, Balazs; McMullen, Ryan S.; Orr-Ewing, Andrew J.; Ashfold, Michael N. R.

    2016-11-01

    Spectroscopically observing the translational and rotational motion of solute molecules in liquid solutions is typically impeded by their interactions with the solvent, which conceal spectral detail through linewidth broadening. Here we show that unique insights into solute dynamics can be made with perfluorinated solvents, which interact weakly with solutes and provide a simplified liquid environment that helps to bridge the gap in our understanding of gas- and liquid-phase dynamics. Specifically, we show that in such solvents, the translational and rotational cooling of an energetic CN radical can be observed directly using ultrafast transient absorption spectroscopy. We observe that translational-energy dissipation within these liquids can be modelled through a series of classic collisions, whereas classically simulated rotational-energy dissipation is shown to be distinctly faster than experimentally measured. We also observe the onset of rotational hindering from nearby solvent molecules, which arises as the average rotational energy of the solute falls below the effective barrier to rotation induced by the solvent.

  9. Nonlinear Dynamic Behaviors of Rotated Blades with Small Breathing Cracks Based on Vibration Power Flow Analysis

    Directory of Open Access Journals (Sweden)

    Hailong Xu

    2016-01-01

    Full Text Available Rotated blades are key mechanical components in turbomachinery and high cycle fatigues often induce blade cracks. Accurate detection of small cracks in rotated blades is very significant for safety, reliability, and availability. In nature, a breathing crack model is fit for a small crack in a rotated blade rather than other models. However, traditional vibration displacements-based methods are less sensitive to nonlinear characteristics due to small breathing cracks. In order to solve this problem, vibration power flow analysis (VPFA is proposed to analyze nonlinear dynamic behaviors of rotated blades with small breathing cracks in this paper. Firstly, local flexibility due to a crack is derived and then time-varying dynamic model of the rotated blade with a small breathing crack is built. Based on it, the corresponding vibration power flow model is presented. Finally, VPFA-based numerical simulations are done to validate nonlinear behaviors of the cracked blade. The results demonstrate that nonlinear behaviors of a crack can be enhanced by power flow analysis and VPFA is more sensitive to a small breathing crack than displacements-based vibration analysis. Bifurcations will occur due to breathing cracks and subharmonic resonance factors can be defined to identify breathing cracks. Thus the proposed method can provide a promising way for detecting and predicting small breathing cracks in rotated blades.

  10. Linking partial and quasi dynamical symmetries in rotational nuclei

    CERN Document Server

    Kremer, C; Leviatan, A; Pietralla, N; Rainovski, G; Trippel, R; Van Isacker, P

    2014-01-01

    Background: Quasi dynamical symmetries (QDS) and partial dynamical symmetries (PDS) play an important role in the understanding of complex systems. Up to now these symmetry concepts have been considered to be unrelated. Purpose: Establish a link between PDS and QDS and find an emperical manifestation. Methods: Quantum number fluctuations and the intrinsic state formalism are used within the framework of the interacting boson model of nuclei. Results: A previously unrecognized region of the parameter space of the interacting boson model that has both O(6) PDS (purity) and SU(3) QDS (coherence) in the ground band is established. Many rare-earth nuclei approximately satisfying both symmetry requirements are identified. Conclusions: PDS are more abundant than previously recognized and can lead to a QDS of an incompatible symmetry.

  11. Quantum Dynamics of Mesoscopic Driven Duffing Oscillators in Rotating Frame

    CERN Document Server

    Guo, Lingzhen; Li, Xin-Qi

    2010-01-01

    We investigate the nonlinear dynamics of a mesoscopic driven Duffing oscillator in a quantum regime. We construct a bifurcation equation applicable in quantum regime. The predictions of our bifurcation equation agree with numerical results perfectly. In terms ofWigner function, we identify the nature of state near the bifurcation point, and extract the transition rate, which displays perfect scaling behavior with the driving distance to the bifurcation point.

  12. Design and Construction of an Affordable Rotating Table for Classroom Demonstrations of Geophysical Fluid Dynamics Principles.

    Science.gov (United States)

    McNoldy, Brian D.; Cheng, Anning; Eitzen, Zachary A.; Moore, Richard W.; Persing, John; Schaefer, Kevin; Schubert, Wayne H.

    2003-12-01

    Rotating tables have been in use for many years because of their ability to demonstrate fluid dynamical phenomena, shedding insight on the sometimes complicated or esoteric mathematics used to describe such processes. A small team of students at the Colorado State University (CSU) Department of Atmospheric Science constructed a rotating table, or “spin tank,” assembly that is simple and affordable, yet instructive.The apparatus is designed to be easy to maintain and operate. The number of moving parts is kept at a minimum, and the electrical components chosen are of high quality. With the aid of a brief instruction manual or tutorial, students and faculty can operate the rotating table and easily perform many demonstrations, with the freedom to vary fluid depth, rotation rate, and acceleration. The entire design and construction process was conducted on a limited budget of &;3,000.A spin tank such as this has practical applications for the qualitative study of fluid dynamics. Fundamental concepts in rotating flow dynamics can be demonstrated to supplement the more rigorous mathematical treatment typically given in oceanography or atmospheric physics graduate-level courses. Topics that have been explored thus far are Ekman pumping, Taylor columns, and barotropic instability, but could be broadened to include subjects such as Rossby waves, baroclinic instability, vortex merger, and thermal convection.

  13. Nonadiabatic dissociation dynamics in H2O: Competition between rotationally and nonrotationally mediated pathways

    Science.gov (United States)

    Yuan, Kaijun; Cheng, Yuan; Cheng, Lina; Guo, Qing; Dai, Dongxu; Wang, Xiuyan; Yang, Xueming; Dixon, Richard N.

    2008-01-01

    The photochemistry of H2O in the VUV region is important in interstellar chemistry. Whereas previous studies of the photodissociation used excitation via unbound states, we have used a tunable VUV photolysis source to excite individual levels of the rotationally structured C̃ state near 124 nm. The ensuing OH product state distributions were recorded by using the H-atom Rydberg tagging technique. Experimental results indicate a dramatic variation in the OH product state distributions and its stereodynamics for different resonant states. Photodissociation of H2O(C̃) in rotational states with k′a = 0 occurs exclusively through a newly discovered homogeneous coupling to the à state, leading to OH products that are vibrationally hot (up to v = 13), but rotationally cold. In contrast, for H2O in rotationally excited states with k′a > 0, an additional pathway opens through Coriolis-type coupling to the B̃ state surface. This yields extremely rotationally hot and vibrationally cold ground state OH(X) and electronically excited OH(A) products, through 2 different mechanisms. In the case of excitation via the 110 ← 000 transition the H atoms for these 2 product channels are ejected in completely different directions. Quantum dynamical models for the C̃-state photodissociation clearly support this remarkable dynamical picture, providing a uniquely detailed illustration of nonadiabatic dynamics involving at least 4 electronic surfaces. PMID:19047628

  14. The Gaia-ESO Survey: dynamical models of flattened, rotating globular clusters

    Science.gov (United States)

    Jeffreson, S. M. R.; Sanders, J. L.; Evans, N. W.; Williams, A. A.; Gilmore, G. F.; Bayo, A.; Bragaglia, A.; Casey, A. R.; Flaccomio, E.; Franciosini, E.; Hourihane, A.; Jackson, R. J.; Jeffries, R. D.; Jofré, P.; Koposov, S.; Lardo, C.; Lewis, J.; Magrini, L.; Morbidelli, L.; Pancino, E.; Randich, S.; Sacco, G. G.; Worley, C. C.; Zaggia, S.

    2017-08-01

    We present a family of self-consistent axisymmetric rotating globular cluster models which are fitted to spectroscopic data for NGC 362, NGC 1851, NGC 2808, NGC 4372, NGC 5927 and NGC 6752 to provide constraints on their physical and kinematic properties, including their rotation signals. They are constructed by flattening Modified Plummer profiles, which have the same asymptotic behaviour as classical Plummer models, but can provide better fits to young clusters due to a slower turnover in the density profile. The models are in dynamical equilibrium as they depend solely on the action variables. We employ a fully Bayesian scheme to investigate the uncertainty in our model parameters (including mass-to-light ratios and inclination angles) and evaluate the Bayesian evidence ratio for rotating to non-rotating models. We find convincing levels of rotation only in NGC 2808. In the other clusters, there is just a hint of rotation (in particular, NGC 4372 and NGC 5927), as the data quality does not allow us to draw strong conclusions. Where rotation is present, we find that it is confined to the central regions, within radii of R ≤ 2rh. As part of this work, we have developed a novel q-Gaussian basis expansion of the line-of-sight velocity distributions, from which general models can be constructed via interpolation on the basis coefficients.

  15. On the rotational equations of motion in rigid body dynamics when using Euler parameters.

    Science.gov (United States)

    Sherif, Karim; Nachbagauer, Karin; Steiner, Wolfgang

    Many models of three-dimensional rigid body dynamics employ Euler parameters as rotational coordinates. Since the four Euler parameters are not independent, one has to consider the quaternion constraint in the equations of motion. This is usually done by the Lagrange multiplier technique. In the present paper, various forms of the rotational equations of motion will be derived, and it will be shown that they can be transformed into each other. Special attention is hereby given to the value of the Lagrange multiplier and the complexity of terms representing the inertia forces. Particular attention is also paid to the rotational generalized external force vector, which is not unique when using Euler parameters as rotational coordinates.

  16. Using Distributed Rotations for a Low-Complexity Dynamic Decode-and-Forward Relay Protocol

    CERN Document Server

    Hucher, Charlotte

    2011-01-01

    In this paper, we propose to implement the dynamic decode-and-forward (DDF) protocol with distributed rotations. In addition to being the first minimum-delay implementation of the DDF protocol proposed for any number of relays, this technique allows to exploit cooperative diversity without inducing the high decoding complexity of a space-time code. The analysis of outage probabilities for different number of relays and rotations shows that the performance of this technique is close to optimal. Moreover, a lower-bound on the diversity-multiplexing gain tradeoff (DMT) is provided in the case of a single relay and two rotations. This lower-bound reaches the optimal DDF's DMT when the frame-length grows to infinity, which shows that even a small number of rotations is enough to obtain good performance.

  17. Asymptotic theory of gravity modes in rotating stars. I. Ray dynamics

    CERN Document Server

    Prat, Vincent; Ballot, Jérôme

    2015-01-01

    Context. The seismology of early-type stars is limited by our uncomplete understanding of gravito-inertial modes. Aims. We develop a short-wavelength asymptotic analysis for gravito-inertial modes in rotating stars. Methods. The Wentzel-Kramers-Brillouin approximation is applied to the equations governing adiabatic small perturbations about a model of uniformly rotating barotropic star. Results. A general eikonal equation, including the effect of the centrifugal deformation, is derived. The dynamics of axisymmetric gravito-inertial rays is solved numerically for polytropic stellar models of increasing rotation and analysed by describing the structure of the phase space. Three different types of phase space structures are distinguished. The first type results from the continuous evolution of structures of the non-rotating integrable phase space. It is predominant in the low-frequency part of the phase space. The second type of structures is island chains associated with stable periodic rays. The third type of ...

  18. Forcing-dependent dynamics and emergence of helicity in rotating turbulence

    CERN Document Server

    Dallas, Vassilios

    2016-01-01

    The effects of large scale mechanical forcing on the dynamics of rotating turbulent flows are studied by means of numerical simulations, varying systematically the nature of the mechanical force in time. We demonstrate that the statistically stationary solutions of these flows depend on the nature of the forcing mechanism. Rapidly enough rotating flows with a forcing that has a persistent direction relatively to the axis of rotation bifurcate from a non-helical state to a helical state despite the fact that the forcing is non-helical. We find that the nature of the mechanical force in time and the emergence of helicity have direct implications on the cascade dynamics of these flows, determining the anisotropy in the flow, the energy condensation at large scales and the power-law energy spectra that are consistent with previous findings and phenomenologies under strong and weak-wave turbulent conditions.

  19. Unstable normal modes of low T/W dynamical instabilities in differentially rotating stars

    CERN Document Server

    Saijo, Motoyuki

    2016-01-01

    We investigate the nature of low T/W dynamical instabilities in differentially rotating stars by means of linear perturbation. Here, T and W represent rotational kinetic energy and the gravitational binding energy of the star. This is the first attempt to investigate low T/W dynamical instabilities as a complete set of the eigenvalue problem. Our equilibrium configuration has "constant" specific angular momentum distribution, which potentially contains a singular solution in the perturbed enthalpy at corotation radius in linear perturbation. We find the unstable normal modes of differentially rotating stars by solving the eigenvalue problem along the equatorial plane of the star, imposing the regularity condition on the center and the vanished enthalpy at the oscillating equatorial surface. We find that the existing pulsation modes become unstable due to the existence of the corotation radius inside the star. The feature of the unstable mode eigenfrequency and its eigenfunction in the linear analysis roughly ...

  20. Calculating rotating hydrodynamic and magneto-hydrodynamic waves to understand magnetic effects on dynamical tides

    CERN Document Server

    Wei, Xing

    2016-01-01

    For understanding magnetic effects on dynamical tides, we study the rotating magneto-hydrodynamic (MHD) flow driven by harmonic forcing. The linear responses are analytically derived in a periodic box under the local WKB approximation. Both the kinetic and Ohmic dissipations at the resonant frequencies are calculated and the various parameters are investigated. Although magnetic pressure may be negligible compared to thermal pressure, magnetic field can be important for the first-order perturbation, e.g. dynamical tides. It is found that magnetic field splits the resonant frequency, namely the rotating hydrodynamic flow has only one resonant frequency but the rotating MHD flow has two, one positive and the other negative. In the weak field regime the dissipations are asymmetric around the two resonant frequencies and this asymmetry is more striking with a weaker magnetic field. It is also found that both the kinetic and Ohmic dissipations at the resonant frequencies are inversely proportional to the Ekman num...

  1. Structural dynamics studies of rotating bladed-disk assemblies coupled with flexible shaft motions

    Science.gov (United States)

    Loewy, R. G.; Khader, N.

    1983-01-01

    In order to analyze the dynamic behavior of the first stage compressor/fan of the 'E3' turbofan engine, a classical structural dynamics approach is employed to couple the motions of a flexible bladed disk to a rotating flexible shaft. The analysis accounts for flexible disk displacements which are transverse to the plane of rotation, and radial as well as tangential, and also accounts for rigid disk translations along, and rotations about, axes normal to the undeformed shaft axes. In the case of a wide range of E3 engine shaft flexibilities and speeds, some of the one-diametral node frequencies are shown to be affected by shaft degrees of freedom whose stiffness values are in general range of design practice. Coriolis forces are also found to significantly affect natural frequencies where strong coupling between certain modes is present.

  2. Dynamic analysis of a rotating rigid-flexible coupled smart structure with large deformations

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on Hamilton's principle, a new kind of fully coupled nonlinear dynamic model for a rotating rigid-flexible smart structure with a tip mass is proposed. The geometrically nonlinear effects of the axial, transverse displacement and rotation angle are considered by means of the first-order approximation coupling (FOAC) model theory, in which large deformations and the centrifugal stiffening effects are considered. Three kinds of systems are established respectively, which are a structure without piezoelectric layer, with piezoelectric layer in open circuit and closed circuit. Several simulations based on simplified models are presented to show the differences in characteristics between structures with and without the tip mass, between smart beams in closed and open circuit, and between the centrifugal effects in high speed rotating state or not. The last simulation calculates the dynamic response of the structure subjected to external electrical loading.

  3. Testing multiple coordination constraints with a novel bimanual visuomotor task.

    Directory of Open Access Journals (Sweden)

    Helene M Sisti

    Full Text Available The acquisition of a new bimanual skill depends on several motor coordination constraints. To date, coordination constraints have often been tested relatively independently of one another, particularly with respect to isofrequency and multifrequency rhythms. Here, we used a new paradigm to test the interaction of multiple coordination constraints. Coordination constraints that were tested included temporal complexity, directionality, muscle grouping, and hand dominance. Twenty-two healthy young adults performed a bimanual dial rotation task that required left and right hand coordination to track a moving target on a computer monitor. Two groups were compared, either with or without four days of practice with augmented visual feedback. Four directional patterns were tested such that both hands moved either rightward (clockwise, leftward (counterclockwise, inward or outward relative to each other. Seven frequency ratios (3∶1, 2∶1, 3∶2, 1∶1, 2∶3. 1∶2, 1∶3 between the left and right hand were introduced. As expected, isofrequency patterns (1∶1 were performed more successfully than multifrequency patterns (non 1∶1. In addition, performance was more accurate when participants were required to move faster with the dominant right hand (1∶3, 1∶2 and 2∶3 than with the non-dominant left hand (3∶1, 2∶1, 3∶2. Interestingly, performance deteriorated as the relative angular velocity between the two hands increased, regardless of whether the required frequency ratio was an integer or non-integer. This contrasted with previous finger tapping research where the integer ratios generally led to less error than the non-integer ratios. We suggest that this is due to the different movement topologies that are required of each paradigm. Overall, we found that this visuomotor task was useful for testing the interaction of multiple coordination constraints as well as the release from these constraints with practice in the presence of

  4. Rotational dynamics of magnetic silica spheres studied by measuring the complex magnetic susceptibility

    NARCIS (Netherlands)

    Claesson, E.M.; Erne, B.H.; Philipse, A.P.

    2007-01-01

    The weak permanent magnetic dipole moment of cobalt ferrite-doped colloidal silica spheres was increased by exposure to a saturating magnetic field. The resulting change of the rotational dynamics of the magnetic microspheres in a weak alternating field was measured from low to high volume fraction

  5. Accuracy of Enskog theory for rotational versus translational motion: A molecular-dynamics study

    NARCIS (Netherlands)

    Talbot, J.; Allen, M.P.; Evans, G.T.; Frenkel, D.; Kivelson, D.

    1989-01-01

    Molecular-dynamics simulations of fluids composed of hard ellipsoids yield translational diffusional coefficients that deviate from the predictions of kinetic theory in the same way, but to a greater degree than, those of hard spheres. Surprisingly, however, the rotational diffusion coefficients are

  6. Spatiotemporal mapping of three dimensional rotational dynamics of single ultrasmall gold nanorods

    Science.gov (United States)

    Chaudhari, Kamalesh; Pradeep, Thalappil

    2014-08-01

    Spatiotemporal mapping of the position and orientation of nano-machinery inside complex and dynamic cellular environments is essential for the detailed understanding of many bio-physical processes. For the genuine observation of such biomolecular dynamics with high signal to noise ratio and reduced disturbance from the labeling probes, reduction in the size of nano-bio labels and simplification of techniques for their observation are important. Here we achieve this using polarized dark field scattering micro-spectroscopy (PDFSMS), in its simplest form so that it is deployable in several experiments. We not only locate tiny gold nanorods (GNRs) of size 30 (length) × 10 nm (diameter) inside HEK293 cells but also demonstrate mapping of their in-situ polarization patterns using a novel method. Real time observations of rotating GNR with DFSMS and PDFSMS are used to resolve in-plane and out-of-plane rotational modes of GNR. We have shown that PDFSMS itself can provide complete information about the state of GNR. A step ahead, we demonstrate the application of PDFSMS to track three dimensional rotational dynamics of transferrin-conjugated GNRs inside live HEK293 cells. These first-time observations of the three dimensional intracellular rotational dynamics of tiny GNRs using PDFSMS present a new landmark in single particle scattering spectroscopy.

  7. Accuracy of Enskog theory for rotational versus translational motion: A molecular-dynamics study

    NARCIS (Netherlands)

    Talbot, J.; Allen, M.P.; Evans, G.T.; Frenkel, D.; Kivelson, D.

    1989-01-01

    Molecular-dynamics simulations of fluids composed of hard ellipsoids yield translational diffusional coefficients that deviate from the predictions of kinetic theory in the same way, but to a greater degree than, those of hard spheres. Surprisingly, however, the rotational diffusion coefficients are

  8. Dynamic moment of inertia of the 192Hg superdeformed band at high rotational frequencies

    Science.gov (United States)

    Lauritsen, T.; Janssens, R. V. F.; Carpenter, M. P.; Moore, E. F.; Ahmad, I.; Fernandez, P. B.; Khoo, T. L.; Kuehner, J. A.; Prevost, D.; Waddington, J. C.; Garg, U.; Reviol, W.; Ye, D.; Drigert, M. W.

    1992-04-01

    The superdeformed band in 192Hg has been extended to higher transition energies from a new analysis of a large set of double and triple coincidence data. Contrary to the results of cranked shell model calculations including monopole pairing, the dynamic moment of inertia I(2) is found to continue to increase with rotational frequency.

  9. Nutrient dynamics throughout the rotation of Eucalyptus clonal stands in Congo.

    Science.gov (United States)

    Laclau, Jean-Paul; Deleporte, Philippe; Ranger, Jacques; Bouillet, Jean-Pierre; Kazotti, Guy

    2003-06-01

    The dynamics of the main nutrient fluxes of the biological cycle were quantified in a clonal Eucalyptus plantation throughout the whole planted crop rotation: current annual requirements of nutrients, uptake from the soil, internal translocations within trees, return to soil (litterfall and crown leaching) and decomposition in the forest floor. As reported for other species, two growth periods were identified in these short-rotation plantations: (1) a juvenile phase up to canopy closure, during which the uptake of nutrients from the soil reserves supplied most of the current requirements; and (2) a second phase up to harvest, characterized by intense nutrient recycling processes. Internal translocation within trees supplied about 30 % of the annual requirements of N and P from 2 years of age onwards, and about 50 % of the K requirement. The mineralization of large amounts of organic matter returned to the soil with litterfall during stand development represented a key process providing nutrients to the stand at the end of the rotation. The importance of the recycling processes was clearly shown by the small amounts of nutrients permanently immobilized in the ligneous components of trees, compared with the total requirements accumulated over the stand rotation which were two to four times higher. Small pools of nutrients circulating quickly in the ecosystem made it possible to produce high amounts of biomass in poor soils. The sustainability of these plantations will require fertilizer inputs that match the changes in soil fertility over successive rotations, mainly linked to the dynamics of organic matter in this tropical soil.

  10. Dynamics of magnetic nanoparticles in a viscous fluid driven by rotating magnetic fields

    Science.gov (United States)

    Usadel, Klaus D.

    2017-03-01

    The rotational dynamics of magnetic nanoparticles in rotating magnetic fields in the presence of thermal noise is studied both theoretically and by performing numerical calculations. Equations for the dynamics of particles with uniaxial magnetic anisotropy are studied and the phase lag between the rotating magnetic moment and the driving field is obtained. It is shown that for large enough anisotropy energy the magnetic moment is locked to the anisotropy axis so that the particle behaves like a rotating magnetic dipole. The corresponding rigid dipole model is analyzed both numerically by solving the appropriate Fokker-Planck equation and analytically by applying an effective field method. In the special case of a rotating magnetic field applied analytic results are obtained in perfect agreement with numerical results based on the Fokker-Planck equation. The analytic formulas derived are not restricted to small magnetic fields or low frequencies and are therefore important for applications. The illustrative numerical calculations presented are performed for magnetic parameters typical for iron oxide.

  11. Superparamagnetic particle dynamics and mixing in a rotating capillary tube with a stationary magnetic field.

    Science.gov (United States)

    Lee, Jun-Tae; Abid, Aamir; Cheung, Ka Ho; Sudheendra, L; Kennedy, Ian M

    2012-09-01

    The dynamics of superparamagnetic particles subject to competing magnetic and viscous drag forces have been examined with a uniform, stationary, external magnetic field. In this approach, competing drag and magnetic forces were created in a fluid suspension of superparamagnetic particles that was confined in a capillary tube; competing viscous drag and magnetic forces were established by rotating the tube. A critical Mason number was determined for conditions under which the rotation of the capillary prevents the formation of chains from individual particles. The statistics of chain length were investigated by image analysis while varying parameters such as the rotation speed and the viscosity of the liquid. The measurements showed that the rate of particle chain formation was decreased with increased viscosity and rotation speed ; the particle dynamics could be quantified by the same dimensionless Mason number that has been demonstrated for rotating magnetic fields. The potential for enhancement of mixing in a bioassay was assessed using a fast chemical reaction that was diffusion-limited. Reducing the Mason below the critical value, so that chains were formed in the fluid, gave rise to a modest improvement in the time to completion of the reaction.

  12. Stable and Unstable Rotational Dynamics of a Smartphone

    Science.gov (United States)

    Loth, Matthew; Gibbons, Chad; Belaiter, Sami; Clarage, James B.

    2017-10-01

    One of the canonical, and memorable, classroom demonstrations from an upper-division mechanics course is to toss a rigid body with three distinct principal moments of inertia into the air, giving it a spin along one of its three principal axes. A student's mechanics textbook itself works great for the body, secured rigidly shut with a rubber band. The book will spin stably about its longest and shortest dimensions, just like a top or gyroscope. What is surprising is that any attempt to spin the book about its intermediate axis (the axis parallel to the book's lines of text) will result in a wildly unstable and chaotic tumbling, which most students find curious enough to warrant staying awake for a subsequent derivation of Euler's equations. However, now that most students read their text "books" off of a tablet or phone, this demonstration may seem outdated. Or is it? Like a textbook, a phone or tablet also has three distinct principal moments. Better still, not only do these solid state devices require no rubber band, but these bodies can collect detailed data on their dynamical state, turning a demonstration into an actual experiment. This article reports the results of this modern version of the classical "book toss" demonstration, fittingly carried out by a team composed of both an old physics professor and a youthful group of three undergraduate students studying physics and engineering.

  13. Dynamic Three-Dimensional Shoulder Mri during Active Motion for Investigation of Rotator Cuff Diseases.

    Directory of Open Access Journals (Sweden)

    Christine Tempelaere

    Full Text Available MRI is the standard methodology in diagnosis of rotator cuff diseases. However, many patients continue to have pain despite treatment, and MRI of a static unloaded shoulder seems insufficient for best diagnosis and treatment. This study evaluated if Dynamic MRI provides novel kinematic data that can be used to improve the understanding, diagnosis and best treatment of rotator cuff diseases.Dynamic MRI provided real-time 3D image series and was used to measure changes in the width of subacromial space, superior-inferior translation and anterior-posterior translation of the humeral head relative to the glenoid during active abduction. These measures were investigated for consistency with the rotator cuff diseases classifications from standard MRI.The study included: 4 shoulders with massive rotator cuff tears, 5 shoulders with an isolated full-thickness supraspinatus tear, 5 shoulders with tendinopathy and 6 normal shoulders. A change in the width of subacromial space greater than 4mm differentiated between rotator cuff diseases with tendon tears (massive cuff tears and supraspinatus tear and without tears (tendinopathy (p = 0.012. The range of the superior-inferior translation was higher in the massive cuff tears group (6.4mm than in normals (3.4mm (p = 0.02. The range of the anterior-posterior translation was higher in the massive cuff tears (9.2 mm and supraspinatus tear (9.3 mm shoulders compared to normals (3.5mm and tendinopathy (4.8mm shoulders (p = 0.05.The Dynamic MRI enabled a novel measure; 'Looseness', i.e. the translation of the humeral head on the glenoid during an abduction cycle. Looseness was better able at differentiating different forms of rotator cuff disease than a simple static measure of relative glenohumeral position.

  14. Dynamic Three-Dimensional Shoulder Mri during Active Motion for Investigation of Rotator Cuff Diseases

    Science.gov (United States)

    Tempelaere, Christine; Pierrart, Jérome; Lefèvre-Colau, Marie-Martine; Vuillemin, Valérie; Cuénod, Charles-André; Hansen, Ulrich; Mir, Olivier; Skalli, Wafa; Gregory, Thomas

    2016-01-01

    Background MRI is the standard methodology in diagnosis of rotator cuff diseases. However, many patients continue to have pain despite treatment, and MRI of a static unloaded shoulder seems insufficient for best diagnosis and treatment. This study evaluated if Dynamic MRI provides novel kinematic data that can be used to improve the understanding, diagnosis and best treatment of rotator cuff diseases. Methods Dynamic MRI provided real-time 3D image series and was used to measure changes in the width of subacromial space, superior-inferior translation and anterior-posterior translation of the humeral head relative to the glenoid during active abduction. These measures were investigated for consistency with the rotator cuff diseases classifications from standard MRI. Results The study included: 4 shoulders with massive rotator cuff tears, 5 shoulders with an isolated full-thickness supraspinatus tear, 5 shoulders with tendinopathy and 6 normal shoulders. A change in the width of subacromial space greater than 4mm differentiated between rotator cuff diseases with tendon tears (massive cuff tears and supraspinatus tear) and without tears (tendinopathy) (p = 0.012). The range of the superior-inferior translation was higher in the massive cuff tears group (6.4mm) than in normals (3.4mm) (p = 0.02). The range of the anterior-posterior translation was higher in the massive cuff tears (9.2 mm) and supraspinatus tear (9.3 mm) shoulders compared to normals (3.5mm) and tendinopathy (4.8mm) shoulders (p = 0.05). Conclusion The Dynamic MRI enabled a novel measure; ‘Looseness’, i.e. the translation of the humeral head on the glenoid during an abduction cycle. Looseness was better able at differentiating different forms of rotator cuff disease than a simple static measure of relative glenohumeral position. PMID:27434235

  15. Humeral elevation reduces the dynamic control ratio of the shoulder muscles during internal rotation.

    Science.gov (United States)

    Howard, William; Burgess, Jonathan; Vrhovnik, Borut; Stringer, Christian; Choy, Sherrie T; Marsden, Jonathan F; Gedikoglou, Ingrid A; Shum, Gary L

    2017-04-01

    To determine the differences in the dynamic control ratio of the glenohumeral joint rotators, during internal rotation at 20° and 60° of humeral elevation in the scapular plan. Dynamic control ratio (DCR) is defined as the ratio between eccentric action of the lateral rotators and the concentric action of the medial rotators. A cross-sectional laboratory study. Thirty asymptomatic participants (men n=14, women n=16, mean age=29.4±8.9years, BMI: 24.1±5.4) were tested. Peak torque generated by the concentric action of the MR and the eccentric action of the LR of the shoulder joint and the DCR were evaluated on the dominant arm using an isokinetic dynamometer at 20° and 60° of humeral elevation at a speed of 20°/s. There was a significant decrease in the DCR at 60° humeral elevation when compared to 20° humeral elevation (p0.05). The significant decrease in the DCR as a consequence of a decrease in the eccentric peak torque of the LR when the humerus is in a more elevated position suggests that the introduction of humeral elevation can be used as a progression for improving the eccentric action of the shoulder LR and subsequently the dynamic control of the shoulder. Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

  16. Carbon dynamics of intensively managed forest along a full rotation

    Science.gov (United States)

    Moreaux, V.; Bosc, A.; Bonnefond, J.; Burlett, R.; Lamaud, E.; Sartore, M.; Trichet, P.; Chipeaux, C.; Lambrot, C.; Kowalski, A. S.; Loustau, D.

    2012-12-01

    Temperate and tropical forests are increasingly exploited for wood and biomass extraction and only one third of forest area was considered as primary in the recent FRA in 2010. Management practices affect the soil-forest-atmosphere continuum through various effects on soil and surface properties. They result ultimately in either positive or negative changes in the biomass and soil carbon pools but, if any, few datasets or modeling tools are available for quantifying their impacts on the net carbon balance of forest stands. To analyse these effects, the net half-hourly fluxes of CO2, water vapour and heat exchanges were monitored for 23 years in two closed stands of maritime pines in southwestern France. Carbon content of the aboveground biomass was measured annually and soil pools 10-early in the younger stand and 5-yearly in the mature stand. For analysing the data collected and disentangling the climate and management effects, we used the three components process-based model GRAECO+ (Loustau et al. this session) linking a 3D radiative transfer and photosynthesis model, MAESTRA, a soil carbon model adapted from ROTH-C and a plant growth model. Eddy flux data were processed, gapfilled and partitioned using the methodological recommendations (Aubinet et al. 2000, Adv. Eco. Res:30, 114-173, Falge et al. 2001, Agr. For. Meteo. : 107, 43-69, Reichstein et al. 2005, Glob. Change Biol., 11:1424-1439). Analysis of the sequence showed that, whether by an increased sensitivity to soil drought compared to the pines or by a rapid re-colonization of the inter-row after understorey removal and plowing, the weeded vegetation contributed to create specific intra-annual dynamics of the fluxes and therefore, controls the dynamics of carbon balance of the stand. After three growing seasons, the stand was already a carbon sink, but the impact of thinning and weeded vegetation removal at the age of 5-year brought the balance to almost neutral. We interpret this change as the combined

  17. Dynamics of arbitrary shaped propellers driven by a rotating magnetic field

    Science.gov (United States)

    Morozov, Konstantin I.; Mirzae, Yoni; Kenneth, Oded; Leshansky, Alexander M.

    2017-04-01

    Motion in fluids at the micro(nano)metric scale is dominated by viscosity. One efficient propulsion method relies on a weak uniform rotating magnetic field that drives a chiral object. From bacterial flagella to artificial magnetic micro- or nanohelices, rotation of a corkscrew is considered as a universally efficient propulsion gait in viscous environments. However, recent experimental studies have demonstrated that geometrically achiral microscale objects or random-shaped magnetic aggregates can propel similarly to helical micromotors. Although approximate theories concerning dynamics of helical magnetic propellers are available, propulsion of achiral particles or objects with complex shapes is not understood. Here we present a general theory of rotation and propulsion of magnetized object of arbitrary shape driven by a rotating magnetic field. Intrinsic symmetries of the viscous mobility tensors yield compact classification of stable rotational states depending on the orientation of the magnetic moment with respect to principal rotation axes of the object. Propulsion velocity can be written in terms of geometry-dependent chirality matrix Ch , where both the diagonal elements (owing to orientation-dependent handedness) and off-diagonal entries (that do not necessitate handedness) contribute in a similar way. In general, the theory anticipates multiplicity of stable rotational states corresponding to two (complimentary to π ) angles the magnetization forms with the field rotation axis. Thus, two identical magnetic objects may propel with different speeds or even in opposite directions. However, for a class of simple achiral objects, there is a particular magnetization whereas the pair of symmetric rotational states gives rise to a unique chiral-like propulsion gait, closely resembling that of an ideal helical propeller. In other words, a geometrically achiral object can acquire apparent chirality due to its interaction with the external magnetic field. The

  18. Development and applications of single particle orientation and rotational tracking in dynamic systems

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Kuangcai [Iowa State Univ., Ames, IA (United States)

    2016-02-19

    The goal of this study is to help with future data analysis and experiment designs in rotational dynamics research using DIC-based SPORT technique. Most of the current studies using DIC-based SPORT techniques are technical demonstrations. Understanding the mechanisms behind the observed rotational behaviors of the imaging probes should be the focus of the future SPORT studies. More efforts are still needed in the development of new imaging probes, particle tracking methods, instrumentations, and advanced data analysis methods to further extend the potential of DIC-based SPORT technique.

  19. A DYNAMIC MODEL FOR A DISC EXCITED BY VERTICALLY MISALIGNED, ROTATING, FRICTIONAL SLIDERS

    Institute of Scientific and Technical Information of China (English)

    OUYANG Huajiang; GU Yuanxian; YANG Haitian

    2004-01-01

    This paper presents a dynamic model for a disc subjected to two sliders rotating in the circumferential direction over the top and bottom surfaces of the disc. The two sliders are vertically misaligned and each is a mass-spring-damper system with friction between the slider and the disc.The moving loads produced by misaligned sliders can destabilise the whole system. Stability analysis is carried out in a simulated example. This model is meant to explain the friction mechanism for generating unstable vibration in many applications involving rotating discs.

  20. Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

    Energy Technology Data Exchange (ETDEWEB)

    Guntur, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Schreck, S. [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sorensen, N. N. [Technical Univ. of Denmark, Lyngby (Denmark); Bergami, L. [Technical Univ. of Denmark, Lyngby (Denmark)

    2015-04-22

    It is well known that airfoils under unsteady flow conditions with a periodically varying angle of attack exhibit aerodynamic characteristics different from those under steady flow conditions, a phenomenon commonly known as dynamic stall. It is also well known that the steady aerodynamic characteristics of airfoils in the inboard region of a rotating blade differ from those under steady two-dimensional (2D) flow conditions, a phenomenon commonly known as rotational augmentation. This paper presents an investigation of these two phenomena together in the inboard parts of wind turbine blades. This analysis is carried out using data from three sources: (1) the National Renewable Energy Laboratory’s Unsteady Aerodynamics Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation, (2) data from unsteady Delayed Detached Eddy Simulations (DDES) carried out using the Technical University of Denmark’s in-house flow solver Ellipsys3D, and (3) data from a simplified model based on the blade element momentum method with a dynamic stall subroutine that uses rotationally augmented steady-state polars obtained from steady Phase VI experimental sequences, instead of the traditional 2D nonrotating data. The aim of this work is twofold. First, the blade loads estimated by the DDES simulations are compared to three select cases of the N sequence experimental data, which serves as a validation of the DDES method. Results show reasonable agreement between the two data in two out of three cases studied. Second, the dynamic time series of the lift and the moment polars obtained from the experiments are compared to those from the dynamic stall subroutine that uses the rotationally augmented steady polars. This allowed the differences between the stall phenomenon on the inboard parts of harmonically pitching blades on a rotating wind turbine and the classic dynamic stall representation in 2D flow to be

  1. Extracting full-field dynamic strain response of a rotating wind turbine using photogrammetry

    Science.gov (United States)

    Baqersad, Javad; Poozesh, Peyman; Niezrecki, Christopher; Avitabile, Peter

    2015-04-01

    Health monitoring of wind turbines is typically performed using conventional sensors (e.g. strain-gages and accelerometers) that are usually mounted to the nacelle or gearbox. Although many wind turbines stop operating due to blade failures, there are typically few to no sensor mounted on the blades. Placing sensors on the rotating parts of the structure is a challenge due to the wiring and data transmission constraints. Within the current work, an approach to monitor full-field dynamic response of rotating structures (e.g. wind turbine blades or helicopter rotors) is developed and experimentally verified. A wind turbine rotor was used as the test structure and was mounted to a block and horizontally placed on the ground. A pair of bearings connected to the rotor shaft allowed the turbine to freely spin along the shaft. Several optical targets were mounted to the blades and a pair of high-speed cameras was used to monitor the dynamics of the spinning turbine. Displacements of the targets during rotation were measured using three-dimensional point tracking. The point tracking technique measured both rigid body displacement and flexible deformation of the blades at target locations. While the structure is rotating, only flap displacements of optical targets (displacements out of the rotation plane) were used in strain prediction process. The measured displacements were expanded and applied to the finite element model of the turbine to extract full-field dynamic strain on the structure. The proposed approach enabled the prediction of dynamic response on the outer surface as well as within the inner points of the structure where no other sensor could be easily mounted. In order to validate the proposed approach, the predicted strain was compared to strain measured at four locations on the spinning blades using a wireless strain-gage system.

  2. Visuomotor transformations for eye-hand coordination.

    Science.gov (United States)

    Henriques, D Y P; Medendorp, W P; Khan, A Z; Crawford, J D

    2002-01-01

    In recent years the scientific community has come to appreciate that the early cortical representations for visually guided arm movements are probably coded in a visual frame, i.e. relative to retinal landmarks. While this scheme accounts for many behavioral and neurophysiological observations, it also poses certain problems for manual control. For example, how are these oculocentric representations updated across eye movements, and how are they then transformed into useful commands for accurate movements of the arm relative to the body? Also, since we have two eyes, which is used as the reference point in eye-hand alignment tasks like pointing? We show that patterns of errors in human pointing suggest that early oculocentric representations for arm movement are remapped relative to the gaze direction during each saccade. To then transform these oculocentric representations into useful commands for accurate movements of the arm relative to the body, the brain correctly incorporates the three-dimensional, rotary geometry of the eyes when interpreting retinal images. We also explore the possibility that the eye-hand coordination system uses a strategy like ocular dominance, but switches alignment between the left and right eye in order to maximize eye-hand coordination in the best field of view. Finally, we describe the influence of eye position on eye-hand alignment, and then consider how head orientation influences the linkage between oculocentric visual frames and bodycentric motor frames. These findings are framed in terms of our 'conversion-on-demand' model, which suggests a virtual representation of egocentric space, i.e. one in which only those representations selected for action are put through the complex visuomotor transformations required for interaction with actual objects in personal space.

  3. Absence of spatial updating when the visuomotor system is unsure about stimulus motion.

    Science.gov (United States)

    Van Barneveld, Denise C P B M; Kiemeneij, Anne C M; Van Opstal, A John

    2011-07-20

    How does the visuomotor system decide whether a target is moving or stationary in space or whether it moves relative to the eyes or head? A visual flash during a rapid eye-head gaze shift produces a brief visual streak on the retina that could provide information about target motion, when appropriately combined with eye and head self-motion signals. Indeed, double-step experiments have demonstrated that the visuomotor system incorporates actively generated intervening gaze shifts in the final localization response. Also saccades to brief head-fixed flashes during passive whole-body rotation compensate for vestibular-induced ocular nystagmus. However, both the amount of retinal motion to invoke spatial updating and the default strategy in the absence of detectable retinal motion remain unclear. To study these questions, we determined the contribution of retinal motion and the vestibular canals to spatial updating of visual flashes during passive whole-body rotation. Head- and body-restrained humans made saccades toward very brief (0.5 and 4 ms) and long (100 ms) visual flashes during sinusoidal rotation around the vertical body axis in total darkness. Stimuli were either attached to the chair (head-fixed) or stationary in space and were always well localizable. Surprisingly, spatial updating only occurred when retinal stimulus motion provided sufficient information: long-duration stimuli were always appropriately localized, thus adequately compensating for vestibular nystagmus and the passive head movement during the saccade reaction time. For the shortest stimuli, however, the target was kept in retinocentric coordinates, thus ignoring intervening nystagmus and passive head displacement, regardless of whether the target was moving with the head or not.

  4. The effect of visuomotor adaptation on proprioceptive localization: the contributions of perceptual and motor changes.

    Science.gov (United States)

    Clayton, Holly A; Cressman, Erin K; Henriques, Denise Y P

    2014-07-01

    Reaching movements are rapidly adapted following training with rotated visual feedback of the hand (motor recalibration). Our laboratory has also found that visuomotor adaptation results in changes in estimates of felt hand position (proprioceptive recalibration) in the direction of the visuomotor distortion (Cressman and Henriques 2009, 2010; Cressman et al. 2010). In the present study, we included an additional method for measuring hand proprioception [specifically, proprioceptive-guided reaches of the unadapted (left) hand to the robot-guided adapted (right) hand-target] and compared this with our original perceptual task (estimating the felt hand position of the adapted hand relative to visual reference markers/the body midline), as well as to no-cursor reaches with the adapted hand (reaching to visual and midline-targets), to better identify whether changes in reaching following adaptation to a 50° rightward-rotated cursor reflect sensory or motor processes. Results for the proprioceptive estimation task were consistent with previous findings; subjects felt their hand to be aligned with a reference marker when it was shifted approximately 4° more in the direction of the visuomotor distortion following adaptation compared with baseline conditions. Moreover, we found similar changes in the proprioceptive-guided reaching task such that subjects misreached 5° in the direction of the cursor rotation. However, these results were true only for proprioceptive-guided reaches to the adapted hand, as reaches to the body midline were not affected by adaptation. This suggests that proprioceptive recalibration is restricted to the adapted hand and does not generalize to the rest of the body; this truly reflects a change in the sensory representation of the hand rather than changes in the motor program. This is in contrast to no-cursor reaches made with the adapted hand, which show reach after-effects for both visual targets and the midline, suggesting that reaches with

  5. Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

    Institute of Scientific and Technical Information of China (English)

    James Q. Feng; C. F. Gallo

    2011-01-01

    We present an efficient,robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies.With appropriate mathematical treatments,the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed.Using a boundary element discretization procedure,the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further iterations.The numerical code implemented according to our algorithm can accurately determine the surface mass density distribution in a disk galaxy from a measured rotation curve (or vice versa).For a disk galaxy with a typical fiat rotation curve,our modeling results show that the surface mass density monotonically decreases from the galactic center toward the periphery,according to Newtonian dynamics.In a large portion of the galaxy,the surface mass density follows an approximately exponential law of decay with respect to the galactic radial coordinate.Yet the radial scale length for the surface mass density seems to be generally larger than that of the measured brightness distribution,suggesting an increasing mass-to- light ratio with the radial distance in a disk galaxy.In a nondimensionalized form,our mathematical system contains a dimensionless parameter which we call the “galactic rotation number” that represents the gross ratio of centrifugal force and gravitational force.The value of this galactic rotation number is determined as part of the numerical solution.Through a systematic computational analysis,we have illustrated that the galactic rotation number remains within ±10% of 1.70 for a wide variety of rotation curves.This implies that the total mass in a disk galaxy is proportional to V(0)2 Rg,with V(0) denoting the characteristic rotation velocity (such as the “fiat” value in a typical rotation curve) and Rg the radius of the galactic

  6. An improved dynamic subgrid-scale model and its application to large eddy simulation of rotating channel flows

    Institute of Scientific and Technical Information of China (English)

    LIU; Nansheng; LU; Xiyun; ZHUANG; Lixian

    2004-01-01

    A new dynamic subgrid-scale (SGS) model, which is proved to satisfy the principle of asymptotic material frame indifference (AMFI) for rotating turbulence, is proposed based on physical and mathematical analysis. Comparison with direct numerical simulation (DNS) results verifies that the new SGS model is effective for large eddy simulation (LES) on rotating turbulent flow. The SGS model is then applied to the LES of the spanwise rotating turbulent channel flow to investigate the rotation effect on turbulence characteristics, budget terms in the transport equations of resolved Reynolds stresses, and flow structures near the wall regions of the rotating channel.

  7. Effect of Target Location on Dynamic Visual Acuity During Passive Horizontal Rotation

    Science.gov (United States)

    Appelbaum, Meghan; DeDios, Yiri; Kulecz, Walter; Peters, Brian; Wood, Scott

    2010-01-01

    The vestibulo-ocular reflex (VOR) generates eye rotation to compensate for potential retinal slip in the specific plane of head movement. Dynamic visual acuity (DVA) has been utilized as a functional measure of the VOR. The purpose of this study was to examine changes in accuracy and reaction time when performing a DVA task with targets offset from the plane of rotation, e.g. offset vertically during horizontal rotation. Visual acuity was measured in 12 healthy subjects as they moved a hand-held joystick to indicate the orientation of a computer-generated Landolt C "as quickly and accurately as possible." Acuity thresholds were established with optotypes presented centrally on a wall-mounted LCD screen at 1.3 m distance, first without motion (static condition) and then while oscillating at 0.8 Hz (DVA, peak velocity 60 deg/s). The effect of target location was then measured during horizontal rotation with the optotypes randomly presented in one of nine different locations on the screen (offset up to 10 deg). The optotype size (logMar 0, 0.2 or 0.4, corresponding to Snellen range 20/20 to 20/50) and presentation duration (150, 300 and 450 ms) were counter-balanced across five trials, each utilizing horizontal rotation at 0.8 Hz. Dynamic acuity was reduced relative to static acuity in 7 of 12 subjects by one step size. During the random target trials, both accuracy and reaction time improved proportional to optotype size. Accuracy and reaction time also improved between 150 ms and 300 ms presentation durations. The main finding was that both accuracy and reaction time varied as a function of target location, with greater performance decrements when acquiring vertical targets. We conclude that dynamic visual acuity varies with target location, with acuity optimized for targets in the plane of motion. Both reaction time and accuracy are functionally relevant DVA parameters of VOR function.

  8. Polarity and Nonpolarity of Ionic Liquids Viewed from the Rotational Dynamics of Carbon Monoxide.

    Science.gov (United States)

    Yasaka, Y; Kimura, Y

    2015-12-17

    The rotational dynamics of carbon monoxide (CO) in a molten salt, ionic liquids (ILs), and alkanes were investigated by (17)O NMR T1 measurements using labeled C(17)O. The molten salt and the studied ILs have the bis(trifluoromethanesulfonyl)imide anion ([NTf2](-)) in common. In hexane near room temperature, the rotational relaxation times are close to the values predicted from the slip boundary condition in the Stokes-Einstein-Debye (SED) theory. However, in contradiction to the theoretical prediction, the rotational relaxation times decrease as the value of η/T increases, where η and T are the viscosity and absolute temperature, respectively. In other alkanes and ILs used in this study, the rotational relaxation times are much faster than those predicted by SED, and show a unique dependence on the number of alkyl carbons. For the same value of η/T, the CO rotational relaxation times in ILs composed of short-alkyl-chain-length imidazolium cations (1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium) are close to those for a molten salt (Cs[NTf2]). On the other hand, the rotational relaxation times in ILs composed of long-chain-length imidazolium (1-methyl-3-octylimidazolium) and phosphonium (tributylmethylphosphonium and tetraoctylphosphonium) cations are much shorter than the SED predictions. This deviation from theory increases as the alkyl chain length increases. We also found that the rotational relaxation times in dodecane and squalane are similar to those in ILs with a similar number of alkyl carbons. These results are discussed in terms of heterogeneous solvation and in comparison with the translational diffusion of CO in ILs.

  9. Post-Transition State Dynamics in Gas Phase Reactivity: Importance of Bifurcations and Rotational Activation.

    Science.gov (United States)

    Martín-Sómer, Ana; Yáñez, Manuel; Hase, William L; Gaigeot, Marie-Pierre; Spezia, Riccardo

    2016-03-01

    Beyond the established use of thermodynamic vs kinetic control to explain chemical reaction selectivity, the concept of bifurcations on a potential energy surface (PES) is proving to be of pivotal importance with regard to selectivity. In this article, we studied by means of post-transition state (TS) direct dynamics simulations the effect that vibrational and rotational excitation at the TS may have on selectivity on a bifurcating PES. With this aim, we studied the post-TS unimolecular reactivity of the [Ca(formamide)](2+) ion, for which Coulomb explosion and neutral loss reactions compete. The PES exhibits different kinds of nonintrinsic reaction coordinate (IRC) dynamics, among them PES bifurcations, which direct the trajectories to multiple reaction paths after passing the TS. Direct dynamics simulations were used to distinguish between the bifurcation non-IRC dynamics and non-IRC dynamics arising from atomistic motions directing the trajectories away from the IRC. Overall, we corroborated the idea that kinetic selectivity often does not reduce to a simple choice between paths with different barrier heights and instead dynamical behavior after passing the TS may be crucial. Importantly, rotational excitation may play a pivotal role on the reaction selectivity favoring nonthermodynamic products.

  10. Dynamics of rotationally fissioned asteroids: Source of observed small asteroid systems

    Science.gov (United States)

    Jacobson, Seth A.; Scheeres, Daniel J.

    2011-07-01

    We present a model of near-Earth asteroid (NEA) rotational fission and ensuing dynamics that describes the creation of synchronous binaries and all other observed NEA systems including: doubly synchronous binaries, high- e binaries, ternary systems, and contact binaries. Our model only presupposes the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, "rubble pile" asteroid geophysics, and gravitational interactions. The YORP effect torques a "rubble pile" asteroid until the asteroid reaches its fission spin limit and the components enter orbit about each other (Scheeres, D.J. [2007]. Icarus 189, 370-385). Non-spherical gravitational potentials couple the spin states to the orbit state and chaotically drive the system towards the observed asteroid classes along two evolutionary tracks primarily distinguished by mass ratio. Related to this is a new binary process termed secondary fission - the secondary asteroid of the binary system is rotationally accelerated via gravitational torques until it fissions, thus creating a chaotic ternary system. The initially chaotic binary can be stabilized to create a synchronous binary by components of the fissioned secondary asteroid impacting the primary asteroid, solar gravitational perturbations, and mutual body tides. These results emphasize the importance of the initial component size distribution and configuration within the parent asteroid. NEAs may go through multiple binary cycles and many YORP-induced rotational fissions during their approximately 10 Myr lifetime in the inner Solar System. Rotational fission and the ensuing dynamics are responsible for all NEA systems including the most commonly observed synchronous binaries.

  11. Interactions between grain boundary faceting, migration and grain rotation: Color group and molecular dynamics simulation approaches

    Science.gov (United States)

    Huang, Yue

    Color group theory and molecular dynamics (MD) simulations were used to study the faceting and rotation of grains in nanocrystalline materials and their interactions. Color group arguments were used to determine symmetry-dictated extrema with respect to misorientation of the grains and with respect to grain boundary normal orientations. MD simulations were used to study the evolution of the system and to elucidate the interactions between grain rotation and faceting in nano-scale systems. The systems of study were fcc bicrystalline systems with two grains sharing their [110] directions. Two geometric parameters were studied: the misorientation between two grains with a common rotation axis in the [110] direction of both grains, and the grain boundary normal orientation of fcc (110) tilt grain boundaries. The symmetry-dictated extremum (SDE) with respect to misorientation around both grains' [110] direction is 90 degrees. The SDE with respect to GB normal orientations for (110) tilt GBs are located on top of the color and classical mirror planes of their dichromatic patterns. By using periodic boundary conditions and a cylindrical embedded grain structure in our simulations, grains are only free to vary the misorientation between grains around the common [110] direction, and the normal of the grain boundaries are always perpendicular to both grains [110] direction. All SDE studied in our simulation are observed to be local energy minimum states. We observed the systems reducing their excess energy through three main modes: forming facets at the boundaries, rotating between the two grains, and reduction of grain boundary area through grain shrinkage. Facets are formed in low-energy grain boundaries and oscillating rotation occurred when the initial misorientation was not a SDE. A new algorithm was developed to quantitatively measure the grain rotation. The ovsered rotations are not rigid-body rotations and have strong interaction with faceting. Systems with lower

  12. Mathematical problems of the dynamics of incompressible fluid on a rotating sphere

    CERN Document Server

    Skiba, Yuri N

    2017-01-01

    This book presents selected mathematical problems involving the dynamics of a two-dimensional viscous and ideal incompressible fluid on a rotating sphere. In this case, the fluid motion is completely governed by the barotropic vorticity equation (BVE), and the viscosity term in the vorticity equation is taken in its general form, which contains the derivative of real degree of the spherical Laplace operator. This work builds a bridge between basic concepts and concrete outcomes by pursuing a rich combination of theoretical, analytical and numerical approaches, and is recommended for specialists developing mathematical methods for application to problems in physics, hydrodynamics, meteorology and geophysics, as well for upper undergraduate or graduate students in the areas of dynamics of incompressible fluid on a rotating sphere, theory of functions on a sphere, and flow stability.

  13. PMMA/PMMA core-shell particles with ellipsoidal, fluorescent cores: accessing rotational dynamics.

    Science.gov (United States)

    Klein, Matthias K; Klinkenberg, Nele; Schuetter, Stefan; Saenger, Nicolai; Pfleiderer, Patrick; Zumbusch, Andreas

    2015-03-10

    For several decades, nonaqueous dispersions of PMMA particles have played an important role in colloid research. They have found application as colloidal model systems, which are used to probe glassy dynamics or to explore crystal nucleation. To date, most research has focused on spherical particles, in which only translational motion can be investigated. Recently, however, there has been a surge of interest in analyzing also rotational dynamics. In this contribution, we introduce a new class of core-shell particles, which can be used as rotational probes. The colloids described herein are composed of shape anisotropic, fluorescent cores covered with nonfluorescent PMMA shells. The core-shell particles are built up in four steps. In a first step, we produce fluorescent and photo-cross-linkable PMMA colloids. In the second step, these particles are thermomechanically elongated and fixed in defined ellipsoidal shapes by photo-cross-linking. Subsequently, we cover the cross-linked, fluorescent core with a nonfluorescent PMMA shell. The shape of the resulting core-shell colloids is tunable between the initial anisotropic and perfect spherical shape. For shaping, we apply a simple solvent swelling procedure. As one option, this method yields perfect PMMA spheres with ellipsoidal, fluorescent centers. We also report morphological particle characterization using various fluorescence microscopy techniques. Finally, we demonstrate that the rotational dynamics of individual colloids can be tracked and analyzed.

  14. Exploring Visuomotor Priming Following Biological and Non-Biological Stimuli

    Science.gov (United States)

    Gowen, E.; Bradshaw, C.; Galpin, A.; Lawrence, A.; Poliakoff, E.

    2010-01-01

    Observation of human actions influences the observer's own motor system, termed visuomotor priming, and is believed to be caused by automatic activation of mirror neurons. Evidence suggests that priming effects are larger for biological (human) as opposed to non-biological (object) stimuli and enhanced when viewing stimuli in mirror compared to…

  15. Exploring Visuomotor Priming Following Biological and Non-Biological Stimuli

    Science.gov (United States)

    Gowen, E.; Bradshaw, C.; Galpin, A.; Lawrence, A.; Poliakoff, E.

    2010-01-01

    Observation of human actions influences the observer's own motor system, termed visuomotor priming, and is believed to be caused by automatic activation of mirror neurons. Evidence suggests that priming effects are larger for biological (human) as opposed to non-biological (object) stimuli and enhanced when viewing stimuli in mirror compared to…

  16. Exploration and Exploitation in Visuomotor Prediction of Autonomous Agents

    NARCIS (Netherlands)

    Bliek, L.

    2013-01-01

    This paper discusses various techniques to let an agent learn how to predict the effects of its own actions on its sensor data autonomously, and their usefulness to apply them to visual sensors. An Extreme Learning Machine is used for visuomotor prediction, while various autonomous control

  17. On the mechanical characterization and modeling of polymer gel brain substitute under dynamic rotational loading.

    Science.gov (United States)

    Fontenier, B; Hault-Dubrulle, A; Drazetic, P; Fontaine, C; Naceur, H

    2016-10-01

    The use of highly sensitive soft materials has become increasingly apparent in the last few years in numerous industrial fields, due to their viscous and damping nature. Unfortunately these materials remain difficult to characterize using conventional techniques, mainly because of the very low internal forces supported by these materials especially under high strain-rates of deformation. The aim of this work is to investigate the dynamic response of a polymer gel brain analog material under specific rotational-impact experiments. The selected polymer gel commercially known as Sylgard 527 has been studied using a specific procedure for its experimental characterization and numerical modeling. At first an indentation experiment was conducted at several loading rates to study the strain rate sensitivity of the Sylgard 527 gel. During the unloading several relaxation tests were performed after indentation, to assess the viscous behavior of the material. A specific numerical procedure based on moving least square approximation and response surface method was then performed to determine adequate robust material parameters of the Sylgard 527 gel. A sensitivity analysis was assessed to confirm the robustness of the obtained material parameters. For the validation of the obtained material model, a second experiment was conducted using a dynamic rotational loading apparatus. It consists of a metallic cylindrical cup filled with the polymer gel and subjected to an eccentric transient rotational impact. Complete kinematics of the cup and the large strains induced in the Sylgard 527 gel, have been recorded at several patterns by means of optical measurement. The whole apparatus was modeled by the Finite Element Method using explicit dynamic time integration available within Ls-dyna(®) software. Comparison between the physical and the numerical models of the Sylgard 527 gel behavior under rotational choc shows excellent agreements.

  18. High-Frequency Dynamic Nuclear Polarization in the Nuclear Rotating Frame

    DEFF Research Database (Denmark)

    Farrar, C. T.; Hall, D. A.; Gerfen, G. J.

    2000-01-01

    A proton dynamic nuclear polarization (DNP) NMR signal enhancement (ϵ) close to thermal equilibrium, ϵ = 0.89, has been obtained at high field (B0 = 5 T, νepr = 139.5 GHz) using 15 mM trityl radical in a 40:60 water/glycerol frozen solution at 11 K. The electron-nuclear polarization transfer...... is performed in the nuclear rotating frame with microwave irradiation during a nuclear spin-lock pulse. The growth of the signal enhancement is governed by the rotating frame nuclear spin–lattice relaxation time (T1ρ), which is four orders of magnitude shorter than the nuclear spin–lattice relaxation time (T1n......). Due to the rapid polarization transfer in the nuclear rotating frame the experiment can be recycled at a rate of 1/T1ρ and is not limited by the much slower lab frame nuclear spin–lattice relaxation rate (1/T1n). The increased repetition rate allowed in the nuclear rotating frame provides an effective...

  19. SLOWLY ROTATING GAS-RICH GALAXIES IN MODIFIED NEWTONIAN DYNAMICS (MOND)

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Salcedo, F. J.; Martinez-Garcia, E. E. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, 04510 Mexico City (Mexico); Hidalgo-Gamez, A. M., E-mail: jsanchez@astro.unam.mx [Departamento de Fisica, Escuela Superior de Fisica y Matematicas, IPN, U.P. Adolfo Lopez Mateos, C.P. 07738, Mexico City (Mexico)

    2013-03-15

    We have carried out a search for gas-rich dwarf galaxies that have lower rotation velocities in their outskirts than MOdified Newtonian Dynamics (MOND) predicts, so that the amplitude of their rotation curves cannot be fitted by arbitrarily increasing the mass-to-light ratio of the stellar component or by assuming additional undetected matter. With presently available data, the gas-rich galaxies UGC 4173, Holmberg II, ESO 245-G05, NGC 4861, and ESO 364-G029 deviate most from MOND predictions and, thereby, provide a sample of promising targets in testing the MOND framework. In the case of Holmberg II and NGC 4861, we find that their rotation curves are probably inconsistent with MOND, unless their inclinations and distances differ significantly from the nominal ones. The galaxy ESO 364-G029 is a promising target because its baryonic mass and rotation curve are similar to Holmberg II but presents a higher inclination. Deeper photometric and H I observations of ESO 364-G029, together with further decreasing systematic uncertainties, may provide a strong test to MOND.

  20. Asymptotic theory of gravity modes in rotating stars. I. Ray dynamics

    Science.gov (United States)

    Prat, V.; Lignières, F.; Ballot, J.

    2016-03-01

    Context. The seismology of early-type stars is limited by our incomplete understanding of gravito-inertial modes. Aims: We develop a short-wavelength asymptotic analysis for gravito-inertial modes in rotating stars. Methods: The Wentzel-Kramers-Brillouin approximation was applied to the equations governing adiabatic small perturbations about a model of a uniformly rotating barotropic star. Results: A general eikonal equation, including the effect of the centrifugal deformation, is derived. The dynamics of axisymmetric gravito-inertial rays is solved numerically for polytropic stellar models of increasing rotation and analysed by describing the structure of the phase space. Three different types of phase-space structures are distinguished. The first type results from the continuous evolution of structures of the non-rotating integrable phase space. It is predominant in the low-frequency region of the phase space. The second type of structures are island chains associated with stable periodic rays. The third type of structures are large chaotic regions that can be related to the envelope minimum of the Brunt-Väisälä frequency. Conclusions: Gravito-inertial modes are expected to follow this classification, in which the frequency spectrum is a superposition of sub-spectra associated with these different types of phase-space structures. The detailed confrontation between the predictions of this ray-based asymptotic theory and numerically computed modes will be presented in a companion paper.

  1. Modeling and Dynamical Behavior of Rotating Composite Shafts with SMA Wires

    Directory of Open Access Journals (Sweden)

    Yongsheng Ren

    2014-01-01

    Full Text Available A dynamical model is developed for the rotating composite shaft with shape-memory alloy (SMA wires embedded in. The rotating shaft is represented as a thin-walled composite of circular cross-section with SMA wires embedded parallel to shaft’s longitudinal axis. A thermomechanical constitutive equation of SMA proposed by Brinson is employed and the recovery stress of the constrained SMA wires is derived. The equations of motion are derived based on the variational-asymptotical method (VAM and Hamilton’s principle. The partial differential equations of motion are reduced to the ordinary differential equations of motion by using the Galerkin method. The model incorporates the transverse shear, rotary inertia, and anisotropy of composite material. Numerical results of natural frequencies and critical speeds are obtained. It is shown that the natural frequencies of the nonrotating shaft and the critical rotating speed increase as SMA wire fraction and initial strain increase and the increase in natural frequencies becomes more significant as SMA wire fraction increases. The initial strain of SMA wires appears to have marginal effect on dynamical behaviors of the shaft. The actuation performance of SMA wires is found to be closely related to the ply-angle.

  2. SINFONI Integral Field Spectroscopy of z~2 UV-selected Galaxies: Rotation Curves and Dynamical Evolution

    CERN Document Server

    Förster-Schreiber, N M; Bouche, N; Davies, R; Eisenhauer, F; Erb, D K; Genzel, R; Gilbert, A; Gillessen, S; Lehnert, M D; Lutz, D; Nesvadba, N; Shapley, A E; Steidel, C C; Sternberg, A; Tacconi, L J; Verma, A

    2006-01-01

    We present 0.5" resolution near-IR integral field spectroscopy of the Ha line emission of 14 z~2 UV-selected BM/BX galaxies obtained with SINFONI at ESO/VLT. The mean Ha half-light radius r_1/2 is about 4kpc and line emission is detected over > ~20kpc in several sources. In 9 sources, we detect spatially-resolved velocity gradients, from 40 to 410 km/s over ~10kpc. The observed kinematics of the larger systems are consistent with orbital motions. Four galaxies are well described by rotating disks with clumpy morphologies and we extract rotation curves out to radii > ~10kpc. One or two galaxies exhibit signatures more consistent with mergers. Analyzing all 14 galaxies in the framework of rotating disks, we infer mean inclination- and beam-corrected maximum circular velocities v_c of 180+-90 km/s and dynamical masses of (0.5-25)x10^10 Msun within r_1/2. On average, the dynamical masses are consistent with photometric stellar masses assuming a Chabrier/Kroupa IMF but too small for a 0.1-100 Msun Salpeter IMF. Th...

  3. Transient Dynamic Response of Delaminated Composite Rotating Shallow Shells Subjected to Impact

    Directory of Open Access Journals (Sweden)

    Amit Karmakar

    2006-01-01

    Full Text Available In this paper a transient dynamic finite element analysis is presented to study the response of delaminated composite pretwisted rotating shallow shells subjected to low velocity normal impact. Lagrange's equation of motion is used to derive the dynamic equilibrium equation and moderate rotational speeds are considered wherein the Coriolis effect is negligible. An eight noded isoparametric plate bending element is employed in the finite element formulation incorporating rotary inertia and effects of transverse shear deformation based on Mindlin's theory. To satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front a multipoint constraint algorithm is incorporated which leads to unsymmetric stiffness matrices. The modified Hertzian contact law which accounts for permanent indentation is utilized to compute the contact force, and the time dependent equations are solved by Newmark's time integration algorithm. Parametric studies are performed in respect of location of delamination, angle of twist and rotational speed for centrally impacted graphite-epoxy composite cylindrical shells.

  4. Dynamic Response of Wind Turbines to Theoretical 3D Seismic Motions Taking into Account the Rotational Component

    OpenAIRE

    Hermanns, Lutz Karl Heinz; Santoyo, M.A.; Quiros, L.E.; Vega Domínguez, Jaime; Gaspar Escribano, Jorge M.; Benito Oterino, Belen

    2011-01-01

    We study the dynamic response of a wind turbine structure subjected to theoretical seismic motions, taking into account the rotational component of ground shaking. Models are generated for a shallow moderate crustal earthquake in the Madrid Region (Spain). Synthetic translational and rotational time histories are computed using the Discrete Wavenumber Method, assuming a point source and a horizontal layered earth structure. These are used to analyze the dynamic response of a wind turb...

  5. Collapse dynamics of a fluid hole in a rotating thin film

    CERN Document Server

    Bostwick, Joshua

    2015-01-01

    We study the collapse dynamics of an axisymmetric fluid cavity that wets the bottom of a rotating bucket bound by vertical sidewalls. Lubrication theory is applied to the governing field equations for the thin film to yield an evolution equation that captures the effect of capillary, gravitational and centrifugal forces on this converging flow. We focus on the quasi-static spreading regime, whereby contact-line motion is governed by a constitutive law relating the contact-angle to the contact-line speed. We report the collapse time, as it depends upon the initial hole size, showing that gravity accelerates the collapse process. Surface tension forces dominate the collapse dynamics for small holes leading to a universal power law whose exponent compares favorably to experiments reported in the literature. Centrifugal forces slow the collapse process and lead to complex dynamics characterized by stalled spreading behavior that separates the large and small hole asymptotic regimes.

  6. Role of rotational energy component in the dynamics of 16O+198Pt reaction

    Directory of Open Access Journals (Sweden)

    Sharma Manoj K.

    2017-01-01

    Full Text Available The role of rotational energy is investigated in reference to the dynamics of 16O+198Pt →214Rn∗ reaction using the sticking (IS and the non-sticking (INS limits of moment of inertia within the framework of dynamical cluster decay model. The decay barrier height and barrier position get significantly modified for the use of sticking or non-sticking choice, which in turn reproduce the evaporation residue and the fusion-fission cross-sections nicely by the IS approach, while the INS approach provides feasible addressal of data only for evaporation residue channel. Moreover, the fragmentation path of decaying fragments of 214Rn∗ compound nucleus gets influenced for different choices of moment of inertia. Beside this, the role of nuclear deformations i.e. static, dynamic quadurpole (β2 and higher order static deformation up to β4 are duly investigated for both choices of the moment of inertia.

  7. Translational and rotational dynamics of a large buoyant sphere in turbulence

    CERN Document Server

    Mathai, Varghese; van der Poel, Erwin P; Sun, Chao

    2016-01-01

    We report experimental measurements of the translational and rotational dynamics of a large buoyant sphere in isotropic turbulence. We introduce an efficient method to simultaneously determine the position and (absolute) orientation of a spherical body from visual observation. The method employs a minimization algorithm to obtain the orientation from the 2D projection of a specific pattern drawn onto the surface of the sphere. This has the advantages that it does not require a database of reference images, is easily scalable using parallel processing, and enables accurate absolute orientation reference. Analysis of the sphere's translational dynamics reveals clear differences between the streamwise and transverse directions. The translational auto-correlations and PDFs provide evidence for periodicity in the particle's dynamics even under turbulent conditions. The angular autocorrelations show weak periodicity. The angular accelerations exhibit wide tails, however without a directional dependence.

  8. Dynamical resonance in F+H2 chemical reaction and rotational excitation effect

    Institute of Scientific and Technical Information of China (English)

    YANG XueMing; XIE DaiQian; ZHANG DongHui

    2007-01-01

    Reaction resonance is a frontier topic in chemical dynamics research, and it is also essential to the understanding of mechanisms of elementary chemical reactions. This short article describes an important development in the frontier of research. Experimental evidence of reaction resonance has been detected in a full quantum state resolved reactive scattering study of the F+H2 reaction. Highly accurate full quantum scattering theoretical modeling shows that the reaction resonance is caused by two Feshbach resonance states. Further studies show that quantum interference is present between the two resonance states for the forward scattering product. This study is a significant step forward in our understanding of chemical reaction resonance in the benchmark F+H2 system. Further experimental studies on the effect of H2 rotational excitation on dynamical resonance have been carried out. Dynamical resonance in the F+H2 (j = 1) reaction has also been observed.

  9. Rotational dynamics of an asymmetric top molecule in parallel electric and non-resonant laser fields

    CERN Document Server

    Omiste, Juan J

    2013-01-01

    We present a theoretical study of the rotational dynamics of asymmetry top molecules in parallel electric field and non-resonant linearly polarized laser pulses. The time-dependent Schr\\"odinger equation is solved within the the rigid rotor approximation. Using the benzonitrile molecule as prototype, we investigate the field-dressed dynamics for experimentally accessible field configurations and compare these results to the adiabatic predictions. We show that for an asymmetric top molecule in parallel fields, the formation of the pendular doublets and the avoided crossings between neighboring levels are the two main sources of non-adiabatic effects. We also provide the field parameters under which the adiabatic dynamics would be achieved.

  10. Dynamics of rotationally fissioned asteroids: Source of observed small asteroid systems

    CERN Document Server

    Jacobson, Seth A

    2014-01-01

    We present a model of near-Earth asteroid (NEA) rotational fission and ensuing dynamics that describes the creation of synchronous binaries and all other observed NEA systems including: doubly synchronous binaries, high- e binaries, ternary systems, and contact binaries. Our model only presupposes the Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effect, "rubble pile" asteroid geophysics, and gravitational interactions. The YORP effect torques a "rubble pile" asteroid until the asteroid reaches its fission spin limit and the components enter orbit about each other (Scheeres, D.J. [2007]. Icarus 189, 370-385). Non-spherical gravitational potentials couple the spin states to the orbit state and chaotically drive the system towards the observed asteroid classes along two evolutionary tracks primarily distinguished by mass ratio. Related to this is a new binary process termed secondary fission - the secondary asteroid of the binary system is rotationally accelerated via gravitational torques until it fissions, thu...

  11. Energy harvester for rotating environments using offset pendulum and nonlinear dynamics

    Science.gov (United States)

    Roundy, Shad; Tola, Jeffry

    2014-10-01

    We present an energy harvester for environments that rotate through the Earth’s gravitational field. Example applications include shafts connected to motors, axles, propellers, fans, and wheels or tires. Our approach uses the unique dynamics of an offset pendulum along with a nonlinear bistable restoring spring to improve the operational bandwidth of the system. Depending on the speed of the rotating environment, the system can act as a bistable oscillator, monostable stiffening oscillator, or linear oscillator. We apply our approach to a tire pressure monitoring system mounted on a car rim. Simulation and experimental test results show that the prototype generator is capable of directly powering an RF transmission every 60 s or less over a speed range of 10 to 155 kph.

  12. Dynamic Chiral Magnetic Effect and Faraday Rotation in Macroscopically Disordered Helical Metals

    Science.gov (United States)

    Ma, J.; Pesin, D. A.

    2017-03-01

    We develop an effective medium theory for electromagnetic wave propagation through gapless nonuniform systems with a dynamic chiral magnetic effect. The theory allows us to calculate macroscopic-disorder-induced corrections to the values of optical, as well as chiral magnetic conductivities. In particular, we show that spatial fluctuations of the optical conductivity induce corrections to the effective value of the chiral magnetic conductivity. The absolute value of the effect varies strongly depending on the system parameters, but yields the leading frequency dependence of the polarization rotation and circular dichroism signals. Experimentally, these corrections can be observed as features in the Faraday rotation angle near frequencies that correspond to the bulk plasmon resonances of a material. Such features are not expected to be present in single-crystal samples.

  13. Testes visuomotores em crianças com estrabismo Visuomotor tests in children with strabismus

    Directory of Open Access Journals (Sweden)

    Jorge Alberto F. Caldeira

    1970-09-01

    Full Text Available Em 43 crianças estrábicas nas quais foi determinado o quociente intelectual foram aplicados os testes visuomotores de Goldstein-Scheerer, Bender-Santucci, lateralidade e estereognosia. Os resultados foram comparados com os obtidos em 44 controles dos mesmos grupos etários e sócio-econômicamente semelhantes. Sugere-se o prosseguimento desta pesquisa com o estudo comparativo entre o teste de Goldstein-Scheerer e o "visual retention test" de Benton (1963 nos quais a análise do fator memória visual pode ser útil para averiguar dificuldades relacionadas com a prontidão para a alfabetização. Sugere-se, também, o estudo de um grupo de crianças em idade escolar com e sem perturbações da motilidade ocular extrínseca para avaliar a influência da escolaridade nos resultados dos testes.Forty-three children with different forms of strabismus and 44 normal children were submited to the following tests: Terman-Merrill intelligence scale, form L-M; Goldstein-Scheerer stick test; Bender-Santucci graphic perceptive organisation; Zazzo lateral dominance test; Tyson cross-modality matching test. Children with squint exhibited poorer results with the Terman-Merrill, Goldstein-Scheerer and Tyson tests as compared with normal children. The differences found with the other tests were not significant.

  14. Toward Realistic Dynamics of Rotating Orbital Debris, and Implications for Lightcurve Interpretation

    Science.gov (United States)

    Ojakangas, Gregory W.; Cowardin, H.; Hill, N.

    2011-01-01

    Optical observations of rotating space debris near GEO contain important information on size, shape, composition, and rotational states, but these aspects are difficult to extract due to data limitations and the high number of degrees of freedom in the modeling process. For tri-axial rigid debris objects created by satellite fragmentations, the most likely initial rotation state has a large component of initial angular velocity directed along the intermediate axis of inertia, leading to large angular reorientations of the body on the timescale of the rotation period. This lends some support to the simplest possible interpretation of light curves -- that they represent sets of random orientations of the objects of study. However, effects of internal friction and solar radiation are likely to cause significant modification of rotation states within a time as short as a few orbital periods. In order to examine the rotational dynamics of debris objects under the influences of these effects, a set of seven first-order coupled equations of motion were assembled in state form: three are Euler equations describing the rates of change of the components of angular velocity in the body frame, and four describe the rates of change of the components of the unit quaternion. Quaternions are a four-dimensional extension of complex numbers that form a seamless, singularity-free representation of body orientation on S3. The Euler equations contain explicit terms describing torque from solar radiation in terms of spherical harmonics, and terms representing effects of a prescribed rate of internal friction. Numerical integrations of these equations of motion are being performed, and results will be presented. Initial tests show that internal friction without solar radiation torque leads to rotation about the maximum principal axis of inertia, as required, and solar radiation torque is expected to lead to spin-up of objects. Because the axis of maximum rotational inertia tends to be

  15. Energetic dynamics of a rotating horizontal convection model of an ocean basin with wind forcing

    Science.gov (United States)

    Zemskova, Varvara; White, Brian; Scotti, Alberto

    2016-11-01

    We analyze the energetic dynamics in a rotating horizontal convection model, where flow is driven by a differential buoyancy forcing along a horizontal surface. This model is used to quantify the influence of surface heating and cooling and surface wind stress on the Meridional Overturning Circulation. We study a model of the Southern Ocean in a rectangular basin with surface cooling on one end (the South pole) and surface warming on the other end (mid-latitudes). Free-slip boundary conditions are imposed in the closed box, while zonally periodic boundary conditions are enforced in the reentrant channel. Wind stress and differential buoyancy forcing are applied at the top boundary. The problem is solved numerically using a 3D DNS model based on a finite-volume AMR solver for the Boussinesq Navier-Stokes equations with rotation. The overall dynamics, including large-scale overturning, baroclinic eddying, turbulent mixing, and resulting energy cascades are investigated using the local Available Potential Energy framework introduced in. We study the relative contributions of surface buoyancy and wind forcing along with the effects of bottom topography to the energetic balance of this dynamic model. This research is part of the Blue Waters sustained-petascale computing project, supported by the NSF (awards OCI-0725070, ACI-1238993 and ACI-14-44747) and the state of Illinois.

  16. Identification of dominant flow structures in rapidly rotating convection of liquid metals using Dynamic Mode Decomposition

    Science.gov (United States)

    Horn, S.; Schmid, P. J.; Aurnou, J. M.

    2016-12-01

    The Earth's metal core acts as a dynamo whose efficiency in generating and maintaining the magnetic field is essentially determined by the rotation rate and the convective motions occurring in its outer liquid part. For the description of the primary physics in the outer core the idealized system of rotating Rayleigh-Bénard convection is often invoked, with the majority of studies considering only working fluids with Prandtl numbers of Pr ≳ 1. However, liquid metals are characterized by distinctly smaller Prandtl numbers which in turn result in an inherently different type of convection. Here, we will present results from direct numerical simulations of rapidly rotating convection in a fluid with Pr ≈ 0.025 in cylindrical containers and Ekman numbers as low as 5 × 10-6. In this system, the Coriolis force is the source of two types of inertial modes, the so-called wall modes, that also exist at moderate Prandtl numbers, and cylinder-filling oscillatory modes, that are a unique feature of small Prandtl number convection. The obtained flow fields were analyzed using the Dynamic Mode Decomposition (DMD). This technique allows to extract and identify the structures that govern the dynamics of the system as well as their corresponding frequencies. We have investigated both the regime where the flow is purely oscillatory and the regime where wall modes and oscillatory modes co-exist. In the purely oscillatory regime, high and low frequency oscillatory modes characterize the flow. When both types of modes are present, the DMD reveals that the wall-attached modes dominate the flow dynamics. They precess with a relatively low frequency in retrograde direction. Nonetheless, also in this case, high frequency oscillations have a significant contribution.

  17. Polarization dynamics in dissipative soliton fiber lasers mode-locked by nonlinear polarization rotation.

    Science.gov (United States)

    Kong, Lingjie; Xiao, Xiaosheng; Yang, Changxi

    2011-09-12

    We numerically studied the polarization dynamics in dissipative soliton lasers mode-locked by nonlinear polarization rotation (NPR). It was found that the polarization states of the intracavity dissipative soliton vary with time across the pulse. Depending on output coupling ratios, the polarization states of the pulse peak before the polarizer can be either nearly circular or nearly linear polarizations. The polarization dependent component in NPR is found to play a role of spectral filter under high and medium output coupling. However, NPR may work as a weak optical limiter under low output coupling, when additional spectral filtering is necessary to maintain steady mode-locking state.

  18. On the polar moment of inertia of a compressible body. [planetary rotational dynamics

    Science.gov (United States)

    Mulholland, J. D.

    1980-01-01

    The rotational dynamics of a body are governed by the values of its principle moments of inertia. These quantities are not directly observable, but they are related to the harmonic coefficients of the external gravity field and to the density distribution within the body, both of which can be inferred from appropriate observations. It is shown that, for the particular case of a spherical planet whose density varies as a power of the radial distance, the principal moment of inertia has an elegantly simple form. Application of this simplified case to the Jovian planets suggests that the density profiles outside the central core are approximately linear, with the apparent exception of Neptune.

  19. Rotational viscosity of a liquid crystal mixture:a fully atomistic molecular dynamics study

    Institute of Scientific and Technical Information of China (English)

    Zhang Ran; Peng Zeng-Hui; Liu Yong-Gang; Zheng Zhi-Gang; Xuan Li

    2009-01-01

    Fully atomistic molecular dynamics(MD)simulations at 293, 303 and 313 K have been performed for the four. component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions(TCFs)were calculated from MD trajectories. The rotational viscosity coefficients(RVCs)of the mixture were ca]culated using the Nemtsov-Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detall. Reasonable agreement between the simulated and experimental values was found.

  20. Generalization patterns for reach adaptation and proprioceptive recalibration differ after visuomotor learning.

    Science.gov (United States)

    Cressman, Erin K; Henriques, Denise Y P

    2015-07-01

    Visuomotor learning results in changes in both motor and sensory systems (Cressman EK, Henriques DY. J Neurophysiol 102: 3505-3518, 2009), such that reaches are adapted and sense of felt hand position recalibrated after reaching with altered visual feedback of the hand. Moreover, visuomotor learning has been shown to generalize such that reach adaptation achieved at a trained target location can influence reaches to novel target directions (Krakauer JW, Pine ZM, Ghilardi MF, Ghez C. J Neurosci 20: 8916-8924, 2000). We looked to determine whether proprioceptive recalibration also generalizes to novel locations. Moreover, we looked to establish the relationship between reach adaptation and changes in sense of felt hand position by determining whether proprioceptive recalibration generalizes to novel targets in a similar manner as reach adaptation. On training trials, subjects reached to a single target with aligned or misaligned cursor-hand feedback, in which the cursor was either rotated or scaled in extent relative to hand movement. After reach training, subjects reached to the training target and novel targets (including targets from a second start position) without visual feedback to assess generalization of reach adaptation. Subjects then performed a proprioceptive estimation task, in which they indicated the position of their hand relative to visual reference markers placed at similar locations as the trained and novel reach targets. Results indicated that shifts in hand position generalized across novel locations, independent of reach adaptation. Thus these distinct sensory and motor generalization patterns suggest that reach adaptation and proprioceptive recalibration arise from independent error signals and that changes in one system cannot guide adjustments in the other.

  1. Feasibility of Using PZT Actuators to Study the Dynamic Behavior of a Rotating Disk due to Rotor-Stator Interaction

    Directory of Open Access Journals (Sweden)

    Alexandre Presas

    2014-07-01

    Full Text Available In this paper, PZT actuators are used to study the dynamic behavior of a rotating disk structure due to rotor-stator interaction excitation. The disk is studied with two different surrounding fluids—air and water. The study has been performed analytically and validated experimentally. For the theoretical analysis, the natural frequencies and the associated mode shapes of the rotating disk in air and water are obtained with the Kirchhoff-Love thin plate theory coupled with the interaction with the surrounding fluid. A model for the Rotor Stator Interaction that occurs in many rotating disk-like parts of turbomachinery such as compressors, hydraulic runners or alternators is presented. The dynamic behavior of the rotating disk due to this excitation is deduced. For the experimental analysis a test rig has been developed. It consists of a stainless steel disk (r = 198 mm and h = 8 mm connected to a variable speed motor. Excitation and response are measured from the rotating system. For the rotating excitation four piezoelectric patches have been used. Calibrating the piezoelectric patches in amplitude and phase, different rotating excitation patterns are applied on the rotating disk in air and in water. Results show the feasibility of using PZT to control the response of the disk due to a rotor-stator interaction.

  2. Feasibility of using PZT actuators to study the dynamic behavior of a rotating disk due to rotor-stator interaction.

    Science.gov (United States)

    Presas, Alexandre; Egusquiza, Eduard; Valero, Carme; Valentin, David; Seidel, Ulrich

    2014-07-07

    In this paper, PZT actuators are used to study the dynamic behavior of a rotating disk structure due to rotor-stator interaction excitation. The disk is studied with two different surrounding fluids-air and water. The study has been performed analytically and validated experimentally. For the theoretical analysis, the natural frequencies and the associated mode shapes of the rotating disk in air and water are obtained with the Kirchhoff-Love thin plate theory coupled with the interaction with the surrounding fluid. A model for the Rotor Stator Interaction that occurs in many rotating disk-like parts of turbomachinery such as compressors, hydraulic runners or alternators is presented. The dynamic behavior of the rotating disk due to this excitation is deduced. For the experimental analysis a test rig has been developed. It consists of a stainless steel disk (r = 198 mm and h = 8 mm) connected to a variable speed motor. Excitation and response are measured from the rotating system. For the rotating excitation four piezoelectric patches have been used. Calibrating the piezoelectric patches in amplitude and phase, different rotating excitation patterns are applied on the rotating disk in air and in water. Results show the feasibility of using PZT to control the response of the disk due to a rotor-stator interaction.

  3. Representing tools as hand movements: early and somatotopic visuomotor transformations.

    Science.gov (United States)

    Bartoli, Eleonora; Maffongelli, Laura; Jacono, Marco; D'Ausilio, Alessandro

    2014-08-01

    The term affordance defines a property of objects, which relates to the possible interactions that an agent can carry out on that object. In monkeys, canonical neurons encode both the visual and the motor properties of objects with high specificity. However, it is not clear if in humans exists a similarly fine-grained description of these visuomotor transformations. In particular, it has not yet been proven that the processing of visual features related to specific affordances induces both specific and early visuomotor transformations, given that complete specificity has been reported to emerge quite late (300-450ms). In this study, we applied an adaptation-stimulation paradigm to investigate early cortico-spinal facilitation and hand movements׳ synergies evoked by the observation of tools. We adapted, through passive observation of finger movements, neuronal populations coding either for precision or power grip actions. We then presented the picture of one tool affording one of the two grasps types and applied single-pulse Transcranial Magnetic Stimulation (TMS) to the hand primary motor cortex, 150ms after image onset. Cortico-spinal excitability of the Abductor Digiti Minimi and Abductor Pollicis Brevis showed a detailed pattern of modulations, matching tools׳ affordances. Similarly, TMS-induced hand movements showed a pattern of grip-specific whole hand synergies. These results offer a direct proof of the emergence of an early visuomotor transformation when tools are observed, that maintains the same amount of synergistic motor details as the actions we can perform on them.

  4. Effects of normal aging on visuo-motor plasticity

    Science.gov (United States)

    Roller, Carrie A.; Cohen, Helen S.; Kimball, Kay T.; Bloomberg, Jacob J.

    2002-01-01

    Normal aging is associated with declines in neurologic function. Uncompensated visual and vestibular problems may have dire consequences including dangerous falls. Visuo-motor plasticity is a form of behavioral neural plasticity, which is important in the process of adapting to visual or vestibular alteration, including those changes due to pathology, pharmacotherapy, surgery or even entry into microgravity or an underwater environment. To determine the effects of aging on visuo-motor plasticity, we chose the simple and easily measured paradigm of visual-motor rearrangement created by using visual displacement prisms while throwing small balls at a target. Subjects threw balls before, during and after wearing a set of prisms which displace the visual scene by twenty degrees to the right. Data obtained during adaptation were modeled using multilevel modeling techniques for 73 subjects, aged 20 to 80 years. We found no statistically significant difference in measures of visuo-motor plasticity with advancing age. Further studies are underway examining variable practice training as a potential mechanism for enhancing this form of behavioral neural plasticity.

  5. Visuomotor memory in elderly: effect of a physical exercise program

    Directory of Open Access Journals (Sweden)

    João Silva

    2014-12-01

    Full Text Available Memory, namely visuomotor memory, is one of the most essential cognitive functions in elder’s life. Among others, regular exercise seems to be an important factor in counteracting age-related-cognitive skills changes and thus prevent memory loss. However, in spite of the importance of visuomotor memory, the results of the scarce studies concerning the influence of exercise on this capacity are contradictory. The aim of this study was to investigate the effect of physical exercise (PE in visuomotor memory (VMM of elderly adults in function of gender and age. VMM (time spent in performing the test and errors during the execution of 74 subjects aged 60-90 years, being 36 practitioners of PE (P - mean age of 70.22 ± 0.90 years and 38 non-practitioners (NP - mean age of 68.26 ± 1.12 years were assessed by VMM Test. The results showed that: a P presented a better performance in the time of performing the test and in the number of errors committed compared to NP; b Gender and age did not influence the VMM performance. Data suggest that PE seems to have positive effect in the VMM, independently of gender and age.

  6. Studying Vortex Dynamics of Rotating Convection with High-resolution PIV Measurement

    Science.gov (United States)

    Fu, Hao; Sun, Shiwei; Wang, Yu; Zhou, Bowen; Wang, Yuan

    2016-11-01

    A novel experimental setup for studying vortex dynamics in rotating Rayleigh-Benard convection has been made in School of Atmospheric Sciences, Nanjing University. With water as the working fluid, three lasers with different frequencies and the corresponding three CCDs have been placed to complete 2D2C (two dimensions, two components) PIV measurement. The lasers are fixed on two crossing guiding ways and can move up and down to scan the flow field. An algorithm has been made to reconstruct 3D velocity field based on multiple 2D2C PIV data. This time, we are going to present the details of this new machine and algorithm, as well as some scientific understanding of vortex dynamics owing to this high-resolution velocity measurement system. This work was supported by "LMSWE Lab Funding No. 14380001".

  7. Approaching the Asymptotic Regime of Rapidly Rotating Convection: Boundary Layers vs Interior Dynamics

    CERN Document Server

    Stellmach, S; Julien, K; Vasil, G; Cheng, J S; Ribeiro, A; King, E M; Aurnou, J M

    2014-01-01

    Rapidly rotating Rayleigh-B\\'enard convection is studied by combining results from direct numerical simulations (DNS), laboratory experiments and asymptotic modeling. The asymptotic theory is shown to provide a good description of the bulk dynamics at low, but finite Rossby number. However, large deviations from the asymptotically predicted heat transfer scaling are found, with laboratory experiments and DNS consistently yielding much larger Nusselt numbers than expected. These deviations are traced down to dynamically active Ekman boundary layers, which are shown to play an integral part in controlling heat transfer even for Ekman numbers as small as $10^{-7}$. By adding an analytical parameterization of the Ekman transport to simulations using stress-free boundary conditions, we demonstrate that the heat transfer jumps from values broadly compatible with the asymptotic theory to states of strongly increased heat transfer, in good quantitative agreement with no-slip DNS and compatible with the experimental d...

  8. Dynamic characterization, monitoring and control of rotating flexible beam-mass structures via piezo-embedded techniques

    Science.gov (United States)

    Lai, Steven H.-Y.

    1992-01-01

    A variational principle and a finite element discretization technique were used to derive the dynamic equations for a high speed rotating flexible beam-mass system embedded with piezo-electric materials. The dynamic equation thus obtained allows the development of finite element models which accommodate both the original structural element and the piezoelectric element. The solutions of finite element models provide system dynamics needed to design a sensing system. The characterization of gyroscopic effect and damping capacity of smart rotating devices are addressed. Several simulation examples are presented to validate the analytical solution.

  9. Oscillatory shear response of dilute ferrofluids: predictions from rotational Brownian dynamics simulations and ferrohydrodynamics modeling.

    Science.gov (United States)

    Soto-Aquino, D; Rosso, D; Rinaldi, C

    2011-11-01

    Ferrofluids are colloidal suspensions of magnetic nanoparticles that exhibit normal liquid behavior in the absence of magnetic fields but respond to imposed magnetic fields by changing their viscosity without loss of fluidity. The response of ferrofluids to constant shear and magnetic fields has received a lot of attention, but the response of ferrofluids to oscillatory shear remains largely unexplored. In the present work we used rotational Brownian dynamics to study the dynamic properties of ferrofluids with thermally blocked nanoparticles under oscillatory shear and constant magnetic fields. Comparisons between simulations and modeling using the ferrohydrodynamics equations were also made. Simulation results show that, for small rotational Péclet number, the in-phase and out-of-phase components of the complex viscosity depend on the magnitude of the magnetic field and frequency of the shear, following a Maxwell-like model with field-dependent viscosity and characteristic time equal to the field-dependent transverse magnetic relaxation time of the nanoparticles. Comparison between simulations and the numerical solution of the ferrohydrodynamic equations shows that the oscillatory rotational magnetoviscosity for an oscillating shear field obtained using the kinetic magnetization relaxation equation quantitatively agrees with simulations for a wide range of Péclet number and Langevin parameter but has quantitative deviations from the simulations at high values of the Langevin parameter. These predictions indicate an apparent elastic character to the rheology of these suspensions, even though we are considering the infinitely dilute limit in which there are negligible particle-particle interactions and, as such, chains do not form. Additionally, an asymptotic analytical solution of the ferrohydrodynamics equations, valid for Pe<2, was used to demonstrate that the Cox-Merz rule applies for dilute ferrofluids under conditions of small shear rates. At higher shear

  10. Aeroelastic deployable wing simulation considering rotation hinge joint based on flexible multibody dynamics

    Science.gov (United States)

    Otsuka, Keisuke; Makihara, Kanjuro

    2016-05-01

    Morphing wings have been developed by several organizations for a variety of applications including the changing of flight ability while in the air and reducing the amount of space required to store an aircraft. One such example of morphing wings is the deployable wing that is expected to be used for Mars exploration. When designing wings, aeroelastic simulation is important to prevent the occurrence of destructive phenomena while the wing is in use. Flutter and divergence are typical issues to be addressed. However, it has been difficult to simulate the aeroelastic motion of deployable wings because of the significant differences between these deployable wings and conventional designs. The most apparent difference is the kinematic constraints of deployment, typically a hinge joint. These constraints lead not only to deformation but also to rigid body rotation. This research provides a novel method of overcoming the difficulties associated with handling these kinematic constraints. The proposed method utilizes flexible multibody dynamics and absolute nodal coordinate formulation to describe the dynamic motion of a deployable wing. This paper presents the simulation of the rigid body rotation around the kinematic constraints as induced by the aeroelasticity. The practicality of the proposed method is confirmed.

  11. Cation effects on rotational dynamics of anions and water molecules in alkali (Li+, Na+, K+, Cs+) thiocyanate (SCN-) aqueous solutions.

    Science.gov (United States)

    Bian, Hongtao; Chen, Hailong; Zhang, Qiang; Li, Jiebo; Wen, Xiewen; Zhuang, Wei; Zheng, Junrong

    2013-07-03

    Waiting time dependent rotational anisotropies of SCN(-) anions and water molecules in alkali thiocyanate (XSCN, X = Li, Na, K, Cs) aqueous solutions at various concentrations were measured with ultrafast infrared spectroscopy. It was found that cations can significantly affect the reorientational motions of both water molecules and SCN(-) anions. The dynamics are slower in a solution with a smaller cation. The reorientational time constants follow the order of Li(+) > Na(+) > K(+) ~/= Cs(+). The changes of rotational time constants of SCN(-) at various concentrations scale almost linearly with the changes of solution viscosity, but those of water molecules do not. In addition, the concentration-dependent amplitudes of dynamical changes are much more significant in the Li(+) and Na(+) solutions than those in the K(+) and Cs(+) solutions. Further investigations on the systems with the ultrafast vibrational energy exchange method and molecular dynamics simulations provide an explanation for the observations: the observed rotational dynamics are the balanced results of ion clustering and cation/anion/water direct interactions. In all the solutions at high concentrations (>5 M), substantial amounts of ions form clusters. The structural inhomogeneity in the solutions leads to distinct rotational dynamics of water and anions. The strong interactions of Li(+) and Na(+) because of their relatively large charge densities with water molecules and SCN(-) anions, in addition to the likely geometric confinements because of ion clustering, substantially slow down the rotations of SCN(-) anions and water molecules inside the ion clusters. The interactions of K(+) and Cs(+) with water or SCN(-) are much weaker. The rotations of water molecules inside ion clusters of K(+) and Cs(+) solutions are not significantly different from those of other water species so that the experimentally observed rotational relaxation dynamics are only slightly affected by the ion concentrations.

  12. Advance Ratio Effects on the Dynamic-stall Vortex of a Rotating Blade in Steady Forward Flight

    Science.gov (United States)

    2014-08-06

    Office P.O. Box 12211 Research Triangle Park , NC 27709-2211 Leading-edge vortex, Dynamic stall vortex, Vortex flows, Rotating wing REPORT...observed on rotating insect wing investigations2,9–13. A common theme among most of these investigations is the existence of a strong span-wise flow...structures by considering only the topology of the flow field. It is specifically designed to identify a large scale vortex superposed on a small-scale

  13. Analytic Transfer Functions for the Dynamics & Control of Flexible Rotating Spacecraft Performing Large Angle Maneuvers

    Science.gov (United States)

    Elgohary, Tarek A.; Turner, James D.; Junkins, John L.

    2015-06-01

    A symmetric flexible rotating spacecraft can be modeled as a distributed parameter system of a rigid hub attached to two flexible appendages with tip masses. First, Hamilton's extended principle is utilized to establish a general treatment for deriving the dynamics of multi-body dynamical systems to establish a hybrid system of integro-partial differential equations that model the evolution of the system in space and time. A Generalized State Space (GSS) system of equations is constructed in the frequency domain to obtain analytic transfer functions for the rotating spacecraft. This model does not include spatial discretization. The frequency response of the generally modeled spacecraft and a special case with no tip masses are presented. Numerical results for the system frequency response obtained from the analytic transfer functions are presented and compared against the classical assumed modes numerical method with two choices of admissible functions. The truncation-error-free analytic results are used to validate the numerical approximations and to agree well with the classical widely used finite dimensional numerical solutions. Fundamentally, we show that the rigorous transfer function, without introduction of spatial discretization, can be directly used in control law design with a guarantee of Lyapunov stable closed loop dynamics. The frequency response of the system is used in a classical control problem where the Lyapunov stable controller is derived and tested for gain selection. The correlation between the controller design in the frequency domain utilizing the analytic transfer functions and the system response is analyzed and verified. The derived analytic transfer functions provide a powerful tool to test various control schemes in the frequency domain and a validation platform for existing numerical methods for distributed parameters models. The same platform has been used to obtain the frequency response of more complex beam models following

  14. Coupled rotational dynamics of Saturn's thermosphere and magnetosphere: a thermospheric modelling study

    Directory of Open Access Journals (Sweden)

    C. G. A. Smith

    2008-05-01

    Full Text Available We use a numerical model of Saturn's thermosphere to investigate the flow of angular momentum from the atmosphere to the magnetosphere. The thermosphere model is driven by Joule heating and ion drag calculated from a simple model of the magnetospheric plasma flows and a fixed model of the ionospheric conductivity. We describe an initial study in which our plasma flow model is fixed and find that this leads to several inconsistencies in our results. We thus describe an improved model in which the plasma flows are allowed to vary in response to the structure of the thermospheric winds. Using this improved model we are able to analyse in detail the mechanism by which angular momentum extracted from the thermosphere by the magnetosphere is replaced by transport from the lower atmosphere. Previously, this transport was believed to be dominated by vertical transport due to eddy viscosity. Our results suggest that transport within the upper atmosphere by meridional winds is a much more important mechanism. As a consequence of this, we find that the rotational structures of the thermosphere and magnetosphere are related in a more complex way than the eddy viscosity model implies. Rather than the thermosphere behaving as a passive component of the system, the thermosphere-magnetosphere interaction is shown to be a two-way process in which rotational structures develop mutually. As an example of this, we are able to show that thermospheric dynamics offer an explanation of the small degree of super-corotation that has been observed in the inner magnetosphere. These results call into question the usefulness of the effective Pedersen conductivity as a parameterisation of the neutral atmosphere. We suggest that a two-parameter model employing the true Pedersen conductivity and the true thermospheric rotation velocity may be a more accurate representation of the thermospheric behaviour.

  15. Dynamic scaling of the restoration of rotational symmetry in Heisenberg quantum antiferromagnets

    Science.gov (United States)

    Weinberg, Phillip; Sandvik, Anders W.

    2017-08-01

    We apply imaginary-time evolution with the operator e-τ H to study relaxation dynamics of gapless quantum antiferromagnets described by the spin-rotation-invariant Heisenberg Hamiltonian H . Using quantum Monte Carlo simulations to obtain unbiased results, we propagate an initial state with maximal order parameter msz (the staggered magnetization) in the z spin direction and monitor the expectation value 〈ms〉 as a function of imaginary time τ . Results for different system sizes (lengths) L exhibit an initial essentially size independent relaxation of 〈ms〉 toward its value in the infinite-size spontaneously symmetry broken state, followed by a strongly size dependent final decay to zero when the O (3 ) rotational symmetry of the order parameter is restored. We develop a generic finite-size scaling theory that shows the relaxation time diverges asymptotically as Lz, where z is the dynamic exponent of the low-energy excitations. We use the scaling theory to develop a practical way of extracting the dynamic exponent from the numerical finite-size data, systematically eliminating scaling corrections. We apply the method to spin-1 /2 Heisenberg antiferromagnets on two different lattice geometries: the standard two-dimensional (2D) square lattice and a site-diluted 2D square lattice at the percolation threshold. In the 2D case we obtain z =2.001 (5 ) , which is consistent with the known value z =2 , while for the site-diluted lattice we find z =3.90 (1 ) or z =2.056 (8 ) Df , where Df=91 /48 is the fractal dimensionality of the percolating system. This is an improvement on previous estimates of z ≈3.7 . The scaling results also show a fundamental difference between the two cases; for the 2D square lattice, the data can be collapsed onto a common scaling function even when 〈ms〉 is relatively large, reflecting the Anderson tower of quantum rotor states with a common dynamic exponent z =2 . For the diluted 2D square lattice, the scaling works well only for

  16. Helioseismic Observations of the Structure and Dynamics of a Rotating Sunspot Beneath the Solar Surface

    Science.gov (United States)

    Zhao, Junwei; Kosovichev, Alexander G.

    2003-01-01

    Time-distance helioseismology is applied to study the subphotospheric structures and dynamics of an unusually fast-rotating sunspot observed by the Michelson Doppler Imager on bead SOH0 in 2000 August. The subsurface sound speed structures and velocity fields are obtained for the sunspot region at different depths from 0 to 12 Mm. By comparing the subsurface sound speed variations with the surface magnetic field, we find evidence for structural twists beneath the visible surface of this active region, which may indicate that magnetic twists often seen at the photosphere also exist beneath the photosphere. We also report on the observation of subsurface horizontal vortical flows that extend to a depth of 5 Mm around this rotating sunspot and present evidence that opposite vortical flows may exist below 9 Mm. It is suggested that the vortical flows around this active region may build up a significant amount of magnetic helicity and energy to power solar eruptions. Monte Carlo simulation has been performed to estimate the error propagation, and in addition the sunspot umbra is masked to test the reliability of our inversion results. On the basis of the three-dimensional velocity fields obtained from the time-distance helioseismology inversions, we estimate the subsurface kinetic helicity at different depths for the first time and conclude that it is comparable to the current helicity estimated from vector magnetograms.

  17. Dynamics of local isolated magnetic flux tubes in a fast-rotating stellar atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Chou, W.; Tajima, C.T. [Univ. of Texas, Austin, TX (United States). Dept. of Physics; Matsumoto, R. [Chiba Univ. (Japan)]|[ASRC, JAERI, Naka (Japan); Shibata, K. [National Astronomical Observatory, Mitaka (Japan)

    1998-01-01

    Dynamics of magnetic flux tubes in the fast rotating stellar atmosphere is studied. We focus on the effects and signatures of the instability of the flux tube emergence influenced by the Coriolis force. We present the result from a linear stability analysis and discuss its possible signatures in the course of the evolution of G-type and M-type stars. We present a three dimensional magnetohydrodynamical simulation of local isolated magnetic flux tubes under a magnetic buoyancy instability in co-rotating Cartesian coordinates. We find that the combination of the buoyancy instability and the Coriolis effect gives rise to a mechanism, to twist the emerging magnetic flux tube into a helical structure. The tilt angle, east-west asymmetry and magnetic helicity of the Twisted flux tubes in the simulations are studied in detail. The linear and nonlinear analyses provide hints as to what kind of pattern of large spots in young M-type main-sequence stars might be observed. We find that young and old G-type stars may have different distributions of spots while M-type stars may always have low latitudes spots. The size of stellar spots may decrease when a star becomes older, due to the decreasing of magnetic field. A qualitative comparison with solar observations is also presented.

  18. Impact of Parkinson's Disease and Dopaminergic Medication on Adaptation to Explicit and Implicit Visuomotor Perturbations

    Science.gov (United States)

    Mongeon, David; Blanchet, Pierre; Messier, Julie

    2013-01-01

    The capacity to learn new visuomotor associations is fundamental to adaptive motor behavior. Evidence suggests visuomotor learning deficits in Parkinson's disease (PD). However, the exact nature of these deficits and the ability of dopamine medication to improve them are under-explored. Previous studies suggested that learning driven by large and…

  19. Dynamic Analysis of Rotating Shaft Subjects to Slant Crack with Experimentation and ANSYS Validation

    Directory of Open Access Journals (Sweden)

    Rushikesh V. Dhokate

    2014-09-01

    Full Text Available The paper contents the dynamic study of rotating shaft with slant crack on surface of shaft. Slant cracks are prepared artificially on surface of shaft with material EN8. In this study, crack location taken on shaft 150 mm from motor side and also for effective study healthy shaft of EN8 material is taken. Experimental results are taken with the help of FFT analyzer. Analysis is carried out from these results and finally these results are validated in FEA software i. e. ANSYS14 software. These validated results with graphs are explained in this paper. The experimentation is also done on healthy shaft of EN8 material for analysis. This paper mainly focused on validation of experimental results with ANSYS software.

  20. A dynamical study of the chirally rotated Schr\\"odinger functional in QCD

    CERN Document Server

    Brida, Mattia Dalla

    2014-01-01

    The chirally rotated Schr\\"odinger functional for Wilson-fermions allows for finite-volume, mass-independent renormalization schemes compatible with automatic O($a$) improvement. So far, in QCD, the set-up has only been studied in the quenched approximation. Here we present first results for $N_{\\rm f} = 2$ dynamical quark-flavours for several renormalization factors of quark-bilinears. We discuss how these renormalization factors can be easily obtained from simple ratios of two-point functions, and show how automatic O($a$) improvement is at work. As a by-product of this investigation the renormalization of the non-singlet axial current, $Z_A$, is determined very precisely.

  1. A dynamical study of the chirally rotated Schroedinger functional in QCD

    Energy Technology Data Exchange (ETDEWEB)

    Dalla Brida, Mattia; Sint, Stefan [Trinity College, Dublin (Ireland). School of Mathematics; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC

    2014-12-15

    The chirally rotated Schroedinger functional for Wilson-fermions allows for finite-volume, mass-independent renormalization schemes compatible with automatic O(a) improvement. So far, in QCD, the set-up has only been studied in the quenched approximation. Here we present first results for N{sub f}=2 dynamical quark-flavours for several renormalization factors of quark-bilinears. We discuss how these renormalization factors can be easily obtained from simple ratios of two-point functions, and show how automatic O(a) improvement is at work. As a by-product of this investigation the renormalization of the non-singlet axial current, Z{sub A}, is determined very precisely.

  2. Aspherical rotating dust dynamics for GIADA experiment in the coma of 67P/Churyumov- Gerasimenko

    Science.gov (United States)

    Ivanovski, S.; Zakharov, V.; Della Corte, V.; Lucarelli, F.; Crifo, J.-F.; Rotundi, A.; Fulle, M.

    2014-04-01

    The recent advances of the 3D+t cometary aspherical dust model [1, 2] have been used for studying the dust dynamics in the circumnuclear coma of the comet 67P/Churyumov-Gerasimenko (67P/C-G). This model will be used for analysis of the forthcoming in-situ dust data collected by GIADA (Grain Impact Analyzer and Dust Accumulator) [3] on board of the ESA ROSETTA probe. In the present research we study dust grain motion driven by the aerodynamic and gravitational forces and discuss the influence of dust grain's shape. We show the differences in dust grain velocities owing to the grain shape, initial orientation and rotation. The outcomes of the model are used to forecast by means of GIPSI [4] the dust distribution seen by GIADA at some of the ROSETTA operational phases.

  3. Does Visuomotor Adaptation Proceed in Stages? An Examination of the Learning Model by Chein and Schneider (2012).

    Science.gov (United States)

    Simon, Anja; Bock, Otmar

    2015-01-01

    A new 3-stage model based on neuroimaging evidence is proposed by Chein and Schneider (2012). Each stage is associated with different brain regions, and draws on cognitive abilities: the first stage on creativity, the second on selective attention, and the third on automatic processing. The purpose of the present study was to scrutinize the validity of this model for 1 popular learning paradigm, visuomotor adaptation. Participants completed tests for creativity, selective attention and automated processing before attending in a pointing task with adaptation to a 60° rotation of visual feedback. To examine the relationship between cognitive abilities and motor learning at different times of practice, associations between cognitive and adaptation scores were calculated repeatedly throughout adaptation. The authors found no benefit of high creativity for adaptive performance. High levels of selective attention were positively associated with early adaptation, but hardly with late adaptation and de-adaptation. High levels of automated execution were beneficial for late adaptation, but hardly for early and de-adaptation. From this we conclude that Chein and Schneider's first learning stage is difficult to confirm by research on visuomotor adaptation, and that the other 2 learning stages rather relate to workaround strategies than to actual adaptive recalibration.

  4. Dynamical Models of SAURON and CALIFA Galaxies: 1D and 2D Rotational Curves

    Science.gov (United States)

    Kalinova, Veselina; van de Ven, G.; Lyubenova, M.; Falcon-Barroso, J.; van den Bosch, R.

    2013-01-01

    The mass of a galaxy is the most important parameter to understand its structure and evolution. The total mass we can infer by constructing dynamical models that fit the motion of the stars and gas in the galaxy. The dark matter content then follows after subtracting the luminous matter inferred from colors and/or spectra. Here, we present the mass distribution of a sample of 18 late-type spiral (Sb-Sd) galaxies, using two-dimensional stellar kinematics obtained with the integral-field spectrograph SAURON. The observed second order velocity moments of these galaxies are fitted with solutions of the Axisymmetric Jeans equations and give us an accurate estimation of the mass-to-light ratio profiles and rotational curves. The rotation curves of the galaxies are obtained by the Asymmetric Drift Correction (ADC) and Multi-Gaussian Expansion (MGE) methods, corresponding to one- and two-dimensional mass distribution. Their comparison shows that the mass distribution based on the 2D stellar kinematics is much more reliable than 1D one. SAURON integral field of view looks at the inner parts of the galaxies in contrast with CALIFA survey. CALIFA survey provides PMAS/PPAK integral-field spectroscopic data of ~ 600 nearby galaxies as part of the Calar Alto Legacy Integral Field Area. We show the first CALIFA dynamical models of different morphological type of galaxies, giving the clue about the mass distribution of galaxies through the whole Hubble sequence and their evolution from the blue cloud to the red sequence.

  5. Haptics in teaching handwriting: the role of perceptual and visuo-motor skills.

    Science.gov (United States)

    Bara, Florence; Gentaz, Edouard

    2011-08-01

    Two studies were carried out in order to better understand the role of perceptual and visuo-motor skills in handwriting. Two training programs, visual-haptic (VH) and visual (V), were compared which differed in the way children explored the letters. The results revealed that improvements of VH training on letter recognition and handwriting quality were higher than improvements after V training. We suppose that VH training was more efficient because it improved both perceptual and visuo-motor skills. In the second experiment, in order to investigate the part of each component, we assessed the link between visuo-motor skills, perceptual skills and handwriting. The results showed that only the visuo-motor tasks predict handwriting copying performance. These results are discussed in relation to the respective roles of the perceptual and visuo-motor skills on letter shape learning and handwriting movement execution.

  6. High-frequency TRNS reduces BOLD activity during visuomotor learning.

    Directory of Open Access Journals (Sweden)

    Catarina Saiote

    Full Text Available Transcranial direct current stimulation (tDCS and transcranial random noise stimulation (tRNS consist in the application of electrical current of small intensity through the scalp, able to modulate perceptual and motor learning, probably by changing brain excitability. We investigated the effects of these transcranial electrical stimulation techniques in the early and later stages of visuomotor learning, as well as associated brain activity changes using functional magnetic resonance imaging (fMRI. We applied anodal and cathodal tDCS, low-frequency and high-frequency tRNS (lf-tRNS, 0.1-100 Hz; hf-tRNS 101-640 Hz, respectively and sham stimulation over the primary motor cortex (M1 during the first 10 minutes of a visuomotor learning paradigm and measured performance changes for 20 minutes after stimulation ceased. Functional imaging scans were acquired throughout the whole experiment. Cathodal tDCS and hf-tRNS showed a tendency to improve and lf-tRNS to hinder early learning during stimulation, an effect that remained for 20 minutes after cessation of stimulation in the late learning phase. Motor learning-related activity decreased in several regions as reported previously, however, there was no significant modulation of brain activity by tDCS. In opposition to this, hf-tRNS was associated with reduced motor task-related-activity bilaterally in the frontal cortex and precuneous, probably due to interaction with ongoing neuronal oscillations. This result highlights the potential of lf-tRNS and hf-tRNS to differentially modulate visuomotor learning and advances our knowledge on neuroplasticity induction approaches combined with functional imaging methods.

  7. Proton-driven spin diffusion in rotating solids via reversible and irreversible quantum dynamics.

    Science.gov (United States)

    Veshtort, Mikhail; Griffin, Robert G

    2011-10-07

    Proton-driven spin diffusion (PDSD) experiments in rotating solids have received a great deal of attention as a potential source of distance constraints in large biomolecules. However, the quantitative relationship between the molecular structure and observed spin diffusion has remained obscure due to the lack of an accurate theoretical description of the spin dynamics in these experiments. We start with presenting a detailed relaxation theory of PDSD in rotating solids that provides such a description. The theory applies to both conventional and radio-frequency-assisted PDSD experiments and extends to the non-Markovian regime to include such phenomena as rotational resonance (R(2)). The basic kinetic equation of the theory in the non-Markovian regime has the form of a memory function equation, with the role of the memory function played by the correlation function. The key assumption used in the derivation of this equation expresses the intuitive notion of the irreversible dissipation of coherences in macroscopic systems. Accurate expressions for the correlation functions and for the spin diffusion constants are given. The theory predicts that the spin diffusion constants governing the multi-site PDSD can be approximated by the constants observed in the two-site diffusion. Direct numerical simulations of PDSD dynamics via reversible Liouville-von Neumann equation are presented to support and compliment the theory. Remarkably, an exponential decay of the difference magnetization can be observed in such simulations in systems consisting of only 12 spins. This is a unique example of a real physical system whose typically macroscopic and apparently irreversible behavior can be traced via reversible microscopic dynamics. An accurate value for the spin diffusion constant can be usually obtained through direct simulations of PDSD in systems consisting of two (13)C nuclei and about ten (1)H nuclei from their nearest environment. Spin diffusion constants computed by this

  8. Effects of Discrete Damping on the Dynamic Behaviour of Rotating Shaft through Extended Lagrangian Formulation

    Directory of Open Access Journals (Sweden)

    Rastogi Vikas

    2016-09-01

    Full Text Available The main focus of the paper is touted as effects of discrete damping on the dynamic analysis of rotating shaft. The whole analysis is being carried out through extended Lagrangian formulation for a discrete – continuous system. The variation formulation for this system is possible, considering the continuous system as one-dimensional. The generalized formulation for one dimensional continuous rotary shaft with discrete external damper has been obtained through principle of variation. Using this extended formulation, the invariance of umbra-Lagrangian density through extended Noether’s theorem is achieved. Rayleigh beam model is used to model the shaft. Amplitude equation of rotor is obtained theoretically and validated through simulation results. The simulation results reveal the important phenomena of limiting dynamics of the rotor shaft, which is due to an imbalance of material damping and stiffness of the rotor shaft. The regenerative energy in the rotor shaft, induced due to elasticity/stiffness of the rotor shaft, is dissipated partially through the in-span discrete damper and also through the dissipative coupling between drive and the rotor shaft. In such cases, the shaft speed will not increase with increase in excitation frequency of the rotor but the slip between the drive and the shaft increases due to loading of drive.

  9. The SAMI Galaxy Survey: Gas Streaming and Dynamical M/L in Rotationally Supported Systems

    CERN Document Server

    Cecil, G; Richards, S; Bland-Hawthorn, J; Lange, R; Moffett, A; Catinella, B; Cortese, L; Ho, I -T; Taylor, E N; Bryant, J J; Allen, J T; Sweet, S M; Croom, S M; Driver, S P; Goodwin, M; Kelvin, L; Green, A W; Konstantopoulos, I S; Owers, M S; Lawrence, J S; Lorente, N P F

    2015-01-01

    Line-of-sight velocities of gas and stars can constrain dark matter (DM) within rotationally supported galaxies if they trace circular orbits extensively. Photometric asymmetries may signify non-circular motions, requiring spectra with dense spatial coverage. Our integral-field spectroscopy of 178 galaxies spanned the mass range of the SAMI Galaxy Survey. We derived circular speed curves (CSCs) of gas and stars from non-parametric Diskfit fits out to $r\\sim2r_e$. For 12/14 with measured H I profiles, ionized gas and H I maximum velocities agreed. We fitted mass-follows-light models to 163 galaxies by approximating the radial starlight profile as nested, very flattened mass homeoids viewed as a S\\'ersic form. Fitting broad-band SEDs to SDSS images gave median stellar mass/light 1.7 assuming a Kroupa IMF vs. 2.6 dynamically. Two-thirds of the dynamical mass/light measures were consistent with star+remnant IMFs. One-fifth required upscaled starlight to fit, hence comparable mass of unobserved baryons and/or DM d...

  10. Effects of Discrete Damping on the Dynamic Behaviour of Rotating Shaft through Extended Lagrangian Formulation

    Science.gov (United States)

    Rastogi, Vikas

    2016-09-01

    The main focus of the paper is touted as effects of discrete damping on the dynamic analysis of rotating shaft. The whole analysis is being carried out through extended Lagrangian formulation for a discrete - continuous system. The variation formulation for this system is possible, considering the continuous system as one-dimensional. The generalized formulation for one dimensional continuous rotary shaft with discrete external damper has been obtained through principle of variation. Using this extended formulation, the invariance of umbra-Lagrangian density through extended Noether's theorem is achieved. Rayleigh beam model is used to model the shaft. Amplitude equation of rotor is obtained theoretically and validated through simulation results. The simulation results reveal the important phenomena of limiting dynamics of the rotor shaft, which is due to an imbalance of material damping and stiffness of the rotor shaft. The regenerative energy in the rotor shaft, induced due to elasticity/stiffness of the rotor shaft, is dissipated partially through the in-span discrete damper and also through the dissipative coupling between drive and the rotor shaft. In such cases, the shaft speed will not increase with increase in excitation frequency of the rotor but the slip between the drive and the shaft increases due to loading of drive.

  11. Dynamic Simulation of Trapping and Controlled Rotation of a Microscale Rod Driven by Line Optical Tweezers

    Science.gov (United States)

    Haghshenas-Jaryani, Mahdi; Bowling, Alan; Mohanty, Samarendra

    2013-03-01

    Since the invention of optical tweezers, several biological and engineering applications, especially in micro-nanofluid, have been developed. For example, development of optically driven micromotors, which has an important role in microfluidic applications, has vastly been considered. Despite extensive experimental studies in this field, there is a lack of theoretical work that can verify and analyze these observations. This work develops a dynamic model to simulate trapping and controlled rotation of a microscale rod under influence of the optical trapping forces. The laser beam, used in line optical tweezers with a varying trap's length, was modeled based on a ray-optics approach. Herein, the effects of viscosity of the surrounding fluid (water), gravity, and buoyancy were included in the proposed model. The predicted results are in overall agreement with the experimental observation, which make the theoretical model be a viable tool for investigating the dynamic behavior of small size objects manipulated by optical tweezers in fluid environments. This material is based upon work supported by the National Science Foundation under Grant No. MCB-1148541.

  12. Dynamics of the envelope of a rapidly rotating star or giant planet in gravitational contraction

    CERN Document Server

    Hypolite, Delphine

    2014-01-01

    We wish to understand the processes that control the fluid flows of a gravitationally contracting and rotating star or giant planet. We consider a spherical shell containing an incompressible fluid that is slowly absorbed by the core so as to mimick gravitational contraction. We also consider the effects of a stable stratification that may also modify the dynamics of a pre-main sequence star of intermediate mass. This simple model reveals the importance of both the Stewartson layer attached to the core and the boundary conditions met by the fluid at the surface of the object. In the case of a pre-main sequence star of intermediate mass where the envelope is stably stratified, shortly after the birth line, the spin-up flow driven by contraction overwhelms the baroclinic flow that would take place otherwise.This model also shows that for a contracting envelope, a self-similar flow of growing amplitude controls the dynamics. It suggests that initial conditions on the birth line are most probably forgotten. Final...

  13. A STELLA model to estimate water and nitrogen dynamics in a short-rotation woody crop plantation

    Science.gov (United States)

    Ying Ouyang; Jiaen Zhang; Theodor D. Leininger; Brent R. Frey

    2015-01-01

    Although short-rotation woody crop biomass production technology has demonstrated a promising potential to supply feedstocks for bioenergy production, the water and nutrient processes in the woody crop planation ecosystem are poorly understood. In this study, a computer model was developed to estimate the dynamics of water and nitrogen (N) species (e.g., NH4...

  14. Anisotropic Rotational Diffusion Studied by Nuclear Spin Relaxation and Molecular Dynamics Simulation: An Undergraduate Physical Chemistry Laboratory

    Science.gov (United States)

    Fuson, Michael M.

    2017-01-01

    Laboratories studying the anisotropic rotational diffusion of bromobenzene using nuclear spin relaxation and molecular dynamics simulations are described. For many undergraduates, visualizing molecular motion is challenging. Undergraduates rarely encounter laboratories that directly assess molecular motion, and so the concept remains an…

  15. Visuomotor control of human adaptive locomotion: Understanding the anticipatory nature

    Directory of Open Access Journals (Sweden)

    Takahiro eHiguchi

    2013-05-01

    Full Text Available To maintain balance during locomotion, the central nervous system (CNS accommodates changes in the constraints of spatial environment (e.g., existence of an obstacle or changes in the surface properties. Locomotion while modifying the basic movement patterns in response to such constraints is referred to as adaptive locomotion. The most powerful means of ensuring balance during adaptive locomotion is to visually perceive the environmental properties at a distance and modify the movement patterns in an anticipatory manner to avoid perturbation altogether. For this reason, visuomotor control of adaptive locomotion is characterized, at least in part, by its anticipatory nature. The purpose of the present article is to review the relevant studies which revealed the anticipatory nature of the visuomotor control of adaptive locomotion. The anticipatory locomotor adjustments for stationary and changeable environment, as well as the spatio-temporal patterns of gaze behavior to support the anticipatory locomotor adjustments are described. Such description will clearly show that anticipatory locomotor adjustments are initiated when an object of interest (e.g., a goal or obstacle still exists in far space. This review also show that, as a prerequisite of anticipatory locomotor adjustments, environmental properties are accurately perceived from a distance in relation to individual’s action capabilities.

  16. Dynamic properties of the human vestibulo-ocular reflex during head rotations in roll

    Science.gov (United States)

    Seidman, S. H.; Leigh, R. J.; Tomsak, R. L.; Grant, M. P.; Dell'Osso, L. F.

    1995-01-01

    We investigated the dynamic properties of the human vestibulo-ocular reflex (VOR) during roll head rotations in three human subjects using the magnetic search coil technique. In the first of two experiments, we quantify the behavior of the ocular motor plant in the torsional plane. The subject's eye was mechanically displaced into intorsion, extorsion or abduction, and the dynamic course of return of the eye to its resting position was measured. The mean predominant time constants of return were 210 msec from intorsion, 83 msec from extorsion, and 217 msec from abduction, although there was considerable variability of results from different trials and subjects. In the second experiment, we quantify the efficacy of velocity-to-position integration of the vestibular signal. Position-step stimuli were used to test the torsional or horizontal VOR, being applied with subjects heads erect or supine. After a torsional position-step, the eye drifted back to its resting position, but after a horizontal position-step the eye held its new horizontal position. To interpret these responses we used a simple model of the VOR with parameters of the ocular motor plant set to values determined during Exp 1. The time constant of the velocity-to-position neural integrator was smaller (typically 2 sec) in the torsional plane than in the horizontal plane (> 20 sec). No disconjugacy of torsional eye movements was observed. Thus, the dynamic properties of the VOR in roll differ significantly from those of the VOR in yaw, reflecting different visual demands placed on this reflex in these two planes.

  17. Dissipative particle dynamics simulation of flow generated by two rotating concentric cylinders: boundary conditions.

    Science.gov (United States)

    Haber, S; Filipovic, N; Kojic, M; Tsuda, A

    2006-10-01

    The dissipative particle dynamics (DPD) method was used to simulate the flow in a system comprised of a fluid occupying the space between two cylinders rotating with equal angular velocities. The fluid, initially at rest, ultimately reaches a steady, linear velocity distribution (a rigid-body rotation). Since the induced flow field is solely associated with the no-slip boundary condition at the walls, we employed this system as a benchmark to examine the effect of bounce-back reflections, specular reflections, and Pivkin-Karniadakis no-slip boundary conditions, upon the steady-state velocity, density, and temperature distributions. An additional advantage of the foregoing system is that the fluid occupies inherently a finite bounded domain so that the results are affected by the prescribed no-slip boundary conditions only. Past benchmark systems such as Couette flow between two infinite parallel plates or Poiseuille flow in an infinitely long cylinder must employ artificial periodic boundary conditions at arbitrary upstream and downstream locations, a possible source of spurious effects. In addition, the effect of the foregoing boundary conditions on the time evolution of the simulated velocity profile was compared with that of the known, time-dependent analytical solution. It was shown that bounce-back reflection yields the best results for the velocity distributions with small fluctuations in density and temperature at the inner fluid domain and larger deviations near the walls. For the unsteady solutions a good fit is obtained if the DPD friction coefficient is proportional to the kinematic viscosity. Based on dimensional analysis and the numerical results a universal correlation is suggested between the friction coefficient and the kinematic viscosity.

  18. Hamiltonian dynamics with a weak noise and the echo effect for the rotator model

    Energy Technology Data Exchange (ETDEWEB)

    Turchetti, Giorgio [Department of Physics, University of Bologna, INFN Sezione di Bologna (Italy); Bassi, Gabriele [Department of Mathematics and Statistics, University of New Mexico, Albuquerque, NM (United States); Bazzani, Armando [Department of Physics, University of Bologna, INFN Sezione di Bologna (Italy); Giorgini, Bruno [Department of Physics, University of Bologna, INFN Sezione di Bologna (Italy); Mais, Helmut [DESY Hamburg (Germany)

    2006-09-15

    We analyse the effect of a weak noise on the Hamiltonian transport from the analytical and numerical viewpoint. A solvable model, the noisy rotator, is proposed to illustrate the basic phenomena. In the absence of noise, the phase space evolution is a shear flow, whose angular correlations decay following a power law, which depends on the smoothness of the initial action distribution. If the action has a fluctuating component, given by a Wiener process, then the angular correlations decay exponentially according to e{sup -{epsilon}{sup 2}}{sup t{sup 3/6}} or faster, where {epsilon} is the noise amplitude. The echo effect is well suited to investigate the competition between the decorrelation due to filamentation and noise. The noisy rotator model allows an exhaustive analytical investigation of the process for a wide class of initial conditions and a generic disturbance. The echo time is proportional to the delay {tau} of the disturbance and its amplitude is proportional to {lambda}{tau}, where {lambda} is the amplitude of the disturbance. The noise reduces the echo amplitude by e{sup -c{epsilon}{sup 2}}{sup t{sup 3}}, where c depends on the Fourier components of the initial angular distribution, and of the disturbance applied at time {tau}. The analytical results, derived in the limit {lambda} {yields} 0, {tau} {yields} {infinity}, with {lambda}{tau} finite and sufficiently small to justify a first-order expansion, are checked numerically. For more realistic models the analytical procedure would provide qualitative results and scaling laws. Quantitative results are obtained by solving the Fokker-Planck equation with a numerical scheme based on splitting: back propagation and biquadratic interpolation for the integrable part, implicit finite difference scheme for the noise component. The application to a noisy pendulum describing the longitudinal dynamics in a particle accelerator is considered, and we determine the value of the noise amplitude {epsilon}, below

  19. Trajectory optimization for dynamic couch rotation during volumetric modulated arc radiotherapy

    Science.gov (United States)

    Smyth, Gregory; Bamber, Jeffrey C.; Evans, Philip M.; Bedford, James L.

    2013-11-01

    Non-coplanar radiation beams are often used in three-dimensional conformal and intensity modulated radiotherapy to reduce dose to organs at risk (OAR) by geometric avoidance. In volumetric modulated arc radiotherapy (VMAT) non-coplanar geometries are generally achieved by applying patient couch rotations to single or multiple full or partial arcs. This paper presents a trajectory optimization method for a non-coplanar technique, dynamic couch rotation during VMAT (DCR-VMAT), which combines ray tracing with a graph search algorithm. Four clinical test cases (partial breast, brain, prostate only, and prostate and pelvic nodes) were used to evaluate the potential OAR sparing for trajectory-optimized DCR-VMAT plans, compared with standard coplanar VMAT. In each case, ray tracing was performed and a cost map reflecting the number of OAR voxels intersected for each potential source position was generated. The least-cost path through the cost map, corresponding to an optimal DCR-VMAT trajectory, was determined using Dijkstra’s algorithm. Results show that trajectory optimization can reduce dose to specified OARs for plans otherwise comparable to conventional coplanar VMAT techniques. For the partial breast case, the mean heart dose was reduced by 53%. In the brain case, the maximum lens doses were reduced by 61% (left) and 77% (right) and the globes by 37% (left) and 40% (right). Bowel mean dose was reduced by 15% in the prostate only case. For the prostate and pelvic nodes case, the bowel V50 Gy and V60 Gy were reduced by 9% and 45% respectively. Future work will involve further development of the algorithm and assessment of its performance over a larger number of cases in site-specific cohorts.

  20. Oxygen-17 NMR in solids by dynamic-angle spinning and double rotation

    Science.gov (United States)

    Chmelka, B. F.; Mueller, K. T.; Pines, A.; Stebbins, J.; Wu, Y.; Zwanziger, J. W.

    1989-05-01

    IT is widely lamented that despite its unqualified success with spin-1/2 nuclei such as 13C, 29Si and31P, the popular NMR technique of magic-angle spinning (MAS) has experienced a somewhat restricted applicability among quadrupolar nuclei such as 17O, 23Na and 27A1 (refs 1-3). The resolution in the central (1/2 lrarr-1/2) transition of these non-integer quadrupolar spins under MAS is thought to be limited primarily by second-order quadrupolar broadening. Such effects of second-order spatial anisotropy cannot be eliminated by rotation about a fixed axis or by multiple-pulse techniques4,5. More general mechanisms of sample reorientation (refs 6-8 and A. Samoson and A. Pines, manuscript in preparation) can, however, make high-resolution NMR of quadrupolar nuclei feasible. MAS is implemented by spinning a sample about a single axis so that second-rank spherical harmonics (which give rise to first-order broadening through anisotropy of electrical and magnetic interactions) are averaged away. But dynamic-angle-spinning (DAS) and double-rotation (DOR) NMR involve spinning around two axes, averaging away both the second- and fourth-rank spherical harmonics, which are responsible for second-order broadening. Here we present the application of these new techniques to 17O in two minerals, cristobalite (SiO2) and diopside (CaMgSi2O6). This work goes beyond previous results on 23Na (ref. 8) by showing the first experimental results using DAS and by demonstrating the application of DOR to the resolution of distinct oxygen sites in an important class of oxide materials.

  1. The method of the gas-dynamic centrifugal compressor stage characteristics recalculation for variable rotor rotational speeds and the rotation angle of inlet guide vanes blades if the kinematic and dynamic similitude conditions are not met

    Science.gov (United States)

    Vanyashov, A. D.; Karabanova, V. V.

    2017-08-01

    A mathematical description of the method for obtaining gas-dynamic characteristics of a centrifugal compressor stage is proposed, taking into account the control action by varying the rotor speed and the angle of rotation of the guide vanes relative to the "basic" characteristic, if the kinematic and dynamic similitude conditions are not met. The formulas of the correction terms for the non-dimensional coefficients of specific work, consumption and efficiency are obtained. A comparative analysis of the calculated gas-dynamic characteristics of a high-pressure centrifugal stage with experimental data is performed.

  2. Effects of asymmetric coupling and self-coupling on metastable dynamical transient rotating waves in a ring of sigmoidal neurons.

    Science.gov (United States)

    Horikawa, Yo

    2014-05-01

    Transient rotating waves in a ring of sigmoidal neurons with asymmetric bidirectional coupling and self-coupling were studied. When a pair of stable steady states and an unstable traveling wave coexisted, rotating waves propagating in a ring were generated in transients. The pinning (propagation failure) of the traveling wave occurred in the presence of asymmetric coupling and self-coupling, and its conditions were obtained. A kinematical equation for the propagation of wave fronts of the traveling and rotating waves was then derived for a large output gain of neurons. The kinematical equation showed that the duration of transient rotating waves increases exponentially with the number of neurons as that in a ring of unidirectionally coupled neurons (metastable dynamical transients). However, the exponential growth rate depended on the asymmetry of bidirectional coupling and the strength of self-coupling. The rate was equal to the propagation time of the traveling wave (a reciprocal of the propagation speed), and it increased near pinned regions. Then transient rotating waves could show metastable dynamics (extremely long duration) even in a ring of a small number of neurons. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Rotating flow

    CERN Document Server

    Childs, Peter R N

    2010-01-01

    Rotating flow is critically important across a wide range of scientific, engineering and product applications, providing design and modeling capability for diverse products such as jet engines, pumps and vacuum cleaners, as well as geophysical flows. Developed over the course of 20 years' research into rotating fluids and associated heat transfer at the University of Sussex Thermo-Fluid Mechanics Research Centre (TFMRC), Rotating Flow is an indispensable reference and resource for all those working within the gas turbine and rotating machinery industries. Traditional fluid and flow dynamics

  4. Effects of context on visuomotor interference depends on the perspective of observed actions.

    Directory of Open Access Journals (Sweden)

    Marta Bortoletto

    Full Text Available Visuomotor interference occurs when the execution of an action is facilitated by the concurrent observation of the same action and hindered by the concurrent observation of a different action. There is evidence that visuomotor interference can be modulated top-down by higher cognitive functions, depending on whether own performed actions or observed actions are selectively attended. Here, we studied whether these effects of cognitive context on visuomotor interference are also dependent on the point-of-view of the observed action. We employed a delayed go/no-go task known to induce visuomotor interference. Static images of hand gestures in either egocentric or allocentric perspective were presented as "go" stimuli after participants were pre-cued to prepare either a matching (congruent or non-matching (incongruent action. Participants performed this task in two different cognitive contexts: In one, they focused on the visual image of the hand gesture shown as the go stimulus (image context, whereas in the other they focused on the hand gesture they performed (action context. We analyzed reaction times to initiate the prepared action upon presentation of the gesture image and found evidence of visuomotor interference in both contexts and for both perspectives. Strikingly, results show that the effect of cognitive context on visuomotor interference also depends on the perspective of observed actions. When focusing on own-actions, visuomotor interference was significantly less for gesture images in allocentric perspective than in egocentric perspective; when focusing on observed actions, visuomotor interference was present regardless of the perspective of the gesture image. Overall these data suggest that visuomotor interference may be modulated by higher cognitive processes, so that when we are specifically attending to our own actions, images depicting others' actions (allocentric perspective have much less interference on our own actions.

  5. Interplay of domain walls and magnetization rotation on dynamic magnetization process in iron/polymer-matrix soft magnetic composites

    Science.gov (United States)

    Dobák, Samuel; Füzer, Ján; Kollár, Peter; Fáberová, Mária; Bureš, Radovan

    2017-03-01

    This study sheds light on the dynamic magnetization process in iron/resin soft magnetic composites from the viewpoint of quantitative decomposition of their complex permeability spectra into the viscous domain wall motion and magnetization rotation. We present a comprehensive view on this phenomenon over the broad family of samples with different average particles dimension and dielectric matrix content. The results reveal the pure relaxation nature of magnetization processes without observation of spin resonance. The smaller particles and higher amount of insulating resin result in the prevalence of rotations over domain wall movement. The findings are elucidated in terms of demagnetizing effects rising from the heterogeneity of composite materials.

  6. Bacterial community dynamics in a rotating biological contactor treating 2-fluorophenol-containing wastewater.

    Science.gov (United States)

    Duque, Anouk F; Bessa, Vânia S; Castro, Paula M L

    2014-01-01

    One of the main factors affecting the performance of rotating biological contactors (RBC) is the biofilm characteristics. Therefore, a deep understanding of the microbial population dynamics and structure of the biofilm is mandatory if optimization of organic matter and nutrients removal is targeted. This study focused on the effects of organic shock loads of 2-fluorophenol (2-FP) on the microbial diversity present in an RBC biofilm. The RBC was seeded with activated sludge from a conventional wastewater treatment plant and was operated during 496 days. During the first 126 days, the RBC was subjected to intermittent 2-FP shocks of 25 mg l(-1) and no degradation occurred. Therefore, the reactor was subsequently augmented with a 2-FP-degrading strain (FP1). Afterwards, the RBC had a stable performance when subjected to 2-FP shocks up to 50 mg l(-1) and to a starvation period, as indicated by removal of the compound. Denaturing gradient gel electrophoresis (DGGE) revealed large shifts in microbial communities present in the first and fifth stages, although no clear relation between the sample collection time and spatial factor was found. Phylogenetic affiliation of some predominant members was assessed by direct sequencing of correspondent DGGE bands. Affiliations to α-, β- and δ-Proteobacteria were found. Several bacterial strains isolated from the reactor showed capacity for 2-FP degradation. Strain FP1 was successfully recovered from the biofilm by plating and by DGGE, reinforcing that bioaugmentation was successfully achieved.

  7. Tailoring porosity and rotational dynamics in a series of octacarboxylate metal-organic frameworks.

    Science.gov (United States)

    Moreau, Florian; Kolokolov, Daniil I; Stepanov, Alexander G; Easun, Timothy L; Dailly, Anne; Lewis, William; Blake, Alexander J; Nowell, Harriott; Lennox, Matthew J; Besley, Elena; Yang, Sihai; Schröder, Martin

    2017-03-21

    Modulation and precise control of porosity of metal-organic frameworks (MOFs) is of critical importance to their materials function. Here we report modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-organic cages. Owing to the high ligand connectivity, these MOFs do not show interpenetration, and are robust structures that have permanent porosity. Interestingly, activated MFM-185a shows a high Brunauer-Emmett-Teller (BET) surface area of 4,734 m(2) g(-1) for an octacarboxylate MOF. These MOFs show remarkable CH4 and CO2 adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH4 capacities of 0.24 g g(-1) and 163 vol/vol (298 K, 5-65 bar) recorded for MFM-185a due to selective elongation of tubular cages. The dynamics of molecular rotors in deuterated MFM-180a-d16 and MFM-181a-d16 were investigated by variable-temperature (2)H solid-state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Analysis of the flipping modes of the mobile phenyl groups, their rotational rates, and transition temperatures paves the way to controlling and understanding the role of molecular rotors through design of organic linkers within porous MOF materials.

  8. Femtosecond Raman induced polarization spectroscopy studies of coherent rotational dynamics in molecular fluids

    Energy Technology Data Exchange (ETDEWEB)

    Morgen, Michael Mark [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1997-05-01

    We develop a polarization-sensitive femtosecond pump probe technique, Raman induced polarization spectroscopy (RIPS), to study coherent rotation in molecular fluids. By observing the collisional dephasing of the coherently prepared rotational states, we are able to extract information concerning the effects of molecular interactions on the rotational motion. The technique is quite sensitive because of the zero background detection method, and is also versatile due to its nonresonant nature.

  9. Exploiting the gain-modulation mechanism in parieto-motor neurons: application to visuomotor transformations and embodied simulation.

    Science.gov (United States)

    Mahé, Sylvain; Braud, Raphaël; Gaussier, Philippe; Quoy, Mathias; Pitti, Alexandre

    2015-02-01

    The so-called self-other correspondence problem in imitation demands to find the transformation that maps the motor dynamics of one partner to our own. This requires a general purpose sensorimotor mechanism that transforms an external fixation-point (partner's shoulder) reference frame to one's own body-centered reference frame. We propose that the mechanism of gain-modulation observed in parietal neurons may generally serve these types of transformations by binding the sensory signals across the modalities with radial basis functions (tensor products) on the one hand and by permitting the learning of contextual reference frames on the other hand. In a shoulder-elbow robotic experiment, gain-field neurons (GF) intertwine the visuo-motor variables so that their amplitude depends on them all. In situations of modification of the body-centered reference frame, the error detected in the visuo-motor mapping can serve then to learn the transformation between the robot's current sensorimotor space and the new one. These situations occur for instance when we turn the head on its axis (visual transformation), when we use a tool (body modification), or when we interact with a partner (embodied simulation). Our results defend the idea that the biologically-inspired mechanism of gain modulation found in parietal neurons can serve as a basic structure for achieving nonlinear mapping in spatial tasks as well as in cooperative and social functions.

  10. Effect of surface tension on the dynamical behavior of bubble in rotating fluids under low gravity environment

    Science.gov (United States)

    Hung, R. J.; Tsao, Y. D.; Leslie, Fred W.; Hong, B. B.

    1988-01-01

    Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) linear functions of increasing and decreasing gravity enviroment in high and low rotating cylidner speeds, (3) step functions of spin-up and spin-down in a low gravity environment, and (4) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie (1988), and Hung et al. (1988).

  11. Dynamical and statistical phenomena of circulation and heat transfer in periodically forced rotating turbulent Rayleigh-Benard convection

    CERN Document Server

    Sterl, Sebastian; Zhong, Jin-Qiang

    2016-01-01

    In this paper, we present results from an experimental study into turbulent Rayleigh-Benard convection forced externally by periodically modulated unidirectional rotation rates. We find that the azimuthal rotation velocity $\\dot{\\theta}$(t) and thermal amplitude $\\delta$(t) of the large-scale circulation (LSC) are modulated by the forcing, exhibiting a variety of dynamics including increasing phase delays and a resonant peak in the amplitude of $\\dot{\\theta}$(t). We also focus on the influence of modulated rotation rates on the frequency of occurrence $\\eta$ of stochastic cessation/reorientation events, and on the interplay between such events and the periodically modulated response of $\\dot{\\theta}$(t). Here we identify a mechanism by which $\\eta$ can be amplfied by the modulated response and these normally stochastic events can occur with high regularity. We provide a modeling framework that explains the observed amplitude and phase responses, and extend this approach to make predictions for the occurrence ...

  12. Dynamic response of the occipito-atlanto-axial (C0-C1-C2) complex in right axial rotation.

    Science.gov (United States)

    Chang, H; Gilbertson, L G; Goel, V K; Winterbottom, J M; Clark, C R; Patwardhan, A

    1992-05-01

    The torque-angular deformation in right axial rotation until failure of the ligamentous occipito-atlanto-axial complex subjected to variable loading rate (dynamic) axial torque was characterized using a biaxial MTS system. A special fixture and gear box that permitted right axial rotation of the specimen until failure without imposing any additional constraints were used to obtain the data. The specimens were divided into three groups and tested until failure at three different dynamic loading rates: 50, 100, and 400 degrees/s. A previous study by the authors provided data for quasi-static (4 degrees/s) loading conditions. The torque versus rotation curves can be divided into two straight regions and two transition zones. The plots clearly indicated that at loading rates higher than 4 degrees/s, the specimens became stiffer in the region of steadily increasing resistance prior to failure. The increase in stiffness was maximum at 100 degrees/s. The stiffness decreased somewhat at 400 degrees/s in comparison with 100 degrees/s, but this decrease was not significant. The resulting torque-right axial rotation curves were also examined to estimate the magnitude of maximum resistance (torque) and the corresponding angular rotation value. The average maximum resistance torque increased from 13.6 Nm at 4 degrees/s to 27.8 Nm at 100 degrees/s. The corresponding right angular rotation data (65-78 degrees), however, did not show any significant variation with loading rate. Posttest dissection of the specimens indicated that the type of injury observed was related to the rate of axial loading imposed on a specimen during testing.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Real-time observation of ultrafast dynamics of individual rotational states in a molecular wavepacket with strong-field-ionization-induced nitrogen lasing

    CERN Document Server

    Zeng, Bin; Li, Guihua; Yao, Jinping; Zhang, Haisu; Ni, Jielei; Jing, Chenrui; Xie, Hongqiang; Cheng, Ya

    2014-01-01

    Molecular rotational spectroscopy based on strong-field-ionization-induced nitrogen laser is employed to investigate the time evolution of the rotational wave packet composed by a coherent superposition of quantum rotational states created in a field-free molecular alignment. We show that this technique uniquely allows real-time observation of the ultrafast dynamics of the individual rotational states in the rotational wavepacket. Our analysis also shows that there exist two channels of generation of the nitrogen laser, shedding new light on the population inversion mechanism behind the air laser generated by intense femtosecond laser pulses.

  14. Consolidation of visuomotor adaptation memory with consistent and noisy environments.

    Science.gov (United States)

    Maeda, Rodrigo S; McGee, Steven E; Marigold, Daniel S

    2017-01-01

    Our understanding of how we learn and retain motor behaviors is still limited. For instance, there is conflicting evidence as to whether the memory of a learned visuomotor perturbation consolidates; i.e., the motor memory becomes resistant to interference from learning a competing perturbation over time. Here, we sought to determine the factors that influence consolidation during visually guided walking. Subjects learned a novel mapping relationship, created by prism lenses, between the perceived location of two targets and the motor commands necessary to direct the feet to their positions. Subjects relearned this mapping 1 wk later. Different groups experienced protocols with or without a competing mapping (and with and without washout trials), presented either on the same day as initial learning or before relearning on day 2 We tested identical protocols under constant and noisy mapping structures. In the latter, we varied, on a trial-by-trial basis, the strength of prism lenses around a non-zero mean. We found that a novel visuomotor mapping is retained at least 1 wk after initial learning. We also found reduced foot-placement error with relearning in constant and noisy mapping groups, despite learning a competing mapping beforehand, and with the exception of one protocol, with and without washout trials. Exposure to noisy mappings led to similar performance on relearning compared with the equivalent constant mapping groups for most protocols. Overall, our results support the idea of motor memory consolidation during visually guided walking and suggest that constant and noisy practices are effective for motor learning.

  15. Translational and rotational dynamics of water contained in aged Portland cement pastes studied by quasi-elastic neutron scattering.

    Science.gov (United States)

    Li, Hua; Zhang, Li-Li; Yi, Zhou; Fratini, Emiliano; Baglioni, Piero; Chen, Sow-Hsin

    2015-08-15

    Cement is a widely used construction material in the world. The quality and durability of aged cement pastes have a strong relationship with the water contained in it. The translational and rotational dynamics of water in ordinary Portland cement (OPC) pastes cured for 7, 14 and 30days were studied by analyzing Quasi-elastic Neutron Scattering (QENS) data. The effect of a new super-plasticizer (SP) additive was also studied by comparing the samples with and without the additive. By fitting the QENS spectra with the Jump-diffusion and Rotation-diffusion Model (JRM), six important parameters including the bound water index (BWI), the self-diffusion coefficient, D(t), the average residence time, τ0, the rotational diffusion constant, D(r), the rotational residence time, τ(r), and the mean squared displacement (MSD), 〈u(2)〉, were obtained. From these parameters, we can quantitatively follow the evolution of the bound water fraction (BWI). We can clearly see the different time ranges for the translational and rotational dynamics of water contained in the OPC pastes by τ0 and τ(r). From the MSD values compared with those of molecular dynamics simulation, we can distinguish between immobile water (mainly bound water) and mobile water, which includes confined water and ultraconfined water. Furthermore, by the fitted parameters' values and their change of slopes with increasing setting time for cement pastes with and without additive SP, it becomes clear that the effect of additive SP is to make the mobile water more confined and induce a more uniform the aging process during the evolution of the OPC pastes.

  16. Dynamic Time-Resolved Chirped-Pulse Rotational Spectroscopy of Vinyl Cyanide Photoproducts in a Room Temperature Flow Reactor

    Science.gov (United States)

    Zaleski, Daniel P.; Prozument, Kirill

    2017-06-01

    Chirped-pulsed (CP) Fourier transform rotational spectroscopy invented by Brooks Pate and coworkers a decade ago is an attractive tool for gas phase chemical dynamics and kinetics studies. A good reactor for such a purpose would have well-defined (and variable) temperature and pressure conditions to be amenable to accurate kinetic modeling. Furthermore, in low pressure samples with large enough number of molecular emitters, reaction dynamics can be observable directly, rather than mediated by supersonic expansion. In the present work, we are evaluating feasibility of in situ time-resolved CP spectroscopy in a room temperature flow tube reactor. Vinyl cyanide (CH_2CHCN), neat or mixed with inert gasses, flows through the reactor at pressures 1-50 μbar (0.76-38 mTorr) where it is photodissociated by a 193 nm laser. Millimeter-wave beam of the CP spectrometer co-propagates with the laser beam along the reactor tube and interacts with nascent photoproducts. Rotational transitions of HCN, HNC, and HCCCN are detected, with ≥10 μs time-steps for 500 ms following photolysis of CH_2CHCN. The post-photolysis evolution of the photoproducts' rotational line intensities is investigated for the effects of rotational and vibrational thermalization of energized photoproducts. Possible contributions from bimolecular and wall-mediated chemistry are evaluated as well.

  17. Characteristic dynamic modes and domain-wall motion in magnetic nanotubes excited by resonant rotating magnetic fields

    Science.gov (United States)

    Yang, Jaehak; Kim, Junhoe; Kim, Bosung; Cho, Young-Jun; Lee, Jae-Hyeok; Kim, Sang-Koog

    2016-07-01

    We performed micromagnetic numerical calculations to explore a cylindrical nanotube's magnetization dynamics and domain-wall (DW) motions driven by eigen-circular-rotating magnetic fields of different frequencies. We discovered the presence of two different localized DW oscillations as well as asymmetric ferromagnetic resonance precession and azimuthal spin-wave modes at the corresponding resonant frequencies of the circular-rotating fields. Associated with these intrinsic modes, there exist very contrasting DW motions of different speed and propagation direction for a given DW chirality. The direction and speed of the DW propagation were found to be controllable according to the rotation sense and frequency of noncontact circular-rotating fields. Furthermore, spin-wave emissions from the moving DW were observed at a specific field frequency along with their Doppler effect. This work furthers the fundamental understanding of soft magnetic nanotubes' intrinsic dynamic modes and spin-wave emissions and offers an efficient means of manipulating the speed and direction of their DW propagations.

  18. Dynamical and secular instability of a self-gravitating rotating cylinder in a toroidal magnetic field

    Science.gov (United States)

    Luyten, P. J.

    1988-02-01

    The oscillations and stability of a homogeneous self-gravitating rotating cylinder in a toroidal magnetic field are investigated. It is assumed that the field is proportional to the distance to the axis of the cylinder. We show the existence of four infinite discreta spectra of magnetic (or rotational) modes. Rotation stabilizes the magnetic m = 1 instability. The magnetic field decreases the growth rate of rotational instability and reduces the interval of unstable wavenumbers. If m = 1, instability always occurs with the exception of the equipartition state. If m> 1, the instability can be suppressed by a sufficiently large magnetic field. Resistivity decreases the growth rate of magnetic instability, but increases the growth rate of rotational instability. For zero wavenumber perturbations secular instability occurs due to the action of resistivity before a neutral point is attained where a second secular instabiliity initiates due to the action of resistivity

  19. Revisit of rotational dynamics of Asteroid 4179 Toutatis from Chang'e-2's flyby

    Science.gov (United States)

    Zhao, Yuhui; Hu, Shoucun; Ji, Jianghui

    2016-01-01

    This paper presents analysis of the rotational parameters of Toutatis based on the observational results from Chang'e-2's close flyby. The 3-D shape model derived from ground-based radar observation is used to calculate the 3-1-3 Euler angles at the flyby epoch, which are evaluated to be -20.1° +/- 1°, 27.6° +/- 1° and 42.2° +/- 1°. The large amplitude of Toutatis' tumbling attitude is demonstrated to be the result of the large deviation of the angular momentum axis and the rotational axis. Two rotational periods are evaluated to be 5.38+/-0.03 days for rotation about the long axis and 7.40+/-0.03 days for precession of the long axis about the angular momentum vector based on Fourier analysis. These results provide a further understanding of rotational state of Toutatis.

  20. Revisit of rotational dynamics of Asteroid 4179 Toutatis from Chang'e-2's flyby

    CERN Document Server

    Zhao, Yuhui; Ji, Jianghui

    2015-01-01

    This paper presents analysis of the rotational parameters of Toutatis based on the observational results from Chang'e-2's close flyby. The 3-D shape model derived from ground-based radar observation is used to calculate the 3-1-3 Euler angles at the flyby epoch, which are evaluated to be $-20.1^\\circ\\pm1^\\circ$, $27.6^\\circ\\pm1^\\circ$ and $42.2^\\circ\\pm1^\\circ$. The large amplitude of Toutatis' tumbling attitude is demonstrated to be the result of the large deviation of the angular momentum axis and the rotational axis. Two rotational periods are evaluated to be $5.38\\pm0.03$ days for rotation about the long axis and $7.40\\pm0.03$ days for precession of the long axis about the angular momentum vector based on Fourier analysis. These results provide a further understanding of rotational state of Toutatis.

  1. Age-related variations of visuo-motor adaptation beyond explicit knowledge

    Directory of Open Access Journals (Sweden)

    Herbert eHeuer

    2014-07-01

    Full Text Available Visuo-motor adaptation suffers at older working age. The age-related decline of behavioural adjustments is accompanied by reduced explicit knowledge of the visuo-motor transformation. It disappears when explicit knowledge is kept constant across the age range, except for particularly high levels of explicit knowledge. According to these findings, at older adult age both the acquisition of explicit knowledge and its application for strategic corrections become poorer. Recently it has been posited that visuo-motor adaptation can involve model-free reinforcement mechanisms of learning in addition to model-based mechanisms. We tested whether age-related declines of reinforcement learning can also contribute to the age-related changes of visuo-motor adaptation. Therefore we enhanced the contribution of reinforcement learning to visuo-motor adaptation by way of introducing salient markers of success and failure during practice. With such modified practice conditions, there were residual age-related variations of behavioural adjustments at all levels of explicit knowledge, even when explicit knowledge was absent. The residual age-related variations were observed for practiced target directions only, but not for new target directions. These findings are consistent with an age-related decline of model-free reinforcement learning as a third factor in the age-related decline of visuo-motor adaptation. Under practice conditions, which spur model-free reward-based learning, this factor adds to the decrements of the acquisition of explicit knowledge and its use for strategic corrections.

  2. Visuomotor performance based on peripheral vision is impaired in the visual form agnostic patient DF.

    Science.gov (United States)

    Hesse, Constanze; Ball, Keira; Schenk, Thomas

    2012-01-01

    The perception-action model states that visual information is processed in different cortical areas depending on the purpose for which the information is acquired. Specifically, it was suggested that the ventral stream mediates visual perception, whereas the dorsal stream primarily processes visual information for the guidance of actions (Goodale & Milner, 1992). Evidence for the model comes from patient studies showing that patients with ventral stream damage (visual form agnosia) and patients with dorsal stream damage (optic ataxia) show divergent performance in action and perception tasks. Whereas DF, a patient suffering from visual form agnosia, was found to perform well in visuomotor tasks despite her inability to use vision for perceptual tasks, patients with optic ataxia show usually the opposite pattern, i.e. good perception but impaired visuomotor control. The finding that both disorders seem to provoke a mirror-reversed pattern of spared and impaired visual functions, led to the belief that optic ataxia and visual form agnosia can be considered as complementary disorders. However, the visuomotor performance of patients with optic ataxia is typically only impaired when they are tested in visual periphery while being often preserved when tested in central vision. Here, we show that DF's visuomotor performance is also only preserved when the target is presented centrally. Her reaching and grasping movements to targets in peripheral vision are abnormal. Our findings indicate that DF's visuomotor performance is quite similar to the visuomotor performance of patients with optic ataxia which undermines previous suggestions that the two disorders form a double-dissociation.

  3. Dynamic Model of a Rotating Flexible Arm-Flexible Root Mechanism Driven by a Shaft Flexible in Torsion

    Directory of Open Access Journals (Sweden)

    S.Z. Ismail

    2006-01-01

    Full Text Available This paper presents a dynamic model of a rotating flexible beam carrying a payload at its tip. The model accounts for the driving shaft and the arm root flexibilities. The finite element method and the Lagrangian dynamics are used in deriving the equations of motion with the small deformation theory assumptions and the Euler-Bernoulli beam theory. The obtained model is a nonlinear-coupled system of differential equations. The model is simulated for different combinations of shaft and root flexibilities and arm properties. The simulation results showed that the root flexibility is an important factor that should be considered in association with the arm and shaft flexibilities, as its dynamics influence the motor motion. Moreover, the effect of system non-linearity on the dynamic behavior is investigated by simulating the equivalent linearized system and it was found to be an important factor that should be considered, particularly when designing a control strategy for practical implementation.

  4. Dynamic detection of a single bacterium: nonlinear rotation rate shifts of driven magnetic microsphere stages

    CERN Document Server

    McNaughton, B H; Kopelman, R; Agayan, Rodney R.; Kopelman, Raoul; Naughton, Brandon H. Mc

    2006-01-01

    We report on a new technique which was used to detect single Escherichia coli that is based on the changes in the nonlinear rotation of a magnetic microsphere driven by an external magnetic field. The presence of one Escherichia Coli bacterium on the surface of a 2.0 micron magnetic microsphere caused an easily measurable change in the drag of the system and, therefore, in the nonlinear rotation rate. The straight-forward measurement uses standard microscopy techniques and the observed average shift in the nonlinear rotation rate changed by a factor of ~3.8.

  5. Coupling between internal dynamics and rotational diffusion in the presence of exchange between discrete molecular conformations.

    Science.gov (United States)

    Ryabov, Yaroslav; Clore, G Marius; Schwieters, Charles D

    2012-01-21

    We present a general formalism for the computation of orientation correlation functions involving a molecular system undergoing rotational diffusion in the presence of transitions between discrete conformational states. In this formalism, there are no proscriptions on the time scales of conformational rearrangement relative to that for rotational diffusion, and the rotational diffusion tensors of the different states can be completely arbitrary. Although closed-form results are limited to the frequency domain, this is generally useful for many spectroscopic observables as the result allows the computation of the spectral density function. We specialize the results for the computation of the frequency-domain correlation function associated with the NMR relaxation.

  6. Rotational elasticity

    Science.gov (United States)

    Vassiliev, Dmitri

    2017-04-01

    We consider an infinite three-dimensional elastic continuum whose material points experience no displacements, only rotations. This framework is a special case of the Cosserat theory of elasticity. Rotations of material points are described mathematically by attaching to each geometric point an orthonormal basis that gives a field of orthonormal bases called the coframe. As the dynamical variables (unknowns) of our theory, we choose the coframe and a density. We write down the general dynamic variational functional for our rotational theory of elasticity, assuming our material to be physically linear but the kinematic model geometrically nonlinear. Allowing geometric nonlinearity is natural when dealing with rotations because rotations in dimension three are inherently nonlinear (rotations about different axes do not commute) and because there is no reason to exclude from our study large rotations such as full turns. The main result of the talk is an explicit construction of a class of time-dependent solutions that we call plane wave solutions; these are travelling waves of rotations. The existence of such explicit closed-form solutions is a non-trivial fact given that our system of Euler-Lagrange equations is highly nonlinear. We also consider a special case of our rotational theory of elasticity which in the stationary setting (harmonic time dependence and arbitrary dependence on spatial coordinates) turns out to be equivalent to a pair of massless Dirac equations. The talk is based on the paper [1]. [1] C.G.Boehmer, R.J.Downes and D.Vassiliev, Rotational elasticity, Quarterly Journal of Mechanics and Applied Mathematics, 2011, vol. 64, p. 415-439. The paper is a heavily revised version of preprint https://arxiv.org/abs/1008.3833

  7. COMPUTER SIMULATION OF 3-DIMENSIONAL DYNAMIC ASSEMBLY PROCESS OF MECHANICAL ROTATIONAL BODY

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    Focusing on the study of the components of mechanical rotational body,the data structure and algorithm of component model generation are discussed.Some problems in assembly process of 3-dimensional graph of components are studied in great detail.

  8. A Vision-Based Dynamic Rotational Angle Measurement System for Large Civil Structures

    Directory of Open Access Journals (Sweden)

    Jong-Jae Lee

    2012-05-01

    Full Text Available In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with high resolution are in great demand. The proposed system consists of commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router. The calculation of rotation angle is obtained by using image processing techniques with pre-measured calibration parameters. Several laboratory tests were conducted to verify the performance of the proposed system. Compared with the commercial rotation angle measurement, the results of the system showed very good agreement with an error of less than 1.0% in all test cases. Furthermore, several tests were conducted on the five-story modal testing tower with a hybrid mass damper to experimentally verify the feasibility of the proposed system.

  9. Nonlinear Dynamic Analysis of Functionally Graded Timoshenko Beam fixed to a Rotating Hub

    Science.gov (United States)

    Panigrahi, B.; Pohit, G.

    2016-08-01

    The present work accounts centrifugal stiffening effect on the nonlinear vibration response of an FGM Timoshenko beam. Analysis is carried out for a cantilever beam fixed with a rotating hub. Material is assumed to have a gradation relation along the depth of the beam. Centrifugal force and axial displacement raised due to the rotating hub is incorporated in the strain energy equations. Subsequent to this, an iterative technique is employed to obtain amplitude dependent vibration response of a rotating Timoshenko beam while material follows a gradation relation along the beam depth. Main objective of the work is to obtain the effects of rotational speeds, hub radius, and different gradation relations on the linear as well as nonlinear frequencies and mode shapes.

  10. Rotational reorientation dynamics of C60 in various solvents. Picosecond transient grating experiments

    Science.gov (United States)

    Rubtsov, I. V.; Khudiakov, D. V.; Nadtochenko, V. A.; Lobach, A. S.; Moravskii, A. P.

    1994-11-01

    The picosecond transient grating technique has been used to study the rotational reorientation of C60 in various solvents: in toluene 7 +/- 1.5 ps, o-dichlorobenzene 10.3 +/- 1.5 ps, o-xylene 13 +/- 2 ps and in decalin 3.5 +/- 1.5 ps. The data obtained cannot be described by hydrodynamic Debye theory. Rough-sphere fluid theory predicts the correct values for C60 rotation in toluene, o-dichlorobenzene and in decalin. The deviations for o-xylene are probably connected with the specifics of the local solvent structure or with the stronger interaction of C60 with solvent molecules. The rotation of C60 in decalin is rapid and approaches the rotation in the gas phase determined by inertia.

  11. Spectral imbalance in the inertial range dynamics of decaying rotating turbulence

    CERN Document Server

    Valente, Pedro C

    2016-01-01

    Direct numerical simulations of homogeneous decaying turbulence with mild background rotation show the existence of a systematic and significant imbalance between the non-linear energy cascade to small scales and its dissipation. By starting the decay from a statistically stationary and fully developed rotating turbulence state, where the dissipation and the energy flux are approximately equal, the data shows a growing imbalance between the two until a maximum is reached when the dissipation is about twice the energy flux. This dichotomy of behaviours during decay is reminiscent of the non-equilibrium and the equilibrium regions previously reported for non-rotating turbulence [P.C. Valente, J.C. Vassilicos, Phys. Rev. Lett. {\\bf 108} 214503 (2012)]. Note, however, that for decaying rotating turbulence the classical scaling of the dissipation rate $\\epsilon \\propto u'^3/L$ (where $u'$ and $L$ are the root mean square fluctuating velocity and the integral length scale, respectively) does not appear to hold duri...

  12. A vision-based dynamic rotational angle measurement system for large civil structures.

    Science.gov (United States)

    Lee, Jong-Jae; Ho, Hoai-Nam; Lee, Jong-Han

    2012-01-01

    In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with high resolution are in great demand. The proposed system consists of commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router. The calculation of rotation angle is obtained by using image processing techniques with pre-measured calibration parameters. Several laboratory tests were conducted to verify the performance of the proposed system. Compared with the commercial rotation angle measurement, the results of the system showed very good agreement with an error of less than 1.0% in all test cases. Furthermore, several tests were conducted on the five-story modal testing tower with a hybrid mass damper to experimentally verify the feasibility of the proposed system.

  13. The fluid dynamic and shear environment in the NASA/JSC rotating-wall perfused-vessel bioreactor

    Science.gov (United States)

    Begley, C. M.; Kleis, S. J.

    2000-01-01

    The rotating-wall perfused-vessel (RWPV) bioreactor, used for both microgravity and Earth-based cell science experiments, is characterized in terms of the fluid dynamic and fluid shear stress environment. A numerical model of the flow field is developed and verified with laser Doppler velocimeter measurements. The effects of changes in operating conditions, including rotation rates and fluid perfusion rates, are investigated with the numerical model. The operating conditions typically used for ground-based experiments (equal rotation of the inner and outer cylinders) leads to flow patterns with relatively poor mass distribution characteristics. Approximately 50% of the inlet-perfused fluid bypasses the bulk of the fluid volume and flows to the perfusion exit. For operating conditions typical in microgravity, small differential rotation rates between the inner and outer cylinders lead to greatly improved flow distribution patterns and very low fluid shear stress levels over a large percentage of the fluid volume. Differences in flow patterns for the different operating conditions are explored. Large differences in the hydrodynamic environments for operating conditions typical of true microgravity and ground-based "microgravity simulations" are demonstrated.

  14. Molecular dynamics simulation of self-rotation effects on ultra-precision polishing of single-crystal copper

    Directory of Open Access Journals (Sweden)

    Yihan Yang

    2013-10-01

    Full Text Available Understanding the behaviors of the material removal mechanism of ultra-precision polishing process has been a critical issue of generating well-formed surface. In order to make clear the abrasive self-rotation effects on material removal at the atomic level, a three-dimensional molecular dynamics (MD model is conducted to study the mechanics of ultra-precision polishing on single-crystal copper with a diamond abrasive and the effects of abrasive self-rotation velocity and direction. Morse potential energy function and EAM potential energy function are applied to model the copper/diamond and copper/copper interactions, respectively. The simulation results show that the deformation mechanism of single-crystal copper is due to the formation and movement of dislocations in the specimen. In addition, with the increasing of abrasive self-rotation velocity, the deformation mechanism falls from cutting to plowing regimes. The abrasive self-rotation velocity and direction have effects on the morphology and quality of the specimen surface, distribution and evolution of defects under the surface of the specimen. Also, the interatomic force between abrasive and specimen is studied to account for the effects of different polishing conditions.

  15. A concise review of dynamical processes in polymorphic environments of a block copolymer: Rotational diffusion and photoisomerization

    Indian Academy of Sciences (India)

    K S Mali; G B Dutt

    2007-03-01

    This article describes our ongoing efforts to understand dynamical processes such as rotational diffusion and photoisomerization in polymorphic environments of a block copolymer. The objective is to explore how the typical properties of a block copolymer solution such as critical micelle temperature (CMT) and temperature-induced sol-gel transition influence the rotational diffusion of hydrophobic solute molecules. Rotational diffusion of solute molecules differs significantly below and above the CMT of a block copolymer solution, while there is no influence of sol-gel transition on solute rotation. This is rationalized on the basis of the site of solubilization of the solute molecules which is the palisade layer of the micelles in both phases and unaffected by gelation. A similar result has been obtained in case of photoisomerization studies carried out with a carbocyanine derivative in the sol and gel phases of the block copolymer. The isomerization studies have been extended to the reverse phases (sol and gel phases) of the block copolymer to explore the nature of the water present in the cores of the reverse micelles. Our results provide evidence for the existence of water droplets with properties resembling bulk water. In essence, we show that despite having vastly differing bulk properties, both the solution and gel phases (normal as well as reverse) offer identical microscopic environment.

  16. Age-related differences in control of a visuomotor coordination task: a preliminary study.

    Science.gov (United States)

    Ryu, Young Uk; Lee, Kyu-Ho; Lee, Hocheol; Park, Jungsik

    2016-04-01

    [Purpose] The purpose of the current study was to examine age-related differences in control of a perception-action coordination skill. We adapted a visuomotor tracking experiment requiring various coordination patterns between a limb's motion and an external signal. [Subjects and Methods] A total of 12 subjects (6 elderly and 6 young) voluntarily participated in the study. The experimental session consisted of 3 trials for 3 different relative phase patterns: 0°, 90°, and 180°, defined by the relationship between the online visual feedback of the joystick motion and the white dot signal. [Results] The 0° and 180° tracking patterns were stable compared with the 90° tracking pattern for both age groups. The present results also showed that the elderly subjects were less stable than were young subjects for all tracking patterns. [Conclusion] The intrinsic coordination dynamics predicted by the Haken-Kelso-Bunz (HKB) mathematical model did not change with age, whereas utilization of visual feedback information declined overall. Further research is needed regarding methods for increasing utilization of visual feedback information from the perspective of rehabilitation.

  17. Non-Markovian dynamics for an open two-level system without rotating wave approximation: indivisibility versus backflow of information

    Science.gov (United States)

    Zeng, H. S.; Tang, N.; Zheng, Y. P.; Xu, T. T.

    2012-10-01

    By use of the recently presented two measures, the indivisibility and the backflow of information, we study the non-Markovianity of the dynamics for a two-level system interacting with a zero-temperature structured environment without using rotating wave approximation (RWA). In the limit of weak coupling between the system and its reservoir, and by expanding the time-convolutionless (TCL) generator to the forth order with respect to the coupling strength, the time-local non-Markovian master equation for the reduced state of the system is derived. Under the secular approximation, the exact analytic solution is obtained and the sufficient and necessary conditions for the indivisibility and the backflow of information for the system dynamics are presented. In the more general case, we investigate numerically the properties of the two measures for the case of Lorentzian reservoir. Our results show the importance of the counter-rotating terms to the short-time-scale non-Markovian behavior of the system dynamics, further expose the relation between the two measures and their rationality as non-Markovian measures. Finally, the complete positivity of the dynamics of the considered system is discussed.

  18. On the role of corotation radius in the low T/W dynamical instability of differentially rotating stars

    Science.gov (United States)

    Yoshida, Shin'ichirou; Saijo, Motoyuki

    2017-04-01

    We investigate the nature of so-called low T/W dynamical instability in a differentially rotating star, by focusing on the role played by the corotation radius of the unstable oscillation modes. A one-dimensional model of linear perturbation, which neglects dependence of variables on the coordinate along the rotational axis of the star, is solved to obtain stable and unstable eigenmodes. A linear eigenmode having a corotation radius, at which azimuthal pattern speed of the mode coincides with the stellar angular velocity, is categorized to either a complex (growing or damping) mode or a purely real mode belonging to a continuous spectrum of frequency. We compute canonical angular momentum and its flux to study eigenmodes with corotation radius. In a dynamically unstable mode, sound wave transports its angular momentum in such a way that the absolute value of the angular momentum is increased on both sides of the corotation radius. We further evaluate growth of amplitude of reflected sound wave incident to a corotation point, and find that the overreflection of the wave and the trapping of it between the corotation radius and the surface of the star may qualitatively explain dependences of eigenfrequencies on the stellar differential rotation. The results suggest that the low T/W instability may be caused by overreflection of sound waves trapped mainly between the surface of the star and a corotation radius.

  19. Path integral molecular dynamics simulation of quasi-free rotational motion of CO doped in a large para-hydrogen cluster

    Science.gov (United States)

    Mizumoto, Yoshihiko; Ohtsuki, Yukiyoshi

    2011-01-01

    Path integral molecular dynamics simulation is used to study the rotational motion of a CO molecule doped in a large para-hydrogen (p-H2) cluster. The quasi-free rotational motion of CO in a p-H2 cluster with a reduced rotational constant is derived from the imaginary-time orientational correlation functions, and is in good agreement with recent experimental observations. We attribute the reduced rotational constant to the low-viscous fluid-like behavior of the host p-H2 cluster.

  20. Controlling the quantum rotational dynamics of a driven planar rotor by rebuilding barriers in the classical phase space

    Indian Academy of Sciences (India)

    ARCHANA SHUKLA; SRIHARI KESHAVAMURTHY

    2017-07-01

    The present work aims to control the rotational excitations of an ac-driven planar rotor, a model for rigid diatomic molecules, by rebuilding barriers in the classical phase space. The barriers are invariant tori with irrational winding ratios which are perturbatively constructed at desired locations in the phase space. Weestablish that constructing such barriers, equivalent to additional weak fields, can efficiently suppress the chaos leading to the control of various processes. The phase space barriers are shown to be effective in controlling the quantum dynamics as well. In particular, the efficiency of the phase space barriers towards controlling dynamical tunneling in the system is explored. Our studies are relevant to understanding the role of the chaotic regions in dynamical tunneling and for molecular alignment using bichromatic fields.

  1. Dynamic motion analysis of dart throwers motion visualized through computerized tomography and calculation of the axis of rotation.

    Science.gov (United States)

    Edirisinghe, Y; Troupis, J M; Patel, M; Smith, J; Crossett, M

    2014-05-01

    We used a dynamic three-dimensional (3D) mapping method to model the wrist in dynamic unrestricted dart throwers motion in three men and four women. With the aid of precision landmark identification, a 3D coordinate system was applied to the distal radius and the movement of the carpus was described. Subsequently, with dynamic 3D reconstructions and freedom to position the camera viewpoint anywhere in space, we observed the motion pathways of all carpal bones in dart throwers motion and calculated its axis of rotation. This was calculated to lie in 27° of anteversion from the coronal plane and 44° of varus angulation relative to the transverse plane. This technique is a safe and a feasible carpal imaging method to gain key information for decision making in future hand surgical and rehabilitative practices.

  2. Dynamics and mechanism of cavitation erosion on perspex and epoxy resins tested in a rotating disk device

    Science.gov (United States)

    Rao, P. V.; Rao, N. S. L.; Rao, B. C. S.

    1982-01-01

    The cavitation erosion behavior including the initiation, dynamics and mechanism of damage process on perspex and epoxy resin specimens tested in a rotating disk device were discussed with respect to exposure time. The inception of erosion always took place at the location nearest to the center of rotation of the disk. Subsequently, as exposure time increased, erosion initiated at other locations as well. Light optical photographs and scanning electron micrographs clearly indicate that most of the material loss appears to occur form the networks of cracks due to their interaction and pits indicate particle debris. The optical degradation (loss of transmittance) on perspex was observed to be more on the rear side than on the front side.

  3. Ab Initio Potential Energy Surfaces and Quantum Dynamics of Rotational Inelastic Processes in the H+ Collision with CS

    CERN Document Server

    Kaur, Rajwant

    2016-01-01

    Rate coefficient for state-to-state rotational transitions in H+ collision with CS has been obtained using accurate quantum dynamical close-coupling calculations to interpret microwave astronomical observations. Accurate three dimensional ab initio potential energy surfaces have been computed for the ground state and low-lying excited states of H+ - CS system using internally contracted MRCI method and aug-cc-pVQZ basis sets. Rotational excitation and deexcitation integral cross sections are computed at low and ultra low collision energies, respectively. Resonances have been observed at very low energies typically below 50 cm-1. Among all the transitions, Deltaj=+1 and Deltaj=-1 are found to be predominant for excitation and deexcitation, respectively. Deexcitation cross section in the ultracold region is found to obey Wigner's threshold law. The magnitude of state-to-state excitation rate obtained is maximum for j'=1 in the temperature range 2-240 K while minimum for deexcitation in ultracold region. The rot...

  4. Structural dynamics of a methionine γ-lyase for calicheamicin biosynthesis: Rotation of the conserved tyrosine stacking with pyridoxal phosphate

    Directory of Open Access Journals (Sweden)

    Hongnan Cao

    2016-05-01

    Full Text Available CalE6 from Micromonospora echinospora is a (pyridoxal 5′ phosphate PLP-dependent methionine γ-lyase involved in the biosynthesis of calicheamicins. We report the crystal structure of a CalE6 2-(N-morpholinoethanesulfonic acid complex showing ligand-induced rotation of Tyr100, which stacks with PLP, resembling the corresponding tyrosine rotation of true catalytic intermediates of CalE6 homologs. Elastic network modeling and crystallographic ensemble refinement reveal mobility of the N-terminal loop, which involves both tetrameric assembly and PLP binding. Modeling and comparative structural analysis of PLP-dependent enzymes involved in Cys/Met metabolism shine light on the functional implications of the intrinsic dynamic properties of CalE6 in catalysis and holoenzyme maturation.

  5. Structural dynamics of a methionine γ-lyase for calicheamicin biosynthesis: Rotation of the conserved tyrosine stacking with pyridoxal phosphate.

    Science.gov (United States)

    Cao, Hongnan; Tan, Kemin; Wang, Fengbin; Bigelow, Lance; Yennamalli, Ragothaman M; Jedrzejczak, Robert; Babnigg, Gyorgy; Bingman, Craig A; Joachimiak, Andrzej; Kharel, Madan K; Singh, Shanteri; Thorson, Jon S; Phillips, George N

    2016-05-01

    CalE6 from Micromonospora echinospora is a (pyridoxal 5' phosphate) PLP-dependent methionine γ-lyase involved in the biosynthesis of calicheamicins. We report the crystal structure of a CalE6 2-(N-morpholino)ethanesulfonic acid complex showing ligand-induced rotation of Tyr100, which stacks with PLP, resembling the corresponding tyrosine rotation of true catalytic intermediates of CalE6 homologs. Elastic network modeling and crystallographic ensemble refinement reveal mobility of the N-terminal loop, which involves both tetrameric assembly and PLP binding. Modeling and comparative structural analysis of PLP-dependent enzymes involved in Cys/Met metabolism shine light on the functional implications of the intrinsic dynamic properties of CalE6 in catalysis and holoenzyme maturation.

  6. Dynamic behavior of a rotating delaminated composite beam including rotary inertia and shear deformation effects

    Directory of Open Access Journals (Sweden)

    Ramazan-Ali Jafari-Talookolaei

    2015-09-01

    Full Text Available A finite element (FE model is developed to study the free vibration of a rotating laminated composite beam with a single delamination. The rotary inertia and shear deformation effects, as well as the bending–extension, bending–twist and extension–twist coupling terms are taken into account in the FE model. Comparison between the numerical results of the present model and the results published in the literature verifies the validity of the present model. Furthermore, the effects of various parameters, such as delamination size and location, fiber orientation, hub radius, material anisotropy and rotating speed, on the vibration of the beam are studied in detail. These results provide useful information in the study of the free vibration of rotating delaminated composite beams.

  7. Combined Néel and Brown rotational Langevin dynamics in magnetic particle imaging, sensing, and therapy

    Energy Technology Data Exchange (ETDEWEB)

    Reeves, Daniel B., E-mail: dbr@Dartmouth.edu [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Weaver, John B. [Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755 (United States); Department of Radiology, Geisel School of Medicine, Hanover, New Hampshire 03755 (United States)

    2015-11-30

    Magnetic nanoparticles have been studied intensely because of their possible uses in biomedical applications. Biosensing using the rotational freedom of particles has been used to detect biomarkers for cancer, hyperthermia therapy has been used to treat tumors, and magnetic particle imaging is a promising new imaging modality that can spatially resolve the concentration of nanoparticles. There are two mechanisms by which the magnetization of a nanoparticle can rotate, a fact that poses a challenge for applications that rely on precisely one mechanism. The challenge is exacerbated by the high sensitivity of the dominant mechanism to applied fields. Here, we demonstrate stochastic Langevin equation simulations for the combined rotation in magnetic nanoparticles exposed to oscillating applied fields typical to these applications to both highlight the existing relevant theory and quantify which mechanism should occur in various parameter ranges.

  8. Structure and internal rotation dynamics of the acetone-neon complex studied by microwave spectroscopy

    Science.gov (United States)

    Gao, Jiao; Seifert, Nathan A.; Thomas, Javix; Xu, Yunjie; Jäger, Wolfgang

    2016-12-01

    The microwave spectra of the van der Waals complexes acetone-20Ne and acetone-22Ne were measured using a cavity-based supersonic jet Fourier-transform microwave spectrometer in the region from 5 to 18 GHz. For these two isotopologues, both c- and weaker a-type transitions were observed. The transitions are split into multiplets due to the internal rotation of the two methyl groups in acetone. Initial electronic structure calculations were performed at the MP2/6-311++g (2d, p) level of theory and the internal rotation barrier height of the methyl groups was calculated to be ∼2.8 kJ/mol. The ab initio rotational constants were the basis for the spectroscopic searches, but the multiplet structures and floppiness of the complex made the quantum number assignment very difficult. The assignment was finally achieved with the aid of constructing closed frequency loops and predicting internal rotation splittings using the XIAM internal rotation program. The acetone methyl group tunneling barrier height was determined experimentally to be 3.10(6) kJ mol-1 [259(5) cm-1] in the acetone-Ne complex, which is lower than in the acetone monomer but comparable to the acetone-Ar complex (Kang et al., 2002). Experimental data and high-level CCSD(T)/aug-cc-pVTZ calculations suggest that the Ne atom lies directly above the plane formed by the carbonyl group and the two carbon-carbon bonds, which is different than the slightly offset position found previously in the acetone-Ar complex. Additionally, ab initio calculations and Quantum Theory of Atoms in Molecules analyses were used to analyze the methyl internal rotation motions in acetone and acetone-Ne.

  9. Gravity Probe-B Spacecraft attitude control based on the dynamics of slosh wave-induced fluid stress distribution on rotating dewar container of cryogenic propellant

    Science.gov (United States)

    Hung, R. J.; Lee, C. C.; Leslie, F. W.

    1991-01-01

    The dynamical behavior of fluids, in particular the effect of surface tension on partially-filled rotating fluids, in a full-scale Gravity Probe-B Spacecraft propellant dewar tank imposed by various frequencies of gravity jitters have been investigated. Results show that fluid stress distribution exerted on the outer and inner walls of rotating dewar are closely related to the characteristics of slosh waves excited on the liquid-vapor interface in the rotating dewar tank. This can provide a set of tool for the spacecraft dynamic control leading toward the control of spacecraft unbalance caused by the uneven fluid stress distribution due to slosh wave excitations.

  10. Testes visuomotores em crianças com estrabismo

    Directory of Open Access Journals (Sweden)

    Jorge Alberto F. Caldeira

    1970-09-01

    Full Text Available Em 43 crianças estrábicas nas quais foi determinado o quociente intelectual foram aplicados os testes visuomotores de Goldstein-Scheerer, Bender-Santucci, lateralidade e estereognosia. Os resultados foram comparados com os obtidos em 44 controles dos mesmos grupos etários e sócio-econômicamente semelhantes. Sugere-se o prosseguimento desta pesquisa com o estudo comparativo entre o teste de Goldstein-Scheerer e o "visual retention test" de Benton (1963 nos quais a análise do fator memória visual pode ser útil para averiguar dificuldades relacionadas com a prontidão para a alfabetização. Sugere-se, também, o estudo de um grupo de crianças em idade escolar com e sem perturbações da motilidade ocular extrínseca para avaliar a influência da escolaridade nos resultados dos testes.

  11. Visuomotor adaptation changes stereoscopic depth perception and tactile discrimination.

    Science.gov (United States)

    Volcic, Robert; Fantoni, Carlo; Caudek, Corrado; Assad, John A; Domini, Fulvio

    2013-10-23

    Perceptual judgments of relative depth from binocular disparity are systematically distorted in humans, despite in principle having access to reliable 3D information. Interestingly, these distortions vanish at a natural grasping distance, as if perceived stereo depth is contingent on a specific reference distance for depth-disparity scaling that corresponds to the length of our arm. Here we show that the brain's representation of the arm indeed powerfully modulates depth perception, and that this internal calibration can be quickly updated. We used a classic visuomotor adaptation task in which subjects execute reaching movements with the visual feedback of their reaching finger displaced farther in depth, as if they had a longer arm. After adaptation, 3D perception changed dramatically, and became accurate at the "new" natural grasping distance, the updated disparity scaling reference distance. We further tested whether the rapid adaptive changes were restricted to the visual modality or were characteristic of sensory systems in general. Remarkably, we found an improvement in tactile discrimination consistent with a magnified internal image of the arm. This suggests that the brain integrates sensory signals with information about arm length, and quickly adapts to an artificially updated body structure. These adaptive processes are most likely a relic of the mechanisms needed to optimally correct for changes in size and shape of the body during ontogenesis.

  12. Elasticity improves handgrip performance and user experience during visuomotor control.

    Science.gov (United States)

    Mace, Michael; Rinne, Paul; Liardon, Jean-Luc; Uhomoibhi, Catherine; Bentley, Paul; Burdet, Etienne

    2017-02-01

    Passive rehabilitation devices, providing motivation and feedback, potentially offer an automated and low-cost therapy method, and can be used as simple human-machine interfaces. Here, we ask whether there is any advantage for a hand-training device to be elastic, as opposed to rigid, in terms of performance and preference. To address this question, we have developed a highly sensitive and portable digital handgrip, promoting independent and repetitive rehabilitation of grasp function based around a novel elastic force and position sensing structure. A usability study was performed on 66 healthy subjects to assess the effect of elastic versus rigid handgrip control during various visuomotor tracking tasks. The results indicate that, for tasks relying either on feedforward or on feedback control, novice users perform significantly better with the elastic handgrip, compared with the rigid equivalent (11% relative improvement, 9-14% mean range; p < 0.01). Furthermore, there was a threefold increase in the number of subjects who preferred elastic compared with rigid handgrip interaction. Our results suggest that device compliance is an important design consideration for grip training devices.

  13. Dynamic balancing of dual-rotor system with very little rotating speed difference

    Institute of Scientific and Technical Information of China (English)

    杨健; 贺世正; 王乐勤

    2003-01-01

    Unbalanced vibration in dual-rotor rotating machinery was studied with numerical simulations and experiments. A new method is proposed to separate vibration signals of inner and outer rotors for a system with very little difference in rotating speeds. Magnitudes and phase values of unbalance defects can be obtained directly by sampling the vibration signal synchronized with reference signal. The balancing process is completed by the reciprocity influence coefficients of inner and outer rotors method. Results showed the advantage of such method for a dual-rotor system as compared with conventional balancing.

  14. Less efficient elementary visuomotor processes in 7- to 10-year-old preterm-born children without cerebral palsy : An indication of impaired dorsal stream processes

    NARCIS (Netherlands)

    Van Braeckel, K.N.J.A.; Butcher, P.R.; Geuze, R.H.; van Duijn, M.A.J.; Bos, Arie; Bouma, A

    2008-01-01

    Follow-up studies of preterm children without serious neurological complications have consistently found deficits in visuomotor skills. To determine whether these deficits may be related to impaired elementary visuomotor processes, we investigated movement programming and execution of simple pointin

  15. Detecting Molecular Rotational Dynamics Complementing the Low-Frequency Terahertz Vibrations in a Zirconium-Based Metal-Organic Framework

    Science.gov (United States)

    Ryder, Matthew R.; Van de Voorde, Ben; Civalleri, Bartolomeo; Bennett, Thomas D.; Mukhopadhyay, Sanghamitra; Cinque, Gianfelice; Fernandez-Alonso, Felix; De Vos, Dirk; Rudić, Svemir; Tan, Jin-Chong

    2017-06-01

    We show clear experimental evidence of cooperative terahertz (THz) dynamics observed below 3 THz (˜100 cm-1 ), for a low-symmetry Zr-based metal-organic framework structure, termed MIL-140A [ZrO (O2C-C 6H4-CO2) ]. Utilizing a combination of high-resolution inelastic neutron scattering and synchrotron radiation far-infrared spectroscopy, we measured low-energy vibrations originating from the hindered rotations of organic linkers, whose energy barriers and detailed dynamics have been elucidated via ab initio density functional theory calculations. The complex pore architecture caused by the THz rotations has been characterized. We discovered an array of soft modes with trampolinelike motions, which could potentially be the source of anomalous mechanical phenomena such as negative thermal expansion. Our results demonstrate coordinated shear dynamics (2.47 THz), a mechanism which we have shown to destabilize the framework structure, in the exact crystallographic direction of the minimum shear modulus (Gmin ).

  16. When Action Observation Facilitates Visual Perception: Activation in Visuo-Motor Areas Contributes to Object Recognition.

    Science.gov (United States)

    Sim, Eun-Jin; Helbig, Hannah B; Graf, Markus; Kiefer, Markus

    2015-09-01

    Recent evidence suggests an interaction between the ventral visual-perceptual and dorsal visuo-motor brain systems during the course of object recognition. However, the precise function of the dorsal stream for perception remains to be determined. The present study specified the functional contribution of the visuo-motor system to visual object recognition using functional magnetic resonance imaging and event-related potential (ERP) during action priming. Primes were movies showing hands performing an action with an object with the object being erased, followed by a manipulable target object, which either afforded a similar or a dissimilar action (congruent vs. incongruent condition). Participants had to recognize the target object within a picture-word matching task. Priming-related reductions of brain activity were found in frontal and parietal visuo-motor areas as well as in ventral regions including inferior and anterior temporal areas. Effective connectivity analyses suggested functional influences of parietal areas on anterior temporal areas. ERPs revealed priming-related source activity in visuo-motor regions at about 120 ms and later activity in the ventral stream at about 380 ms. Hence, rapidly initiated visuo-motor processes within the dorsal stream functionally contribute to visual object recognition in interaction with ventral stream processes dedicated to visual analysis and semantic integration.

  17. Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

    DEFF Research Database (Denmark)

    Davies, G. R.; Chaplin, W. J.; Farr, W. M.;

    2014-01-01

    The solar analogs 16 Cyg A and 16 Cyg B are excellent asteroseismic targets in the \\Kepler field of view and together with a red dwarf and a Jovian planet form an interesting system. For these more evolved Sun-like stars we cannot detect surface rotation with the current \\Kepler data but instead ...

  18. Asteroseismic inference on rotation, gyrochronology and planetary system dynamics of 16 Cygni

    CERN Document Server

    Davies, G R; Farr, W M; a, R A Garc\\'ı; Lund, M N; Mathis, S; Metcalfe, T S; Appourchaux, T; Basu, S; Benomar, O; Campante, T L; Ceillier, T; Elsworth, Y; Handberg, R; Salabert, D; Stello, D

    2014-01-01

    The solar analogs 16 Cyg A and 16 Cyg B are excellent asteroseismic targets in the \\Kepler field of view and together with a red dwarf and a Jovian planet form an interesting system. For these more evolved Sun-like stars we cannot detect surface rotation with the current \\Kepler data but instead use the technique of asteroseimology to determine rotational properties of both 16 Cyg A and B. We find the rotation periods to be $23.8^{+1.5}_{-1.8} \\rm \\, days$ and $23.2^{+11.5}_{-3.2} \\rm \\, days$, and the angles of inclination to be $56^{+6}_{-5} \\, ^{\\circ}$ and $36^{+17}_{-7} \\, ^{\\circ}$, for A and B respectively. Together with these results we use the published mass and age to suggest that, under the assumption of a solar-like rotation profile, 16 Cyg A could be used when calibrating gyrochronology relations. In addition, we discuss the known 16 Cyg B star-planet eccentricity and measured low obliquity which is consistent with Kozai cycling and tidal theory.

  19. Angular momentum dynamics and the intrinsic drift of monopolar vortices on a rotating sphere

    NARCIS (Netherlands)

    Van der Toorn, R.; Zimmerman, J.T.F.

    2010-01-01

    On the basis of the angular momentum equation for a fluid shell on a rotating planet, we analyze the intrinsic drift of a monopolar vortex in the shell. Central is the development of a general angular momentum equation for Eulerian fluid mechanics based on coordinate-free, general tensorial

  20. Angular momentum dynamics and the intrinsic drift of monopolar vortices on a rotating sphere

    NARCIS (Netherlands)

    Van der Toorn, R.; Zimmerman, J.T.F.

    2010-01-01

    On the basis of the angular momentum equation for a fluid shell on a rotating planet, we analyze the intrinsic drift of a monopolar vortex in the shell. Central is the development of a general angular momentum equation for Eulerian fluid mechanics based on coordinate-free, general tensorial represen

  1. Dynamics of piezoceramics-based mass and force actuators for rotating machines

    NARCIS (Netherlands)

    Sloetjes, Peter; Boer, de André; Hoogt, van der Peter

    2007-01-01

    In the past decade, it has become more and more common to install active vibration control devices on rotating systems like grinding machines, tooling centers, industrial fans and drive shafts. In the present research, two innovative actuation concepts for such devices are evaluated. The first devic

  2. Benchmarking in a rotating annulus: a comparative experimental and numerical study of baroclinic wave dynamics

    Directory of Open Access Journals (Sweden)

    Miklos Vincze

    2015-01-01

    Full Text Available The differentially heated rotating annulus is a widely studied tabletop-size laboratory model of the general mid-latitude atmospheric circulation. The two most relevant factors of cyclogenesis, namely rotation and meridional temperature gradient are quite well captured in this simple arrangement. The radial temperature difference in the cylindrical tank and its rotation rate can be set so that the isothermal surfaces in the bulk tilt, leading to the formation of baroclinic waves. The signatures of these waves at the free water surface have been analyzed via infrared thermography in a wide range of rotation rates (keeping the radial temperature difference constant and under different initial conditions. In parallel to the laboratory experiments, five groups of the MetStröm collaboration have conducted numerical simulations in the same parameter regime using different approaches and solvers, and applying different initial conditions and perturbations. The experimentally and numerically obtained baroclinic wave patterns have been evaluated and compared in terms of their dominant wave modes, spatio-temporal variance properties and drift rates. Thus certain “benchmarks” have been created that can later be used as test cases for atmospheric numerical model validation.

  3. Delta-singular vortex dynamics on a rotating sphere and stability of coupled atmospheric centers of action

    CERN Document Server

    Mokhov, I I; Chefranov, A G

    2010-01-01

    Existence of a stationary mode for a Hamiltonian dynamic system of two point vortexes with different signs on different latitudes of a uniform rotating sphere complying with observed data is stated. It is shown that such mode realization is possible only in the case when the more intensive cyclonic vortex has greater latitude than that of the anticyclonic vortex. A criterion of exponential instability of the stationary vortex mode taken into account impact of the polar vortexes is obtained. Compliance of the theory to observed data and reanalysis for coupled quasi-stationary systems of cyclonic and anticyclonic atmosphere action centers above oceans in the Northern Hemisphere is considered.

  4. Dynamics of rotating and vibrating thin hemispherical shell with mass and damping imperfections and parametrically driven by discrete electrodes

    CSIR Research Space (South Africa)

    Shatalov, M

    2009-05-01

    Full Text Available stream_source_info Shatalov2_2009.pdf.txt stream_content_type text/plain stream_size 22572 Content-Encoding UTF-8 stream_name Shatalov2_2009.pdf.txt Content-Type text/plain; charset=UTF-8 1 DYNAMICS OF ROTATING... AND VIBRATING THIN HEMISPHERICAL SHELL WITH MASS AND DAMPING IMPERFECTIONS AND PARAMETRICALLY DRIVEN BY DISCRETE ELECTRODES Michael Shatalov1,2 and Charlotta Coetzee2 1Sensor Science and Technology (SST) of CSIR Material Science and Manufacturing (MSM...

  5. Interaction between global-scale atmospheric vortices: Modeling with Hamiltonian dynamic system of antipodal point vortices on a rotating sphere

    CERN Document Server

    Mokhov, Igor I; Chefranov, A G

    2016-01-01

    We get point vortices dynamics equations on a rotating sphere surface directly from the hydrodynamic equations as representing their weak exact solution contrary to the conventional case of the use of a kinematic relationship between a given singular vortex field and velocity field. It is first time that the effect of a sphere rotation on the vortices interaction is accounted for in exact form. We show that only the stream function of a vortex pair of antipodal vortices (APV), and only it satisfies the original three-dimensional hydrodynamics equations on a sphere. We prove that only APV pair with two point vortices in the diameter-conjugated points of a sphere with equal by quantity but different sign circulations may be correctly considered as an elementary (stationary, not self-affecting) singular point object on a sphere. We suggest using the axis connecting the two point vortices in an APV for describing of an axis of rotation of the global vortices introduced in (Barrett, 1958) to reflect the observed g...

  6. Visuomotor perception in children with attention deficit hyperactivity disorder--combined type.

    Science.gov (United States)

    Raggio, D J

    1999-04-01

    Children with Attention Deficit Hyperactivity Disorder--Combined Type (ADHD-CT) defined by behavioral characteristics of inattention, impulsivity, and hyperactivity including weaknesses in fine motor coordination and poor motor inhibition frequently exhibit poor handwriting and penmanship. Performance of children on visuomotor tasks is further complicated, as most studies have not excluded children with specific learning disabilities who are known to do poorly on these tests. This study was designed to examine the performance of children diagnosed with this disorder, without learning disabilities on visuomotor tasks. 26 preadolescent patients were administered a battery of tests that included the Bender-Gestalt, Conners' Parent Rating Scale, Continuous Performance Task, and Wide Range Achievement Test-Third Edition Scores on the Bender-Gestalt test averaged significantly lower than Koppitz normative data. This study lends support to the hypothesis that ADHD-CT children without learning disabilities exhibit deficits on tasks requiring visuomotor perception.

  7. An `Analytic Dynamical Magnetosphere' formalism for X-ray and optical emission from slowly rotating magnetic massive stars

    CERN Document Server

    Owocki, Stanley P; Sundqvist, Jon O; Petit, Veronique; Cohen, David H; Townsend, Richard H D

    2016-01-01

    Slowly rotating magnetic massive stars develop "dynamical magnetospheres" (DM's), characterized by trapping of stellar wind outflow in closed magnetic loops, shock heating from collision of the upflow from opposite loop footpoints, and subsequent gravitational infall of radiatively cooled material. In 2D and 3D magnetohydrodynamic (MHD) simulations the interplay among these three components is spatially complex and temporally variable, making it difficult to derive observational signatures and discern their overall scaling trends.Within a simplified, steady-state analysis based on overall conservation principles, we present here an "analytic dynamical magnetosphere" (ADM) model that provides explicit formulae for density, temperature and flow speed in each of these three components -- wind outflow, hot post-shock gas, and cooled inflow -- as a function of colatitude and radius within the closed (presumed dipole) field lines of the magnetosphere. We compare these scalings with time-averaged results from MHD si...

  8. Counter-rotating stellar discs around a massive black hole: self-consistent, time-dependent dynamics

    CERN Document Server

    Touma, Jihad R

    2011-01-01

    We formulate the collisionless Boltzmann equation (CBE) for dense star clusters that lie within the radius of influence of a massive black hole in galactic nuclei. Our approach to these nearly Keplerian systems follows that of Sridhar and Touma (1999): Delaunay canonical variables are used to describe stellar orbits and we average over the fast Keplerian orbital phases. The stellar distribution function (DF) evolves on the longer time scale of precessional motions, whose dynamics is governed by a Hamiltonian, given by the orbit-averaged self-gravitational potential of the cluster. We specialize to razor-thin, planar discs and consider two counter-rotating ("$\\pm$") populations of stars. To describe discs of small eccentricities, we expand the $\\pm$ Hamiltonian to fourth order in the eccentricities, with coefficients that depend self-consistently on the $\\pm$ DFs. We construct approximate $\\pm$ dynamical invariants and use Jeans' theorem to construct time-dependent $\\pm$ DFs, which are completely described by ...

  9. Extended pump-probe Faraday rotation spectroscopy of the submicrosecond electron spin dynamics in n -type GaAs

    Science.gov (United States)

    Belykh, V. V.; Evers, E.; Yakovlev, D. R.; Fobbe, F.; Greilich, A.; Bayer, M.

    2016-12-01

    We develop an extended pump-probe Faraday rotation technique to study submicrosecond electron spin dynamics with picosecond time resolution in a wide range of magnetic fields. The electron spin dephasing time T2* and the longitudinal spin relaxation time T1, both approaching 250 ns in weak fields, are measured thereby in n -type bulk GaAs. By tailoring the pump pulse train through increasing the contained number of pulses, the buildup of resonant spin amplification is demonstrated for the electron spin polarization. The spin precession amplitude in high magnetic fields applied in the Voigt geometry shows a nonmonotonic dynamics deviating strongly from a monoexponential decay and revealing slow beatings. The beatings indicate a two spin component behavior with a g -factor difference of Δ g ˜4 ×10-4 , much smaller than the Δ g expected for free and donor-bound electrons. This g -factor variation indicates efficient, but incomplete spin exchange averaging.

  10. Influence of a second satellite on the rotational dynamics of an oblate moon

    Science.gov (United States)

    Tarnopolski, Mariusz

    2017-02-01

    The gravitational influence of a second satellite on the rotation of an oblate moon is numerically examined. A simplified model, assuming the axis of rotation perpendicular to the (Keplerian) orbit plane, is derived. The differences between the two models, i.e. in the absence and presence of the second satellite, are investigated via bifurcation diagrams and by evolving compact sets of initial conditions in the phase space. It turns out that the presence of another satellite causes some trajectories, that were regular in its absence, to become chaotic. Moreover, the highly structured picture revealed by the bifurcation diagrams in dependence on the eccentricity of the oblate body's orbit is destroyed when the gravitational influence is included, and the periodicities and critical curves are destroyed as well. For demonstrative purposes, focus is laid on parameters of the Saturn-Titan-Hyperion system, and on oblate satellites on low-eccentric orbits, i.e. e≈ 0.005.

  11. Ocean Circulation in a Rotating Tank - An Outreach Project in Fluid Dynamics

    Science.gov (United States)

    Reckinger, Shanon

    2013-11-01

    A rotating water tank was designed and built by two senior mechanical engineering undergraduates at Fairfield University. The project was part of a year long senior design course. The rotating water tank is used to simulate oceanic and atmospheric phenomenon for classroom or outreach use. The following year, the tank was used for outreach as part of Fairfield University's Broadening Access to Science Education (BASE) camp. BASE camp is a two week residential camp for high school woman interested in scientific research. It is designed to inform and excite students by giving them a hands-on, research-based experience in the sciences, engineering, and mathematics. An all female research team composed of one mechanical engineering faculty member, two engineering undergraduates, and three high school students used the tank to explore ``how the ocean moves.'' This talk will explain the design project and the outreach project in detail, in hopes of inspiring new fluids education and outreach ideas.

  12. Influence of a second satellite on the rotational dynamics of an oblate moon

    CERN Document Server

    Tarnopolski, Mariusz

    2016-01-01

    The gravitational influence of a second satellite on the rotation of an oblate moon is numerically examined. A simplified model, assuming the axis of rotation perpendicular to the (Keplerian) orbit plane, is derived. The differences between the two models, i.e. in the absence and presence of the second satellite, are investigated via bifurcation diagrams and by evolving compact sets of initial conditions in the phase space. It turns out that the presence of another satellite causes some trajectories, that were regular in its absence, to become chaotic. Moreover, the highly structured picture revealed by the bifurcation diagrams in dependence on the eccentricity of the oblate body's orbit is destroyed when the gravitational influence is included, and the periodicities and critical curves are destroyed as well. For demonstrative purposes, focus is laid on parameters of the Saturn-Titan-Hyperion system, and on oblate satellites on low-eccentric orbits, i.e. $e\\approx 0.005$.

  13. Earle K. Plyler Prize for Molecular Spectroscopy & Dynamics Lecture: Broadband Rotational Spectroscopy for Chemical Kinetics, Molecular Structure, and Analytical Chemistry

    Science.gov (United States)

    Pate, Brooks

    2013-03-01

    Advances in high-speed digital electronics have enabled a new generation of molecular rotational spectroscopy techniques that provide instantaneous broadband spectral coverage. These techniques use a chirped excitation pulse to coherently excite the molecular sample over a spectral bandwidth of 10 GHz or larger through rapid passage. The subsequent time-domain emission is recorded using high-speed digitizers (up to 100 Gigasample/s) and the frequency domain spectrum is produced by fast Fourier transformation. The chirped-pulse Fourier transform (CP-FT) method has been implemented in the microwave frequency range (2-40 GHz) for studies of cold samples in pulsed jet sources and in the mm-wave/terahertz (THz) frequency range for studies of samples at room-temperature. The method has opened new applications for molecular rotational spectroscopy in the area of chemical kinetics where dynamic rotational spectroscopy is used to measure the rates of unimolecular isomerization reactions in highly excited molecules prepared by pulsed infrared laser excitation. In these applications, the isomerization rate is obtained from an analysis of the overall line shapes which are modified by chemical exchange leading to coalescence behavior similar to the effect in NMR spectroscopy. The sensitivity of the method and the ability to extend it to low frequency (2-8 GHz) have significantly increased the size range of molecules and molecular clusters for structure determination using isotopic substitution to build up the 3D molecular structures atom-by-atom. Application to the structure of water clusters with up to 15 water molecules will be presented. When coupled with advances in solid-state mm-wave/THz devices, this method provides a direct digital technique for analytical chemistry of room-temperature gases based on molecular rotational spectroscopy. These high-throughput methods can analyze complex sample mixtures with unmatched chemical selectivity and short analysis times. Work

  14. Eye rotation induced dynamics of a Newtonian fluid within the vitreous cavity: the effect of the chamber shape

    Energy Technology Data Exchange (ETDEWEB)

    Stocchino, Alessandro [Department of Environmental Engineering, University of Genoa (Italy); Repetto, Rodolfo [Department of Engineering of Structures, Water and Soil, University of L' Aquila (Italy); Cafferata, Chiara [Department of Environmental Engineering, University of Genoa (Italy)

    2007-04-07

    The dynamics of the vitreous body induced by eye rotations is studied experimentally. In particular, we consider the case in which the vitreous cavity is filled by a Newtonian fluid, either because the vitreous is liquefied or because it has been replaced, after vitrectomy, by a viscous fluid. We employ a rigid Perspex container which models, in a magnified scale, the vitreous cavity of the human eye. The shape of the cavity closely resembles that of the real vitreous chamber; in particular, the anterior part of the container is concave in order to model the presence of the eye lens. The container is filled with glycerol and is mounted on the shaft of a computer-controlled motor which rotates according to a periodic time law. PIV (particle image velocimetry) measurements are taken on the equatorial plane orthogonal to the axis of rotation. The experimental measurements show that the velocity field is strongly influenced by the deformed geometry of the domain. In particular, the formation of a vortex in the vicinity of the lens, which migrates in time towards the core of the domain, is invariably observed. The vortex path is tracked in time by means of a vortex identification technique and it is found that it is significantly influenced by the Womersley number of the flow. Particle trajectories are computed from the PIV measurements. Particles initially located at different positions on the equatorial horizontal plane (perpendicular to the axis of rotation) tend to concentrate in narrow regions adjacent to the lens, thus suggesting the existence, in such regions, of a vertical fluid ejection. Such a strong flow three-dimensionality, which is essentially induced by the irregular shape of the domain, may play a significant role in the mixing processes taking place inside the eye globe. The tangential stresses acting on the rigid boundary of the domain are also computed from the experimental measurements showing that regions subject to particularly intense stresses

  15. Rotation of mercury: theoretical analysis of the dynamics of a rigid ellipsoidal planet.

    Science.gov (United States)

    Laslett, L J; Sessler, A M

    1966-03-18

    The second-order nonlinear differential equation for the rotation of Mercury implies locked-in motion when the period is within the range where e is the eccentricity and T is the period of Mercury's orbit, the time t is measured from perihelion, and lambda is a measure of the planet's disiortion. For values near 2T/3, the instantaneous period oscillates about 2T/3 with period (21lambdae/2)T.

  16. Local measurement of error field using naturally rotating tearing mode dynamics in EXTRAP T2R

    Science.gov (United States)

    Sweeney, R. M.; Frassinetti, L.; Brunsell, P.; Fridström, R.; Volpe, F. A.

    2016-12-01

    An error field (EF) detection technique using the amplitude modulation of a naturally rotating tearing mode (TM) is developed and validated in the EXTRAP T2R reversed field pinch. The technique was used to identify intrinsic EFs of m/n  =  1/-12, where m and n are the poloidal and toroidal mode numbers. The effect of the EF and of a resonant magnetic perturbation (RMP) on the TM, in particular on amplitude modulation, is modeled with a first-order solution of the modified Rutherford equation. In the experiment, the TM amplitude is measured as a function of the toroidal angle as the TM rotates rapidly in the presence of an unknown EF and a known, deliberately applied RMP. The RMP amplitude is fixed while the toroidal phase is varied from one discharge to the other, completing a full toroidal scan. Using three such scans with different RMP amplitudes, the EF amplitude and phase are inferred from the phases at which the TM amplitude maximizes. The estimated EF amplitude is consistent with other estimates (e.g. based on the best EF-cancelling RMP, resulting in the fastest TM rotation). A passive variant of this technique is also presented, where no RMPs are applied, and the EF phase is deduced.

  17. Cold gas dynamics in Hydra-A: evidence for a rotating disk

    CERN Document Server

    Hamer, S L; Swinbank, A M; Oonk, J B R; Mittal, R; McNamara, B R; Russell, H R; Bremer, M N; Combes, F; Fabian, A C; Nesvadba, N P H; O'Dea, C P; Baum, S A; Salomé, P; Tremblay, G; Donahue, M; Ferland, G J; Sarazin, C L

    2013-01-01

    We present multi-frequency observations of the radio galaxy Hydra-A (3C218) located in the core of a massive, X-ray luminous galaxy cluster. IFU spectroscopy is used to trace the kinematics of the ionised and warm molecular hydrogen which are consistent with a ~ 5 kpc rotating disc. Broad, double-peaked lines of CO(2-1), [CII]157 $\\mu$m and [OI]63 $\\mu$m are detected. We estimate the mass of the cold gas within the disc to be M$_{gas}$ = 2.3 $\\pm$ 0.3 x 10$^9$ M$_{\\odot}$. These observations demonstrate that the complex line profiles found in the cold atomic and molecular gas are related to the rotating disc or ring of gas. Finally, an HST image of the galaxy shows that this gas disc contains a substantial mass of dust. The large gas mass, SFR and kinematics are consistent with the levels of gas cooling from the ICM. We conclude that the cold gas originates from the continual quiescent accumulation of cooled ICM gas. The rotation is in a plane perpendicular to the projected orientation of the radio jets and I...

  18. Quantifying online visuomotor feedback utilization in the frequency domain.

    Science.gov (United States)

    de Grosbois, John; Tremblay, Luc

    2016-12-01

    The utilization of sensory information during activities of daily living is ubiquitous both prior to and during movements (i.e., related to planning and online control, respectively). Because of the overlapping nature of online corrective processes, the quantification of feedback utilization has proven difficult. In the present study, we primarily sought to evaluate the utility of a novel analysis in the frequency domain for identifying visuomotor feedback utilization (i.e., online control). A second goal was to compare the sensitivity of the frequency analysis to that of currently utilized measures of online control. Participants completed reaching movements to targets located 27, 30, and 33 cm from a start position. During these reaches, vision of the environment was either provided or withheld. Performance was assessed across contemporary measures of online control. For the novel frequency analysis presented in this study, the acceleration profiles of reaching movements were detrended with a 5th-order polynomial fit, and the proportional power spectra were computed from the residuals of these fits. The results indicated that the use of visual feedback during reaching movements increased the contribution of the 4.68-Hz frequency to the residuals of the acceleration profiles. Comparisons across all measures of online control showed that the most sensitive measure was the squared Fisher transform of the correlation between the positions at 75 % and 100 % of the movement time. However, because such correlational measures can be contaminated by offline control processes, the frequency-domain analysis proposed herein represents a viable and promising alternative to detect changes in online feedback utilization.

  19. A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation

    Science.gov (United States)

    Zhu, Ling; van de Ven, Glenn; Watkins, Laura L.; Posti, Lorenzo

    2016-11-01

    We present a new discrete chemo-dynamical axisymmetric modelling technique, which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement over previous Jeans models is that realistic chemical distributions are included directly in the dynamical modelling of the discrete data. This avoids loss of information due to spatial binning and eliminates the need for hard cuts to remove contaminants and to separate stars based on their chemical properties. Using a combined likelihood in position, metallicity and kinematics, we find that our models naturally separate Sculptor stars into a metal-rich and a metal-poor population. Allowing for non-spherical symmetry, our approach provides a central slope of the dark matter density of γ = 0.5 ± 0.3. The metal-rich population is nearly isotropic (with β _r^{red} = 0.0± 0.1), while the metal-poor population is tangentially anisotropic (with β _r^{blue} = -0.2± 0.1) around the half-light radius of 0.26 kpc. A weak internal rotation of the metal-rich population is revealed with vmax/σ0 = 0.15 ± 0.15. We run tests using mock data to show that a discrete data set with ˜6000 stars is required to distinguish between a core (γ = 0) and cusp (γ = 1), and to constrain the possible internal rotation to better than 1σ confidence with our model. We conclude that our discrete chemo-dynamical modelling technique provides a flexible and powerful tool to robustly constrain the internal dynamics of multiple populations, and the total mass distribution in a stellar system.

  20. Mapping shape to visuomotor mapping: learning and generalisation of sensorimotor behaviour based on contextual information.

    Directory of Open Access Journals (Sweden)

    Loes C J van Dam

    2015-03-01

    Full Text Available Humans can learn and store multiple visuomotor mappings (dual-adaptation when feedback for each is provided alternately. Moreover, learned context cues associated with each mapping can be used to switch between the stored mappings. However, little is known about the associative learning between cue and required visuomotor mapping, and how learning generalises to novel but similar conditions. To investigate these questions, participants performed a rapid target-pointing task while we manipulated the offset between visual feedback and movement end-points. The visual feedback was presented with horizontal offsets of different amounts, dependent on the targets shape. Participants thus needed to use different visuomotor mappings between target location and required motor response depending on the target shape in order to "hit" it. The target shapes were taken from a continuous set of shapes, morphed between spiky and circular shapes. After training we tested participants performance, without feedback, on different target shapes that had not been learned previously. We compared two hypotheses. First, we hypothesised that participants could (explicitly extract the linear relationship between target shape and visuomotor mapping and generalise accordingly. Second, using previous findings of visuomotor learning, we developed a (implicit Bayesian learning model that predicts generalisation that is more consistent with categorisation (i.e. use one mapping or the other. The experimental results show that, although learning the associations requires explicit awareness of the cues' role, participants apply the mapping corresponding to the trained shape that is most similar to the current one, consistent with the Bayesian learning model. Furthermore, the Bayesian learning model predicts that learning should slow down with increased numbers of training pairs, which was confirmed by the present results. In short, we found a good correspondence between the

  1. On a role of corotation radius in the low $T/W$ dynamical instability of differentially rotating stars

    CERN Document Server

    Yoshida, Shin'ichirou

    2016-01-01

    We investigate the nature of so-called low $T/W$ dynamical instability in a differentially rotating star by focusing on the role played by the corotation radius of the unstable oscillation modes. An one dimensional model of linear perturbation, which neglects dependence of variables on the coordinate along the rotational axis of the star, is solved to obtain stable and unstable eigenmodes. A linear eigenmode having a corotation radius, at which azimuthal pattern speed of the mode coincides with the stellar angular velocity, is categorized to either a complex (growing or damping) mode or a purely real mode belonging to a continuous spectrum of frequency. We compute canonical angular momentum and its flux to study eigenmodes with corotation radius. In a dynamically unstable mode, sound wave transports its angular momentum in such a way that the absolute value of the angular momentum is increased on both sides of the corotation radius. We further evaluate growth of amplitude of reflected sound wave incident to a...

  2. [Dynamics of polycyclic aromatic hydrocarbons (PAHs) in the paddy-soil system during the crop rotation process].

    Science.gov (United States)

    Jiao, Xing-chun; Ye, Chuan-yong; Chen, Su-hua; Yang, Yong-liang; Wu, Zhen-yan

    2010-07-01

    The concentrations of polycyclic aromatic hydrocarbons (PAHs) in the paddy root-soil system were determined to study the dynamic and the influencing factors during crop rotation period. It showed that the dynamic of PAHs in paddy roots was most correlative with the factor of root surface area, but less correlated with PAHs in air and particles, which indicates that the physiological characters rather than the environment media are the main factors influencing the PAHs accumulation in paddy roots. According to the EPA risk standard about BaP and sigma PAHs, the PAHs accumulation in the paddy seeds won't decrease the food security to human being. The PAHs concentrations in paddy soil showed a declined trend during the period of paddy growth, which was affected not only by the processes of water elution and microbe degradation, but also depended on the absorption rate of paddy roots. When the crop rotation begins and paddy planting rolls into the next growing period, the PAHs in the paddy soil will again increase into a higher level which is correlated with the TOC content in the soil.

  3. Determination of Scaling Parameter and Dynamical Resonances in Complex-Rotated Hamiltonian Ⅱ: Numerical Analysis

    Institute of Scientific and Technical Information of China (English)

    LIU Zong-Liang; ZHAO Fang; LI Shao-Hua; ZHAO Mei-Shan; CHEN Chang-Yong

    2008-01-01

    This paper is concerned with the determination of a unique scaling parameter in complex scaling analysis and with accurate calculation of dynamics resonances. In the preceding paper we have presented a theoretical analysis and provided a formalism for dynamical resonance calculations. In this paper we present accurate numerical results for two non-trivial dynamical processes, namely, models of diatomie molecular predissoeiation and of barrier potential scattering for resonances. The results presented in this paper confirm our theoretical analysis, remove a theoretical ambiguity on determination of the complex scaling parameter, and provide an improved understanding for dynamical resonance calculations in rigged Hilbert space.

  4. Steering Dynamic Performance of an Electric Transmission Tracked Vehicle Based on Rotating Speed Control

    Institute of Scientific and Technical Information of China (English)

    SUN Feng-chun; CHEN Shu-yong; ZHANG Cheng-ning

    2006-01-01

    In order to analyze steering dynamic performance of an electric transmission tracked vehicle exactly, modern design theory and methodology-collaborative simulation and virtual prototype are applied. The 3-D multi-body dynamic model of full vehicle running gears and control system model are built based on the simulation platform on dynamic analysis software known as RecurDyn/Track-HM and control system analysis software known as Matlab/Simulink. Theory analysis and collaborative simulation of turning kinematic/dynamic performance in different velocity and turning radius are made. Comparing the test result with theory computation validates the correctness of the model. The method has instructional significance of solving the existent modeling problem, comprehension of turning performance and test debugging strategy,and also forms a new idea of research on dynamic characteristics for the electric transmission tracked vehicle's electric propulsion system.

  5. Determination of Scaling Parameter and Dynamical Resonances in Complex-Rotated Hamiltonian Ⅰ: Theory

    Institute of Scientific and Technical Information of China (English)

    LI Heng-Mei; ZHAO Fang; YUAN Hong-Chun; ZHAO Mei-Shan

    2008-01-01

    In this paper we present a theoretical analysis on the determination of the scaling parameter in the complex-rotated Hamiltonian, which has served as a basis for successful applications of the rigged Hilbert space theory for resonances. Based on the complex energy eigenvalue, E(θ) = En(θ) - iF(θ)/2, as a function of the scaling parameter The condition dER(θR)/ dθ = 0 is merely a consequence of the Virial theorem and θⅠ = θR is not a necessary condition for a resonance state. We also provide a harmonic approximation formalism for resonances in scattering over a potential barrier.

  6. Dynamics of test particles in the five-dimensional, charged, rotating EMCS spacetime

    CERN Document Server

    Reimers, Stephan

    2016-01-01

    We derive the complete set of geodesic equations for massive and massless test particles of a five-dimensional, charged, rotating black hole solution of the Einstein-Maxwell-Chern-Simons field equations in five-dimensional minimal gauged supergravity and present their analytical solutions in terms of Weierstra{\\ss}' elliptic functions. We study the polar and radial motion, depending on the black hole and test particle parameters, and characterize the test particle motion qualitatively by the means of effective potentials. We use the analytical solutions in order to visualize the test particle motion by two- and three-dimensional plots.

  7. Speckle dynamics for dual-beam optical illumination of a rotating structure

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Yura, Harold; Hanson, Steen Grüner

    2009-01-01

    An out-of-plane rotating object is illuminated with two spatially separated coherent beams, giving rise to fully developed speckles, which will translate and gradually decorrelate in the observation plane, located in the far field. The speckle pattern is a compound structure, consisting of random...... Fourier transform system. It is shown that the compound speckle structures move as two individual structures with the same decorrelation length. The velocity of the random speckles is a combination of angular and peripheral velocity, where the peripheral velocity is inversely proportional to the radius...

  8. Effects of rotating frame turbulence and dynamic stall on gust response of helicopter blades

    Science.gov (United States)

    Madhavan, R.; Gaonkar, G. H.

    1989-01-01

    The instantaneous or frequency-time spectrum of rotating frame turbulence (RFT) is presented. This spectrum makes it possible to predict the transfer of energy with respect to frequencies and the periodically varying nonstationarity with respect to time. Attention is also given to the RFT effects on the response statistics of an isolated rotor blade for low-advance-ratio and low-altitude conditions. It is noted that spectral density, rms values, and threshold-crossing expectation rates are significantly influenced by RFT.

  9. Dynamic Formulations and Beating Phenomena of Rotating Euler—Bernoulli Flexible Shafts

    Institute of Scientific and Technical Information of China (English)

    朱怀亮

    2002-01-01

    In this paper,the intrinsic behavior of rotating Euler-Benoulli flexible shafts was studied due to coupled bending and torsional vibratuions,the equations of motion of the shaft with unbalanced eccentricity and visous material damping were derived by the Hamilton principle.The numerical solution was obtained using the perturbation approach and mode-assuming method.The influences of the coupled vibrations between the benging and torsion.the rotaing speed,material damping and the slenderness ratio of the shaft were analyzed.It is clearly shown that the beating phenomena can occur when the interaction of torsion and flexure is considered.

  10. Local measurement of error field using naturally rotating tearing mode dynamics in EXTRAP T2R

    CERN Document Server

    Sweeney, R M; Brunsell, P; Fridström, R; Volpe, F A

    2016-01-01

    An error field (EF) detection technique using the amplitude modulation of a naturally rotating tearing mode (TM) is developed and validated in the EXTRAP T2R reversed field pinch. The technique was used to identify intrinsic EFs of $m/n = 1/-12$, where $m$ and $n$ are the poloidal and toroidal mode numbers. The effect of the EF and of a resonant magnetic perturbation (RMP) on the TM, in particular on amplitude modulation, is modeled with a first-order solution of the Modified Rutherford Equation. In the experiment, the TM amplitude is measured as a function of the toroidal angle as the TM rotates rapidly in the presence of an unknown EF and a known, deliberately applied RMP. The RMP amplitude is fixed while the toroidal phase is varied from one discharge to the other, completing a full toroidal scan. Using three such scans with different RMP amplitudes, the EF amplitude and phase are inferred from the phases at which the TM amplitude maximizes. The estimated EF amplitude is consistent with other estimates (e....

  11. Intersegmental dynamics of 3D upper arm and forearm longitudinal axis rotations during baseball pitching.

    Science.gov (United States)

    Naito, Kozo; Takagi, Hiroyasu; Yamada, Norimasa; Hashimoto, Shinichi; Maruyama, Takeo

    2014-12-01

    The shoulder internal rotation (IR) and forearm pronation (PR) are important elements for baseball pitching, however, how rapid rotations of IR and PR are produced by muscular torques and inter-segmental forces is not clear. The aim of this study is to clarify how IR and PR angular velocities are maximized, depending on muscular torque and interactive torque effects, and gain a detailed knowledge about inter-segmental interaction within a multi-joint linked chain. The throwing movements of eight collegiate baseball pitchers were recorded by a motion capture system, and induced-acceleration analysis was used to assess the respective contributions of the muscular (MUS) and interactive torques associated with gyroscopic moment (GYR), and Coriolis (COR) and centrifugal forces (CEN) to maximum angular velocities of IR (MIRV) and PR (MPRV). The results showed that the contribution of MUS account for 98.0% of MIRV, while that contribution to MPRV was indicated as negative (-48.1%). It was shown that MPRV depends primarily on the interactive torques associated with GYR and CEN, but the effects of GYR, COR and CEN on MIRV are negligible. In conclusion, rapid PR motion during pitching is created by passive-effect, and is likely a natural movement which arises from 3D throwing movement. Applying the current analysis to IR and PR motions is helpful in providing the implications for improving performance and considering conditioning methods for pitchers.

  12. Time-dependent rotational stability of dynamic planets with viscoelastic lithospheres

    Science.gov (United States)

    Moore, K. M.; Chan, N.-H.; Daradich, A.; Mitrovica, J. X.

    2017-06-01

    We extend previous work to derive a non-linear rotational stability theory governing true polar wander (TPW) of terrestrial planets with viscoelastic lithospheres. We demonstrate, analytically and using numerical examples, that our expressions are consistent with previous results in the limiting cases of low and infinite (i.e., purely elastic) viscosity lithospheres. To illustrate the stability theory, we compute TPW on Mars driven by a simple, prescribed mass loading. Our calculations demonstrate that on short time scales relative to the relaxation time of the viscoelastic lithosphere, the rotation axis follows a constrained path that reflects stabilization by remnant strength in the lithosphere, but that on long times scales this stabilization disappears and the load ultimately reaches the equator. Earlier work based on the assumption of a permanent remnant bulge in the case of a purely elastic lithosphere has suggested that Martian TPW would not persist for any significant time after a load is emplaced, and thus an equilibrium stability theory is sufficient to model long-term (order 1 Myr or longer) polar motion of the planet. Our results suggest, in contrast, that TPW on Mars can continue over time scales on the order of the relaxation time of the lithosphere after load emplacement; for sufficiently high lithospheric viscosities, this time scale may be comparable to the age of the planet.

  13. Indentification of a Rotator Phase of Octamethyl Ferrocene and Correlations Between its Structural and Dynamical Properties

    Energy Technology Data Exchange (ETDEWEB)

    Asthalter,T.; Sergueev, I.; Van Burck, U.; Dinnebier, R.

    2006-01-01

    The low- and high-temperature phases of octamethyl ferrocene were studied in detail, using high-resolution X-ray powder diffraction, differential scanning calorimetry and nuclear resonant scattering, in particular the novel technique of synchrotron radiation perturbed angular correlations (SRPAC). Much as in the case of an analogous but more unsymmetrical molecule, octamethyl ethinyl ferrocene, the high-temperature phase possesses the space group R{bar 3}m source with lattice parameters a = b = 12.5568(1) Angstroms, c = 9.6045(1) Angstroms, which in the rhombohedral setting correspond to a = 7.9251(1) Angstroms, {alpha}=104.79 degrees. An increase of the volume per formula unit of about 12% across the phase transition is observed. The rotation of the electric field gradient, which can be identified with the rotation of the entire molecule within the lattice, follows Arrhenius behavior with a high activation energy of (40.3 {+-} 3.3)kJ mol{sup -1}. Whereas precursor effects and a change in activation energy were observed for octamethyl ethinyl ferrocene, no such effects are observed for octamethyl ferrocene. We relate this difference to the absence of the ethinyl substituent in octamethyl ferrocene.

  14. Rotations with Rodrigues' Vector

    Science.gov (United States)

    Pina, E.

    2011-01-01

    The rotational dynamics was studied from the point of view of Rodrigues' vector. This vector is defined here by its connection with other forms of parametrization of the rotation matrix. The rotation matrix was expressed in terms of this vector. The angular velocity was computed using the components of Rodrigues' vector as coordinates. It appears…

  15. Changes in corticospinal drive to spinal motoneurones following visuo-motor skill learning in humans

    DEFF Research Database (Denmark)

    Perez, Monica A.; Jensen, Jesper Lundbye; Nielsen, Jens Bo

    2006-01-01

    We have previously demonstrated an increase in the excitability of the leg motor cortical area in relation to acquisition of a visuo-motor task in healthy humans. It remains unknown whether the interaction between corticospinal drive and spinal motoneurones is also modulated following motor skill...

  16. Role of human premotor dorsal region in learning a conditional visuomotor task.

    Science.gov (United States)

    Parikh, Pranav J; Santello, Marco

    2017-01-01

    Conditional learning is an important component of our everyday activities (e.g., handling a phone or sorting work files) and requires identification of the arbitrary stimulus, accurate selection of the motor response, monitoring of the response, and storing in memory of the stimulus-response association for future recall. Learning this type of conditional visuomotor task appears to engage the premotor dorsal region (PMd). However, the extent to which PMd might be involved in specific or all processes of conditional learning is not well understood. Using transcranial magnetic stimulation (TMS), we demonstrate the role of human PMd in specific stages of learning of a novel conditional visuomotor task that required subjects to identify object center of mass using a color cue and to apply appropriate torque on the object at lift onset to minimize tilt. TMS over PMd, but not vertex, increased error in torque exerted on the object during the learning trials. Analyses of digit position and forces further revealed that the slowing in conditional visuomotor learning resulted from impaired monitoring of the object orientation during lift, rather than stimulus identification, thus compromising the ability to accurately reduce performance error across trials. Importantly, TMS over PMd did not alter production of torque based on the recall of learned color-torque associations. We conclude that the role of PMd for conditional learning is highly sensitive to the stage of learning visuomotor associations.

  17. Dual-Tasking Alleviated Sleep Deprivation Disruption in Visuomotor Tracking: An fMRI Study

    Science.gov (United States)

    Gazes, Yunglin; Rakitin, Brian C.; Steffener, Jason; Habeck, Christian; Butterfield, Brady; Basner, Robert C.; Ghez, Claude; Stern, Yaakov

    2012-01-01

    Effects of dual-responding on tracking performance after 49-h of sleep deprivation (SD) were evaluated behaviorally and with functional magnetic resonance imaging (fMRI). Continuous visuomotor tracking was performed simultaneously with an intermittent color-matching visual detection task in which a pair of color-matched stimuli constituted a…

  18. Dual-Tasking Alleviated Sleep Deprivation Disruption in Visuomotor Tracking: An fMRI Study

    Science.gov (United States)

    Gazes, Yunglin; Rakitin, Brian C.; Steffener, Jason; Habeck, Christian; Butterfield, Brady; Basner, Robert C.; Ghez, Claude; Stern, Yaakov

    2012-01-01

    Effects of dual-responding on tracking performance after 49-h of sleep deprivation (SD) were evaluated behaviorally and with functional magnetic resonance imaging (fMRI). Continuous visuomotor tracking was performed simultaneously with an intermittent color-matching visual detection task in which a pair of color-matched stimuli constituted a…

  19. Visuospatial and visuomotor deficits in preterm children : The involvement of cerebellar dysfunctioning

    NARCIS (Netherlands)

    Van Braeckel, Koenraad N. J. A.; Taylor, H. Gerry

    2013-01-01

    One of the more consistent findings in follow-up studies of preterm children is a deficit in visuospatial and visuomotor skills. Impairment of the dorsal visual stream and basal ganglia damage have been hypothesized to underlie this deficit. However, given recent findings of impaired cerebellar deve

  20. Evidence of enhancement of spatial attention during inhibition of a visuo-motor response

    NARCIS (Netherlands)

    Maguire, RP; Broerse, A; de Jong, BM; Cornelissen, FW; Meiners, LC; Leenders, KL; den Boer, JA

    2003-01-01

    A visuo-motor task was used as the setting for a study into inhibition in six healthy volunteers using fMRI. The task involved responding to colored stimuli, which appeared at random positions in the left and right visual field, with the corresponding hand. The volunteers were asked to respond to gr

  1. Evidence of enhancement of spatial attention during inhibition of a visuo-motor response

    NARCIS (Netherlands)

    Maguire, RP; Broerse, A; de Jong, BM; Cornelissen, FW; Meiners, LC; Leenders, KL; den Boer, JA

    2003-01-01

    A visuo-motor task was used as the setting for a study into inhibition in six healthy volunteers using fMRI. The task involved responding to colored stimuli, which appeared at random positions in the left and right visual field, with the corresponding hand. The volunteers were asked to respond to

  2. Visuomotor performance in a patient with visual agnosia due to an early lesion.

    Science.gov (United States)

    Dijkerman, H Chris; Lê, Sandra; Démonet, Jean-François; Milner, A David

    2004-06-01

    We tested a patient with visual agnosia who had suffered severe bilateral brain damage early in life, on a series of visuomotor tasks. The broad pattern of results confirms that S.B., like the extensively tested patient D.F., shows an impressive array of preserved skills, despite his severe perceptual problems. Also like D.F., S.B. shows certain subtle visuomotor difficulties that can be related to the idea that his partially intact occipito-parietal areas are unable to benefit from interactions with the apparently severely damaged occipito-temporal regions. Unlike D.F., however, he is able to make accurate discriminations of simple visual features, such as object width and orientation, albeit with very slow response times. We hypothesize that several factors such as the early onset of S.B.'s lesion and the long period since his brain lesion have allowed his brain to compensate to a degree what has been impossible in D.F., whose brain damage occurred in adulthood. This may include an element of 'rewiring' and self-monitoring of visuomotor processes that allow S.B. to achieve perceptual access to visual information processed in the dorsal stream: information that is normally only available for on-line visuomotor control.

  3. Concurrent visuomotor behaviour improves form discrimination in a patient with visual form agnosia.

    Science.gov (United States)

    Schenk, Thomas; Milner, A David

    2006-09-01

    It is now well established that the visual brain is divided into two visual streams, the ventral and the dorsal stream. Milner and Goodale have suggested that the ventral stream is dedicated for processing vision for perception and the dorsal stream vision for action [A.D. Milner & M.A. Goodale (1995) The Visual Brain in Action, Oxford University Press, Oxford]. However, it is possible that ongoing processes in the visuomotor stream will nevertheless have an effect on perceptual processes. This possibility was examined in the present study. We have examined the visual form-discrimination performance of the form-agnosic patient D.F. with and without a concurrent visuomotor task, and found that her performance was significantly improved in the former condition. This suggests that the visuomotor behaviour provides cues that enhance her ability to recognize the form of the target object. In control experiments we have ruled out proprioceptive and efferent cues, and therefore propose that D.F. can, to a significant degree, access the object's visuomotor representation in the dorsal stream. Moreover, we show that the grasping-induced perceptual improvement disappears if the target objects only differ with respect to their shape but not their width. This suggests that shape information per se is not used for this grasping task.

  4. Integrated intensive proprioceptive and visuomotor rehabilitation program for treatment of spastic diplegic Children

    Directory of Open Access Journals (Sweden)

    Fathy A. Elshazly

    2016-08-01

    Full Text Available Although so many rehabilitation programs have been addressed for rehabilitation of diplegic children, it still a challenging task to attain a satisfactory functional recovery. The purpose of the study was to investigate the efficacy of an intensive proprioceptive and visuomotor training program in the treatment of diplegic children in term of spatiotemporal gait parameters, postural stability, and quality of life. In a prospective randomized controlled trial, convenient sample of forty ambulant diplegic children were randomly distributed to either control (n=20 or study (n=20 groups; the control group received a traditional rehabilitation program for 1 hour, 5 times/week for 3 successive months, while the study group received the same program with intensive proprioceptive and visuomotor integration. Vicon 3D motion analysis system, Technobody balance system and Pediatric Quality of life Inventory were used to measure spatiotemporal gait parameters, stability indices and quality of life respectively. all parameters were similar in both groups at inception (p˃0.05. Children within both groups showed improvement of gait function, postural stability and quality of life (p˂0.05 and the integrated proprioceptive and visuomotor rehabilitation program achieved better gain (p˂0.05. Integrated proprioceptive and visuomotor rehabilitation might improve gait function, postural stability, and quality of life in diplegic children.

  5. Visuo-motor integration in unresponsive wakefulness syndrome: A piece of the puzzle towards consciousness detection?

    Science.gov (United States)

    Naro, Antonino; Leo, Antonino; Filoni, Serena; Bramanti, Placido; Calabrò, Rocco Salvatore

    2015-01-01

    Abstract Purpose: The unresponsive wakefulness syndrome (UWS) is characterized by either a profound unawareness or an impairment of large-scale cortico/subcortical connectivity. Nevertheless, some individuals with UWS could show residual markers of consciousness and cognition. In this study, we applied an electrophysiological approach aimed to identify the residual visuomotor connectivity patterns that are thought to be linked to awareness, in patients with chronic disorder of consciousness (DOC). Methods: We measured some markers of visuomotor and premotor-motor integration in 14 patients affected by DOC, before and after the application of transcranial direct current stimulation, delivered over the dorsolateral prefrontal cortex and the parieto-occipital area, paired to transorbital alterning current stimulation. Results: Our protocol induced a potentiation of the electrophysiological markers of visuomotor and premotor-motor connectivity, paired to a clinical improvement, in all of the patients with minimally conscious state and in one individual affected by UWS. Conclusions: Our protocol could be a promising approach to potentiate the functional connectivity within large-scale visuomotor networks, thus allowing identifying the patients suffering from a functional locked-in syndrome (i.e. individuals showing an extreme behavioral motor dysfunction although with somehow preserved cognitive functions that can be identified only through para-clinical tests) within individuals with UWS. PMID:26409404

  6. Changes in the Spinal Neural Circuits are Dependent on the Movement Speed of the Visuomotor Task.

    Science.gov (United States)

    Kubota, Shinji; Hirano, Masato; Koizume, Yoshiki; Tanabe, Shigeo; Funase, Kozo

    2015-01-01

    Previous studies have shown that spinal neural circuits are modulated by motor skill training. However, the effects of task movement speed on changes in spinal neural circuits have not been clarified. The aim of this research was to investigate whether spinal neural circuits were affected by task movement speed. Thirty-eight healthy subjects participated in this study. In experiment 1, the effects of task movement speed on the spinal neural circuits were examined. Eighteen subjects performed a visuomotor task involving ankle muscle slow (nine subjects) or fast (nine subjects) movement speed. Another nine subjects performed a non-visuomotor task (controls) in fast movement speed. The motor task training lasted for 20 min. The amounts of D1 inhibition and reciprocal Ia inhibition were measured using H-relfex condition-test paradigm and recorded before, and at 5, 15, and 30 min after the training session. In experiment 2, using transcranial magnetic stimulation (TMS), the effects of corticospinal descending inputs on the presynaptic inhibitory pathway were examined before and after performing either a visuomotor (eight subjects) or a control task (eight subjects). All measurements were taken under resting conditions. The amount of D1 inhibition increased after the visuomotor task irrespective of movement speed (P circuits, and that task movement speed is one of the critical factors for inducing plastic changes in reciprocal Ia inhibition.

  7. Behavioral Self-Regulation and Executive Function Both Predict Visuomotor Skills and Early Academic Achievement

    Science.gov (United States)

    Becker, Derek R.; Miao, Alicia; Duncan, Robert; McClelland, Megan M.

    2014-01-01

    The present study explored direct and interactive effects between behavioral self-regulation (SR) and two measures of executive function (EF, inhibitory control and working memory), with a fine motor measure tapping visuomotor skills (VMS) in a sample of 127 prekindergarten and kindergarten children. It also examined the relative contribution of…

  8. Parallel Specification of Visuomotor Feedback Gains during Bimanual Reaching to Independent Goals

    Science.gov (United States)

    Gallivan, Jason P.

    2017-01-01

    Abstract During goal-directed reaching, rapid visuomotor feedback processes enable the human motor system to quickly correct for errors in the trajectory of the hand that arise from motor noise and, in some cases, external perturbations. To date, these visuomotor responses, the gain of which is sensitive to features of the task and environment, have primarily been examined in the context of unimanual reaching movements toward a single target. However, many natural tasks involve moving both hands together, often to separate targets, such that errors can occur in parallel and at different spatial locations. Here, we examined the resource capacity of automatic visuomotor corrective mechanisms by comparing feedback gains during bimanual reaches, toward two targets, to feedback gains during unimanual reaches toward single targets. To investigate the sensitivity of the feedback gains and their relation to visual-spatial processing, we manipulated the widths of the targets and participants’ gaze location. We found that the gain of corrective responses to cursor displacements, while strongly modulated by target width and gaze position, were only slightly reduced during bimanual control. Our results show that automatic visuomotor corrective mechanisms can efficiently operate in parallel across multiple spatial locations.

  9. On the Dynamics of the Massless Spin-1 Particles in the Rotating Cosmological Models

    CERN Document Server

    Salti, M; Havare, A; Korunur, M; Salti, Mustafa; Aydogdu, Oktay; Havare, Ali; Korunur, Murat

    2005-01-01

    In the present article, we have considered massless Duffin-Kemmer-Petiau equation for the general rotating space-times, and obtain its second order form in this cosmological model. Considering this second order differential equation for some well-known cosmological model which are included by the our general line-element, we obtain exact solution of the massless Duffin-Kemmer-Petiau equation. On the other hand, by using spinor form of the Maxwell equations the propagation problem is reduced to the solution of the second order differential equation of complex combination of the electric and magnetic fields. For these two different approach we obtain the spinors in terms of field strength tensor.

  10. Speckle dynamics for dual-beam optical illumination of a rotating structure

    DEFF Research Database (Denmark)

    Jakobsen, Michael Linde; Yura, Harold; Hanson, Steen Grüner

    2009-01-01

    An out-of-plane rotating object is illuminated with two spatially separated coherent beams, giving rise to fully developed speckles, which will translate and gradually decorrelate in the observation plane, located in the far field. The speckle pattern is a compound structure, consisting of random...... speckles modulated by a smaller and repetitive structure. Generally, these two components of the compound speckle structure will move as rigid structures with individual velocities determined by the characteristics of the two illuminating beams. Closed-form analytical expressions are found for the space......- and time-lagged covariance of irradiance and the corresponding power spectrum for the two spatially separated illuminating beams. The present analysis is valid for propagation through an arbitrary ABCD system, though the focus for the experimental evaluation is far-field observations using an optical...

  11. Dynamical instability in a relativistic cylindrical shell composed of counter rotating particles

    CERN Document Server

    Kurita, Yasunari

    2011-01-01

    We give a perturbative analysis for an infinitesimally thin cylindrical shell composed of counter rotating collisionless particles, originally devised by Apostolatos and Thorne. They found a static solution of the shell and concluded by C-energy argument that it is stable. Recently, the present authors and Ida reanalyzed this system by evaluating the C-energy on the future null infinity and found that the system has an instability, though it was not shown how the system is unstable. In this paper, it is shown in the framework of the linear perturbation theory that, if the constituent particles move slowly, the static shell is unstable in the sense that the perturbation of its circumferential radius oscillates with exponentially growing amplitude, whereas if the speed of the constituent particle exceeds a critical value, the shell just expands or contracts exponentially with time.

  12. Rotation and migration of nanoparticles for heat transfer augmentation in nanofluids by molecular dynamics simulation

    Directory of Open Access Journals (Sweden)

    Wenzheng Cui

    2015-09-01

    Full Text Available Nanofluids are a new generation of high-efficiency refrigerant with abnormal increased thermal conductivity and convective heat transfer properties. In view of the paucity of research work on the contribution of nanoparticle Brownian motion for the thermal conductivity augmentation, the present paper carries out a series of MD simulations to explorer the order of magnitude of nanoparticle Brownian motion and discusses the effect of nanoparticle Brownian motion for thermal conductivity enhancement of nanofluids. Various influence factors including nanoparticle shapes, sizes, and materials are considered. The Brownian motion of nanoparticles is decomposed into rotation and migration and calculated by MD simulation. By means of Peclet number, the effect of nanoparticle Brownian motion for thermal conductivity enhancement of nanofluids is discussed.

  13. GEODYNAMICS AS WAVE DYNAMICS OF THE MEDIUM COMPOSED OF ROTATING BLOCKS

    Directory of Open Access Journals (Sweden)

    Alexander V. Vikulin

    2015-10-01

    Full Text Available The geomedium block concept envisages that stresses in the medium composed of rotating blocks have torque and thus predetermine the medium's energy capacity (in terms of [Ponomarev, 2008]. The present paper describes the wave nature of the global geodynamic process taking place in the medium characterized by the existence of slow and fast rotation strain waves that are classified as a new type of waves. Movements may also occur as rheid, superplastic and/or superfluid motions and facilitate the formation of vortex geological structures in the geomedium.Our analysis of data on almost 800 strong volcanic eruptions shows that the magma chamber’s thickness is generally small, about 0.5 km, and this value is constant, independent of the volcanic process and predetermined by properties of the crust. A new magma chamber model is based on the idea of 'thermal explosion’/‘self-acceleration' manifested by intensive plastic movements along boundaries between the blocks in conditions of the low thermal conductivity of the geomedium. It is shown that if the solid rock in the magma chamber is overheated above its melting point, high stresses may occur in the surrounding area, and their elastic energy may amount to 1015 joules per 1 km3 of the overheated solid rock. In view of such stresses, it is possible to consider the interaction between volcano’s magma chambers as the migration of volcanic activity along the volcanic arc and provide an explanation of the interaction between volcanic activity and seismicity within the adjacent parallel arcs.The thin overheated interlayer/magma chamber concept may be valid for the entire Earth's crust. In our hypothesis, properties of the Moho are determined by the phase transition from the block structure of the crust to the nonblock structure of the upper mantle.

  14. An `analytic dynamical magnetosphere' formalism for X-ray and optical emission from slowly rotating magnetic massive stars

    Science.gov (United States)

    Owocki, Stanley P.; ud-Doula, Asif; Sundqvist, Jon O.; Petit, Veronique; Cohen, David H.; Townsend, Richard H. D.

    2016-11-01

    Slowly rotating magnetic massive stars develop `dynamical magnetospheres' (DMs), characterized by trapping of stellar wind outflow in closed magnetic loops, shock heating from collision of the upflow from opposite loop footpoints, and subsequent gravitational infall of radiatively cooled material. In 2D and 3D magnetohydrodynamic (MHD) simulations, the interplay among these three components is spatially complex and temporally variable, making it difficult to derive observational signatures and discern their overall scaling trends. Within a simplified, steady-state analysis based on overall conservation principles, we present here an `analytic dynamical magnetosphere' (ADM) model that provides explicit formulae for density, temperature, and flow speed in each of these three components - wind outflow, hot post-shock gas, and cooled inflow - as a function of colatitude and radius within the closed (presumed dipole) field lines of the magnetosphere. We compare these scalings with time-averaged results from MHD simulations, and provide initial examples of application of this ADM model for deriving two key observational diagnostics, namely hydrogen H α emission line profiles from the cooled infall, and X-ray emission from the hot post-shock gas. We conclude with a discussion of key issues and advantages in applying this ADM formalism towards derivation of a broader set of observational diagnostics and scaling trends for massive stars with such dynamical magnetospheres.

  15. Evaluation of reptation-based modeling of entangled polymeric fluids including chain rotation via nonequilibrium molecular dynamics simulation

    Science.gov (United States)

    Nafar Sefiddashti, Mohammad Hadi; Edwards, Brian J.; Khomami, Bamin

    2017-08-01

    Recent simulation results of a moderately entangled linear polyethylene C700H1402 liquid have confirmed prior simulation and experimental evidence that individual polymer molecules experience periodic rotation and retraction cycles under steady shear flow at high Weissenberg number. With this insight, theoreticians have begun to grapple with this additional complicating physical phenomenon that needs to be incorporated into rheological models to help explain the data under conditions of high shear. In this paper we examine these recent efforts by using nonequilibrium molecular dynamics simulations to provide insight into the requisite theoretical variables and their assigned evolution equations to evaluate the capability of these tube-based models to predict accurately the simulated data sets. This analysis reveals that the primary variables used in tube models to impart a conceptual basis to the theory, namely, the tube orientation tensor and the tube stretch, remain fundamental system properties even far away from equilibrium; however, the theory describing their evolution under flow is not well suited to quantitative prediction. Furthermore, it is demonstrated that key system properties, such as the entanglement number and disengagement time, should play a more significant role in model development since these quantities can change dramatically under flow, particularly at high Weissenberg number where the chain rotation and retraction cycles dominate the system physics.

  16. [Seasonal dynamics of quantitative and morphological traits of poplar fine roots and their differences between successive rotation plantations].

    Science.gov (United States)

    Wang, Yan-ping; Xu, Tan; Zhu, Wan-rui; Wang, Qi-tong; Liu, Meng-ling; Wang, Hua-tian; Li, Chuan-rong; Dong, Yu-feng

    2016-02-01

    Based on the fine root samples of the first and second generations of poplar (Populus x euramericana ' Neva'), this study examined the response of quantitative and morphological traits of fine roots of different orders and the difference between generations. The results showed that, the quantitative traits of fine roots, such as root length, root surface area and root biomass, presented obvious seasonal variation, and the fine root traits had obvious difference among root orders. The quantitative traits of lower-order fine roots showed significant seasonal difference, and the fine root biomass increased in the growing season and then decreased significantly. The specific root length (SRL) of higher-order roots also showed significant change with season, while the root length density (RLD) and root tissue density (RTD) changed a little. The successive rotation resulted in the significant increase of root length, root biomass, SRL and RLD of 1-2 orders in the growing season. The quantitative traits of first order root significantly positively correlated with soil temperature and moisture, and significantly negatively correlated with the soil organic matter and soil available nitrogen content. However, the quantitative traits of second order root only showed significant correlation with soil nutrient content. The seasonal dynamics of poplar fine roots and the difference between successive rotation plantations implied carbon investment change of poplar to roots. Soil nutrient deficiency induced more carbon investment into roots, and this carbon allocation pattern might affect the aboveground productivity of poplar plantation.

  17. Towards mastery of complex visuo-motor transformations

    Directory of Open Access Journals (Sweden)

    Herbert eHeuer

    2013-02-01

    Full Text Available In this paper we review and integrate a set of findings on learning the transformation of a sliding first-order lever, a type of tool with a prominent role in minimal access surgery. Its kinematic transformation is characterized by the so-called fulcrum effect, the inversion of the movement direction of the tip of the lever relative to that of the hand for rotations. A second characteristic is gain anisotropy, which results in curved paths of the tip of the lever for straight paths of the hand and vice versa. An internal model of the kinematic transformation is acquired during practice, the accuracy of which can be assessed in visual open-loop test trials. The accuracy of the acquired internal model is enhanced when visual closed-loop control during practice is impeded, and the accuracy of the internal model is reduced when closed-loop control during practice is facilitated. The internal model consists of a rapidly acquired line-symmetric approximation to the transformation of the sliding lever and a slowly acquired fine tuning. The fine tuning is local, that is, it is specific for the region of the workspace encountered during practice. The internal model is transferred to other regions of the workspace, but not adjusted to the fine tuning appropriate for these regions. Whereas the symmetry approximation is most likely explicit, the fine tuning seems to be represented implicitly. Findings on the straightness of the paths of the tip of the lever and the hand suggest that the internal model of the transformation is confined to initial and final positions of aimed movements, whereas their path is not strictly controlled, but affected by the dynamic transformation of the tool. Only when visual closed-loop control is possible, the path of the effective part of the tool is straightened. These characteristics of the internal model of the sliding first-order lever and its acquisition may be partly specific to sufficiently complex extrinsic

  18. Complex Rotation Quantum Dynamic Neural Networks (CRQDNN) using Complex Quantum Neuron (CQN): Applications to time series prediction.

    Science.gov (United States)

    Cui, Yiqian; Shi, Junyou; Wang, Zili

    2015-11-01

    Quantum Neural Networks (QNN) models have attracted great attention since it innovates a new neural computing manner based on quantum entanglement. However, the existing QNN models are mainly based on the real quantum operations, and the potential of quantum entanglement is not fully exploited. In this paper, we proposes a novel quantum neuron model called Complex Quantum Neuron (CQN) that realizes a deep quantum entanglement. Also, a novel hybrid networks model Complex Rotation Quantum Dynamic Neural Networks (CRQDNN) is proposed based on Complex Quantum Neuron (CQN). CRQDNN is a three layer model with both CQN and classical neurons. An infinite impulse response (IIR) filter is embedded in the Networks model to enable the memory function to process time series inputs. The Levenberg-Marquardt (LM) algorithm is used for fast parameter learning. The networks model is developed to conduct time series predictions. Two application studies are done in this paper, including the chaotic time series prediction and electronic remaining useful life (RUL) prediction.

  19. Prospects in the orbital and rotational dynamics of the Moon with the advent of sub-centimeter lunar laser ranging

    CERN Document Server

    Kopeikin, S M; Pavlis, D; Brumberg, V A; Escapa, A; Getino, J; Gusev, A; Müller, J; Ni, W -T; Petrova, N

    2007-01-01

    Lunar Laser Ranging (LLR) measurements are crucial for advanced exploration of the laws of fundamental gravitational physics and geophysics. Current LLR technology allows us to measure distances to the Moon with a precision approaching 1 millimeter. As NASA pursues the vision of taking humans back to the Moon, new, more precise laser ranging applications will be demanded, including continuous tracking from more sites on Earth, placing new CCR arrays on the Moon, and possibly installing other devices such as transponders, etc. Successful achievement of this goal strongly demands further significant improvement of the theoretical model of the orbital and rotational dynamics of the Earth-Moon system. This model should inevitably be based on the theory of general relativity, fully incorporate the relevant geophysical processes, lunar librations, tides, and should rely upon the most recent standards and recommendations of the IAU for data analysis. This paper discusses methods and problems in developing such a mat...

  20. Dynamic Mechanism of Sustainable Molecular Orientation Generated From Cyclic Rotational States

    Institute of Scientific and Technical Information of China (English)

    CHI Fang-Ping; YANG Yu-Jun; HUANG Yu-Xin; ZHU Qi-Ren

    2006-01-01

    @@ Recently, two papers presented by Ortigoso et al. [Phys. Rev. Lett. 93 (2004) 073001 and Phys. Rev. A 72(2005) 053401] develop a novel strategy in which the best sustainable molecular alignment/orientation has been achieved. We intend to analyse the dynamic mechanisms, including those Ortigoso et al. have not clarified.

  1. Dynamics of viscous fingers in rotating Hele-Shaw cells with Coriolis effects.

    Science.gov (United States)

    Gadêlha, Hermes; Brito, Nielison; Miranda, José A

    2007-01-01

    A growing number of experimental and theoretical works have been addressing various aspects of the viscous fingering formation in rotating Hele-Shaw cells. However, only a few of them consider the influence of Coriolis forces. The studies including Coriolis effects are mostly restricted to the high-viscosity-contrast limit and rely on either purely linear stability analyses or intensive numerical simulations. We approach the problem analytically and use a modified Darcy's law including the exact form of the Coriolis effects to execute a mode-coupling analysis of the system. By imposing no restrictions on the viscosity contrast A (dimensionless viscosity difference) we go beyond linear stages and examine the onset of nonlinearities. Our results indicate that when Coriolis effects are taken into account, an interesting interplay between the Reynolds number Re and A arises. This leads to important changes in the stability and morphological features of the emerging interfacial patterns. We contrast our mode-coupling approach with previous theoretical models proposed in the literature.

  2. First Gaia Local Group Dynamics: Magellanic Clouds Proper Motion and Rotation

    CERN Document Server

    van der Marel, Roeland P

    2016-01-01

    We use the Gaia data release 1 (DR1) to study the proper motion (PM) fields of the Large and Small Magellanic Clouds (LMC, SMC). This uses the Tycho-Gaia Astrometric Solution (TGAS) PMs for 29 Hipparcos stars in the LMC and 8 in the SMC. The LMC PM in the West and North directions is inferred to be $(\\mu_W,\\mu_N) = (1.874 \\pm 0.039, 0.223 \\pm 0.049)$ mas/yr, and the SMC PM $(\\mu_W,\\mu_N) = (0.876 \\pm 0.060, 1.227 \\pm 0.042)$ mas/yr. These results have similar accuracy and agree to within the uncertainties with existing Hubble Space Telescope (HST) PM measurements. Since TGAS uses different methods with different systematics, this provides an external validation of both data sets and their underlying approaches. Residual DR1 systematics may affect the TGAS results, but the HST agreement implies this must be below the random errors. Also in agreement with prior HST studies, the TGAS LMC PM field clearly shows the clockwise rotation of the disk, even though it takes the LMC disk in excess of $10^8$ years to comp...

  3. Structure and Rotational Dynamics of Isoamyl Acetate and Methyl Propionate Studied by Microwave Spectroscopy

    Science.gov (United States)

    Stahl, W.; Nguyen, H. V. L.; Sutikdja, L. W.; Jelisavac, D.; Mouhib, H.; Kleiner, I.

    2012-06-01

    The microwave spectra of a number of organic aliphatic esters have been recorded for the first time in the 3-26.5 GHz frequency range, using the molecular beam Fourier-transform microwave (MB-FTMW) spectrometer in Aachen, with an instrumental uncertainty of a few kHz for unblended lines. The combined use of ab initio quantum chemical calculations and spectral analysis allowed us to determine the spectroscopic parameters and potential barriers to internal rotation of the methyl groups for the lowest energy conformers. We will compare here the results from ab initio calculations and from two different hamiltonian methods (the XIAM and BELGI codes) for isoamyl acetate H3C-COO-(CH2)2-CH(CH3)2, an one-top internal rotor molecule with a C1 symmetry and for methyl propionate CH3CH2COOCH3 containing two inequivalent methyl tops (C3v), with different barrier heights. This study is part of a larger project which aims at determining the structures of the lowest energy conformers for a serie of organic esters and ketones which are of interest for flavour or perfume applications.

  4. Nonlinear dynamics and synchronisation of pendula attached to a rotating hub

    Science.gov (United States)

    Warminski, J.; Szmit, Z.; Latalski, J.

    2014-04-01

    A model of a nonlinear system composed of a hub with attached two pendula rotating in a horizontal plane is studied in the paper. Each single pendulum, treated as a stiff and massless rod with a lumped mass, is connected to the hub by a flapping hinge. Nonlinear stiffness and viscous damping of the hinge is taken into consideration. The system is excited by an external torque generated by a DC motor which is considered as an ideal system with torque given by a harmonic function. For small oscillations the problem is linearised and then solved analytically. An influence of the structural parameters like mass of the hub and pendula length on natural end excited vibrations is presented. Large oscillations are studied by a continuation technique, directly from the original Ordinary Differential Equations of motion (ODE). The complete synchronisation, phase synchronisation, bifurcations and transition through resonances are analysed considering the influence of the mass of the hub. The existence of chaotic oscillations of the system and paths leading to chaos are demonstrated as well.

  5. Temperature dependence of cross-effect dynamic nuclear polarization in rotating solids

    DEFF Research Database (Denmark)

    Geiger, Michel-Andreas; Orwick-Rydmark, Marcella; Märker, Katharina

    2016-01-01

    Dynamic nuclear polarization exploits electron spin polarization to boost signal-to-noise in magic-angle-spinning (MAS) NMR, creating new opportunities in materials science, structural biology, and metabolomics studies. Since protein NMR spectra recorded under DNP conditions can show improved...... the importance of protons in a sphere of 4-6 Å around the nitroxyl group, presumably for polarization pickup from electron spins....

  6. Measurement Research of Motorized Spindle Dynamic Stiffness under High Speed Rotating

    Directory of Open Access Journals (Sweden)

    Xiaopeng Wang

    2015-01-01

    Full Text Available High speed motorized spindle has become a key functional unit of high speed machine tools and effectively promotes the development of machine tool technology. The development of higher speed and more power puts forward the stricter requirement for the performance of motorized spindle, especially the dynamic performance which affects the machining accuracy, reliability, and production efficiency. To overcome the problems of ineffective loading and dynamic performance measurement of motorized spindle, a noncontact electromagnetic loading device is developed. The cutting load can be simulated by using electromagnetic force. A new method of measuring force by force sensors is presented, and the steady and transient loading force could be measured exactly. After the high speed machine spindle is tested, the frequency response curves of the spindle relative to machine table are collected at 0~12000 rpm; then the relationships between stiffness and speeds as well as between damping ratio and speeds are obtained. The result shows that not only the static and dynamic stiffness but also the damping ratio declined with the increase of speed.

  7. A discrete chemo-dynamical model of the dwarf spheroidal galaxy Sculptor: mass profile, velocity anisotropy and internal rotation

    CERN Document Server

    Zhu, Ling; Watkins, Laura L; Posti, Lorenzo

    2016-01-01

    We present a new discrete chemo-dynamical axisymmetric modeling technique, which we apply to the dwarf spheroidal galaxy Sculptor. The major improvement over previous Jeans models is that realistic chemical distributions are included directly in the dynamical modelling of the discrete data. This avoids loss of information due to spatial binning and eliminates the need for hard cuts to remove contaminants and to separate stars based on their chemical properties. Using a combined likelihood in position, metallicity and kinematics, we find that our models naturally separate Sculptor stars into a metal-rich and a metal-poor population. Allowing for non-spherical symmetry, our approach provides a central slope of the dark matter density of $\\gamma = 0.5 \\pm 0.3$. The metal-rich population is nearly isotropic (with $\\beta_r^{red} = 0.0\\pm0.1$) while the metal-poor population is tangentially anisotropic (with $\\beta_r^{blue} = -0.2\\pm0.1$) around the half light radius of $0.26$ kpc. A weak internal rotation of the m...

  8. The low-temperature inflection observed in neutron scattering measurements of proteins is due to methyl rotation: direct evidence using isotope labeling and molecular dynamics simulations.

    Science.gov (United States)

    Wood, Kathleen; Tobias, Douglas J; Kessler, Brigitte; Gabel, Frank; Oesterhelt, Dieter; Mulder, Frans A A; Zaccai, Giuseppe; Weik, Martin

    2010-04-14

    There is increasing interest in the contribution of methyl groups to the overall dynamics measured by neutron scattering experiments of proteins. In particular an inflection observed in atomic mean square displacements measured as a function of temperature on high resolution spectrometers (approximately 1 microeV) was explained by the onset of methyl group rotations. By specifically labeling a non-methyl-containing side-chain in a native protein system, the purple membrane, and performing neutron scattering measurements, we here provide direct experimental evidence that the observed inflection is indeed due to methyl group rotations. Molecular dynamics simulations reproduce the experimental data, and their analysis suggests that the apparent transition is due to methyl group rotation entering the finite instrumental resolution of the spectrometer. Methyl group correlation times measured by solid state NMR in the purple membrane, taken from previous work, support the interpretation.

  9. Modeling dynamic stall on wind turbine blades under rotationally augmented flow fields

    DEFF Research Database (Denmark)

    Guntur, Srinivas; Sørensen, Niels N.; Schreck, Scott

    2016-01-01

    Experiment Phase VI experimental data, including constant as well as continuously pitching blade conditions during axial operation; (2) data from unsteady delayed detached eddy simulations (DDES) carried out using the Technical University of Denmark’s in-house flow solver Ellipsys3D; and (3) data from...... agreement between the model and the experimental data in many cases, which suggests that the current two-dimensional dynamic stall model as used in blade element momentum-based aeroelastic codes may provide a reasonably accurate representation of three-dimensional rotor aerodynamics when used in combination...

  10. Crop rotation design in view of soilborne pathogen dynamics : a methodological approach illustrated with Sclerotium rolfsii and Fusarium oxysporum f.sp. cepae

    NARCIS (Netherlands)

    Leoni, C.

    2013-01-01

    Key words: Sclerotium rolfsii, Fusarium oxysporum f.sp. cepae, soilborne pathogens, crop rotation, population dynamic models, simulation.   During the last decades, agriculture went through an intensification process associated with an increased use of fossil fuel energy, which despite tempor

  11. Analysis of the dynamics of adaptation to transgenic corn and crop rotation by western corn rootworm (Coleoptera: Chrysomelidae) using a daily time-step model.

    Science.gov (United States)

    Crowder, D W; Onstad, D W; Cray, M E; Pierce, C M F; Hager, A G; Ratcliffe, S T; Steffey, K L

    2005-04-01

    Western corn rootworm, Diabrotica virgifera virgifera LeConte, has overcome crop rotation in several areas of the north central United States. The effectiveness of crop rotation for management of corn rootworm has begun to fail in many areas of the midwestern United States, thus new management strategies need to be developed to control rotation-resistant populations. Transgenic corn, Zea mays L., effective against western corn rootworm, may be the most effective new technology for control of this pest in areas with or without populations adapted to crop rotation. We expanded a simulation model of the population dynamics and genetics of the western corn rootworm for a landscape of corn; soybean, Glycine max (L.); and other crops to study the simultaneous development of resistance to both crop rotation and transgenic corn. Results indicate that planting transgenic corn to first-year cornfields is a robust strategy to prevent resistance to both crop rotation and transgenic corn in areas where rotation-resistant populations are currently a problem or may be a problem in the future. In these areas, planting transgenic corn only in continuous cornfields is not an effective strategy to prevent resistance to either trait. In areas without rotation-resistant populations, gene expression of the allele for resistance to transgenic corn, R, is the most important factor affecting the evolution of resistance. If R is recessive, resistance can be delayed longer than 15 yr. If R is dominant, resistance may be difficult to prevent. In a sensitivity analysis, results indicate that density dependence, rotational level in the landscape, and initial allele frequency are the three most important factors affecting the results.

  12. Population dynamics of Meloidogyne arenaria and Pasteuria penetrans in a long-term crop rotation study.

    Science.gov (United States)

    Timper, Patricia

    2009-12-01

    The endospore-forming bacterium Pasteuria penetrans is an obligate parasite of root-knot nematodes (Meloidogyne spp.). The primary objective of this study was to determine the effect of crop sequence on abundance of P. penetrans. The experiment was conducted from 2000 to 2008 at a field site naturally infested with both the bacterium and its host Meloidogyne arenaria and included the following crop sequences: continuous peanut (Arachis hypogaea) (P-P-P) and peanut rotated with either 2 years of corn (Zea mays) (C-C-P), 1 year each of cotton (Gossypium hirsutum) and corn (Ct-C-P), or 1 year each of corn and a vegetable (V-C-P). The vegetable was a double crop of sweet corn and eggplant (Solanum melongena). A bioassay with second-stage juveniles (J2) of M. arenaria from a greenhouse (GH) population was used to estimate endospore abundance under the different crop sequences. A greater numerical increase in endospore densities was expected in the P-P-P and V-C-P sequences than in the other sequences because both peanut and eggplant are good hosts for M. arenaria. However, endospore densities, as determined by bioassay, did not substantially increase in any of the sequences during the 9-year experiment. To determine whether the nematode population had developed resistance to the resident P. penetrans, five single egg-mass (SEM) lines from the field population of M. arenaria were tested alongside the GH population for acquisition of endospores from the field soil. Four of the five SEM lines acquired 9 to 14 spores/J2 whereas the GH population and one of the SEM lines acquired 3.5 and 1.8 spores/J2, respectively. Endospore densities estimated with the four receptive SEM lines were highest in the P-P-P plots (14-20 spores/J2), intermediate in the V-C-P plots (6-7 spores/J2), and lowest in the Ct-C-P plots (cropping of hosts for M. arenaria, but the GH population of the nematode was not receptive to spore attachment. However, previously, the GH population was very receptive

  13. A new post-phase rotation based dynamic receive beamforming architecture for smartphone-based wireless ultrasound imaging

    Science.gov (United States)

    Park, Minsuk; Kang, Jeeun; Lee, Gunho; Kim, Min; Song, Tai-Kyong

    2016-04-01

    Recently, a portable US imaging system using smart devices is highlighted for enhancing the portability of diagnosis. Especially, the system combination can enhance the user experience during whole US diagnostic procedures by employing the advanced wireless communication technology integrated in a smart device, e.g., WiFi, Bluetooth, etc. In this paper, an effective post-phase rotation-based dynamic receive beamforming (PRBF-POST) method is presented for wireless US imaging device integrating US probe system and commercial smart device. In conventional, the frame rate of conventional PRBF (PRBF-CON) method suffers from the large amount of calculations for the bifurcated processing paths of in-phase and quadrature signal components as the number of channel increase. Otherwise, the proposed PRBF-POST method can preserve the frame rate regardless of the number of channels by firstly aggregating the baseband IQ data along the channels whose phase quantization levels are identical ahead of phase rotation and summation procedures on a smart device. To evaluate the performance of the proposed PRBF-POST method, the pointspread functions of PRBF-CON and PRBF-POST methods were compared each other. Also, the frame rate of each PRBF method was measured 20-times to calculate the average frame rate and its standard deviation. As a result, the PRBFCON and PRBF-POST methods indicates identical beamforming performance in the Field-II simulation (correlation coefficient = 1). Also, the proposed PRBF-POST method indicates the consistent frame rate for varying number of channels (i.e., 44.25, 44.32, and 44.35 fps for 16, 64, and 128 channels, respectively), while the PRBF-CON method shows the decrease of frame rate as the number of channel increase (39.73, 13.19, and 3.8 fps). These results indicate that the proposed PRBF-POST method can be more advantageous for implementing the wireless US imaging system than the PRBF-CON method.

  14. Linking partial and quasi dynamical symmetries in rotational nuclei and shell evolution in {sup 96}Zr

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, Christoph

    2016-01-27

    The first part of this thesis revolves around symmetries in the sd-IBA-1. A region of approximate O(6) symmetry for the ground-state band, a partial dynamical symmetry (PDS) of type III, in the parameter space of the extended consistent-Q formalism is identified through quantum number fluctuations. The simultaneous occurrence of a SU(3) quasi dynamical symmetry for nuclei in the region of O(6) PDS is explained via the β=1, γ=0 intrinsic state underlying the ground-state band. The previously unrelated concepts of PDS and QDS are connected for the first time and many nuclei in the rare earth region that approximately satisfy both symmetry requirements are identified. Ground-state to ground-state (p, t) transfer reactions are presented as an experimental signature to identify pairs of nuclei that both exhibit O(6) PDS. In the second part of this thesis inelastic electron scattering off {sup 96}Zr is studied. The experiment was performed at the high resolution Lintott spectrometer at the S-DALINAC and covered a momentum-transfer range of 0.28 - 0.59 fm{sup -1}. Through a relative analysis using Plane Wave Born Approximation (PWBA) the B(E2;2{sup +}{sub 2}→0{sup +}{sub 1}) value is extracted without incurring the additional model dependence of a Distorted Wave Born Approximation (DWBA). By combining this result with known multipole mixing ratios and branching ratios all decay strengths of the 2{sup +}{sub 2} state are determined. A mixing calculation establishes very weak mixing (V{sub mix}=76 keV) between states of the ground-state band and those of the band build on top of the 0{sup +}{sub 2} state which includes the 2{sup +}{sub 2} state. The occurrence of these two isolated bands is interpreted within the shell model in terms of type II shell evolution.

  15. Effect of the alkyl chain length on the rotational dynamics of nonpolar and dipolar solutes in a series of N-alkyl-N-methylmorpholinium ionic liquids.

    Science.gov (United States)

    Khara, Dinesh Chandra; Kumar, Jaini Praveen; Mondal, Navendu; Samanta, Anunay

    2013-05-01

    Rotational dynamics of two dipolar solutes, 4-aminophthalimide (AP) and 6-propionyl-2-dimethylaminonaphthalene (PRODAN), and a nonpolar solute, anthracene, have been studied in N-alkyl-N-methylmorpholinium (alkyl = ethyl, butyl, hexyl, and octyl) bis(trifluoromethansulfonyl)imide (Tf2N) ionic liquids as a function of temperature and excitation wavelength to probe the microheterogeneous nature of these ionic liquids, which are recently reported to be more structured than the imidazolium ionic liquids (Khara and Samanta, J. Phys. Chem. B2012, 116, 13430-13438). Analysis of the measured rotational time constants of the solutes in terms of the Stokes-Einstein-Debye (SED) hydrodynamic theory reveals that with increase in the alkyl chain length attached to the cationic component of the ionic liquids, AP shows stick to superstick behavior, PRODAN rotation lies between stick and slip boundary conditions, whereas anthracene exhibits slip to sub slip behavior. The contrasting rotational dynamics of these probe molecules is a reflection of their location in distinct environments of the ionic liquids thus demonstrating the heterogeneity of these ionic liquids. The microheterogeneity of these media, in particular, those with the long alkyl chain, is further evidence from the excitation wavelength dependence study of the rotational diffusion of the dipolar probe molecules.

  16. The effect of the nonlinear velocity and history dependencies of the aerodynamic force on the dynamic response of a rotating wind turbine blade

    Science.gov (United States)

    van der Male, Pim; van Dalen, Karel N.; Metrikine, Andrei V.

    2016-11-01

    Existing models for the analysis of offshore wind turbines account for the aerodynamic action on the turbine rotor in detail, requiring a high computational price. When considering the foundation of an offshore wind turbine, however, a reduced rotor model may be sufficient. To define such a model, the significance of the nonlinear velocity and history dependency of the aerodynamic force on a rotating blade should be known. Aerodynamic interaction renders the dynamics of a rotating blade in an ambient wind field nonlinear in terms of the dependency on the wind velocity relative to the structural motion. Moreover, the development in time of the aerodynamic force does not follow the flow velocity instantaneously, implying a history dependency. In addition, both the non-uniform blade geometry and the aerodynamic interaction couple the blade motions in and out of the rotational plane. Therefore, this study presents the Euler-Bernoulli formulation of a twisted rotating blade connected to a rigid hub, excited by either instantaneous or history-dependent aerodynamic forces. On this basis, the importance of the history dependency is determined. Moreover, to assess the nonlinear contributions, both models are linearized. The structural response is computed for a stand-still and a rotating blade, based on the NREL 5-MW turbine. To this end, the model is reduced on the basis of its first three free-vibration mode shapes. Blade tip response predictions, computed from turbulent excitation, correctly account for both modal and directional couplings, and the added damping resulting from the dependency of the aerodynamic force on the structural motion. Considering the deflection of the blade tip, the history-dependent and the instantaneous force models perform equally well, providing a basis for the potential use of the instantaneous model for the rotor reduction. The linearized instantaneous model provides similar results for the rotating blade, indicating its potential

  17. Determination of optimum rotational speed of heterogeneous catalytic reactor using computational fluid dynamic

    Directory of Open Access Journals (Sweden)

    Rungrote Kokoo

    2008-09-01

    Full Text Available Solid suspension in a stirrer tank reactor is relevant in many chemical process industries. For a heterogeneous catalyticreactor, the degree of solid suspension is a crucial parameter in the design and scaling-up processes. The suspension of solid catalysts at a minimum impeller speed can reduce the operating cost of processes. To ensure optimum conditions for suspension, a 3D simulation technique by Computational Fluid Dynamic (CFD was used to study flow characteristics in a heterogeneous catalytic reactor. A case study of a 200 milliliter cylindrical reactor was modeled together with equipped parts, i.e. a sampling port, 2 baffles, one thermocouple and a mechanical stirrer. The results show that the total velocity increases from the impeller’s center to the impeller’s tip and decreases from the impeller’s tip to the side wall of the reactor. The vertical velocity at the bottom of the impellers directs flow upward while the velocity at the top directs flow downward. These simulations provide a good preview of solid suspension without doing experiments. It is recommended that the vertical velocity at thebottom of the reactor is in the range between minimum fluidization velocity and terminal velocity to ensure solid suspension inthe system.

  18. Dynamics of forage accumulation in Elephant grass subjected to rotational grazing intensities

    Directory of Open Access Journals (Sweden)

    Braulio Maia de Lana Sousa

    2013-09-01

    Full Text Available We assessed the accumulation dynamics of forage and its components in Elephant grass cv. Napier (Pennisetum purpureum Schum. that were subjected to three post-grazing height treatments (30, 50, and 70 cm from February through May 2009 (experiment one and December 2009 through May 2010 (experiment two. In experiment one, the grazing events started when the light interception by the canopy reached 95%. The same was adopted for experiment two, except for the first grazing event, which was based on the height of the apical meristems of basal tillers. The experimental design for both experiments was a randomized complete block with three replications. The pastures that were managed at a post-grazing height of 30 cm exhibited lower rates of leaf and stem growth, total growth and forage accumulation than those that were managed at 50 or 70 cm, indicating that post-grazing height affects Elephant grass. The pastures that were managed at 50 cm exhibited relatively stable accumulation rates and less stem accumulation. Pastures managed at 70 cm of pos-grazing height presented more leaf and stem accumulation. Most apical meristems of Elephant grass should be removed in the first grazing when they reach the post-grazing target height of 50 cm. The elevation in the residual post-grazing height, especially in the summer, raises the regrowth vigor in the Elephant grass cv. Napier pasture. The post-grazing height of 30 cm reduces the growth of the Elephant grass cv. Napier.

  19. Investigation of the energy barrier to the rotation of amide CN bonds in ACE inhibitors by NMR, dynamic HPLC and DFT.

    Science.gov (United States)

    Bouabdallah, S; Ben Dhia, M T; Driss, M R; Touil, S

    2016-09-01

    The isomerizations of Enalapril, Perindopril, Enalaprilat and Lisinopril have been investigated using NMR spectroscopic, dynamic chromatographic, unified equation and DFT theoretical calculations. The thermodynamic parameters (ΔH, ΔS and ΔG) were determined by varying the temperature in the NMR experiments. At the coalescence temperature, we can evaluate the isomerization barrier to the rotation (ΔG(≠)) around the amide bond. Using dynamics chromatography and an unified equation introduced by Trap, we can determine isomerization rate constants and Gibbs activation energies. Molecular mechanics calculations also provided evidence for the presence of low energy conformers for the ACE due to restricted amide rotation. With the value of barriers (ΔE) between them of the order of (20kJmol(-1)), which is in agreement with the dynamic NMR results and DFT calculations.

  20. Characteristic visuomotor influences on eye-movement patterns to faces and other high level stimuli

    Directory of Open Access Journals (Sweden)

    Joseph Michael Arizpe

    2015-07-01

    Full Text Available Eye-movement patterns are often utilized in studies of visual perception as indices of the specific information extracted to efficiently process a given stimulus during a given task. Our prior work, however, revealed that not only the stimulus and task influence eye-movements, but that visuomotor (start position factors also robustly and characteristically influence eye-movement patterns to faces (Arizpe, et al, 2012. Here we manipulated lateral starting side and distance from the midline of face and line-symmetrical control (butterfly stimuli in order to further investigate the nature and generality of such visuomotor influences. First we found that increasing starting distance from midline (4, 8, 12, 16 degrees visual angle strongly and proportionately increased the distance of the first ordinal fixation from midline. We did not find influences of starting distance on subsequent fixations, however, suggesting that eye-movement plans are not strongly affected by starting distance following an initial orienting fixation. Further, we replicated our prior effect of starting side (left, right to induce a spatially contralateral tendency of fixations after the first ordinal fixation. However, we also established that these visuomotor influences did not depend upon the predictability of the location of the upcoming stimulus, and were present not only for face stimuli but also for our control stimulus category (butterflies. We found a correspondence in overall left-lateralized fixation tendency between faces and butterflies. Finally, for faces, we found a relationship between left starting side (right sided fixation pattern tendency and increased recognition performance, which likely reflects a cortical right hemisphere (left visual hemifield advantage for face perception. These results further indicate the importance of considering and controlling for visuomotor influences in the design, analysis, and interpretation of eye-movement studies.

  1. A STELLA Model to Estimate Water and Nitrogen Dynamics in a Short-Rotation Woody Crop Plantation.

    Science.gov (United States)

    Ouyang, Ying; Zhang, Jiaen; Leininger, Theodor D; Frey, Brent R

    2015-01-01

    Although short-rotation woody crop biomass production technology has demonstrated a promising potential to supply feedstocks for bioenergy production, the water and nutrient processes in the woody crop planation ecosystem are poorly understood. In this study, a computer model was developed to estimate the dynamics of water and nitrogen (N) species (e.g., NH-N, NO-N, particulate organic N, and soluble organic N [SON]) in a woody crop plantation using STELLA (tructural hinking and xperiential earning aboratory with nimation) software. A scenario was performed to estimate diurnal and monthly water and N variations of a 1-ha mature cottonwood plantation over a 1-yr simulation period. A typical monthly variation pattern was found for soil water evaporation, leaf water transpiration, and root water uptake, with an increase from winter to summer and a decrease from summer to the following winter. Simulations further revealed that the rate of soil water evaporation was one order of magnitude lower than that of leaf water transpiration. In most cases, the relative monthly water loss rates could be expressed as evapotranspiration > root uptake > percolation > runoff. Leaching of NO-N and SON depended not only on soil N content but also on rainfall rate and duration. Leaching of NO-N from the cottonwood plantation was about two times higher than that of SON. The relative monthly rate of N leaching was NO-N > SON > NH-N. This study suggests that the STELLA model developed is a useful tool for estimating water and N dynamics from a woody crop plantation.

  2. Carbon pools and temporal dynamics along a rotation period in sessile oak dominated high forest and coppice with standards stands

    Science.gov (United States)

    Bruckman, V. J.; Yan, S.; Hochbichler, E.; Glatzel, G.

    2012-04-01

    Carbon pools in two Quercus petraea (sessile oak) dominated chronosequences under different forest management (high forest and coppice with standards) were investigated. The objective was to study temporal carbon dynamics, in particular carbon sequestration in the soil and woody biomass production, in common forest management systems in eastern Austria along with stand development. The chronosequence approach was used to substitute time-for-space to enable coverage of a full rotation period in each system. Carbon content was determined in the following compartments: aboveground biomass, litter, soil to a depth of 50 cm, living root biomass and decomposing residues in the mineral soil horizons. Biomass carbon pools, except fine roots and residues, were estimated using species-specific allometric functions. Total carbon pools were on average 143 Mg ha-1 in the high forest stand (HF) and 213 Mg ha-1 in the coppice with standards stand (CS). The mean share of the total organic carbon pool (TOC) which is soil organic carbon (SOC) differs only marginally between HF (43.4%) and CS (42.1%), indicating the dominance of site factors, particularly climate, in controlling this ratio. While there was no significant change in O-layer and SOC stores over stand development, we found clear relationships between living biomass (aboveground and belowground) pools and C:N ratio in topsoil horizons with stand age. SOC pools seem to be very stable and an impact of silvicultural interventions was not detected with the applied method. Rapid decomposition and mineralization of litter, indicated by low O-horizon pools with wide C:N ratios of residual woody debris at the end of the vegetation period, suggests high rates of turnover in this fraction. CS, in contrast to HF benefits from rapid resprouting after coppicing and hence seems less vulnerable to conditions of low rainfall and drying topsoil. Keywords: carbon dynamics; soil carbon; chronosequence; Quercus petraea; coppice; high forest

  3. Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task difficulty?

    Directory of Open Access Journals (Sweden)

    Yong Hyun Kwon

    2015-01-01

    Full Text Available Transcranial direct current stimulation (tDCS, an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimulator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels (levels 1, 2, 3 of difficulty with higher level indicating greater difficulty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not significantly increased after real tDCS compared to the sham tDCS. These findings suggest that tasks of moderate difficulty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more difficult tasks.

  4. Is effect of transcranial direct current stimulation on visuomotor coordination dependent on task dififculty?

    Institute of Scientific and Technical Information of China (English)

    Yong Hyun Kwon; Kyung Woo Kang; Sung Min Son; Na Kyung Lee

    2015-01-01

    Transcranial direct current stimulation (tDCS), an emerging technique for non-invasive brain stimulation, is increasingly used to induce changes in cortical excitability and modulate motor behavior, especially for upper limbs. The purpose of this study was to investigate the effects of tDCS of the primary motor cortex on visuomotor coordination based on three levels of task difficulty in healthy subjects. Thirty-eight healthy participants underwent real tDCS or sham tDCS. Using a single-blind, sham-controlled crossover design, tDCS was applied to the primary motor cortex. For real tDCS conditions, tDCS intensity was 1 mA while stimulation was applied for 15 minutes. For the sham tDCS, electrodes were placed in the same position, but the stimu-lator was turned off after 5 seconds. Visuomotor tracking task, consisting of three levels (levels 1, 2, 3) of dififculty with higher level indicating greater dififculty, was performed before and after tDCS application. At level 2, real tDCS of the primary motor cortex improved the accurate index compared to the sham tDCS. However, at levels 1 and 3, the accurate index was not signiifcantly increased after real tDCS compared to the sham tDCS. These ifndings suggest that tasks of mod-erate dififculty may improve visuomotor coordination in healthy subjects when tDCS is applied compared with easier or more dififcult tasks.

  5. BDNF Val66Met Polymorphism Influences Visuomotor Associative Learning and the Sensitivity to Action Observation

    Science.gov (United States)

    Taschereau-Dumouchel, Vincent; Hétu, Sébastien; Michon, Pierre-Emmanuel; Vachon-Presseau, Etienne; Massicotte, Elsa; De Beaumont, Louis; Fecteau, Shirley; Poirier, Judes; Mercier, Catherine; Chagnon, Yvon C.; Jackson, Philip L.

    2016-01-01

    Motor representations in the human mirror neuron system are tuned to respond to specific observed actions. This ability is widely believed to be influenced by genetic factors, but no study has reported a genetic variant affecting this system so far. One possibility is that genetic variants might interact with visuomotor associative learning to configure the system to respond to novel observed actions. In this perspective, we conducted a candidate gene study on the Brain-derived neurotrophic factor (BDNF) Val66Met polymorphism, a genetic variant linked to motor learning in regions of the mirror neuron system, and tested the effect of this polymorphism on motor facilitation and visuomotor associative learning. In a single-pulse TMS study carried on 16 Met (Val/Met and Met/Met) and 16 Val/Val participants selected from a large pool of healthy volunteers, Met participants showed significantly less muscle-specific corticospinal sensitivity during action observation, as well as reduced visuomotor associative learning, compared to Val homozygotes. These results are the first evidence of a genetic variant tuning sensitivity to action observation and bring to light the importance of considering the intricate relation between genetics and associative learning in order to further understand the origin and function of the human mirror neuron system. PMID:27703276

  6. Effects of reactant rotation on the dynamics of the OH + CH4 → H2O + CH3 reaction: A six-dimensional study

    Science.gov (United States)

    Song, Hongwei; Li, Jun; Jiang, Bin; Yang, Minghui; Lu, Yunpeng; Guo, Hua

    2014-02-01

    The dynamics of the hydrogen abstraction reaction between methane and hydroxyl radical is investigated using an initial state selected time-dependent wave packet method within a six-dimensional model. The ab initio calibrated global potential energy surface of Espinosa-García and Corchado was used. Integral cross sections from several low-lying rotational states of both reactants have been obtained using the centrifugal sudden and J-shifting approximations. On the empirical potential energy surface, the rotational excitation of methane has little effect on the reaction cross section, but excited rotational states of OH inhibit the reactivity slightly. These results are rationalized with the newly proposed sudden vector projection model.

  7. Trial-by-Trial Motor Cortical Correlates of a Rapidly Adapting Visuomotor Internal Model.

    Science.gov (United States)

    Stavisky, Sergey D; Kao, Jonathan C; Ryu, Stephen I; Shenoy, Krishna V

    2017-02-15

    Accurate motor control is mediated by internal models of how neural activity generates movement. We examined neural correlates of an adapting internal model of visuomotor gain in motor cortex while two macaques performed a reaching task in which the gain scaling between the hand and a presented cursor was varied. Previous studies of cortical changes during visuomotor adaptation focused on preparatory and perimovement epochs and analyzed trial-averaged neural data. Here, we recorded simultaneous neural population activity using multielectrode arrays and focused our analysis on neural differences in the period before the target appeared. We found that we could estimate the monkey's internal model of the gain using the neural population state during this pretarget epoch. This neural correlate depended on the gain experienced during recent trials and it predicted the speed of the subsequent reach. To explore the utility of this internal model estimate for brain-machine interfaces, we performed an offline analysis showing that it can be used to compensate for upcoming reach extent errors. Together, these results demonstrate that pretarget neural activity in motor cortex reflects the monkey's internal model of visuomotor gain on single trials and can potentially be used to improve neural prostheses.SIGNIFICANCE STATEMENT When generating movement commands, the brain is believed to use internal models of the relationship between neural activity and the body's movement. Visuomotor adaptation tasks have revealed neural correlates of these computations in multiple brain areas during movement preparation and execution. Here, we describe motor cortical changes in a visuomotor gain change task even before a specific movement is cued. We were able to estimate the gain internal model from these pretarget neural correlates and relate it to single-trial behavior. This is an important step toward understanding the sensorimotor system's algorithms for updating its internal models

  8. BASIC THEORY OF RELATIVISTIC BIRKHOFFIAN DYNAMICS OF ROTATIONAL SYSTEM%转动系统相对论性Birkhoff动力学的基本理论

    Institute of Scientific and Technical Information of China (English)

    罗绍凯; 傅景礼; 陈向炜

    2001-01-01

    建立转动系统相对论性Birkhoff动力学的基本理论,给出其Birkhoff函数和Birkhoff函数组、Pfaff作用量、Pfaff-Birkhoff原理、Pfaff-Birkhoff-D'Alembert原理,以及Birkhoff方程。并研究转动系统相对论性Lagrange力学、Hamilton力学与转动系统相对论性Birkhoff动力学之间的关系,证明完整保守、完整非保守转动相对论系统都可纳入转动相对论Birkhoff系统。%The basic theory of relativistic Birkhoffian dynamics of rotational system is constructed, and the Birkhoffian,Birkhoff's functions,Pfaff action,Pfaff-Birkhoff principle,Pfaff-Birkhoff-D' Alembert principle and Birkhoffian equations are given.The relations among relativistic Lagrangian mechanics,Hamiltonian mechanics and relativistic Birkhoffian dynamics of rotational system are studied.It is proved that the holonomic conserved and holonomic non-conserved rotational relativistic systems can all belong to the rotational relativistic Birkhoffian system.

  9. Dynamics of the large-scale circulation in turbulent Rayleigh–Bénard convection with modulated rotation

    NARCIS (Netherlands)

    Zhong, J.Q.; Sterl, S.H.; Li, H.M.

    2015-01-01

    We present measurements of the azimuthal rotation velocity $\\dot{{\\it\\theta}}(t)$θ˙(t) and thermal amplitude ${\\it\\delta}(t)$δ(t) of the large-scale circulation in turbulent Rayleigh–Bénard convection with modulated rotation. Both $\\dot{{\\it\\theta}}(t)$θ˙(t) and ${\\it\\delta}(t)$δ(t) exhibit clear os

  10. A molecular dynamics study of nanoconfined water flow driven by rotating electric fields under realistic experimental conditions

    DEFF Research Database (Denmark)

    De Luca, Sergio; Todd, Billy; Hansen, Jesper Schmidt;

    2014-01-01

    by an external spatially uniform rotating electric field and confined between two planar surfaces exposing different degrees of hydrophobicity. The permanent dipole moment of water follows the rotating field, thus inducing the molecules to spin, and the torque exerted by the field is continuously injected...... into the fluid, enabling a steady conversion of spin angular momentum into linear momentum. The translational–rotational coupling is a sensitive function of the rotating electric field parameters. In this work, we have found that there exists a small energy dissipation region attainable when the frequency...... of the rotating electric field matches the inverse of the dielectric relaxation time of water and when its amplitude lies in a range just before dielectric saturation effects take place. In this region, that is, when the frequency lies in a small window of the microwave region around ∼20 GHz and amplitude ∼0.03 V...

  11. Effects of zonal flows on correlation between energy balance and energy conservation associated with nonlinear nonviscous atmospheric dynamics in a thin rotating spherical shell

    Science.gov (United States)

    Ibragimov, Ranis N.

    2016-12-01

    The nonlinear Euler equations are used to model two-dimensional atmosphere dynamics in a thin rotating spherical shell. The energy balance is deduced on the basis of two classes of functorially independent invariant solutions associated with the model. It it shown that the energy balance is exactly the conservation law for one class of the solutions whereas the second class of invariant solutions provides and asymptotic convergence of the energy balance to the conservation law.

  12. Registration-based filtering: An acceptable tool for noise reduction in left ventricular dynamic rotational angiography images?

    Science.gov (United States)

    Wielandts, Jean-Yves; De Buck, Stijn; Ector, Joris; Nuyens, Dieter; Maes, Frederik; Heidbuchel, Hein

    2014-03-01

    VT ablations could benefit from Dynamic 3D (4D) left ventricle (LV) visualization as road-map for anatomy-guided procedures. We developed a registration-based method that combines information of several cardiac phases to filter out noise and artifacts in low-dose 3D Rotational Angiography (3DRA) images. This also enables generation of accurate multi-phase surface models by semi-automatic segmentation (SAS). The method uses B-spline non-rigid inter-phase registration (IPR) and subsequent averaging of the registered 3DRA images of 4 cardiac phases, acquired with a slow atrial pacing protocol, and was validated on data from 5 porcine experiments. IPR parameter settings were optimized against manual delineations of the LVs using a composed similarity score (Q), dependent on DICE-coefficient, RMSDistance, Hausdorff (HD) and the percentage of inter-surface distances ≤3mm and ≤4mm. The latter are clinically acceptable error cut-off values. Validation was performed after SAS for varying voxel intensity thresholds (ISO), by comparison between models with and without prior use of IPR. Distances to the manual delineations at optimal ISO were reduced to ≤3mm for 95.6±2.7% and to ≤4mm for 97.1±2.0% of model surfaces. Improved quality was proven by significant mean Q-increase irrespective of ISO (7.6% at optimal ISO (95%CI 4.6-10.5,pmodels proved feasible, with sufficient accuracy for clinical applications, opening the perspective of more accurate overlay and guidance during ablation in locations with high degrees of movement.

  13. Discordant tasks and motor adjustments affect interactions between adaptations to altered kinematics and dynamics

    Directory of Open Access Journals (Sweden)

    Fritzie Arce

    2010-01-01

    Full Text Available Motor control and adaptation are multi-determinate processes with complex interactions. This is reflected for example in the ambiguous nature of interactions during sequential adaptation of reaching under kinematics and dynamics perturbations. It has been suggested that perturbations based on the same kinematic parameter interfere. Others posited that opposing motor adjustments underlie interference. Here, we examined the influence of discordances in task and in motor adjustments on sequential adaptations to visuomotor rotation and viscous force field perturbations. These two factors – perturbation direction and task discordance – have been examined separately by previous studies, thus the inherent difficulty to identify the roots of interference. Forty-eight human subjects adapted sequentially to one or two types of perturbations, of matched or conflicting directions. We found a gradient of interaction effects based on perturbation direction and task discordance. Perturbations of matched directions showed facilitation while perturbations of opposite directions, which required opposing motor adjustments, interfered with each other. Further, interaction effects increased with greater task discordance. We also found that force field and visuomotor rotation had mutual anterograde and retrograde effects. However, we found independence between anterograde and retrograde interferences between similar tasks. The results suggest that the newly acquired internal models of kinematic and dynamic perturbations are not independent but they share common neuronal resources and interact between them. Such overlap does not necessarily imply competition of resources. Rather, our results point to an additional principle of sensorimotor adaptation allowing the system to tap or harness common features across diverse sensory inputs and task contexts whenever available.

  14. Effects of retinal position on the visuo-motor adaptation of visual stability in a virtual environment

    Science.gov (United States)

    Kitazaki, Michiteru

    2013-01-01

    Although the retinal image changes a great deal with the movement of our head or eyes, we perceive a stable world (a phenomenon known as visual stability or position constancy). Visual stability adaptively changes for each new combination of vision and head motion, or to compensate for manipulated visuo-motor gain. This study aims to investigate the effects of retinal positions on visuo-motor adaptation and to discuss the neural mechanisms involved. I found that visuo-motor adaptation occurred, and was transferable from right to left visual fields (Experiment 1), between the upper and lower visual fields (Experiment 2), and between the central and peripheral visual fields (Experiment 4), and that for the left visual field (Experiment 1) and the large visual field (Experiment 3) visuo-motor adaptations were effective. The dominance of the central vision was found in Experiment 3 but not found in Experiment 4. These results suggest that the visuo-motor adaptation of visual stability was not specific to the retinal location, but is processed by a relatively high level of the perceptual system. PMID:24349685

  15. Effects of Retinal Position on the Visuo-Motor Adaptation of Visual Stability in a Virtual Environment

    Directory of Open Access Journals (Sweden)

    Michiteru Kitazaki

    2013-06-01

    Full Text Available Although the retinal image changes a great deal with the movement of our head or eyes, we perceive a stable world (a phenomenon known as visual stability or position constancy. Visual stability adaptively changes for each new combination of vision and head motion, or to compensate for manipulated visuo-motor gain. This study aims to investigate the effects of retinal positions on visuo-motor adaptation and to discuss the neural mechanisms involved. I found that visuo-motor adaptation occurred, and was transferable from right to left visual fields (Experiment 1, between the upper and lower visual fields (Experiment 2, and between the central and peripheral visual fields (Experiment 4, and that for the left visual field (Experiment 1 and the large visual field (Experiment 3 visuo-motor adaptations were effective. The dominance of the central vision was found in Experiment 3 but not found in Experiment 4. These results suggest that the visuo-motor adaptation of visual stability was not specific to the retinal location, but is processed by a relatively high level of the perceptual system.

  16. A non-contacting approach for full field dynamic strain monitoring of rotating structures using the photogrammetry, finite element, and modal expansion techniques

    Science.gov (United States)

    Baqersad, Javad

    Health monitoring of rotating structures such as wind turbines and helicopter rotors is generally performed using conventional sensors that provide a limited set of data at discrete locations near or on the hub. These sensors usually provide no data on the blades or interior locations where failures may occur. Within this work, an unique expansion algorithm was extended and combined with finite element (FE) modeling and an optical measurement technique to identify the dynamic strain in rotating structures. The merit of the approach is shown by using the approach to predict the dynamic strain on a small non-rotating and rotating wind turbine. A three-bladed wind turbine having 2.3-meter long blades was placed in a semi-built-in boundary condition using a hub, a machining chuck, and a steel block. A finite element model of the three wind turbine blades assembled to the hub was created and used to extract resonant frequencies and mode shapes. The FE model was validated and updated using experimental modal tests. For the non-rotating optical test, the turbine was excited using a sinusoidal excitation, a pluck test, arbitrary impacts on three blades, and random force excitations with a mechanical shaker. The response of the structure to the excitations was measured using three-dimensional point tracking. A pair of high-speed cameras was used to measure the displacement of optical targets on the structure when the blades were vibrating. The measured displacements at discrete locations were expanded and applied to the finite element model of the structure to extract the full-field dynamic strain. The results of the work show an excellent correlation between the strain predicted using the proposed approach and the strain measured with strain-gages for all of the three loading conditions. Similar to the non-rotating case, optical measurements were also preformed on a rotating wind turbine. The point tracking technique measured both rigid body displacement and flexible

  17. Difference rather than delay in development of elementary visuomotor processes in children born preterm without Celebral Palsy : A quasi-longitudinal study

    NARCIS (Netherlands)

    Van Braeckel, K.N.J.A.; Butcher, P.R.; Geuze, R.H.; van Duijn, M.A.J.; Bos, Arie; Bouma, Anke

    Follow-up studies of preterm children without serious neonatal medical complications have consistently found poor visuomotor and visuospatial skills. In the first round of current follow-up study, we found a deficit in elementary visuomotor processes in preterm children without Cerebral Palsy (CP).

  18. Comparative study of dynamic structure of pig and chicken aspartate aminotransferases by measuring the rotational correlation time.

    Science.gov (United States)

    Timofeev, V P; Dudich, I V; Volkenstein, M V

    1980-01-01

    The rotational correlation time of two homologous cytoplasmic aspartate aminotransferase molecules isolated from pig and chicken hearts was obtained by spin-labeling technique. The maleimide and iodoacetamide spin-labels modifying external SH-groups of a protein were used. In the interpretation of ESR spectra a rotational motion of nitroxide group relative to the protein molecule was taken into account. To determine the macromolecule rotational correlation time two methods of the immobilization of a protein molecule were used: 1) by means of increasing protein solution viscosity and 2) by fixation of the protein molecule on adsorbent. From comparison of experimental and theoretical values of rotational correlation time it was conclude that the both enzymes exhibits an intramolecular flexibility.

  19. Exoplanet dynamics. Asynchronous rotation of Earth-mass planets in the habitable zone of lower-mass stars.

    Science.gov (United States)

    Leconte, Jérémy; Wu, Hanbo; Menou, Kristen; Murray, Norman

    2015-02-06

    Planets in the habitable zone of lower-mass stars are often assumed to be in a state of tidally synchronized rotation, which would considerably affect their putative habitability. Although thermal tides cause Venus to rotate retrogradely, simple scaling arguments tend to attribute this peculiarity to the massive Venusian atmosphere. Using a global climate model, we show that even a relatively thin atmosphere can drive terrestrial planets' rotation away from synchronicity. We derive a more realistic atmospheric tide model that predicts four asynchronous equilibrium spin states, two being stable, when the amplitude of the thermal tide exceeds a threshold that is met for habitable Earth-like planets with a 1-bar atmosphere around stars more massive than ~0.5 to 0.7 solar mass. Thus, many recently discovered terrestrial planets could exhibit asynchronous spin-orbit rotation, even with a thin atmosphere.

  20. IMMEDIATE EFFECTS OF A DYNAMIC ROTATION-SPECIFIC WARM-UP ON X-FACTOR AND X-FACTOR STRETCH IN THE AMATEUR GOLFER.

    Science.gov (United States)

    Henry, Elizabeth; Berglund, Kathy; Millar, Lynn; Locke, Frederick

    2015-12-01

    Recent evidence suggests performing a warm-up prior to golf can improve performance and reduce injuries. While some characteristics of effective golf warm-ups have been determined, no studies have explored the immediate effects of a rotational-specific warm-up with elements of motor control on the biomechanical aspects of the full X-Factor and X-Factor Stretch during the golf swing. Thirty-six amateur golfers (mean ± SD age: 64 ± 8 years old; 75% male) were randomized into a Dynamic Rotation-Specific Warm-up group (n=20), or a Sham Warm-up group (n=16). X-Factor and X-Factor Stretch were measured at baseline and immediately following the warm-up. Mixed model ANCOVAs were used to determine if a Group*Time interaction existed for each variable with group as the between-subjects variable and time as the within-subjects variable. The mixed model ANCOVAs did not reveal a statistically significant group*time interaction for X-Factor or X-Factor Stretch. There was not a significant main effect for time for X-Factor but there was for X-Factor Stretch. These results indicate that neither group had a significant effect on improving X-Factor, however performing either warm-up increased X-Factor Stretch without significant difference between the two. The results of this study suggest that performing the Dynamic Rotation-Specific Warm-up did not increase X-Factor or X-Factor Stretch when controlled for age compared to the Sham Warm-up. Further study is needed to determine the long-term effects of the Dynamic Rotation-Specific Warm-up on performance factors of the golf swing while examining across all ages. 2b.

  1. Dependence of the L- to H-mode Power Threshold on Toroidal Rotation and the Link to Edge Turbulence Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    McKee, G; Gohil, P; Schlossberg, D; Boedo, J; Burrell, K; deGrassie, J; Groebner, R; Makowski, M; Moyer, R; Petty, C; Rhodes, T; Schmitz, L; Shafer, M; Solomon, W; Umansky, M; Wang, G; White, A; Xu, X

    2008-10-13

    The injected power required to induce a transition from L-mode to H-mode plasmas is found to depend strongly on the injected neutral beam torque and consequent plasma toroidal rotation. Edge turbulence and flows, measured near the outboard midplane of the plasma (0.85 < r/a < 1.0) on DIII-D with the high-sensitivity 2D beam emission spectroscopy (BES) system, likewise vary with rotation and suggest a causative connection. The L-H power threshold in plasmas with the ion {del}B drift away from the X-point decreases from 4-6 MW with co-current beam injection, to 2-3 MW with near zero net injected torque, and to <2 MW with counter injection. Plasmas with the ion {del}B drift towards the X-point exhibit a qualitatively similar though less pronounced power threshold dependence on rotation. 2D edge turbulence measurements with BES show an increasing poloidal flow shear as the L-H transition is approached in all conditions. At low rotation, the poloidal flow of turbulent eddies near the edge reverses prior to the L-H transition, generating a significant poloidal flow shear that exceeds the measured turbulence decorrelation rate. This increased poloidal turbulence velocity shear may facilitate the L-H transition. No such reversal is observed in high rotation plasmas. The poloidal turbulence velocity spectrum exhibits a transition from a Geodesic Acoustic Mode zonal flow to a higher-power, lower frequency, zero-mean-frequency zonal flow as rotation varies from co-current to balanced during a torque scan at constant injected neutral beam power, perhaps also facilitating the L-H transition. This reduced power threshold at lower toroidal rotation may benefit inherently low-rotation plasmas such as ITER.

  2. Visuomotor competencies and primary monosymptomatic nocturnal enuresis in prepubertal aged children.

    Science.gov (United States)

    Esposito, Maria; Gallai, Beatrice; Parisi, Lucia; Roccella, Michele; Marotta, Rosa; Lavano, Serena Marianna; Mazzotta, Giovanni; Patriciello, Giuseppina; Precenzano, Francesco; Carotenuto, Marco

    2013-01-01

    Primary monosymptomatic nocturnal enuresis (PMNE) is a common problem in the developmental ages; it is the involuntary loss of urine during the night in children older than 5 years of age. Several clinical observations have suggested an association between bedwetting and developmental delays in motricity, language development, learning disability, physical growth, and skeletal maturation. The aim of the present study is to evaluate the prevalence of fine motor coordination and visuomotor integration abnormalities in prepubertal children with PMNE. The study population included 31 children (16 males, 15 females; mean age 8.14 years ± 1.36 years), and the control group comprised 61 typical developing children (32 males, 29 females; mean age 8.03 years ± 1.44 years). The whole population underwent a clinical evaluation to assess total intelligence quotient level, visuomotor integration (VMI) skills, and motor coordination performance (using the Movement Assessment Battery for Children, or M-ABC). No significant differences between the two study groups were found for age (P = 0.725), gender (P = 0.886), z-body mass index (P = 0.149), or intellectual abilities (total intelligence quotient) (P = 0.163). The PMNE group showed a higher prevalence of borderline performance on M-ABC evaluation and in pathologic performance on VMI Total Task compared to controls (P VMI Visual Task (P = 0.793), and VMI Motor Task (P = 0.213). Our findings pinpointed that PMNE should not be considered as a voiding disorder alone and, consequently, the children affected should be referred to specific rehabilitative programs that aim to improve motor coordination and visuomotor integration.

  3. Descending projections of the hamster intergeniculate leaflet: relationship to the sleep/arousal and visuomotor systems

    Science.gov (United States)

    Morin, Lawrence P.; Blanchard, Jane H.

    2005-01-01

    The intergeniculate leaflet (IGL), homolog of the primate pregeniculate nucleus, modulates circadian rhythms. However, its extensive anatomical connections suggest that it may regulate other systems, particularly those for visuomotor function and sleep/arousal. Here, descending IGL-efferent pathways are identified with the anterograde tracer, Phaseolus vulgaris leucoagglutinin, with projections to over 50 brain stem nuclei. Projections of the ventral lateral geniculate are similar, but more limited. Many of the nuclei with IGL afferents contribute to circuitry governing visuomotor function. These include the oculomotor, trochlear, anterior pretectal, Edinger-Westphal, and the terminal nuclei; all layers of the superior colliculus, interstitial nucleus of the medial longitudinal fasciculus, supraoculomotor periaqueductal gray, nucleus of the optic tract, the inferior olive, and raphe interpositus. Other target nuclei are known to be involved in the regulation of sleep, including the lateral dorsal and pedunculopontine tegmentum. The dorsal raphe also receives projections from the IGL and may contribute to both sleep/arousal and visuomotor function. However, the locus coeruleus and medial vestibular nucleus, which contribute to sleep and eye movement regulation and which send projections to the IGL, do not receive reciprocal projections from it. The potential involvement of the IGL with the sleep/arousal system is further buttressed by existing evidence showing IGL-efferent projections to the ventrolateral preoptic area, dorsomedial, and medial tuberal hypothalamus. In addition, the great majority of all regions receiving IGL projections also receive input from the orexin/hypocretin system, suggesting that this system contributes not only to the regulation of sleep, but to eye movement control as well.

  4. Single- vs. double-bundle anterior cruciate ligament reconstruction: a new aspect of knee assessment during activities involving dynamic knee rotation.

    Science.gov (United States)

    Czamara, Andrzej; Królikowska, Aleksandra; Szuba, Łukasz; Widuchowski, Wojciech; Kentel, Maciej

    2015-02-01

    Few studies have compared single-bundle (SB) and double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) in the knee joint during activities involving change-of-direction maneuvers and knee rotation. This study examined whether the type of ACLR contributes to postphysiotherapy outcomes, with an emphasis on knee function assessment during activities involving dynamic knee rotation. Fifteen male patients after SB ACLR and 15 male patients after DB ACLR took part in the same physiotherapy program. Twenty-four weeks after ACLR, both groups underwent anterior laxity measurement, pivot shift tests, range of movement and joint circumference measurements, subjective assessment of pain and stability levels in the knee joint, peak torque measurement of the muscles rotating the tibia toward the femur, and a run test with maximal speed and change-of-direction maneuvers. Comparative analysis did not show any differences between the results of anterior tibial translation, pivot shift test, range of movement and joint circumference, and subjective assessment of pain and knee joint stability levels. No differences were noted between the groups in peak torque values obtained from the muscles responsible for internal and external tibial rotation or results of the run test. The data obtained from this study can be used by research teams to monitor and compare the effectiveness of various study protocols involving surgical and physiotherapy treatment. The data are especially useful when combined with the clinical assessment of patients who would like to return to sport.

  5. Implementation of dynamic crop growth processes into a land surface model: evaluation of energy, water and carbon fluxes under corn and soybean rotation

    Directory of Open Access Journals (Sweden)

    Y. Song

    2013-06-01

    Full Text Available Worldwide expansion of agriculture is impacting Earth's climate by altering the carbon, water and energy fluxes, but climate in turn is impacting crop production. To study this two-way interaction and its impact on seasonal dynamics of carbon, water and energy fluxes, we implemented dynamic crop growth processes into a land surface model, the Integrated Science Assessment Model (ISAM. In particular, we implement crop specific phenology schemes, which account for light, water, and nutrient stresses while allocating the assimilated carbon to leaf, root, stem and grain pools; dynamic vegetation structure growth, which better simulate the LAI and canopy height; dynamic root distribution processes in the soil layers, which better simulate the root response of soil water uptake and transpiration; and litter fall due to fresh and old dead leaves to better represent the water and energy interception by both stem and brown leaves of the canopy during leaf senescence. Observational data for LAI, above and below ground biomass, and carbon, water and energy fluxes were compiled from two Ameri-Flux sites, Mead, NE and Bondville, IL, to calibrate and evaluate the model performance under corn (C4-soybean (C3 rotation system over the period 2001–2004. The calibrated model was able to capture the diurnal and seasonal patterns of carbon assimilation, water and energy fluxes under the corn-soybean rotation system at these two sites. Specifically, the calculated GPP, net radiation fluxes at the top of canopy and latent heat fluxes compared well with observations. The largest bias in model results is in sensible heat flux (H for corn and soybean at both sites. With dynamic carbon allocation and root distribution processes, model simulated GPP and latent heat flux (LH were in much better agreement with observation data than for the without dynamic case. Modeled latent heat improved by 12–27% during the growing season at both sites, leading to the improvement in

  6. Age-related differences in control of a visuomotor coordination task: a preliminary study

    OpenAIRE

    2016-01-01

    [Purpose] The purpose of the current study was to examine age-related differences in control of a perception-action coordination skill. We adapted a visuomotor tracking experiment requiring various coordination patterns between a limb’s motion and an external signal. [Subjects and Methods] A total of 12 subjects (6 elderly and 6 young) voluntarily participated in the study. The experimental session consisted of 3 trials for 3 different relative phase patterns: 0°, 90°, and 180°, defined by th...

  7. Visuomotor competencies and primary monosymptomatic nocturnal enuresis in prepubertal aged children

    Directory of Open Access Journals (Sweden)

    Esposito M

    2013-06-01

    Full Text Available Maria Esposito,1 Beatrice Gallai,2 Lucia Parisi,3 Michele Roccella,3 Rosa Marotta,4 Serena Marianna Lavano,4 Giovanni Mazzotta,5 Giuseppina Patriciello,1 Francesco Precenzano,1 Marco Carotenuto1 1Clinic of Child and Adolescent Neuropsychiatry, Department of Mental Health, Physical and Preventive Medicine, Second University of Naples, Italy; 2Unit of Child and Adolescent Neuropsychiatry, University of Perugia, Italy; 3Child Neuropsychiatry, Department of Psychology, University of Palermo, Italy; 4Department of Psychiatry, "Magna Graecia" University of Catanzaro, Catanzaro, Italy; 5Unit of Child and Adolescent Neuropsychiatry, AUSL Umbria 2, Terni, Italy Background: Primary monosymptomatic nocturnal enuresis (PMNE is a common problem in the developmental ages; it is the involuntary loss of urine during the night in children older than 5 years of age. Several clinical observations have suggested an association between bedwetting and developmental delays in motricity, language development, learning disability, physical growth, and skeletal maturation. The aim of the present study is to evaluate the prevalence of fine motor coordination and visuomotor integration abnormalities in prepubertal children with PMNE. Methods: The study population included 31 children (16 males, 15 females; mean age 8.14 years ± 1.36 years, and the control group comprised 61 typical developing children (32 males, 29 females; mean age 8.03 years ± 1.44 years. The whole population underwent a clinical evaluation to assess total intelligence quotient level, visuomotor integration (VMI skills, and motor coordination performance (using the Movement Assessment Battery for Children, or M-ABC. Results: No significant differences between the two study groups were found for age (P = 0.725, gender (P = 0.886, z-body mass index (P = 0.149, or intellectual abilities (total intelligence quotient (P = 0.163. The PMNE group showed a higher prevalence of borderline performance on M

  8. Population Dynamics and Survival of Rhizoctonia solani AG-1 in Field Soil Under Rice-Wheat Rotation

    Institute of Scientific and Technical Information of China (English)

    LI Shi-dong

    2004-01-01

    A field under rice-wheat rotation was selected near Chengdu, China, to study the population of Rhizoctonia solani anastomosis group 1 (AG-l), pathogen causing rice sheath blight disease, in natural soil ecosystem. Inocula of the fungus recovered from the field were divided into three types, i.e., sclerotia, free mycelium retained in the soil passed through a 0.355mm sieve, and colonized plant debris which was subdivided into small colonized debris retained between 2.00 and 0.355mm sieves and large colonized debris retained on 2.00mm sieve after wet screening. Quantitative estimation of the three types of inocula in one year indicated that small colonized debris was the dominant inoculum type for most of the time. The population peaked in March and September at 1 210and 480 colonized debris 100 g-1 air-dry soil respectively, and fell down in December and August to 0 and 177 colonized debris 100 g-1 air-dry soil respectively. Free mycelium was only detectable in March, September and October with 1 209, 7.9 and 14.5 μg fresh wt myceliumg-1 air-dry soil respectively, which corresponded to the two peaks and the second highest level of small debris density in the year. Viable sclerotia and large colonized debris were rare with populations ranging from 0 to 3 for sclerotia and 0 to 14 for large colonized debris 100 g-1 air-dry soil, but were the main structures to survive over winter. It was expected that soil temperature was the main factor determining population dynamics of R.solani AG-1 in natural soil. Optimum temperature for population increasing is predicted to be around 15℃, with a range from 10 to 25℃. Viability tests indicated that 60.9% sclerotia could survive after 265 d being buried in natural sandy loam in field conditions in Beijing, while colonized rice straw debris (0.5 - 1.0 cm long) could not yield the fungus on medium plates after 88d of being buried under the same conditions.

  9. Justification for parameters of a dynamic stabilizer of the experimental stand mobile unit in studying of active rotational working tools of tiller machines

    Directory of Open Access Journals (Sweden)

    Vladimir F. Kupryashkin

    2017-03-01

    Full Text Available Introduction: The article deals with design options and technological modes of the dynamic stabilizer of the experimental stand mobile unit for studying tillage machine active rotating work tools. Based on theoretical and experimental studies, the possibility the movable module instability was discovered. This negatively affects on implementing the experiment program trough the especific method. The need in engineering solutions for the defect correction is shown. In addition, the authors consider the structural features and characteristics of the used devices for providing the stabilization of the movable module in the study of active rotating work tools of tillage machines. An electromagnetic brake dynamic stabilizer in the structure of the existing rolling module was proposed as an engineering device. Materials and Methods: A theoretical study of rolling module stability, based on synthesis of basic regulations and laws of mechanics related to active rotating work tools was conducted. As a result of the theoretical research, a design scheme of movable module loading was created. This scheme includes the design features and structural power factors. Results: A database representing the settings of power specification in the motion stability determining the mobile unit was created. Further use of the database values allow supporting the most optimal location of the electromagnetic brake with its design options. Discussion and Conclusions: The research of the electromagnetic brake in a mobile unit promoted stabilizing the unit movement, increased the frequency of its use and provided data that are more precise during experiments.

  10. A discrete chemo-dynamical model of the giant elliptical galaxy NGC 5846: dark matter fraction, internal rotation and velocity anisotropy out to six effective radii

    CERN Document Server

    Zhu, Ling; van de Ven, Glenn; Long, R J; Watkins, Laura L; Pota, Vincenzo; Napolitano, Nicola R; Forbes, Duncan A; Brodie, Jean; Foster, Caroline

    2016-01-01

    We construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy NGC 5846. These models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. We use Jeans models to simultaneously fit stellar kinematics within the effective radius $R_{\\rm e}$, planetary nebula (PN) radial velocities out to $3\\, R_{\\rm e}$, and globular cluster (GC) radial velocities and colours out to $6\\,R_{\\rm e}$. The best-fitting model is a cored DM halo which contributes $\\sim 10\\%$ of the total mass within $1\\,R_{\\rm e}$, and $67\\% \\pm 10\\%$ within $6\\,R_{\\rm e}$, although a cusped DM halo is also acceptable. The red GCs exhibit mild rotation with $v_{\\rm max}/\\sigma_0 \\sim 0.3$ in the region $R > \\,R_{\\rm e}$, aligned with but counter-rotating to the stars in the inner parts, while the blue GCs and PNe kinematics are consistent with no rotation. The red GCs are tangentially anisotropic, the blue GCs are mildly radially anisotropic, and the PNe vary from r...

  11. A discrete chemo-dynamical model of the giant elliptical galaxy NGC 5846: dark matter fraction, internal rotation, and velocity anisotropy out to six effective radii

    Science.gov (United States)

    Zhu, Ling; Romanowsky, Aaron J.; van de Ven, Glenn; Long, R. J.; Watkins, Laura L.; Pota, Vincenzo; Napolitano, Nicola R.; Forbes, Duncan A.; Brodie, Jean; Foster, Caroline

    2016-11-01

    We construct a suite of discrete chemo-dynamical models of the giant elliptical galaxy NGC 5846. These models are a powerful tool to constrain both the mass distribution and internal dynamics of multiple tracer populations. We use Jeans models to simultaneously fit stellar kinematics within the effective radius Re, planetary nebula (PN) radial velocities out to 3 Re, and globular cluster (GC) radial velocities and colours out to 6 Re. The best-fitting model is a cored dark matter halo which contributes ˜10 per cent of the total mass within 1 Re, and 67 per cent ± 10 per cent within 6 Re, although a cusped dark matter halo is also acceptable. The red GCs exhibit mild rotation with vmax/σ0 ˜ 0.3 in the region R > Re, aligned with but counter-rotating to the stars in the inner parts, while the blue GCs and PNe kinematics are consistent with no rotation. The red GCs are tangentially anisotropic, the blue GCs are mildly radially anisotropic, and the PNe vary from radially to tangentially anisotropic from the inner to the outer region. This is confirmed by general made-to-measure models. The tangential anisotropy of the red GCs in the inner regions could stem from the preferential destruction of red GCs on more radial orbits, while their outer tangential anisotropy - similar to the PNe in this region - has no good explanation. The mild radial anisotropy of the blue GCs is consistent with an accretion scenario.

  12. A robust and efficient numerical method to compute the dynamics of the rotating two-component dipolar Bose-Einstein condensates

    CERN Document Server

    Tang, Qinglin; Mauser, Norbert

    2016-01-01

    In this paper, we propose a robust and efficient numerical method to compute the dynamics of the rotating two-component dipolar Bose-Einstein condensates (BEC). Using the rotating Lagrangian coordinates transform \\cite{BMTZ2013}, we reformulate the original coupled Gross-Pitaevskii equations (CGPE) into new equations where the rotating term vanishes and the potential becomes time-dependent. A time-splitting Fourier pseudospectral method is proposed to simulate the new equations where the nonlocal Dipole-Dipole Interactions (DDI) are computed by a newly-developed Gaussian-sum (GauSum) solver \\cite{EMZ2015} which helps achieve spectral accuracy in space within $O(N\\log N)$ operations ($N$ is the total number of grid points). The new method is spectrally accurate in space and second order accurate in time, and the accuracies are confirmed numerically. Dynamical properties of some physical quantities, including the total mass, energy, center of mass and angular momentum expectation, are presented and confirmed nu...

  13. Galaxy cluster's rotation

    CERN Document Server

    Manolopoulou, Maria

    2016-01-01

    We study the possible rotation of cluster galaxies, developing, testing and applying a novel algorithm which identifies rotation, if such does exits, as well as its rotational centre, its axis orientation, rotational velocity amplitude and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte-Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z<~0.1 with member galaxies selected from the SDSS DR10 spectroscopic database. We find that ~35% of our clusters are rotating when using a set of strict criteria, while loosening the criteria we find this fraction increasing to ~48%. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation that the significance and strength of their...

  14. Presynaptic control of group Ia afferents in relation to acquisition of a visuo-motor skill in healthy humans

    DEFF Research Database (Denmark)

    Perez, Monica A.; Lungholt, Bjarke K.S.; Nielsen, Jens Bo

    2005-01-01

    , a novel visuo-motor task involving the ankle muscles, and a control task involving simple voluntary ankle movements, would induce changes in the size of the soleus H-reflex. The slope of the H-reflex recruitment curve and the H-max/M-max ratio were depressed after repetition of the visuo-motor skill task...... and returned to baseline after 10 min. No changes were observed after the control task. To elucidate the mechanisms contributing to the H-reflex depression, we measured the size of the long-latency depression of the soleus H-reflex evoked by peroneal nerve stimulation (D1 inhibition) and the size...

  15. 同心球间旋转流动Lorenz系统的动力学行为及仿真%THE DYNAMICAL BEHAVIOR AND THE SIMULATION OF THE LORENZ SYSTEM OF THE FLOW BETWEEN TWO CONCENTRIC ROTATING SPHERES

    Institute of Scientific and Technical Information of China (English)

    王贺元

    2012-01-01

    To discuss the dynamical behavior of the flow between two concentric rotating spheres we study the dynamical behavior and the numerical simulation of the model system similar to the Lorenz equations of the Navier-Stokes equations for the flow between two concentric rotating spheres. Its stationary points and the stability are presented, the existence of attractor is proved, and the global stability of the system is discussed. Chaos behavior is simulated numerically by computer with the changing of Reynolds number.

  16. Electron spin dynamics of Ce3 + ions in YAG crystals studied by pulse-EPR and pump-probe Faraday rotation

    Science.gov (United States)

    Azamat, D. V.; Belykh, V. V.; Yakovlev, D. R.; Fobbe, F.; Feng, D. H.; Evers, E.; Jastrabik, L.; Dejneka, A.; Bayer, M.

    2017-08-01

    The spin relaxation dynamics of Ce3 + ions in heavily cerium-doped YAG crystals is studied using pulse-electron paramagnetic resonance and time-resolved pump-probe Faraday rotation. Both techniques address the 4 f ground state, while pump-probe Faraday rotation also provides access to the excited 5 d state. We measure a millisecond spin-lattice relaxation time T1, a microsecond spin coherence time T2, and a ˜10 ns inhomogeneous spin dephasing time T2* for the Ce3 + ground state at low temperatures. The spin-lattice relaxation of Ce3 + ions is due to modified Raman processes involving the optical phonon mode at ˜125 cm-1 . The relaxation at higher temperature goes through a first excited level of the 5/2 2F term at about ℏ ω ≈228 cm-1 . Effects provided by the hyperfine interaction of the Ce3 + with the 27Al nuclei are observed.

  17. Amplification of azimuthal modes with odd wave numbers during dynamical bar-mode growth in rotating stars

    CERN Document Server

    Kojima, Yasufumi

    2008-01-01

    Nonlinear growth of the bar-mode deformation is studied for a differentially rotating star with supercritical rotational energy. In particular, the growth mechanism of some azimuthal modes with odd wave numbers is examined by comparing a simplified mathematical model with a realistic simulation. Mode coupling to even modes, i.e., the bar mode and higher harmonics, significantly enhances the amplitudes of odd modes, unless they are exactly zero initially. Therefore, other modes which are not axially symmetric cannot be neglected at late times in the growth of the unstable bar-mode even when starting from an almost axially symmetric state.

  18. Change of caged dynamics at Tg in hydrated proteins: Trend of mean squared displacements after correcting for the methyl-group rotation contribution

    Science.gov (United States)

    Ngai, K. L.; Capaccioli, S.; Paciaroni, A.

    2013-06-01

    The question whether the dynamics of hydrated proteins changes with temperature on crossing the glass transition temperature like that found in conventional glassformers is an interesting one. Recently, we have shown that a change of temperature dependence of the mean square displacement (MSD) at Tg is present in proteins solvated with bioprotectants, such as sugars or glycerol with or without the addition of water, coexisting with the dynamic transition at a higher temperature Td. The dynamical change at Tg is similar to that in conventional glassformers at sufficiently short times and low enough temperatures, where molecules are mutually caged by the intermolecular potential. This is a general and fundamental property of glassformers which is always observed at or near Tg independent of the energy resolution of the spectrometer, and is also the basis of the dynamical change of solvated proteins at Tg. When proteins are solvated with bioprotectants they show higher Tg and Td than the proteins hydrated by water alone, due to the stabilizing action of excipients, thus the observation of the change of T-dependence of the MSD at Tg is unobstructed by the methyl-group rotation contribution at lower temperatures [S. Capaccioli, K. L. Ngai, S. Ancherbak, and A. Paciaroni, J. Phys. Chem. B 116, 1745 (2012)], 10.1021/jp2057892. On the other hand, in the case of proteins hydrated by water alone unambiguous evidence of the break at Tg is hard to find, because of their lower Tg and Td. Notwithstanding, in this paper, we provide evidence for the change at Tg of the T-dependence of proteins hydrated by pure water. This evidence turns out from (i) neutron scattering experimental investigations where the sample has been manipulated by either full or partial deuteration to suppress the methyl-group rotation contribution, and (ii) neutron scattering experimental investigations where the energy resolution is such that only motions with characteristic times shorter than 15 ps can be

  19. Developing a new experimental system for an undergraduate laboratory exercise to teach theories of visuomotor learning.

    Science.gov (United States)

    Kasuga, Shoko; Ushiba, Junichi

    2014-01-01

    Humans have a flexible motor ability to adapt their movements to changes in the internal/external environment. For example, using arm-reaching tasks, a number of studies experimentally showed that participants adapt to a novel visuomotor environment. These results helped develop computational models of motor learning implemented in the central nervous system. Despite the importance of such experimental paradigms for exploring the mechanisms of motor learning, because of the cost and preparation time, most students are unable to participate in such experiments. Therefore, in the current study, to help students better understand motor learning theories, we developed a simple finger-reaching experimental system using commonly used laptop PC components with an open-source programming language (Processing Motor Learning Toolkit: PMLT). We found that compared to a commercially available robotic arm-reaching device, our PMLT accomplished similar learning goals (difference in the error reduction between the devices, P = 0.10). In addition, consistent with previous reports from visuomotor learning studies, the participants showed after-effects indicating an adaptation of the motor learning system. The results suggest that PMLT can serve as a new experimental system for an undergraduate laboratory exercise of motor learning theories with minimal time and cost for instructors.

  20. Enhanced visuomotor processing of phobic images in blood-injury-injection fear.

    Science.gov (United States)

    Haberkamp, Anke; Schmidt, Thomas

    2014-04-01

    Numerous studies have identified attentional biases and processing enhancements for fear-relevant stimuli in individuals with specific phobias. However, this has not been conclusively shown in blood-injury-injection (BII) phobia, which has rarely been investigated even though it has features distinct from all other specific phobias. The present study aims to fill that gap and compares the time-course of visuomotor processing of phobic stimuli (i.e., pictures of small injuries) in BII-fearful (n=19) and non-anxious control participants (n=23) by using a response priming paradigm. In BII-fearful participants, phobic stimuli produced larger priming effects and lower response times compared to neutral stimuli, whereas non-anxious control participants showed no such differences. Because these effects are fully present in the fastest responses, they indicate an enhancement in early visuomotor processing of injury pictures in BII-fearful participants. These results are comparable to the enhanced processing of phobic stimuli in other specific phobias (i.e., spider phobia). Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. Emotion processing fails to modulate putative mirror neuron response to trained visuomotor associations.

    Science.gov (United States)

    Fitzgibbon, Bernadette M; Kirkovski, Melissa; Fornito, Alex; Paton, Bryan; Fitzgerald, Paul B; Enticott, Peter G

    2016-04-01

    Recent neuroimaging studies have demonstrated that activation of the putative human mirror neuron system (MNS) can be elicited via visuomotor training. This is generally interpreted as supporting an associative learning account of the mirror neuron system (MNS) that argues against the ontogeny of the MNS to be an evolutionary adaptation for social cognition. The current study assessed whether a central component of social cognition, emotion processing, would influence the MNS activity to trained visuomotor associations, which could support a broader role of the MNS in social cognition. Using functional magnetic resonance imaging (fMRI), we assessed repetition suppression to the presentation of stimulus pairs involving a simple hand action and a geometric shape that was either congruent or incongruent with earlier association training. Each pair was preceded by an image of positive, negative, or neutral emotionality. In support of an associative learning account of the MNS, repetition suppression was greater for trained pairs compared with untrained pairs in several regions, primarily supplementary motor area (SMA) and right inferior frontal gyrus (rIFG). This response, however, was not modulated by the valence of the emotional images. These findings argue against a fundamental role of emotion processing in the mirror neuron response, and are inconsistent with theoretical accounts linking mirror neurons to social cognition. Copyright © 2016 Elsevier Ltd. All rights reserved.

  2. Time- but not sleep-dependent consolidation of tDCS-enhanced visuomotor skills.

    Science.gov (United States)

    Reis, Janine; Fischer, Jan Torben; Prichard, George; Weiller, Cornelius; Cohen, Leonardo G; Fritsch, Brita

    2015-01-01

    Consolidation of motor skills after training can occur in a time- or sleep-dependent fashion. Recent studies revealed time-dependent consolidation as a common feature of visuomotor tasks. We have previously shown that anodal transcranial direct current stimulation (tDCS) in combination with repeated motor training benefits consolidation by the induction of offline skill gains in a complex visuomotor task, preventing the regular occurrence of skill loss between days. Here, we asked 2 questions: What is the time course of consolidation between days for this task and do exogenously induced offline gains develop as a function of time or overnight sleep? We found that both the development of offline skill loss in sham-stimulated subjects and offline skill gains induced by anodal tDCS critically depend on the passage of time after training, but not on overnight sleep. These findings support the view that tDCS interacts directly with the physiological consolidation process. However, in a control experiment, anodal tDCS applied after the training did not induce skill gains, implying that coapplication of tDCS and training is required to induce offline skill gains, pointing to the initiation of consolidation already during training.

  3. To lead and to lag - forward and backward recalibration of perceived visuo-motor simultaneity

    Directory of Open Access Journals (Sweden)

    Marieke eRohde

    2013-01-01

    Full Text Available Studies on human recalibration of perceived visuo-motor simultaneity so far have been limited to the study of recalibration to movement-lead temporal discrepancies (visual lags. We studied adaptation to both vision-lead and movement-lead discrepancies, to test for differences between these conditions, as a leading visual stimulus violates the underlying cause-effect structure. To this end, we manipulated the temporal relationship between a motor action (button press and a visual event (flashed disk in a training phase. Participants were tested in a temporal order judgment task and perceived simultaneity (PSS was compared before and after recalibration. A PHANToM© force-feedback device that tracks the finger position in real time was used to display a virtual button. We predicted the timing of full compression of the button from early movement onset in order to time visual stimuli even before the movement event of the full button press. The results show that recalibration of perceived visuo-motor simultaneity is evident in both directions and does not differ in magnitude between the conditions. The strength of recalibration decreases with perceptual accuracy, suggesting the possibility that some participants recalibrate less because they detect the discrepancy. We conclude that the mechanisms of temporal recalibration work in both direction and there is no evidence that they are asymmetrical around the point of actual simultaneity, despite the underlying asymmetry in the cause-effect relation.

  4. Close interpersonal proximity modulates visuomotor processing of object affordances in shared, social space.

    Science.gov (United States)

    Saccone, Elizabeth J; Szpak, Ancret; Churches, Owen; Nicholls, Michael E R

    2017-09-01

    Research suggests that the human brain codes manipulable objects as possibilities for action, or affordances, particularly objects close to the body. Near-body space is not only a zone for body-environment interaction but also is socially relevant, as we are driven to preserve our near-body, personal space from others. The current, novel study investigated how close proximity of a stranger modulates visuomotor processing of object affordances in shared, social space. Participants performed a behavioural object recognition task both alone and with a human confederate. All object images were in participants' reachable space but appeared relatively closer to the participant or the confederate. Results revealed when participants were alone, objects in both locations produced an affordance congruency effect but when the confederate was present, only objects nearer the participant elicited the effect. Findings suggest space is divided between strangers to preserve independent near-body space boundaries, and in turn this process influences motor coding for stimuli within that social space. To demonstrate that this visuomotor modulation represents a social phenomenon, rather than a general, attentional effect, two subsequent experiments employed nonhuman joint conditions. Neither a small, Japanese, waving cat statue (Experiment 2) nor a metronome (Experiment 3) modulated the affordance effect as in Experiment 1. These findings suggest a truly social explanation of the key interaction from Experiment 1. This study represents an important step toward understanding object affordance processing in real-world, social contexts and has implications broadly across fields of social action and cognition, and body space representation.

  5. Moving to Capture Children's Attention: Developing a Methodology for Measuring Visuomotor Attention.

    Directory of Open Access Journals (Sweden)

    Liam J B Hill

    Full Text Available Attention underpins many activities integral to a child's development. However, methodological limitations currently make large-scale assessment of children's attentional skill impractical, costly and lacking in ecological validity. Consequently we developed a measure of 'Visual Motor Attention' (VMA-a construct defined as the ability to sustain and adapt visuomotor behaviour in response to task-relevant visual information. In a series of experiments, we evaluated the capability of our method to measure attentional processes and their contributions in guiding visuomotor behaviour. Experiment 1 established the method's core features (ability to track stimuli moving on a tablet-computer screen with a hand-held stylus and demonstrated its sensitivity to principled manipulations in adults' attentional load. Experiment 2 standardised a format suitable for use with children and showed construct validity by capturing developmental changes in executive attention processes. Experiment 3 tested the hypothesis that children with and without coordination difficulties would show qualitatively different response patterns, finding an interaction between the cognitive and motor factors underpinning responses. Experiment 4 identified associations between VMA performance and existing standardised attention assessments and thereby confirmed convergent validity. These results establish a novel approach to measuring childhood attention that can produce meaningful functional assessments that capture how attention operates in an ecologically valid context (i.e. attention's specific contribution to visuomanual action.

  6. Moving to Capture Children's Attention: Developing a Methodology for Measuring Visuomotor Attention.

    Science.gov (United States)

    Hill, Liam J B; Coats, Rachel O; Mushtaq, Faisal; Williams, Justin H G; Aucott, Lorna S; Mon-Williams, Mark

    2016-01-01

    Attention underpins many activities integral to a child's development. However, methodological limitations currently make large-scale assessment of children's attentional skill impractical, costly and lacking in ecological validity. Consequently we developed a measure of 'Visual Motor Attention' (VMA)-a construct defined as the ability to sustain and adapt visuomotor behaviour in response to task-relevant visual information. In a series of experiments, we evaluated the capability of our method to measure attentional processes and their contributions in guiding visuomotor behaviour. Experiment 1 established the method's core features (ability to track stimuli moving on a tablet-computer screen with a hand-held stylus) and demonstrated its sensitivity to principled manipulations in adults' attentional load. Experiment 2 standardised a format suitable for use with children and showed construct validity by capturing developmental changes in executive attention processes. Experiment 3 tested the hypothesis that children with and without coordination difficulties would show qualitatively different response patterns, finding an interaction between the cognitive and motor factors underpinning responses. Experiment 4 identified associations between VMA performance and existing standardised attention assessments and thereby confirmed convergent validity. These results establish a novel approach to measuring childhood attention that can produce meaningful functional assessments that capture how attention operates in an ecologically valid context (i.e. attention's specific contribution to visuomanual action).

  7. Ultrahigh sensitivity of rotation sensing beyond the trade-off between sensitivity and linewidth by the storage of light in a dynamic slow-light resonator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xuenan; Zhang Yundong; Tian He; Wu Hao; Li Geng; Zhu Ruidong; Yuan Ping [National Key Laboratory of Tunable Laser Technology, Institute of Opto-Electronics, Harbin Institute of Technology, Harbin 150080 (China)

    2011-12-15

    We propose to employ the storage of light in a dynamically tuned add-drop resonator to realize an optical gyroscope of ultrahigh sensitivity and compact size. Taking the impact of the linewidth of incident light on the sensitivity into account, we investigate the effect of rotation on the propagation of a partially coherent light field in this dynamically tuned slow-light structure. It is demonstrated that the fundamental trade-off between the rotation-detection sensitivity and the linewidth will be overcome and the sensitivity-linewidth product will be enhanced by two orders of magnitude in comparison to that of the corresponding static slow-light structure. Furthermore, the optical gyroscope employing the storage of light in the dynamically tuned add-drop resonator can acquire ultrahigh sensitivity by extremely short fiber length without a high-performance laser source of narrow linewidth and a complex laser frequency stabilization system. Thus the proposal in this paper provides a promising and feasible scheme to realize highly sensitive and compact integrated optical gyroscopes by slow-light structures.

  8. Dynamic virtual simulation of the occurrence and severity of edge loading in hip replacements associated with variation in the rotational and translational surgical position.

    Science.gov (United States)

    Leng, Joanna; Al-Hajjar, Mazen; Wilcox, Ruth; Jones, Alison; Barton, David; Fisher, John

    2017-04-01

    Variation in the surgical positioning of total hip replacement can result in edge loading of the femoral head on the rim of the acetabular cup. Previous work has reported the effect of edge loading on the wear of hip replacement bearings with a fixed level of dynamic biomechanical hip separation. Variations in both rotational and translational surgical positioning of the hip joint replacement combine to influence both the biomechanics and the tribology including the severity of edge loading, the amount of dynamic separation, the force acting on the rim of the cup and the resultant wear and torque acting on the cup. In this study, a virtual model of a hip joint simulator has been developed to predict the effect of variations in some surgical positioning (inclination and medial-lateral offset) on the level of dynamic separation and the contact force of the head acting on the rim as a measure of severity of edge loading. The level of dynamic separation and force acting on the rim increased with increased translational mismatch between the centres of the femoral head and the acetabular cup from 0 to 4 mm and with increased cup inclination angle from 45° to 65°. The virtual model closely replicated the dynamics of the experimental hip simulator previously reported, which showed similar dynamic biomechanical trends, with the highest level of separation being found with a mismatch of 4 mm between the centres of the femoral head and acetabular cup and 65° cup inclination angle.

  9. Simulation study of the effect of wall roughness on the dynamics of granular flows in rotating semicylindrical chutes

    NARCIS (Netherlands)

    Shirsath, Sushil S.; Padding, Johan T.; Kuipers, J.A.M. (Hans); Clercx, Herman J.H.

    2015-01-01

    A discrete element model (DEM) is used to investigate the behavior of spherical particles flowing down a semicylindrical rotating chute. The DEM simulations are validated by comparing with particle tracking velocimetry results of spherical glass particles flowing through a smooth semicylindrical chu

  10. Implementation of dynamic crop growth processes into a land surface model: evaluation of energy, water and carbon fluxes under corn and soybean rotation

    Science.gov (United States)

    Song, Y.; Jain, A. K.; McIsaac, G. F.

    2013-12-01

    Worldwide expansion of agriculture is impacting the earth's climate by altering carbon, water, and energy fluxes, but the climate in turn is impacting crop production. To study this two-way interaction and its impact on seasonal dynamics of carbon, water, and energy fluxes, we implemented dynamic crop growth processes into a land surface model, the Integrated Science Assessment Model (ISAM). In particular, we implemented crop-specific phenology schemes and dynamic carbon allocation schemes. These schemes account for light, water, and nutrient stresses while allocating the assimilated carbon to leaf, root, stem, and grain pools. The dynamic vegetation structure simulation better captured the seasonal variability in leaf area index (LAI), canopy height, and root depth. We further implemented dynamic root distribution processes in soil layers, which better simulated the root response of soil water uptake and transpiration. Observational data for LAI, above- and belowground biomass, and carbon, water, and energy fluxes were compiled from two AmeriFlux sites, Mead, NE, and Bondville, IL, USA, to calibrate and evaluate the model performance. For the purposes of calibration and evaluation, we use a corn-soybean (C4-C3) rotation system over the period 2001-2004. The calibrated model was able to capture the diurnal and seasonal patterns of carbon assimilation and water and energy fluxes for the corn-soybean rotation system at these two sites. Specifically, the calculated gross primary production (GPP), net radiation fluxes at the top of the canopy, and latent heat fluxes compared well with observations. The largest bias in model results was in sensible heat flux (SH) for corn and soybean at both sites. The dynamic crop growth simulation better captured the seasonal variability in carbon and energy fluxes relative to the static simulation implemented in the original version of ISAM. Especially, with dynamic carbon allocation and root distribution processes, the model

  11. THE INFLUENCE OF THE EXERCISES OF GROSS AND FINE MOTOR SKILLS ON VISUO-MOTOR COORDINATION OF THE CEREBRAL PALSY CHILDREN

    Directory of Open Access Journals (Sweden)

    Almira Mujkić

    2013-09-01

    Full Text Available Visuomotor coordination is reffered to eye coordination and to various parts of the body in different activities and games. The aim of the research was to establish the influence of the exercises of gross and fine motor skills on visuomotor coordination of the cerebral palsy children. The sample was the case study where a male person of 3 and a half years old was an examinee. Measuring instrument used was the Test of visuomotor coordination of the gross motor skills of the dominant hand. Data were analyzed by t-test.

  12. Modeling Attitude Dynamics in Simulink: A Study of the Rotational and Translational Motion of a Spacecraft Given Torques and Impulses Generated by RMS Hand Controllers

    Science.gov (United States)

    Mauldin, Rebecca H.

    2010-01-01

    In order to study and control the attitude of a spacecraft, it is necessary to understand the natural motion of a body in orbit. Assuming a spacecraft to be a rigid body, dynamics describes the complete motion of the vehicle by the translational and rotational motion of the body. The Simulink Attitude Analysis Model applies the equations of rigid body motion to the study of a spacecraft?s attitude in orbit. Using a TCP/IP connection, Matlab reads the values of the Remote Manipulator System (RMS) hand controllers and passes them to Simulink as specified torque and impulse profiles. Simulink then uses the governing kinematic and dynamic equations of a rigid body in low earth orbit (LE0) to plot the attitude response of a spacecraft for five seconds given known applied torques and impulses, and constant principal moments of inertia.

  13. Dynamical tides excited in rotating stars of different masses and ages and the formation of close in orbits

    CERN Document Server

    Chernov, S V; Ivanov, P B

    2013-01-01

    We study the tidal response of rotating solar mass stars, as well as more massive rotating stars, of different ages in the context of tidal captures leading to either giant exoplanets on close in orbits, or the formation of binary systems in star clusters. To do this, we adopt approaches based on normal mode and associated overlap integral evaluation, developed in a companion paper by Ivanov et al., and direct numerical simulation, to evaluate energy and angular momentum exchanges between the orbit and normal modes. The two approaches are found to be in essential agreement apart from when encounters occur near to pseudosynchronization, where the stellar angular velocity and the orbital angular velocity at periastron are approximately matched. We find that the strength of tidal interaction being expressed in dimensionless natural units is significantly weaker for the more massive stars, as compared to the solar mass stars, because of the lack of significant convective regions in the former case. On the other h...

  14. Theory and simulation of the dynamics, deformation, and breakup of a chain of superparamagnetic beads under a rotating magnetic field

    Science.gov (United States)

    Vázquez-Quesada, A.; Franke, T.; Ellero, M.

    2017-03-01

    In this work, an analytical model for the behavior of superparamagnetic chains under the effect of a rotating magnetic field is presented. It is postulated that the relevant mechanisms for describing the shape and breakup of the chains into smaller fragments are the induced dipole-dipole magnetic force on the external beads, their translational and rotational drag forces, and the tangential lubrication between particles. Under this assumption, the characteristic S-shape of the chain can be qualitatively understood. Furthermore, based on a straight chain approximation, a novel analytical expression for the critical frequency for the chain breakup is obtained. In order to validate the model, the analytical expressions are compared with full three-dimensional smoothed particle hydrodynamics simulations of magnetic beads showing excellent agreement. Comparison with previous theoretical results and experimental data is also reported.

  15. Effects of Interfaces on Dynamics in Micro-Fluidic Devices: Slip-Boundaries’ Impact on Rotation Characteristics of Polar Liquid Film Motors

    Science.gov (United States)

    Jiang, Su-Rong; Liu, Zhong-Qiang; Amos Yinnon, Tamar; Kong, Xiang-Mu

    2017-05-01

    A new approach for exploring effects of interfaces on polar liquids is presented. Their impact on the polar liquid film motor (PLFM) - a novel micro-fluidic device - is studied. We account for the interface’s impact by modeling slip boundary effects on the PLFM’s electro-hydro-dynamical rotations. Our analytical results show as k={l}s/R increases (with {l}s denoting the slip length resulting from the interface’s impact on the film’s properties, k > -1 and R denoting the film’s radius): (a) PLFMs subsequently exhibit rotation characteristics under “negative-”, “no-”, “partial-” and “perfect-” slip boundary conditions; (b) The maximum value of the linear velocity of the steady rotating film increases linearly and its location approaches the film’s border; (c) The decay of the angular velocities’ dependency on the distance from the center of the film slows down, resulting in a macroscopic flow near the boundary. With our calculated rotation speed distributions consistent with the existing experimental ones, research aiming at fitting computed to measured distributions promises identifying the factors affecting {l}s, e.g., solid-fluid potential interactions and surface roughness. The consistency also is advantageous for optimizing PLFM’s applications as micro-washers, centrifuges, mixers in the lab-on-a-chip. Supported by National Natural Science Foundation of China under Grant Nos. 11302118, 11275112, and Natural Science Foundation of Shandong Province under Grant No. ZR2013AQ015

  16. Dynamic tides in rotating objects: a numerical investigation of inertial waves in fully convective or barotropic stars and planets

    CERN Document Server

    Papaloizou, J C B

    2010-01-01

    We perform direct numerical simulations of the tidal encounter of a rotating planet on a highly eccentric or parabolic orbit about a central star formulated as an initial value problem. This approach enables us to extend previous work of Ivanov & Papaloizou to consider planet models with solid cores and to avoid making an anelastic approximation. We obtain a power spectrum of the tidal response of coreless models which enables global inertial modes to be identified. Their frequencies are found to be in good agreement with those obtained using either a WKBJ approach or the anelastic spectral approach adopted in previous work for small planet rotation rates. We also find that the dependence of the normal mode frequencies on the planet angular velocity in case of higher rotation rates can for the most part be understood by applying first order perturbation theory to the anelastic modes. We calculate the energy and angular momentum exchanged as a result of the tidal encounter and for coreless models again fin...

  17. Quantum dynamics of rovibrational transitions in H2-H2 collisions: internal energy and rotational angular momentum conservation effects.

    Science.gov (United States)

    Fonseca dos Santos, S; Balakrishnan, N; Lepp, S; Quéméner, G; Forrey, R C; Hinde, R J; Stancil, P C

    2011-06-01

    We present a full dimensional quantum mechanical treatment of collisions between two H(2) molecules over a wide range of energies. Elastic and state-to-state inelastic cross sections for ortho-H(2) + para-H(2) and ortho-H(2) + ortho-H(2) collisions have been computed for different initial rovibrational levels of the molecules. For rovibrationally excited molecules, it has been found that state-to-state transitions are highly specific. Inelastic collisions that conserve the total rotational angular momentum of the diatoms and that involve small changes in the internal energy are found to be highly efficient. The effectiveness of these quasiresonant processes increases with decreasing collision energy and they become highly state-selective at ultracold temperatures. They are found to be more dominant for rotational energy exchange than for vibrational transitions. For non-reactive collisions between ortho- and para-H(2) molecules for which rotational energy exchange is forbidden, the quasiresonant mechanism involves a purely vibrational energy transfer albeit with less efficiency. When inelastic collisions are dominated by a quasiresonant transition calculations using a reduced basis set involving only the quasiresonant channels yield nearly identical results as the full basis set calculation leading to dramatic savings in computational cost.

  18. Avalanche dynamics of granular materials under the slumping regime in a rotating drum as revealed by speckle visibility spectroscopy.

    Science.gov (United States)

    Yang, H; Li, R; Kong, P; Sun, Q C; Biggs, M J; Zivkovic, V

    2015-04-01

    We used speckle visibility spectroscopy to measure the time-resolved dynamcis of avalanching down the inclined surface of a granular material in a half-full rotating drum operating in the slumping regime. The distribution of the avalanche period, t(d), rest time between them, t(r), and peak particle velocity fluctuation, δv(p)(2), are all normally distributed. While the distributions of the two times at the top and bottom of the free surface are very similar, the particle velocity fluctuation is greater at the bottom of the free surface than at the top. The rest time is observed to be inversely related to the drum speed. Combining this with the relation of t(r) and the difference of the upper and lower angle of repose for the granular material, Δθ, we find that the latter decreases linearly with increasing rotational speed. We also observe that t(d) increases in a linear fashion with the drum speed. Using the relation of t(r) and the distance that particles have to move during an avalanche, we further find that a new scaling relation of the mean number of avalanches required to traverse the free surface with drum speed. We find that the slumping frequency increases with the rotating speed before becoming constant in the slumping-to-rolling transition region. Finally, we find that the average peak of the fluctuation speed of the avalanche, δv(p)(2), increases linearly with the drum speed.

  19. Dynamic Test and Research of Spindle Rotation Error%主轴回转误差的动态测试和研究∗

    Institute of Scientific and Technical Information of China (English)

    孙军; 黄圆; 秦显军; 钱彬彬

    2015-01-01

    In order to realize the error of measuring spindle rotation, to achieve dynamic separation of spin-dle rotation accuracy, paper uses mathematical statistics on LabVIEW software to develop a separate spindle error dynamic simulation software by mathematical statistics and theoretical basis for the design of a Rotary error test system based on LabVIEW spindle. The system consists of combining CompactRIO embedded sys-tem controller, LabVIEW software programming, data collection, data processing functions and data dis-play. The system is used to measure the actual spindle rotation accuracy to obtain high-precision spindle er-ror number.%为实现主轴回转误差的测量,实现主轴回转精度的动态分离,文章运用数理统计法在LabVIEW软件上开发了一套主轴回转误差动态分离模拟软件,并由数理统计法为理论基础设计出一个基于LabVIEW的主轴回转误差测试系统。该系统由结合嵌入式系统CompactRIO为控制器、LabVIEW软件编程,可以实现数据采集、数据处理和数据显示的功能。该系统用于机床主轴回转精度的实际测量,得到了高精度的主轴回转误差数据,为主轴回转误差的动态测量提供技术支持。

  20. Practice effects reveal visuomotor vulnerability in school and university rugby players.

    Science.gov (United States)

    Shuttleworth-Edwards, Ann B; Radloff, Sarah E; Whitefield-Alexander, Victoria J; Smith, Ian P; Horsman, Mark

    2014-02-01

    This article reports on three pre- versus post-season prospective studies in which male university and high school contact sport players predominantly of Rugby Union (hereafter rugby) were compared with age, education, and IQ equivalent non-contact sport controls on the ImPACT (Immediate Postconcussion Assessment and Cognitive Testing) test. All analyses revealed a relative absence of practice effects on the Visual Motor Speed (VMS) composite for contact sport groups compared with controls. The VMS data for rugby players from each study were pooled and subjected to additional analysis (Rugby, n = 145; Controls, n = 106). Controls revealed significant improvement over the season (p rugby players whose performance remained the same (interaction effect, p = .028). It is apparent that practice effects have diagnostic potential in this context, implicating vulnerability on speeded visuomotor processing in association with participation in rugby. Pointers for further research and concussion management in the individual case are explored.

  1. A new neural net approach to robot 3D perception and visuo-motor coordination

    Science.gov (United States)

    Lee, Sukhan

    1992-01-01

    A novel neural network approach to robot hand-eye coordination is presented. The approach provides a true sense of visual error servoing, redundant arm configuration control for collision avoidance, and invariant visuo-motor learning under gazing control. A 3-D perception network is introduced to represent the robot internal 3-D metric space in which visual error servoing and arm configuration control are performed. The arm kinematic network performs the bidirectional association between 3-D space arm configurations and joint angles, and enforces the legitimate arm configurations. The arm kinematic net is structured by a radial-based competitive and cooperative network with hierarchical self-organizing learning. The main goal of the present work is to demonstrate that the neural net representation of the robot 3-D perception net serves as an important intermediate functional block connecting robot eyes and arms.

  2. Rapid visuomotor processing of phobic images in spider- and snake-fearful participants.

    Science.gov (United States)

    Haberkamp, Anke; Schmidt, Filipp; Schmidt, Thomas

    2013-10-01

    This study investigates enhanced visuomotor processing of phobic compared to fear-relevant and neutral stimuli. We used a response priming design to measure rapid, automatic motor activation by natural images (spiders, snakes, mushrooms, and flowers) in spider-fearful, snake-fearful, and control participants. We found strong priming effects in all tasks and conditions; however, results showed marked differences between groups. Most importantly, in the group of spider-fearful individuals, spider pictures had a strong and specific influence on even the fastest motor responses: Phobic primes entailed the largest priming effects, and phobic targets accelerated responses, both effects indicating speeded response activation by phobic images. In snake-fearful participants, this processing enhancement for phobic material was less pronounced and extended to both snake and spider images. We conclude that spider phobia leads to enhanced processing capacity for phobic images. We argue that this is enabled by long-term perceptual learning processes.

  3. An experimental analysis of strontium titanate ceramic substrates polished by magnetorheological finishing with dynamic magnetic fields formed by rotating magnetic poles

    Science.gov (United States)

    Pan, Jisheng; Yu, Peng; Yan, Qiusheng; Li, Weihua

    2017-05-01

    Strontium titanate (SrTiO3, STO) ceramic substrate is an incipient ferroelectric material with a perovskite structure and which has a wide range of applications in the fields of microwave, millimetre wave, and optic fibre. This paper reports on a system of experiments carried out on STO substrates using a new magnetorheological (MR) finishing process where dynamic magnetic fields are formed by magnetic poles rotate. The results show that a circular ring shaped polishing belt with a stability evaluation zone appears on the surface after being polished by MR finishing with a single-point dynamic magnetic field. The dynamic magnetic fields are stronger when the revolutions of magnetic pole increase and eccentricity of pole enlarge, with the surface finish is smoother and more material is removed. The optimum machining times, machining gap, oscillation distance, eccentricity of pole, revolutions of the workpiece and magnetic pole are 60 min, 0.8 mm, 0 mm, 7 mm, and 350 r min-1 and 90 r min-1, respectively, and the best MR fluid consists of 6 wt% of diamond abrasives in W1 particle size and 18 wt% of carbonyl iron powder in W3.5 particle size. A surface roughness of Ra and a material removal rate of 8 nm and 0.154 μm min-1 can be obtained in these optimum process conditions. Finally, the polishing mechanism for dynamic magnetic fields and the mechanism for removing material from STO ceramic substrates are discussed in detail.

  4. CISM Course on Rotating Fluids

    CERN Document Server

    1992-01-01

    The volume presents a comprehensive overview of rotation effects on fluid behavior, emphasizing non-linear processes. The subject is introduced by giving a range of examples of rotating fluids encountered in geophysics and engineering. This is then followed by a discussion of the relevant scales and parameters of rotating flow, and an introduction to geostrophic balance and vorticity concepts. There are few books on rotating fluids and this volume is, therefore, a welcome addition. It is the first volume which contains a unified view of turbulence in rotating fluids, instability and vortex dynamics. Some aspects of wave motions covered here are not found elsewhere.

  5. Impact of scaffold micro and macro architecture on Schwann cell proliferation under dynamic conditions in a rotating wall vessel bioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Valmikinathan, Chandra M.; Hoffman, John [Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030 (United States); Yu, Xiaojun, E-mail: xyu@stevens.edu [Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, 07030 (United States)

    2011-01-01

    Over the last decade tissue engineering has emerged as a powerful alternative to regenerate lost tissues owing to trauma or tumor. Evidence shows that Schwann cell containing scaffolds have improved performance in vivo as compared to scaffolds that depend on cellularization post implantation. However, owing to limited supply of cells from the patients themselves, several approaches have been taken to enhance cell proliferation rates to produce complete and uniform cellularization of scaffolds. The most common approach is the application of a bioreactor to enhance cell proliferation rate and therefore reduce the time needed to obtain sufficiently significant number of glial cells, prior to implantation. In this study, we show the application of a rotating wall bioreactor system for studying Schwann cell proliferation on nanofibrous spiral shaped scaffolds, prepared by solvent casting and salt leaching techniques. The scaffolds were fabricated from polycaprolactone (PCL), which has ideal mechanical properties and upon degradation does not produce acidic byproducts. The spiral scaffolds were coated with aligned or random nanofibers, produced by electrospinning, to provide a substrate that mimics the native extracellular matrix and the essential contact guidance cues. At the 4 day time point, an enhanced rate of cell proliferation was observed on the open structured nanofibrous spiral scaffolds in a rotating wall bioreactor, as compared to static culture conditions. However, the cell proliferation rate on the other contemporary scaffolds architectures such as the tubular and cylindrical scaffolds show reduced cell proliferation in the bioreactor as compared to static conditions, at the same time point. Moreover, the rotating wall bioreactor does not alter the orientation or the phenotype of the Schwann cells on the aligned nanofiber containing scaffolds, wherein, the cells remain aligned along the length of the scaffolds. Therefore, these open structured spiral

  6. The dynamics of ring rotation in ferrocene, nickelocene and ruthenocene by incoherent quadi-elastic neutron scattering

    Science.gov (United States)

    Gardner, A. B.; Howard, S.; Waddington, T. C.; Richardson, R. M.; Tomkinson, J.

    1981-05-01

    Incoherent quasi-elastic neutron scattering has been used to study the reorientational motions of the cyclopentadienyl rings in ferrocene, nickelocene and ruthenocene. The results for ferrocene show that the activation energy for ring rotation drops above the 164 K phase transition to 4.4 ± 0.5 kJ mol-1 (which is approximately half its low temperature value) but the rings still appear to jump between only five orientations on the observable time scale. At room temperature, the rings in nickelocene appear to behave the same as in ferrocene but in ruthenocene they reorientate much less frequently and resemble those in ferrocene below 164 K.

  7. Visuomotor adaptation needs a validation of prediction error by feedback error

    Directory of Open Access Journals (Sweden)

    Valérie eGaveau

    2014-11-01

    Full Text Available The processes underlying short-term plasticity induced by visuomotor adaptation to a shifted visual field are still debated. Two main sources of error can induce motor adaptation: reaching feedback errors, which correspond to visually perceived discrepancies between hand and target positions, and errors between predicted and actual visual reafferences of the moving hand. These two sources of error are closely intertwined and difficult to disentangle, as both the target and the reaching limb are simultaneously visible. Accordingly, the goal of the present study was to clarify the relative contributions of these two types of errors during a pointing task under prism-displaced vision. In ‘terminal feedback error’ condition, viewing of their hand by subjects was allowed only at movement end, simultaneously with viewing of the target. In ‘movement prediction error’ condition, viewing of the hand was limited to movement duration, in the absence of any visual target, and error signals arose solely from comparisons between predicted and actual reafferences of the hand. In order to prevent intentional corrections of errors, a subthreshold, progressive stepwise increase in prism deviation was used, so that subjects remained unaware of the visual deviation applied in both conditions. An adaptive aftereffect was observed in the ‘terminal feedback error’ condition only. As far as subjects remained unaware of the optical deviation and self-assigned pointing errors, prediction error alone was insufficient to induce adaptation. These results indicate a critical role of hand-to-target feedback error signals in visuomotor adaptation; consistent with recent neurophysiological findings, they suggest that a combination of feedback and prediction error signals is necessary for eliciting aftereffects. They also suggest that feedback error updates the prediction of reafferences when a visual perturbation is introduced gradually and cognitive factors are

  8. Aggregation dynamics and magnetic properties of magnetic micrometer-sized particles dispersed in a fluid under the action of rotating magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Llera, María [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Codnia, Jorge [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina); Centro de Investigaciones en Láseres y Aplicaciones, CITEDEF-CONICET, Buenos Aires (Argentina); Jorge, Guillermo A., E-mail: gjorge@ungs.edu.ar [Instituto de Ciencias, Universidad Nacional de General Sarmiento, Buenos Aires (Argentina)

    2015-06-15

    We present a dynamic study of soft magnetic, commercial Fe and Ni micrometer-sized particles dispersed in oleic acid and subjected to a variable (rotating) magnetic field in the horizontal plane. A very complex structure is formed after the particles decant towards the bottom liquid–solid interface and the magnetic field is applied for several minutes. The dynamics of structure formation was studied by means of the registration and analysis of microscopic video images, through a Matlab image analysis script. Several parameters, such as the number of clusters, the perimeter-based fractal dimension and circularity, were calculated as a function of time. The time evolution of the number of clusters was found to follow a power-law behavior, with an exponent consistent with that found in other studies for magnetic systems, whereas the typical formation time depends on the particle diameter and field configuration. Complementarily, the magnetic properties of the formed structure were studied, reproducing the experiment with liquid paraffin as the containing fluid, and then letting it solidify. The sample obtained was studied by vibrating sample magnetometry. The magnetization curves show that the material obtained is a planar magnetically anisotropic material, which could eventually be used as an anisotropic magnetic sensor or actuator. - Highlights: • Dynamic study of Fe and Ni particles in oleic acid under rotating fields. • A very complex system of interconnected clusters was observed. • Larger particles had a smaller aggregation time. • A power law behavior of the number of clusters vs. time. • A Fe-paraffin sample with planar anisotropy characterized.

  9. A unified normal mode approach to dynamic tides and its application to rotating Sun-like stars

    CERN Document Server

    Ivanov, P B; Chernov, S V

    2013-01-01

    We determine the response of a uniformly rotating star to tidal perturbations due to a companion. General periodic orbits and parabolic flybys are considered. We evaluate energy and angular momentum exchange rates as a sum of contributions from normal modes allowing for dissipative processes. We consider the case when the response is dominated by the contribution of an identifiable regular spectrum of low frequency modes, such as gravity modes and evaluate it in the limit of very weak dissipation. Our formalism may be applied both to Sun-like stars with radiative cores and convective envelopes and to more massive stars with convective cores and radiative envelopes. We provide general expressions for transfer of energy and angular momentum valid for an orbit with any eccentricity. Detailed calculations are made for Sun-like stars in the slow rotation regime where centrifugal distortion is neglected in the equilibrium and the traditional approximation is made for the normal modes. We use both a WKBJ procedure a...

  10. Impacts of stellar evolution and dynamics on the habitable zone: The role of rotation and magnetic activity

    CERN Document Server

    Florian, Gallet; Louis, Amard; Sacha, Brun; Ana, Palacios; Stephane, Mathis

    2016-01-01

    In this article, we aim to provide the community with the dependence of the habitable zone upon the stellar mass, metallicity, rotation, and for various prescriptions of the limits of the habitable zone. We use the STAREVOL code to study the evolution of the habitable zone and of the continuously habitable zone limits. Mass and metallicity are the stellar parameters that have the most dramatic effects on the habitable zone limits. Conversely, for a given stellar mass and metallicity, stellar rotation has only a marginal effect on these limits and does not modify the width of the habitable zone. The evolution of the habitable zone limits is also correlated to the evolution of the stellar activity (through the Rossby number) that depends on the stellar mass considered. While the magnetic activity has negligible consequence in the case of more massive stars, these effects may have a strong impact on the habitability of a planet around M dwarf stars. Thus, stellar activity cannot be neglected and may have strong ...

  11. Using the Discrete Dipole Approximation and Holographic Microscopy to Measure Rotational Dynamics of Non-spherical Colloids

    CERN Document Server

    Wang, Anna; Fung, Jerome; Razavi, Sepideh; Kretzschmar, Ilona; Chaudhary, Kundan; Lewis, Jennifer A; Manoharan, Vinothan N

    2013-01-01

    We present a new, high-speed technique to track the three-dimensional translation and rotation of non-spherical colloidal particles. We capture digital holograms of micrometer-scale silica rods and sub-micrometer-scale Janus particles freely diffusing in water, and then fit numerical scattering models based on the discrete dipole approximation to the measured holograms. This inverse-scattering approach allows us to extract the the position and orientation of the particles as a function of time, along with static parameters including the size, shape, and refractive index. The best-fit sizes and refractive indices of both particles agree well with expected values. The technique is able to track the center of mass of the rod to a precision of 35 nm and its orientation to a precision of 1.5$^\\circ$, comparable to or better than the precision of other 3D diffusion measurements on non-spherical particles. Furthermore, the measured translational and rotational diffusion coefficients for the silica rods agree with hy...

  12. 基于混合液晶分子动力学模拟比较液晶分子旋转黏度大小∗%Rotational viscosity comparison of liquid crystals based on the molecular dynamics of mixtures

    Institute of Scientific and Technical Information of China (English)

    王启东; 彭增辉; 刘永刚; 姚丽双; 任淦; 宣丽

    2015-01-01

    It is critical to improve the response speed of a liquid crystal wavefront corrector in order to increase the band-width of a liquid crystal adaptive optics system. The design of liquid crystal molecules with small rotational viscosity becomes a basic method of increasing the response speed of a liquid crystal wavefront corrector. Various phases of liquid crystal from molecular dynamics simulation are given in this paper, and the detailed computational methods of order parameter and rotational viscosity are also presented. Rotational viscosities of liquid crystals are compared based on the molecular dynamics of mixtures. The data fluctuation is reduced effectively through several simulations and the multiple analysis of original data. A detailed process of molecular dynamics of mixtures is given in this paper and the result is greatly satisfactory. We believe that one can perform a better molecular design using this process and obtain a better understanding of molecular interactions of LCs.

  13. The interplay between helicity and rotation in turbulence: implications for scaling laws and small-scale dynamics

    CERN Document Server

    Pouquet, A

    2009-01-01

    Invariance properties of physical systems govern their behavior: energy conservation in turbulence drives a wide distribution of energy among modes, observed in geophysical or astrophysical flows. In ideal hydrodynamics, the role of helicity conservation (correlation between velocity and its curl, measuring departures from mirror symmetry) remains unclear since it does not alter the energy spectrum. However, with solid body rotation, significant differences emerge between helical and non-helical flows. We first outline several results, like the energy and helicity spectral distribution and the breaking of strict universality for the individual spectra. Using massive numerical simulations, we then show that small-scale structures and their intermittency properties differ according to whether helicity is present or not, in particular with respect to the emergence of Beltrami-core vortices (BCV) that are laminar helical vertical updrafts. These results point to the discovery of a small parameter besides the Ross...

  14. Dissipative particle dynamics simulation of flow generated by two rotating concentric cylinders: II. Lateral dissipative and random forces

    Energy Technology Data Exchange (ETDEWEB)

    Filipovic, N [Faculty of Mechanical Engineering, University of Kragujevac (Serbia); Haber, S [Technion-Israel Institute of Technology, Haifa (Israel); Kojic, M [Faculty of Mechanical Engineering, University of Kragujevac (Serbia); Tsuda, A [Harvard School of Public Health, Harvard University, Boston, MA (United States)

    2008-02-07

    Traditional DPD methods address dissipative and random forces exerted along the line connecting neighbouring particles. Espanol (1998 Phys. Rev. E 57 2930-48) suggested adding dissipative and random force components in a direction perpendicular to this line. This paper focuses on the advantages and disadvantages of such an addition as compared with the traditional DPD method. Our benchmark system comprises fluid initially at rest occupying the space between two concentric cylinders rotating with various angular velocities. The effect of the lateral force components on the time evolution of the simulated velocity profile was also compared with that of the known analytical solution. The results show that (i) the solution accuracy at steady state has improved and the error has been reduced by at least 30% (in one case by 75%), (ii) the DPD time to reach steady state has been halved, (iii) the CPU time has increased by only 30%, and (iv) no significant differences exist in density and temperature distributions.

  15. Dissipative particle dynamics simulation of flow generated by two rotating concentric cylinders: II. Lateral dissipative and random forces

    Science.gov (United States)

    Filipovic, N.; Haber, S.; Kojic, M.; Tsuda, A.

    2008-02-01

    Traditional DPD methods address dissipative and random forces exerted along the line connecting neighbouring particles. Espanol (1998 Phys. Rev. E 57 2930-48) suggested adding dissipative and random force components in a direction perpendicular to this line. This paper focuses on the advantages and disadvantages of such an addition as compared with the traditional DPD method. Our benchmark system comprises fluid initially at rest occupying the space between two concentric cylinders rotating with various angular velocities. The effect of the lateral force components on the time evolution of the simulated velocity profile was also compared with that of the known analytical solution. The results show that (i) the solution accuracy at steady state has improved and the error has been reduced by at least 30% (in one case by 75%), (ii) the DPD time to reach steady state has been halved, (iii) the CPU time has increased by only 30%, and (iv) no significant differences exist in density and temperature distributions.

  16. Rotating Wavepackets

    Science.gov (United States)

    Lekner, John

    2008-01-01

    Any free-particle wavepacket solution of Schrodinger's equation can be converted by differentiations to wavepackets rotating about the original direction of motion. The angular momentum component along the motion associated with this rotation is an integral multiple of [h-bar]. It is an "intrinsic" angular momentum: independent of origin and…

  17. Finite Fault Analysis and Near Field Dynamic Strains and Rotations due to the 11/05/2011 (Mw5.2) Lorca Earthquake, South-Eastern Spain

    CERN Document Server

    Santoyo, Miguel Angel

    2012-01-01

    The 11/5/2011 Lorca, Spain earthquake (Mw=5.2) and its foreshock produced extensive damage to buildings and infrastructures within the town of Lorca and vicinity. During these earthquakes, evidence of rotational behaviour and permanent deformations in many structures were observed. The closest accelerometric station that recorded the ground motions was located about 6.0 km from the hypocentral zone. To analyze these aspects and study the source properties from the near-field, I obtained by an appropriate double time-integration procedure of accelerograms, the displacement time histories including the static component. Using these data I calculated the foreshock and the mainshock slip distributions by means of a complete waveform kinematic inversion. To study the dynamic deformations, the 3D tensor of displacement gradients at Lorca station was computed by a single station method. This was done assuming the incidence of body waves at the recording location. Using the finite fault inversion results and a first ...

  18. Simulation and Analysis on the Two-Phase Flow Fields in a Rotating-Stream-Tray Absorber by Using Computational Fluid Dynamics

    Institute of Scientific and Technical Information of China (English)

    邵雄飞; 吴忠标

    2004-01-01

    The flow field of gas and liquid in a φ150mm rotating-stream-tray (RST) scrubber is simulated by using computational fluid dynamic (CFD) method. The simulation is based on the two-equation RNG κ-ε turbulence model, Eulerian multiphase model, mad a real-shape 3D model with a huge number of meshes. The simulation results include detailed information about velocity, pressure, volume fraction and so on. Some features of the flow field are obtained: liquid is atomized in a thin annular zone; a high velocity air zone prevents water drops at the bottom from flying towards the wall;the pressure varies sharply at the end of blades and so on. The results will be helpful for structure optimization and engineering design.

  19. Learning efficacy of explicit visuomotor sequences in children with attention-deficit/hyperactivity disorder and Asperger syndrome.

    Science.gov (United States)

    Watanabe, Katsumi; Ikeda, Hanako; Miyao, Masutomo

    2010-05-01

    Developmental disorders such as attention-deficit/hyperactivity disorder (ADHD) and Asperger syndrome (AS) are often associated with learning disabilities. This study investigated the explicit learning of visuomotor sequences in 17 ADHD children (mean age 12.1), 21 AS children (mean age 12.7), and 15 typically developing children (mean age: 12.3). The participants were required to explore a hidden sequence of button presses by trial and error and elaborate the learned sequence (2 x 10 task: Hikosaka et al. 1996). The results indicated that although ADHD and AS children had a tendency of repeating the same errors and took longer to complete a sequence, both showed a degree and pattern of improvement in accuracy and speed similar to that of typically developing children. These results suggest that the explicit learning of visuomotor sequence in ADHD and AS patients is largely unimpaired.

  20. How does visuomotor priming differ for biological and non-biological stimuli? A review of the evidence.

    Science.gov (United States)

    Gowen, E; Poliakoff, E

    2012-07-01

    Visuomotor priming occurs when our actions are influenced by observing a compatible or incompatible action. Here we ask whether visuomotor priming is specific to human, biological actions or generalises to non-biological movements, such as abstract shapes or robots. Reviewing the evidence indicates that priming occurs for both types of stimuli and emphasises the contributions of both bottom-up (e.g. stimulus saliency, appearance, kinematics) and top-down (e.g. attention and prior knowledge) factors. We propose a model suggesting that although bottom-up features play a critical role, the degree of difference in priming for biological versus non-biological stimuli can be ultimately shaped by top-down factors.

  1. Measurement of Ultraslow Rotational Dynamics of Probes in Imidazolium-Based Ionic Liquids Near and Below the Glass Transition Temperature: Studying the Role of Structural Heterogeneity on Dynamic Heterogeneity

    Science.gov (United States)

    Mendoza, Kayla; Udugama-Arachchilage, Rakhitha; Bardak, Fehmi; Tamas, George; Quitevis, Edward

    2014-03-01

    The dynamics of imidazolium-based ionic liquids were probed in the supercooled liquid regime by observing the fluorescence recovery after photobleaching of directionally oriented tetracene molecules. Spatial heterogeneity arises in ionic liquids containing a 1-alkyl-3-methylimidazolium cation for alkyl chain lengths equal to and exceeding four carbons; aggregation of the alkyl tails leads to the formation of non-polar domains, which increase in size with increasing alkyl chain length. Near the glass transition, supercooled liquids relax non-exponentially, and this non-exponentiality has been attributed to dynamic heterogeneity. The purpose of this study was to observe the role of structural heterogeneity on dynamic heterogeneity. The rotational dynamics of tetracene in 1-butyl-3-methylimidazolium bistriflate, 1, 3-dibutylimidazolium bistriflate, and 1-heptyl-3-methylimidazlium bistriflate were observed in the vicinity of their glass transition temperatures. From the weak dependence of the degree of non-exponentiality exhibited by the relaxation function on alky chain length and cation symmetry, it was concluded that structural heterogeneity does not play a strong role in determining dynamic heterogeneity. This work was supported by NSF grant CHE-1153077.

  2. Impacts of stellar evolution and dynamics on the habitable zone: The role of rotation and magnetic activity

    Science.gov (United States)

    Gallet, F.; Charbonnel, C.; Amard, L.; Brun, S.; Palacios, A.; Mathis, S.

    2017-01-01

    Context. With the ever growing number of detected and confirmed exoplanets, the probability of finding a planet that looks like the Earth increases continuously. While it is clear that the presence of a planet in the habitable zone does not imply the planet is habitable, a systematic study of the evolution of the habitable zone is required to account for its dependence on stellar parameters. Aims: In this article, we aim to provide the community with the dependence of the habitable zone upon the stellar mass, metallicity, rotation, and for various prescriptions of the limits of the habitable zone. Methods: We use stellar evolution models computed with the code STAREVOL, which includes the most current physical mechanisms of internal transport of angular momentum and external wind braking, to study the evolution of the habitable zone and the continuously habitable zone limits. Results: The stellar parameters mass and metallicity affect the habitable zone limits most dramatically. Conversely, for a given stellar mass and metallicity, stellar rotation has only a marginal effect on these limits and does not modify the width of the habitable zone. Moreover, and as expected in the main-sequence phase and for a given stellar mass and metallicity, the habitable zone limits remain almost constant, and this confirms the usual assumptions of a relative constancy of these limits during that phase. The evolution of the habitable zone limits is also correlated to the evolution of the stellar activity (through the Rossby number), which depends on the stellar mass considered. While the magnetic activity has negligible consequence in the case of more massive stars, these effects may have a strong impact on the habitability of a planet around M-dwarf stars. Thus, stellar activity cannot be neglected and may have a strong impact on the development of life during the early stage of the continuously habitable zone phase of low-mass stars. Using observed trends of stellar magnetic field

  3. Explaining the relationship between number line estimation and mathematical achievement: The role of visuomotor integration and visuospatial skills.

    Science.gov (United States)

    Simms, Victoria; Clayton, Sarah; Cragg, Lucy; Gilmore, Camilla; Johnson, Samantha

    2016-05-01

    Performance on number line tasks, typically used as a measure of numerical representations, are reliably related to children's mathematical achievement. However, recent debate has questioned what precisely performance on the number line estimation task measures. Specifically, there has been a suggestion that this task may measure not only numerical representations but also proportional judgment skills; if this is the case, then individual differences in visuospatial skills, not just the precision of numerical representations, may explain the relationship between number line estimation and mathematical achievement. The current study investigated the relationships among visuospatial skills, visuomotor integration, number line estimation, and mathematical achievement. In total, 77 children were assessed using a number line estimation task, a standardized measure of mathematical achievement, and tests of visuospatial skills and visuomotor integration. The majority of measures were significantly correlated. In addition, the relationship between one metric from the number line estimation task (R(2)LIN) and mathematical achievement was fully explained by visuomotor integration and visuospatial skill competency. These results have important implications for understanding what the number line task measures as well as the choice of number line metric for research purposes.

  4. Rotational kinematics of pelvis and upper trunk at butterfly stroke: Can fins affect the dynamics of the system?

    Science.gov (United States)

    Averianova, Anastasia; Nikodelis, Thomas; Konstantakos, Vasileios; Kollias, Iraklis

    2016-02-08

    The purpose of the present study was to investigate the rotational kinematics pattern of the upper trunk and the pelvis and the complexity-variability of their movement, during the sprint butterfly stroke between male and female swimmers with long fins (18-26 cm) and without fins. Two pairs of 3D accelerometers and gyroscopes were used to measure segments' flexion-extension angles. There were no gender differences apart from the record. The amplitude values at the pelvis were significantly larger when swimming without fins while at the C7 they were significantly larger when swimming with them. Autocorrelation coefficients of angles' time histories were higher when swimming with fins for both segments. The power spectrums revealed a dominant frequency representing the stroke period which grew significantly stronger for the fin condition. Correlation Dimension verified a lower dimensionality for the fin condition for the C7 segment movement pattern. Overall fin use seems to offer "strength" to the swimmer's movement pattern. This does not imply better movement coordination, but rather a trend toward a more stable attractor.

  5. Towards a new generalized space expansion dynamics applied to the rotation of galaxies and Tully Fisher law

    CERN Document Server

    Fleuret, Jacques

    2016-01-01

    Up to now, the rotational velocities of galaxies are not clearly understood and the experimental Tully Fisher rule, linking the total galactic mass to the fourth power of the velocity, through an acceleration coefficient of about 10-10 m/s2 has not found a deep theoretical explanation. Tentative proposals (MOND theory of a modified Newton s law and extraneous dark matter) do not bring a definite clarification. We propose here a new approach to this problem, without exotic matter and using the classical Newton force. But we introduce a new additional universal acceleration, which could represent a universal expansion law valid at the scale level of a galaxy. We show that this hypothesis leads to a good description of the observed variations of the galactic transverse velocity. It can be considered as a consequence of the Scale Expansion Cosmos theory (SEC) introduced by J. Masreliez, but we postulate that the space expansion acceleration universally applies at any scale. We obtain a formal derivation of the Tu...

  6. Phenology and population dynamics of willow beetles (Coleoptera: chrysomelidae) in short-rotation coppiced willows at Long Ashton

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-05-01

    The life cycles and phylogeny of three willow beetle pests, Phyllodecta vulgatissima, P. vitellinae and Galerucella lineola (Coleoptera, Chrysomelidae), were investigated during 1994-95 in an experimental plantation of short-rotation coppiced willows (Salix viminalis Bowles Hybrid) at Pearces Farm, Long Ashton (Bristol), UK, Willow rods were sampled at regular intervals throughout the year and carefully search for eggs, larvae and adult beetles. An extensive survey was done in hedgerows around the site during February 1995 in order to identify the overwintering sites of adult beetles. In autumn 1995, hibernation trap-bands were used to study the onset of hibernation and the distribution of hibernating in the vicinity of the willow plantation. Adult flight activity was monitored each week throughout the year using window traps. Pot-grown willows were established in the field to augment observations on beetle behaviour in spring and autumn. Exclusion cages were used during the summer in an attempt to estimate the natural mortality of eggs larvae and pupae, but this technique had to be abandoned because all the cages were attacked and damaged by wasps. The fecundity of adult beetles and the development of eggs, larvae and pupae were measured in the laboratory under controlled environment conditions. (Author)

  7. Rotating three-dimensional dynamic culture of adult human bone marrow-derived cells for tissue engineering of hyaline cartilage.

    Science.gov (United States)

    Sakai, Shinsuke; Mishima, Hajime; Ishii, Tomoo; Akaogi, Hiroshi; Yoshioka, Tomokazu; Ohyabu, Yoshimi; Chang, Fei; Ochiai, Naoyuki; Uemura, Toshimasa

    2009-04-01

    The method of constructing cartilage tissue from bone marrow-derived cells in vitro is considered a valuable technique for hyaline cartilage regenerative medicine. Using a rotating wall vessel (RWV) bioreactor developed in a NASA space experiment, we attempted to efficiently construct hyaline cartilage tissue from human bone marrow-derived cells without using a scaffold. Bone marrow aspirates were obtained from the iliac crest of nine patients during orthopedic operation. After their proliferation in monolayer culture, the adherent cells were cultured in the RWV bioreactor with chondrogenic medium for 2 weeks. Cells from the same source were cultured in pellet culture as controls. Histological and immunohistological evaluations (collagen type I and II) and quantification of glycosaminoglycan were performed on formed tissues and compared. The engineered constructs obtained using the RWV bioreactor showed strong features of hyaline cartilage in terms of their morphology as determined by histological and immunohistological evaluations. The glycosaminoglycan contents per microg DNA of the tissues were 10.01 +/- 3.49 microg/microg DNA in the case of the RWV bioreactor and 6.27 +/- 3.41 microg/microg DNA in the case of the pellet culture, and their difference was significant. The RWV bioreactor could provide an excellent environment for three-dimensional cartilage tissue architecture that can promote the chondrogenic differentiation of adult human bone marrow-derived cells.

  8. Sum Frequency Generation Spectroscopy and Molecular Dynamics Simulations Reveal a Rotationally Fluid Adsorption State of α-Pinene on Silica

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Junming; Psciuk, Brian T.; Chase, Hilary M.; Rudshteyn, Benjamin; Upshur, Mary Alice; Fu, Li; Thomson, Regan J.; Wang, Hong-Fei; Geiger, Franz M.; Batista, Victor S.

    2016-06-16

    A rotationally fluid state of α-pinene at fused silica/vapor interfaces is revealed by computational and experimental vibrational sum frequency generation (SFG) studies. We report the first assignment of the vibrational modes in the notoriously congested C-H stretching region of α-pinene and identify its bridge methylene group on the four-membered ring ("βCH2") as the origin of its dominant spectral feature. We find that the spectra are perfused with Fermi resonances that need to be accounted for explicitly in the computation of vibrational spectra of strained hydrocarbons such α-pinene. The preferred orientations of α-pinene are consistent with optimization of van der Waals contacts with the silica surface that results in a bimodal distribution of highly fluxional orientations in which the βCH2 group points "towards" or "away from” the surface. The reported findings are particularly relevant to the exposure of α-pinene to primary oxidants in heterogeneous catalytic pathways that exploit α-pinene as a sustainable feedstock for fine chemicals and polymers.

  9. Rotation operator approach for the dynamics of non-dissipative multi-state Landau-Zener problems: Exact solutions

    Science.gov (United States)

    Ateuafack, M. E.; Diffo, J. T.; Fai, L. C.; Jipdi, M. N.

    2017-01-01

    The paper investigates exact time-dependent analytical solutions of the Landau-Zener (LZ) transitions for spin one-half subjected to classical noise field using rotation operator approach introduced by Zhou and co-authors. The particular case of the LZ model subjected to colored noise field is studied and extended to arbitrary spin magnitude. Transition probabilities are derived regardless of the initial configuration of the system and are found to be functions of the sort for Stokes constant. It is observed that the latter may be completely evaluated provided we have knowledge of the phase difference between noise in x - and y - directions. Transition probabilities are found to depend not only on the LZ parameter and noise frequency, but also on the states involved in the study. In particular, the coherence of the system is sustained for an exceedingly long time when many levels are considered in an atom and if in addition, the LZ parameter tends to unity and the noise' frequency is low.

  10. Bifurcations of rotating waves in rotating spherical shell convection.

    Science.gov (United States)

    Feudel, F; Tuckerman, L S; Gellert, M; Seehafer, N

    2015-11-01

    The dynamics and bifurcations of convective waves in rotating and buoyancy-driven spherical Rayleigh-Bénard convection are investigated numerically. The solution branches that arise as rotating waves (RWs) are traced by means of path-following methods, by varying the Rayleigh number as a control parameter for different rotation rates. The dependence of the azimuthal drift frequency of the RWs on the Ekman and Rayleigh numbers is determined and discussed. The influence of the rotation rate on the generation and stability of secondary branches is demonstrated. Multistability is typical in the parameter range considered.

  11. Activation of Visuomotor Systems during Visually Guided Movements: A Functional MRI Study

    Science.gov (United States)

    Ellermann, Jutta M.; Siegal, Joel D.; Strupp, John P.; Ebner, Timothy J.; Ugurbil, Kâmil

    1998-04-01

    The dorsal stream is a dominant visuomotor pathway that connects the striate and extrastriate cortices to posterior parietal areas. In turn, the posterior parietal areas send projections to the frontal primary motor and premotor areas. This cortical pathway is hypothesized to be involved in the transformation of a visual input into the appropriate motor output. In this study we used functional magnetic resonance imaging (fMRI) of the entire brain to determine the patterns of activation that occurred while subjects performed a visually guided motor task. In nine human subjects, fMRI data were acquired on a 4-T whole-body MR system equipped with a head gradient coil and a birdcage RF coil using aT*2-weighted EPI sequence. Functional activation was determined for three different tasks: (1) a visuomotor task consisting of moving a cursor on a screen with a joystick in relation to various targets, (2) a hand movement task consisting of moving the joystick without visual input, and (3) a eye movement task consisting of moving the eyes alone without visual input. Blood oxygenation level-dependent (BOLD) contrast-based activation maps of each subject were generated using period cross-correlation statistics. Subsequently, each subject's brain was normalized to Talairach coordinates, and the individual maps were compared on a pixel by pixel basis. Significantly activated pixels common to at least four out of six subjects were retained to construct the final functional image. The pattern of activation during visually guided movements was consistent with the flow of information from striate and extrastriate visual areas, to the posterior parietal complex, and then to frontal motor areas. The extensive activation of this network and the reproducibility among subjects is consistent with a role for the dorsal stream in transforming visual information into motor behavior. Also extensively activated were the medial and lateral cerebellar structures, implicating the cortico

  12. Visuomotor correction is a robust contributor to force variability during index finger abduction by older adults

    Directory of Open Access Journals (Sweden)

    Brian L Tracy

    2015-12-01

    Full Text Available We examined aging-related differences in the contribution of visuomotor correction to force fluctuations during index finger abduction via the analysis of two datasets from similar subjects. Study 1 Young (N= 27, 23+/-8 yrs and older adults (N=14, 72+/- 9 yrs underwent assessment of maximum voluntary contraction force (MVC and force steadiness during constant-force (CF index finger abduction (2.5, 30, 65% MVC. For each trial, visual feedback of the force (VIS was provided for 8-10 s and removed for 8-10s (NOVIS. Visual gain of the force feedback at 2.5% MVC was high; 12- and 26-fold greater than the 30% and 65% MVC targets. Mean force, standard deviation (SD of force, and coefficient of variation (CV of force was calculated for detrended (<0.5Hz drift removed VIS and NOVIS data segments. Study 2 A similar group of 14 older adults performed discrete, randomly-ordered VIS or NOVIS trials at low target forces (1-3% MVC and high visual gain. Study 1 For young adults the CV of force was similar between VIS and NOVIS for the 2.5% (4.8 vs. 4.3%, 30% (3.2 vs. 3.2% and 65% (3.5 vs. 4.2% target forces. In contrast, for older adults the CV of force was greater for VIS than NOVIS for 2.5% MVC (6.6 vs. 4.2%, P<0.001, but not for the 30% (2.4 vs. 2.4% and 65% (3.1 vs. 3.3% target forces. At 2.5% MVC, the increase in CV of force for VIS compared with NOVIS was significantly greater (age x visual condition P=0.008 for older than young adults. Study 2 Similarly, for older adults performing discrete, randomly ordered trials the CV of force was greater for VIS than NOVIS (6.04 vs. 3.81%, P=0.01. When visual force feedback was a dominant source of information at low forces, normalized force variability was ~58% greater for older adults, but only 11% greater for young adults. The significant effect of visual feedback for older adults was not dependent on the order of presentation of visual conditions. The results indicate that impaired processing of visuomotor

  13. Dual beam Doppler FD-OCT system with integrated Dynamic Vessel Analyzer and rotatable beams to measure total retinal blood flow

    Science.gov (United States)

    Doblhoff-Dier, Veronika; Werkmeister, René M.; Gröschl, Martin; Schmetterer, Leopold

    2014-03-01

    We present a method capable of measuring the total retinal blood flow in arteries and veins based on dual beam Fourierdomain Doppler optical coherence tomography (OCT) in combination with a fundus camera based Dynamic Vessel Analyzer. Incorporating a Dynamic vessel analyzer into the system not only gives a live image of the fundus - it also allows determining the vessels' diameter precisely during the OCT measurement, which is necessary for the determination of the blood flow. While dual beam systems with fixed detection plane allow only vessels with certain orientations to be measured, the detection plane of our system can be rotated by 90°. This ensures that the blood's velocity can be measured in all vessels around the optic nerve head. The results of the total blood flow measurements are in the same range as previously published data. Additionally, the high degree of conformity between the measured venous and arterial flow corroborated the system's validity. For larger vessels, the logarithmic values of vessel diameter and blood flow were found to be related linearly with a regression coefficient of around 3, which is in accordance with Murray's law. For smaller vessels (diameter below 60 μm), the values diverge from the linear dependence. The high sensitivity and the good agreement with published data suggest a high potential for examining the retinal blood flow in patients with ocular diseases.

  14. Influence of Concentration and Temperature on Tunneling and Rotational Dynamics of Ammonium in $Rb_{1-x}(NH_{4})_{x}$ Mixed Crystals

    CERN Document Server

    Natkaniec, I; Martínez-Sarrion, M L; Mestres, L; Herraiz, M; Smirnov, L S; Shuvalov, L A

    2001-01-01

    The Rb_{1-x}(NH_{4})_{x} mixed crystals are studied by inelastic incoherent neutron scattering using time-of-flight spectrometers in the concentration region of the x-T phase diagram 0.01\\lq x \\lq 0.66 at 5\\lq T \\lq 150 K, where dynamic and static orientational disorder phases are generally found. It is shown that at 5 K rotational tunneling levels for ammonium concentrations x=0.01,0.02 and 0.06 are similar. Additional tunneling levels are observed for x=0.16 which can be explained as the result of T-states splitting for annount of NH_{4}-NH_{4} interaction. Tunneling levels are not observed for 0.40 as the result of forming orientational glass state. The elastic incoherent structure factors for concentrations 0.01\\lq x \\lq 0.16 (dynamic orientational disordered \\alpha-phase), x=0.40 (orientational glass state) and 0.50\\lq x \\lq 0.66 (orientational ordered state) have different temperature dependences.

  15. The fluid dynamics of work transfer in the non-uniform viscous rotating flow within a Tesla disc turbomachine

    Science.gov (United States)

    Guha, Abhijit; Sengupta, Sayantan

    2014-03-01

    In this article, the fluid dynamics of work transfer within the narrow spacing (usually of the order of 100 μm) of multiple concentric discs of a Tesla disc turbomachine (turbine or compressor) has been analysed theoretically and computationally. Both the overall work transfer and its spatial development have been considered. It has been established that the work transfer mechanism in a Tesla disc turbomachine is very different from that in a conventional turbomachine, and the formulation of the Euler's work equation for the disc turbomachine contains several conceptual subtleties because of the existence of complex, three dimensional, non-uniform, viscous flow features. A work equivalence principle has been enunciated, which establishes the equality between the magnitudes of work transfer determined rigorously from two different approaches—one based on the shear stress acting on the disc surfaces and the other based on the change in angular momentum of the fluid. Care is needed in identifying the shear stress components that are responsible for the generation or absorption of useful power. It is shown from the Reynolds transport theorem that mass-flow-averaged tangential velocities (as opposed to the normally used area-averaged values) must be used in determining the change in angular momentum; the calculation has to be carefully formulated since both radial velocity (that determines throughput) and tangential velocity (that generates torque) depend strongly on the coordinate perpendicular to the disc surfaces. The principle of work transfer has been examined both in the absolute and relative frames of reference, revealing the subtle role played by Coriolis force. The concept of a new non-dimensional quantity called the torque potential fraction (Δ tilde H) is introduced. The value of Δ tilde H at any radial position increases with a decrease in inter-disc spacing. The computational fluid dynamic analysis shows that, for small value of inter-disc spacing and

  16. Relative equilibria of full dynamics of a rigid body with gravitational orbit-attitude coupling in a uniformly rotating second degree and order gravity field

    Science.gov (United States)

    Wang, Yue; Xu, Shijie

    2014-12-01

    The motion of a rigid body in a uniformly rotating second degree and order gravity field is a good model for the gravitationally coupled orbit-attitude motion of a spacecraft in the close proximity of an asteroid. The relative equilibria of this full dynamics model are investigated using geometric mechanics from a global point of view. Two types of relative equilibria are found based on the equilibrium conditions: one is the Lagrangian relative equilibria, at which the circular orbit of the rigid body is in the equatorial plane of the central body; the other is the non-Lagrangian relative equilibria, at which the circular orbit is parallel to but not in the equatorial plane of central body. The existences of the Lagrangian and non-Lagrangian relative equilibria are discussed numerically with respect to the parameters of the gravity field and the rigid body. The effect of the gravitational orbit-attitude coupling is especially assessed. The existence region of the Lagrangian relative equilibria is given on the plane of the system parameters. Numerical results suggest that the negative C 20 with a small absolute value and a negative C 22 with a large absolute value favor the existence of the non-Lagrangian relative equilibria. The effect of the gravitational orbit-attitude coupling of the rigid body on the existence of the non-Lagrangian relative equilibria can be positive or negative, which depends on the harmonics C 20 and C 22, and the angular velocity of the rotation of the gravity field.

  17. The Build-Up Course of Visuo-Motor and Audio-Motor Temporal Recalibration

    Directory of Open Access Journals (Sweden)

    Yoshimori Sugano

    2011-10-01

    Full Text Available The sensorimotor timing is recalibrated after a brief exposure to a delayed feedback of voluntary actions (temporal recalibration effect: TRE (Heron et al., 2009; Stetson et al., 2006; Sugano et al., 2010. We introduce a new paradigm, namely ‘synchronous tapping’ (ST which allows us to investigate how the TRE builds up during adaptation. In each experimental trial, participants were repeatedly exposed to a constant lag (∼150 ms between their voluntary action (pressing a mouse and a feedback stimulus (a visual flash / an auditory click 10 times. Immediately after that, they performed a ST task with the same stimulus as a pace signal (7 flashes / clicks. A subjective ‘no-delay condition’ (∼50 ms served as control. The TRE manifested itself as a change in the tap-stimulus asynchrony that compensated the exposed lag (eg, after lag adaptation, the tap preceded the stimulus more than in control and built up quickly (∼3–6 trials, ∼23–45 sec in both the visuo- and audio-motor domain. The audio-motor TRE was bigger and built-up faster than the visuo-motor one. To conclude, the TRE is comparable between visuo- and audio-motor domain, though they are slightly different in size and build-up rate.

  18. White matter fiber degradation attenuates hemispheric asymmetry when integrating visuomotor information.

    Science.gov (United States)

    Schulte, Tilman; Müller-Oehring, Eva M; Rohlfing, Torsten; Pfefferbaum, Adolf; Sullivan, Edith V

    2010-09-01

    Degradation of white matter fibers can affect the transmission of signals in brain circuits that normally enable integration of highly lateralized visual and motor processes. Here, we used diffusion tensor imaging tractography in combination with functional magnetic resonance imaging to examine the specific contributions of interhemispheric and intrahemispheric white matter fibers to functional measures of hemispheric transfer and parallel information processing using bilateral and unilateral left and right visual field stimulation in normal and compromised systems. In healthy adults, a greater degree of bilateral processing advantage with the left (nondominant) hand correlated with higher integrity of callosal fibers connecting occipital cortices, whereas less unilateral processing advantage with the right hand correlated with higher integrity of left-hemispheric posterior cingulate fibers. In contrast, alcoholics who have compromised callosal integrity showed less bilateral processing advantage than controls when responding with the left hand and greater unilateral processing advantage when responding with the right hand. We also found degraded left posterior cingulate and posterior callosal fibers in chronic alcoholics, which is consistent with functional imaging results of less left posterior cingulate and extrastriate cortex activation in alcoholics than controls when processing bilateral compared with unilateral visual field stimulation. Together, our results demonstrated that interhemispheric and intrahemispheric white matter fiber pathways mediate visuomotor integration asymmetrically and that subtle white matter fiber degradation in alcoholism attenuated the normal pattern of hemispheric asymmetry, which may have ramifications for the efficiency of visual information processing and fast response execution.

  19. Videogame training strategy-induced change in brain function during a complex visuomotor task.

    Science.gov (United States)

    Lee, Hyunkyu; Voss, Michelle W; Prakash, Ruchika Shaurya; Boot, Walter R; Vo, Loan T K; Basak, Chandramallika; Vanpatter, Matt; Gratton, Gabriele; Fabiani, Monica; Kramer, Arthur F

    2012-07-01

    Although changes in brain function induced by cognitive training have been examined, functional plasticity associated with specific training strategies is still relatively unexplored. In this study, we examined changes in brain function during a complex visuomotor task following training using the Space Fortress video game. To assess brain function, participants completed functional magnetic resonance imaging (fMRI) before and after 30 h of training with one of two training regimens: Hybrid Variable-Priority Training (HVT), with a focus on improving specific skills and managing task priority, or Full Emphasis Training (FET), in which participants simply practiced the game to obtain the highest overall score. Control participants received only 6 h of FET. Compared to FET, HVT learners reached higher performance on the game and showed less brain activation in areas related to visuo-spatial attention and goal-directed movement after training. Compared to the control group, HVT exhibited less brain activation in right dorsolateral prefrontal cortex (DLPFC), coupled with greater performance improvement. Region-of-interest analysis revealed that the reduction in brain activation was correlated with improved performance on the task. This study sheds light on the neurobiological mechanisms of improved learning from directed training (HVT) over non-directed training (FET), which is related to visuo-spatial attention and goal-directed motor planning, while separating the practice-based benefit, which is related to executive control and rule management.

  20. Rapid online correction is selectively suppressed during movement with a visuomotor transformation.

    Science.gov (United States)

    Gritsenko, V; Kalaska, J F

    2010-12-01

    Reaching movements to visual targets are under fast feedback control, which can rapidly correct an ongoing movement for errors. This study investigates how this online correction is affected by the application of a new visuomotor transformation. Thirty-two subjects made planar pointing movements to visual targets. Vision of the arm was prevented, and hand position was represented by a cursor displayed in the movement plane. In some trials, the target abruptly changed location at the onset of arm movement, which required a rapid correction of movement direction. After performing baseline trials, some subjects were required to adapt to a mirror-image transformation that inverted the visual feedback of their hand position across the body midline, whereas others were not familiarized with the transformation. Afterward, subjects' online correction was tested with target jumps in the presence of the mirror transformation. Results show that after short-term motor adaptation to the mirror transformation there was a selective suppression of the rapid non-mirror correction in the direction of visual target displacement but no mirror reversal. The suppression occurred within the first few trials after the introduction of the mirror transformation, and it was strongest for the movements in which the transformation caused the largest dissociation between the target location and hand movement. Finally, whether or not the short-latency non-mirror correction was suppressed in a given trial, the mirror correction occurred at the same latency as the onset time of voluntary correction in subjects who had not experienced the mirror transformation.

  1. Classifying visuomotor workload in a driving simulator using subject specific spatial brain patterns.

    Directory of Open Access Journals (Sweden)

    Chris eDijksterhuis

    2013-08-01

    Full Text Available A passive Brain Computer Interface (BCI is a system that responds to the spontaneously produced brain activity of its user and could be used to develop interactive task support. A human-machine system that could benefit from brain-based task support is the driver-car interaction system. To investigate the feasibility of such a system to detect changes in visuomotor workload, 34 drivers were exposed to several levels of driving demand in a driving simulator. Driving demand was manipulated by varying driving speed and by asking the drivers to comply to individually set lane keeping performance targets. Differences in the individual driver’s workload levels were classified by applying the Common Spatial Pattern (CSP and Fisher’s linear discriminant analysis to frequency filtered electroencephalogram (EEG data during an off line classification study. Several frequency ranges, EEG cap configurations, and condition pairs were explored. It was found that classifications were most accurate when based on high frequencies, larger electrode sets, and the frontal electrodes. Depending on these factors, classification accuracies across participants reached about 95% on average. The association between high accuracies and high frequencies suggests that part of the underlying information did not originate directly from neuronal activity. Nonetheless, average classification accuracies up to 75%-80% were obtained from the lower EEG ranges that are likely to reflect neuronal activity. For a system designer, this implies that a passive BCI system may use several frequency ranges for workload classifications.

  2. Rotational superradiance in fluid laboratories

    CERN Document Server

    Cardoso, Vitor; Richartz, Mauricio; Weinfurtner, Silke

    2016-01-01

    Rotational superradiance has been predicted theoretically decades ago, and is the chief responsible for a number of important effects and phenomenology in black hole physics. However, rotational superradiance has never been observed experimentally. Here, with the aim of probing superradiance in the lab, we investigate the behaviour of sound and surface waves in fluids resting in a circular basin at the center of which a rotating cylinder is placed. We show that with a suitable choice for the material of the cylinder, surface and sound waves are amplified. By confining the superradiant modes near the rotating cylinder, an instability sets in. Our findings are experimentally testable in existing fluid laboratories and hence offer experimental exploration and comparison of dynamical instabilities arising from rapidly rotating boundary layers in astrophysical as well as in fluid dynamical systems.

  3. 5D quantum dynamics of the H{sub 2}@SWNT system: Quantitative study of the rotational-translational coupling

    Energy Technology Data Exchange (ETDEWEB)

    Mondelo-Martell, M.; Huarte-Larrañaga, F., E-mail: fermin.huarte@ub.edu [Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB),Universitat de Barcelona, C/ Martí i Franqués 1, 08028 Barcelona (Spain)

    2015-02-28

    The dynamics of the dihydrogen molecule when confined in carbon nanotubes with different chiralities and diameters are studied by using a 5 dimensional model considering the most relevant degrees of freedom of the system. The nuclear eigenstates are calculated for an (8,0) and a (5,0) carbon nanotubes by the State-Average Multiconfigurational Time-dependent Hartree, and then studied using qualitative tools (mapping of the total wave functions onto given subspaces) and more rigorous analysis (different kinds of overlaps with reference functions). The qualitative analysis is seen to fail due to a strong coupling between the internal and translational degrees of freedom. Using more accurate tools allows us to gain a deeper insight into the behaviour of confined species.

  4. 5D quantum dynamics of the H2@SWNT system: quantitative study of the rotational-translational coupling.

    Science.gov (United States)

    Mondelo-Martell, M; Huarte-Larrañaga, F

    2015-02-28

    The dynamics of the dihydrogen molecule when confined in carbon nanotubes with different chiralities and diameters are studied by using a 5 dimensional model considering the most relevant degrees of freedom of the system. The nuclear eigenstates are calculated for an (8,0) and a (5,0) carbon nanotubes by the State-Average Multiconfigurational Time-dependent Hartree, and then studied using qualitative tools (mapping of the total wave functions onto given subspaces) and more rigorous analysis (different kinds of overlaps with reference functions). The qualitative analysis is seen to fail due to a strong coupling between the internal and translational degrees of freedom. Using more accurate tools allows us to gain a deeper insight into the behaviour of confined species.

  5. Optimisation of NMR dynamic models I. Minimisation algorithms and their performance within the model-free and Brownian rotational diffusion spaces.

    Science.gov (United States)

    d'Auvergne, Edward J; Gooley, Paul R

    2008-02-01

    The key to obtaining the model-free description of the dynamics of a macromolecule is the optimisation of the model-free and Brownian rotational diffusion parameters using the collected R (1), R (2) and steady-state NOE relaxation data. The problem of optimising the chi-squared value is often assumed to be trivial, however, the long chain of dependencies required for its calculation complicates the model-free chi-squared space. Convolutions are induced by the Lorentzian form of the spectral density functions, the linear recombinations of certain spectral density values to obtain the relaxation rates, the calculation of the NOE using the ratio of two of these rates, and finally the quadratic form of the chi-squared equation itself. Two major topological features of the model-free space complicate optimisation. The first is a long, shallow valley which commences at infinite correlation times and gradually approaches the minimum. The most severe convolution occurs for motions on two timescales in which the minimum is often located at the end of a long, deep, curved tunnel or multidimensional valley through the space. A large number of optimisation algorithms will be investigated and their performance compared to determine which techniques are suitable for use in model-free analysis. Local optimisation algorithms will be shown to be sufficient for minimisation not only within the model-free space but also for the minimisation of the Brownian rotational diffusion tensor. In addition the performance of the programs Modelfree and Dasha are investigated. A number of model-free optimisation failures were identified: the inability to slide along the limits, the singular matrix failure of the Levenberg-Marquardt minimisation algorithm, the low precision of both programs, and a bug in Modelfree. Significantly, the singular matrix failure of the Levenberg-Marquardt algorithm occurs when internal correlation times are undefined and is greatly amplified in model-free analysis by

  6. Dynamical localization in chaotic systems: spectral statistics and localization measure in the kicked rotator as a paradigm for time-dependent and time-independent systems.

    Science.gov (United States)

    Manos, Thanos; Robnik, Marko

    2013-06-01

    We study the kicked rotator in the classically fully chaotic regime using Izrailev's N-dimensional model for various N≤4000, which in the limit N→∞ tends to the quantized kicked rotator. We do treat not only the case K=5, as studied previously, but also many different values of the classical kick parameter 5≤K≤35 and many different values of the quantum parameter kε[5,60]. We describe the features of dynamical localization of chaotic eigenstates as a paradigm for other both time-periodic and time-independent (autonomous) fully chaotic or/and mixed-type Hamilton systems. We generalize the scaling variable Λ=l(∞)/N to the case of anomalous diffusion in the classical phase space by deriving the localization length l(∞) for the case of generalized classical diffusion. We greatly improve the accuracy and statistical significance of the numerical calculations, giving rise to the following conclusions: (1) The level-spacing distribution of the eigenphases (or quasienergies) is very well described by the Brody distribution, systematically better than by other proposed models, for various Brody exponents β(BR). (2) We study the eigenfunctions of the Floquet operator and characterize their localization properties using the information entropy measure, which after normalization is given by β(loc) in the interval [0,1]. The level repulsion parameters β(BR) and β(loc) are almost linearly related, close to the identity line. (3) We show the existence of a scaling law between β(loc) and the relative localization length Λ, now including the regimes of anomalous diffusion. The above findings are important also for chaotic eigenstates in time-independent systems [Batistić and Robnik, J. Phys. A: Math. Gen. 43, 215101 (2010); arXiv:1302.7174 (2013)], where the Brody distribution is confirmed to a very high degree of precision for dynamically localized chaotic eigenstates, even in the mixed-type systems (after separation of regular and chaotic eigenstates).

  7. 带旋转修正的弹簧-TFI混合动网格方法%Spring-TFI Hybrid Dynamic Mesh Method with Rotation Correction

    Institute of Scientific and Technical Information of China (English)

    张兵; 韩景龙

    2011-01-01

    Problems of orthogonal properties become more serious when the traditional transfinite interpolation (TFI) dynamic mesh method is employed for large deformations. Based on an analysis of the geometric relationship and interpolation features, an improvement for the present TFI method is proposed with a rotation correction. A new spring-TFI hybrid dynamic mesh method is developed for a structured mesh. First, each block of the computation domain is divided into several sub-blocks. Then, a spring network which connects the corners of all sub-blocks is established to smooth the mesh by means of spring analysis. Finally, a modified TFI method is used for calculating the inner deformations of the sub-blocks. Computational results of typical two and three dimensional viscous grids indicate that good orthogonal and smoothing properties can be achieved by rotation correction for large mesh deformations. In addition, the computational efficiency is slightly decreased than the traditional TFI method, but improved by 1 or 2 orders of magnitude when compared with the spring analogy method.%网格存在大变形时,传统的超限插值(TFI)动网格方法易于引起网格正交性问题.依据几何关系并考虑其插值特点,提出了一种带旋转修正的TFI动网格方法.对结构网格块进行分块,在子块角点间建立弹簧元,并基于弹簧类比法计算角点位移;子网格内部结点位移采用修正后的TFI动网格方法进行计算,从而形成具有弹簧-TFI混合特征的动网格新方法.以典型二维及三维黏性网格为例进行方法的有效性研究.结果表明,在显著大变形情况下,引入旋转修正得到了正交性和光顺性良好的变形网格.另外,该方法的计算效率较传统TFI动网格方法有所降低,但相比弹簧方法提高1到2个量级.

  8. Jupiter and Saturn Rotation Periods

    CERN Document Server

    Helled, Ravit; Anderson, John D

    2009-01-01

    Anderson & Schubert (2007, Science,317,1384) proposed that Saturn's rotation period can be ascertained by minimizing the dynamic heights of the 100 mbar isosurface with respect to the geoid; they derived a rotation period of 10h 32m 35s. We investigate the same approach for Jupiter to see if the Jovian rotation period is predicted by minimizing the dynamical heights of its isobaric (1 bar pressure level) surface using zonal wind data. A rotation period of 9h 54m 29s is found. Further, we investigate the minimization method by fitting Pioneer and Voyager occultation radii for both Jupiter and Saturn. Rotation periods of 9h 55m 30s and 10h 32m 35s are found to minimize the dynamical heights for Jupiter and Saturn, respectively. Though there is no dynamical principle requiring the minimization of the dynamical heights of an isobaric surface, the successful application of the method to Jupiter lends support to its relevance for Saturn. We derive Jupiter and Saturn rotation periods using equilibrium theory in ...

  9. Evaluation of Central Corneal Thickness Using Corneal Dynamic Scheimpflug Analyzer Corvis ST and Comparison with Pentacam Rotating Scheimpflug System and Ultrasound Pachymetry in Normal Eyes

    Science.gov (United States)

    Yu, Ayong; Zhao, Weiqi; Savini, Giacomo; Huang, Zixu; Bao, Fangjun; Lu, Weicong; Wang, Qinmei; Huang, Jinhai

    2015-01-01

    Purpose. To assess the repeatability and reproducibility of central corneal thickness (CCT) measurements by corneal dynamic Scheimpflug analyzer Corvis ST in normal eyes and compare the agreement with Pentacam rotating Scheimpflug System and ultrasound pachymetry. Methods. 84 right eyes underwent Corvis ST measurements performed by two operators. The test-retest repeatability (TRT), within-subject coefficient of variation (CoV), and intraclass correlation coefficient (ICC) were used to evaluate the intraoperator repeatability and interoperator reproducibility. CCT measurements also were obtained from Pentacam and ultrasound pachymetry by the first operator. The agreement between the three devices was evaluated with 95% limits of agreement (LoA) and Bland-Altman plots. Results. Corvis ST showed high repeatability as indicated by TRT ≤ 13.0 μm, CoV 0.97. The interoperator reproducibility was also excellent. The CoV was 0.97. Corvis ST showed significantly lower values than Pentacam and ultrasound pachymetry (P < 0.001). The 95% LoA between Corvis ST and Pentacam or ultrasound pachymetry were −15.8 to 9.5 μm and −27.9 to 12.3 μm, respectively. Conclusions. Corvis ST showed excellent repeatability and interoperator reproducibility of CCT measurements in normal eyes. Corvis ST is interchangeable with Pentacam but not with ultrasound pachymetry. PMID:26697213

  10. Evaluation of Central Corneal Thickness Using Corneal Dynamic Scheimpflug Analyzer Corvis ST and Comparison with Pentacam Rotating Scheimpflug System and Ultrasound Pachymetry in Normal Eyes

    Directory of Open Access Journals (Sweden)

    Ayong Yu

    2015-01-01

    Full Text Available Purpose. To assess the repeatability and reproducibility of central corneal thickness (CCT measurements by corneal dynamic Scheimpflug analyzer Corvis ST in normal eyes and compare the agreement with Pentacam rotating Scheimpflug System and ultrasound pachymetry. Methods. 84 right eyes underwent Corvis ST measurements performed by two operators. The test-retest repeatability (TRT, within-subject coefficient of variation (CoV, and intraclass correlation coefficient (ICC were used to evaluate the intraoperator repeatability and interoperator reproducibility. CCT measurements also were obtained from Pentacam and ultrasound pachymetry by the first operator. The agreement between the three devices was evaluated with 95% limits of agreement (LoA and Bland-Altman plots. Results. Corvis ST showed high repeatability as indicated by TRT ≤ 13.0 μm, CoV 0.97. The interoperator reproducibility was also excellent. The CoV was 0.97. Corvis ST showed significantly lower values than Pentacam and ultrasound pachymetry (P<0.001. The 95% LoA between Corvis ST and Pentacam or ultrasound pachymetry were −15.8 to 9.5 μm and −27.9 to 12.3 μm, respectively. Conclusions. Corvis ST showed excellent repeatability and interoperator reproducibility of CCT measurements in normal eyes. Corvis ST is interchangeable with Pentacam but not with ultrasound pachymetry.

  11. Different Evolutionary Origins for the Reach and the Grasp: An Explanation for Dual Visuomotor Channels in Primate Parietofrontal Cortex

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    Jenni M Karl

    2013-12-01

    Full Text Available The Dual Visuomotor Channel Theory proposes that manual prehension consists of two temporally integrated movements, each subserved by distinct visuomotor pathways in occipitoparietofrontal cortex. The Reach is mediated by a dorsomedial pathway and transports the hand in relation to the target’s extrinsic properties (i.e., location and orientation. The Grasp is mediated by a dorsolateral pathway and opens, preshapes, and closes the hand in relation to the target’s intrinsic properties (i.e., size and shape. Here, neuropsychological, developmental, and comparative evidence is reviewed to show that the Reach and the Grasp have different evolutionary origins. First, the removal or degradation of vision causes prehension to decompose into its constituent Reach and Grasp components, which are then executed in sequence or isolation. Similar decomposition occurs in optic ataxic patients following cortical injury to the Reach and Grasp pathways and after corticospinal tract lesions in non-human primates. Second, early nonvisual PreReach and PreGrasp movements develop into mature Reach and Grasp movements but are only integrated under visual control after a prolonged developmental period. Third, comparative studies reveal many similarities between stepping movements and the Reach and between food handling movements and the Grasp, suggesting that the Reach and Grasp are derived from different evolutionary antecedents. The evidence is discussed in relation to the ideas that dual visuomotor channels in primate parietofrontal cortex emerged as a result of distinct evolutionary origins for the Reach and Grasp; that foveated vision in primates serves to integrate the Reach and Grasp into a single prehensile act; and, that flexible recombination of discrete Reach and Grasp movements under various forms of sensory and cognitive control can produce adaptive behavior.

  12. Deviant smooth pursuit in preschool children exposed prenatally to methadone or buprenorphine and tobacco affects integrative visuomotor capabilities.

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    Melinder, Annika; Konijnenberg, Carolien; Sarfi, Monica

    2013-12-01

    Although an increasing number of children are born to mothers in opioid maintenance therapy (OMT), little is known about the long-term effects of these opioids. Previous studies suggest an association between prenatal OMT exposure and difficulties in eye movement control. Also, the effects of tobacco smoking on eye movements have been reported. The present study examined the influence of eye movements, i.e. smooth pursuit, on visuomotor capabilities in children of smoking mothers in OMT. The study comprised a 2 (OMT versus contrast group) × 2 (slow versus fast smooth pursuit) between-subject factorial design. The cognitive developmental research unit at the University of Oslo, Norway. Participants were 26 4-year-old children of tobacco-smoking women in OMT and 23 non-exposed 4-year-old children, with non-smoking mothers, matched by gender and age. Eye movements and smooth pursuit were recorded using a Tobii 1750 eyetracker. Visuomotor functions were examined by Bender test. The OMT group tracked slowly moving objects with smooth pursuit in a similar manner to their non-exposed peers. When fast smooth pursuit was measured, the OMT group of children tracked the object more slowly than the contrast group, P = 0.02, ηp(2) = 0.11. A regression analysis showed that fast smooth pursuit predicted children's performance on a visuomotor task, R(2) = 0.37. Impaired eye-tracking skills in 4-year-old children exposed to methadone or buprenorphine and tobacco prenatally could inhibit the development of some cognitive functions in later life. ©2013 The Authors. Addiction published by John Wiley & Sons Ltd on behalf of The Society for the Study of Addiction.

  13. The dynamic behavior of bacterial macrofibers growing with one end prevented from rotating: variation in shaft rotation along the fiber's length, and supercoil movement on a solid surface toward the constrained end

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    Chen Liling

    2003-08-01

    Full Text Available Abstract Background Bacterial macrofibers twist as they grow, writhe, supercoil and wind up into plectonemic structures (helical forms the individual filaments of which cannot be taken apart without unwinding that eventually carry loops at both of their ends. Terminal loops rotate about the axis of a fiber's shaft in contrary directions at increasing rate as the shaft elongates. Theory suggests that rotation rates should vary linearly along the length of a fiber ranging from maxima at the loop ends to zero at an intermediate point. Blocking rotation at one end of a fiber should lead to a single gradient: zero at the blocked end to maximum at the free end. We tested this conclusion by measuring directly the rotation at various distances along fiber length from the blocked end. The movement of supercoils over a solid surface was also measured in tethered macrofibers. Results Macrofibers that hung down from a floating wire inserted through a terminal loop grew vertically and produced small plectonemic structures by supercoiling along their length. Using these as markers for shaft rotation we observed a uniform gradient of initial rotation rates with slopes of 25.6°/min. mm. and 36.2°/min. mm. in two different fibers. Measurements of the distal tip rotation in a third fiber as a function of length showed increases proportional to increases in length with constant of proportionality 79.2 rad/mm. Another fiber tethered to the floor grew horizontally with a length-doubling time of 74 min, made contact periodically with the floor and supercoiled repeatedly. The supercoils moved over the floor toward the tether at approximately 0.06 mm/min, 4 times faster than the fiber growth rate. Over a period of 800 minutes the fiber grew to 23 mm in length and was entirely retracted back to the tether by a process involving 29 supercoils. Conclusions The rate at which growing bacterial macrofibers rotated about the axis of the fiber shaft measured at various

  14. Prisms for pain. Can visuo-motor rehabilitation strategies alleviate chronic pain?

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    Torta, DM; Legrain, V; Rossetti, Y; Mouraux, A

    2017-01-01

    Background and aims Prism adaptation (PA) is a non-invasive procedure in which participants perform a visuo-motor pointing task while wearing prism goggles inducing a lateral displacement of the visual field and a mismatch between the seen and felt position of the pointing hand. PA is thought to induce a reorganization of sensorimotor coordination, and has been used successfully to rehabilitate neglect following right-hemisphere lesions. Because studies have shown that complex regional pain syndrome (CRPS) is associated with neglect-like symptoms, it was proposed that PA could be used to alleviate pain in these patients. Database A search for peer-reviewed articles on neglect-like symptoms in CRPS and on the use of prisms in CRPS was conducted using the PubMed database. Results There is still no agreement as to whether CRPS patients really present neglect symptoms and, if they do, what it is that they neglect. Furthermore, there is insufficient data to determine whether PA exerts an effect on CRPS symptoms. Finally, it remains unknown whether neglect can be observed in other types of lateralized pain, or whether PA could be useful for these patients. Conclusion By highlighting open issues, our review provides guidelines for future studies on the use of prisms in pain. The assessment of neglect in patients with CRPS as well as other types of lateralized chronic pain should be characterized using a combination of neuropsychological methods assessing the multiple aspects of neglect in a more refined manner. In addition, further studies should investigate the mechanisms through which PA may modulate pain. PMID:26095341

  15. Interhemispheric claustral circuits coordinate somatomotor and visuomotor cortical areas that regulate exploratory behaviors

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    Jared Brent Smith

    2014-05-01

    Full Text Available The claustrum has a role in the interhemispheric transfer of certain types of sensorimotor information. Whereas the whisker region in rat motor (M1 cortex sends dense projections to the contralateral claustrum, the M1 forelimb representation does not. The claustrum sends strong ipsilateral projections to the whisker regions in M1 and somatosensory (S1 cortex, but its projections to the forelimb cortical areas are weak. These distinctions suggest that one function of the M1 projections to the contralateral claustrum is to coordinate the cortical areas that regulate peripheral sensor movements during behaviors that depend on bilateral sensory acquisition. If this hypothesis is true, then similar interhemispheric circuits should interconnect the frontal eye fields (FEF with the contralateral claustrum and its network of projections to vision-related cortical areas. To test this hypothesis, anterograde and retrograde tracers were placed in physiologically-defined parts of the FEF and primary visual cortex (V1 in rats. We observed dense FEF projections to the contralateral claustrum that terminated in the midst of claustral neurons that project to both FEF and V1. While the FEF inputs to the claustrum come predominantly from the contralateral hemisphere, the claustral projections to FEF and V1 are primarily ipsilateral. Detailed comparison of the present results with our previous studies on somatomotor claustral circuitry revealed a well-defined functional topography in which the ventral claustrum is connected with visuomotor cortical areas and the dorsal regions are connected with somatomotor areas. These results suggest that subregions within the claustrum play a critical role in coordinating the cortical areas that regulate the acquisition of modality-specific sensory information during exploration and other behaviors that require sensory attention.

  16. View-Invariant Visuomotor Processing in Computational Mirror Neuron System for Humanoid.

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    Dawood, Farhan; Loo, Chu Kiong

    2016-01-01

    Mirror neurons are visuo-motor neurons found in primates and thought to be significant for imitation learning. The proposition that mirror neurons result from associative learning while the neonate observes his own actions has received noteworthy empirical support. Self-exploration is regarded as a procedure by which infants become perceptually observant to their own body and engage in a perceptual communication with themselves. We assume that crude sense of self is the prerequisite for social interaction. However, the contribution of mirror neurons in encoding the perspective from which the motor acts of others are seen have not been addressed in relation to humanoid robots. In this paper we present a computational model for development of mirror neuron system for humanoid based on the hypothesis that infants acquire MNS by sensorimotor associative learning through self-exploration capable of sustaining early imitation skills. The purpose of our proposed model is to take into account the view-dependency of neurons as a probable outcome of the associative connectivity between motor and visual information. In our experiment, a humanoid robot stands in front of a mirror (represented through self-image using camera) in order to obtain the associative relationship between his own motor generated actions and his own visual body-image. In the learning process the network first forms mapping from each motor representation onto visual representation from the self-exploratory perspective. Afterwards, the representation of the motor commands is learned to be associated with all possible visual perspectives. The complete architecture was evaluated by simulation experiments performed on DARwIn-OP humanoid robot.

  17. View-Invariant Visuomotor Processing in Computational Mirror Neuron System for Humanoid.

    Directory of Open Access Journals (Sweden)

    Farhan Dawood

    Full Text Available Mirror neurons are visuo-motor neurons found in primates and thought to be significant for imitation learning. The proposition that mirror neurons result from associative learning while the neonate observes his own actions has received noteworthy empirical support. Self-exploration is regarded as a procedure by which infants become perceptually observant to their own body and engage in a perceptual communication with themselves. We assume that crude sense of self is the prerequisite for social interaction. However, the contribution of mirror neurons in encoding the perspective from which the motor acts of others are seen have not been addressed in relation to humanoid robots. In this paper we present a computational model for development of mirror neuron system for humanoid based on the hypothesis that infants acquire MNS by sensorimotor associative learning through self-exploration capable of sustaining early imitation skills. The purpose of our proposed model is to take into account the view-dependency of neurons as a probable outcome of the associative connectivity between motor and visual information. In our experiment, a humanoid robot stands in front of a mirror (represented through self-image using camera in order to obtain the associative relationship between his own motor generated actions and his own visual body-image. In the learning process the network first forms mapping from each motor representation onto visual representation from the self-exploratory perspective. Afterwards, the representation of the motor commands is learned to be associated with all possible visual perspectives. The complete architecture was evaluated by simulation experiments performed on DARwIn-OP humanoid robot.

  18. Neural Predictors of Visuomotor Adaptation Rate and Multi-Day Savings

    Science.gov (United States)

    Cassady, Kaitlin; Ruitenberg, Marit; Koppelmans, Vincent; Reuter-Lorenz, Patricia; De Dios, Yiri; Gadd, Nichole; Wood, Scott; Riascos Castenada, Roy; Kofman, Igor; Bloomberg, Jacob; hide

    2017-01-01

    Recent studies of sensorimotor adaptation have found that individual differences in task-based functional brain activation are associated with the rate of adaptation and savings at subsequent sessions. However, few studies to date have investigated offline neural predictors of adaptation and multi-day savings. In the present study, we explore whether individual differences in the rate of visuomotor adaptation and multi-day savings are associated with differences in resting state functional connectivity and gray matter volume. Thirty-four participants performed a manual adaptation task during two separate test sessions, on average 9 days apart. We found that resting state functional connectivity strength between sensorimotor, anterior cingulate, and temporoparietal areas of the brain was a significant predictor of adaptation rate during the early, cognitive phase of practice. In contrast, default mode network functional connectivity strength was found to predict late adaptation rate and savings on day two, which suggests that these behaviors may rely on overlapping processes. We also found that gray matter volume in temporoparietal and occipital regions was a significant predictor of early learning, whereas gray matter volume in superior posterior regions of the cerebellum was a significant predictor of late adaptation. The results from this study suggest that offline neural predictors of early adaptation facilitate the cognitive mechanisms of sensorimotor adaptation, with support from by the involvement of temporoparietal and cingulate networks. In contrast, the neural predictors of late adaptation and savings, including the default mode network and the cerebellum, likely support the storage and modification of newly acquired sensorimotor representations. These findings provide novel insights into the neural processes associated with individual differences in sensorimotor adaptation.

  19. Daytime sleep has no effect on the time course of motor sequence and visuomotor adaptation learning.

    Science.gov (United States)

    Backhaus, Winifried; Braaß, Hanna; Renné, Thomas; Krüger, Christian; Gerloff, Christian; Hummel, Friedhelm C

    2016-05-01

    Sleep has previously been claimed to be essential for the continued learning processes of declarative information as well as procedural learning. This study was conducted to examine the importance of sleep, especially the effects of midday naps, on motor sequence and visuomotor adaptation learning. Thirty-five (27 females) healthy, young adults aged between 18 and 30years of age participated in the current study. Addressing potential differences in explicit sequence and motor adaptation learning participants were asked to learn both, a nine-element explicit sequence and a motor adaptation task, in a crossover fashion on two consecutive days. Both tasks were performed with their non-dominant left hand. Prior to learning, each participant was randomized to one of three interventions; (1) power nap: 10-20min sleep, (2) long nap: 50-80min sleep or (3) a 45-min wake-condition. Performance of the motor learning task took place prior to and after a midday rest period, as well as after a night of sleep. Both sleep conditions were dominated by Stage N2 sleep with embedded sleep spindles, which have been described to be associated with enhancement of motor performance. Significant performance changes were observed in both tasks across all interventions (sleep and wake) confirming that learning took place. In the present setup, the magnitude of motor learning was not sleep-dependent in young adults - no differences between the intervention groups (short nap, long nap, no nap) could be found. The effect of the following night of sleep was not influenced by the previous midday rest or sleep period. This finding may be related to the selectiveness of the human brain enhancing especially memory being thought of as important in the future. Previous findings on motor learning enhancing effects of sleep, especially of daytime sleep, are challenged.

  20. A contribution on the investigation of the dynamic behavior of rotating shafts with a Hybrid Magnetic Bearing Concept (HMBC) for blower application

    Energy Technology Data Exchange (ETDEWEB)

    Gronek, Martin, E-mail: MGronek@hs-zigr.d [HOCHSCHULE ZITTAU/GOERLITZ-University of Applied Sciences, Institute of Process Technology, Process Automation and Measuring Technology (IPM), Department Mechatronical Systems, Theodor-Koerner-Allee 16, 02763 Zittau (Germany); Rottenbach, Torsten; Worlitz, Frank [HOCHSCHULE ZITTAU/GOERLITZ-University of Applied Sciences, Institute of Process Technology, Process Automation and Measuring Technology (IPM), Department Mechatronical Systems, Theodor-Koerner-Allee 16, 02763 Zittau (Germany)

    2010-10-15

    Within a subproject of the RAPHAEL-Program, which was part of the 6th EURATOM Framework Program supervised by the European Commission, it was investigated whether the use of a Hybrid Magnetic Bearing Concept (HMBC) will be beneficial for a blower application. Within the RAPHAEL program, the subproject 'Component Development' is dealing with R and D of components of High Temperature Reactor Technology (HTR), where a major focus is on safety- and reliability-related issues. That implies special requirements for the support of high speed rotating shafts in HTR-Applications that only can be satisfied by using Active Magnetic Bearings (AMB). Regarding safety and competitiveness, AMBs are considered to be key components for the support of rotating HTR-components due to their technical features. AMBs are characterized by an electromagnetic actuator that is generating the bearing force depending on the clearance between stator and rotor, in which the rotor is levitated. Therefore an active control of the coil current is necessary. Furthermore, Touch Down Bearings (TDB) are needed to avoid damages in case of an emergency shut down or in case of energy supply losses. This contribution provides an internal insight on the advantages of a Hybrid Magnetic Bearing Concept that is characterized by a completely Active Magnetic Bearing-supported vertical arranged rotor and an additional permanent magnetic radial orientated bearing. One benefit of the HMBC is an additional radial guidance of the shaft that may reduce the loads while dropping into the Touch Down Bearings e.g. in case of energy supply losses of the AMBs. Reduced loads on the TDBs will increase their life cycle and the availability of the AMB supported component. The scope of this R and D-Project, which will be described more detailed in this contribution, includes: the analytical modeling and simulation of the dynamic behavior of the Hybrid Magnetic Bearing System; the modification of the completely AMB